AFS Lecture 4

COROT, COnvection, ROtation & Transits exoplanétaires

Objectives COROT had two objectives: - Searching for planets of the a type similar to our own Earth (so far unknown around other stars - Studying the inner parts of stars (for the first time) by measuring the changes in light output caused by acoustical sound waves travelling through the star. COROT was essentially a very precise light-meter (photometer). COROT could measure changes in stellar flux of better than 1 part in ! (For brightest objects a few ppm) It could discriminate between colours ==> COROT could tell what the cause of variations in stellar flux were. Either: a) Intrinsic changes caused by activity or by waves travelling through the star b) Occultations by a (small) planetary body passing in front of the star

Close-in planetary objects could be discovered in „alarm mode“ Very high S/N of data transit events visible at N1 level CoRoT-Exo-4b

CoRoT PSF

basic data reduction How CoRoT planet detection works… observations Follow-up observations Confirmed planets data reduction transit candidate list Follow-up observations Confirmed planets transit alarm!  Preliminary candidate list (large planets!) Giant (and even small ones) planets can be detected already in „alarm mode“!

Follow-up to transits is ground based In CoRoT it is complex and comprehensive Consists of spectroscopy (high resolution, high s/n) for – Stellar modelling (T eff, log g, [Fe/H], v sin i *, V mic, V mac – Radial velocity determination  Planetary mass * v sin i * – Finding contaminant stars within PSF

How to determine the effective temperature of a star

For Solar Type stars there are two methods in Use: – By calculating the shape of the Balmer line wings – By using the equivalent widths of a large number of Fe I and Fe II lines

T eff CoRoT-2 is 5330K+/-70K (internal error)

T eff CoRoT-6 is 5926K+/-100K (internal error)

Determine the equivalent widths of a large number of Fe I and Fe II lines The equivalenth width is the width a line would have if it had 100% absorption and covering the same area as the “real” line. Area proportional to number of absorbing ions After T eff we must determine the value of g (or rather log g). This  The estimates the mass of the star

The „first 4“! CoRoT-Exo-1b CoRoT-Exo-3b CoRoT-Exo-4b CoRoT-Exo-2b Deleuil et al Barge et al Alonso et al Agrain et al. and Moutou et al CoRoT-Exo-1b: P: d r: 1.49 R J m: 1.03 M J The star: G0V V = 13.6 mag CoRoT-Exo-4b: P: d r: 1.19 R J m: 0.72 M J The star: F0V V=13.7 mag CoRoT-Exo-2b: P: d r: R J m: 3.31 M J The star: K0V V=12.6 mag CoRoT-Exo-3b: P: d r: 1.01 R J m: M J The star: G0V V = 13.3 mag

The „next two“ CoRoT-Exo-5bCoRoT-Exo-6b

Transiting planets around variable stars Alonso et al Observations made during the first „long run“ of CoRoT of 152 days duration ~ flux measurements with 512 s (1. week) and then 32 s sampling The star shows periodic variation over several days due to surface spots The planet: Period: days Radius: / R Jup Mass: 3.31+/-0.16 M Jup The star: Type: G7 Magnitude: V=12.6 mag Mass: 0.97+/-0.06 M sun „Discovery space“ for CoRoT

Cleaned and normalised  Raw lightcurve of 144d, demonstrating a rotation period of 22-23d CoRoT-7b First terrestrial planet found outside solar system…

No sign of any transit in‘raw‘ light curve

Extracted light curves in color (top) and white light (bottom) Detection of very small planet signature! Period 20.2h if a planet the Radius = 1.6 R Earth

Lightcurve implies a small planet but it could be a background object or a grazing occultation of a binary: Solved by photometry and spectroscopy PSF of 7b  Contaminants Solution to this : On/Off photometry from the ground of potential contaminants Exclude other possibilities

Workhorses: Photometry, IAC, CFHT, AO Imaging: NACO, CRIRES We need to search for very faint and close by contaminants. For this we use adaptive optics in the near infra-red.

37 Finally after several months 110 CoRoT-7 radial velocity observations produce a curve

Small planet

Medium planet

Large planet

The star and its planets Stellar type: G9V Stellar mass: 0.91 M Sun Stellar radii: 0.82 R Sun Mass 7b: 8 M Earth Radii 7b: 1.6 R earth P 7b: 20.2h Mass 7c: ~ 10 M Earth Radii 7c: Unknown P7c: 3.4d Density 7b: 10+/-2 g cm -3

Close-in „small“ objects could even be discovered in „alarm mode“ The small planet: CoRoT turns out to be the transit with smallest radius – CoRoT-7b First planet under 11 Earth masses with both mass and radius estimate Very likely only one out of 3 planets in this system – a ‚packed‘ system Evidence for a ‚rocky‘ world as ´Earth-like‘ as Earth, Venus and Mercury – at least as far as is concerned

44 CoRoT-9b Temperate = 250K-430K 0.84 M jup Density = 0.94 g cm -3 Circular orbit, 95d Distance = 460 pc G3V Has been checked for the presence of a moon – No signs yet!

CoRoT has today found and published > 35 new planets The latest to be fully ready for publication is CoRoT-32b – The youngest planet yet CoRoT ceased operations due to a technical fault on 2 November 2012 – two days after having been extended for 3 more years of operations Between 15 and 30 new planets are expected within the material we already have – if somebody bothers to carry out the follow-up. This is going to be difficult since all of the targets are faint N.B. If we had applied the same criteria as NASA’s Kepler mission we would already have had a number of more ‘confirmed’ planets

NASA’s Kepler mission – most successful planet finder March 6, 2009

NASA’s Kepler mission – most successful planet finder

A Kepler light curve is a beautiful thing….

NASA’s Kepler mission – most successful planet finder

50 Kepler-10 Light Curve

Period =.84 days Period = days

Kepler asteroseismology Blow-up showing l=0,1,2 P-modes in Hat-P-7  0 for l = 0,1,2; filled symbols is data, open is model 3

Kepler asteroseismology Kepler result is following: Planet parameters are now known to 50%!!!

54 Stellar Properties Kepler-10 G4V Mass = 0.90 Radius = 1.06 R Age > 8 Gyr Distance = 560 Light-years

THE END