University of Texas McDonald Observatory and Department of … · 2020. 1. 3. · University of...

637

University of TexasMcDonald Observatory and Department of Astronomy

Austin, Texas 78712

u

afoortauacuc

isu-leg

c

-.n

-

de

si

in-

s-

As-

r ink

fes-

ing

This report covers the period 1 September 1994 31 Aug1995.

1. ORGANIZATION, STAFF, AND ACTIVITIES

1.1 Description of Facilities

The astronomical components of the University of Texat Austin are the Department of Astronomy, the CenterAdvanced Studies in Astronomy, and McDonald Observatat Mount Locke. Faculty, research, and administrative soffices of all components are located on the campus in Atin. The Department of Astronomy operates a 23-cm refrtor and a 41-cm reflector on the Austin campus for instrtional, test, and research purposes.

McDonald Observatory is in West Texas, near Fort Davon Mount Locke and Mount Fowlkes. The primary instrments are 2.7-m, 2.1-m, 91-cm, and 76-cm reflecting tescopes and a 76-cm telescope dedicated to laser ranginthe moon and artificial satellites.

McDonald Observatory is also a partner in the CalteSubmillimeter Observatory on Mauna Kea, Hawaii.

1.2 Administration

William H. Jefferys is Chair of the Department of Astronomy, with EthanVishniac as Assistant Chair. Frank NBash is the Director of McDonald Observatory and the Ceter for Advanced Studies in Astronomy, Thomas G.BarnesIII is Associate Director, ChrisSnedenwas Associate Direc-tor for the Hobby-Eberly Telescope, and Phillip W.Kelton isAssistant Director. MarkAdams is the resident Superintendent.

Bill Block was Chair of the McDonald Observatory anDepartment of Astronomy Board of Visitors, with GeorgChristian Vice Chair and LucyAlexander Secretary.

Members of the Board of Visitors: LucyAlexander, MarkBivins, William Block, Malcolm Brachman, Wm. TerryBray, J.P.Bryan, Clifton Caldwell, GeorgeChristian , Jo-sephCialone, AnneDickson, MarshallDoke, GeorgeFin-ley, DavidGraeber, William Guest, PaulHobby, ElizabethHutchinson, KatherineJohnson, HerbertKelleher, GarlandLasater, ThomasLink , PaulMeek, ArthurMiller , BradfordMoody, Lillian Murray , JudyNewton, PikePowers, Will-iam Ratz, Carl Ryan, Marshall Steves, RobertStrauser,Curtis Vaughan, David Weeks, GeneWiggins, FrancisWright , and SamuelYanagisawa.

1.3 Teaching and Research Personnel

~In the lists that follow, asterisks denote Mount Locke redents.!

st

sryffs---

,

-to

h

-

-

Academic

Named Professors: Frank N. Bash ~Frank N. EdmondsRegents Professor in Astronomy!; Gerard H. de Vau-couleurs ~Jane and Roland Blumberg Professor EmeritusAstronomy!; David S.Evans ~Jack S. Josey Centennial Professor Emeritus in Astronomy!; Neal J.Evans II ~EdwardRandall, Jr. Centennial Professor!, William H. Jefferys ~Har-lan J. Smith Centennial Professor in Astronomy!; David L.Lambert ~Isabel McCutcheon Harte Centennial Chair in Atronomy!; R. EdwardNather ~Rex G. Baker, Jr. and Mc-Donald Observatory Centennial Research Professor intronomy!; Edward L.Robinson ~William B. Blakemore IIRegents Professor in Astronomy!; John M.Scalo ~Jack S.Josey Centennial Professor in Astronomy!; Gregory A.Shields~Jane and Roland Blumberg Centennial ProfessoAstronomy!; StevenWeinberg ~Regents Professor and JacS. Josey–Welch Foundation Chair in Science!; and J. CraigWheeler ~Samuel T. and Fern Yanagisawa Regents Prosorship in Astronomy!.

Professors: Michel Breger ~adjunct!, James N.Douglas,Roman Smoluchowski ~emeritus!, Paul Shapiro, ChrisSneden, Paul A. Vanden Bout ~adjunct!, EthanVishniac,DerekWills , and DonWinget.

Associate Professors: Harriet Dinerstein, Paul M.Har-vey, Dan Jaffe, JohnLacy, and R. RobertRobbins, Jr.As-sistant Professors: BeverleyWills .

Non-Academic

Senior Research Scientists: Thomas G.Barnes III, RobertG. Tull , Laurence M.Trafton .

Research Scientists: Edwin S.Barker , George F.Bene-dict, Anita L. Cochran, William D. Cochran, Artie P.Hatzes, Paul D.Hemenway, Gary Hill , Daniel F.Lester,FrankRay, Peter J.Shelus, VerneSmith, JocelynTomkin ,and Arthur L.Whipple.

Research Associates: Mark Cornell, Robert Duncan,Mary Kay Hemenway, Victor Krabbendam, AlexeiKhokhlov , Larry Long, Hugo Martel , Alvin L. Mitchell ,Phillip MacQueen, Ed Nelan, Darrell Story, and Er-HoZhang.

Postdoctoral Research Associates and Other VisitStaff: Eric Bakker, Beth Clark , Ramon Garcıa Lopez,Guillermo Gonzalez, Christopher Johns-Krull , IngerJo”rgensen, Doug Kelly , Soon-WookKim , JeremyKing ,ChrisKoresko, M. Kusunose, Alex Lazarian, Zong-WeiLi ,Matt Richter, JuditGyorgyey Ries, YaronSheffer, Keith L.Thompson, and LifanWang.

1.4 Senior Research Support and Administration

HET Project Manager: Tom Sebring.Special Assistant to the Director: Joyce C.Sampson~De-

velopment!.

g

e

a

cre

bth

yof

ph

o

-

tenerinirtora

m

r

he

on-

n-l

ee-is-

ent

ce

le 5

gd

-ys-

r

r

-ics2

rar-15ion

eas

ar-the

of

atice

gal-ics

638 ANNUAL REPORT

Associated member of another department: Raynor L.Duncombe, Professor of Aerospace Engineering and Enneering Mechanics.

Director of the McDonald Public Information Office: San-dra L.Barnes.

McDonald Supervisors: GordonWesley ~mechanical en-gineering!, EdwardDutchover, Jr.* ~administrative support!,EarlGreen* ~observing support!, George E.Grubb* ~physi-cal plant!, Mark Cornell ~computing systems!, Phillip Mac-Queen~CCD Development!, Alvin L. Mitchell ~engineeringsupport!, and Jerry R.Wiant* ~MLRS!.

Administrative Services Officer: CecilioMartinez

1.5 Visitors and Affiliations

Dr. RobKennicutt , of the University of Arizona, visitedin the fall as the Beatrice M. Tinsley Visiting Professor. Hgave a series of lectures on extragalactic astronomy.

The Antoinette de Vaucouleurs Medal for this year wawarded to Dr. DonOsterbrock, Lick Observatory. He gavethe medal lecture entitled ‘‘The Nature and Structure of Ative Galactic Nuclei.’’ In addition, he gave the public lectu‘‘Active Galaxies in the Universe.’’

In addition to these visitors whose visits were fundednamed programs, the following people were visitors todepartment for periods of one week or longer:

M. de Fatima Saraiva, University of BrazilH. Dekker, European Southern ObservatoryP.Diener, University of CopenhagenJ.Laird , Bowling Green State University I.Lichtenstadt,Hebrew University of JerusalemB. Milvang-Jensen, Copenhagen University ObservatorI. Novikov, Theoretical Astrophysics Center, UniversityCopenhagenK. Oliveria Filho, University of BrazilE. Oran, Naval Research LaboratoryJ.M.Owen, Ohio State UniversityJ.Stein, Hebrew University of Jerusalem quotation

1.6 Awards, Honors, and Special Activities

Inger Jo”rgensenwas awarded a Hubble Space TelescoPostdoctoral Fellowship. She will use her fellowship at tUniversity of Texas at Austin.

JohnLacy was selected by his peers as the recipientthe 1995 Board of Visitors’ Teaching Award.

Anita Cochran was a Councilor for the American Astronomical Society. Mary KayHemenway continued to serveas Education Officer for the AAS, on the American Instituof Physics Committee on Physics Education, as a liaisothe National Committee on Science Standards and Assment of the National Research Council, and on the SteeCommittee of the UT Women’s Faculty Organization. Sheon the national Steering Committee of the Coalition for EaScience Education. She also serves as Associate Directthe University of Texas Institute for Science and Mathemics Education. CraigWheeler was the Chair of the AASNominations Committee and was on the Tinsley Prize Comittee.

i-

s

-

ye

ee

f

toss-gshoft-

-

AnitaCochranwas elected Vice Chair of the Division foPlanetary Sciences of the AAS.

Art Whipple served his fourth year as secretary of tAAS Division on Dynamical Astronomy. PeterShelusserved his 17th year as treasurer of the AAS DivisionDynamical Astronomy. JuditRies is a member of the Committee of the Division on Dynamical Astronomy.

Anita Cochran served on the National Research Coucil’s Task Group on the BMDO New Technology OrbitaObservatory.

CraigWheeler served on the NASA Long-Term SpacAstrophysics Review Panel, the NASA Hubble Fellows Slection Panel, and the NASA Astrophysics Advanced Msion Concepts Review Panel. WilliamCochran served onthe NASA Origins of Solar Systems Program ManagemOperations Working Group. AnitaCochran served on theSolar System Exploration Subcommittee.

BevWills is a member of the STScI–NASA–ESA SpaTelescope Users’ Committee. ArtWhipple served on the So-lar System Panel of the Hubble Space Telescope CycTime Allocation Committee.

PaulShapiro was co-Chair of the Scientific OrganizinCommittee of ‘‘The Physics of the Interstellar Medium anthe Intergalactic Medium,’’ Elba, Italy, June 1994.

Greg Shields served on the Scientific Organizing Committee for the Fifth Mexico–Texas Conference on Astrophics held in Tequesquitengo, Mexico, April 2–5, 1995.

Tom Barnes served on the Organizing Committee foIAU Commission 27~Variable Stars!.

RobertRobbins was on the Organizing Committee foIAU Commission 46.

CraigWheelerwas on the International Organizing Committee for the Texas Symposium on Relativistic Astrophysand the Organizing Committee for IAU Commission 4~Close Binary Systems!.

PaulShapiro was a visiting member of the Institute foTheoretical Physics, University of California at Santa Bbara, for one week in March 1995 and on May 15–Juneas a participant in the 1995 Workshop on Galaxy Formatand Radiation Backgrounds at the ITP.

CraigWheeler was on the Executive Committee of thBoard of Trustees for the Aspen Center for Physics. He walso on the Admission Committee for this center.

RobertRobbins designed and presented a four-daychaeoastronomy workshop for college teachers underauspices of the NSF-Chautauqua program.

Larry Trafton continues to serve as an Associate EditorIcarus.

GregShieldsspent the spring 1995 semester on leavethe Department of Space Physics and Astronomy at RUniversity. At Rice, he worked with Dr. R. Dufour onHubble Space Telescope observations of dwarf irregularaxies and delivered the Marlar Graduate Lectures on ‘‘Topin Active Galactic Nuclei’’~May 1995!.

2. ACADEMIC AND EDUCATIONAL PROGRAM

2.1 Graduate Program

The Graduate Studies Committee Chair was EthanVish-niac with Graduate Advisor NealEvans.

tia

arls

o-tnr-the

y

ve

uc

o

y

rf

iesanddu-ingool

rday24for27lso11

hasa-t ofthe

ndre-u/

eryob-al.’pe-stu-

ofzingthe

rgyJu-

r-ficease, a

ells’

639UNIVERSITY OF TEXAS

The Fred T. Goetting, Jr. Memorial Endowed PresidenScholarship was awarded to MichaelMontgomery, who wasstudying asteroseismology of white dwarf stars. The Boof Visitors Graduate Student Endowment Fund was aawarded to MichaelMontgomery. The David Alan BenfieldMemorial Fellowship was awarded to ChuckClaver, whostudied the age of the Milky Way using white dwarf chrnometry. Rene´ Plumewon the first prize in the URSI studenessay contest, for his paper ‘‘The World’s Smallest TeMeter Submillimeter Telescope.’’ URSI is a international oganization of radio and millimeter-wave engineers, andprize included a $1000 cash award and a trip to BouldColorado, where the award was presented.

Graduate students in 1994–1995 were RobertBenjamin,Jay Boisseau, Michael Brotherton , David Chappell,JungyeonCho, Minho Choi, CharlesClaver, AlejandroClocchiatti, Cecilia Colome, JamesDiFrancesco, CynthiaFroning, Niall Gaffney, Youxin Gao, Erik Gregersen, JimHeath, Daniel Hiltgen, Antonio Kanaan-Neto, LukeKeller , Soon-WookKim , Scot Kleinman, Eric Klumpe,Paul Kornreich , Anand Kudari , Wenbin Li , Zhiqing Li ,Yingming Lou, MichaelLuhman, ShanLuo, FengMa, By-ron Mattingly , RebeccaMcQuitty , MichaelMontgomery,MichaelMoscoso, AtsukoNitta , FredOrtiz , SoojongPak,RenePlume, Divas Sanwal, SusanTrammell , JoeWang,QiangguoWang, YangshengWang, LanceWobus, VincentWoolf, ChangsongZhang, and EricZink .

Doctoral Dissertations: Nine Ph.D. degrees in astronomwere awarded in 1994–1995:

• RobertBenjamin ~Supervisor P. Shapiro!: ‘‘The Originand Evolution of Galactic Halo Gas’’

• Minho Choi ~Supervisor N. Evans!: ‘‘Study of MassiveStar Formation Regions With a Monte Carlo RadiatiTransfer Method’’

• ChuckClaver ~Supervisor E. Nather!: ‘‘The Age of theMilky Way Galaxy From White Dwarf Chronometry’’

• Alejandro Clocchiatti ~Supervisor C. Wheeler!: ‘‘Su-pernova Spectroscopy’’

• Soon-WookKim ~Supervisor C. Wheeler!: ‘‘Topics inAccretion Disk Instabilities:~1.! Magnetized Disks inIntermediate Polars and GK Per, and~2.! IrradiatedDisks in Black Hole X-Ray Novae’’

• MichaelLuhman ~Supervisor D. Jaffe!: ‘‘Near-InfraredMolecular Hydrogen Emission as a Probe of the Strture of Photodissociation Regions?’’

• RenePlume ~Supervisor D. Jaffe!: ‘‘A Study of Warm,Atomic Gas in the Interstellar Medium’’

• Susan Trammell ~Supervisor H. Dinerstein!: ‘‘TheStructure of Objects in Transition from the AGB tPlanetary Nebula’’

• YangshengWang ~Supervisor N. Evans!: ‘‘From DenseCores to Protostars’’

Master’s Theses: Four Master’s degrees in astronomwere earned in 1994–1995:

• Michael Montgomery ~Supervisor D. Winget!: ‘‘TheAsteroseismology of White Dwarf Stars’’

• Divas Sanwal ~Supervisor E. Robinson!: ‘‘OpticalStudy of Pulsars’’

• Vincent Woolf ~Supervisor D. Lambert!: ‘‘The

l

do

-

er,

-

r -Process Element Europium in F and G Disk DwaStars’’

• Luke Keller ~Supervisor D. Jaffe!: ‘‘The Large ScaleDistribution of H-Alpha and @FeII# 1.6435 MicronEmission in IC 443’’

2.2 Undergraduate Program

Derek Wills is the chair of the Undergraduate StudCommittee. There were 39 astronomy majors this year,two students received BAs. Dan Jaffe served as Undergraate Advisor. Eric Berger was awarded the OutstandGraduating Senior Award. He is going on to graduate schin science journalism at the University of Missouri.

2.3 Educational Services

Operation of the nine-inch refractor~Painter Hall Obser-vatory! was directed by Antoˆnio Kanaan-Neto. The PainteHall Observatory hosts public star parties every Saturnight. From September ’94 until September ’95, we hadstar parties receiving a total of 617 visitors. Star partiesUT students were held every Monday night, and we hadof them bringing a total of 107 visitors. The Observatory agives tours to school groups; during this year we gavegroup tours with a total of 165 visitors.

Judit Ries, as Education Services Office manager,compiled and installed an electronically accessible informtion system about the department. Thus, the DepartmenAstronomy is the first of the departments to appear onUniversity-wide ITower system.

A World Wide Web home page~currently http://www.as.utexas.edu/! was established for the Department aObservatory. In addition, a WWW abstract server for pprints was created~currently http://abstract.as.utexas.edabstracts.html!.

The Educational Services Office hosted star parties evWednesday while UT was in session on the 14th floorserving deck of RLM. About 400 people attended in totOn July 19th, the NASA documentary ‘‘A Time of Apollo’was shown to commemorate the National Space Week. Scial solar tours are also arranged through the ESO fordents ranging from second grade to eighth grade~attendanceabout 700 total!.

Judit Ries, Derek Wills, and Lara Eakins, with the helpastronomy graduate students, hosted a special stargaparty on July 28th at the 16-inch telescope on the top ofRLM building for 60 high school honors students.

The department also participated in the Texas EneSymposium for high school students and teachers, wheredit Ries gave a talk on energy production in the stars.

