C. Reylé

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

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Publications (125)228.96 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Using six-dimesional phase-space information from the Fourth Data release of the Radial Velocity Experiment (RAVE) over the range of Galactic longitude 240 • < l < 360 • and V LS R < −239 kms −1 , we have computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to ω Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of ω Centauri due to the tidal effects of the Galaxy disk on the cluster along time. We also ignored secular changes in the Milky Way potential over time. In a Monte Carlo scheme, and under the assumption that the stars may have been ejected with velocities greater than the escape velocity (V rel > V esc,0) from the cluster, we identified 15 stars as having close encounters with ω Centauri: (i) 8 stars with relative velocities V rel < 200 kms −1 may have been ejected ∼ 200 Myr ago from ω Centauri; (ii) other group of 7 stars were identified with high relative velocity V rel > 200 kms −1 during close encounters, and seems unlikely that they have been ejected from ω Centauri. We also confirm the link between J131340.4-484714 as potential member of ω Centauri, and probably ejected ∼ 2.0 Myr ago, with a relative velocity V rel ∼ 80 kms −1 .
    No preview · Article · Aug 2015 · Astronomy and Astrophysics
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    ABSTRACT: The most accurate 6D phase-space information from the Radial Velocity Experiment (RAVE) was used to integrate the orbits of 105 stars around the galactic globular cluster 47 Tucanae, over the distance range 2 kpc < d < 6 kpc. Using the uncertainties in the current position and velocity vector for both the star and cluster, 10 5 pairs of star-cluster orbits were generated in a Monte Carlo numerical scheme. We integrated the orbits over 1000 Myr and 300 Myr, considering an axisymmetric and non-axisymmetric Milky-Way-like Galactic potential, respectively, and looked for close encounters in the past with a minimum distance approach less than the cluster tidal radius, between stars in the RAVE survey around 47 Tucanae and the cluster itself. In this scheme, we identified 30 potential cluster members that had close encounters with the globular cluster 47 Tucanae, all of which are shown to have a relative velocity distribution (V rel) less than 200 kms −1. Among these potential members, 9 had close encounters with the cluster with velocities less than the escape velocity of 47 Tucanae, therefore a scenario of " tidal stripping " seems likely, while for the other 21 stars V rel exceeds the escape velocity of the cluster, therefore they were likely " ejected ". The number of stars found in and out the tidal radius during our simulations, is comparable to the escape rate for 47 Tucanae estimated to be about 14 stars per Myr.
    No preview · Article · Aug 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using six-dimesional phase-space information from the Fourth Data release of the Radial Velocity Experiment (RAVE) over the range of Galactic longitude 240 • < l < 360 • and V LS R < −239 kms −1 , we have computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to ω Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of ω Centauri due to the tidal effects of the Galaxy disk on the cluster along time. We also ignored secular changes in the Milky Way potential over time. In a Monte Carlo scheme, and under the assumption that the stars may have been ejected with velocities greater than the escape velocity (V rel > V esc,0) from the cluster, we identified 15 stars as having close encounters with ω Centauri: (i) 8 stars with relative velocities V rel < 200 kms −1 may have been ejected ∼ 200 Myr ago from ω Centauri; (ii) other group of 7 stars were identified with high relative velocity V rel > 200 kms −1 during close encounters, and seems unlikely that they have been ejected from ω Centauri. We also confirm the link between J131340.4-484714 as potential member of ω Centauri, and probably ejected ∼ 2.0 Myr ago, with a relative velocity V rel ∼ 80 kms −1 .
    No preview · Article · Jul 2015 · Astronomy and Astrophysics
  • Dataset: RAVE V5

    No preview · Dataset · Jul 2015
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    ABSTRACT: We present preliminary results of the CIDA Equatorial Variability Survey (CEVS), looking for quasar (hereafter QSO) candidates near the Galactic plane. The CEVS contains photometric data from extended and adjacent regions of the Milky Way disk ($\sim$ 500 sq. deg.). In this work 2.5 square degrees with moderately high temporal sampling in the CEVS were analyzed. The selection of QSO candidates was based on the study of intrinsic optical photometric variability of 14,719 light curves. We studied samples defined by cuts in the variability index (Vindex $>$ 66.5), periodicity index (Q $>$ 2), and the distribution of these sources in the plane (AT , ${\gamma}$), using a slight modification of the first-order of the structure function for the temporal sampling of the survey. Finally, 288 sources were selected as QSO candidates. The results shown in this work are a first attempt to develop a robust method to detect QSO towards the Galactic plane in the era of massive surveys such as VISTA and Gaia.
    No preview · Conference Paper · Jun 2015
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    ABSTRACT: The Besan\c{c}on Galaxy model was used to compare the infrared colour distribution of synthetic stars with those from 2MASS observations taking the selection function of the data into account, in order to study the shape of the stellar halo of the Milky Way, with complemetary spectroscopic data from SDSS-III/APOGEE survey. Furthermore, we compared the generated mock metallicity distribution of the Besan\c{c}on Galaxy model, to the intrinsic metallicity distribution with reliable stellar parameters from the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP). The comparison was carried accross a large volume of the inner part of the Galaxy, revealing that a metal-poor population, [M/H]$<-1.2$ dex, could fill an extended component of the inner galactic halo. With this data set, we are able to model a more realistic mass density distribution of the stellar halo component of the Milky Way, assuming a six-parameters double power-law model, and reconstruct the behaviour of the rotation curve in the inner part of the Galaxy.
    No preview · Conference Paper · Jun 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.
    Full-text · Article · Jan 2015 · The Astrophysical Journal
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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.
    No preview · Conference Paper · Dec 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)
    Full-text · Article · Jun 2014 · Astronomy and Astrophysics
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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.
    Full-text · Article · Apr 2014 · Astronomy and Astrophysics
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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.
    Full-text · Article · Mar 2014
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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.
    Full-text · Article · Jan 2014 · Astronomy and Astrophysics
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    ABSTRACT: Two new analysis of SDSS and 2MASS surveys are used to constrain the characteristics of the thin and thick disc of the Milky Way, based on a population synthesis model and a MCMC scheme to constrain model parameters. These studies show that 1) the thick disc has been formed during an extended period of time and it was contracting during this phase; 2) the external thin disc is shown to have characteristics which vary with age such as the scale length, warp orientation, warp and flare slopes. The thick disc undergoing a contraction with time while the thin disc forming inside-out clearly indicate that they are truly distinct components of the Galaxy.
    No preview · Article · Jan 2014 · EAS Publications Series

  • No preview · Article · Jan 2014
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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.
    Full-text · Article · Sep 2013
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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.
    Full-text · Article · Sep 2013 · Astronomy and Astrophysics
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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.
    Full-text · Article · Jul 2013 · The Astronomical Journal
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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.
    No preview · Article · May 2013
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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.
    Full-text · Article · Apr 2013 · Astronomy and Astrophysics
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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.
    No preview · Article · Jan 2013

Publication Stats

3k Citations
228.96 Total Impact Points

Institutions

  • 2008-2015
    • University of Franche-Comté
      • Institut UTINAM
      Becoinson, Franche-Comté, France
  • 2011
    • Université de Montréal
      Montréal, Quebec, Canada
  • 2002-2008
    • French National Centre for Scientific Research
      • Institut d'astrophysique spatiale (IAS)
      Lutetia Parisorum, Île-de-France, France