Transcript Basic data of CoRoT-Exo-2b - tls

Schedule of CoRoT
and Kepler
CoRoT
KEPLER
Launch: 27.12.2006
First image: 18.01.2007
First scientific observations:
05.02.2007
First planet detected 87 days
after begin of observations
Launch: 07.03.2009
First image: 16.04.2009
Start of scientific operations:
13.05.2009
87 days after begin of
scientific observations will
be August 8th.
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Searching for extrasolar
planets with CoRoT
(Convection, Rotation et Transites planétaires)
Du cœur des étoiles aux planètes habitables
CoRoT Mission Scientific
Objective
1.) Detecting oscillations of solar like stars
2.) Detecting transiting gaseous planets
3.) Derive radius, mass, density of gaseous
planets to obtain mass-radius relation
4.) Determine frequency of short-period
massive planets.
5.) Mission has fair chance to detect even
rocky planets
Mass: 605 kg
Dimensions: 4.2m wide by 9m high
The satellite
Optical design:
telescope of 27cm aperture
1.2 m focal length
2.3 arsec per pixel
FOV 2.8x1.4 degrees for the Exo-field
The baffle reduces stray-light from earth by
factor 10-13 , however because of the zodical
light, the background flux still is 15
phot/pix/s.
4 CCDs (2048x2048 pixel):
2 for Exo-field, 2 for stellar oscillations
T=-40C, telemetry 1.5 Gbyte/day
Exo field: little spectra (R=4, 100nm/pix)
(40% in red, 30% in green, 30% in blue)
Advantages of space
observations
 Photometric accuracy 10 to 100 times better than with ground
based telescopes. While ground based observations reach a
level of better than 1%, not all nights are perfect. In many nights
this means that the photometric accuracy for all faint stars is
bad. Because all stars are effected at the time, this creates socalled “red-noise”, which has proven to be the big problem of
ground based photometry.
 Continuous light-curves without gaps allow to distinguish spots
from transits.
 CoRoT monitors fields for 150 or 20 days. (long/short runs).
 The sampling is 8 minutes for all stars, if it is discovered that an
object has transit, the frequency is increased to 30 seconds.
That means, each LC has between 3600 and 3x432000 points.
CoRoT database is by far the largest photometric data-base
ever obtained.
 Three colour photometry allows to exclude eclipsing binaries
within the photometric mask.
Noise sources
Background noise (Zodiacal light)
Readout noise
Jitter noise
“Breathing noise” due to tiny changes of the
temperature of the telescope structure
Photometric accuracy 10-5 to a few times10-4.
Launch : 27.12.2006
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Orbital parameters
Semi major axis 7276.3 km
Orbital inclination 90 degrees
Eccentricity 0.00127
The eyes of CoRoT
Observations in
pace versus
ground:
Observations in space allow
continuous monitoring. That
means we can detect transit of
planets with much longer
orbital period. Here is a
comparison with SuperWASP,
which is located at the island
of La Palma.
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The other big advantage of observations in space is that
spots and transits can easily be distinguished, and we get
the rotation rate of the star for free!
Stars that are being
observed
In order to get statistically meaningful results,
we have to determine the spectral types
(mass) of all the stars that we are looking at.
A first analysis of the CoRoT data shows that
ground based observations detect only 10%
of the hot Jupiters that are in principle within
reach. This is an effect of the red noise and
very often also the day/night gaps of ground
based observations.
How do we determine the spectral types of
1000nds of stars?
Magnitude range
Why do we need spectroscopy?
The superb photometric archive created by CoRoT
allows us to address a large variety of different scientific
questions.
However, for all these projects we need to know what
kind of star we are looking at.
Teff , Lum. Class, log(g), [Fe/H], Av , RV, vsin(i), stellar
activity level, age, etc.
We don't want to waste time!
Multi Object Spectroscopy (MOS)
AAOmega observations
Gratings: 580V + 385 R
Blue: 3600-5700 AA;
R=1300
Red: 5700-8900 AA;
R=1300
Settings:
AAOmega spectrograph:
392 fibers
(maximum: 367 stars + 25
sky (+ 7 feducials)
Observing time per field
about 45 minutes.
We observed 56 fields
(about 20000 spectra)
How do we determine the
Spectral Type from the lowresolution spectra?
– Method => we fit each observed spectrum with a
suitable grid of templates, taking the amount of
extinction along the line of sight into account.
– What is needed? => Library of flux-calibrated and
de-reddened stellar spectra covering our spectral
range.
An example
(observations: black, template: green)
.......another example......