2.4 Public Information Office

The Public Information Office moved from 2601 Univesity to 2609 University and added 2,000 square feet of ofspace. The W.L. Moody, Jr. Visitors’ Information Center wrenovated to add 400 square feet of gift shop floor spacpartition to the theater area, and office space.

Funding totaling $180,000 was received from the AbHanger Foundation to build the George T. Abell Visitor

e-aaadtadta

tencdrrAsto

th

n

b

eoTh

ainuybyaor

ciis

vm

ofrd,

ndesdet

oioorim

aryricalce.rastelror

c-roruralignpo--

hisle-en-le-tothe

heThetheisa-orforrly

orl 95orre-ousofd itcy.andureonat-ght,andlity-me-ich

aryedowreal-ele-rorn-

640 ANNUAL REPORT

Gallery. This will be adjacent to the Hobby-Eberly Telscope. Conceptual drawings for a 7,000-square-foot expsion to the Visitors’ Center were developed. Plans foroutdoor expansion which adds an amphitheater, pavilion,the Rebecca Gale Astronomical Park were also develope

Universo, the new Spanish language version of the SDate radio program, was launched. The series exceedefirst major milestone in August by adding over 60 radio stions that are airing the program in Spanish. The programproduced at KXCR studios in El Paso and is also markeout of those studios. Teresa Fendi de la Cruz is the annoufor Universo, Arturo Vasquez is the co-producer, Armandola Fuente assisted with the marketing, and Rosario H. Tois the translator. Technical editors include Jorge Lopez,sistant Professor of Physics, UT El Paso; Carmen PanArecibo Observatory; and Celia Colome´, UT Austin. TheUniverso series is made possible with grant funding fromNational Science Foundation and NASA.

Funds from NASA Astrophysics Grants to SupplemeEducation funded theGuide to the Solar System. Ethan Vish-niac is PI on the grant, and the production is being donethe Public Information Office.

A new 16-inch Meade telescope and CCD camera wadded at the Visitors’ Center. They are housed in a 20-fdome that previously housed the 30-inch telescope.dome has been refurbished at the Visitors’ Center site.

The StarDate radio program continues to broadcast toaudience of 2.5 million daily on over 200 radio stationsthe U.S. Sternzeit, StarDate’s German counterpart, continto broadcast on Deutschland Radio in Cologne, Germanan audience of 20 million daily. Sternzeit is producedAxel Scheibchen and directed by Edgar Forschbach; thenouncer is Gu¨nther Dybus. Forschbach also heads up ‘‘Fschung Aktuell’’~Current Research!, a daily half-hour infor-mation program that incorporates Sternzeit.

StarDatemagazine added an 800 number to increaseculation and over 80,000 copies were circulated. The Vtors’ Center served over 130,000 visitors and continuedprovide the astronomy curriculum for the Prude Ranch enronmental education program and the Elderhostel progra

3. RESEARCH PROGRAM

3.1 Future Plans: The Hobby-Eberly Telescope

The Hobby-Eberly Telescope project is a joint effortthe Univerisity of Texas, Penn State University, StanfoUniversity, the Ludwig Maximilian University in Munichand the Georg-August University in Go¨ttingen.

Substantial progress has been made in the constructiothe Hobby-Eberly Telescope during this reporting perioGround was broken in May of 1994. By September, progrhad been realized in the pouring of foundations, in thetailed design of the telescope structure and dome, and indevelopment of a process for manufacturing the mirrors.

In November, final acceptance testing was performedthe Center of Curvature Alignment Sensor, the polarizatshearing interferometer to be used to sense the relative ptions of the 91 one-meter mirrors which make up the pmary. Bids were received for the tracker system in Dece

n-nnd.r-its-isderees-ja,

e

t

y

reote

n

esto

n--

r-i-toi-.

of.s-he

nnsi---

ber, with Orbital Sciences Corporation the winner. In Janu1995, Eastman Kodak completed a redesign of the spheaberration corrector to achieve better optical performanThe new design featured four reflective elements in contto the original design’s two. At this point, structural steerection at the facility was nearly complete, and 36 mirsegments were in fabrication at Eastman Kodak.

In February, Mero Structures of Wurzburg, Germany ocupied a portion of the site to assemble the primary mirtruss. This 11-meter truss utilizes more than 1700 structmembers to support the primary mirror segments. Its desis such that manufacturing tolerances alone control nodesition to within 4 mm, allowing simple, bolt-together assembly at the site.

Erection of the enclosure dome began in March. At tpoint, the initial phase of construction was nearing comption, with the control and service building and telescopeclosure enclosed and ready for the installation of the tescope structure. A layer of finely finished concrete, flat0.010 inch, had been applied to the telescope pier forstructure azimuth rotation air bearings to run on.

In April, Comsat/Radiation Systems, Inc. occupied tsite to commence installation of the telescope structure.base portion of the structure was assembled in place, andcompleted primary mirror truss was lifted into place. Thtruss sits on kinematic mounts which prevent any deformtion of the telescope structure from affecting primary mirrfigure. On 28 June, the HET structure rotated in azimuththe first time. The framework for the dome was very neacompleted adjacent to the telescope enclosure.

By June, twelve shipments of zerodur primary mirrblanks from Schott had been received, and 65 of the totamirror blanks were at Eastman Kodak. The first two mirrblanks were completed and met optical and dimensionalquirements. Mirrors are being fabricated using a continuplanetary polishing process with final ion figuring. Testingthe mirror support prototype was completed at Kodak, anmet requirements for repeatability and positioning accura

In July, the structure had been completely assembledthe enclosure dome was lifted into place atop the encloswalls. The first two mirrors were transported to DentVacuum for use in development of the protected silver coing process. In August, the dome was made weather tiand Phase II of construction began. Between AugustJanuary 1996, the interior and exterior finishes of the faciwill be applied, all electrical wiring and plumbing completed, and the environmental controls completed. The dowill then be completed and the HET Project Team will commence installation of the computers and equipment whmake up the telescope control system.

First light is expected in the summer of 1996, withpartially filled primary mirror array and using a temporatwo-element surrogate corrector. At first light it is expectthat the telescope will acquire, track, form images, and allassessment of the expected optical performance to beized. Completion of the telescope and dedication to full timoperations is planned for mid-1997. The Hobby-Eberly Tescope is unique in that it features the largest primary mirin the world, utilizes a 9-meter pupil in its Arecibo-type co

o

ooauls

e

foetfoctrhan9etthsr.h.8

jotabouvi.aintein

rkhasunte-

ono-avear-y, C.ewtheITE

seg-ndle-vail-firstJ.van-or-canformndewud

ngm-the

andlete

-ven

heef-hat-

and

sesands-torcs.er.orn,tem

CD-o-


figuration, and yet is being constructed for a total cost$13.5 million, including all labor and materials.

3.2 Observing Conditions at McDonald Observatory

A summary of the hours scheduled, hours lost to pweather, hours lost to telescope/instrument problems,hours assigned to maintenance is given below. Schedhours are measured from civil twilight to civil twilight, pluany especially scheduled daytime hours.~The daytime hoursfor all four telescopes together total only 52 hours.! Category‘‘Other’’ is comprised primarily of time when the telescopwas not scheduled or no program object was available.

Since the 2.7-m telescope is used almost exclusivelyspectrometry, a reasonable estimate of the spectromweather can be obtained from its records. After correctingdowntime due to maintenance, equipment, etc., the spemetric time is estimated as 65% for the last fiscal year. Tvalue can be compared with 63% for the previous year,62.1% for a fourteen-year mean. Until fiscal year 1992–the 0.9-m telescope was used predominately for photomso its usage can be used to infer the photometric weastatistic.~Since 1992–93 the 0.9-m telescope has been umostly for programs not requiring photometric weathe!From the 0.9-m telescope statistics for 1981–1992, the ptometric weather at McDonald Observatory averaged 39of the available hours.

TABLE 1. Utilization Statistics for McDonaldObservatory Optical Telescopes~1994–1995! ~Hours!

2.7-m 2.1-m 0.9-m 0.8-m

a!* 4022 4019 4031 4011

b! 2383 ~62%! 2395 ~60%! 1296 ~32%! 1160 ~29%!

c! 1305 ~33%! 1330 ~33%! 1287 ~32%! 758 ~19%!

d! 42 ~1%! 48 ~1%! 27 ~1%! 107 ~3%!

e! 52 ~1%! 55 ~1%! 56 ~1%! 140 ~3%!

f! 139 ~3%! 191 ~5%! 1365 ~34%! 1846 ~46%!

*a! Scheduled; b! Observed; c! Lost to weather;d! Lost to telescope/instrument problems;e! Scheduled maintenance; f! Other

3.3 Scientific Results

3.3.1 Instrumentation:

Several significant developments occurred last yearcomputing systems at McDonald. Control of all of the mainstruments which use CCDs was transferred from VAXstion systems to Sun systems. The Sun systems use Sbased interfaces, developed by P. MacQueen’s CCD grand new software which runs under the IRAF Control Enronment~ICE!, developed by M. Cornell’s computing groupA major upgrade of the computing network to the mountwas also implemented. The old 9600-baud leased line sysbetween Austin and Mount Locke was replaced by a T1 l

f

rnded

rricro-isd3ry,ered

o-%

inr-us-p,-

me

which connects Mount Locke into the UT System netwovia the UT Permian Basin campus in Odessa. The T1 linebeen extended from Mount Locke to the adjacent MoFowlkes, where it will connect to the Hobby-Eberly Telscope facility now under construction.

There has been a great deal of excitement among astrmers the last few years as technological improvements hmade it possible to obtain high-resolution visual and neinfrared images from ground-based telescopes. P. HarveKoresko, and D. Sill began work in January 1994 on a nnear-infrared camera optimized for taking images athighest possible resolution. The new camera, named D-L~Diffraction-Limited Infrared Telescope Experiment!, is de-signed to be used for speckle interferometry at the Casrain focus of McDonald Observatory’s 2.7-m telescope aon the U.S. Air Force Starfire 1.5-m adaptive-optics tescope, which has recently been declassified and made aable to university astronomers. The new camera sawlight at McDonald in January 1995. In May, they joinedChristou and R. Fugate at Starfire to demonstrate the adtages of adaptive optics and speckle interferometry overdinary direct imaging and the greater advantage whichbe had when the two techniques are used together to per‘‘compensated speckle.’’ They are preparing for a secoStarfire trip in late October, when they hope to use the ninstrument to study the young stars in the Taurus Dark Clowith a superb combination of resolution and sensitivity.

R. Plume and D. Jaffe have modified their re-imagidevice for the Caltech Submillimeter Observatory to accomodate the new telescope secondary. Plume has useddevice to observe large-scale emission in neutral carbonin several CO lines and has now used the device to comphis Ph.D. thesis.

Following their initial work on front-surface micromachined gratings, L. Keller, T. Benedict, and D. Jaffe hafabricated an IR immersion diffraction grating on a silicoprism using standard photolithographic~chemical etching!techniques. They are currently working on improving tprocess to minimize surface defects and improve gratingficiency. The final product will be an echelle grating whichas. 3.5 times the resolving power of a front surface gring with identical size.

P. MacQueen, J. Graw, and G. Hansen have designedprototyped an 18-bit Analog Signal Processor~ASP! to re-place present and future McDonald analog modules. It uthree integrators for constant-gain readouts at 20, 50,100 kpixels s21. A checksum generator confirms data tranmission integrity. A versatile synthetic waveform generaand a power supply monitor provide detailed diagnostiThe prototype delivers a signal-to-noise ratio of ov200,000:1 and is linear to at least 30,000:1 peak-to-peak

P. MacQueen, G. Wesley, J. Graw, G. Hansen, J. Welband D. Edmonston commissioned a CCD detector syscalled TK3 with a Tektronix 2K32K, grade 1, thin CCD. Ituses a new 150-mm-diameter detector housing with a Cmount that flexes less than 0.1mm between any two orientations while leaking only 220 mW of heat. TK3 uses a prtotype ASP to provide a 180,000 e2 dynamic range with a3.5 e2 readout noise.

de2

aloG

eyof

tio

aundfig

tefnisnri-the-iervpin

gctoh-ilonmafo

-tv

-edIRhefieti

ioaebesi

giA

nyThe

tor-rom

-t

e,ntsch-

-ob-The

s-ofts.oryctsves

firstthenoatitK.

ted

heof

ker

ionuneures

ofL-9nrisonlaceced

642 ANNUAL REPORT

P. MacQueen, D. Edmonston, and J. Welborn upgrathe TK2 CCD system from use of a thin Tektronix 513512 CCD to a SITe 1K31K, thin, grade 1 CCD systemcalled TK4.

P. MacQueen and D. Edmonston upgraded the anelectronics of the RA2 CCD system which uses an EG&Reticon 12003400, thin CCD. MacQueen and J.F. Harvhave implemented a new lamp for efficient UV floodingRA2.

P. MacQueen and C. Claver developed a new collimatechnique for the 0.76-m Prime Focus Corrector~PFC!. Animage quality of 24mm FWHM can be achieved which islimit set by errors in the manufacture of the optics. The nlens for the tertiary mirror was found to be misfigured, ahas been reworked to allow the corrector optics to be reured.

W. Wren and C. Wheeler have constructed and dedicaa novel new telescope to be used for a visual searchnearby supernovae. This telescope sits on an optical bewith a fixed 18-inch primary mounted with its optical axhorizontal. The only moving part is a flat at the opposite eof the optical bench. The light path from the flat to the pmary is brought to focus through a hole in the center offlat to a fixed eyepiece. This configuration will strongly rduce the observer fatigue involved from chasing the eyepin a normal equatorial mount telescope. Wren has obseseveral hundred galaxies a night with orthodox telescoand has discovered SN 1992H and SN 1994Y. This newstrument should make his work more efficient.

G. Hill, B. Wills, and K. Thompson have been continuinconstruction of the dual-beam spectrograph for the MDonald 2.7-m. The spectrograph will cover 3150 Å11,000 Å atR5700 simultaneously through use of a dicroic beamsplitter. Optimized red and UV-blue coatings wyield high throughput over the entire wavelength range. Cstruction of the red arm of the spectrograph will be copleted in early 1996, and it will be used on the 2.7-m asefficient red spectrograph while the custom CCD camerathe blue arm is constructed.

G. Hill upgraded the ROKCAM IR imager with new optics and mechanical design. Gordon Wesley assisted inmechanical design. The upgraded instrument has improimaging and is parfocal over theJ, H, andK bands. DarrenDePoy~Ohio State University! designed the optics. The instrument will reenter service in December. Hill completthe optical design for Coolspec, an innovative cooledspectrometer to mate with the ROKCAM IR imager on t2.7-m telescope. The instrument has a simple modiCzerny-Turner design and a 50-mm beam size. Construcof Coolspec is continuing, and the instrument is expectedsee first light in 1996.

R. Tull and colleagues are planning a high-resolutbroad-band optical spectrometer for the HET. The local teincludes P. MacQueen, C. Sneden, W. Cochran, D. Lamband A. Hatzes. The international team also includes memat the HET member organizations at Penn State Univerand the Universities of Munich and Go¨ttingen. More thanhalf the needed funding has been raised through privateto the University together with state of Texas and NAS

d

g

n

ll

-

dorch

d

e

ceedes-

-

l--nr

heed

donto

nmrt,rsty

fts

contributions plus University of Texas matching funds. Maof the major optical components have been ordered.needed CCDs for a mosaic of two 204834096 chips with 15mm pixels were recently produced at ORBIT Semiconducin collaboration with the Lick Observatory CCD Lab. A proposal has been prepared to seek the remaining funding fNSF. Completion is planned for 1998.

G. Hill is leading the design team for the HET lowresolution spectrograph~LRS!. The design is an efficiengrism spectrograph covering 0.4 to 1.4mm atR5500–4000. Hill has assisted Larry Ramsey~HET ProjectScientist! with the design of the tracker optical packag~TOP! for the HET, which will provide acquisition, guidingfiber-feed control, and interface to prime-focus instrumefor the telescope. Hill was also a member of the HET Tenical Steering Committee.

3.3.2 Solar System:

A. Cochran, H. Levison, A. Stern~SwRI!, and M. Duncan~Queen’s University! announced their detection of 5–10 kmsized bodies in the Kuiper Belt. The observations weretained with the WFPC2 on the Hubble Space Telescope.detected population of 29 objects in less than 4 arcmin2 im-plies a population of 23108 objects of 5–10 km in a regionof the Kuiper Belt with inclinations less than 12° and ditances from the Sun of less than 40 AU. This populationobjects is sufficient to supply the known short-period come

Observations obtained by the McDonald ObservatComet Impact Science Team during the R, U, and V impaof Shoemaker-Levy 9 on Jupiter were analyzed. Light curwere derived from images obtained at 2.12mm ~pressure-induced H2) and 0.89mm ~CH4) with the 2.7-m and 0.76-mtelescopes at McDonald Observatory, respectively. Theprecursor flash and the main event were clearly seen in2.12mm data for the R impact, but this impact producedflash at 0.89mm. From the upper limit on the flux increaseCH4 and the detection at H2 , the team derived an upper limtemperature for the main event of the R impact of 1300The U impact produced a very small flash at 2.12mm, cor-responding to the main event. No impact flash was detecfrom the V impact.

