Early science on Early science on exoplanets with Gaiaexoplanets with Gaia

A. MoraA. Mora11, L.M. Sarro, L.M. Sarro22, S. Els, S. Els33, R. Kohley, R. Kohley11

11ESA-ESAC Gaia SOC. Madrid. SpainESA-ESAC Gaia SOC. Madrid. Spain22UNED. Artificial Intelligence Department. Madrid. UNED. Artificial Intelligence Department. Madrid.

SpainSpain33Gaia DPAC Project Office. Madrid. SpainGaia DPAC Project Office. Madrid. Spain

2010-05-20. GREAT Exoplanets Kick-off meeting. Osservatorio Astronomico di Torino

1. Introduction1. Introduction

Exoplanets: thousands Exoplanets: thousands candidatescandidates

► Thousands of Jupiter sized planets with Thousands of Jupiter sized planets with aa ~ 1 AU ~ 1 AU► 5 years survey for high precision parameters5 years survey for high precision parameters► Uncertainties for large period exoplanetsUncertainties for large period exoplanets

Low precision for periods larger than mission lifetimeLow precision for periods larger than mission lifetime

Casertano et al. (2008)

Hypothesis: 1.5 yr early Hypothesis: 1.5 yr early releaserelease

► The astrometric solution (AGIS) needs 1.5+ The astrometric solution (AGIS) needs 1.5+ years of data to provide parallaxesyears of data to provide parallaxes

► End of mission: best astrometric precisionEnd of mission: best astrometric precision G2V: G2V: σσππ < 7 < 7 μμas (V<10), 24 as (V<10), 24 μμas (V=15), 300 as (V=15), 300 μμas (V=20)as (V=20)

► Planet detection: individual measurementsPlanet detection: individual measurements Bright limit (G<11), Bright limit (G<11), σσAL,1CCDAL,1CCD ~ 50 ~ 50 μμas, as, σσAC,1CCDAC,1CCD ~ ~

250250μμasas►Number of transits on the Gaia field of viewNumber of transits on the Gaia field of view

They can be predicted (scanning law)They can be predicted (scanning law) ~80, end of mission (5 years)~80, end of mission (5 years) ~24, hypothetical early realease (1.5 years)~24, hypothetical early realease (1.5 years)

AL & AC single CCD precisionAL & AC single CCD precision

de Bruijne (2009)

Gaia scanning lawGaia scanning law

2. Radial velocity 2. Radial velocity candidates inclinationcandidates inclination

RV candidates inclinationRV candidates inclination

► Radial velocity (RV) techniqueRadial velocity (RV) technique Hundreds of exoplanet candidatesHundreds of exoplanet candidates

► Inclination (Inclination (sin sin ii) determination is difficult) determination is difficult► HST FGS provides narrow field mas astrometryHST FGS provides narrow field mas astrometry

Inclinations for ~6 RV candidatesInclinations for ~6 RV candidates

Benedict et al. (2010)Benedict et al. (2002)

RV candidates selectionRV candidates selection

► Combination of RV and Gaia early dataCombination of RV and Gaia early data Minimum sampling: half a period (P ≤ 3 yr)Minimum sampling: half a period (P ≤ 3 yr) 1 Transit bright limit (G<11) average precision:1 Transit bright limit (G<11) average precision:

►σσAL,1transitAL,1transit ~ 17 ~ 17 μμas, as, σσAC,1transitAC,1transit ~ 84 ~ 84 μμasas

~24 data points (one per transit)~24 data points (one per transit) Astrometric signatureAstrometric signature

►αα = (M = (MPP / M / M) (a) (aPP / 1AU) (pc / d) arcsec / 1AU) (pc / d) arcsec

►αα ≥ 3 ≥ 3 σσAL,1transitAL,1transit = 51 = 51 μμasas

Gaia brightness bright end limit: G ≥ 6Gaia brightness bright end limit: G ≥ 6

► ~50 suitable candidates. Inclination known for ~50 suitable candidates. Inclination known for twotwo

Orbital element Orbital element determinationdetermination

►Orbital element determination is a complex Orbital element determination is a complex non-linear problemnon-linear problem

►Simulations neededSimulations needed To learn what extra knowledge can be gainedTo learn what extra knowledge can be gained Arbitrary thresholds used. Number of suitable Arbitrary thresholds used. Number of suitable

candidates can be very differentcandidates can be very different

►RV data coeval with Gaia probably neededRV data coeval with Gaia probably needed Simulations Simulations better telescope time allocation better telescope time allocation

3. Early candidates 3. Early candidates radial velocity follow-radial velocity follow-

upup

Exoplanets: 1.5 year surveyExoplanets: 1.5 year survey

► Will planets be detected?Will planets be detected? Biased, order of magnitude Biased, order of magnitude

estimation: 40% of 5 yr estimation: 40% of 5 yr

~3000 objects~3000 objects

► Lots of planetary systemsLots of planetary systems

► Many false detectionsMany false detections

► Low period planets onlyLow period planets only

► Low precision parametersLow precision parameters

► Break degeneracies Break degeneracies RV RV

Casertano et al. 2008

~40%

RV follow-up of early RV follow-up of early candidatescandidates

► RV confirmation of candidates RV confirmation of candidates false false detectionsdetections

► Planetary systems parametersPlanetary systems parameters Break degeneracies and high precision parametersBreak degeneracies and high precision parameters RV monitoring during many periods requiredRV monitoring during many periods required

► Plenty of telescope time needed !!Plenty of telescope time needed !! Dedicated telescopes/instruments?Dedicated telescopes/instruments?

