J.-F. Le Campion

University of Bordeaux, Burdeos, Aquitaine, France

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Publications (80)162.51 Total impact

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    ABSTRACT: The nearby TW Hydrae Association (TWA) is currently a benchmark for the study of formation and evolution of young low-mass stars, circumstellar disks and the imaging detection of planetary companions. For such studies, it is crucial to evaluate the distance to group members in order to access their physical properties. Membership of several stars is strongly debated and age estimates vary from one author to another with doubts about coevality. We revisit the kinematic properties of the TWA in light of new trigonometric parallaxes and proper motions to derive the dynamical age of the association and physical parameters of kinematic members. Using observations performed with the NTT/ESO telescope we measured trigonometric parallaxes and proper motions for 13 stars in TWA. With the convergent point method we identify a co-moving group with 31 TWA stars. We deduce kinematic distances for 7 members of the moving group that lack trigonometric parallaxes. A traceback strategy is applied to the stellar space motions of a selection of 16 of the co-moving objects with accurate and reliable data yielding a dynamical age for the association of t = 7.5 +/- 0.7 Myr. Using our new parallaxes and photometry available in the literature we derive stellar ages and masses from theoretical evolutionary models. With new parallax and proper motion measurements from this work and current astrometric catalogs we provide an improved and accurate database for TWA stars to be used in kinematical analysis. We conclude that the dynamical age obtained via traceback strategy is consistent with previous age estimates for the TWA, and is also compatible with the average ages derived in the present paper from evolutionary models for pre-main sequence stars.
    01/2014;
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    ABSTRACT: The ESA Gaia mission, to be launched during 2013, will observe billions of objects, among which many galaxies, during its scanning of the sky. This will provide a large space-based dataset with unprecedented spatial resolution. Because of its natural Galactic and Astrometric priority, Gaia's observational strategy was optimized for point sources. Nonetheless, it is expected that 10^6 sources will be extragalactic, and a large portion of them will be angularly small galaxies. Although the mission was designed for point sources, a dedicated analysis of the raw data will allow the recovery of morphology of those objects at a 0.2" level. This may constitute a unique all-sky survey of such galaxies. We describe the conceptual design of the method we created for performing the morphological analysis of these objects as well as first results obtained from data simulations of low-resolution, highly binned, satellite data. Based on the obtained results we conclude that it is possible to push the limits of the Gaia space mission by analyzing galaxy morphology. (Abridged)
    Astronomy and Astrophysics 07/2013; · 5.08 Impact Factor
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    ABSTRACT: We have conducted a program of trigonometric distance measurements to 13 members of the TW Hydrae Association (TWA), which will enable us (through back-tracking methods) to derive a convincing estimate of the age of the association, independent of stellar evolutionary models. With age, distance, and luminosity known for an ensemble of TWA stars and brown dwarfs, models of early stellar evolution (which are still uncertain for young ages and substellar masses) will then be constrained by observations over a wide range of masses (0.025 to 0.7 M⊙).
    Proceedings of the International Astronomical Union 02/2013; 8(S289):386-389.
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    ABSTRACT: Context. The photometry of mutual occultations and eclipses of natural planetary satellites can be used to infer very accurate astrometric data. This can be achieved by processing the light curves of the satellites observed during international campaigns of photometric observations of these mutual events. Aims. This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Saturnian satellites made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods. We develop an accurate photometric model of mutual event observations of sufficiently high accuracy. Our original method is applied to derive astrometric data from photometric observations of the mutual occultations and eclipses of the Saturnian satellites. Results. We process the 26 light curves obtained during the international campaign of photometric observations of the Saturnian satellites in 2009. Compared with the theory TASS 1.7 by Vienne and Duriez, we find that the root mean square of the "O–C" residuals for the 23 highest quality observations are equal to 48.5 and 21.7 mas in right ascension and declination, respectively, we obtain 16.4 and 20.7 mas with the new theory by Lainey and collaborators and 17.3 and 21.6 mas with JPL SAT351 ephemerides. Topocentric or heliocentric angular differences for satellites pairs are obtained for 16 time instants during the time period from December 19, 2008 to July 16, 2009.
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    ABSTRACT: Context. The photometry of mutual occultations and eclipses of natural planetary satellites can be used to infer very accurate astrometric data. This can be achieved by processing the light curves of the satellites observed during international campaigns of photometric observations of these mutual events. Aims: This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Saturnian satellites made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods: We develop an accurate photometric model of mutual event observations of sufficiently high accuracy. Our original method is applied to derive astrometric data from photometric observations of the mutual occultations and eclipses of the Saturnian satellites. Results: We process the 26 light curves obtained during the international campaign of photometric observations of the Saturnian satellites in 2009. Compared with the theory TASS 1.7 by Vienne and Duriez, we find that the root mean square of the "O-C" residuals for the 23 highest quality observations are equal to 48.5 and 21.7 mas in right ascension and declination, respectively, we obtain 16.4 and 20.7 mas with the new theory by Lainey and collaborators and 17.3 and 21.6 mas with JPL SAT351 ephemerides. Topocentric or heliocentric angular differences for satellites pairs are obtained for 16 time instants during the time period from December 19, 2008 to July 16, 2009.
