TESS Open Cluster Surveya.k.a. T O C S

David Latham

TESS• Launch: March 2018

• All sky (nearly) over 2 years

• 4 cameras cover 24x96 deg. FOV, 21” pixels, 600-1000nm bandpass

• 13 observing sectors per hemisphere

• Observe each sector for 2 orbital periods = 2 x 13.7 days = 27.4 days

• Sector overlap => Tobs > 27 days at larger ecliptic latitude

• Monitor about 200,000+ late-type dwarfs @ 2-min. cadence (30-min FFI)

• Primary goal: small planets around bright/nearby stars

The overlap of the sectors is illustrated in Fig. 7.Approximately 30;000 deg2 are observed for at least 27 days.Close to the ecliptic poles, approximately 2800 deg2 areobserved for more than 80 days. Surrounding the eclipticpoles, approximately 900 deg2 are observed for more than300 days.

7.3 Data Downlink and Housekeeping Operations

At perigee, science operations are interrupted for no more than16 h to point TESS’s antenna toward Earth, downlink data, andresume observing. This includes a nominal 4-h period forKa-band science data downlink using NASA’s Deep SpaceNetwork. In addition, momentum unloading is occasionallyneeded due to the ≈1.5 Nm of angular momentum build-upinduced by solar radiation pressure. For this purpose, TESSuses its hydrazine thrusters.

7.4 Ground-Based Data Analysis and Follow-Up

The TESS data will be processed with a data reduction pipelinebased on software that was developed for the Kepler mission.20

This includes pixel-level calibration, background subtraction,aperture photometry, identification and removal of systematicerrors, and the search for transits with a wavelet-domainmatched filter.

Once the data are processed and transits are identified,selected stars will be characterized with ground-based imagingand spectroscopy. These observations are used to establishreliable stellar parameters, confirm the existence of planets,and establish the sizes and masses of the planets. Observationswill be performed with committed time on the Las CumbresObservatory Global Telescope Network and the MEarthobservatory. In addition, the TESS science team membershave access to numerous other facilities (e.g., Keck, Magellan,Subaru, HARPS, HARPS-North, Automated Planet Finder)through the usual telescope time allocation processes at theirhome institutions. The TESS team includes a large group of col-laborators for follow-up observations and welcomes additionalparticipation.

8 Anticipated Results

8.1 Photometric Performance

Figure 8 shows the anticipated photometric performance of theTESS cameras. The noise sources in this model are photon-counting noise from the star and the background (zodiacallight and faint unresolved stars), dark current (negligible), read-out noise, and a term representing additional systematic errorsthat cannot be corrected by cotrending. The most important sys-tematic error is expected to be due to random pointing variations(“spacecraft jitter”). Because of the nonuniform quantum effi-ciency of the CCD pixels, motion of the star image on theCCD will introduce changes in the measured brightness, asthe weighting of the image PSF changes, and as parts of theimage PSF enter and exit the summed array of pixels.

The central pixel of a stellar image will saturate at approx-imately IC ¼ 7.5. However, this does not represent the brightlimit for precise photometry because the excess charge is spreadacross other CCD pixels and is conserved, until the excesscharge reaches the boundary of the CCD. As long as the photo-metric aperture is large enough to encompass all of the charge,high photometric precision can still be obtained. The Keplermission demonstrated that photon-noise–limited photometrycan be obtained for stars 4 mag brighter than the single-pixelsaturation limit.21 Since similar performance is expected forTESS, the bright limit is expected to be IC ≈ 4 or perhapseven brighter.

