ABSTRACT: We report the discovery of KOI-127b, a Saturn-mass transiting planet in a
3.6-day orbit around a metal-rich solar-like star. We combined the publicly
available Kepler photometry (quarters 1-13) with high-resolution spectroscopy
from the Sandiford@McDonald and FIES@NOT spectrographs. We derived the system
parameters via a simultaneous joint fit to the photometric and radial velocity
measurements. Our analysis is based on the Bayesian approach and is carried out
by sampling the parameter posterior distributions using Markov chain Monte
Carlo simulation. KOI-127b is a moderately inflated planet with a mass of
Mp=0.430+/-0.032 Mjup, radius of Rp=0.960+/-0.016 Rjup, and bulk density of
0.603+/-0.055 g/cm^3. It orbits a slowly rotating (P=36+/-6 days) G5V star with
M*=0.95+/-0.04 Msun, R*=0.99+/-0.02 Rsun, Teff=5520+/-60 K, [M/H]=0.20+/-0.05,
and an age of 7.5+/-2.0 Gyr. The lack of detectable planetary occultation with
a depth larger than about 10 ppm, implies a planet's geometric and Bond albedo
of Ag<0.087+/-0.008 and Ab<0.058+/-0.006, respectively, placing KOI-127b among
the gas-giant planets with the lowest albedo known so far. We found neither
additional planetary transit signals, nor transit timing variations (TTVs) at a
level of about 0.5 minutes, in accordance with the trend that close-in gas
giant planets seem to belong to single-planet systems. The 106 transits
observed in short-cadence mode by Kepler for nearly 1.2 years show no
detectable signatures of the planet's passage in front of starspots. We
explored the implications of the absence of detectable spot-crossing events for
the inclination of the stellar spin-axis, the sky-projected spin-orbit
obliquity, and the latitude of magnetically active regions.
ABSTRACT: We study how the precision of the exoplanet radius determination is affected
by our present knowledge of limb darkening in two cases: when we fix the limb
darkening coefficients and when we adjust them. We also investigate the effects
of spots in one-colour photometry. We study the effect of limb darkening on the
planetary radius determination both via analytical expressions and by numerical
experiments. We also compare some of the existing limb darkening tables. When
stellar spots affect the fit, we replace the limb darkening coefficients,
calculated for the unspotted cases, with effective limb darkening coefficients
to describe the effect of the spots. There are two important cases. (1) When
one fixes the limb darkening values according to some theoretical predictions,
the inconsistencies of the tables do not allow us to reach accuracy in the
planetary radius of better than 1-10% (depending on the impact parameter) if
the host star's surface effective temperature is higher than 5000 K. Below 5000
K the radius ratio determination may contain even 20% error. (2) When one
allows adjustment of the limb darkening coefficients, the a/Rs ratio, the
planet-to-stellar radius ratio, and the impact parameter can be determined with
sufficient accuracy (<1%), if the signal-to-noise ratio is high enough.
However, the presence of stellar spots and faculae can destroy the agreement
between the limb darkening tables and the fitted limb darkening coefficients,
but this does not affect the precision of the planet radius determination. We
also find that it is necessary to fit the contamination factor, too. We
conclude that the present inconsistencies of theoretical stellar limb darkening
tables suggests one should not fix the limb darkening coefficients. When one
allows them to be adjusted, then the planet radius, impact parameter, and the
a/Rs can be obtained with the required precision.
ABSTRACT: Context. Transit detection algorithms are mathematical tools used for
detecting planets in the photometric data of transit surveys. In this work we
study their application to space-based surveys. Aims: Space missions are
exploring the parameter space of the transit surveys where classical algorithms
do not perform optimally, either because of the challenging signal-to-noise
ratio of the signal or its non-periodic characteristics. We have developed an
algorithm addressing these challenges for the mission CoRoT. Here we extend the
application to the data from the space mission Kepler. We aim at understanding
the performances of algorithms in different data sets. Methods: We built a
simple analytical model of the transit signal and developed a strategy for the
search that improves the detection performance for transiting planets. We
analyzed Kepler data with a set of stellar activity filtering and transit
detection tools from the CoRoT community that are designed for the search of
transiting planets. Results: We present a new algorithm and its performances
compared to one of the most widely used techniques in the literature using
CoRoT data. Additionally, we analyzed Kepler data corresponding to quarter Q1
and compare our results with the most recent list of planetary candidates from
the Kepler survey. We found candidates that went unnoticed by the Kepler team
when analyzing longer data sets. We study the impact of instrumental features
on the production of false alarms and false positives. These results show that
the analysis of space mission data advocates the use of complementary
detrending and transit detection tools also for future space-based transit
surveys such as PLATO.
