PLAnetary Transits and Oscillations of stars Thierry Appourchaux for the PLATO Consortium

- Science Objectives - Instrumental Concept - Expected Performances - Conclusion Outline

Science Objectives (1/2) Understand formation and evolution of planetary systems (= planets + host stars) Understand evolution toward habitability Complete statistical study of exoplanetary systems Identification and characterisation of planetary systems - including planets of all masses and sizes on various orbits - around stars of all types and ages - including seismic characterization of planet host stars - in particular rocky planets in habitable zone of solar-like stars

Goal: detect and characterise exoplanets - measurement of radius and mass, hence of mean density - estimate of age Method: transit search AND seismic analysis on the same stars - photometric transits : R p /R s (R s known thanks to Gaia + seismology) - radial velocity follow-up : M p /M s - seismic analysis of host stars : R s, M s, age Tool: - ultra-high precision, long, uninterrupted CCD photometric monitoring of very wide samples of bright stars: CoRoT - Kepler heritage Science Objectives (2/2)

- seismically determined masses and radii of host stars are required to derive useful constraints on planetary interiors - will give us the opportunity to study diversity of planets : planets with same radius and different masses - seismically determined exoplanetary ages will be used to place exoplanets in an evolutionary context Why a seismic analysis of planet host stars? - Wagner et al. 2009, also: Valencia et al % 10% 5% maximum acceptable error bars PLATO error bar (with seismology + Gaia) standard error bar (no seismology) We want to compare exoplanet characteristics to model predictions with various compositions and structures

PLATO target samples > 20,000 bright (~ m V ≤11) cool dwarfs/subgiants (>F5V&IV): exoplanet transits AND seismic analysis of their host stars AND ultra-high precision RV follow-up noise < in 1hr for 3 years > 250,000 cool dwarfs/subgiants (~ m V ≤13) exoplanet transits + RV follow-up >1,000 very bright (m V ≤8) cool dwarfs/subgiants for 3 years >3,000 very bright (m V ≤8) cool dwarfs/subgiants for >5 months exoplanets around bright and nearby stars Main focus of PLATO: Bright and nearby stars !! PLATO… is watching you ! noise < in 1hr for 3 years > 5,000 (3 years) + 5,000 (5 months) nearby M-dwarfs (m V ≤15-16) noise < in 1hr

Noise requirements: transit search noise requirement ≤ 2.7 x in 1 hr for high S/N transit measurement for transit search :≤ 8.0 x in 1 hr for marginal transit detection simulation: 1 R  planet transiting a solar-like star at 1 AU - mean of 3 transits transit well characterized transit detectable

Noise requirements: seismic analysis ≤ 2.7 x in 1 hr frequency (  Hz) power (ppm 2 /  Hz) CoRoT HD m V = days PLATO equivalent m V = 9.6 same data noise 2.7 x per hr PLATO equivalent m V = 11.1 oscillation spectrum still distinguishable although affected by noise

Instrumental Concept New design - 32 « normal » cameras : cadence 25 sec - 2 « fast » cameras : cadence 2.5 sec - pupil 120 mm - huge dynamical range: 4 ≤ m V ≤ 16 !! Very wide field + large collecting area : multi-instrument approach FPA 356 mm S-FPL51 N-KzFS11 CaF2 (Lithotec) S-FPL53 L-PHL1 KzFSN mm optics fully dioptric, 6 lenses Orbit around L2 Lagrangian point, 6-year nominal lifetime + possible extension optical field 37° 4 CCDs:  m « normal » focal planes « normal » FPA« fast » FPA

Concept of overlapping line of sight 4 groups of 8 cameras with offset lines of sight baseline offset = 0.35 x field diameter (k=0.35) Optimization of number of stars at given noise level AND of number of stars at given magnitude 37° 50°

>50% of the sky ! CoRoT Kepler PLATO Observation strategy: 1. two long pointings : 3 years + 2 years or 2 years + 2 years 2. « step&stare » phase (1 or 2 years) : N fields 2-5 months each Sky coverage

Expected noise level jitter/PRNU jitter/confusion + background photon noise photon noise dominant noise calculated for 32 cameras noise in 1 hr (ppm)

Performances of the long pointing phases as a function of noise level as a function of magnitude PLATO (4360 deg 2 )Kepler (100 deg 2 ) noise level (ppm/√hr) nb of cool dwarfs & subgiants m V range nb of cool dwarfs & subgiants mVmV 2722, , , , , ,490111,30011 spec 20,000 spec 250,000 spec 1,000 maximum noise level for seismic analysis of solar-like stars & earth-like planet transit measurement numbers of cool dwarfs and subgiants observable by PLATO and Kepler, for various photometric noise levels and various magnitudes, during long monitoring sequences Note that solar-like oscillations will be measurable for more then 20,000 dwarfs!

Scientific Impact Expected number of detected transiting planets by PLATO and Kepler: - each star has one and only one planet in each cell - planet is detected if a transit signal AND a radial velocity signal are measured - intrinsic stellar « noise » is taken into account numbers in white are expected numbers of detections by PLATO and Kepler in each cell: Kepler contributions are represented by the green sectors. The lower right corner (telluric planets in the HZ), not covered by Kepler because of the overwhelming difficulty of FU observations, will be explored by PLATO thanks to its focus on bright stars. Note that all planets detected by PLATO referred to in this diagram will have their host star fully characterized by asteroseismology Orbit semi-major axis in units of habitable zone

Conclusion Building on CoRoT and Kepler experience, - PLATO is a next generation planet finder and characterizer - its focus will be mainly on bright and nearby targets - it will detect and characterize significant numbers of telluric planets in the habitable zone - PLATO will provide seismic analysis of planet host stars and of a very large sample of stars of all types and ages - PLATO will represent a major step forward after the pioneering CoRoT and Kepler missions