arXiv subjects

F. Bouchy

Publications and source records attributed to F. Bouchy.

At least 253 records · Page 14Linked to original sources

arXiv2011

The HARPS search for southern extrasolar planets. XXV. Four new planets in orbit around the moderatly active dwarfs HD 63765, HD 104067, HD 125595, and HIP 70849

We report the detection of four new extrasolar planets in orbit around the moderately active stars HD 63765, HD 104067, HIP 70849, and HD 125595 with the HARPS Echelle spectrograph mounted on the ESO 3.6-m telescope at La Silla. The first planet, HD 63765 b, has a minimum mass of 0.64MJup, a period of 358 days, and an eccentricity of 0.24. It orbits a G9 dwarf at 0.94 AU. The second planet, HD 104067 b, is a 3.6 Neptune-mass-planet with a 55.8-day-period. It orbits its parent K2 dwarf, in a circular orbit with a semi-major axis of a=0.26 AU. Radial velocity measurements present a \approx 500-day-oscillation that reveals significant magnetic cycles. The third planet is a 0.77 Neptune-mass-planet in circular orbit around the K4 dwarf, HD 12595, with a 9.67-day-period. Finally, HIP 7849 b is a long-period (5< P <75 years) and massive planet of m. sin i \approx 3.5-15 MJup that orbits a late K7 dwarf.

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arXiv2011

Transiting exoplanets from the CoRoT space mission XVII. The hot Jupiter CoRoT-17b: a very old planet

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.

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arXiv2011

WASP-40b: independent discovery of the 0.6-Mjup transiting exoplanet HAT-P-27b

From WASP photometry and SOPHIE radial velocities we report the discovery of WASP-40b (HAT-P-27b), a 0.6 Mjup planet that transits its 12th magnitude host star every 3.04 days. The host star is of late G-type or early K-type and likely has a metallicity greater than solar ([Fe/H] = 0.14 +/- 0.11). The planet's mass and radius are typical of the known hot Jupiters, thus adding another system to the apparent pileup of transiting planets with periods near 3 to 4 days. Our parameters match those of the recent HATnet announcement of the same planet, thus giving confidence in the techniques used. We report a possible indication of stellar activity in the host star.

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arXiv2011

WASP-39b: a highly inflated Saturn-mass planet orbiting a late G-type star

We present the discovery of WASP-39b, a highly inflated transiting Saturn-mass planet orbiting a late G-type dwarf star with a period of $4.055259 \pm 0.000008$\,d, Transit Epoch T$_{0}=2455342.9688\pm0.0002$\,(HJD), of duration $0.1168 \pm 0.0008$\,d. A combined analysis of the WASP photometry, high-precision follow-up transit photometry, and radial velocities yield a planetary mass of $\mpl=0.28\pm0.03\,\mj$ and a radius of $\rpl=1.27\pm0.04\,\rj$, resulting in a mean density of $0.14 \pm 0.02\,\rhoj$. The stellar parameters are mass $\mstar = 0.93 \pm 0.03\,\msun$, radius $\rstar = 0.895\pm 0.23\,\rsun$, and age $9^{+3}_{-4}$\,Gyr. Only WASP-17b and WASP-31b have lower densities than WASP-39b, although they are slightly more massive and highly irradiated planets. From our spectral analysis, the metallicity of WASP-39 is measured to be \feh\,$= -0.12\pm0.1$\,dex, and we find the planet to have an equilibrium temperature of $1116^{+33}_{-32}$\,K\,. Both values strengthen the observed empirical correlation between these parameters and the planetary radius for the known transiting Saturn-mass planets.

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arXiv2011

WASP-35b, WASP-48b and WASP-51b: Two new planets and an independent discovery of HAT-P-30b

We report the detection of WASP-35b, a planet transiting a metal-poor ([Fe/H] = -0.15) star in the Southern hemisphere, WASP-48b, an inflated planet which may have spun-up its slightly evolved host star of 1.75 R_sun in the Northern hemisphere, and the independent discovery of HAT-P-30b / WASP-51b, a new planet in the Northern hemisphere. Using WASP, RISE, FTS and TRAPPIST photometry, with CORALIE, SOPHIE and NOT spectroscopy, we determine that WASP-35b has a mass of 0.72 +/- 0.06 M_J and radius of 1.32 +/- 0.03 R_J, and orbits with a period of 3.16 days, WASP-48b has a mass of 0.98 +/- 0.09 M_J, radius of 1.67 +/- 0.08 R_J and orbits in 2.14 days, while WASP-51b, with an orbital period of 2.81 days, is found to have a mass of 0.76 +/- 0.05 M_J and radius of 1.42 +/- 0.04 R_J, agreeing with values of 0.71 +/- 0.03 M_J and 1.34 +/- 0.07 R_J reported for HAT-P-30b.