ABSTRACT: The CoRoT field LRa02 has been observed with the Berlin Exoplanet Search
Telescope II (BEST II) during the southern summer 2007/2008. A first analysis
of stellar variability led to the publication of 345 newly discovered variable
stars. Now, a deeper analysis of this data set was used to optimize the
variability search procedure. Several methods and parameters have been tested
in order to improve the selection process compared to the widely used J index
for variability ranking. This paper describes an empirical approach to treat
systematic trends in photometric data based upon the analysis of variance
statistics that can significantly decrease the rate of false detections.
Finally, the process of reanalysis and method improvement has virtually
doubled the number of variable stars compared to the first analysis by Kabath
et al. A supplementary catalog of 272 previously unknown periodic variables
plus 52 stars with suspected variability is presented. Improved ephemerides are
given for 19 known variables in the field. In addition, the BEST II results are
compared with CoRoT data and its automatic variability classification.
Solar System Research 05/2012; 45(4):374-375. · 0.68 Impact Factor
ABSTRACT: We report the discovery by the CoRoT space mission of a new giant
planet, CoRoT-20b. The planet has a mass of 4.24 ± 0.23
MJup and a radius of 0.84 ± 0.04 RJup. With
a mean density of 8.87 ± 1.10 g cm-3, it is among the
most compact planets known so far. Evolutionary models for the planet
suggest a mass of heavy elements of the order of 800 M⊕
if embedded in a central core, requiring a revision either of the planet
formation models or both planet evolution and structure models. We note
however that smaller amounts of heavy elements are expected by more
realistic models in which they are mixed throughout the envelope. The
planet orbits a G-type star with an orbital period of 9.24 days and an
eccentricity of 0.56.The star's projected rotational velocity is vsini =
4.5 ± 1.0 km s-1, corresponding to a spin period of
11.5 ± 3.1 days if its axis of rotation is perpendicular to the
orbital plane. In the framework of Darwinian theories and neglecting
stellar magnetic breaking, we calculate the tidal evolution of the
system and show that CoRoT-20b is presently one of the very few
Darwin-stable planets that is evolving toward a triple synchronous state
with equality of the orbital, planetary and stellar spin periods.
The CoRoT space mission, launched on December 27th 2006, has been
developed and is operated by CNES, with the contribution of Austria,
Belgium, Brazil, ESA (RSSD and Science Programme), Germany, and Spain.
Astronomy and Astrophysics 01/2012; 538:145. · 4.59 Impact Factor
ABSTRACT: Observations of transiting extrasolar planets are of key importance to our
understanding of planets because their mass, radius, and mass density can be
determined. The CoRoT space mission allows us to achieve a very high
photometric accuracy. By combining CoRoT data with high-precision radial
velocity measurements, we derive precise planetary radii and masses. We report
the discovery of CoRoT-19b, a gas-giant planet transiting an old, inactive
F9V-type star with a period of four days. After excluding alternative physical
configurations mimicking a planetary transit signal, we determine the radius
and mass of the planet by combining CoRoT photometry with high-resolution
spectroscopy obtained with the echelle spectrographs SOPHIE, HARPS, FIES, and
SANDIFORD. To improve the precision of its ephemeris and the epoch, we observed
additional transits with the TRAPPIST and Euler telescopes. Using HARPS spectra
obtained during the transit, we then determine the projected angle between the
spin of the star and the orbit of the planet. We find that the host star of
CoRoT-19b is an inactive F9V-type star close to the end of its main-sequence
life. The host star has a mass M*=1.21+/-0.05 Msun and radius R*=1.65+/-0.04
Rsun. The planet has a mass of Mp=1.11+/-0.06 Mjup and radius of Rp=1.29+/-0.03
Rjup. The resulting bulk density is only rho=0.71+/-0.06 gcm-3, which is much
lower than that for Jupiter. The exoplanet CoRoT-19b is an example of a giant
planet of almost the same mass as Jupiter but a 30% larger radius.
åp. 12/2011; 537.
