Transits from Space: Transits from Space: 1. The CoRoT mission1. The CoRoT mission

Why do Transit searches from Space?

1. No scintillation noise → One can reach the photon limit

2. No atmospheric extinction → Less false positives

3. Continous temporal coverage → if a stars shows a transit you will find it!

In short: the light curves are of better quality, have better temporal coverage so you can find smaller transits and transits in long period orbits

Disadvantages of Space

1. If the launch fails you do not get a second chance

2. If your instrument breaks, you cannot fix it

3. Space environment introduces different problems in the light curve analysis

4. It is expensive!

The CoRoT Mission (CNES)COnvection ROtation and Planetary Transits

• Goals: exoplanets + astroseismology• Polar Earth orbit• 27 cm Telescope w/ 4 CCD detectors• 2.8° x 2.8° field-of-view• Max 150 days observing runs• Launched: 27th December 2006• Participation from: F, A, B, D, E, ESA, Brasil• Duration 6+ years

CoRoT was successfully launched from Baikanur on 27 December 2006

630 kg + 1000 kg water

The Launch Profile of CoRoT:

if (WWIII) then

White House., U.S.A

else if (corot) then

orbit

end if Washington, D.C.

orbit

Baikanur.

• a = 7278.475 km

• e = 0.00169

• i = 89.984

The Orbit of CoRoT

• a = 7278.189 km

• e = 0.00162

• i = 90.002

• Porb = 6176–6195 s

→ The orbit is nearly perfect

Goal Reality

The eyes of CoRoT

Movie time!

*

*

**

*

faint stars (11-16)targets / CCD

main target

secondary target

*

**

* Field of view

Asteroseismologie channel

Exoplanets channel

Focal Plane:

PSF: Astroseismology

PSF: exo-Planet

CoRoT-Mission: Focal Plane

Sismo

ExoWindow

Thermal link

PRISM

MLI

SHIELDING

Optics

ElectronicsFlex rigid

Radiator

Thermalmanagement

Flex rigidElectronics

2.8o x 1.4o

Seismo field:

~10 targets/CCD 5 < V < 9.5

Exofield field:

~ 6000 targets/CCD 11 < V < 16

• CoRoT does not download the entire CCD images, but only the data in an aperture centered on the star

• 32 sec integrations. On-board summing of data in aperture plus binning to 512 s exposure time. On-board processing returns only integrated flux in aperture.

• 400 „oversampled“ apertures with 32 s sampling. This can be changed during the run

• ~ 40 imagettes. Data from the full image inside the aperture is sent back

• Chromatic information (CoRoT r,g,b) for only about ½ of the brightest stars (chromatic and monochromatic light curves)

• ~6000 apertures per exo-CCD. If more stars are in the field one has to decide before which stars to observed (proposals)

Exofield Information

The South Atlantic Anomaly (SAA)

Duty Cycle: Not completely continuous coverage

• ~ 6% of the data is lost due to the SAA

• other „random events“ cause 1-2% loss

• Duty cycle ~ 92%

Sample Light Curves from the Exofield Showing Stellar Variability

So is all this effort worth going to Space?

An OGLE transit discovery (ground-based)

A CoRoT transit discovery

The CoRoT Ground-based Follow-up Effort

CoRoT only finds transit „candidates“. An extensive ground-based effort is required to confirm that this is indeed a planet.

For Space-based transit searches, Ground-based observations are „part of the Mission“

But before the ground-based follow up starts one needs to do the best possible analysis on the light curve to give the best candidates. Much information comes from the light curves

e.g.:

Is the transit too long : probably a giant

Do you see a secondary? Probably an eclipsing binary

Problem : The size of the CoRoT aperture

The CoRoT PSF can have up to 0-20 background stars whose light contaminates the light of the primary star. The first step is to identify which star is making the transit

We will go through the necessary procedures to confirm the planet for the case of CoRoT-7b!

