arXiv subjects

D. Queloz

Publications and source records attributed to D. Queloz.

At least 271 records · Page 15Linked to original sources

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

Astrometric search for a planet around VB 10

We observed VB 10 in August and September 2009 using the FORS2 camera of the VLT with the aim of measuring its astrometric motion and of probing the presence of the announced planet VB 10b. We used the published STEPS astrometric positions of VB 10 over a time-span of 9 years, which allowed us to compare the expected motion of VB 10 due to parallax and proper motion with the observed motion and to compute precise deviations. The achieved single-epoch precisions of our observations are about 0.1 mas and the data showed no significant residual trend, while the presence of the planet should have induced an apparent proper motion larger than 10 mas/yr. Subtraction of the predicted orbital motion from the observed data produces a large trend in position residuals of VB 10. We estimated the probability that this trend is caused by random noise. Taking all the uncertainties into account and using Monte-Carlo resampling of the data, we are able to reject the existence of VB 10b with the announced mass of 6.4 M_J with the false alarm probability of only 0.0005. A 3.2 M_J planet is also rejected with a false alarm probability of 0.023.

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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 Doppler Shadow of WASP-3b: A tomographic analysis of Rossiter-McLaughlin observations

Hot-Jupiter planets must form at large separations from their host stars where the temperatures are cool enough for their cores to condense. They then migrate inwards to their current observed orbital separations. Different theories of how this migration occurs lead to varying distributions of orbital eccentricity and the alignment between the rotation axis of the star and the orbital axis of the planet. The spin-orbit alignment of a transiting system is revealed via the Rossiter-McLaughlin effect, which is the anomaly present in the radial velocity measurements of the rotating star during transit due to the planet blocking some of the starlight. In this paper we aim to measure the spin-orbit alignment of the WASP-3 system via a new way of analysing the Rossiter-McLaughlin observations. We apply a new tomographic method for analysing the time variable asymmetry of stellar line profiles caused by the Rossiter-McLaughlin effect. This new method eliminates the systematic error inherent in previous methods used to analyse the effect. We find a value for the projected stellar spin rate of v sin i = 13.9 \pm 0.03 km/s which is in agreement with previous measurements but has a much higher precision. The system is found to be well aligned which favours an evolutionary history for WASP-3b involving migration through tidal interactions with a protoplanetary disc. Using gyrochronology we estimate the age of the star to be ~300 Myr with an upper limit of 2 Gyr from comparison with isochrones.

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arXiv2010

WASP-22 b: A transiting "hot Jupiter" planet in a hierarchical triple system

We report the discovery of a transiting planet orbiting the star TYC 6446-326-1. The star, WASP-22, is a moderately bright (V=12.0) solar-type star (Teff = 6000 +/- 100 K, [Fe/H] = -0.05 +/- 0.08). The lightcurve of the star obtained with the WASP-South instrument shows periodic transit-like features with a depth of about 1 and a duration of 0.14 days. The presence of a transit-like feature in the lightcurve is confirmed using z-band photometry obtained with Faulkes Telescope South. High resolution spectroscopy obtained with the CORALIE and HARPS spectrographs confirm the presence of a planetary mass companion with an orbital period of 3.533 days in a near-circular orbit. From a combined analysis of the spectroscopic and photometric data assuming that the star is a typical main-sequence star we estimate that the planet has a mass M_p = 0.56 +/- 0.02 M_Jup and a radius R_p = 1.12 +/- 0.04 R_Jup. In addition, there is a linear trend of 40 m/s/yr in the radial velocities measured over 16 months, from which we infer the presence of a third body with a long period orbit in this system. The companion may be a low mass M-dwarf, a white dwarf or a second planet.