ABSTRACT: Context: CoRoT is a pioneering space mission whose primary goals are stellar
seismology and extrasolar planets search. Its surveys of large stellar fields
generate numerous planetary candidates whose lightcurves have transit-like
features. An extensive analytical and observational follow-up effort is
undertaken to classify these candidates. Aims: The list of planetary transit
candidates from the CoRoT LRa01 star field in the Monoceros constellation
towards the Galactic anti-center is presented. The CoRoT observations of LRa01
lasted from 24 October 2007 to 3 March 2008. Methods: 7470 chromatic and 3938
monochromatic lightcurves were acquired and analysed. Instrumental noise and
stellar variability were treated with several filtering tools by different
teams from the CoRoT community. Different transit search algorithms were
applied to the lightcurves. Results: Fifty-one stars were classified as
planetary transit candidates in LRa01. Thirty-seven (i.e., 73 % of all
candidates) are "good" planetary candidates based on photometric analysis only.
Thirty-two (i.e., 87 % of the "good" candidates) have been followed-up. At the
time of this writing twenty-two cases have been solved and five planets have
been discovered: three transiting hot-Jupiters (CoRoT-5b, CoRoT-12b, and
CoRoT-21b), the first terrestrial transiting planet (CoRoT-7b), and another
planet in the same system (CoRoT-7c, detected by radial velocity survey only).
Evidences of another non-transiting planet in the CoRoT-7 system, namely
CoRoT-7d, have been recently found.
Astronomy and Astrophysics. 10/2011; 538(2012).
ABSTRACT: We report the discovery by the CoRoT space mission of a new giant planet,
CoRoT-20b. The planet has a mass of 4.24 +/- 0.23 MJ and a radius of 0.84 +/-
0.04 RJ. With a mean density of 8.87 +/- 1.10 g/cm^3, it is among the most
compact planets known so far. Evolution models for the planet suggest a mass of
heavy elements of the order of 800 ME if embedded in a central core, requiring
a revision either of the planet formation models or of planet evolution and
structure models. We note however that smaller amounts of heavy elements are
expected from more realistic models in which they are mixed throughout the
envelope. The planet orbits a G-type star with an orbital period of 9.24 days
and an eccentricity of 0.56. The star's projected rotational velocity is vsini
= 4.5 +/- 1.0 km/s, corresponding to a spin period of 11.5 +/- 3.1 days if its
axis of rotation is perpendicular to the orbital plane. In the framework of
Darwinian theories and neglecting stellar magnetic breaking, we calculate the
tidal evolution of the system and show that CoRoT-20b is presently one of the
very few Darwin-stable planets that is evolving towards a triple synchronous
state with equality of the orbital, planetary and stellar spin periods.
ABSTRACT: The Berlin Exoplanet Search Telescope is a small-aperture, wide-field telescope dedicated to time-series photometric observations. During an initial commissioning phase at the Thüringer Landessternwarte Tautenburg, Germany, and subsequent operations at the Observatoire de Haute-Provence, France, a 10 deg2 circumpolar field close to the galactic plane centered at (α, δ) = (02h39m23s, + 52°01'46'') (J2000.0) was observed between 2001 August and 2006 December during 52 nights. From the 32129 stars observed, a subsample of 145 stars with clear stellar variability was detected out of which 125 are newly identified variable objects. For five bright objects, the system parameters were derived by modeling the light curve.
The Astronomical Journal 09/2011; 142(4):114. · 4.03 Impact Factor
ABSTRACT: We report the detection of CoRoT-18b, a massive hot jupiter transiting in
front of its host star with a period of 1.9000693 +/- 0.0000028 days. This
planet was discovered thanks to photometric data secured with the CoRoT
satellite combined with spectroscopic and photometric ground-based follow-up
observations. The planet has a mass M_p = 3.47 +/- 0.38 M_Jup, a radius R_p =
1.31 +/- 0.18 R_Jup, and a density rho_p = 2.2 +/- 0.8 g/cm3. It orbits a G9V
star with a mass M_* = 0.95 +/- 0.15 M_Sun, a radius R_* = 1.00 +/- 0.13 R_Sun,
and a rotation period P_rot = 5.4 +/- 0.4 days. The age of the system remains
uncertain, with stellar evolution models pointing either to a few tens Ma or
several Ga, while gyrochronology and lithium abundance point towards ages of a
few hundred Ma. This mismatch potentially points to a problem in our
understanding of the evolution of young stars, with possibly significant
implications for stellar physics and the interpretation of inferred sizes of
exoplanets around young stars. We detected the Rossiter-McLaughlin anomaly in
the CoRoT-18 system thanks to the spectroscopic observation of a transit. We
measured the obliquity psi = 20 +/- 20 degrees (sky-projected value: lambda =
-10 +/- 20 degrees), indicating that the planet orbits in the same way as the
star is rotating and that this prograde orbit is nearly aligned with the
åp. 07/2011; 533.
