References of "Bonfils, Xavier"
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See detailA rocky planet transiting a nearby low-mass star
Berta-Thompson, Zachory K.; Irwin, Jonathan; Charbonneau, David et al

in Nature (2015), 527

M-dwarf stars—hydrogen-burning stars that are smaller than 60 per cent of the size of the Sun—are the most common class of star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1. Recent ... [more ▼]

M-dwarf stars—hydrogen-burning stars that are smaller than 60 per cent of the size of the Sun—are the most common class of star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1. Recent results have shown that M dwarfs host Earth-sized planets in great numbers: the average number of M-dwarf planets that are between 0.5 to 1.5 times the size of Earth is at least 1.4 per star. The nearest such planets known to transit their star are 39 parsecs away, too distant for detailed follow-up observations to measure the planetary masses or to study their atmospheres. Here we report observations of GJ 1132b, a planet with a size of 1.2 Earth radii that is transiting a small star 12 parsecs away. Our Doppler mass measurement of GJ 1132b yields a density consistent with an Earth-like bulk composition, similar to the compositions of the six known exoplanets with masses less than six times that of the Earth and precisely measured densities. Receiving 19 times more stellar radiation than the Earth, the planet is too hot to be habitable but is cool enough to support a substantial atmosphere, one that has probably been considerably depleted of hydrogen. Because the host star is nearby and only 21 per cent the radius of the Sun, existing and upcoming telescopes will be able to observe the composition and dynamics of the planetary atmosphere. [less ▲]

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See detailIndependant analysis of Spitzer and HARPS : the still lonely and metal-rich GJ 436b
Lanotte, Audrey ULg; Gillon, Michaël ULg; Demory, Brice-Olivier et al

Poster (2014, April 30)

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See detailSpitzer Observations of GJ3470b: a Very Low-density Neptune-size Planet Orbiting a Metal-rich M dwarf
Demory, Brice-Olivier; Torres, Guillermo; Neves, Vasco et al

in Astrophysical Journal (2013)

We present Spitzer/IRAC 4.5-micron transit photometry of GJ3470b, a Neptune-size planet orbiting a M1.5 dwarf star with a 3.3-day period recently discovered in the course of the HARPS M-dwarf survey. We ... [more ▼]

We present Spitzer/IRAC 4.5-micron transit photometry of GJ3470b, a Neptune-size planet orbiting a M1.5 dwarf star with a 3.3-day period recently discovered in the course of the HARPS M-dwarf survey. We refine the stellar parameters by employing purely empirical mass-luminosity and surface brightness relations constrained by our updated value for the mean stellar density, and additional information from new near-infrared spectroscopic observations. We derive a stellar mass of M_star = 0.539+0.047-0.043 M_sun and a radius of R_star = 0.568+0.037-0.031 R_sun. We determine the host star of GJ3470b to be metal-rich, with a metallicity of [Fe/H] = +0.20 +/- 0.10 and an effective temperature of Teff = 3600 +/- 100 K. The revised stellar parameters yield a planetary radius R_pl = 4.83+0.22-0.21 R_Earth that is 13 percent larger than the value previously reported in the literature. We find a planetary mass M_pl = 13.9+1.5-1.4 M_Earth that translates to a very low planetary density, rho_pl = 0.72+0.13-0.12 gcm-3, which is 33% smaller than the original value. With a mean density half of that of GJ436b, GJ3470b is an example of a very low-density low-mass planet, similar to Kepler-11d, Kepler-11e, and Kepler-18c but orbiting a much brighter nearby star that is more conducive to follow-up studies. [less ▲]

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See detailProspects for Near-infrared Characterisation of Hot Jupiters with the VLTI Spectro-imager (VSI)
Renard, Stéphanie; Absil, Olivier ULg; Berger, Jean-Philippe et al

in Moorwood, A. (Ed.) Science with the VLT in the ELT Era (2009)

Since the discovery of the first exoplanet around 51 Pegasi, the study of planetary systems receives an increasing attention, with the development and test of more and more detection techniques. Among the ... [more ▼]