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arXiv2011

The retrograde orbit of the HAT-P-6b exoplanet

We observed with the SOPHIE spectrograph (OHP, France) the transit of the HAT-P-6b exoplanet across its host star. The resulting stellar radial velocities display the Rossiter-McLaughlin anomaly and reveal a retrograde orbit: the planetary orbital spin and the stellar rotational spin point towards approximately opposite directions. A fit to the anomaly measures a sky-projected angle lambda = 166 +/- 10 degrees between these two spin axes. All seven known retrograde planets are hot jupiters with masses M_p < 3 M_Jup. About two thirds of the planets in this mass range however are prograde and aligned (lambda ~ 0). By contrast, most of the more massive planets (M_p > 4 M_Jup) are prograde but misaligned. Different mechanisms may therefore be responsible for planetary obliquities above and below ~3.5 M_Jup.

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arXiv2011

Disentangling stellar activity and planetary signals

Photospheric stellar activity might be an important source of noise and confusion in the radial-velocity measurements. RV planet search surveys as well as follow-up of photometric transit surveys require a deeper understanding and characterization of the effects of stellar activities to disentangle it from planetary signals. We simulate dark spots on a rotating stellar photosphere. The variations of the photometry, RV and spectral line shapes are characterized and analyzed according to the stellar inclination, the latitude and the number of spots. The Lomb-Scargle periodograms of the RV variations induced by activity present power at the rotational period Prot of the star and its two-first harmonics Prot/2 and Prot/3. Three adjusted sinusoids fixed at Prot and its two-first harmonics allow to remove about 90% of the RV jitter amplitude. We apply and validate our approach on four known active planet-host stars: HD189733, GJ674, CoRoT-7 and iHor. We succeed in fitting simultaneously activity and planetary signals on GJ674 and CoRoT-7. This simultaneous modeling of the activity and planetary parameters leads to slightly larger masses of CoRoT-7b and c: respectively, 5.7+/-2.5ME and 13.1+/-4.1ME. The larger uncertainties take into account properly for the stellar active jitter. We excluded short-period low-mass exoplanets around iHor. For data with realistic time-sampling and white Gaussian noise, we use simulations to show that our approach is efficient to disentangle reflex-motion due to a planetary companion and stellar-activity induced-RV variations provided that 1) the planetary orbital period is not close to that of the stellar rotation or one of its two-first harmonics 2) the semi-amplitude of the planet exceeds 30% of the semi-amplitude of the active signal 3) the rotational period of the star is accurately known 4) the data cover more than one stellar rotational period.

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arXiv2011

Transiting exoplanets from the CoRoT space mission: XIII. CoRoT-14b: an unusually dense very hot Jupiter

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.

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arXiv2011

Radial velocity follow-up of CoRoT transiting exoplanets

We report on the results from the radial-velocity follow-up program performed to establish the planetary nature and to characterize the transiting candidates discovered by the space mission CoRoT. We use the SOPHIE at OHP, HARPS at ESO and the HIRES at Keck spectrographs to collect spectra and high- precision radial velocity (RV) measurements for several dozens dif- ferent candidates from CoRoT. We have measured the Rossiter- McLaughlin effect of several confirmed planets, especially CoRoT- 1b which revealed that it is another highly inclined system. Such high-precision RV data are necessary for the discovery of new tran- siting planets. Furthermore, several low mass planet candidates have emerged from our Keck and HARPS data.

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arXiv2010

SOPHIE velocimetry of Kepler transit candidates II. KOI-428b: a hot Jupiter transiting a subgiant F-star

We report the discovery of a hot Jupiter transiting a subgiant star with an orbital period of 6.87 days thanks to public photometric data from the Kepler space mission and new radial velocity observations obtained by the SOPHIE spectrograph. The planet KOI-428b with a radius of 1.17 +/- 0.04 RJup and a mass of 2.2 +/- 0.4MJup, orbits around a F5IV star with R* = 2.13 +/- 0.06Rsun, M* = 1.48 +/- 0.06 Msun and Teff = 6510 +/- 100 K. The star KOI-428 is the largest and the most evolved star discovered so far with a transiting planet.