Follow-up observations of the long-term effects of timpact of Comet D/Shoemaker-Levy 9 on the atmosphereJupiter were obtained by A. Cochran, W. Cochran, E. Bar~NASA HQ!, W. Pryor ~LASP!, and C. Na~LASP!. Thesedata included CCD images, and low- and high-resolutspectroscopy. By the time of the last observations in J1995, the obvious prominent southern hemisphere feat~dark in the continuum and bright in CH4 bands! had fadedsignificantly.

L. Trafton participated in the reduction and analysisspectroscopic data taken during the impact of Comet Swith Jupiter last year at the UKIRT and HST. Information othe composition and distribution of impact-generated debwas extracted and published. This included informationJupiter, the comet, and the chemical processes taking pduring the impact. Sulfur-bearing compounds and enhanNH3 were detected.

M. Brown ~LPL!, A. Bouchez~UC Berkeley!, H. Spinrad

nis

oarhens

ora

reheocaer,lientnct

rbioofata

putn-e

rsio

aan

ehe-omalioowygnite.

hethb

on-o-oth

rdtro-a-10’smeed,to-if-

amrd.us

i-r itnicOomplesore

’’ur-thene-canb-ob-forow-ro--

-ityichheferic

calez-foroids433o

eanbyart


~UC Berkeley!, and C. Johns-Krull analyzed high-resolutiospectra of the comet P/Swift-Tuttle for the presence of emsion in the OH Meinel system. The high resolution (R'60,000! of the spectra and the large heliocentric velocitythe comet permit easy separation of these lines from neOH sky lines. No OH Meinel lines were detected in tcomet, consistent with theoretical calculations of prompt afluorescent cometary emission and contrary to reports baon low-resolution work.

Observations of the distribution of OH in the comaecomets were continued as part of a program by A. Cochand D. Schleicher~Lowell Observatory! to understand thephotodissociation of H2O as a function of changing solaactivity. An excellent set of observations of comets with hliocentric distances from 1–2 AU were obtained while tSun was at a minimum of activity. Observations obtaineddifferent comets on the same night showed that the slengths of the OH gas in the comae were different for diffent comets. Since the observations were the same nightphotodissociation lifetimes must be the same. This impthat the outflow velocities are quite different for differecomets and that the scale lengths are also dependent odensity of gas in the coma. Work continues on this proje

The McDonald Observatory Planetary Search~MOPS!program~W. Cochran and A. Hatzes! continued survey ob-servations designed to detect planetary systems in oaround nearby solar type stars. Extremely high-precismeasurements are obtained of radial velocity variationssample of 36 dwarfs and subgiants of spectral types F, G,K. A time series of such observations will reveal the orbimotion of the star around the star–planet barycenter. An2

gas absorption cell placed in front of the 2.7-m telescocoude spectrograph allows velocity precision of abo5–10 m s21 to be achieved. A companion southerhemisphere survey is being conducted at the EuropSouthern Observatory in collaboration with M. Ku¨rster, K.Dennerl, and S. Do¨bereiner~MPI Garching!. The ESO sur-vey uses an I2 absorption cell at the 1.4-m CAT. Three yeaof data from ESO have demonstrated a long-term precisof better than 10 m s21.

The Hubble Space Telescope Astrometry Science Tecontinues to monitor the nearby stars Proxima CentauriBarnard’s Star for low-mass companions~investigation leadby G.F. Benedict!. No new data for Proxima Centauri weracquired this year with which to either confirm or refute tweak perturbation detected atP;80 days. With 25 observation sets acquired over two years, there are no obvious cpanions to Barnard’s Star. Monte Carlo and Bayesian anses~D. Chappell! yielded present companion mass detectlimits for both Proxima Cen and Barnard’s Star at or belone Jupiter mass for periods ranging from 100 to 600 daRe-application of their continually evolving and improvinastrometry reduction procedures have resulted in a sigcant increase in the precision with which the team demines the parallax and proper motion of Barnard’s Startime-dependent version of their master calibration~OFAD!and a correction of an obvious systematic signature in tcalibration residuals reduced by nearly a factor of twoformal uncertainties. Should Barnard have no detecta

-

fby

ded

fn

-

nle-thes

the.

itnandlIe

an

n

md

-y-n

s.

fi-r-A

irele

companions, these data will still have great value as a ‘ctrol’ in the Proxima Cen ‘experiment.’ Systematics intrduced by HST or the FGS are present in the data for bstars.

Anything detected in the Proxima data not in the Barnadata becomes less likely instrumental, and more likely asnomical. The intrinsic value of additional Barnard observtions prompted the Astrometry Science Team to dedicateCycle 5 GTO orbits to continued monitoring of BarnardStar. Benedict secured 10 additional orbits of HST GO tito continue monitoring Proxima Cen. They have determinwith the HST data, that Barnard’s Star is a periodic phometric variable, and can report that the period is clearly dferent than that found for Proxima Centauri. Benedict~as-sisted by P. Shelus, A. Whipple, and D. Cornell! hasinstigated a ground-based photometric monitoring progrto confirm or refute the period indicated by HST for BarnaThey are using the McDonald Observatory Prime FocCamera.

L. Trafton participated in an HST study of Io’s SO2 UVspectrum with J. Caldwell, C. Cunningham~both York Uni-versity!, and C. Barnet~GSFC!. They found new, larger,lower limits to the portions of Io’s leading and trailing hemsphere covered by the gas. Io’s atmosphere is too thin foto envelope Io; it resides near sunlit ices and volcasources. They also further constrained the maximum S2

column abundance and argued that the UV results differ frthe mm-wave results because the latter technique samessentially only the hot gas over volcanoes, which is mabundant than elsewhere.

L. Trafton extended his ‘‘Detailed Balancing Model~DBM! of the interaction between the vapor pressure of sface ices, the relative composition of ice volatiles, andatmospheric composition he developed for Pluto’s methanitrogen atmosphere to Triton. He showed that the modelexplain Triton’s atmospheric methane/ nitrogen ratio oserved by the Voyager EUV experiment. This has been prlematical because this ratio is close to the value expectedthe pure ices but should be orders of magnitude smallering to the observed solution of solid methane in solid nitgen. Henry’s~or Raoult’s! law predicts that the vapor pressure of the minor constituent~methane! should beproportional to its mole fraction in the ice. The DBM resolves the conflict by invoking a compositional discontinuat the surface of the ice above which a thin methane-rlayer is maintained by interaction with the atmosphere. TDBM is an alternative to the ‘‘Hot Methane Patch Model’’ oStansberry for explaining Pluto’s enhanced atmosphmethane content.

A. Whipple and P. Shelus performed long-term numeriintegrations of the orbits of the Near Earth Asteroid Rendvous mission targets to determine the dynamical contextthe physical observations that will be made of these asterby the spacecraft. They found that the rendezvous target,Eros, is on a fairly chaotic orbit and that its proximity tMars (a.1.46 AU! places it in the middle of the very highorder mean motion resonances associated with the 1:1 mmotion resonance with Mars. They also found that the flytarget, 253 Mathilde, is located in a dynamically unusual p

a

ifi

-theidssenpometiondo

osindin

antesen-i

tonic

fea-hei

l

sitieiccndndis

r

tia

elsedles.hero-

rsin

dee-

two

ar

c-tricthetricionra-

atethanse

is

yyarctoratelyso-tal-ype

moreer-

nntrva-de-larthe

.-bleOb-e-

644 ANNUAL REPORT

of the asteroid belt. It is located just inside of the 11:4 memotion resonance with Jupiter and near theg22g61g5secular resonance. These resonances have caused signdepletion of the asteroid belt in the vicinity of Mathilde.

A. Whipple calculated the Lyapunov times for all numbered asteroids whose current perihelion distance is less1.6 AU to investigate the structure of chaos in the innasteroid belt. He found that the planet-crossing asterohave extraordinarily short Lyapunov times, virtually all lethan 5000 years. The Lyapunov time was found to depvery strongly on perihelion distance. These results supthe conclusion that the predominant cause of the extrechaos among the planet-crossing asteroids is their closecounters with the terrestrial planets rather than mean moand secular resonances. The magnitude of the chaos fouthese asteroids severely limits the ability to predict their mtions for even centuries.

J. Ries and W. Jefferys carried out a preliminary studythe application of Bayesian method for lunar data analyAccording to the study, identification of lunar returns arecovery of earth orientation parameters is promising usthis technique.

3.3.3 Stars and Stellar Systems:

T. Barnes with T. Moffett~Purdue University! examinedthe uncertainties~random and systematic! in the visual sur-face brightness technique~Baade-Wesselink method! as ap-plied to Galactic Cepheid variables. Gieren, Barnes,Moffett had used this technique to establish the most exsive Galactic Cepheid period–luminosity relation to date,it is important to understand the uncertainties in it. Thshowed that the random error in a single Cepheid distameasurement is68% and that an upper limit to the systematic uncertainty in the surface brightness PL relation66% in distance. These combine, for a single Cepheid,typical uncertainty of610% and, for samples larger than teCepheids appropriate to studies of other galaxies, to a typuncertainty of less than66% in distance.

J. Fernley~ESA-Vilspa! and T. Barnes completed most othe observations of the Hipparcos RR Lyrae stars for mradial velocity and for metallicity. These data will be combined with Hipparcos proper motions for a new study of tmean absolute magnitudes of RR Lyraes. This work iscollaboration with D.W. Evans~RGO! and Suzanne Hawley~Michigan State University!.

T. Moffett ~Purdue University!, T. Barnes, and W. Gieren~Catholic University, Santiago! completed their observationaprogram to determine high-qualityBVRIphotometry of thoseLMC/SMC Cepheids with existing, precise radial velocitieThese 22 stars are also being investigated for metallicusing the CTIO 4-m telescope in the fall 1995 MagellanCloud season. When the data are complete, Barnes andlaborators will be able to check the metallicity pattern fouby Luck and Lambert for Magellanic Cloud Cepheids awill do a surface brightness analysis for the LMC/SMC dtances.

C. Johns-Krull examined three rapidly rotating T Taustars~HDE 283572, RY Tau, and SU Aur! and a half-dozenrapidly rotating Pleiades F stars for evidence of differen

n

cant

anrs

drten-nin-

ns.

g

dn-oyce

sa

al

n

n

.s

ol-

-

i

l

rotation. Recent theoretical investigations predict large levof differential rotation in these stars which can be discernin the shape changes produced in the absorption line profiAnalysis of line profiles in the above stars show that tlarge levels of differential rotation are not present. The pfiles suggest that modest levels of ‘‘anti-solar’’~polewardacceleration! differential rotation may exist in these stawhich if true could falsify the detection of polar spotsmany late-type stars using Doppler imaging techniques.

C. Johns-Krull and J. Valenti~JILA! have begun using thehigh-resolution (R5 120,000! mode of the cross-disperseechelle spectrometer on the 2.7-m telescope to look for Zman splitting in theg52.5 FeI line at 8468.4 Å in dMeflare stars. To date, strong splitting has been detected instars~EV Lacerta and Gliese 729! indicating large magneticfields (.3 kG! covering substantial amounts of the stellsurface (.50%).

G. Basri ~UC Berkeley!, K. Stassun~Wisconsin!, R.Mathieu~Wisconsin!, C. Johns-Krull, G. Marcy~SFSU!, andJ. Valenti~JILA! have analyzed several high-resolution spetra of the T Tauri star DQ Tau and found it to be an eccen('0.6) double-lined spectroscopic binary system. This islatest spectral-type T Tauri binary discovered. Photomemonitoring of this system also indicates that the accretrate of material from the disk to the primary increases dmatically just before periasteron.

C. Johns-Krull, S. Hawley~Michigan State!, G. Basri~UCBerkeley!, and J. Valenti~JILA! are currently analyzinghigh-resolution echelle spectra of a solar flare obtainedLick Observatory in 1993. Initial results show that thBalmer decrement in solar flares is substantially steeperin flare on dMe flare stars. In addition, comparison of thespectra with the flare models of Hawley and G. Fisher~UCBerkeley! indicate that the coronal pressure in flare loopshigher than previously thought.

V. Woolf, J. Tomkin, and D.L. Lambert completed a studof the abundances of ther -process element Eu in 81 nearbfield F and G disk dwarfs. In comparison with the solabundance ratio, the stars’ Eu/Fe ratio increases by a faof three as their Fe abundance decreases from approximtwice the solar Fe abundance to approximately one-tenthlar. The relative increase of the Eu abundance in the medeficient stars, which are also the older stars, points to TII supernovae as the site of ther -process. Although this trendhas been seen before, the new Eu abundances correlateclosely with predictions based on models of Type II supnovae than previous data have.

J. Tomkin and D.L. Lambert completed high-resolutioobservations of the 7800 Å RbI line in metal-deficiedwarfs and giants. Reduction and analysis of the obsetions are in progress and show that the RbI line can betected down to metallicities as small as 1/30 of the sometallicity. Rb abundances are of interest as a monitor ofneutron density at thes-process site.

G. Gonza´lez, in collaboration with D. Lambert and SGiridhar ~Bangalore, India!, has been working on a longterm project to estimate abundances for RV Tau variastars. The observations are being obtained at McDonaldservatory. RV Tau’s are highly evolved low- or intermediat

heinr

ethe-

tu

aeimoaaeathraigcaiochvim

erwemstesteneseiceIch

leedethde

er

ndenon

tainofthe

the50ra-ts

allevelpernthisan

ryto

an-hy-za-ingareeden-htbeof

ass

eyave

arethatpi-

r

d atorefortel-eu-tarypo-in,

c-herneve-tnd


mass stars considered to be in a post-AGB phase of tevolution. The results of this study should reveal somethnew about the chemical enrichment histories of these sta

P. Hoflich ~Harvard! and A. Khokhlov analyzed Type Ialight curves and compared them with observations of numous individual observed supernovae. They concludedH0 5 696 10. The Pskovskii–Branch–Phillips relation btween the brightness and post-maximum decline of Typesupernovae light curves was interpreted and explained inframework of the delayed detonation scenario by M. HamM. Phillips, N. Suntzeff~all CTIO!, Hoflich, Khokhlov, andC. Wheeler.

For his Ph.D. dissertation, A. Clocchiatti showed thsome supernovae classified from their maximum light sptra as helium-deficient Type Ic nevertheless have late-tlight curves very similar to some helium-rich, hydrogen-poType Ib and to the peculiar Type II SN 1993J. The fact ththese supernovae display a range in ejecta velocitieshence presumably ejecta mass suggests that some of thdioactive matter that powers the light curve is not participing in the overall homologous expansion. If that were tcase, the events with smaller mass would trap gammafrom radioactive decay less efficiently and have steeper lcurves. Some Type Ic events do, in fact, have steeply deing late-time light curves so that the spectral classificatalone is not sufficient to characterize these events. Clocatti also showed that all Type Ic plausibly show weak edence for helium in the optical, so that they are not copletely helium deficient.

M. Adams, W. Wren, M. Ward, L. Wang, and C. Wheelhave begun a search program for supernovae in clustersredshift in the rangeZ 5 0.03–0.15. This search will takadvantage of the wide field of view of the Prime Focus Caera on the 0.76-m telescope to survey entire Abell clustera single image. The McDonald program will help elucidathe dependence of the variation of properties of Type Iapernovae, especially the light curve amplitude/shape, onmorphological type of the host galaxy. This will strengththe ability to use Type Ia supernovae as ‘‘calibrated candlto determine the distance scale. They will specifically survthe Abell clusters analyzed by Lauer and Postman whshowed a velocity dipole with different orientation from thcosmic background radiation and from samples of Typesupernovae. They will apply the Type Ia supernovae tenique directly to the Lauer–Postman clusters.

L. Wang and C. Wheeler, in collaboration with the HubbSpace Telescope Supernova Intensive Study Team headR. Kirshner ~Harvard!, have analyzed the very late timspectra of SN 1987A obtained with HST. The spectra ofejecta show that the gas is very cold despite being heategamma rays. A feature in the blue is identified as the Balmcontinuum and its profile used to determine that the tempture in the ejecta nebula is 400–500 K. The doublet@OI#ll 6300, 6364 still does not display the ratio of three to oexpected of optically thin emission. The argument is mathat the lines are optically thin, but that the observed intsity ratio is altered because the line profiles are nGaussian.

L. Wang, A. Clocchiatti, Z. Li~Beijing Normal Univer-

irgs.

r-at

Iahey,

tc-ertndra--eyshty-ni---

ith

-in

u-he

’’yh

a-

by

ebyra-

ee--

sity!, and C. Wheeler have begun a new program to obroutine photometric and spectropolarimetric observationsbright supernovae. They have observed 6 supernovae infirst two trimesters of this program, thereby increasingtotal sample of supernova with polarization data by overpercent. Combining the new data with results from the liteture reveals a potentially critical dichotomy. Of the evenwith reliable~multi-wavelength, multi-epoch! data for whichthe effect of the ISM can be corrected, it appears thatType II supernovae are polarized at about the 1 percent land that Type Ia supernovae are unpolarized with an uplimit of about 0.2 percent. The Imaging Grating Instrumehas been adapted to do imaging or spectopolarimetry. Twill be much more effective for background subtraction ththe instrument used in the preliminary program.

