arXiv subjects

M. Mayor

Publications and source records attributed to M. Mayor.

At least 145 records · Page 8Linked to original sources

arXiv2009

WASP-16b: A new Jupiter-like planet transiting a southern solar analog

We report the discovery from WASP-South of a new Jupiter-like extrasolar planet, WASP-16b, which transits its solar analog host star every 3.12 days. Analysis of the transit photometry and radial velocity spectroscopic data leads to a planet with R_p = 1.008+-0.071 R_Jup and M_p =0.855+-0.059 M_Jup, orbiting a host star with R_* = 0.946+-0.054 R_sun and M_* = 1.022+-0.101 M_sun. Comparison of the high resolution stellar spectrum with synthetic spectra and stellar evolution models indicates the host star is a near-solar metallicity ([Fe/H]= 0.01+-0.10) solar analog (Teff = 5700+-150 K, log g= 4.5+-0.2) of intermediate age (Tau = 2.3+5.8-2.2 Gyr).

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arXiv2009

TRIMOR - three-dimensional correlation technique to analyze multi-order spectra of triple stellar systems; Application to HD188753

This paper presents a new algorithm, TRIMOR, to analyse multi-order spectra of triple systems. The algorithm is an extension of TRICOR, the three-dimensional correlation technique that derives the radial velocities of triple stellar systems from single-order spectra. The combined correlation derived from many orders enables the detection and the measurement of radial velocities of faint tertiary companions. The paper applied TRIMOR to the already available spectra of HD188753, a well known triple system, yielding the radial velocities of the faintest star in the system. This rendered the close pair of the triple system a double-lined spectroscopic binary, which led to a precise mass-ratio and an estimate of its inclination. The close-pair inclination is very close to the inclination of the wide orbit, consistent with the assertion that this triple system has a close to coplanar configuration.

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arXiv2009

Probing the Impact of Stellar Duplicity on Planet Occurrence

The presence of a stellar companion closer than ~100 AU is likely to affect planet formation and evolution. Yet, the precise effects and their actual impact on planet occurrence are still debated. To bring observational constraints, we have conducted with VLT/NACO a systematic adaptive optics survey for close stellar companions to 130 solar-type stars with and without planets. In this paper we present observational and preliminary statistical results from this survey. Observational results reveal about 20 true companions, of which 4 are new companions to planet-host stars. As to preliminary statistical results, they suggest that circumstellar giant planets are less frequent in binaries closer than ~100 AU than around single stars, in possible agreement with the theoretical studies that predict a negative impact of stellar duplicity on giant planet formation in binaries closer than ~100 AU. These statistical results will need confirmation, however, as they are severely limited by small sample sizes.

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arXiv2009

The HARPS search for southern extra-solar planets XVIII. An Earth-mass planet in the GJ 581 planetary system

The GJ 581 planetary system was already known to harbour three planets, including two super-Earths planets which straddle its habitable zone. We report here the detection of an additional planet -- GJ 581e -- with a minimum mass of 1.9 M_earth. With a period of 3.15 days, it is the innermost planet of the system and has a ~5% transit probability. We also correct our previous confusion of the orbital period of GJ 581d (the outermost planet) with a one-year alias, thanks to an extended time span and many more measurements. The revised period is 66.8 days, and locates the semi-major axis inside the habitable zone of the low mass star. The dynamical stability of the 4-planet system imposes an upper bound on the orbital plane inclination. The planets cannot be more massive than approximately 1.6 times their minimum mass.

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arXiv2009

The 0.5M$_J$ transiting exoplanet WASP-13b

We report the discovery of WASP-13b, a low-mass $ M_p = 0.46 ^{+ 0.06}_{- 0.05} M_J$ transiting exoplanet with an orbital period of $4.35298 \pm 0.00004$ days. The transit has a depth of 9 mmag, and although our follow-up photometry does not allow us to constrain the impact parameter well ($0 < b < 0.46$), with radius in the range $R_p \sim 1.06 - 1.21 R_J$ the location of WASP-13b in the mass-radius plane is nevertheless consistent with H/He-dominated, irradiated, low core mass and core-free theoretical models. The G1V host star is similar to the Sun in mass (M$_{*} = 1.03^{+0.11}_ {- 0.09} M_{\odot}$) and metallicity ([M/H]=$0.0\pm0.2$), but is possibly older ($8.5^{+ 5.5}_{- 4.9}$ Gyr).