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arXiv2010

The HARPS search for southern extra-solar planets: XXVI: Seven new planetary systems

We are conducting a planet search survey with HARPS since seven years. The volume-limited stellar sample includes all F2 to M0 main-sequence stars within 57.5 pc, where extrasolar planetary signatures are systematically searched for with the radial-velocity technics. In this paper, we report the discovery of new substellar companions of seven main-sequence stars and one giant star, detected through multiple Doppler measurements with the instrument HARPS installed on the ESO 3.6m telescope, La Silla, Chile. These extrasolar planets orbit the stars HD 1690, HD 25171, HD 33473A, HD 89839, HD 113538, HD 167677 and HD 217686. The already-published giant planet around HD 72659 is also analysed here, and its elements are better determined by the addition of HARPS and Keck data. The other discoveries are giant planets in distant orbits, ranging from 0.3 to 29 MJup, in mass and between 0.7 and 10 years in orbital period. The low metallicity of most of these new planet-hosting stars reinforces the current trend for long-distance planets around metal-poor stars. Long-term radial-velocity surveys allow probing the outskirts of extrasolar planetary systems, although confidence in the solution may be low until more than one orbital period is fully covered by the observations. For many systems discussed in this paper, longer baselines are necessary to refine the radial-velocity fit and derive planetary parameters. The radial-velocity time series of stars BD -114672 and HIP 21934 are also analysed and their behaviour interpreted in terms of the activity cycle of the star, rather than long-period planetary companions.

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arXiv2010

The spin-orbit angles of the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b from Rossiter-McLaughlin observations

We present observations of the Rossiter-McLaughlin effect for the transiting exoplanet systems WASP-1, WASP-24, WASP-38 and HAT-P-8, and deduce the orientations of the planetary orbits with respect to the host stars' rotation axes. The planets WASP-24b, WASP-38b and HAT-P-8b appear to move in prograde orbits and be well aligned, having sky-projected spin orbit angles consistent with zero: λ = -4.7 \pm 4.0°, λ = 15 + 33°/-43° and λ = -9.7 +9.0°/-7.7°, respectively. The host stars have Teff < 6250 K and conform with the trend of cooler stars having low obliquities. WASP-38b is a massive planet on a moderately long period, eccentric orbit so may be expected to have a misaligned orbit given the high obliquities measured in similar systems. However, we find no evidence for a large spin-orbit angle. By contrast, WASP-1b joins the growing number of misaligned systems and has an almost polar orbit, λ = -79 +4.5°/-4.3°. It is neither very massive, eccentric nor orbiting a hot host star, and therefore does not share the properties of many other misaligned systems.

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arXiv2010

Stellar characterization of CoRoT/Exoplanet fields with MATISSE

The homogeneous spectroscopic determination of the stellar parameters is a mandatory step for transit detections from space. Knowledge of which population the planet hosting stars belong to places constraints on the formation and evolution of exoplanetary systems. We used the FLAMES/GIRAFFE multi-fiber instrument at ESO to spectroscopically observe samples of stars in three CoRoT/Exoplanet fields, namely the LRa01, LRc01, and SRc01 fields, and characterize their stellar populations. We present accurate atmospheric parameters, Teff, logg, [M/H], and [$α$/Fe]\ derived for 1227 stars in these fields using the \matisse algorithm. The latter is based on the spectral synthesis methodology and automatically provides stellar parameters for large samples of observed spectra. We trained and applied this algorithm to \flames observations covering the Mg \textsc{i} b spectral range. It was calibrated on reference stars and tested on spectroscopic samples from other studies in the literature. The barycentric radial velocities and an estimate of the Vsini values were measured using cross-correlation techniques. We corrected our samples in the LRc01 and LRa01 CoRoT fields for selection effects to characterize their FGK dwarf stars population, and compiled the first unbiased reference sample for the in-depth study of planet metallicity relationship in these CoRoT fields. We conclude that the FGK dwarf population in these fields mainly exhibit solar metallicity. We show that for transiting planet finding missions, the probability of finding planets as a function of metallicity could explain the number of planets found in the LRa01 and LRc01 CoRoT fields. This study demonstrates the potential of multi-fiber observations combined with an automated classifier such as MATISSE for massive spectral classification.

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arXiv2010

The HARPS search for southern extra-solar planets. XXVII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems

Context. Low-mass extrasolar planets are presently being discovered at an increased pace by radial velocity and transit surveys, opening a new window on planetary systems. Aims. We are conducting a high-precision radial velocity survey with the HARPS spectrograph which aims at characterizing the population of ice giants and super-Earths around nearby solar-type stars. This will lead to a better understanding of their formation and evolution, and yield a global picture of planetary systems from gas giants down to telluric planets. Methods. Progress has been possible in this field thanks in particular to the sub-m/s radial velocity precision achieved by HARPS. We present here new high-quality measurements from this instrument. Results. We report the discovery of a planetary system comprising at least five Neptune-like planets with minimum masses ranging from 12 to 25 M_Earth, orbiting the solar-type star HD 10180 at separations between 0.06 and 1.4 AU. A sixth radial velocity signal is present at a longer period, probably due to a 65-M_Earth object. Moreover, another body with a minimum mass as low as 1.4 M_Earth may be present at 0.02 AU from the star. This is the most populated exoplanetary system known to date. The planets are in a dense but still well-separated configuration, with significant secular interactions. Some of the orbital period ratios are fairly close to integer or half-integer values, but the system does not exhibit any mean-motion resonances. General relativity effects and tidal dissipation play an important role to stabilize the innermost planet and the system as a whole. Numerical integrations show long-term dynamical stability provided true masses are within a factor ~3 from minimum masses. We further note that several low-mass planetary systems exhibit a rather "packed" orbital architecture with little or no space left for additional planets. (Abridged)

