C. Reylé

University of Franche-Comté, Becoinson, Franche-Comté, France

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Publications (119)216.45 Total impact

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    ABSTRACT: We present a method designed to detect QSOs near the Galactic Plane, based on their optical photometric variability, and we analyze its performance using data from the CIDA Low Latitude Variability Survey (CLLVS). This survey contains photometric data from extended and adjacent regions of the Milky Way disk. In this work we have analyzed 2.5 square degrees of the survey . We have selected a sample of 288 QSOs candidates using the variability, the periodicity, and the Structure Function. We obtain a low efficiency in recovering previously reported QSOs in the SDSS (≈5%), however we expect a high degree of contamination. Additionally, we present preliminary results of follow-up spectroscopic observations carried on at CASLEO (Argentina). The results shown in this work are a first attempt to develop a robust method to detect QSOs in the Galactic Plane in the era of massive surveys such as VISTA and Gaia.
    Semaine de l'Astrophysique Française, Toulouse; 06/2015
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    ABSTRACT: The Besançon Galaxy model (BGM) is used to compare the infrared colour and [M/H] metallicity distributions of stars with those from 2MASS and APOGEE observations taking the selection function of the data into account, across a large volume of the inner part of the Galaxy. For this purpose we model the mass density distribution of the inner stellar halo by a 6-parameters double power-law model, and reconstruct the behaviour of the rotation curve in the inner part of the Milky Way.
    Semaine de l'Astrophysique Française, Toulouse; 06/2015
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    ABSTRACT: We report the discovery of 14 low-mass binary systems containing mid-M to mid-L dwarf companions with separations larger than 250 AU. We also report the independent discovery of 9 other systems with similar characteristics that were recently discovered in other studies. We have identified these systems by searching for common proper motion sources in the vicinity of known high proper motion stars, based on a cross-correlation of wide area near-infrared surveys (2MASS, SDSS, and SIMP). An astrometric follow-up, for common proper motion confirmation, was made with SIMON and/or CPAPIR at the OMM 1.6 m and CTIO 1.5 m telescopes for all the candidates identified. A spectroscopic follow-up was also made with GMOS or GNIRS at Gemini to determine the spectral types of 11 of our newly identified companions and 10 of our primaries. Statistical arguments are provided to show that all of the systems we report here are very likely to be physical binaries. One of the new systems reported features a brown dwarf companion: LSPM J1259+1001 (M5) has an L4.5 (2M1259+1001) companion at about 340 AU. This brown dwarf was previously unknown. Seven other systems have a companion of spectral type L0-L1 at a separation in the 250-7500 AU range. Our sample includes 14 systems with a mass ratio below 0.3.
    The Astrophysical Journal 01/2015; 802(1). DOI:10.1088/0004-637X/802/1/37 · 6.28 Impact Factor
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    ABSTRACT: We present a preliminary attempt to compute a non-axisymmetric potential together with the previous axisymmetric potential of the Besançon galaxy model (hereafter BGM). The contribution by non-axisymmetric components are modeled by Pichardo et al. (2004) method: This consists in the superposition of inhomogeneous ellipsoids to approximate the triaxial bar and superposition of homogeneous oblate spheroids for a stellar halo, possibly triaxial. Finally, we have computed the potential and force field for these non-axisymmetric components in order to constraint the total mass of the Milky Way. We present the preliminary results for the new fit to the rotation curve and constraints on the dark halo shape. This approach allows us to use the new dynamical constraints, together with mocked kinematical information to compare with upcoming data from large-scale survey such as RAVE, BRAVA, APOGEE, and GAIA in the near future. 1. Apply the Schwarzschild method to this new potential. 2. Study the influence of the potential produced by a three-dimensional Spiral Arms model (Pichardo et al. 2003) within the BGM. 3. New values for age-velocity dispersion relation are explored, from RAVE data (Robin et al. 2015, in preparation). 4. Performing simulations with test particles, in order to probe the local effect of the bar and derive the general kinematics of the stars under a triaxial bar potential. Figure 3: Left: Superposition of homogeneous oblate spheroids to approximate the density law for the stellar halo given in Robin et al. (2015, in preparation); n = 4.39 and R core = 2.128 kpc. Right: Force field along the R-plane (top), z-axis (bottom) in the superposition model of homogeneous oblate spheroid.