ABSTRACT: We report on the discovery of a hot Jupiter-type exoplanet, CoRoT-17b,
detected by the CoRoT satellite. It has a mass of $2.43\pm0.30$\Mjup and a
radius of $1.02\pm0.07$\Rjup, while its mean density is $2.82\pm0.38$ g/cm$^3$.
CoRoT-17b is in a circular orbit with a period of $3.7681\pm0.0003$ days. The
host star is an old ($10.7\pm1.0$ Gyr) main-sequence star, which makes it an
intriguing object for planetary evolution studies. The planet's internal
composition is not well constrained and can range from pure H/He to one that
can contain $\sim$380 earth masses of heavier elements.
åp. 06/2011; 531.
ABSTRACT: In this paper, the CoRoT Exoplanet Science Team announces its 14th discovery.
Herein, we discuss the observations and analyses that allowed us to derive the
parameters of this system: a hot Jupiter with a mass of $7.6 \pm 0.6$ Jupiter
masses orbiting a solar-type star (F9V) with a period of only 1.5 d, less than
5 stellar radii from its parent star. It is unusual for such a massive planet
to have such a small orbit: only one other known exoplanet with a higher mass
orbits with a shorter period.
ABSTRACT: The CoRoT exoplanet science team announces the discovery of CoRoT-11b, a fairly massive hot-Jupiter transiting a V=12.9 mag F6 dwarf star (M*=1.27 +/- 0.05 Msun, R*=1.37 +/- 0.03 Rsun, Teff=6440 +/- 120 K), with an orbital period of P=2.994329 +/- 0.000011 days and semi-major axis a=0.0436 +/- 0.005 AU. The detection of part of the radial velocity anomaly caused by the Rossiter-McLaughlin effect shows that the transit-like events detected by CoRoT are caused by a planet-sized transiting object in a prograde orbit. The relatively high projected rotational velocity of the star (vsini=40+/-5 km/s) places CoRoT-11 among the most rapidly rotating planet host stars discovered so far. With a planetary mass of mp=2.33+/-0.34 Mjup and radius rp=1.43+/-0.03 Rjup, the resulting mean density of CoRoT-11b (rho=0.99+/-0.15 g/cm^3) can be explained with a model for an inflated hydrogen-planet with a solar composition and a high level of energy dissipation in its interior. Comment: 15 pages, 13 figures, accepted for publication in A&A
Astronomy and Astrophysics 09/2010; · 4.59 Impact Factor
ABSTRACT: The space telescope CoRoT searches for transiting extrasolar planets by continuously monitoring the optical flux of thousands of stars in several fields of view. We report the discovery of CoRoT-10b, a giant planet on a highly eccentric orbit (e=0.53 +/- 0.04) revolving in 13.24 days around a faint (V=15.22) metal-rich K1V star. We use CoRoT photometry, radial velocity observations taken with the HARPS spectrograph, and UVES spectra of the parent star to derive the orbital, stellar and planetary parameters. We derive a radius of the planet of 0.97 +/- 0.07 R_Jup and a mass of 2.75 +/- 0.16 M_Jup. The bulk density, rho_pl=3.70 +/- 0.83 g/cm^3, is ~2.8 that of Jupiter. The core of CoRoT-10b could contain up to 240 M_Earth of heavy elements. Moving along its eccentric orbit, the planet experiences a 10.6-fold variation in insolation. Owing to the long circularisation time, tau_circ > 7 Gyr, a resonant perturber is not required to excite and maintain the high eccentricity of CoRoT-10b. Comment: 9 pages, 9 figures, accepted for publication by Astronomy and Astrophysics
ABSTRACT: Of the over 400 known exoplanets, there are about 70 planets that transit their central star, a situation that permits the derivation of their basic parameters and facilitates investigations of their atmospheres. Some short-period planets, including the first terrestrial exoplanet (CoRoT-7b), have been discovered using a space mission designed to find smaller and more distant planets than can be seen from the ground. Here we report transit observations of CoRoT-9b, which orbits with a period of 95.274 days on a low eccentricity of 0.11 +/- 0.04 around a solar-like star. Its periastron distance of 0.36 astronomical units is by far the largest of all transiting planets, yielding a 'temperate' photospheric temperature estimated to be between 250 and 430 K. Unlike previously known transiting planets, the present size of CoRoT-9b should not have been affected by tidal heat dissipation processes. Indeed, the planet is found to be well described by standard evolution models with an inferred interior composition consistent with that of Jupiter and Saturn.