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arXiv2009

Photometric and spectroscopic detection of the primary transit of the 111-day-period planet HD 80606 b

We report the detection of the primary transit of the extra-solar planet HD 80606 b, thanks to photometric and spectroscopic observations performed at Observatoire de Haute-Provence, simultaneously with the CCD camera at the 120-cm telescope and the SOPHIE spectrograph at the 193-cm telescope. We observed the whole egress of the transit and partially its central part, in both data sets with the same timings. The ingress occurred before sunset and was not observed. The full duration of the transit was between 9.5 and 17.2 hours. The data allows the planetary radius to be measured (Rp = 0.9 +- 0.1 RJup) and other parameters of the system to be refined. Radial velocity measurements show the detection of a prograde Rossiter-McLaughlin effect, and provide a hint for a spin-orbit misalignment. If confirmed, this misalignment would corroborate the hypothesis that HD 80606 b owes its unusual orbital configuration to Kozai migration. HD 80606 b is by far the transiting planet on the longest period detected today. Its unusually small radius reinforces the observed relationship between the planet radius and the incident flux received from the star and opens new questions for theory. Orbiting a quite bright star (V=9), it opens opportunities to numerous follow-up studies.

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arXiv2009

Stellar activity of planetary host star HD 189733

Extra-solar planet search programs require high-precision velocity measurements. They need to study how to disentangle radial-velocity variations due to Doppler motion from the noise induced by stellar activity. We monitored the active K2V star HD 189733 and its transiting planetary companion that has a 2.2-day orbital period. We used the high-resolution spectograph SOPHIE mounted on the 1.93-m telescope at the Observatoire de Haute-Provence to obtain 55 spectra of HD 189733 over nearly two months. We refined the HD 189733b orbit parameters and put limits on the eccentricity and on a long-term velocity gradient. After subtracting the orbital motion of the planet, we compared the variability of spectroscopic activity indices to the evolution of the radial-velocity residuals and the shape of spectral lines. The radial velocity, the spectral-line profile and the activity indices measured in HeI (5875.62 Å), Halpha (6562.81 Å) and the CaII H&K lines (3968.47 Åand 3933.66 Å, respectively) show a periodicity around the stellar rotation period and the correlations between them are consistent with a spotted stellar surface in rotation. We used such correlations to correct for the radial-velocity jitter due to stellar activity. This results in achieving high precision on the orbit parameters, with a semi-amplitude K = 200.56 \pm 0.88 m.s-1 and a derived planet mass of M_{P}=1.13 \pm 0.03 M$_{Jup}$.

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arXiv2009

The low density transiting exoplanet WASP-15b

We report the discovery of a low-density exoplanet transiting an 11th magnitude star in the Southern hemisphere. WASP-15b, which orbits its host star with a period P=3.7520656+-0.0000028d has a mass M_p=0.542+-0.050M_J and radius R_p=1.428+-0.077R_J, and is therefore the one of least dense transiting exoplanets so far discovered (rho_p=0.247+-0.035g cm^-3). An analysis of the spectrum of the host star shows it to be of spectral type around F5, with an effective temperature T_eff=6300+-100K and [Fe/H]=-0.17+-0.11.

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arXiv2009

Spectroscopic binaries among Hipparcos M giants I. Data, orbits, and intrinsic variations

This paper is a follow-up of the vast effort to collect radial velocity data for stars belonging to the Hipparcos survey. We aim at extending the orbital data available for binaries with M giant primaries. The data will be used in the companion papers of this series to (i) derive the binary frequency among M giants and compare it to that of K giants (Paper II), and (ii) analyse the eccentricity-period diagram and the mass-function distribution (Paper III). Keplerian solutions are fitted to radial-velocity data. However, for several stars, no satisfactory solution could be found, despite the fact that the radial-velocity standard deviation is larger than the instrumental error, because M giants suffer from intrinsic radial-velocity variations due to pulsations. We show that these intrinsic radial-velocity variations can be linked with both the average spectral-line width and the photometric variability. We present an extensive collection of spectroscopic orbits for M giants, with 12 new orbits, plus 17 from the literature. Moreover, to illustrate the fact that the large radial-velocity jitter present in Mira and semi-regular variables may easily be confused with orbital variations, we also present examples of pseudo-orbital variations (in S UMa, X Cnc and possibly in HD 115521, a former IAU radial-velocity standard). Because of this difficulty, M giants involving Mira variables were excluded from our monitored sample. We finally show that the majority of M giants detected as X-ray sources are actually binaries.