    “The Milky Way Unraveled by Gaia”, GREAT meeting; 12/2014
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    ABSTRACT: We study the shape of the thick disc using photometric data at high and intermediate latitudes from SDSS and 2MASS surveys. We use the population synthesis approach using an ABC-MCMC method to characterize the thick disc shape, scale height, scale length, local density and flare, and we investigate the extend of the thick disc formation period by simulating several formation episodes. We find that the vertical variation in density is not exponential, but much closer to an hyperbolic secant squared. Assuming a single formation epoch, the thick disc is better fitted with a sech2 scale height of 470 pc and a scale length of 2.3 kpc. However if one simulates two successive formation episodes, mimicking an extended formation period, the older episode has a higher scale height and a larger scale length than the younger episode, indicating a contraction during the collapse phase. The scale height range from 800 pc to 340 pc, and the scale length from 3.2 kpc to 2 kpc. The star formation increases from the old episode to the young one. During the fitting process, the halo parameters are also determined. The constraint on the halo shows that a transition between a inner and outer halo, if exists, cannot be at a distance of less than about 30 kpc, which is the limit of our investigation using turnoff halo stars. Finally we show that the extrapolation of the thick disc towards the bulge region is important enough that there is no longer need for a classical bulge. To explain these results, the most probable scenario for the thick disc is that it formed while the Galaxy was gravitationally collapsing from well mixed gas-rich giant clumps sustained by high turbulence which awhile prevent a thin disc to form, as proposed by Bournaud et al. (2009). This scenario explains the observations in the thick disc region as well as in the bulge region. (abridged)
    Astronomy and Astrophysics 06/2014; 569. DOI:10.1051/0004-6361/201423415 · 4.48 Impact Factor
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    ABSTRACT: Aims: An effort has been undertaken to simulate the expected Gaia Catalogue, including the effect of observational errors. A statistical analysis of this simulated Gaia data is performed in order to better understand what can be obtained from the Gaia astrometric mission. This catalogue is used in order to investigate the potential yield in astrometric, photometric and spectroscopic information, and the extent and effect of observational errors on the true Gaia Catalogue. This article is a follow-up to Robin et. al. (2012), where the expected Gaia Catalogue content was reviewed but without the simulation of observational errors. Methods: The Gaia Object Generator (GOG) catalogue is analysed using the Gaia Analysis Tool (GAT), producing a number of statistics on the catalogue. Results: A simulated catalogue of one billion objects is presented, with detailed information on the 523 million individual single stars it contains. Detailed information is provided for the expected errors in parallax, position, proper motion, radial velocity, photometry in the four Gaia bands, and physical parameter determination including temperature, metallicity and line of sight extinction.
    Astronomy and Astrophysics 04/2014; 566. DOI:10.1051/0004-6361/201423636 · 4.48 Impact Factor
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    ABSTRACT: Aims: An effort has been undertaken to simulate the expected Gaia Catalogue, including the effect of observational errors. A statistical analysis of this simulated Gaia data is performed in order to better understand what can be obtained from the Gaia astrometric mission. This catalogue is used in order to investigate the potential yield in astrometric, photometric and spectroscopic information, and the extent and effect of observational errors on the true Gaia Catalogue. This article is a follow-up to Robin et. al. (2012), where the expected Gaia Catalogue content was reviewed but without the simulation of observational errors. Methods: The Gaia Object Generator (GOG) catalogue is analysed using the Gaia Analysis Tool (GAT), producing a number of statistics on the catalogue. Results: A simulated catalogue of one billion objects is presented, with detailed information on the 523 million individual single stars it contains. Detailed information is provided for the expected errors in parallax, position, proper motion, radial velocity, photometry in the four Gaia bands, and physical parameter determination including temperature, metallicity and line of sight extinction.
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    ABSTRACT: Context. M subdwarfs are metal poor and cool stars. They are important probes of the old galactic populations. However, they remain elusive due to their low luminosity. Observational and modeling efforts are required to fully understand their physics and to investigate the effects of metallicity in their cool atmospheres. Aims. We perform a detailed study of a sample of subdwarfs to determine their stellar parameters and constrain the stat-of-the art atmospheric models. Methods. We present UVES/VLT high resolution spectra of three late-K subdwarfs and 18 M subdwarfs. Our atlas covers the optical region from 6400 AA up to the near infrared at 8900 AA. We show spectral details of cool atmospheres at very high resolution (R= 40 000) and compare with synthetic spectra computed from the recent BT-Settl atmosphere models. Results. Our comparison shows that molecular features (TiO, VO, CaH), and atomic features (Fe I, Ti I, Na I, K I) are well fitted by current models. We produce an effective temperature versus spectral type relation all over the subdwarf spectral sequence. Thanks to the high resolution of our spectra, we perform a detailed comparison of line profiles of individual elements such as Fe I, Ca II, Ti I, and are able to determine accurate metallicities of these stars. These determinations contribute to calibrate the relation between metallicity and molecular band strength indices from low-resolution spectra. Conclusions. This work shows that the new generation of models are able to reproduce various spectral features of M subdwarfs. Working with these high resolution spectra allowed us to disentangle the atmospheric parameters (effective temperature, gravity, metallicity), which is not possible when using low resolution spectroscopy or photometry.