P. Hoflich ~Harvard!, C. Wheeler, D. Hines~Arizona!, andS. Trammell~Chicago! have analyzed the spectropolarimetof SN 1993J more thoroughly. The observations seemshow that the intrinsic polarization did not change substtially while the photosphere receded down through thedrogen envelope and into the helium mantle. The polarition can be modeled by an ellipsoidal electron-scatterenvelope with an axis ratio of about 1.6 to 1. The dataconsistent with a geometry in which the ellipsoid is viewnearly edge on and which does not display a very steep dsity gradient just after the second maximum of the ligcurve. The constancy of the polarization may, however,more consistent with a deeply buried off-center sourceluminosity, perhaps a bubble of radioactive nickel, in a mdistribution with smaller geometrical distortion.

Z. Li ~Beijing Normal University! and C. Wheeler re-examined the dependence of Type Ia supernovae on thHband luminosity in galaxies of varying Hubble type. Theconfirm the earlier study by van den Bergh that spirals ha much higher rate per unitH band luminosity than do ellip-ticals. This suggests that Type Ia have progenitors thatnot associated with old, red companion stars and perhapssome younger population is providing the higher rate in srals.

3.3.4 Interstellar Medium, Compact Regions, ProtostellaDisks, Star-Forming Regions:

H. Dinerstein, C. Sneden, and J. Uglum~Stanford! pub-lished results from a survey of planetary nebulae observehigh spectral resolution in the NaI D resonance lines. Mthan half of their sample of 21 nebulae showed evidenceNaI lines associated with the nebula, in addition to interslar features. They interpret this as strong evidence that ntral circumnebular envelopes are prevalent among planenebulae; even in cases where there is no molecular comnent, there is often neutral, atomic material. DinersteSneden, and K. Volk~University of Calgary! are followingthis up with a new study using the 2.7-m ‘‘2-d coude’’ spetrometer to obtain broader wavelength coverage and higspectral resolution. This new survey will not only examiother resonance lines that might arise in the neutral enlopes of planetary nebulae~such as CaII, CaI, and KI, buwill also provide information on the expansion velocities aline profiles in the ionized and neutral layers.

ebiaon

niniaitr,n-on-srshe

inpa

ti

reedth5noha

oseesiougm

on

oladsilf

ichn,ai2

nin1taa

th

a

tos-

per

es,

rge

ether.illi-

ofcu-

ps

sityate

CIre-om-ofionoutom

calero-di-the

mo-he-let

thter.

dis-rf

is-

COrre-

ofelylar

646 ANNUAL REPORT

S. Trammell defended her Ph.D. dissertation on sptropolarimetry, spectroscopy, and imaging polarimetry of ojects undergoing the transition between the late red g~post-AGB! and planetary nebula phases of stellar evolutiUsing optical spectropolarimetry, she~together with H. Din-erstein, and R. Goodrich, STScI! established that more tha50% of a sample of 31 stellar objects identified as be‘‘post-AGB’’ stars show evidence for large-scale spatasymmetries, manifested as intrinsic linear polarization. WG. Hill, Trammell studied several more evolved ‘‘bipolanebulae,’’ including Gl 618, M 2-9, M 1-91, and M 1-92with a new imaging polarimeter, obtaining polarimetric iformation for images taken in both emission lines and ctinuum. The polarized~reflected! component shows a tendency for ‘‘flattening’’ of the position angles which containclues about the geometry of these nebulae; now at Univeof Chicago, Trammell is currently attempting to model treflection process, together with J. Kartje~University of Chi-cago!. The unpolarized component of the line emissionthese nebulae, which arises from shocks, reveals comstructures such as knots, ‘‘bars,’’ and arc-like structures.

J. DiFrancesco, N.J. Evans, and co-workers have conued to observe several Herbig Ae/Be stars at 2.7 mmsearch for direct evidence of circumstellar disks, mostcently with the IRAM interferometer. Of the 3 stars observso far this year, only Elias 1 appears to have emissionmay unambiguously be from a disk. In addition to thesources observed earlier, AB Aur and MWC 1080 weredetected, indicating any 2.7-mm emission is far below tpredicted by disk models.

In another attempt to determine the nature of their psible circumstellar disks, J. DiFrancesco and S.R. Tramm~University of Chicago! have observed 30 Herbig Ae/Bstars with the IGI spectropolarimeter at McDonald. Intereingly, about one third of the objects surveyed have emisslines that are polarized differently than the continuum, sgesting different sources of scattering within their circustellar environments.

Y. Wang and co-workers have published his workhigh-frequency line calibration standards for the CSO.

M. Choi and collaborators have published a re-analysisthe CS and H2CO emission lines toward the best protostelcollapse candidate, B335, using a new, more accurate rative transfer code. Choi and Evans developed this code uthe Monte Carlo method to be more flexible and seconsistent than previous codes.

M. Choi has developed a 2-D Monte Carlo code, whwill allow analysis of aspherical clouds, including rotatioas well as collapse and turbulence, in a self-consistent wThe first application of this code has been to model the emsion of a large number of molecular lines in the Mon Rmolecular cloud.

Y. Wanget al. have identified several more collapse cadidates in a sample of Bok globules, by comparing the lprofiles of C18O and H2CO lines at wavelengths aroundmm. Wang and Evans have completed a complemenstudy of CS emission from globules, which they are preping for publication.

E. Gregersen and N. Evans have surveyed most of

c--nt.

glh

-

ity

ct

n-to-

at

tt

-ll

t-n--

fria-ng-

y.s-

-e

ryr-

e

Class 0 sources~molecular cloud cores thought to be atvery early stage of star formation! in HCO1 J 5 4–3 and3–2 lines and have found several new candidates for protellar collapse.

S. Zhou, N. Evans, and Y. Wang have submitted a pareporting observations with BIMA of13CO and C18O J 51–0 emission from two protostellar collapse candidatL1527 and CB54.

J. DiFrancesco and collaborators have completed lascale maps in theJ 5 1–0 line of C18O of five cores in theTaurus molecular cloud, which will allow them to study thprocess which separates one star-forming core from ano

N. Evans has published the results of combined submmeter and infrared spectroscopy of GL2591.

K. Tatematsu and co-workers have submitted a studystructure in the outer parts of the Orion cloud using molelar line observations from the CSO. Tatematsuet al.find thatUV radiation affects the isotopic chemistry in the clumoutside the cloud core.

M. Choi et al. have published a paper with lower limiton emission of neutral carbon in the extremely-high-velocwings in molecular outflows, constraining the chemical stof the stellar wind.

R. Plume and D. Jaffe have completed a survey ofemission from three nearby dark clouds, using theimaging device on the CSO. Plume and Jaffe have also cpleted a study of CI emission from four molecular cloudsintermediate size and have obtained a map of CI emissfrom a strip covering 2 degrees in galactic longitude abthe galactic center. The CI emission most likely arises frPDRs distributed throughout the galactic center region.

M. Luhman and colleagues have detected degree-semission in the near-IR emission lines of molecular hydgen in the Orion clouds. Analysis of the line strengths incates that the emission arises in gas at the surface ofcloud which is excited by ultraviolet photons.

S. Pak and collaborators have detected large-scalelecular hydrogen emission from the inner 400 pc of tMilky Way, using the University of Texas Near-IR FabryPerot Spectrometer. This emission is excited by ultravioradiation from young stars and is similar to the H2 emissionin the nuclei of many other galaxies.

S. Paket al. have observed the Magellanic Clouds withe University of Texas Near-IR Fabry-Perot SpectromeThey detected H2 emission toward regions where no COJ 51–0 emission has been detected. Strong UV-fields maysociate CO molecules in low-metallicity regions like dwagalaxies. In these regions, near-IR H2 emission is a veryimportant tracer for the molecular gas.

M. Luhman and D. Jaffe have compared large-scale emsion from H2, CO, and C

1 to the far-infrared emission fromdust toward four clouds. The H2 emission is excited by ul-traviolet light and extends beyond the boundaries of theemission. Over the entire cloud, there is a significant colation between the emission from H2 and from dust.

M. Miesch ~University of Colorado! and J. Scalo havecompleted a study of the one-point probability distributioncentral radial velocities in star-forming gas using the denssampled Bell Labs CO data for a number of molecu

nreosthtu-lyetoo

ee

ir-C-etec

or-

adr oage

till

eatHlueeaaticgnth

hvhavee

om-thersks,,d

xy

iftrstneeaxy

thehetra60ipsuc-fiedth,

-

on

um.ed,AL

hism-theonh

ingfert

ofmi-s inedde-itsor-the

a-e


clouds with active star formation. The results show stroevidence for non-Gaussian velocity distributions in somegions, with the tails of the distributions being nearly expnential. Although they examined a number of possible phycal explanations, none of them seem to explainexponential nature of the tails. Work using this datasecontinuing. They have found that the probability distribtions of linewidths appear uniformly exponential or possiblognormal, an unexpected and unexplained result. Interprtions in terms of physical mechanisms are underway in claboration with groups performing numerical simulationscoupled star formation-hydrodynamics.

3.3.5 Extragalactic:

G.F. Benedict, in collaboration with B.J. Smith~IPAC!and J. Kenney~Yale!, has obtained, reduced, and analyzCO interferometry of NGC 4314. These data were obtainat Owens Valley Radio Observatory. These CO~1–0! inter-ferometer data provide 2.3932.29 spatial resolution and 13km s21 velocity resolution. The data reveal a clumpy ccumnuclear ring of gas. They also find a central peak ofwithin 29 of the optical center. Deviations from circular motion are seen where the dust lanes along the leading edgthe primary stellar bar intersect the nuclear ring, consiswith gas inflow along the bar. This is the clearest evidenfor inflow along a stellar bar observed in any galaxy. Hamaps of this galaxy show bright HII regions near the endsthis inflow region, perhaps indicating triggering of star fomation by the inflow.

G. Shields, R. Dufour~Rice University!, D. Garnett~Uni-versity of Minnesota!, and several collaborators completedstudy of silicon abundances in dwarf irregular galaxies, fining that silicon is not depleted by more than about a factotwo by dust formation. Si/O remains fairly constant21.5960.07 over an oxygen abundance ran21.6, logO/H,23.4.

G. Shields completed the second phase of a study ofchemical abundances of Virgo spiral galaxies with E. Skman ~University of Minnesota!, R. Kennicutt~University ofArizona!, and D. Zaritsky~UCSC!. New spectrophotometricobservations of HII regions were combined with earlier msurements to study the interstellar oxygen abundances indisks of nine Virgo spirals. The results show that thedeficient spirals closest to the cluster core have O/H va;0.5 dex higher than in comparable field spirals, wherthe spirals in the outskirts of the Virgo cluster, with normHI contents, have normal abundances. Simple theoremodels of the chemical evolution of the Virgo galaxies sugests that a cutoff of infall of primordial gas several billioyears ago in the Virgo spirals could account for much ofeffect observed.

I. Jo”rgensen, M. Franx~Kapteyn Institute, Holland!, andP. Kjæ rgaard~Copenhagen University, Denmark! have stud-ied the Fundamental Plane~FP! for a large sample of lowredshift elliptical and lenticular galaxies. The FP is a tigrelation between effective radius, surface brightness, andlocity dispersion for the galaxies. The existence of the FPimplications for galaxy formation and evolution. They hafound that the FP is affected by both the cluster environm

g--i-eis

a-l-f

dd

O

ofnte

f

-ft

he-

-heIsslal-

e

te-s

nt

and by variations in mean ages and metal content. This cplicates the use of the FP as a distance indicator. To furunderstand the effects of age, metal content, and diJo”rgensen and B. Milvang-Jensen~Copenhagen UniversityDenmark! are investigating the FP for a magnitude-limitesample of galaxies in the Hydra cluster.

I. Jo”rgensen, M. Franx~Kapteyn Institute!, and J. Hjorth~Cambridge, UK! have obtained observations of two galaclusters atz 5 0.2, which will allow investigation of theseclusters in similar detail as previously done for low redshclusters. The observations will make it possible for the fitime to establish the FP for high redshift clusters. Thus, omay study galaxy evolution using this tight relation. In thcourse of these observations a previously unknown galcluster was discovered at a redshift of 0.7.

M. Brotherton obtained moderate-resolution spectra ofHb–@OIII # l5007 region for 41 radio-loud quasars using tLCS on McDonald Observatory’s 2.7-m telescope. Specfrom the literature were also used to form a data set ofradio-loud quasars in order to investigate relationshamong quasars’ broad- and narrow-line profiles, radio strtures, and X-ray properties. Statistical analyses identiseveral strong, related trends: the FWHM, equivalent widand degree of redward asymmetry of Hb increase with de-creasing radio core dominance~an orientation indicator!,whereas the FWHM of@OIII # l5007 increases with luminosity andaox .

B. Wills and D. Hines~Steward Observatory! continuedpolarimetric investigations of the Lowet al.sample of IRASQSOs. Using spectropolarimetry of the Broad AbsorptiLine ~BAL ! QSO IRAS 0759816508, they showed it hadunpolarized broad emission lines and a polarized continuThe continuum consists of two components: an unpolarizreddened continuum that passes through low-ionization B~NaI! gas, and a polarized~scattered! continuum that is muchless reddened and is not absorbed by the BAL gas. Tprovides direct evidence that the BAL gas does not copletely cover the QSO continuum source, consistent withpresence of BAL gas in all QSOs with the BAL phenomenbeing simply a line-of-sight effect. With S. Young, J. Houg~University of Hertfordshire!, and collaborators, B. Wills dis-covered and investigated scattered light polarization arisfrom buried QSOs in a sample of warm infrared and Sey2 galaxies.

B. Wills and M. Brotherton investigated a different waymeasuring the dominance of a compact radio core in lunous quasars, using the rest-frame ratio of flux densitiethe radio-core to that in the optical continuum. They showthat this measure correlates well with orientation anglerived from observations of superluminal motion and limon inverse-Compton scattered X-ray flux. The good anticrelation between the new core-dominance measure andwidth of the broad Hb emission line suggests that orienttion significantly affects our view of the broad emission linregion.

The HST team~B. Wills, D. Wills, K. Thompson, M.Brotherton; J. Baldwin~CTIO!; H. Netzer~Tel Aviv Univer-sity!; G. Ferland~University of Kentucky!; I Browne ~Uni-versity of Manchester!; and R. Carswell~Institute of As-

jef

art 6o

anadtOtsincw

ora

etheiftgethes

eals o

se

ructeurte

za

iget treticcthriethlaLyzeut

fof

f aicsicsnr-nsof

e-r indardes

atrnelvenichey,om-—-sorng

ach-theousnewre-M.

-ge-iumr

-

sedonicereo-hatanun-is

as-yonnican-

648 ANNUAL REPORT

tronomy, Cambridge University!! have now completedquasi-simultaneous spectroscopy using HST’s faint-obspectrograph in the ultraviolet and ground-based spectrathe optical and infrared, for a sample of radio-loud quasUsing archival HST spectra, the sample contains abouobjects. Reduction of the thousands of spectra are almcomplete, as well as new VLA radio maps. Clear, importtrends among continuum and emission line shapes, rcore-dominance, and radio loudness are emerging withinsample and by comparison with, e.g., radio-quiet QSNetzeret al.show that reddening intrinsic to the QSO affecboth emission lines and continuum, and possibly the lwings more than their cores. In conjunction with this spetrophotometry, ground-based photometric monitoring shotrends of flux variability with luminosity.

G. Hill studied the rest-frame optical and UV spectrahigh-redshift quasars, redshifted in to infrared, in collabotion with R. Elston~CTIO! and K. Thompson.J, H, andKband spectra were obtained with the cryogenic spectromat the KPNO 4-m and with the IRS Spectrometer atCTIO 4-m. Rest-frame optical FeII emission line complexnear H-beta and MgII were detected in QSOs with redshup to z 5 4.8, confirming their earlier result and indicatinthat the nuclear environment of QSOs was highly enricheven at a very early epoch. Observations of objects athighest redshift can constrain the geometry of the universiron takes;1 Gyr to enrich to above solar abundance. Thedata indicate a low value ofq0 .

G. Hill continued the Texas Large-Scale Structure Surv~TLSS! using the Prime Focus Camera on the McDon0.76-m reflector. The aim of the survey is to select clustergalaxies from a 100 sq. deg. area with redshifts out toz 50.5, usingUBVRIphotometry. This project shares the dataof the Texas Deep Sky Survey~TDSS! of C. Claver, Hill, andP. MacQueen. Spectroscopic redshifts of clusters in thesulting catalog will provide a map of the largest-scale strture in the universe, using clusters rather than galaxies astracers. Claver, I. Jo”rgensen, D. Cornell, and F. Ma werinvolved in obtaining data for the TDSS/TLSS, and the crent area coverage stands at about 25 sq. deg., in spirelatively poor weather.