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arXiv2010

The HARPS search for southern extrasolar planets XXV. Results from the metal-poor sample

Searching for extrasolar planets around stars of different metallicity may provide strong constraints to the models of planet formation and evolution. In this paper we present the overall results of a HARPS (a high-precision spectrograph mostly dedicated to deriving precise radial velocities) program to search for planets orbiting a sample of 104 metal-poor stars (selected [Fe/H] below -0.5). Radial velocity time series of each star are presented and searched for signals using several statistical diagnostics. Stars with detected signals are presented, including 3 attributed to the presence of previously announced giant planets orbiting the stars HD171028, HD181720, and HD190984. Several binary stars and at least one case of a coherent signal caused by activity-related phenomena are presented. One very promising new, possible giant planet orbiting the star HD107094 is discussed, and the results are analyzed in light of the metallicity-giant planet correlation. We conclude that the frequency of giant planets orbiting metal-poor stars may be higher than previously thought, probably reflecting the higher precision of the HARPS survey. In the metallicity domain of our sample, we also find evidence that the frequency of planets is a steeply rising function of the stellar metal content, as found for higher metallicity stars.

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arXiv2010

WASP-38b: A Transiting Exoplanet in an Eccentric, 6.87d Period Orbit

We report the discovery of WASP-38b, a long period transiting planet in an eccentric 6.871815 day orbit. The transit epoch is 2455335.92050 +/- 0.00074 (HJD) and the transit duration is 4.663 hours. WASP-38b's discovery was enabled due to an upgrade to the SuperWASP-North cameras. We performed a spectral analysis of the host star HD 146389/BD+10 2980 that yielded Teff = 6150 +/- 80K, logg =4.3 +/- 0.1, vsini=8.6 +/- 0.4 km/s, M*=1.16 +/- 0.04 Msun and R* =1.33 +/- 0.03 Rsun, consistent with a dwarf of spectral type F8. Assuming a main-sequence mass-radius relation for the star, we fitted simultaneously the radial velocity variations and the transit light curves to estimate the orbital and planetary parameters. The planet has a mass of 2.69 +/- 0.06 Mjup and a radius of 1.09 +/-0.03 Rjup giving a density, rho_p = 2.1 +/-0.1 rho_jup. The high precision of the eccentricity e=0.0314 +/- 0.0044 is due to the relative transit timing from the light curves and the RV shape. The planet equilibrium temperature is estimated at 1292 +/- 33K. WASP-38b is the longest period planet found by SuperWASP-North and with a bright host star (V =9.4 mag), is a good candidate for followup atmospheric studies.

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arXiv2010

The HARPS search for southern extra-solar planets. XXIV. Companions to HD 85390, HD 90156 and HD 103197: A Neptune analogue and two intermediate mass planets

We report the detection of three new extrasolar planets orbiting the solar type stars HD 85390, HD 90156 and HD 103197 with the HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla observatory. HD 85390 has a planetary companion with a projected intermediate mass (42.0 Earth masses) on a 788-day orbit (a=1.52 AU) with an eccentricity of 0.41, for which there is no analogue in the solar system. A drift in the data indicates the presence of another companion on a long period orbit, which is however not covered by our measurements. HD 90156 is orbited by a warm Neptune analogue with a minimum mass of 17.98 Earth masses (1.05 Neptune masses), a period of 49.8 days (a=0.25 AU) and an eccentricity of 0.31. HD 103197 has an intermediate mass planet on a circular orbit (P=47.8 d, Msini=31.2 Earth masses). We discuss the formation of planets of intermediate mass (about 30-100 Earth masses) which should be rare inside a few AU according to core accretion formation models.

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arXiv2010

Transiting exoplanets from the CoRoT space mission. XV. CoRoT-15b: a brown dwarf transiting companion

We report the discovery by the CoRoT space mission of a transiting brown dwarf orbiting a F7V star with an orbital period of 3.06 days. CoRoT-15b has a radius of 1.12 +0.30 -0.15 Rjup, a mass of 63.3 +- 4.1 Mjup, and is thus the second transiting companion lying in the theoretical mass domain of brown dwarfs. CoRoT-15b is either very young or inflated compared to standard evolution models, a situation similar to that of M-dwarfs stars orbiting close to solar-type stars. Spectroscopic constraints and an analysis of the lightcurve favors a spin period between 2.9 and 3.1 days for the central star, compatible with a double-synchronisation of the system.

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