778 research outputs found
Introduction
This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered
New planetary and EB candidates from Campaigns 1-6 of the K2 mission
With only two functional reaction wheels, Kepler cannot maintain stable
pointing at its original target field and entered a new mode of observation
called K2. Our method is based on many years of experience in planet hunting
for the CoRoT mission. Due to the unstable pointing, K2 light curves present
systematics that are correlated with the target position in the CCD. Therefore,
our pipeline also includes a decorrelation of this systematic noise. Our
pipeline is optimised for bright stars for which spectroscopic follow-up is
possible. We achieve a maximum precision on 6 hours of 6 ppm. The decorrelated
light curves are searched for transits with an adapted version of the CoRoT
alarm pipeline. We present 172 planetary candidates and 327 eclipsing binary
candidates from campaigns 1, 2, 3, 4, 5 and 6 of K2. Both the planetary
candidates and eclipsing binary candidates lists are made public to promote
follow-up studies. The light curves will also be available to the community.Comment: 22 pages. 5 figures, 4 tables, Accepted for publication in A&
The CoRoT Exoplanet program : status & results
The CoRoT satellite is the first instrument hunting for planets from space.
We will review the status of the CoRoT/Exoplanet program. We will then present
the CoRoT exoplanetary systems and how they widen the range of properties of
the close-in population and contribute to our understanding of the properties
of planets.Comment: 10 pages, Proceeding of Haute Provence Observatory Colloquium (23-27
August 2010
PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance
A large fraction of the smallest transiting planet candidates discovered by
the Kepler and CoRoT space missions cannot be confirmed by a dynamical
measurement of the mass using currently available observing facilities. To
establish their planetary nature, the concept of planet validation has been
advanced. This technique compares the probability of the planetary hypothesis
against that of all reasonably conceivable alternative false-positive (FP)
hypotheses. The candidate is considered as validated if the posterior
probability of the planetary hypothesis is sufficiently larger than the sum of
the probabilities of all FP scenarios. In this paper, we present PASTIS, the
Planet Analysis and Small Transit Investigation Software, a tool designed to
perform a rigorous model comparison of the hypotheses involved in the problem
of planet validation, and to fully exploit the information available in the
candidate light curves. PASTIS self-consistently models the transit light
curves and follow-up observations. Its object-oriented structure offers a large
flexibility for defining the scenarios to be compared. The performance is
explored using artificial transit light curves of planets and FPs with a
realistic error distribution obtained from a Kepler light curve. We find that
data support for the correct hypothesis is strong only when the signal is high
enough (transit signal-to-noise ratio above 50 for the planet case) and remains
inconclusive otherwise. PLATO shall provide transits with high enough
signal-to-noise ratio, but to establish the true nature of the vast majority of
Kepler and CoRoT transit candidates additional data or strong reliance on
hypotheses priors is needed.Comment: Accepted for publication in MNRAS; 23 pages, 11 figure
Activity modelling and impact on planet’s parameters: The case of CoRoT-7
International audienc
Improved parameters of seven Kepler giant companions characterized with SOPHIE and HARPS-N
Radial-velocity observations of Kepler candidates obtained with the SOPHIE
and HARPS-N spectrographs have permitted unveiling the nature of the five giant
planets Kepler-41b, Kepler-43b, Kepler-44b, Kepler-74b, and Kepler-75b, the
massive companion Kepler-39b, and the brown dwarf KOI-205b. These companions
were previously characterized with long-cadence (LC) Kepler data. Here we aim
at refining the parameters of these transiting systems by i) modelling the
published radial velocities (RV) and Kepler short-cadence (SC) data that
provide a much better sampling of the transits, ii) performing new spectral
analyses of the SOPHIE and ESPaDOnS spectra, and iii) improving stellar
rotation periods hence stellar age estimates through gyrochronology, when
possible. Posterior distributions of the system parameters were derived with a
differential evolution Markov chain Monte Carlo approach. Our main results are
as follows: a) Kepler-41b is significantly larger and less dense than
previously found because a lower orbital inclination is favoured by SC data.