3.3.6 Theory:

G. Shields and L. Wobus continued work on the polarition of thermal emission from an accretion disk aroundsupermassive black hole in a quasar. Preliminary resultsdicate that the polarization of the disk continuum chanlittle across the Lyman edge and can remain significaninfrared wavelengths. This result differs from previoussults because the current work uses a model for the verdensity profile in the disk. The photospheric density is mulower than the midplane density, which had been used inearlier work, and the lower density causes electron scatteto remain the dominant opacity source over a wider rangwavelength. Shields began a theoretical investigation oforigin of the recently observed abrupt increase of the poization of QSO continua at wavelengths shorter than theman edge. He is considering a model in which the polaricontinuum component is emitted by an axial jet moving o

ctors.0sttiohes.

e-s

f-

teress

dease

ydf

t

e--he

-of

-an-so-alhengofer--d-

ward at speeds;0.3c, explaining the observed blueshift othe polarization rise relative to the expected wavelengththe Lyman edge.

P. Shapiro and H. Martel continued their development onew and improved version of the numerical gas dynammethod known as Smoothed Particles Hydrodynam~SPH!, with application to cosmology. As a Lagrangiamethod, SPH is well-suited to the simulation of galaxy fomation by the growth of cosmological density fluctuatiosince it uses particles which move with the flow as centersinterpolation which replace the fixed grid points of finitdifference codes, thereby increasing its resolving powehigh-density regions as density contrasts arise. The stanversion of SPH, however, suffers from two deficienciwhich are particularly acute in cosmology simulations:~1!the smoothing, or interpolation, of particle data, which isthe heart of the method, uses an isotropic interpolation kewhich is parametrized by a scalar smoothing length, ethough the gravitational collapse and shock waves whdominate the flows involve highly anisotropic volumchanges; and~2! shocks are handled by artificial viscositwhich causes widespread, spurious viscous heating of cpressing regions far from any shocks. The new methodAdaptive SPH~ASPH! — solves these problems by introducing an anisotropic interpolation kernel and a tensmoothing length which automatically adjust the resolvipower in time, in space, and indirection by tracking themean particle spacing along different directions around eparticle in the flow. In addition, shock-tracking is accomplished using the tensor smoothing lengths to predictoccurrence of density caustics and thereby to restrict vischeating to gas encountering a shock. As a result, theASPH method has at least an order of magnitude bettersolving power than standard SPH. Collaborators includeOwen~Ohio State University! and J. Villumsen~Max PlanckInstitute for Theoretical Astrophysics, Munich, Germany!.

P. Shapiro, H. Martel, A. Valinia~Physics Department!,and J. Villumsen~MPITA! applied their new ASPH numerical gas dynamics method to simulate the formation of larscale structure and the evolution of the intergalactic med~IGM! in cosmology models including Cold Dark Matte~CDM!, Cold-plus-Hot Dark Matter~CHDM!, and Hot DarkMatter ~HDM!, with high resolution in 2D. Their results indicate that dense regions tend to be anti-biased~gas concen-trates less tightly than does dark matter!. Observed X-raysurface brightness profiles of galaxy clusters have been urecently to measure the cluster total mass and the barygas fraction, by assuming the cluster is an isothermal sphin hydrostatic equilibrium. This has led to claims of a scalled ‘‘baryon catastrophe,’’ since the results indicate tthe cluster baryon mass fraction is significantly higher ththe mean value allowed by Big Bang nucleosynthesis abdance constraints if the total universal mean densityenough to make the Universe flat. Shapiroet al. have usedtheir simulations of flat models of cosmology to test thesumptions underlying the analysis which leads to the barcatastrophe. Their results confirm that the high baryomass fraction inside clusters found by X-ray observers c

,

oe

Mauasoniveeadbleec

Idun

thonth

thheraMhiealaldllereothofHGfraee

hi.-atiow

eaonscee

lf-ynt.ady-liedvedtos.l-fakesas,sityerse

-etheionve-

ra-gper-m-

fithmo-eu-edon-hee orofdy-ft-ent.oust.nofel-res-lawE.entsIa

alena

sionpar-anthat

c-ere


not be explained by flat universe models like CDM, CHDMand HDM.

P. Shapiro has continued his study of the re-ionizationthe intergalactic medium~IGM! and quasar absorption linclouds~QALCs!. With M. Giroux ~University of Colorado!,he modeled the ionization and thermal history of the IGnumerically, by a space-averaged approach which takescount of the ionization and heating due to photons from qsars and stars and bulk heating by hydrodynamical procesradiative and Compton cooling, cosmological expansinon-equilibrium ionization and recombination, and radiattransfer, including the continuum opacity of the observQALCs. Their results include predictions of widespremetal production prior to redshift 3 if stars are responsifor producing the metagalactic UV background and the HLyman alpha resonance absorption troughs in quasar spat high redshift~HeII Gunn-Peterson effect!. Recently, HSTand the Hopkins UV Telescope~HUT! detected such HeILyman alpha absorption in quasar spectra at redshift 3either to unresolved HeII lines associated with low-columdensity QALCs or to the diffuse IGM or both. Together wiresults like those of Giroux and Shapiro, these detecticonstrain the nature of the IGM and the QALCs andorigin of the metagalactic UV radiation background.

P. Shapiro and M. Giroux considered the feedback onIGM and on the rate of formation of new objects out of tIGM due to the ionizing energy released by the first genetion of bound objects to form by condensing out of the IGThey demonstrated that, if energy is released at a rateenough to re-ionize the IGM, this reheats and raises the Jmass of the uncollapsed IGM, which suppresses and dethe growth of the collapsed fraction. In a model like the CoDark Matter ~CDM! model in a flat universe, the maximaefficiency for energy release associated with stellar nucsynthesis is enough to re-ionize the IGM as early as ashift of about 50. In order to investigate the importancethe feedback effect of this re-ionization and reheating ofIGM on the rate of formation of galaxies and QALCs outthe IGM, Shapiro and H. Martel have applied their ASPmethod to simulate the gas dynamical response of the Ito such reheating and the consequences for the rate ofmation of galaxy-sized and subgalactic gas clouds. Theirsults indicate that the observed amount of baryonic malready formed into QALCs by redshift 3 is too high to bconsistent with predictions of the CHDM model, while thCDM model is consistent if either photoheatingalone re-heats the IGM or if explosive heating occurs as well, but theating is accompanied by very efficient radiative cooling

R. Benjamin~University of Texas and University of Minnesota! and P. Shapiro continued their modeling of hot gwhich cools radiatively in the Galactic halo as in the Galacfountain model. Their calculations of a steady-state, 1D flof gas cooling from close to 106K to below 104K, includingnon-equilibrium ionization, radiative cooling and radiativtransfer, make detailed predictions for comparison with Glactic halo ISM observations. They show that UV emissiand absorption lines observed from highly ionized specieour Galactic halo by IUE, HST, and various other spaborne detectors, for example, can be self-consistently

f

c--es,,

d

eIItra

e

se

e

-.ghnsys

o-d-fe

Mor-e-ss

s

sc

-

in-x-

plained by such a Galactic fountain flow, when the seillumination of the cooling gas by the radiation emitted bthe hotter part of the flow is properly taken into accouThese calculations have been generalized to describe stestate, radiative MHD shocks. They have also been appsuccessfully to predict and explain the metal lines obserin quasar Lyman-limit absorption-line systems, believedoriginate in galactic halos over a range of earlier redshift

A. Valinia, P. Shapiro, H. Martel, E. Vishniac, and J. Vilumsen~MPITA! have studied the gravitational instability ocosmological pancakes. They have modeled these pancas 1D, plane-wave density fluctuations in a collisionless gwhich collapse into sheets along the planes of each denmaximum, and have subjected the pancakes to transvperturbations which are either symmetric~density! or anti-symmetric ~bending! modes. They have shown by highresolution 2D, gravitational N-body simulations by thParticle-Mesh~PM! method that pancakes are unstable toformation of clumps for a substantial range of perturbatwavelengths from roughly equal to the pancake mode walength to smaller wavelengths.

The antisymmetric modes also lead to significant genetion of vorticity. Numerical gas dynamical simulations usinthe new ASPH method developed here have also beenformed, revealing similar instabilities when a gaseous coponent is included.

H. Martel studied analytically the non-linear growth ocosmological perturbations for flat cosmological models wa uniform component that can be either a non-zero coslogical constant, domain walls, cosmic strings, massive ntrinos, or radiation. The semi-analytical solutions obtainshow that the relationship between the present density ctrast and peculiar velocity field is a sensitive function of tdensity parameter, but it is very insensitive to the presencnature of the uniform component. This rules out any hopedetermining the presence of a uniform component by stuing the dynamics of the local universe. Only redshidependent tests might reveal the presence of this componThis generalizes the results obtained previously by variauthors for models with a non-zero cosmological constan

A. Khokhlov proposed a scaling law for buoyancy-driveturbulent pre-mixed flames and confirmed it by meansthree-dimensional simulations. This regime of burning is revant both for supernovae and for lean hydrocarbon tertrial flames in vertical tubes. For such flames, the scalinghas been recently confirmed experimentally. Khokhlov,Oran, and C. Wheeler proposed that terrestrial experimcan be used to calibrate thermonuclear models of Typesupernova explosions.

A. Khokhlov also performed the first three-dimensionsimulations of the explosion of a massive carbon oxygwhite dwarf as a Type Ia supernova. The results showsubstantial decrease of the burning rate due to expaneffects and sphericity. The results were consistent with atial burning of a central portion of the star which leads toexpansion and recontraction. A detonation may occur atpoint.

Three-dimensional simulations of relativistic tidal interations of a star with a supermassive Kerr black hole w

etAe-poaatherteara

aorno

tu-, hthireha

g

cti-amaf-

D

inxlieioi

nac

iniol tneed.l-el

w

e-oleiskhar-thatavetohotis

acks..

tion-ir-

atec-ver

heirinlo-icalteden--ityughter-eda-iblevednalrceud

elsonab-pa-ro-useelynsande-tionellshesultbylo-el-uldfor-n

650 ANNUAL REPORT

carried out for the regimes of weak interaction to compldisruption to ultra-strong compression of the star byKhokhlov, P. Deiner, and I. Novikov. A general relation btween the tidal tensor and the energy and momentum deited into a star has been found which covers both westrong, relativistic, and non-relativistic regimes. For ultrclose encounters, material is ejected from the vicinity ofblack hole in a large solid angle and can interact with intstellar matter effectively. Sgr A East in the Galactic Cenmay be a result of the disruption of a solar-like star byblack hole of 106 solar masses at a distance of seveSchwarzschild radii.

The development of the multi-energy, multi-dimensionneutrino transport and fluid dynamics model, ALLA-C, fType II supernova explosions was completed by I. Lichtestadt and A. Khokhlov. Preliminary results show a phaseturbulent boiling before the explosion.

J. Boisseau completed his Ph.D. dissertation on the sof the stability of carbon detonation fronts with twodimensional models. In analogy to terrestrial detonationsfound that the detonation front fragments on the scale ofpost-shock carbon burning length into unburned pockets wa size characterized by the equation of state and nucleaaction dynamics. This effect increases with decreasing dsity and may dominate for the low-density detonations tare thought to characterize delayed detonation modelsType Ia supernovae. This may affect the detonation propation and the resultant distribution of burning products.

J. Wang has continued to construct a computer codepable of simulating the principle features of muldimensional gravitational collapse models of supernovSuch a code will allow a study of a broader range of paraeter space than full multi-dimensional models. Wang himplemented a ‘‘two-stream’’ formalism to simulate the efects of convection and overshoot.

C. Wheeler, Research Assistant R. Gearhart, andSwartz~Marshall Space Flight Center! are re-examining theproduction of carbon monoxide in SN 1987A. They are usthe distribution of composition, ionization, and ionizing flufrom complete radiative transfer models in contrast to earone-zone models. They find that the CO velocity distributis better reproduced in models in which the compositionsubstantially macroscopically unmixed.

M. Kusunose worked on hot accretion disks with nothermal particles and on particle acceleration around blholes. With S. Mineshige~Kyoto University!, he studied thestructure of accretion disks around black holes and examthe condition where electron–positron annihilation emissis observed from accretion disks. He applied this modeGalactic black hole candidates such as Cyg X-1 aGX339-4 to determine model parameters. With this modhe further examined a mechanism to explain the two diffent states of X-ray emission from Galactic black hole candates, i.e., the low state and the high state. Kusunose, Hand E. Liang~Rice University! constructed a model to caculate particle acceleration and radiation transfer sconsistently, by which gamma-ray spectra from non-thermplasmas near black holes are calculated and comparedobservations.

e.

s-k,-e-r

l

l

-f

dy

eethre-n-tofa-

a-

e.-s

.

g

rns

-k

ednodl,r-i-Li,

f-alith

S.-W. Kim completed his dissertation research on timdependent, irradiated accretion disk models for black hX-ray transients. He found that self-shadowing by the dcan lead to phenomena like the secondary reflare which cacterizes many black hole candidate systems. Modelsreproduce the observed light curves reasonably well hvery little irradiation of the companion. The models tendhave a central portion near the black hole that remainsand ionized even in quiescence, when most of the diskpredicted to be cold, and an accretion rate down the blhole that is in approximate accord with X-ray observation

M. Moscoso has continued work in collaboration with MKusunose to develop a code that can compute the radiainduced pair wind expected to be driven from a padominated corona around a black hole.

M. Della Valle, S. Benetti~Asiago Observatory!, and C.Wheeler are writing a paper on the black hole candidX-ray transient Nova Vel 1993. This system is only the seond known to have experienced multiple outbursts otimes of hundreds of days after the main outburst.

P. Kornreich and J. Scalo completed one phase of tinvestigation of the production of vortical internal motionsinterstellar clouds by shock waves produced by stellar expsions and winds. Analytical methods, supported by numersimulations, have been used to study the vorticity generaas an initially planar shock propagates through irregular dsity and velocity fields. A general analytic result for the immediate post-shock vorticity and the downstream vorticwas derived. It was found that the passage of a shock throa cloud with a density gradient should generate strong innal vortical motions, which should eventually be convertby vortical-compressible interactions into density fluctutions. These calculations suggest a physically plausmechanism for sustaining the supersonic linewidths obserin interstellar clouds, provide a means of generating interdensity and velocity structure in clouds without any souof instabilities, and are also relevant to observations of clorotation and initial protostellar angular momentum.

D. Chappell and J. Scalo continued their study of modfor collective spatial and temporal behavior of star formatiin galaxies. The models operate on a lattice and includestracted implementations of threshold star formation, progating star formation, fluid advection, heating by stellar pcesses, radiative cooling, and turbulent dissipation. Becaof its abstracted nature, the model calculations are extremfast compared to conventional hydrodynamic simulatioand allow us to examine a wide range of parameter spaceinitial conditions. Most of the work this year has been dvoted to a model that simulates the physics of the interacbetween non-linear fluid advection and expanding shdriven by threshold star formation. Besides the ability of tmodels to generate extremely interesting structure as a reof advection alone interacting with the motions drivenstar formation, a particularly interesting result is that the gbal star formation rate becomes ‘‘bursty’’ if the adopted stlar initial mass function is steep enough. The models shoeventually provide an observational test for whether starmation primarily excites or inhibits further star formatio

on

-lat beytoblisoaqu

olidic

thchlyreiopeareynul

c, Athc-f alseGraewratea1,-iostar aetet

eiad

lativ-m-

RSon-inglarthech-m,esex-d itsnicety.nterer-on-ion,meng-

ngare.g.,r-Itr tonce-ingto asea

s inn-gnchtiv-isheatticsngovedre-

ldangup-hasble,anl-ar-


and whether burst/lull behavior should be expected in ninteracting galaxies.

E. Vazquez-Semadeni~UNAM ! and J. Scalo are collaborating on a summary of observational and numerical simution evidence that interstellar clouds may for the most partransient entities that are usually far from equilibrium. Thcalculated the probability distribution for interstellar gasbe subjected to shocks from supernovae and winds/bubCoupled with a study of the numerical simulations, thshows that clouds are probably disturbed by external shwaves and advective interactions with larger scales whichon timescales smaller than the time required to attain elibrium. These results suggest that the entrenched viewclouds in a state of virial equilibrium, and the conceptexternal confinement by turbulent pressure, may be inva

J. Scalo began an investigation of a range of theoretmodels for the stellar initial mass function~IMF!, with anemphasis on models that couple the IMF to the nature ofvelocity field in the clouds from which the stars form, suas velocity fields dominated by stellar winds, externaldriven shock waves, or some sort of more traditional ‘‘tubulence.’’ The properties of other models are also beingamined. The goal is to understand how different assumptabout the dominant physics affect the predicted IMF, escially on the issue of universality, and to question whethmeaningful choices between theories can presently be mgiven that the range of possible physical scenarios is so gand the observational constraints so weak. The availabilitdata from HST on deep star counts in various environmeand from accumulating spectroscopy of massive star poptions plays a key role in answering these questions.