Nature 03/2010; 464(7287):384-7. · 36.28 Impact Factor
ABSTRACT: The CoRoT satellite exoplanetary team announces its sixth transiting planet in this paper. We describe and discuss the satellite observations as well as the complementary ground-based observations - photometric and spectroscopic - carried out to assess the planetary nature of the object and determine its specific physical parameters. The discovery reported here is a `hot Jupiter' planet in an 8.9d orbit, 18 stellar radii, or 0.08 AU, away from its primary star, which is a solar-type star (F9V) with an estimated age of 3.0 Gyr. The planet mass is close to 3 times that of Jupiter. The star has a metallicity of 0.2 dex lower than the Sun, and a relatively high $^7$Li abundance. While thelightcurveindicatesamuchhigherlevelof activity than, e.g., the Sun, there is no sign of activity spectroscopically in e.g., the [Ca ] H&K lines.
Astronomy and Astrophysics 01/2010; · 4.59 Impact Factor
ABSTRACT: The 11408 targets observed by CoRoT were selected using the information
gathered in the database Exo-Dat (Deleuil et al. 2009AJ....138..649D;
Meunier et al. 2007, ASP Conf., 376, 339), built with dedicated ground
based photometric observations in the visible and near IR bands from
(1 data file).
VizieR Online Data Catalog. 12/2009; 350:60501.
ABSTRACT: The Berlin Exoplanet Search Telescope (BEST) wide-angle telescope installed at the Observatoire de Haute-Provence and operated in remote control from Berlin by the Institut für Planetenforschung, DLR, has observed the CoRoT target fields prior to the mission. The resulting archive of stellar photometric light curves is used to search for deep transit events announced during CoRoT's alarm mode to aid in fast photometric confirmation of these events. The "initial run" field of CoRoT (IRa01) was observed with BEST in 2006 November and December for 12 nights. The first "long run" field (LRc01) was observed from 2005 June to September for 35 nights. After standard CCD data reduction, aperture photometry has been performed using the ISIS image subtraction method. About 30,000 light curves were obtained in each field. Transits of the first detected planets by the CoRoT mission, CoRoT-1b and CoRoT-2b, were found in archived data of the BEST survey and their light curves are presented here. Such detections provide useful information at the early stage of the organization of follow-up observations of satellite alarm-mode planet candidates. In addition, no period change was found over ~4 years between the first BEST observation and last available transit observations.
The Astronomical Journal 11/2009; 139(1):53. · 4.03 Impact Factor
ABSTRACT: Aims. The CoRoT space mission continues to photometrically monitor about 12 000 stars in its field-of-view for a series of target fields to search for transiting extrasolar planets ever since 2007. Deep transit signals can be detected quickly in the "alarm-mode" in parallel to the ongoing target field monitoring. CoRoT's first planets have been detected in this mode. Methods. The CoRoT raw lightcurves are filtered for orbital residuals, outliers, and low-frequency stellar signals. The phase folded lightcurve is used to fit the transit signal and derive the main planetary parameters. Radial velocity follow-up observations were initiated to secure the detection and to derive the planet mass. Results. We report the detection of CoRoT-5b, detected during observations of the LRa01 field, the first long-duration field in the galactic anticenter direction. CoRoT-5b is a "hot Jupiter-type" planet with a radius of 1.388(+0.046, -0.047) R_Jup, a mass of 0.467(+0.047, -0.024) M_Jup, and therefore, a mean density of 0.217(+0.031, -0.025) g cm-3. The planet orbits an F9V star of 14.0 mag in 4.0378962 +/- 0.0000019 days at an orbital distance of 0.04947(+0.00026, -0.00029) AU. Comment: 6 pages, 6 figures, 4 tables, accepted at A&A