GTO Observing Program and Target List

Jeffrey Linsky and Cool Star Mafia

COS Team meetingSpace Telescope Science

Institute26 October 2007

Cool Stars COS Observing Program Program Targets Orbits

Brown dwarfs 6* 29*

Metal deficient chromospheres 1 2

Alien dwarfs 1 8

Pre-main sequence stars 4 16

Solar mass stars: cradle to grave 3 5

Transiting Planets 1 20

Total number of orbits 16 80

*Deeper exposures for two of the brown dwarf targets included in # of orbits.

Brown dwarf observing program: Testing structural scenarios

• Question: Are young brown dwarfs with disks low mass versions of CTTSs?

• Question: Is the high T gas heated by (MHD) accretion from disks (or close secondaries).

• Question: Is the H2 emission Lyα fluorescence?• Question: Are the older brown dwarfs without disks low

mass versions of active M dwarfs with flare-event (transient) heating?

• Question: How does the absence of H core burning (due to low mass and/or age) change the outer atmosphere structure and heating from that seen in M dwarfs?

Ultraviolet spectra of L and T dwarfs (collisionally excited and fluorescent lines)

• 2MASSW J1207334-393254 (0.03Msun, 70 pc) is the closest L dwarf with a disk.

• STIS G140L 5.0ks obs by Gizis et al. 2005). Age ~10 Myr

• Study the chromospheric and fluorescent (H2 and ?) lines for a range of L and T dwarfs of different ages and compare with M dwarfs.

• What is the amount and character of nonradiative heating processes in cool fully convective stars?

• 7 targets. Number of orbits 36.

Preliminary BD target list

Target (2MASS or other) SpType d(pc) J 1207334-393254 M8bin 59(TYA) 12.98VB10 M8 5.78LHS 1070C L0 7.711507476-162738 L5 7.33 12.821315309-264951 L5 55(TYA) 15.180255035-470050 L8 4.9 13.231237+6526 T6bin? 14 15.4

Information on 2MASS 1207• Probably in the TW Hya Association with age 6-

10 Myr. Evidence for accretion like TW Hya.• Closest known BD with a disk. Very strong Hα

emission.• Emission lines of C II-IV, O I, and He II detected

in the STIS G140L 5 ks exposure.• Many H2 emission lines seen pumped by Lyα.

Compare with or reconstruct the Lyα emission line to test.

• C IV count rate with COS G130M would be 0.5/sec.

COS Simulated G140L spectrum of 2MASS1207 (6ks, night)

COS Simulated G130M and G160M spectra of 2MASS1207

• 6 ks night spectra.• C III, N V, C II, O I, C

IV, and He II fluxes from STIS.

• Fluorescent H2 emission (observed in STIS spectrum) are scaled from TW Hya spectrum.

Brown dwarf observing program: Proposed plan

• For 2MASS1207 the line fluxes are known, so obtain G130M and G160M exposures and a deep G140L exposure (9 orbits).

• For the other 6 targets first obtain 2 orbit test exposures with G140L (12 orbits).

• Then decide which targets to obtain deeper G140L or G130M and G160M exposures (3 stars, 5 orbits each = 15 orbits).

• Total request 36 orbits.

Activity in Ancient Metal Deficient Chromospheres

• Question: How are the physical properties and heating mechanisms of chromospheres in very metal deficient giants different from normal metal stars?

• Question: Does extreme age and low metalicity change the cooling channels and lead to pure acoustic (basal heating) without any magnetic heating?

• Proposed by Graham Harper (CASA).• Targets: 2 stars, 2 orbits each, G140L (1230Å setting to

avoid Lyα), FP-SPLIT=2 or 4.• HD 216143: [Fe/H]=-2.3, V=7.82, vrad = -116 km/s (see

simulated spectrum).• HD 6833: [Fe/H]=-1.6, V=6.75.

Activity in Ancient metal Deficient Chromospheres: A simulated Spectrum• 2 orbit G140L spectrum

of HD 216143.• Collisionally-excited and

fluorescent lines (e.g. OI).• Scaled from α Boo using

COS simulator.• GHRS Mg II spectra

useful.• GHRS G160M 6 ks

spectrum and long IUE SWP-LO spectra show only noise and geocoronal emission.

Alien Dwarfs: Studying the Arcturus Moving Group

• Background: The Arcturus MG studied by Eggen consists of high velocity stars captured from another galaxy with [Fe/H] = -0.68 (1/5 solar).

• Question: How does metal poverty change the heating, structure, and dynamics of the outer layers of stars?

• Observe fluxes and line widths of C IV, Si IV, O IV, Si II, and He II lines.

• 1 target observed with G140L , G130M, and G160M, 12 orbits total.

• To be analyzed by Alec Brown.

Alien Dwarfs: Targets and Observing Program

• Target: HD 199288, V=6.5, d=21.6 pc.• Age: 6-7 Gyr.• Brightest known alien G dwarf. • No previous UV spectra of the aliens.• X-ray detections and Ca II flux predict UV emission line

fluxes somewhat below solar minimum values.• Predict G140L C IV 1550Å peak count rates of 0.1

cts/RE/s and S/N=30 in 5 ks (line fluxes in 1.5 orbits).• Predict G160M C IV 1550Å peak count rates of 0.02

cts/RE/s and S/N=15 in 12 ks (line widths in 4 orbits).• G130M to measure C II and other line widths (1.5 orbits).