    Astronomy and Astrophysics 01/2014; 564. DOI:10.1051/0004-6361/201322881 · 4.48 Impact Factor
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    ABSTRACT: M subdwarfs are metal poor and cool stars. They are important probes of the old galactic populations. However, they remain elusive due to their low luminosity. Observational and modeling efforts are required to fully understand the physics and to investigate the effect of metallicity in their cool atmo- spheres. We perform a detail study of a sample of subdwarfs to determine their stellar parameters and constrain the atmosphere models. We present UVES/VLT high resolution spectra of 21 M subdwarfs. Our atlas covers the optical region from 6400{\deg}A up to the near infrared at 10000{\deg}A. We show spectral details of cool atmospheres at very high resolution (R = 40 000) and compare with synthetic spectra computed from the recent BT-Settl atmosphere models. Our comparison shows that molecular features (TiO, VO, CaH), and atomic features (Fe, Ti, Na, K) are well fitted by current models. We produce an effective temperature versus spectral type relation all over the subdwarf spectral sequence.
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    ABSTRACT: Stellar-substellar binary systems are quite rare, and provide interesting benchmarks. They constrain the complex physics of substellar atmospheres, because several physical parameters of the substellar secondary can be fixed from the much better characterized main sequence primary. We report the discovery of CFBDS J111807-064016, a T2 brown dwarf companion to 2MASS J111806.99-064007.8, a low-mass M4.5-M5 star. The brown-dwarf was identified from the Canada France Brown Dwarf Survey. At a distance of 50-120 pc, the 7.7 arcsec angular separation corresponds to projected separations of 390-900 AU. The primary displays no Halpha emission, placing a lower limit on the age of the system of about 6 Gyr. The kinematics is also consistent with membership in the old thin disc. We obtained near-infrared spectra, which together with recent atmosphere models allow us determine the effective temperature and gravity of both components. From these parameters and the age constraint, evolutionary models estimate masses of 0.10 to 0.15 Msol for the M dwarf, and 0.06 to 0.07 Msol for the T dwarf. This system is a particularly valuable benchmark because the brown dwarf is an early T: the cloud-clearing that occurs at the L/T transition is very sensitive to gravity, metallicity, and detailed dust properties, and produces a large scatter in the colours. This T2 dwarf, with its metallicity measured from the primary and its mass and gravity much better constrained than those of younger early-Ts, will anchor our understanding of the colours of L/T transition brown dwarfs. It is also one of the most massive T dwarfs, just below the hydrogen-burning limit, and all this makes it a prime probe a brown dwarf atmosphere and evolution models.
    Astronomy and Astrophysics 09/2013; 561. DOI:10.1051/0004-6361/201322107 · 4.48 Impact Factor
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    ABSTRACT: We are carrying out a large ancillary program with the SDSS-III, using the fiber-fed multi-object NIR APOGEE spectrograph, to obtain high-resolution H-band spectra of more than 1200 M dwarfs. These observations are used to measure spectroscopic rotational velocities, radial velocities, physical stellar parameters, and variability of the target stars. Here, we describe the target selection for this survey and results from the first year of scientific observations based on spectra that is publicly available in the SDSS-III DR10 data release. As part of this paper we present RVs and vsini of over 200 M dwarfs, with a vsini precision of ~2 km/s and a measurement floor at vsini = 4 km/s. This survey significantly increases the number of M dwarfs studied for vsini and RV variability (at ~100-200 m/s), and will advance the target selection for planned RV and photometric searches for low mass exoplanets around M dwarfs, such as HPF, CARMENES, and TESS. Multiple epochs of radial velocity observations enable us to identify short period binaries, and AO imaging of a subset of stars enables the detection of possible stellar companions at larger separations. The high-resolution H-band APOGEE spectra provide the opportunity to measure physical stellar parameters such as effective temperatures and metallicities for many of these stars. At the culmination of this survey, we will have obtained multi-epoch spectra and RVs for over 1400 stars spanning spectral types of M0-L0, providing the largest set of NIR M dwarf spectra at high resolution, and more than doubling the number of known spectroscopic vsini values for M dwarfs. Furthermore, by modeling telluric lines to correct for small instrumental radial velocity shifts, we hope to achieve a relative velocity precision floor of 50 m/s for bright M dwarfs. We present preliminary results of this telluric modeling technique in this paper.