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arXiv2010

WASP-32b: A transiting hot Jupiter planet orbiting a lithium-poor, solar-type star

We report the discovery of a transiting planet orbiting the star TYC 2-1155-1. The star, WASP-32, is a moderately bright (V=11.3) solar-type star (Teff=6100 +- 100K, [Fe/H] = -0.13 +- 0.10). The lightcurve of the star obtained with the WASP-South and WASP-North instruments shows periodic transit-like features with a depth of about 1% and a duration of 0.10d every 2.72d. The presence of a transit-like feature in the lightcurve is confirmed using z-band photometry obtained with Faulkes Telescope North. High resolution spectroscopy obtained with the CORALIE spectrograph confirms the presence of a planetary mass companion. From a combined analysis of the spectroscopic and photometric data, assuming that the star is a typical main-sequence star, we estimate that the planet has a mass M_p = 3.60 +- 0.07 M_Jup and a radius R_p = 1.19 +- 0.06R_Jup. WASP-32 is one of a small group of hot Jupiters with masses M_p > 3M_Jup. We find that some stars with hot Jupiter companions and with masses M_* =~ 1.2M_sun, including WASP-32, are depleted in lithium, but that the majority of these stars have similar lithium abundances to field stars.

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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

WASP-37b: a 1.8 MJ exoplanet transiting a metal-poor star

We report on the discovery of WASP-37b, a transiting hot Jupiter orbiting a mv = 12.7 G2-type dwarf, with a period of 3.577471 \pm 0.00001 d, transit epoch T0 = 2455338.6188 \pm 0.0006 (HJD), and a transit duration 0.1304 \pm 0.0018 d. The planetary companion has a mass Mp = 1.80 \pm 0.17 MJ and radius Rp = 1.16 \pm 0.07 RJ, yielding a mean density of 1.15 \pm 0.15 times that of Jupiter. From a spectral analysis and comparisons with stellar models, we find the host star has M* = 0.925 \pm 0.120 Msun, R* = 1.003 \pm 0.053 Rsun, Teff = 5800 \pm 150 K and [Fe/H] = -0.40 \pm 0.12. WASP-37 is therefore one of the lowest metallicity stars to host a transiting planet.

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arXiv2010

WASP-25b: a 0.6 M_J planet in the Southern hemisphere

We report the detection of a 0.6 M_J extrasolar planet by WASP-South, WASP-25b, transiting its solar-type host star every 3.76 days. A simultaneous analysis of the WASP, FTS and Euler photometry and CORALIE spectroscopy yields a planet of R_p = 1.22 R_J and M_p = 0.58 M_J around a slightly metal-poor solar-type host star, [Fe/H] = -0.05 \pm 0.10, of R_{\ast} = 0.92 R_{\odot} and M_{\ast} = 1.00 M_{\odot}. WASP-25b is found to have a density of ρ_p = 0.32 ρ_J, a low value for a sub-Jupiter mass planet. We investigate the relationship of planetary radius to planetary equilibrium temperature and host star metallicity for transiting exoplanets with a similar mass to WASP-25b, finding that these two parameters explain the radii of most low-mass planets well.

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arXiv2010

WASP-29b: A Saturn-sized transiting exoplanet

We report the discovery of a Saturn-sized planet transiting a V = 11.3, K4 dwarf star every 3.9 d. WASP-29b has a mass of 0.24+/-0.02 M_Jup and a radius of 0.79+/-0.05 R_Jup, making it the smallest planet so far discovered by the WASP survey, and the exoplanet most similar in mass and radius to Saturn. The host star WASP-29 has an above-Solar metallicity and fits a possible correlation for Saturn-mass planets such that planets with higher-metallicity host stars have higher core masses and thus smaller radii.

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arXiv2010

Transiting exoplanets from the CoRoT space mission XIV. CoRoT-11b: a transiting massive "hot-Jupiter" in a prograde orbit around a rapidly rotating F-type star

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.

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arXiv2010

Transiting exoplanets from the CoRoT space mission. XI. CoRoT-8b: a hot and dense sub-Saturn around a K1 dwarf

We report the discovery of CoRoT-8b, a dense small Saturn-class exoplanet that orbits a K1 dwarf in 6.2 days, and we derive its orbital parameters, mass, and radius. We analyzed two complementary data sets: the photometric transit curve of CoRoT-8b as measured by CoRoT and the radial velocity curve of CoRoT-8 as measured by the HARPS spectrometer. We find that CoRoT-8b is on a circular orbit with a semi-major axis of 0.063 +/- 0.001 AU. It has a radius of 0.57 +/- 0.02 RJ, a mass of 0.22 +/- 0.03 MJ, and therefore a mean density 1.6 +/- 0.1 g/cm^3. With 67 % of the size of Saturn and 72 % of its mass, CoRoT-8b has a density comparable to that of Neptune (1.76 g/cm^3). We estimate its content in heavy elements to be 47-63 Earth masses, and the mass of its hydrogen-helium envelope to be 7-23 Earth masses. At 0.063 AU, the thermal loss of hydrogen of CoRoT-8b should be no more than about 0.1 % over an assumed integrated lifetime of 3~Ga.