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arXiv2009

Spectroscopic binaries among Hipparcos M giants II. Binary frequency

This paper is the second one in a series devoted to the study of properties of binaries involving M giants. The binary frequency of field M giants is derived and compared with the binary fraction of K giants. Diagrams of the CORAVEL spectroscopic parameter Sb (measuring the average line-width) vs. radial-velocity standard deviation for our samples are used to define appropriate binarity criteria. These then serve to extract the binarity fraction among the M giants. Comparison is made to earlier data on K giants binarity frequency. The Sb parameter is discussed in relation to global stellar parameters and the Sb vs. stellar radius relation is used to identify fast rotators. We find that the spectroscopic binary detection rate among field M giants, in a sample with a low number of velocity measurements (~2), unbiased toward earlier known binaries, is 6.3%. This is less than half of the analogous rate for field K giants, likely resulting from a real difference. This difference originates in the greater difficulty of finding binaries among M giants because of their smaller orbital velocity amplitudes and larger intrinsic jitter and in the different distributions of K and M giants in the eccentricity-period diagram. A larger detection rate was obtained in a smaller M giant sample with more radial velocity measurements per object: 11.1% confirmed plus 2.7% possible binaries. The CORAVEL spectroscopic parameter Sb was found to correlate better with the stellar radius than with either luminosity or effective temperature separately. Two outliers of the Sb vs. stellar radius relation, HD 190658 and HD 219654, have been recognized as fast rotators. The rotation is companion-induced, as both objects turn out to be spectroscopic binaries.

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arXiv2009

HD45364, a pair of planets in a 3:2 mean motion resonance

Precise radial-velocity measurements with the HARPS spectrograph reveal the presence of two planets orbiting the solar-type star HD45364. The companion masses are 0.187 Mjup and 0.658 Mjup, with semi-major axes of 0.681 AU and 0.897 AU, and eccentricities of 0.168 and 0.097, respectively. A dynamical analysis of the system further shows a 3:2 mean motion resonance between the two planets, which prevents close encounters and ensures the stability of the system over 5 Gyr. This is the first time that such a resonant configuration has been observed for extra-solar planets, although there is an analogue in our Solar System formed by Neptune and Pluto. This singular planetary system may provide important constraints on planetary formation and migration scenarios.

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arXiv2009

Discovery and characterization of WASP-6b, an inflated sub-Jupiter mass planet transiting a solar-type star

We report the discovery of WASP-6b, an inflated sub-Jupiter mass planet transiting every 3.3610060 +0.0000022-0.0000035 days a mildly metal-poor solar-type star of magnitude V=11.9. A combined analysis of the WASP photometry, high-precision followup transit photometry and radial velocities yield a planetary mass M_p = 0.503 +0.019-0.038 M_jup and radius R_p = 1.224 +0.051-0.052 R_jup, resulting in a density rho_p = 0.27 +-0.05 rho_jup. The mass and radius for the host star are M_s = 0.88 +0.05-0.08 M_sun and R_s = 0.870 +0.025-0.036 R_sun. The non-zero orbital eccentricity e = 0.054 +0.018-0.015 that we measure suggests that the planet underwent a massive tidal heating ~1 Gyr ago that could have contributed to its inflated radius. High-precision radial velocities obtained during a transit allow us to measure a sky-projected angle between the stellar spin and orbital axis Beta = 11 +14-18 deg. In addition to similar published measurements, this result favors a dominant migration mechanism based on tidal interactions with a protoplanetary disk.

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arXiv2008

The HARPS search for southern extra-solar planets. XVII. Super-Earth and Neptune-mass planets in multiple planet systems HD47186 and HD181433

This paper reports on the detection of two new multiple planet systems around solar-like stars HD47186 and HD181433. The first system includes a hot Neptune of 22.78 M_Earth at 4.08-days period and a Saturn of 0.35 M_Jup at 3.7-years period. The second system includes a Super-Earth of 7.5 M_Earth at 9.4-days period, a 0.64 M$_Jup at 2.6-years period as well as a third companion of 0.54 M_Jup with a period of about 6 years. These detections increase to 20 the number of close-in low-mass exoplanets (below 0.1 M_Jup) and strengthen the fact that 80% of these planets are in a multiple planetary systems.

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arXiv2008

WASP-10b: a 3M_J, gas-giant planet transiting a late-type K star

We report the discovery of WASP-10b, a new transiting extrasolar planet (ESP) discovered by the WASP Consortium and confirmed using NOT FIES and SOPHIE radial velocity data. A 3.09 day period, 29 mmag transit depth, and 2.36 hour duration are derived for WASP-10b using WASP and high precision photometric observations. Simultaneous fitting to the photometric and radial velocity data using a Markov-chain Monte Carlo procedure leads to a planet radius of 1.28R_J, a mass of 2.96M_J and eccentricity of ~0.06. WASP-10b is one of the more massive transiting ESPs, and we compare its characteristics to the current sample of transiting ESP, where there is currently little information for masses greater than ~2M_J and non-zero eccentricities. WASP-10's host star, GSC 2752-00114 (USNO-B1.0 1214-0586164) is among the fainter stars in the WASP sample, with V=12.7 and a spectral type of K5. This result shows promise for future late-type dwarf star surveys.