    The Astronomical Journal 07/2013; 146(6). DOI:10.1088/0004-6256/146/6/156 · 4.05 Impact Factor
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    ABSTRACT: The launch of Gaia satellite of ESA is approaching (scheduled in 2013) and the scientific community is preparing for the maximal scientific return. As white dwarfs are very faint (especially in the very cool regime, Teff ≤ 5,000 K), they are very hard to detect and only the closest ones have been observed until now. Gaia, through its 5--6 years survey of the whole sky up to magnitude 20-25 (depending on the colour of the source), will drastically increase the sample of known white dwarfs and provide a lot of new science in this field. Using synthetic spectral energy distribution libraries and the most recent Gaia transmission curves, we derive colours of three different kinds of white dwarfs (pure hydrogen, pure helium and mixed composition with H/He=0.1). With these colours we derive transformations to other common photometric systems (Johnson-Cousins, Sloan Digital Sky Survey and 2MASS). Different relationships have to be considered for different white dwarfs compositions. Pure-He white dwarfs show an unique behaviour valid at different temperatures, but pure-H white dwarfs need to be analysed in two different temperature regimes, as their behaviour changes around Teff =5,000 K. We also compare the estimations of number of white dwarfs as predicted by the Gaia Universe Model Snapshot and by a different model of white dwarfs population (Napiwotzky's simulations). Among all white dwarfs observed, the most interesting ones will be those in the very cool regime. According to our simulations, Gaia will be able to observe thousands of them for the first time.
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    ABSTRACT: Despite their large number in the Galaxy, M dwarfs remain elusive objects and the modeling of their photospheres has long remained a challenge (molecular opacities, dust cloud formation). Our objectives are to validate the BT-Settl model atmospheres, update the M dwarf T eff -spectral type relation, and find the atmospheric parameters of the stars in our sample. We compare two samples of optical spectra covering the whole M dwarf sequence with the most recent BT-Settl synthetic spectra and use a \c{hi}2 minimization technique to determine Teff . The first sample consists of 97 low-resolution spectra obtained with NTT at La Silla Observatory. The second sample contains 55 mid-resolution spectra obtained at the Siding Spring Observatory (SSO). The spectral typing is realized by comparison with already classified M dwarfs. We show that the BT-Settl synthetic spectra reproduce the slope of the spectral energy distribution and most of its features. Only the CaOH band at 5570{\AA} and AlH and NaH hydrides in the blue part of the spectra are still missing in the models. The Teff-scale obtained with the higher resolved SSO 2.3 m spectra is consistent with that obtained with the NTT spectra. We compare our Teff scale with those of other authors and to published isochrones using the BT-Settl colors. We also present relations between effective temperature, spectral type and colors of the M dwarfs.
    Astronomy and Astrophysics 04/2013; 556. DOI:10.1051/0004-6361/201321346 · 4.48 Impact Factor
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    ABSTRACT: The launch of the Gaia satellite of ESA is approaching (scheduled in 2013) and the scientific community is preparing for the maximal scientific return. As white dwarfs (WDs) are very faint, (especially in the cool domain, Teff < 5 000K) they have been very hard to detect and only the closest ones have been observed until now. Gaia, through its 5-6 years survey of the whole sky down to magnitude 20-25 (depending on the colour of the source), will detect many faint WDs and most importantly, provide parallaxes for them. We provide a new characterisation of Gaia photometry for the case of WDs, deriving Gaia magnitudes and colours for WDs. Some transformations between some of the most common photometric systems and Gaia passbands are also derived to allow predictions of how WDs will be seen by Gaia.