3.3.7 Laser Ranging:

Lunar and artificial satellite laser ranging, with ProjeDirector P. Shelus and staff members R. Ricklefs, J. RiesWhipple, and J. Wiant, continues under the support ofNational Aeronautics and Space Administration. The MDonald Laser Ranging Station~MLRS! is a fundamental station in the world-wide laser ranging network. It consists o0.76-m reflecting telescope and a very short pufrequency-doubled, 532-nm-wavelength, neodymium-YAlaser, with associated computer, electronic, and timing haware. The station is located on Mt. Fowlkes, to the northeof Mt. Locke, and shares the mountaintop with the nHobby-Eberly Telescope. With a two-crew observing opetion, laser ranging is carried on to a host of artificial satelli~Fizeau, ERS-1, ERS-2, Starlette, Stella, Meteor-3, AjisTOPEX/Poseidon, LAGEOS-1, LAGEOS-2, Etalon-Etalon-2, GPS-35, GPS-36, GLONASS, and Meteosat P!plus the moon. The MLRS is the only lunar-capable statin the United States and only one of two lunar-capabletions in the entire world. By measuring the time it takes folaser pulse to leave a ground station, bounce off a targreflector array, and return to the ground station, one can msure very precisely the distance between the station andreflector array. Comparing a series of measurements~almost30 years of lunar laser ranging observations have now baccumulated, together with more than 10 years of artificsatellite data!, scientific results are obtained in four broa

-

-e

es.

ckcti-off.al

e

--x-nse-rde,atoftsa-

t.e-

,

d-st

-si,

2n-

eda-he

enl

areas: solar system ephemeris development, general reity and gravitational physics, lunar science, and geodynaics.

Laser ranging observations were obtained with the MLat record-setting levels for the sixth straight year as persnel cooperated with colleagues around the world, makmaximum use of the data type in earth, moon, and sosystem-related dynamics. For the first time ever withMLRS, the group is reaching lunar data densities approaing those obtained in the mid-1970s with the 2.7-m systebut at levels of accuracy and precision almost five timbetter. Principal research activity includes monitoring thechange of angular momentum between the solid earth anatmosphere, the principal geopotential terms, plate tectoactivity, tidal dissipation in the lunar orbit, the lunar frelibration, and the equivalence principle of general relativiIn a service capacity the project serves as Observing Ceand Analysis Center in the International Earth Rotation Svice, obtaining millisecond accuracy estimates of the cstant of precession and coefficients of nutation, polar motand Earth rotation. This constitutes the only near-real-tisource of this information that includes the lunar laser raing data type.

The MLRS Auto-Guiding and Imaging System~AGIS! isapproaching full integration in all facets of the laser rangioperation. The AGIS is an integrated hardware and softwsystem that accepts real-time video signals as input, ehighly magnified images of a small portion of the lunar suface, or stellar or artificial satellite point-source images.performs real-time image processing and allows a useselect among various levels and types of image enhament. Further, the AGIS produces raw and filtered trackerror signals that under user selection are communicatedcontrol computer for guiding control. At this time, most uof the AGIS is applied to the lunar effort, producingmarked increase in the volume of LLR data.

A second, improved Avalanche Photo-Diode~APD! wasdelivered to the MLRS this summer by German colleagueWettzell in the effort to replace the MLRS Varian high quatum efficiency photomultiplier tube in lunar laser ranginoperations. Such an APD detector, now in use at the FreLLR station, has exhibited a significant increase in sensiity and improved accuracy and precision. A similar deviceused for artificial satellite laser ranging operations in tUnited Kingdom and elsewhere in Europe. The first unit ththe team received exhibited intolerable noise characterisand marginal sensitivity when installed in the MLRS rangisystem. The second unit appears to possess much imprnoise characteristics and greater sensitivity. The first testsults on the moon have been very encouraging.

Finally, the team has replaced the MLRS’s 15-year-oData General NOVA control computer system withLynxOS-based, X-windows, real-time Unix system runnion PC hardware. This has been coordinated with similargrades at other NASA- based laser ranging systems. Itcreated a system having highly compatible, transportaand transferable hardware and software architecture inopen-systems~POSIX! environment. The approach has alowed a maximum amount of software portability and sh

re

mG-n-rin

(ta

oesus

na

nsosndedvir eTofaibn

13caeal.botheoCem

c

coueae

ercttrinit

ostthet ofned.an-

e-ng

4,ind

J.,

act

e

e,n-andinecal

.,e-. &n-

b-.

e

b-.

e,anic

n-hi--s,

d

652 ANNUAL REPORT

ing. All MLRS data, both lunar and artificial satellite, anow being obtained with this system.

3.3.8 Astrometry:

The Hubble Space Telescope Astrometry Science Teabased at the University of Texas. Local members includeBenedict~Deputy P.I.!, R. Duncombe~Aerospace Engineering!, W. Jefferys~P.I.!, B. McArthur, P. Hemenway, E. Nela~STScI!, P. Shelus, and D. Story~Goddard Spaceflight Center!. The team continued reducing and analyzing data beaon planet searches, HIPPARCOS-quasar reference framein, and parallaxes of astrophysically interesting objectsdCephei, RR Lyrae, Feige 24, planetary nebulae central sthe Hyades, low-mass M-dwarfs!. All data are obtained withFine Guidance Sensor 3 aboard HST. They continue totain milliarcsecond or better precision for parallax valuMuch future science will come from nearly simultaneotransfer scan and position mode astrometry with FGS 3obtain precise orbits, parallaxes, and masses for close bistars difficult or impossible to study from the ground.

This year the team carried out two remaining calibratiolateral color and cross-filter. Shelus’ analysis of the mrecent HST lateral color observations was finished withsubstantive effect being detected. A parallel and totally inpendent examination of these data by Benedict also failefind any statistically significant effect. Given the strong edence from past ground-based testing that a lateral colofect does exist, the team continues to study these data.information will be crucial to FGS astrometry, muchwhich is carried out on extremely red stars. Hemenwheaded up a successful effort to secure a cross-filter caltion. Observations were obtained to calibrate the positiooffset between the ‘‘clear’’ and ‘‘neutral density’’ filters inFGS 3. The success of this calibration insures amagnitude dynamic range for HST FGS astrometry. Applition of the derived calibration~rms at the 1 mas level for thcorrections! to the Hipparcos link data reduced the residuof the data taken with the ND filter from 8 mas to 2 mas

P. Shelus and A. Whipple continue their astrometric oservations of faint solar system objects. This effort has ncompletely moved from the photographic process, usingCassegrain Camera on the Otto Struve 2.1-m reflecting tscope at Mt. Locke, to a CCD using the Prime Focus Crector~PFC! on the McDonald 0.76-m reflector. The f/3 PFis ideal for astrometric observations of faint solar systobjects. The detector is a Loral-Fairchild 204832048 chipthat covers a 46-arcmin3 46-arcmin field with 1.35-arcsepixels. This instrument is capable of reachingR522, withmore than 3 sigma significance on stellar objects, inadded integrations. Whipple and R. Whited have continto develop a software system within IRAF and ICEX thperforms routine, near-real-time processing of CCD framtaken with the PFC~or any other CCD!, identifies star fieldsand solar system objects within the fields, digitally detmines the centers and intensities for all identified objewithin the fields, and then processes the measures to obastrometric positions and magnitudes. The total astromesystem is fully functional, and excellent results are beobtained. Observations were made of the satellites of Jup

is.

gtie-

rs,

b-.

tory

,to-to-f-he

yra-al

--

s

-wele-r-

-dts

-tsainicger,

Saturn, and Neptune, and of many selected asteroids. Mof these objects have, been grossly underobserved inpast, and orbit refinements require that a continuous seprecise and accurate positional observations be maintaiPositions of all interesting objects are determined in a stdard reference frame.

PUBLICATIONSAchtermann, J.M. & Lacy, J.H. 1995, ‘‘Structure and Kin

matics Within the Starburst Nucleus of M82: Searchifor a Bar,’’ ApJ,439, 163

Armosky, B.J., Sneden, C., Langer, G.E. & Kraft, R.P. 199‘‘Abundance Trends Among Neutron Capture ElementsGiants of Globular Clusters M5, M3, M13, M92, anM15,’’ AJ, 108, 1364

Atreya, S.K., Edgington, S.G., Trafton, L.M., Caldwell, J.Noll K.S., & Weaver, H.A. 1995, ‘‘Abundances of NH3and CS2 in the Jovian Stratosphere Following the Impof Comet Shoemaker–Levy 9,’’ GRL,22, 1625

Barnes, T.G. & Moffett, T.J., 1995, ‘‘Uncertainties in thGalactic Cepheid Distance Scale,’’ inAstrophysical Appli-cations of Stellar Pulsation, ASP Conference Series83,363

Benedict, G.F., McArthur, B., Nelan, E., Story, D., WhipplA.L., Wang, Q., Jefferys, W.H., Duncombe, R., Hemeway, P.D., Shelus, P.J., Franz, O.G., Fredrick, L.W. & vAltena, W.F. 1995, ‘‘The Search for Planets ArounProxima Centauri Using the Hubble Space Telescope FGuidance Sensor ##3: A Progress Report,’’ Astrophysiand Space Sciences223, 137

Benedict, G.F., Jefferys, W.H., McArthur, B., Nelan, EWhipple, A.L., Wang, Q., Story, D., Duncombe, R., Hmenway, P.D., Shelus, P.J., Franz, O.G., Fredrick, L.Wvan Altena, W.F. 1995, ‘‘Hubble Space Telescope: A Geerator of Sub-Milliarcsecond Precision Parallaxes,’’ inAs-tronomical and Astrophysical Objectives of SuMilliarcsecond Optical Astrometry, eds. E. Hoeg and P.KSeidelmann~Kluwer Academic Publishers, Dordrecht!, p.89

Benedict, G.F., McGraw, J.T. & Hess, T.R. 1995, ‘‘RelativAstrometry with Imaging Transit Telescopes,’’ inAstro-nomical and Astrophysical Objectives of SuMilliarcsecond Optical Astrometry, eds. E. Hoeg and P.KSeidelmann~Kluwer Academic Publishers, Dordrecht!

Beuermann, K., Reinsch, K., Barwig, H., Burwitz, V., dMartino, D., Mantel, K.-H., Pakull, M.W., RobinsonE.L., Schwope, A.D., Thomas, H.-C., Trumper, J., vTeeseling, A. & Zhang, E. 1995, ‘‘Discovery of a GalactSupersoft Binary X-Ray Source,’’ A&J,294, L1

Breger, M., Handler, G., Nather, R.E., Winget, D.E., Kleiman, S.J., Sullivan, D.J., Zhi-Ping, L., Solheim, J.-E., SYang, J., Zong-Li, L., Wood, M.A., Watson, T.K., Dziembowski, W.A., Serkowitsch, E., Mendelson, H., ClemenJ.C., Krzesinski, J. & Pajdosz, G. 1995, ‘‘Thed Scuti StarFG Vir. I. Multiple Pulsation Frequencies Determinewith a Combined DSN/WET Campaign,’’ A&J,297, 473

Briley, M.M., Smith, V.V. & Lambert, D.L. 1994, ‘‘CarbonIsotope Ratios Among M71 Bright Red Giants,’’ ApJ424,L119

ll,n

ekith,5,del

e,’’

i,

tic

4nc

55

,

r-

5dpe

r2V.ric

la

f,

.Jc-

in

ni

ra

-

J,

.N

r-ue

&

S

h

on,e

G.

&-s,’’

&-theF.

yn-

r,rya-

nce

-

al

es

y,or,.-

an,-he,

f


Brown, M.E., Boudhez, A.H., Spinrad, H. & Johns-KruC.M. 1995, ‘‘Non-Detection of the OH Meinel System iComet P/Swift-Tuttle,’’ A&A, 301, L1

Brandt, J.C., Heap, S.R., Beaver, E.A., Boggess, A., Carpter, K.G., Ebbets, D.C., Hutchings, J.B., Jura, M., Lecrone, D.S., Linsky, J.L., Maran, S.P., Savage, B.D., SmA.M., Trafton, L.M., Walter, F.M., Weymann, R.J., SnowM., Randall, C.E., Robinson, R. & Wahlgren G. 199‘‘An Atlas of Alpha Orionis Obtained with the GoddarHigh-Resolution Spectrograph on the Hubble Space Tscope,’’ AJ,109, 2706

Busso, M., Gallino, R., Lambert, D.L., Raiteri, C.M. &Smith, V.V. 1995, ‘‘Nucleosynthesis and Mixing on thAGB. II. Carbon and Barium Stars in the Galactic DiskApJ, 446, 775

Busso, M., Lambert, D.L., Beglio, L., Gallino, R., RaiterC.M. & Smith, V.V. 1995, ‘‘Nucleosynthesis and Mixingon the AGB. II. Carbon and Barium Stars in the GalacDisk,’’ ApJ, 446, 775

Choi, M., Evans, N.J. II, Gregersen, E.M. & Wang, Y. 199Proceedings of the Haystack Meeting, ASP ConfereSeries65, 167

Choi, M., Evans, N.J. II, Gregersen, E.M. & Wang, Y. 199‘‘Modeling Line Profiles of Protostellar Collapse in B33with the Monte Carlo Method,’’ ApJ,448, 742

Choi, M., Evans, N.J. II, Jaffe, D.T. & Walker, C.K. 1994‘‘Observation of@C1# Toward GL 2591 and W 28 A2 Mo-lecular Outflows,’’ ApJ,435, 734

Clark, B.E. 1995, ‘‘Spectral Mixing Models of S-Type Asteoids,’’ JGR,100, 14443

Clark, B.E., Bell, J.F., Fanale, F.P. & O’Connor, D.J. 199‘‘Results of the Seven-Color Asteroid Survey: InfrareSpectral Observations of 50-Km Size S-, K-, and M-TyAsteroids,’’ Icarus,113, 387

Clocchiatti, A., Brotherton, M., Harkness, R.P. & WheeleJ.C. 1994, ‘‘Supernova 1994I in NGC 5194,’’ IAUC 597

Clocchiatti, A., Wheeler, J.C., Barker, E.S., Filippenko, A.Matheson, T. & Leibert, J.W. 1995, ‘‘SpectrophotometStudy of SN 1993J at First Maximum Light,’’ ApJ,446,167

Cochran, A.L. 1995, ‘‘Spectroscopic Observations of SoSystem Objects: Pushing the Limits,’’ inNew Develop-ments in Array Technology and Applications, eds. A.G.Davis-Phillipset al. ~D. Riedel, Dordrecht!, p. 251

Cochran, A.L. & Trout A.P. 1994,‘‘The Gas Distribution oComet Halley and its Relation to the Nucleus RotationAJ, 108, 1471

Cochran, A.L., Whipple, A.L., MacQueen, P.J., Shelus, PWhited, R.W. & Claver, C.F. 1994, ‘‘Pre-Impact Charaterization of Comet Shoemaker–Levy 9,’’ Icarus,112, 528

Colome, C., DiFrancesco, J. & Harvey, P.M. 1994,Clouds, Cores, and Low-Mass Stars, Proceedings of the4th Haystack Meeting, eds. D. Clemens and R. BarvaiASP Conference Series62, 181

Colome, C. & Harvey, P.M. 1995, ‘‘The Distribution ofWarm Dust in the Star-Forming Region Cepheus A: Infred Constraints,’’ ApJ,449, 656

Colome, C., Harvey, P.M. & Lester, D.F. 1995, ‘‘High

n--,

e-

,e

,

,

,

,

r

’’

.,

s,

-

Resolution Far-Infrared Observations of DR 21,’’ Ap447, 236

Combi, M., Huang, B., Cochran, A., Fink, U. & Schulz, R1994, ‘‘Time-Dependent Analysis of Eights Days of CSpatial Profiles in Comet P/Halley,’’ ApJ,435, 870

Corwin, H.G, Buta, R.J. & de Vaucouleurs, G. 1994, ‘‘Corections and Additions to the Third Reference Catalogof Bright Galaxies,’’ AJ,108, 2128

Cowan, J.J., Burris, D.L., Sneden, C., Preston, G.W.McWilliam, A. 1995, ‘‘Evidence of ther -Process Early inthe History of the Galaxy: The Ultrametal-Poor Star C22892-052,’’ ApJ,439, L51

Crane, P., Lambert, D. & Scheffer, Y. 1995, ‘‘A Very HigResolution Survey of Interstellar CH and CH1,’’ ApJS,99, 107

De Jager, O.C., Meintjes, P.J., O’Donoghue, D. & RobinsE.L. 1994, ‘‘The Discovery of a Brake on the WhitDwarf in AE Aquarii,’’ MNRAS, 267, 577

Deliyannis, C.P., King, J.R., Boesgaard, A.M. & Ryan, S.1994, ‘‘Lithium in a Short-Period Tidally Locked Binaryof M67: Implications for Stellar Evolution, GalacticLithium Evolution, and Cosmology,’’ ApJL,434, L71

DiFrancesco, J., Evans, N.J. II, Harvey, P.M., Mundy, L.G.Butner, H.M. 1994, ‘‘Constraining Circumstellar Environments: Far-Infrared Observations of Herbig Ae/Be starApJ, 432, 710

DiFrancesco, J., Evans, N.J. II, Harvey, P.M., Mundy, L.G.Butner, H.M. 1995, inFrom Gas to Stars to Dust: Proceedings of the Airborne Astronomy Symposium onGalactic Ecosystem, eds. M. Haas, J. Davidson, and E.Erickson, ASP Conference Series73, 267

Dinerstein, H.L., Sneden, C. & Uglum, J. 1995, ‘‘A Surveof Planetary Nebulae at Na D: Evidence for Neutral Evelopes,’’ ApJ,447, 262

Dinerstein, H.L., Haas, M.R., Erickson, E.F., & WerneM.W. 1995, ‘‘Far-Infrared Emission Lines from PlanetaNebulae,’’ inAirborne Astronomy Symposium on the Glactic Ecosystem: From Gas to Stars to Dust,eds. M.R.Haas, J.A. Davidson, and E.F. Erickson, ASP ConfereSeries73, 365