Since the discovery of the first exoplanet around 51 Pegasi, the study of planetary systems receives an increasing attention, with the development and test of more and more detection techniques. Among the direct detection techniques, interferometry is one of the most promising for the near future. It already provides the required angular resolution, but the dynamic range needs to be improved. The detection and characterisation of extrasolar planets is one of the main science cases of the 2nd generation VLTI Spectro-Imager instrument (VSI). The goal of this work is to study the feasibility of obtaining near-infrared spectra of bright extrasolar giant planets (EGP) with VSI. [less ▲]

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See detailScience case for 1 mas spectro-imagining in the near-infrared
Garcia, Paulo J V; Berger, Jean-Phillipe; Marconi, Alessandro et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

We present the work developed within the science team of the Very Large Telescope Interferometer Spectro-Imager (VSI) during the Phase A studies. VSI aims at delivering ~ 1 milliarcsecond resolution data ... [more ▼]

We present the work developed within the science team of the Very Large Telescope Interferometer Spectro-Imager (VSI) during the Phase A studies. VSI aims at delivering ~ 1 milliarcsecond resolution data cubes in the near-infrared, with several spectral resolutions up to 12 000, by combining up to 8 VLTI telescopes. In the design of an instrument, the science case plays a central role by supporting the instrument construction decision, defining the top-level requirements and balancing design options. The overall science philosophy of VSI was that of a general user instrument serving a broad community. The science team addressed themes which included several areas of astrophysics and illustrated specific modes of operation of the instrument: a) YSO disks and winds; b) Multiplicity of young stars; c) Exoplanets; d) Debris disks; e) Stellar surface imaging; f) The environments of evolved stars; g) AGN tori; h) AGN's Broad Line Region; i) Supermassive black-holes; and j) Microlensing. The main conclusions can be summarized as follows: a) The accessible targets and related science are extremely sensitive to the instrument limiting magnitude; the instrument should be optimized for sensitivity and have its own fringe tracker. b) Most of the science cases are readily achievable with on-axis fringe tracking, off-axis fringe tracking enabling extra science. c) In most targets (YSOs, evolved stars and AGNs), the interpretation and analysis of circumstellar/nuclear dust morphology requires direct access to the gas via spectral resolved studies of emission lines, requiring at least a spectral resolution of 2 500. d) To routinely deliver images at the required sensitivity, the number of telescopes in determinant, with 6 telescopes being favored. e) The factorial increase in the number of closure phases and visibilities, gained in a single observation, makes massive surveys of parameters and related science for the first time possible. f) High dynamic range imaging and very high dynamic range differential closure phase are possible allowing the study of debris disks and characterization of pegasides. g) Spectro-imaging in the near-infrared is highly complementary to ALMA, adaptive optics and interferometric imaging in the thermal infrared. [less ▲]

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See detailRecurring Outbursts and Nuclear Fragmentation of Comet C/2001 A2 (LINEAR)
Sekanina, Zdenek; Jehin, Emmanuel ULg; Boehnhardt, Hermann et al

in Astrophysical Journal (2002), 572

Analysis of the visual light curve and fragmentation sequence of comet C/2001 A2 (LINEAR) shows a strong temporal correlation between the onset of outbursts and separation of companion nuclei. This ... [more ▼]

Analysis of the visual light curve and fragmentation sequence of comet C/2001 A2 (LINEAR) shows a strong temporal correlation between the onset of outbursts and separation of companion nuclei. This scenario conforms to Sekanina's conceptual model for the release of sizable fragments of an inert dust mantle from the nucleus surface: an outburst is triggered as some of the mass rapidly disintegrates into fine dust. [less ▲]

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See detailSplit Comet C/2001 A2 (LINEAR)
Jehin, Emmanuel ULg; Boehnhardt, Hermann; Sekanina, Zdenek et al

in Earth, Moon, and Planets (2002), 90

Comet C/2001 A2 experienced several splitting events during its 2001 perihelion passage. The first break-up event was observed in March 2001 (IAUC 7616). In this paper we report the first results of our ... [more ▼]

Comet C/2001 A2 experienced several splitting events during its 2001 perihelion passage. The first break-up event was observed in March 2001 (IAUC 7616). In this paper we report the first results of our extensive imaging and spectroscopic monitoring campaign with ESO telescopes over several weeks before and after the perihelion passage on May 25 2001. [less ▲]

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