    01/2013;
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    ABSTRACT: We present an optical spectral atlas of stars covering the whole M-dwarf sequence. It consists of 95 M dwarfs at solar metallicity observed at low-resolution with EMMI@NTT and 21 M-subdwarfs, extreme-subdwarfs and ultra-subdwarfs observed at high resolution with UVES@VLT. Using the most recent PHOENIX BT-Settl stellar model atmospheres we perform a detailed comparison with our observed spectra using χ^2 minimization technique. We confront the models with low-resolution spectra of M dwarfs at solar metallicity and we assign effective temperatures to the M dwarfs. We present temperature versus spectral type and colour relations and their comparison with others found in the literature. We also present our high-resolution spectra of the subdwarfs (sdM, esdM, usdM) and compare them to the newest grid of the BT Settl models which uses the revised solar abundances of Caffau et al (2011). This comparison allows us to study the spectral details of cool atmospheres, to determine precise [Fe/H] values for our objects, and to investigate the effect of metallicity on cool dwarf atmospheres. This study also helps to validate the atmosphere models and improve them by determining new constants on molecular opacities, dust cloud formation etc.
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    ABSTRACT: Using the CFBDSIR wide field survey for brown dwarfs, we identified CFBDSIRJ214947.2-040308.9, a late T dwarf with atypically red J-Ks colour. We obtained an X-Shooter spectra, with signal detectable from 0.8 to 2.3 micron, which confirmed a T7 spectral type with an enhanced Ks-band flux indicative of a potentially low-gravity, young, object. The comparison of our near infrared spectrum with atmosphere models, for solar metallicity, shows that CFBDSIRJ214947.2-040308.9 is probably a 650-750 K, log g=3.75-4.0 substellar object. Using evolution models, this translates into a planetary mass object, with an age in the 20-200 Myr range. An independent Bayesian analysis from proper motion measurements results in a 87% probability that this free-floating planet is a member of the 50-120 Myr old AB Doradus moving group, which strengthens the spectroscopic youth diagnosis. By combining our atmospheric characterisation with the age and metallicity constraints arising from the probable membership to the AB Doradus moving group, we find that CFBDSIRJ214947.2-040308.9 is probably a 4-7 Jupiter masses free-floating planet with an effective temperature of ~700K and a log g of ~4.0, typical of the late T-type exoplanets that are targeted by direct imaging. We stress that this object could be used as a benchmark for understanding the physics of the similar T-type exoplanets that will be discovered by the upcoming high contrast imagers.
    Astronomy and Astrophysics 10/2012; 548. DOI:10.1051/0004-6361/201219984 · 4.48 Impact Factor
  • EAS Publications Series 09/2012;
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    ABSTRACT: LHS1070 is a nearby multiple system of low mass stars. It is an important source of information for probing the low mass end of the main sequence, down to the hydrogen-burning limit. The primary of the system is a mid-M dwarf and two components are late-M to early L dwarfs, at the star-brown dwarf transition. Hence LHS1070 is a valuable object to understand the onset of dust formation in cool stellar atmospheres.This work aims at determining the fundamental stellar parameters of LHS1070 and to test recent model atmospheres: BT-Dusty,BT-Settl, DRIFT, and MARCS models.Unlike in previous studies, we have performed a chi^2-minimization comparing well calibrated optical and infrared spectra with recent cool star synthetic spectra leading to the determination of the physical stellar parameters Teff, radius, and log g for each of the three components of LHS1070.
    Astronomy and Astrophysics 08/2012; 545. DOI:10.1051/0004-6361/201219029 · 4.48 Impact Factor
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    ABSTRACT: Unlike in previous studies, we have performed a {chi}2-minimi comparing well calibrated optical and infrared spectra with recent cool star synthetic spectra leading to the determination of the physical stellar parameters Teff, radius, and logg for each of the three components of LHS 1070. (5 data files).
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    ABSTRACT: This study has been developed in the framework of the computational simulations that are executed for the preparation of the ESA Gaia astrometric mission. We focus on describing the objects and characteristics that Gaia will potentially observe without taking into consideration instrumental effects (detection efficiency, observing errors). The theoretical Universe model prepared for the Gaia simulation has been statistically analysed at a given time. Ingredients of the model are described, with the greatest emplasis on the stellar content, the double and multiple stars, and variability. ************************************************************************** * * * The simulated catalogue will be soon available * * * **************************************************************************

Publication Stats

2k Citations
216.45 Total Impact Points

Institutions

  • 2009–2014
    • University of Franche-Comté
      • Institut UTINAM
      Becoinson, Franche-Comté, France
  • 2006–2007
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2005
    • Hue University
      Huế, Thừa Thiên-Huế, Vietnam
  • 2001
    • Université de Bretagne Sud
      Lorient, Brittany, France