Dinerstein, H.L. 1995, ‘‘Evidence for Neutral Matter in Planetary Nebulae,’’ inAsymmetrical Planetary Nebulae, eds.A. Harpaz and N. Soker, Annals of the Israel PhysicSociety,11, 152

Dinerstein, H.L. 1995, ‘‘Infrared Emission Lines as Probof Gaseous Nebulae,’’ inThe Analysis of Emission Lines,eds. R.E. Williams and M. Livio~Cambridge UniversityPress!, p. 134

Dolan, J.F., Boyd, P.T., Wolinski, K.G., Smith, P.S., ImpeC.D., Bless, R.C., Nelson, M.J., Percival, J.W., TaylM.J., Elliot, J.L., Robinson, E.L. & van Citters, G. W1994, ‘‘The Linear Polarization of 3C345 in the Ultraviolet,’’ ApJ, 432, 560

Edvardsson, B., Gustafsson, B., Johansson, S.G., KiselmD., Lambert, D.L., Nissen, P.E. & Gilmore, G. 1994, ‘‘Boron in the Extreme Population II Star HD140283 and tProduction of Light Elements in the Early Galaxy,’’A&A290, 176

Elston, R., Thompson, K.L. & Hill, G.J. 1994, ‘‘Detection o

sherl-

p

in

.As

f

r-ed

.r

ers,IIos

i-,’’

th

.,

o

e

,

iu,

he

ty

d

-n-

-

of8

dIaol-

en,.J.-

x-

of

y

tarsys-

0of

-in

0

st

E.,.,.,j-.,v-o-

he

or

.,.,

K.,.,.,ol-

654 ANNUAL REPORT

Strong Optical Fe II Emission inz.3 Quasars,’’ Nature,367, 250

Eracleous, M., Horne, K., Robinson, E.L., Zhang, E., MarT.R. & Wood, J. 1994, ‘‘Hubble Space Telescope Obsvations of the Cataclysmic Variable AE Aquarii: The Utraviolet Pulsar Revealed,’’ ApJ,433, 313

Evans, D.S. 1995, ‘‘The Surface-Brightness Technique Aplied to Cepheid Variables,’’ The Observatory,115, 205

Evans, N.J. II, Lacy, J.H., Carr, J.S. & Zhou, S. 1995,Circumstellar Matter, eds. G.D. Watt and P.M. Williams~Reidel, Dordrecht!, p. 181

Federman, S.R., Strom, C.J., Lambert, D.L., Cardelli, JSmith, V.V. & Joseph, C.L. 1994, ‘‘Chemical Transitionfor Interstellar C2 and CN in Cloud Envelopes,’’ApJ,424,772

Frolov, V., Khokhlov, A.M., Novikov, I.D. & Pethick, C.,1994 ‘‘Relativistic Tidal Interactions of a White Dwarwith a Massive Black Hole,’’ ApJ,432, 680

Gaffney, N.I., Lester, D.F. & Doppmann, G. 1995, ‘‘Measuing Stellar Kinematics in Galaxies with the Near-Infrar~2–0!12CO Absorption Bandhead,’’ PASP,107, 68

Garnett, D.R., Skillman, E.D., Dufour, R.J., Peimbert, MTorres-Peimbert, S., Shields, G.A., Terlevich, R. & Televich, E. 1995, ApJ,443, 64

Garnett, D.R., Dufour, R.J., Peimbert, M., Torres-PeimbS., Skillman, E.D., Terlevich, R., Terlevich, E. & ShieldG.A. 1995, ‘‘Si/O Abundance Ratios in Extragalactic HRegions from Hubble Space Telescope UV Spectrcopy,’’ ApJ, 449, L77

Giridhar, S., Rao, N.K. & Lambert, D.L. 1994, ‘‘The Chemcal Composition of the RV Tauri Variable IW CarinaeApJ, 437, 476

Goodrich, R.W., Veillieux, S. & Hill, G.J. 1994, ‘‘InfraredSpectroscopy of Seyfert 2 Galaxies: a View ThroughObscuring Torus,’’ ApJ,422, 521

Graf, U.U., Jaffe, D.T., Kim, E.J., Lacy, J.H., Ling, HMoore, J.T. & Rebeiz, G. 1994, Appl. Opt.,33, 96

Gratton, R.G. & Sneden, C., 1994 ‘‘Abundances of NeutrCapture Elements in Metal Poor Starts,’’ A&A,287, 927

Harvey, P.M., Lester, D.F., Colome´, C. & Smith, B. 1994‘‘G5.89-0.39: A Compact H II Region with a Very DensCircumstellar Dust Torus,’’ ApJ,433, 187

Harvey, P.M., Smith, B.J., Colome´, C., DiFrancesco, J.Lester, D.F. & Sill, D. 1995, inFrom Gas to Stars toDust: Proceedings of the Airborne Astronomy Symposon the Galactic Ecosystem, eds. M. Haas, J. Davidsonand E.F. Erickson, ASP Conference Series73, 251

Hatzes, A. 1995, ‘‘Spot and Chromospheric Activity on tRS CVN Star DM Ursae Majoris,’’ AJ,109, 350

Hatzes, A.P. & Cochran, W.D., 1994, ‘‘The Radial VelociVariation of the K Giantb Oph. I. The Detection of Low-Amplitude, Short-Period Pulsations,’’ ApJ,432, 763

Hellier, C. & Robinson, E.L. 1994, ‘‘PX Andromedae anthe SW Sex Phenomenon,’’ ApJL,431, L197

Hellier, C., Ringwald, F.A. & Robinson, E.L. 1994, ‘‘WXAri: A Low Inclination SW Sex Star,’’ A&A,289, 148

Hill, G.J. 1994, ‘‘An Infrared Test of AGN Unification Theories,’’ in Infrared Astronomy With Arrays: the Next Geeration, ed. I.S. McLean~Kluwer, Dordrecht!, p. 173.

,-

-

.,

,-

t,

-

e

n

m

Hill, G.J. 1995 ‘‘Science with the Hobby-Eberly Spectroscopic Survey Telescope,’’ inWide Field Spectroscopy,eds. S.J. Maddox and A. Aragon- Salamanca~World Sci-entific, Singapore!, p. 49

Hines, D.C. & Wills, B.J., 1995, ‘‘The Polarized Spectrumthe Fe II-Rich Broad Absorption Line QSO IRAS 075916508,’’ ApJ,448, 69

Hoflich, P., Khokhlov, A.M. & Wheeler, J.C. 1995, ‘‘DelayeDetonation Models for Normal and Subluminous TypeSupernovae: Absolute Brightness, Light Curves, and Mecule Formation,’’ ApJ,444, 831

Jaffe, D.T., Zhou, S., Howe, J.E., Herrmann, F., MaddS.C., Poglitsch, A., van der Werf, P.P. & Stacey, G1994, ‘‘Ultraviolet-Illuminated Molecular Cloud Boundaries: Extended@C II# 158-Micron Emission TowardL1630,’’ ApJ, 436, 203

Jefferys, W.H. 1995, ‘‘On p-Values and Chance,’’ J. Sci. Eplor., 9, 121

Johns, C.M. & Basri, G. 1995, ‘‘Hamilton Echelle SpectraYoung Stars. II. Time Series Analysis of Ha Variations,’’AJ, 109, 2800

Johns, C.M. & Basri, G. 1995, ‘‘The Line Profile Variabilitof SU Aur,’’ ApJ, 449, 341

Jo”rgensen, I., 1994 ‘‘Secondary photometric standard sfor the Thuan-Gunn and the Johnson-Kron-Cousins stems,’’ PASP,106, 967

Jo”rgensen, I. & Franx, M., 1994, ‘‘The Nature of E and SGalaxies: A Study of a Magnitude-Limited SampleGalaxies in the Coma Cluster,’’ ApJ,433, 553

Jo”rgensen, I., Franx, M. & Kjæ rgaard, P., 1995, ‘‘Multicolour CCD Surface Photometry for E and S0 Galaxies10 Clusters,’’ MNRAS,273, 1097

Jo”rgensen, I. & Franx, M., 1995, ‘‘The Nature of E and SGalaxies,’’ Astro. Lett. and Communications,31, 211

Kaiser, M.E. & Hill, G.J. 1994, ‘‘Near-Infrared Observationof 3C208.1,’’ in Infrared Astronomy With Arrays: the NexGeneration, ed. I.S. McLean~Kluwer, Dordrecht!, p. 135

Kawaler, S.D., O’Brien, M.S., Clemens, J.C., Nather, R.Winget, D.E., Watson, T.K., Yanagida, K., Dixson, J.SBradley, P.A., Wood, M.A., Sullivan, D.J., Kleinman, S.JMeistas, E., Liebowitz, E.M., Moskalik, P., Zola, S., Padosz, G., Krzesinski, J., Solheim, J.-E., Bruvold, AO’Donoghue, D., Katz, M., Vauclair, G., Dolez, N., Chereton, M., Barstow, M.A., Kanaan, A., Kepler, S.O., Givannini, O., Provenc¸al, J.L. & Hansen, C.J. 1995, ‘‘WholeEarth Telescope Observations of PG 21311066: AnotherVictory for Precision Asteroseismology,’’ ApJ,450, 350

Kelly, D.M. & Latter, W.B. 1995, ‘‘Spectroscopy of EvolvedStars in the Near Infrared: Explorations Beyond tAGB,’’ AJ, 109, 1320

Kelton, P.W. & Cornell, M.E., 1994, ‘‘Operations Issues fthe Hobby-Eberly Telescope,’’ ASP Conference Series79,136

Kepler, S.O., Giovannini, O., Wood, M.A., Nather, R.EWinget, D.E., Kanaan, A., Kleinman, S.J., Bradley, P.AProvenc¸al, J.L., Clemens, J.C., Claver, C.F., Watson, T.Yanagida, K., Krisciunas, K., Marar, T.M.K., Seetha, SAshoka, B.N., Leibowitz, E., Mendelson, H., Mazeh, TMoskalik, P., Krzesinski, J., Pajdosz, G., Zola, S., S

G.m.,&n

S

io

in

5,he

f-n.

y-13

&ere

.C

.,

.,ru,n-a-

rs

.,.

ine,

.DA

s

le

i-ts

I.,-w

e-

if-

to,’’

e

s-an

5,

GP

t

,of

4,i-n,’’

S.t

S.t

e-

ph,n,t

-

n


heim, J.-E., Emanuelsen, P.-I., Dolez, N., Vauclair,Chrevreton, M., Fremy, J.-R., Barstow, M.A., SansoA.E., Tweedy, R.W., Wickramasinghe, D.T., Ferrario, LSullivan, D.J., van der Peet, A.J., Bickley, D.A.H.Chen, A.-L. 1995, ‘‘Whole Earth Telescope Observatioof the DAV White Dwarf G226-29,’’ ApJ,447, 874

Kepler, S.O., Robinson, E.L. & Nather, R.E. 1995, ‘‘FOObservations of a Pulsating DA White Dwarf,’’ inCali-brating Hubble Space Telescope: Post Servicing Miss,eds. A. Koratkar and C. Leitherer~STScI, Baltimore!, p.104

Khokhlov, A.M. 1995, ‘‘Propagation of Turbulent FlamesSupernovae,’’ ApJ,449, 695

Kim, S.J., Trafton, L.M., Geballe, T.R. & Slanina, Z. 199‘‘2-mm Absorption Features of Hydrogen Dimers in tEquatorial Spectra of Jupiter,’’ Icarus,113, 217

Kim, S.-W., Wheeler, J.C. & Mineshige, S. 1994, ‘‘The Efect of Disk Irradiation on Outbursts in X-Ray Novae,’’ iThe Evolution of X-Ray Binaries, eds. S.S. Holt and C.SDay ~AIP, New York!, p. 213

King, J.R. 1994, ‘‘Stellar Oxygen Abundances. III. The Oxgen Abundance of the Very Metal Poor Halo Star BD-° 3442,’’ ApJ,436, 331

Kirkpatrick, J.D., McGraw, J.T., Hess, T.R., Liebert, J.McCarthy, D.W. Jr. 1994 ‘‘Luminosity Function at thEnd of the Main Sequence: Results of a Deep, Large-ACCD Survey for Cool Dwarfs,’’ ApJS,94, 749

Kleinman, S.J., Nather, R.E., Winget, D.E., Clemens, JBradley, P.A., Kanaan, A., Provenc¸al, J.L., Claver, C.F.,Watson, T.K., Yanagida, K., Dixson, J.S., Wood, M.ASullican, D.J., Meistas, E., Leibowitz, E.M., Moskalik, PZola, S., Pajdosz, G., Krzesinski, J., Solheim, J.-E., Bvold, A., O’Donoghue, D., Katz, M., Vauclair, G., DolezN., Chevreton, M., Barstow, M.A., Kepler, S.O., Giovanini, O., Hansen, C.J. & Kawaler, S.D. 1994, ‘‘Observtional Limits on Companions to G29-38,’’ ApJ,436, 875

Koresko, C.D. 1995, ‘‘Composite Spectra in Young StaAccretion or Close Companions?’’ ApJ,440, 746

Korista, K.T., Alloin, D., Barr, P., Clavel, J., Cohen, R.DCrenshaw, D.M., Evans, I.N., Horne, K., Koratkar, A.PKriss, G.A., . . . Wills, B.J.••• 1995, ‘‘Steps TowardDetermination of the Size an Structure of the Broad-LRegion in Active Galactic Nuclei. VIII. An Intensive HSTIUE, and Ground-Based Study of NGC5548,’’ ApJS,97,285

Kraft, R.P., Sneden, C., Langer, G.E. & Shetrone, M1995, ‘‘Oxygen Abundances in Halo Giants. VI. M10,Cluster with Metallicity Similar to M3 and M13,’’ AJ,109, 2586

Kusunose M. & Mineshige, S. 1995, ‘‘Hot Accretion Diskwith Nonthermal Pairs,’’ ApJ,440, 100

Lambert, D.L., Sheffer, Y. & Federman, S.R. 1995, ‘‘HubbSpace Telescope Observations of C2 Molecules in DiffuseInterstellar Clouds,’’ ApJ,438, 740

Lambert, D.L., Smith, V.V., Busso, M., Gallino, R. & Stranero, O. 1995, ‘‘The Chemical Composition of Red GianIV. The Neutron Density at thes-Process Site,’’ ApJ,450,302

,,

s

n

a

.,

-

:

,

.

.

Lazarian, A 1995, ‘‘Study of Turbulence in H I Using RadioInterferometers,’’ A&A,293, 507

Lester, D.F., Zink, E.C., Doppmann, G.W., Gaffney, N.Harvey, P.M., Smith, B.J. & Malkan, M. 1995, ‘‘FarInfrared Thermal Emission From the Inner Cooling FloRegion of NGC 1275,’’ ApJ,439, 185

Li, W., Evans, N.J. II, Harvey, P.M. & Colome´, C. 1994,‘‘Near-Infrared~J, H, K! Imaging of Herbig Ae/Be Stars,’’ApJ, 433, 199

Luhman, M.L., Jaffe, D.T., Keller, L.D. & Pak, S. 1994, ‘‘H

2 Emission as a Tracer of Molecular Hydrogen: LargScale Observations of Orion,’’ ApJL,436, L185

Luhman, M.L., Jaffe, D.T., Keller, L.D. & Pak, S. 1995, ‘‘ANew Fabry-Perot Spectrometer for Observations of Dfuse Near-Infrared Line Emission,’’ PASP,107, 184

Luo, S. & Vishniac, E.T. 1995, ‘‘Bayesian ApproachesTesting the Nature of Primordial Density FluctuationsApJ, 443, 469

Luo, S. & Vishniac, E.T. 1995, ‘‘Three Dimensional ShapStatistics: Methodology,’’ ApJS, 96, 429

Marsh, T.R., Robinson, E.L. & Wood, J.H. 1994, ‘‘Spectrocopy of A0620–00: The Mass of the Black Hole andImage of Its Accretion Disk,’’ MNRAS,266, 137

Marsh, T.R., Wood, J.H., Horne, K. & Lambert, D.L. 199‘‘The Discovery of High-Velocity Flares in NV and theDetection of Carbon in the Double Degenerate BinaryCom,’’ MNRAS, 274, 452

Martel, H. 1995, ‘‘Nonlinear Structure Formation in FlaCosmological Models,’’ ApJ,445, 537

Martel, H., Shapiro, P.R., Valinia, A. & Villumsen, J.V. 1995‘‘Large-Scale Structure Formation and the SegregationDark and Baryonic Matter,’’ inDark Matter, eds. S.S.Holt and C.L. Bennett, AIP Conference Proceedings336,p. 441

Martel, H., Shapiro, P.R., Villumsen, J.V.,& Kang, H. 199‘‘Adaptive Smoothed Particle Hydrodynamics with Applcation to Galaxy and Large-Scale Structure Formatioin Smooth Hydrodynamics in Astrophysics, eds. G. Bonoand J. Miller, Memorie Della Societa´ Astronomica Ital-iana,65, p. 1061

McWilliam, A., Preston, G.W., Sneden, C. & Shectman,1995, ‘‘A Spectroscopic Analysis of 33 of the MosMetal-Poor Stars. I.,’’ AJ,109, 2736

McWilliam, A., Preston, G.W., Sneden, C. & Shectman,1995, ‘‘A Spectroscopic Analysis of 33 of the MosMetal-Poor Stars. II.,’’ AJ,109, 2757

Miesch, M.S. & Scalo, J.M. 1995, ‘‘Exponential Tails in thCentroid Velocity Distributions of Star-Forming Regions,’’ ApJL, 450, L27

Miller, S., Achilleos, N., Dinelli, B.M., Lam, H.A., Tenny-son, J., Jagod, M.-F., Geballe, T.R., Trafton, L.M., JoseR.D., Ballester, G.E., Baines, K., Brooke, T.Y. & OrtoG. 1995, ‘‘The Effect of the Impact of ComeShoemaker–Levy 9 on Jupiter’s Aurorae,’’ GRL,22, 1629

Mineshige, S., Kusunose, M. & Matsumoto, R. 1995, ‘‘LowState Disks and Low-Beta Disks,’’ ApJL,445, L43

Moscoso, M.D. & Wheeler, J.C. 1994, ‘‘Electron-PositroPair Winds,’’ in The Evolution of X-Ray Binaries, eds.S.S. Holt and C.S. Day~AIP, New York!, p. 83

J.ds

ernc

,&o,’’

s,,

ssr,

th

-

.,anras-nn-&

e

-

.