► Simulations Simulations observations optimization observations optimization Number and time of RV measurementsNumber and time of RV measurements Upcoming astrometric data has to be consideredUpcoming astrometric data has to be considered

4. Stellar activity:4. Stellar activity:impact on astrometryimpact on astrometry

Stellar activity: starspotsStellar activity: starspots

► Starspots in active stars can be very largeStarspots in active stars can be very large► They leave astrometric signaturesThey leave astrometric signatures

~10 ~10 μμAU (LC V), ~500 AU (LC V), ~500 μμAU (LC III), ~10000 AU (LC III), ~10000 μμAU AU (LC I)(LC I)

Strassmeier (2009)

Stellar activity: impactStellar activity: impact

Eriksson & Lindegren (2007)

Stellar activity: impactStellar activity: impact

► Some estimations availableSome estimations available e.g. Eriksson & Lindegren (2007), Makarov et al. (2009)e.g. Eriksson & Lindegren (2007), Makarov et al. (2009)

► Exoplanet detection by Gaia not affectedExoplanet detection by Gaia not affected Astrometric jitter << 1 MAstrometric jitter << 1 M JJ planet signature planet signature

But predictions must be confirmedBut predictions must be confirmed

► Impact on Gaia astrometry of giant stars ??Impact on Gaia astrometry of giant stars ??

► Impact on future missions (e.g. SIM Lite) ??Impact on future missions (e.g. SIM Lite) ??

► Test: Simultaneous astrometry + Doppler imagingTest: Simultaneous astrometry + Doppler imaging

Stellar activity: Doppler Stellar activity: Doppler imagingimaging

► Line shape is altered by Line shape is altered by starspotsstarspots

► Surface temperature Surface temperature map reconstructionmap reconstruction

► High resolution spectraHigh resolution spectra λλ / / ΔλΔλ ~ 100,000 ~ 100,000 SNR ~ 300SNR ~ 300

► Photometric data usefulPhotometric data useful► Observations during a Observations during a

period period astrometric astrometric signature estimationsignature estimation

Strassmeier (2006)

Stellar activity: observationsStellar activity: observations

► Empirical determination of astrometric signatureEmpirical determination of astrometric signature ~50-100 ~50-100 μμas for nearby giants as for nearby giants Gaia and Gaia and

VLTI/PRIMAVLTI/PRIMA

► Simultaneous Astrometry and Doppler imagingSimultaneous Astrometry and Doppler imaging► Astrometry with GaiaAstrometry with Gaia

Scanning law Scanning law prediction of focal plane transits prediction of focal plane transits Plenty of ground-based telescope time neededPlenty of ground-based telescope time needed

►e.g. 10 transits x 10 observations = 100 spectra per stare.g. 10 transits x 10 observations = 100 spectra per star

► Astrometry with VLTI/PRIMAAstrometry with VLTI/PRIMA Less telescope time needed, e.g. 10 spectra / rotationLess telescope time needed, e.g. 10 spectra / rotation Bright nearby reference star required. Distance ~ 20”Bright nearby reference star required. Distance ~ 20”

Stellar activity: statistical Stellar activity: statistical analysisanalysis

►The astrometric signature The astrometric signature σσpospos depends depends

on the stellar magnitude variability on the stellar magnitude variability σσmm

►Gaia will provide millimag light curvesGaia will provide millimag light curves

►Knowledge on a single object is limited, Knowledge on a single object is limited,

but statistical analysis could be feasiblebut statistical analysis could be feasible

►Trends with mass and evolutionary statusTrends with mass and evolutionary status

5. Summary5. SummaryEarly science Early science

activitiesactivities

Early science: activitiesEarly science: activities

►SimulationsSimulations Inclination angle for RV candidatesInclination angle for RV candidates Candidate selection for RV follow-upCandidate selection for RV follow-up

►ObservationsObservations RV: coeval data for existing RV RV: coeval data for existing RV

candidatescandidates RV: early astrometry planets monitoringRV: early astrometry planets monitoring Gaia + Doppler imaging of active starsGaia + Doppler imaging of active stars PRIMA + Doppler imaging of active starsPRIMA + Doppler imaging of active stars Stellar activity: statistical analysisStellar activity: statistical analysis