Evolution of activity of solar mass stars: from the cradle to the grave

• Question: How does chromospheric and coronal activity decline as stars lose angular momentum and magnetic fields with age?

• Important for predicting the atmospheres of young planets that are blasted by strong UV radiation and stellar winds from young stars.

• Measuring fluxes and profiles of emission lines formed at different temperatures needed to predict the ionizing flux and wind from the star.

• Extension of Tom Ayres’ “Sleuthing the Dynamo” project with HST/STIS. Excellent STIS spectra of α Cen (G2 V) and α Boo )(K2 III) available for comparison.

• 4 targets, 10 orbits total.

Evolution of solar mass stars: simulated COS G130M and G160M spectra

• Top in each panel: β Hydri (G2 IV, 7 Gyr, 8 pc).

• Middle: HD 28344 (Hyades G2 V, 600 Myr, 44 pc).

• Bottom: HII 314 (Pleiades G1 V, 100 Myr, 130 pc).

• Horizontal lines: overlight (100 cts/s/RE), S/N=30, and S/N=10.

• HD 28344 and HII 314 observed with FOS. TTAG mode to look for flares.

Evolution of solar mass stars: The age (activity) sequence

• The youngest G star: HD 14082B (in β Pic MG, age=10Myr, d=34pc). Simulated spectra of HD 14082B (top), HII 314 (below).

• 10 Myr (HD 14082B)• 100 Myr (HII 314)• 600 Myr (HD 28344)• 5 Gyr (α Cen)• 7 Gyr (β Hyd)

Accretion flows and winds of PMS stars

• STIS E140M spectrum (2.3ks) of the brightest TTS TW Hya. Face-on disk. 56 pc. mv=11.1

• Evidence for accretion flows in CIV and NV lines and wind absorption in CII and Lyα.

• Need high S/N of several TTS with different inclination angles to determine T range, flow velocities, and column densities of inflows and outflows.

• 4 TTS observed for 4 orbits each. E.g. V4046 Sgr, DF Tau, BP Tau, GG Tau.

Atmospheres and winds of transiting planets

• Transit of a close-in Jupiter-like planet (Porb≈3 days) around HD 209458 (G0 V).

• Apd/Astar ≈ 1.5% but absorption in Lyα 5±2% and in C II 7.5±3.5%.

• STIS G140L resolution (600 km/s) so absorption width, Doppler shift, and central depth not measured. Also stellar line flux variable.

• Need COS for high S/N and 15 km/s resolution.

• Vidal-Madjar et al. proposed a hydrodynamic escape model for the outflow but mass loss rate very uncertain.

Vidal-Madjar et al. ApJ 604, L69 (2004)and Nature 422, 143 (2003)

Why observe a transiting planet?• Lifetime and evolution of

“roasters” could be determined by atmospheric loss rate.

• What is chemical composition of the atmospheres?

• What physical processes dominate the mass loss?

• Observations at quadratures (±130 km/s) may show scattered light and/or aurorae.

• Demonstration of COS capabilities: high time resolution, sensitivity, and ability to detect weak features.

• HD 189733b an alternative. 4 orbits of STIS G140Ldata during midtransit.

Cool Stars COS Observing Program Program Targets Orbits

Brown dwarfs 6* 29*

Metal deficient chromospheres 1 2

Alien dwarfs 1 8

Pre-main sequence stars 4 16

Solar mass stars: cradle to grave 3 5

Transiting Planets 1 20

Total number of orbits 16 80

*Deeper exposures for two of the brown dwarf targets included in # of orbits.

Supplementary Slides

Information on VB10

• M8 standard star.• Hα in emission.• X-ray emission detected (Fleming et al.

ApJ 594, 982 (2003)). Quiescent emission log Lx/Lbol = -4.9.

Information on LHS 1070C

• 2MASS 0024442-270825 data in Cruz et al. (AJ 133, 439 (2007).

• Nearest L0 brown dwarf.

Information on 2MASS 1507

• Data in Cruz et al (2007)• Nearest L5 brown dwarf

Information on 2MASS 1315

• See Gizis (ApJ 575, 484 (2002)).• Probable member of the TW Hya

Association.• Very strong Hα emission.• Mass about 0.025 solar.

Information on 2MASS 0255

• Also DENIS-P J0255-4700.• Data in Cruz et al. (2007)• Nearest known L8 brown dwarf.

Information on 2MASS 1237

• See Burgasser et al. (AJ 123, 2744 (2002)).

• Very strong Hα emission. LHα/Lbol far above all studied L and T dwarfs.

• Possible Hα velocity shifts suggests a BD binary.

Advantages of COS for observations of cool stars

• G130M mode (20,000 res. 1132-1469Å) is 10-20 times more sensitive than STIS E140M (40,000 res. 1140-1735Å)

• G160M mode (20,000 res. 1382-1798Å) ~10 times more sensitive than STIS E160M at C IV 1550Å.

• G140L mode (2,500 res. 1105-2378Å) X times more sensitive than STIS G140L at C IV 1550Å.

• 2.5” aperture (no slit loss, good for photometry, include CS emission)

Disadvantages of COS for observation of cool stars and ISM

• 2.5” aperture means strong Lyα (and O I 1302Å) geocoronal emission 35 cts/s (night) or 200 cts/s (day). In principle, this can be subtracted.

• S/N ≈ 45 with FP-SPLIT.• Cannot separate stellar

from CS emission.• No R=100,000 mode or

long slit spectral imaging or coronography.