Status of CoRoT

• CoRoT has been operating for over 4 years

• Over 110,000 stars have been observed

• 24 Transiting Planets have been discovered

• CoRoT mission has been extended for 3 years until the end of 2013

• On 7 March 2009 CoRoT lost DPU1 (Data Processing Unit) that controlled one Exoplanet and one Seismo CCD. CoRoT continues to work well, but only getting data on ½ the original number of stars

On 6 March 2009 NASA Launched Kepler

The first six CoRoT planets:

CoRoT-1b CoRoT-3bCoRoT-2b

Deleuil et al. 2008Barge et al. 2008 Alonso et al. 2008

CoRoT-4b

Agrain et al. and Moutou et al. 2008

CoRoT-5b

Rauer et al., A&A 2009

CoRoT-6b

Fridlund et al., A&A 2009

P: 1.5089557 days

R: 1.49 RJ

m: 1.03 MJ

: 0.38 cgs

P: 1.5089557 days

R: 1.49 RJ

m: 1.03 MJ

: 0.38 cgs

P: 1.742996 days

R: 1.465 RJ

m: 3.31 MJ

: 1.3 cgs

P: 1.742996 days

R: 1.465 RJ

m: 3.31 MJ

: 1.3 cgs

P: 4.2568 days

R: 1.01 RJ

m: 21.66 MJ

: 26.4 cgs

P: 4.2568 days

R: 1.01 RJ

m: 21.66 MJ

: 26.4 cgs

P: 9.20205 daysR: 1.19 RJ

m: 0.72 MJ

: 0.5 cgs

P: 9.20205 daysR: 1.19 RJ

m: 0.72 MJ

: 0.5 cgs

P: 4.0384 daysR: 1.28 RJ

m: 0.459 MJ

: 0.22 cgs

P: 4.0384 daysR: 1.28 RJ

m: 0.459 MJ

: 0.22 cgs

P: 8.88 days R: 1.15 RJ

m: 3.3 MJ

: 2.3 cgs

P: 8.88 days R: 1.15 RJ

m: 3.3 MJ

: 2.3 cgs

And the next 6

CoRoT-7b

Deleuil et al. 2008Barge et al. 2008

CoRoT-9bCoRoT-8b

CoRoT-11bCoRoT-10b CoRoT-12b

Gandolfi et al. 2010Bonnono et al. 2010

Borde et al. 2010

P: 0.85 days

R: 0.14 RJ

m: 0.02 MJ

: 10.1 cgs

P: 0.85 days

R: 0.14 RJ

m: 0.02 MJ

: 10.1 cgs

P: 95 days

R: 1.05 RJ

m: 0.84 MJ

: 0.9 cgs

P: 95 days

R: 1.05 RJ

m: 0.84 MJ

: 0.9 cgs

P: 6.2 days

R: 0.57 RJ

m: 0.22 MJ

: 1.6 cgs

P: 6.2 days

R: 0.57 RJ

m: 0.22 MJ

: 1.6 cgs

P: 13.2 days

R: 0.97 RJ

m: 2.75 MJ

3.7 cgs

P: 13.2 days

R: 0.97 RJ

m: 2.75 MJ

3.7 cgs

P: 3.0 days

R: 1.43 RJ

m: 2.33 MJ

1.0 cgs

P: 3.0 days

R: 1.43 RJ

m: 2.33 MJ

1.0 cgs

P: 2.8 days

R: 1.44 RJ

m: 0.91 MJ

0.8 cgs

P: 2.8 days

R: 1.44 RJ

m: 0.91 MJ

0.8 cgs

Gillon et al. 2010

CoRoT-13b

Bouchy et al. 2011Cabrera et al. 2011

CoRoT-15bCoRoT-14b

P: 4.0 days

R:0.88 RJ

m: 1.31 MJ

: 2.3 cgs

P: 4.0 days

R:0.88 RJ

m: 1.31 MJ

: 2.3 cgs

P: 3.1 days

R: 1.12 RJ

m: 63 MJ

: 59 cgs

P: 3.1 days

R: 1.12 RJ

m: 63 MJ

: 59 cgs

P: 1.5 days

R: 1.1 RJ

m: 7.6 MJ

: 7.3 cgs

P: 1.5 days

R: 1.1 RJ

m: 7.6 MJ

: 7.3 cgs

Tingley et al. 2011

In preparation: CoRoT-16b – 24b

RM anomaly

CoRoT-1b and its Rossiter-McLaughlin effect

CoRoT-2b : A Hot Jupiter around an active star

Alonso et al. 2008

P: 1.742996 days

R: 1.465 RJ

m: 3.31 MJ

: 1.3 cgs

P: 1.742996 days

R: 1.465 RJ

m: 3.31 MJ

: 1.3 cgs

CoRoT-3b : The First Transiting Brown Dwarf

P: 4.2568 days

R: 1.01 RJ

m: 21.66 MJ

: 26.4 cgs

P: 4.2568 days

R: 1.01 RJ

m: 21.66 MJ

: 26.4 cgs

Planets

Pressure support provided by electron degeneracy pressure, no fusion (M < 13 MJup)