.ofe,

idutera,

.,&er

.Cy-eh

is,.d-pJ,

l

l:pJ,

ea-

eof

-,’’-

ticd,

ero-

J.u-

ndJ.

i-y

,Vc-

-a

.

&h

n

656 ANNUAL REPORT

Najita, J., Ostriker, E., Wilkin, F., Johns, C.M. & Carr,1994, ‘‘The Interaction Between Stars and Disks: WinFunnel Flows, and More,’’ inClouds, Cores, and LowMass Stars: The Fourth Haystack Observatory Confence, eds. D. Clemens and R. Barvainis, ASP ConfereSeries65, 325

Nather, R.E. 1994, ‘‘Inside GD358,’’ Baltic Astronomy,2,436

Noll, K.S., McGrath, M.A., Trafton, L.M., Atreya, S.K.Caldwell, J.J., Weaver, H.A., Yelle, R.V., Barnet, C.Edgington, S. 1995, ‘‘HST Spectroscopic ObservationsJupiter After the Collision of Comet Shoemaker–Levy 9Science,267, 1307

Netzer, H., Brotherton, M.S., Wills, B.J., Han, M.S., WillD., Baldwin, J.A., Ferland, G.J. & Browne, I.W.A. 1995‘‘The HST Sample of Radio-Loud Quasars: The Lya/Hb Ratio,’’ ApJ, 448, 27

Percival, J.W., Boyd, P.T., Biggs, J.D., Dolan, J.F., BleR.C., Elliot, J.L., Nelson, M.J., Robinson, E.L., TayloM.J., van Citters, G.W. & Wolinski, K.G. 1995, ‘‘ASearch for a Pulsar in the Remnant of SN 1987a withSpace Telescope High-Speed Photometer,’’ ApJ,446, 832

Plume R. & Jaffe, D.T. 1995, ‘‘The World’s Smallest 10Meter Submillimeter Telescope,’’ PASP,107, 488

Provenc¸al, J.L., Winget, D.E., Nather, R.E., Robinson, E.LSolheim, J.-E., Clemens, J.C., Bradley, P.A., KleinmS.J., Kanaan, A., Claver, C.F., Hansen, C.J., MaT.M.K., Seetha, S., Ashoka, B.N., Leibowitz, E.M., Meitas, E.G., Bruvold, A., Vauclair, G., Dolez, N., ChevretoM., Barstow, M.A., Sansom, A.E., Tweedy, R.W., Fotaine, G., Bergeron, P., Kepler, S.O., Wood, M.A.Grauer, A.D. 1995, ‘‘The Unusual Helium Variable AMCanum Venaticorum,’’ ApJ,445, 927

Ramsey, L.W., Sebring, T.A. & Sneden, C.A. 1994, ‘‘ThSpectroscopic Survey Telescope Project,’’ inAdvancedTechnology Optical Telescopes V, SPIE Proceedings Series, ed. L.M. Stepp,2199, 31

Reach, W.T., Franz, B.A., Weiland, J.L., Hauser, M.GKelsall, T.N., Wright, E.L., Rawley, G., Stemwedel, S.W& Spiesman, W.J. 1995, ‘‘Observational Confirmationa Circumsolar Dust Ring by the COBE Satellite,’’ Natur374, 521

Ries, J.G. 1993, ‘‘On the Depletion of the Outer AsteroBelt,’’ in Proceedings of a NATO Advanced Study InstitFrom Newton to Chaos: Modern Techniques for Undstanding and Coping with Chaos in N-Body DynamicSystems, eds. A.E. Roy and B.E. Steves~Plenum PressNew York!

Robinson, E.L., Mailloux, T.M., Zhang, E., Koester, DStiening, R.F., Bless, R.C., Percival, J.W., Taylor, M.J.van Citters, G.W. 1995, ‘‘The Pulsation Index, EffectivTemperature, and the Thickness of the Hydrogen Layethe Pulsating DA White Dwarf G117-B15A,’’ ApJ,438,908

Robinson, E.L., Wood, J.H., Bless, R.C., Clemens, JDolan, J.F., Elliot, J.L., Nelson, M.J., Percival, J.W., Talor, M.J., van Citters G.W. & Zhang, E. 1995, ‘‘HubblSpace Telescope Observations of the Dwarf Nova Z Cmealeontis Through Two Eruption Cycles,’’ApJ,443, 295

,

-e

f

,

e

,r,

,

,

e-l

in

.,

a-

Ruiz-Lapuente, P., Kirshner, R.P., Phillips, M.M., ChallP.M., Schmidt, B.P., Filippenko, A.V. & Wheeler, J.C1994, ‘‘Late-Time Spectra and Type IA Supernova Moels: New Clues from the Hubble Space Telescope,’’ A439, 60

Ryan, S.G. & Lambert, D.L. 1995, ‘‘Demise of the MetaPoor Disk?: Spectroscopic Iron Abundances,’’ AJ,109,2068

Shafter, A.W., Veal, J.M. & Robinson, E.L. 1995, ‘‘A RadiaVelocity Study of the Dwarf Nova AR AndromedaeComparison of the Quiescent and Outburst States,’’ A440, 853

Shapiro, P.R., Martel, H. & Villumsen, J.V. 1994, ‘‘AdaptivSmoothed Particle Hydrodynamics and Galaxy Formtion,’’ in Numerical Simulations in Astrophysics, eds. J.Franco, S. Lizano, L. Aguilar, and E. Daltabuit~Cam-bridge University Press, Cambridge, UK!, p. 45

Shapiro, P.R., Martel, H. & Villumsen, J.V. 1994, ‘‘AdaptivSmoothed Particle Hydrodynamics and the SimulationLarge-Scale Structure Formation,’’ inEvolution of theUniverse and its Observational Quest, Proceedings of Ya-mada Conference XXXVII, ed. K. Sato~Universal Acad-emy Press, Tokyo!, p. 295

Shapiro, P.R. & Martel, H. 1995, ‘‘The Effect of Reionization of the Intergalactic Medium on Galaxy Formationin Dark Matter, eds. S.S. Holt and C.L. Bennett, AIP Conference Proceedings336, p. 446

Shapiro, P.R. 1995, ‘‘The Reionization of the IntergalacMedium,’’ in The Physics of the Interstellar Medium anthe Intergalactic Medium, eds. A. Ferrara, C.F. Mc KeeC. Heiles, and P.R. Shapiro, ASP Conference Series80, p.55

Shelus, P.J., Ricklefs, R.L., Gyo¨rgyey-Ries, J., Whipple, A.L.& Wiant, J.R. 1995, ‘‘McDonald Observatory Lunar LasRanging: Beginning the Second 25 Years,’’ IAU Sympsium No. 172, Paris, France

Shields, G.A., Dufour, R.J., Skillman, E.D. & Wyatt, R.1994, ‘‘The Star Formation History and Chemical Evoltion of GR 8 from HST Observations,’’ inThird CTIO/ESO Workshop on the Local Group: Comparative aGlobal Properties, eds. A. Layden, R. C. Smith, andStorm~European Southern Observatory, Garching!, p. 65.

Smith, B.J., Harvey, P.M. & Lester, D.F. 1995, ‘‘The Distrbution of Far-Infrared Light in the ’Dusty Hand’ GalaxNGC 2146,’’ ApJ,442, 610

Smith, D.M., Lin, R.P., Anderson, K.A., Hurley, K. & JohnsC.M. 1995, ‘‘High-Resolution Spectra of 20–300 keHard X-Rays from Electron Precipitation Over Antartica,’’ JGR,100, 19675

Smith, V.V. & Lambert, D.L. 1994, ‘‘High-Resolution Spectroscopy of the Post-AGB Star V1853 Cygni: Birth ofPlanetary Nebula?’’ ApJL,424, L123

Smith, V.V., Plez, B., Lambert, D.L. & Lubowich, D.A1995, ‘‘A Survey of Lithium in the Red GIants of theMagellanic Clouds,’’ ApJ,441, 735

Sneden, C., Preston, G.W., McWilliam, A., Searle, L.Cowan, J.J. 1995, ‘‘A Very Metal-Poor Field Giant witExtremer -Process Abundance Enhancements,’’ inNucleiin the Cosmos III, Third International Symposium o

.mr-om,’’

-

-ri-

T.-ins

t,in-ed

ar

nd

-

ice-

o-s-

4,inrim

.Lllery

a

,

4,

.,e,r-del,-

.,r,.,C.,ko.,&in

S.,IL,

w

,

et

-

-

.,r-of31

s,’’

ack

4,


Nuclear Astrophysics, AIP Conference Proceedings327,eds. M. Busso, R. Gallino, and C. Raiteri~American In-stitute of Physics, New York!, p. 37

Spiesman, W.J., Hauser, M.G., Kelsall, T., Lisse, C.MMoseley, S.H. Jr., Reach, W.T., Silverberg, R.F., Stewedel, S.W. & Weiland, J.L. 1995, ‘‘Near- and FaInfrared Observations of Interplanetary Dust Bands frthe COBE Diffuse Infrared Background ExperimentApJ, 442, 662

Stern, S.A. & Trafton, L.M. 1994, ‘‘The Ultraviolet Spectrum of Triton from HST: First Results,’’ Icarus,112, 533

Stern, S.A., Trafton, L.M. & Flynn, B. 1995, ‘‘RotationallyResolved Studies of the Mid-Ultraviolet Spectrum of Tton. II. HST Surface and Atmospheric Results,’’ AJ,109,2855

Szczerba, R., Krelowski, J., Walker, G.A.H., Kennelly, E.Sneden, C., Volk, K. & Hill, G. 1994, ‘‘Correlation between Molecular Lines and Diffuse Interstellar Bands,’’The Diffuse Interstellar Bands: Contributed Paper,NASA Conference Publications10144, ed. A.G.G.M. Tie-lens, p. 33

Taylor, M., Bless, R.C., Ogelman, H., Dolan, J.F., EllioJ.L., Gallagher, J.S., Nelson, M.J., Percival, J.W., Robson, E.L. & van Citters, G.W. 1994, ‘‘Ultraviolet Photometry of Nova Cygni 1992 Obtained with the High-SpePhotometer,’’ ApJL,424, L45

Teays, T.J., Bonnell, J.T., Schmidt, E.G., Guinan, E.F. & Bnes, T.G. 1994, ‘‘The Blazhko Effect in RR Lyrae,’’ inFrontiers of Space and Ground-based Astronomy, 27thESLAB Symposium, eds. W. Wamsteker, M. Longair, aY. Kondo ~Kluwer!, p. 59

Thompson, K.L., Elston, R. & Hill, G.J. 1994, ‘‘Strong Optical Fe II Emission inz.2 QSOs,’’ in Infrared As-tronomy With Arrays: the Next Generation, ed. I.S.McLean ~Kluwer, Dordrecht!, p. 497

Tomkin, J., Pan, X. & McCarthy, J.K. 1995, ‘‘SpectroscopDetection of the Secondaries of the Hyades Interferomric Spectroscopic Binaryu2 Tauri and of the Interferometric Spectroscopic Binarya Andromedae,’’ AJ,109, 780

Tomkin, J., Woolf, V.M. & Lambert, D.L. 1995, ‘‘Carbon inField F and G Disk Dwarfs,’’ AJ,109, 2204

Trafton, L.M. 1995, ‘‘Induced Spectra in Planetary Atmspheres,’’ inCollision- and Interaction-Induced Spectrocopy, eds. G.C. Tabisz and M.N. Neuman~Kluwer, Dor-drecht!, p. 517

Trammell, S.R., Dinerstein, H.L. & Goodrich, R.W. 199‘‘Evidence for the Early Onset of Aspherical Structurethe Planetary Nebula Formation Process: Spectropolaetry of Post-AGB Stars,’’ AJ,108, 984

Tull, R.G., MacQueen, P.J., Sneden, C. & Lambert, D1995, ‘‘The High-Resolution Cross-Dispersed EcheWhite-Pupil Spectrometer of the McDonald Observato2.7-M Telescope,’’ PASP,107, 251

,-

,

-

-

t-

-

.

Vishniac, E.T. 1995, ‘‘The Dynamics of Flux Tubes inHigh b Plasma. I. A General Description,’’ ApJ,446, 724

Wang, Y., Jaffe, D.T., Graf, U.U. & Evans, N.J. II 1994‘‘Single-Sideband Calibration for CO,13CO, HCN, andCS lines near 345 GHz,’’ ApJS,95, 503

Wegner, W., Snow, T.P., Sneden, C. & Krelowski, J. 199‘‘Diffuse Bands versus Extinction Parameters,’’ inTheDiffuse Interstellar Bands: Contributed Papers, NASAConference Publications10144, ed. A.G.G.M. Tielens, p.39

Weiland, J.L., Arendt, R.G., Berriman, G.B., Dwek, EFreudenreich, H.T., Hauser, M.G., Kelsall, T., LissC.M., Mitra, M., Moseley, S.H., Odegard, N.P., Silveberg, R.F., Sodroski, T.J., Spiesman, W.J. & StemweS.W. 1994, ‘‘COBE Diffuse Background Experiment Observations of the Galactic Bulge,’’ ApJL,425, L81

Wells, L.A., Phillips, M.M., Suntzeff, N.B., Heathcote, S.RHamuy, M., Navarrete, H.M., Fernandez, M., WelleW.G., Schommer, R.A., Kirshner, R.P., Leibundgut, BWillner, S.P., Peletier, R.F., Schlegel, E.M., Wheeler, J.Harkness, R.P., Bell, D.J., Matthews, J.M., FilippenA.V., Shields, J.C., Richmond, M.W., Jewitt, D., Luu, JTran, H.D., Appleton, P.N., Robson, E.I., Tyson, J.A.Guhathakurta, P. 1994, ‘‘The Type Ia Supernova 1989BNGC 3627~M66!,’’ AJ, 108, 2233

Wheeler, J.C., Harkness, R.P., Clocchiatti, A., Benetti,Brotherton, M., Depoy, D.L. & Elias, J. 1994, ‘‘SN 1994in MS1 and the Nature of Type Ibc Supernovae,’’ ApJ436, 135

Wheeler, J.C. 1994, ‘‘Black Hole X-Ray Novae: A NeView into the Abyss,’’ Griffith Observer,59, 2

Wheeler, J.C., Harkness, R.P., Khokhlov, A.M. & Ho¨flich, P.1994, ‘‘Stirling’s Supernovae: A Survey of the Field,’’ inThe Physics of Supernovae, eds. D.H. Feng, S. Bludmanand S. Pittel~Elsevier Science, Amsterdam!, 256, 211

Whipple, A.L., Shelus, P.J. & Whited, R. 1995, Minor PlanCirc. no. 25288

Whipple, A.L. 1995, ‘‘Lyapunov Times of the Inner Asteroids,’’ Icarus,115, 347

Wills, B.J. & Brotherton, M.S. 1995, ‘‘An Improved Measure of Quasar Orientation,’’ ApJ,448, 81

Wills, B.J., Thompson, K.L., Han, M., Netzer, H., Wills, DBaldwin, J.A., Ferland, G.J., Browne, I.W.A. & Brotheton, M.S. 1995, ‘‘Hubble Space Telescope SampleRadio-Loud Quasars: Ultraviolet Spectra of the FirstQuasars,’’ ApJ,447, 139

Yi, I. & Vishniac, E.T. 1994, ‘‘The Hard X-Ray EmissionSpectra From Accretion Columns in Intermediate PolarApJ, 435, 829

Zhou, S. & Evans, N.J. II 1994, Proceedings of the HaystMeeting, ASP Conference Series65, 183

Zhou, S., Wang, Y., Evans, N.J. II, Peng, R. & Lo, K.Y. 199ApJ, 433, 131

University of Texas McDonald Observatory and Department of … · 2020. 1. 3. · University of...

Documents

Transcript of University of Texas McDonald Observatory and Department of … · 2020. 1. 3. · University of...