.......another example......
.......the last one!
Comparing photometry and
AAOmega - spectroscopy I:
dwarfs (red: photometry, blue spectroscopy)
Comparing photometry and
AAOmega - spectroscopy II:
giants (red: photometry, blue spectroscopy)
CoRoT is a space telescope but we still
need lots of observations with groundbased telescopes:
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Spectra taken with mulit-object spectrograph: Is the star a giant or dwarf, what
is the mass of the star?
Is the transit really on the star, or is there an eclipsing binary within the
photometric mask (on/off photometry with high resolution).
Could the object be a triple star, with two faint companions eclipsing each other?
(infrared spectra with high spectra resolution needed)
Determine the mass and the radius of the host star accurately (optical spectra
with high spectral resolution and high signal to noise needed, in practise 2 to 4
hours on 8-m-telescope)
Measure the mass of the planet (can be as much as 10 nights on a 4-m-class
telescope)
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OGLE 56
The first one: CoRot-Exo-1b
CoRoT-Exo-1b
Star: 0.95 +/-0.16 Msun
Star: 1.11+/-0.05 Rsun
Star: F9V (13.6 mag)
Planet: 1.03+/-0.12 Mjup
Planet: 1.49+/-0.08 Rjup
Orbital period: 1.509 days
CoRoT-Exo-1b: first planet detected in
reflected light in the optical regime:
nigthside: dark
dayside albedo ≤20% (gas giants in solar system 41 to 52%)
A planet orbiting a
young, active star
A planet of a young star:
 Star: 0.97 +/-0.06 Msun
 Star: 0.90+/-0.02 Rsun
 Star: G7V (12.6 mag)
 Planet: 3.31+/-0.16 Mjup
 Planet: 1.47+/-0.03 Rjup
 Orbital period: 1.742 days
=7.1±5.00
S-index 0.511 (sun 0.179, Eps Eri 0.496)

CoRoT-Exo-2b :log(R’HK)= 4.36-4.43
Dots, squares: Hyades
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Crosses: Pleiades
Plus:CoRoT- Exo-2b
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CoRoT-Exo-2b
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An interesting aspect:
 We know that the eccentricity is very small (possibly
< 0.000046)
 This means that the orbit circularized very quickly.
 This means the tidal interaction must be very strong.
 The planet will spiral into the star!
NGC 2264
(distance 760pc, age 3 Myr)
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A brown dwarf orbiting a
normal star
 Star: 1.27 +/-0.05 Msun
 Star: 1.305+/-0.02 Rsun
 Star: G0V (13.3 mag)
 Planet: 20.2 Mjup
 Planet: 0.829 Rjup
 Orbital period: 4.25 days
A transiting planet with a relatively long
orbital period
 Star: 1.10 +/-0.02 Msun
 Star: 1.15+/-0.02 Rsun
 Star: F8V (13.7 mag)
 Planet: 0.73 Mjup
 Planet: 1.17+/-0.05 Rjup
 Orbital period: 9.202 days
Mass period-relation
KEPLER System
Characteristics:
 Spacebased Photometer: 0.95-m aperture
 Primary mirror: 1.4 meter diameter, 85% light weighted
 Detectors: 95 mega pixels (42 CCDs with 2200x1024
pixels)
 Field of view 105 square degress
 Bandpass: 430-890 nm FWHM
 Dynamic range: 9th to 16th magnitude stars
 Fine guidance sensors: 4 CCDs located on science focal
plane
 Attitude stability: <9 milli-arcsec, 3 sigma over 15
minutes.
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Mission Characteristics:
 Continuously point at a single star field in CygnusLyra region except during Ka-band downlink.
 Roll the spacecraft 90 degrees about the line-of-sight
every 3 months to maintain the sun on the solar
arrays and the radiator pointed to deep space.
 Earth-trailing orbit (heliocentric orbit with 372.5 day
period)
 Monitor 100,000 main-sequence stars for
planetsMission lifetime of 3.5 years extendible to at
least 6 years
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Kepler Mission Scientific Objective:
 1.Determine the percentage of terrestrial and larger planets
there are in or near the habitable zone of a wide variety of stars;
 2.Determine the distribution of sizes and shapes of the orbits of
these planets;
 3.Estimate how many planets there are in multiple-star systems;
 4.Determine the variety of orbit sizes and planet reflectivities,
sizes, masses and densities of short-period giant planets;
 5.Identify additional members of each discovered planetary
system using other techniques; and
 6.Determine the properties of those stars that harbor planetary
systems.
Kepler: first light: March 6th 2009
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