Stars

Hydrogen fusing in hydrostatic equilibrium

(M > 80 MJup)

Brown Dwarfs

Pressure support provided by electron degeneracy pressure, short period of deuterium burning (13 < M < 80 MJup)

Modified From H. Rauer

CoRoT-3b : Radius = Jupiter, Mass = 21.6 Jupiter

CoRoT-1b : Radius = 1.5 Jupiter, Mass = 1 Jupiter

OGLE-TR-133b: Radius = 1.33 Jupiter, Mass = 85 Jupiter

CoRoT-1b

CoRoT-3b

OGLE-TR-133b

CoRoT-9b, the first well-known temperate exoplanet

- longest period planet detected by transits (at time of announcement)

- moderate temperate gas giant

- low eccentricity, thus moderate temparature variations along orbit

Deeg et al., Nature 2010

CoRoT-9b: - R = 1.05 RJ

- P = 95.274 d- a = 0.407 AU - e = 0.11- m = 0.84 MJ

- Density = 0.9 gm cm–3

- Teff = 250 – 400 K

In spite of rotational modulation due to spots with a photometric amplitude of ~2% one can find…

CoRoT-7b : The Crown Jewel of CoRoT

0.035%

CoRoT-7b : The Crown Jewel of CoRoT

Transit Curve

CoRoT-7b: - Rpl = 1.6 R

P = 0.8536 d

- a = 0.017 AU

- m = 7.4 MEarth

CoRoT-7b: - Rpl = 1.6 R

P = 0.8536 d

- a = 0.017 AU

- m = 7.4 MEarth

Leger et al., 2009; Queloz et al. 2009, Hatzes et al. 2010

The „Sherlock Holmes Proof“

Or why we knew CoRoT-7b was a planet before we had radial velocity measurements.

Hypothesis #1: The transit is caused by a contaminant

On-off photometry established that nearby stars could not account for transit depth of CoRoT-7

Hypothesis #2: The star is really a giant star

No, it is a G8 Main Sequence Star

Hypothesis #3: There is a faint very nearby background eclipsing binary star that causes the eclipse

Adaptive Optics Imaging shows no very close companions

Hypothesis #4: A Hiearchical Triple system with 2 eclipsing M-dwarfs,

Short period M dwarfs are very active and we would have seen Ca II emission from the binary stars and X-ray emission

Hypothesis #5:The transit is caused by a background (or binary companion) M dwarf with a transiting Hot Jupiter

1. Giant planets to M dwarfs are rare

2 The M dwarf is bright in the Infrared. High resolution infrared spectral

observations show no evidence for an M dwarf companion.

There are only two astronomical bodies that have a radius ~ 1 REarth:

1. White Dwarf

2. A terrestrial planet

White Dwarfs have a mass of ~ 1 Solar Mass, so the radial velocity amplitude should be ~ 100s km/s. This is excluded by low precision radial velocity measurements.

„Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”

- Sherlock Holmes

44

RV

(m

/s)

JD

CoRoT-7 is an active star with an RV jitter twice that the expected RV planet from the star

Prot = 23 d

A carefull analysis shows that you can extract the planet signal from the activity signal

O–C = 1.7 m/s

RV = 1.8 m/s

CoRoT-7b

P = 0.85 d

Mass = 7.3 MEarth

50

Tsurface ~ 1800 – 2600 CA lava ocean planet?

Art predicting reality?

There is a popular German SF-series where a Lava planet - called Daa’mur – populated by exotic life forms which evolved from thermophile. Therefore its funny that the first transiting rocky planet (CoRoT-7b) fits in such a Lava-planet category.

The CoRoT-7 Planetary System

P = 3.7 Days

Mass = 12.4 ME

CoRoT-7c

P = 9 Days

Mass = 16.7 ME

CoRoT-7d

The analysis of the radial velocity measurements reveals the presence of 2 additional planets. So why do these not transit?

10o Only CoRoT-7b Transits

CoRoT-7b,c,d

Mercury

MarsVenus

Earth

Moon

CoRoT-7b

1

2

3

4

5

7

10

0.2 0.4

Radius (REarth)

(g

m/c

m3)

0.6 0.8 1 1.2 1.4 1.6 1.8 2

Kepler-10b

No iron

Earth-likeIron enriched

From Diana Valencia