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arXiv2008

WASP-14b: 7.3 Mj transiting planet in an eccentric orbit

We report the discovery of a 7.3 Mjup exoplanet WASP-14b, one of the most massive transiting exoplanets observed to date. The planet orbits the tenth-magnitude F5V star USNO-B1 11118-0262485 with a period of 2.243752 days and orbital eccentricity e = 0.09. A simultaneous fit of the transit light curve and radial velocity measurements yields a planetary mass of 7.3+/-0.5 Mjup and a radius of 1.28+/-0.08 Rjup. This leads to a mean density of about 4.6 g/cm^3 making it densest transiting exoplanets yet found at an orbital period less than 3 days. We estimate this system to be at a distance of 160+/-20 pc. Spectral analysis of the host star reveals a temperature of 6475+/-100 K, log g = 4.07 cm/s^2 and vsin i = 4.9+/-1.0 km/s, and also a high lithium abundance, log N(Li} = 2.84+/-0.05. The stellar density, effective temperature and rotation rate suggest an age for the system of about 0.5-1.0 Gyr.

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arXiv2008

The HARPS search for southern extra-solar planets XVII. Six long-period giant planets around BD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377, HD 153950

We report the discovery of six new substellar companions of main-sequence stars, detected through multiple Doppler measurements with the instrument HARPS installed on the ESO 3.6m telescope, La Silla, Chile. These extrasolar planets are orbiting the stars BD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377, HD 153950. The orbital characteristics which best fit the observed data are depicted in this paper, as well as the stellar and planetary parameters. Masses of the companions range from 2 to 18 Jupiter masses, and periods range from 100 to 2000 days. The observational data are carefully analysed for activity-induced effects and we conclude on the reliability of the observed radial-velocity variations as of exoplanetary origin. Of particular interest is the very massive planet (or brown-dwarf companion) around the metal-rich HD 131664 with M2sini= 18.15 MJup, and a 5.34-year orbital period. These new discoveries reinforces the observed statistical properties of the exoplanet sample as known so far.

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arXiv2008

Extrasolar planets and brown dwarfs around A-F type stars VI. High precision RV survey of early type dwarfs with HARPS

(Abridged) Aims: Systematic surveys to search for exoplanets have been mostly dedicated to solar-type stars sofar. We developed in 2004 a method to extend such searches to earlier A-F type dwarfs and started spectroscopic surveys to search for planets and quantify the detection limit achievable when taking into account the stars properties and their actual levels of intrinsic variations. We give here the first results of our southern survey with HARPS. Results: 1) 64% of the 170 stars with enough data points are found to be variable. 20 are found to be binaries or candidate binaries (with stars or brown dwarfs). More than 80% or the latest type stars (once binaries are removed) are intrinsically variable at a 2 m/s precision level. Stars with earlier spectral type (B-V <= 0.2) are either variable or associated to levels of uncertainties comparable to the RV rms observed on variable stars of same B-V. 2) We have detected one long-period planetary system around an F6IV-V star. 3) We have quantified the jitter due to stellar activity and we show that taking into account this jitter in addition to the stellar parameters, it is still possible to detect planets with HARPS with periods of 3 days (resp. 10 days and 100 days) on 91% (resp. 83%, 61%) of them. We show that even the earliest spectral type stars are accessible to this type of search, provided they have a low vsini and low levels of activity. 4) Taking into account the present data, we compute the actually achieved detection limits for 107 targets and discuss the limits as a function of B-V. Given the data at hand, our survey is sensitive to short-period (few days) planets and to longer ones (100 days) at a lower extent (latest type stars). We derive first constrains on the presence of planets around A-F stars for these ranges of periods.

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arXiv2008

The sub-Jupiter mass transiting exoplanet WASP-11b

We report the discovery of a sub-Jupiter mass exoplanet transiting a magnitude V=11.7 host star 1SWASP J030928.54+304024.7. A simultaneous fit to the transit photometry and radial-velocity measurements yield a planet mass M_p=0.53+-0.07M_J, radius R_p=0.91^{+0.06}_{-0.03}R_J and an orbital period of 3.722465^{+0.000006}_{-0.000008} days. The host star is of spectral type K3V, with a spectral analysis yielding an effective temperature of 4800+-100K and log g=4.45+-0.2. It is amongst the smallest, least massive and lowest luminosity stars known to harbour a transiting exoplanet. WASP-11b is the third least strongly irradiated transiting exoplanet discovered to date, experiencing an incident flux F_p=1.9x10^8 erg s^{-1} cm^{-2} and having an equilibrium temperature T_eq=960+-70K.

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