This also affects the determination of the geometric albedo that is lower than
previously derived: Ag < 0.135; b) Kepler-44b is moderately smaller and denser
than reported in the discovery paper; c) good agreement was achieved with
published Kepler-43, Kepler-75, and KOI-205 system parameters, although the
host stars Kepler-75 and KOI-205 were found to be slightly richer in metals and
hotter, respectively; d) the previously reported non-zero eccentricities of
Kepler-39b and Kepler-74b might be spurious. If their orbits were circular, the
two companions would be smaller and denser than in the eccentric case. The
radius of Kepler-39b is still larger than predicted by theoretical isochrones.
Its parent star is hotter and richer in metals than previously determined.
[ABRIDGED]Comment: 17 pages, 9 figures, accepted for publication in Astronomy and
Astrophysic
PASTIS: Bayesian extrasolar planet validation II. Constraining exoplanet blend scenarios using spectroscopic diagnoses
The statistical validation of transiting exoplanets proved to be an efficient
technique to secure the nature of small exoplanet signals which cannot be
established by purely spectroscopic means. However, the spectroscopic diagnoses
are providing us with useful constraints on the presence of blended stellar
contaminants. In this paper, we present how a contaminating star affects the
measurements of the various spectroscopic diagnoses as function of the
parameters of the target and contaminating stars using the model implemented
into the PASTIS planet-validation software. We find particular cases for which
a blend might produce a large radial velocity signal but no bisector variation.
It might also produce a bisector variation anti-correlated with the radial
velocity one, as in the case of stellar spots. In those cases, the full width
half maximum variation provides complementary constraints. These results can be
used to constrain blend scenarios for transiting planet candidates or radial
velocity planets. We review all the spectroscopic diagnoses reported in the
literature so far, especially the ones to monitor the line asymmetry. We
estimate their uncertainty and compare their sensitivity to blends. Based on
that, we recommend the use of BiGauss which is the most sensitive diagnosis to
monitor line-profile asymmetry. In this paper, we also investigate the
sensitivity of the radial velocities to constrain blend scenarios and develop a
formalism to estimate the level of dilution of a blended signal. Finally, we
apply our blend model to re-analyse the spectroscopic diagnoses of HD16702, an
unresolved face-on binary which exhibits bisector variations.Comment: Accepted for publication in MNRA
III.2 Activity modelling and impact on planet’s parameters
This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered
SOPHIE velocimetry of Kepler transit candidates VI. An additional companion in the KOI-13 system
We report the discovery of a new stellar companion in the KOI-13 system.
KOI-13 is composed by two fast-rotating A-type stars of similar magnitude. One
of these two stars hosts a transiting planet discovered by Kepler. We obtained
new radial velocity measurements using the SOPHIE spectrograph at the
Observatoire de Haute-Provence that revealed an additional companion in this
system. This companion has a mass between 0.4 and 1 Msun and orbits one of the
two main stars with a period of 65.831 \pm 0.029 days and an eccentricity of
0.52 \pm 0.02. The radial velocities of the two stars were derived using a
model of two fast-rotating line profiles. From the residuals, we found a hint
of the stellar variations seen in the Kepler light curve with an amplitude of
about 1.41 km/s and a period close to the rotational period. This signal
appears to be about three order of magnitude larger than expected for stellar
activity. From the analysis of the residuals, we also put a 3-sigma upper-limit
on the mass of the transiting planet KOI-13.01 of 14.8 Mjup and 9.4 Mjup,
depending on which star hosts the transit. We found that this new companion has
no significant impact on the photometric determination of the mass of KOI-13.01
but is expected to affect precise infrared photometry. Finally, using dynamical
simulations, we infer that the new companion is orbiting around KOI-13B while
the transiting planet candidate is expected to orbit KOI-13A. Thus, the
transiting planet candidate KOI-13.01 is orbiting the main component of a
hierarchical triple system.Comment: Accepted in A&A Letters. 4 pages including 4 figures and the RV tabl
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