8.2 Transit Detections

Monte Carlo simulations are used to verify that the scienceobjectives can be met and to anticipate the properties of thedetected planetary systems.12 These simulations are based ona model of the local neighborhood of main-sequence FGKMstars.11 Simulated stars are populated randomly with planets,and “observed” by TESS. Those for which transits are observedwith a sufficiently high signal-to-noise ratio are counted asdetections. In addition, the simulated star catalog is populatedwith eclipsing binaries that may be blended with brighter stars to

Fig. 7 (a) The instantaneous combined field of view of the four TESS cameras. (b) Division of thecelestial sphere into 26 observation sectors (13 per hemisphere). (c) Duration of observations on thecelestial sphere taking into account the overlap between sectors. The dashed black circle enclosingthe ecliptic pole shows the region which James Webb Space Telescope will be able to observe atany time.

Journal of Astronomical Telescopes, Instruments, and Systems 014003-7 Jan–Mar 2015 • Vol. 1(1)

Ricker et al.: Transiting Exoplanet Survey Satellite

Downloaded From: http://astronomicaltelescopes.spiedigitallibrary.org/ on 07/13/2015 Terms of Use: http://spiedl.org/terms

The space revolution

TOCS working groupChair:

Soren Meibom

Steering committee:Sofia RandichWillie TorresDavid James

Sydney Barnes

- TOCS Charter

- Membership policy

…like, really smart and stable geniuses:

David LathamPhillip Cargile Nicholas WrightElisabeth Newton Adam KrausRob JeffriesSam QuinnGermano SaccoRichard JacksonVeronica RoccatagliataGeorge ZhouAaron RizzutoStephanie DouglasAndrew MannElena FranciosiniSaskia HekkerSarbani Basu

Nina KharchenkoKeivan StassunBob MathieuEric MamajekAaron GellerFabienne BastienNatalie GosnellSteven SaarJose Dias do NascimentoJoshua PepperGiovanni CarraroJason CurtisJoseph GlaserEdward GillenJoey RodriguezAndrew VanderburgJeb BailyJonathan Thornton

Goals of TOCSwg

• To construct a list of members of open clusters, groups, and associations/SFR to be observed by TESS

• To form collaborations and lead cluster research using TESS data

Consideration for cluster and star selection

• TESS aperture and pixel scale => nearby (~< 800pc) clusters

• Planets of all sizes of interest in clusters (SNR=7.3) => light curve simulations => Tmag =14 faint limit on 2-min cadence targets (1% error; Jupiter/Sun, Neptune/M-dwarf) - Elisabeth Newton, Aaron Rizzuto

• Prioritization of targets: Priority = 1 / [R*sqrt(sig)]

Plan and execution• Assemble best published and unpublished information on

all potential clusters (all available photometry, kinematic data, Li and activity data, etc. useful for identification and characterization of clusters and their member stars)

• Monthly meetings, voluntary contributions/presentations from 2/3 of members - Gaia ESO survey group, Adam Kraus

• The TOCS wiki

The TOCS wiki pages

Astrometric modeling• Nick Wright• High-precision proper motions

from Gaia DR1 and the HSOY catalogue were also used to astrometrically model the clusters and their background and foreground field star populations in proper motion space

IC 2391

Refining cluster and stellar properties• Phill Cargile• MINESweeper: Bayesian

tool to refine the properties of individual cluster stars by modeling all available photometry, spectroscopy

• Sisters: Bayesian tool using output posterior information from MINESweeper to infer the distance, age, and membership probabilities for each individual cluster.

• MINESweeper+Sisters => robust cluster+stellar parameters incl. membership

Distance: 437 +/- 26 pc

Age: 353 +/- 68 Myr Distance: 437 +/- 26 pc

The southern TOCS clusters• Main-sequence: 14

clusters, 2,080 2-min + 763 30-min

• PMS: 10 clusters, 777 2-min + 550 30-min

• YMG: 8 (AB Dor, β Pic, Carina, Tuc-Hor, TW Hydra, 32 Ori, Columba, and η Cha)

‣ 568 2-min + ~1,100 30-min

YMG

The southern TOCS clusters

• Main-sequence: SNR-based calc. => 4.0 +- 1.6 - George Zhou

• PMS: 4

• YMG: 17

YMG

Expected planet yield

Questions?