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arXiv2010

Transiting exoplanets from the CoRoT space mission. XIII. CoRoT-13b: a dense hot Jupiter in transit around a star with solar metallicity and super-solar lithium content

We announce the discovery of the transiting planet CoRoT-13b. Ground based follow-up in CFHT and IAC80 confirmed CoRoT's observations. The mass of the planet was measured with the HARPS spectrograph and the properties of the host star were obtained analyzing HIRES spectra from the Keck telescope. It is a hot Jupiter-like planet with an orbital period of 4.04 days, 1.3 Jupiter masses, 0.9 Jupiter radii, and a density of 2.34 g cm-3. It orbits a G0V star with Teff=5945K, M*=1.09 Msun, R*=1.01 Rsun, solar metallicity, a lithium content of +1.45 dex, and an estimated age between 0.12 and 3.15 Gyr. The lithium abundance of the star is consistent with its effective temperature, activity level, and age range derived from the stellar analysis. The density of the planet is extreme for its mass. It implies the existence of an amount of heavy elements with a mass between about 140 and 300 Mearth.

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arXiv2010

Transiting exoplanets from the CoRoT space mission. XII. CoRoT-12b: a short-period low-density planet transiting a solar analog star

We report the discovery by the CoRoT satellite of a new transiting giant planet in a 2.83 days orbit about a V=15.5 solar analog star (M_* = 1.08 +- 0.08 M_sun, R_* = 1.1 +- 0.1 R_sun, T_eff = 5675 +- 80 K). This new planet, CoRoT-12b, has a mass of 0.92 +- 0.07 M_Jup and a radius of 1.44 +- 0.13 R_Jup. Its low density can be explained by standard models for irradiated planets.

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arXiv2010

The SOPHIE search for northern extrasolar planets III. A Jupiter-mass companion around HD 109246

We report the detection of a Jupiter-mass planet discovered with the SOPHIE spectrograph mounted on the 1.93-m telescope at the Haute-Provence Observatory. The new planet orbits HD109246, a G0V star slightly more metallic than the Sun. HD109246b has a minimum mass of 0.77 MJup, an orbital period of 68 days, and an eccentricity of 0.12. It is placed in a sparsely populated region of the period distribution of extrasolar planets. We also present a correction method for the so-called seeing effect that affects the SOPHIE radial velocities. We complement this discovery announcement with a description of some calibrations that are implemented in the SOPHIE automatic reduction pipeline. These calibrations allow the derivation of the photon-noise radial velocity uncertainty and some useful stellar properties (vsini, [Fe/H], logR'HK) directly from the SOPHIE data.

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arXiv2010

CoRoT-10b: a giant planet in a 13.24 day eccentric orbit

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.

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arXiv2010

WASP-21b: a hot-Saturn exoplanet transiting a thick disc star

We report the discovery of WASP-21b, a new transiting exoplanet discovered by the Wide Angle Search for Planets (WASP) Consortium and established and characterized with the FIES, SOPHIE, CORALIE and HARPS fiber-fed echelle spectrographs. A 4.3-d period, 1.1% transit depth and 3.4-h duration are derived for WASP-21b using SuperWASP-North and high precision photometric observations at the Liverpool Telescope. Simultaneous fitting to the photometric and radial velocity data with a Markov Chain Monte Carlo procedure leads to a planet in the mass regime of Saturn. With a radius of 1.07 R_Jup and mass of 0.30 M_Jup, WASP-21b has a density close to 0.24 rho_Jup corresponding to the distribution peak at low density of transiting gaseous giant planets. With a host star metallicity [Fe/H] of -0.46, WASP-21b strengthens the correlation between planetary density and host star metallicity for the five known Saturn-like transiting planets. Furthermore there are clear indications that WASP-21b is the first transiting planet belonging to the thick disc.

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