PLAnetary Transits and Oscillations of stars

H. Rauer1, C. Catala2, D. Pollacco3, S. Udry4 and the PLATO Team

1: Institut für Planetenforschung, DLR and TU Berlin2: Observatoire de Paris, LESIA

3: Univ. Belfast4: Obs. Geneva

http://www.oact.inaf.it/plato/PPLC/Home.html

M-class mission candidate in ESA Cosmic Vision Program;In competition for launch in 2018

PLATO Science Objective

> measurement of radius and mass, hence of planet mean density

> measurement of age of host stars, hence of planetary systems

Transits: Planetary Parameters• Key Tool

Mostly geometry

radius of planet/star, inclination.

Kepler’s 3rd law => semi-major axis

FF

RPlR

2

Only needed physics: limb darkening

Sun + Jupiter : ~ 1% dip Sun + Earth : ~ 0.01% dip

CoRoT 7bCoRoT 7bKepler 4bKepler 4b

GJ1214bGJ1214b

GJ436bGJ436b

Detection range of transit surveysDetection range of transit surveys

Space surveys

Ground-based

surveysTrES-4b

HAT-P-7b

HD149026b

CoRoT-2b

HAT-P-12b

HAT-P-11b

PLATO Survey of 1RE rocky planets in habitable zones of all late type stars

News:• Now includes M dwarfs• M stars lower intrinsic

brightness (local) and very red

• PLATO can work as faint as I~15-16 mag with little blending in most cases

• 6000 M stars per pointing • RV signal larger

Groundbased follow-up- Vigorous follow-up needed- Most important aspect = radial velocity monitoring

planet confirmation and mass measurement

Planet Distance (AU)

RV Amp. (m/s)

Jupiter 1 28.4

Neptune 0.1 4.8

Neptune 1 1.5

SuperEarth 0.1 1.4

SuperEarth 1 0.5

Earth 1 0.1

- stellar intrinsic « noise »: oscillations, granulation, activity- need to apply proper averaging technique- time consuming- in practice limited to bright stars

PLATO

CoRoT - Kepler

telescope diameter needed to confirm earth-like planet

Asteroseismology• Key ToolPlanet parameters stellar parameters (asteroseismology)

Solar-like stars oscillate in many modes, excited by convection. Sound waves trapped in interior

Resonant frequencies determined by structure: frequencies probe structure gives mass, angular momentum, age

Power spectrum of light curve gives frequencies

Asteroseismology

Inversions + model fitting + consistent , M, , J, age

PLATO will provide:

Large separations M/R3 mean densitySmall separations d02

probe the core age

Uncertainty in Age ~ 10%

Uncertainty in Mass ~ 2%

CoRoT 1.36 +/- 0.04 M

3.90 +/- 0.4 Gyr

8.0 x 10-5 in 1 hr for marginal transit detection

1 R planet transiting a solar-like star at 1 AU - mean of 3 transits

Noise level requirements for PLATO

2.7 x 10-5 in 1 hr for high S/N transit measurement: also required for seismic analysis

The PLATO star samples

mV ≤ 11mV ≤ 11

m <11

≤ 2.7 10-5 / hr

≥ 20,000 cool dwarfs & subgiants

mV ≤ 10-11.5mV ≤ 8

≥ 1,000 / 3,000 cool

dwarfs & subgiants

11 < mV ≤ 13 ≤ 8.0 10-5 / hr

≥ 250,000 cool dwarfs & subgiants

Instrumental Concept

- 32 « normal » cameras : cadence 25 sec- 2 « fast » cameras : cadence 2.5 sec- pupil 120 mm- dynamical range: 4 ≤ mV ≤ 16

Very wide field + large collecting area :multi-instrument approach

on board data treatment: 1 DPU per camera 1 ICU

optical field 37°

4 CCDs: 45102 18m « normal » « fast »

focal planes

FPA

356 mm

S-FPL51

N-KzFS11 CaF2(Lithotec)

S-FPL53

L-PHL1

KzFSN5

164.

6 m

m

optics

fully dioptric, 6 lenses

Orbit around L2 Lagrangian point, 6-year nominal lifetime

Concept of overlapping line of sights

4 groups of 8 cameras with offset lines of sightoffset = 0.35 x field diameter

8 8

8 8

16

16

16 16

2424

2424

32

Optimization of number of stars at given noise level AND of number of stars at given magnitude

37°

50°

Kepler

CoRoT CoRoT

Basic observation strategyObservation strategy:1. two long pointings : 3 years or 2 years2. « step&stare » phase (1 or 2 years) : N fields 2-5 months each

PLATO

PLATO

Kepler

CoRoT CoRoT

>40% of the whole sky !

Basic observation strategyObservation strategy:1. two long pointings : 3 years or 2 years2. « step&stare » phase (1 or 2 years) : N fields 2-5 months each

Assumptions:- 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

Expected number of confirmed planets

lower right corner of the (orbit,mass) plane = terrestrial planets in the HZ, not covered by Kepler, will be explored by PLATO thanks to its priority on bright stars

-

Wagner et al. 2009, also: Valencia et al. 2007

standard error bar

Compare exoplanets with predictions of models with various compositions and structures

error bar dominated by error of host stars characteristics

Impact of radius and mass measurement

-

Wagner et al. 2009, also: Valencia et al. 2007

5%

10%

10%

5%

maximum acceptable error bars

standard error bar

Compare exoplanets with predictions of models with various compositions and structures

Impact of radius and mass measurement

error bar dominated by error of host stars characteristics

- constraints on planet interiors- radii and masses atmospheres- diversity

-

Wagner et al. 2009, also: Valencia et al. 2007

5%

10%

10%

5%

maximum acceptable error bars

PLATO error bar

standard error bar

Compare exoplanets with predictions of models with various compositions and structures

Impact of radius and mass measurement

PLATO: compare Earth-like exoplanets with age scale of Earth

- precision better than timescale planet

evolution

- targets of future characterization

dated by PLATO (Earth-like, but also

Neptunes, hot Jupiters…)

Impact of age measurement

place exoplanetary systems in evolutionary context

MagnetosphereCarbon-silicate cycle

Oxygen riseOzone layer

Proto Earth

Objective: Detect and characterize planetary systems, particularly earth-like in habitable zone

Techniques: detection by transits + asteroseismology of host stars + ground based spectroscopy

Instrument: Multi-telescopes very wide field of view

Targets: > 20,000 bright cool dwarfs (noise < 2.7 10-5 in one hr) > 50,000 bright cool dwarfs (mv<11)

> 6,000 very nearby M dwarfs > 230,000 cool dwarfs (mv<13,noise < 8.0 10-5 in one hr )

Observing strategy: 2 long runs (2-3 years) + several short runs

PLATO: Summary

More than 40% sky coverage