    Astronomy and Astrophysics 08/2012; 544:29. · 5.08 Impact Factor
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    ABSTRACT: We develop an accurate photometric model of mutual event observations of sufficiently high accuracy. Our original method is applied to derive astrometric data from photometric observations of the mutual occultations and eclipses of the Saturnian satellites. We process the 26 light curves obtained during the international campaign of photometric observations of the Saturnian satellites in 2009.
    Astronomy and Astrophysics 01/2012; · 5.08 Impact Factor
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    ABSTRACT: The manifold Gaia scientific output rely on precise astrometry accurate to submas standards. This depends on building a fundamental reference frame formed by pointlike, position stable, and allsky homogeneous grid points. In one word, quasars. The Gaia CU3 Initial Quasar Catalogue Working Package was established to beforehand produce one such list, although ultimately the satellite multiband photometry aided by astrometric monitoring has the potential to pick up a clean sample of quasars.
    Memorie della Societa Astronomica Italiana. 01/2012;
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    ABSTRACT: The Galactic Bulge Valinhos Observatory Catalog (GBVOC) contains 11619 stars brighter than V~16 magnitudes, located in the direction of 12 low extinction windows of the Galactic bulge. The catalog provides the J2000.0 positions, proper motions at the mean epoch and their errors. These astrometric parameters were measured exclusively with CCD meridian observations realized at the Abrahao de Moraes Observatory Valinhos (Brazil) with a mean internal precision of 22mas for the positions and 4mas/yr for the proper motions. The catalog also contains the V magnitudes and mean epochs of observations. Moreover, an indicative effective temperature (better than 500K) based on the 2MASS photometry is given. The JHK 2MASS magnitudes and identifier are also provided. In the last column the capital letter T indicates that the star is present in the Tycho 2 catalog. (1 data file).
    VizieR Online Data Catalog. 10/2011;
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    ABSTRACT: Context. The definition, construction and realization of a reference system is one of the oldest and most fundamental tasks of astronomy. Currently, the International Celestial Reference System (ICRS), realized by the International Celestial Reference Frame (ICRF) or ICRF2, is the reference system adopted by the IAU. It is based on the very precise VLBI positions of a few hundred compact extragalactic radio sources. Despite its excellent precision, the ICRF is far from providing a reference system that is available for the entire sky and accessible to all observers. The ICRF has to be densified and extended to other wavelengths, mainly to the optical domain where the astronomical activities are more intense. For this reason, the IAU has recommended and encouraged works in this direction over the years. Many of them were developed to give sometimes good positions and proper motions, but they are very limited in magnitude, while others are extremely dense and deep in magnitude but have low accuracy, mainly for the proper motions. Nevertheless, all these contributions are very important because they are complementary. Aims: We present a homogeneous and precise optical astrometric catalog that extends the ICRF in the direction of 12 low-extinction windows of the Galactic bulge and provides at the same time a useful database for kinematic studies. Methods: The catalog was constructed on a total of 9 observational epochs spread over 15 years of observations with the CCD meridian circle of the Abrahão de Moraes Observatory (Valinhos - Brazil). The Galactic Bulge Valinhos Observatory Catalog (GBVOC) contains only those stars with at least 6 observational epochs and a time base of 10 years or more. We also imposed a minimum of 3 observations per star in each observational epoch and 20 observations in total. Results: The catalog provides positions and proper motions for about 11 600 stars with a mean internal precision of about 22 mas and 4.0 mas/yr, which ensures a high quality and reliable extension of the ICRF in this direction. The GBVOC is extremely dense with more than 3500 stars per square degree. Comparison of the GBVOC with other densification works allows us to estimate the external precision of the GBVOC to be better than 42.0 mas and 5.5 mas/yr in position and proper motion. Based on observations collected with the CCD meridian circle of the Abrahão de Moraes Observatory - Valinhos - Brazil.Full Table 2 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/534/A91
    Astronomy and Astrophysics 01/2011; 534. · 5.08 Impact Factor
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    ABSTRACT: We present a catalogue of 2572 new double stars with common proper motion and angular separation smaller than 2 arcminutes, found in PM2000 proper motion catalogue. To this catalogue we add an annex of 259 of common proper motion doublestars with angular separation between 2 and 5 arcminutes and proper motion larger than 50mas/yr. A by-product of this work was the identification in PM2000 and remeasurement of 926 WDS double stars. (3 data files).
    VizieR Online Data Catalog. 07/2010;
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    ABSTRACT: We derive lists of proper-motions and kinematic membership probabilities for 49 open clusters and possible open clusters in the zone of the Bordeaux PM2000 proper motion catalogue ($+11^{\circ}\le\delta\le+18^{\circ}$). We test different parametrisations of the proper motion and position distribution functions and select the most successful one. In the light of those results, we analyse some objects individually. The segregation between cluster and field member stars, and the assignment of membership probabilities, is accomplished by applying a new and fully automated method based on both parametrisations of the proper motion and position distribution functions, and genetic algorithm optimization heuristics associated with a derivative-based hill climbing algorithm for the likelihood optimization. We present a catalogue comprising kinematic parameters and associated membership probability lists for 49 open clusters and possible open clusters in the Bordeaux PM2000 catalogue region. We note that this is the first determination of proper motions for five open clusters. We confirm the non-existence of two kinematic populations in the region of 15 previously suspected non-existent objects. Comment: 14 pages, 6 figures, 4 tables. Accepted for publication in Astronomy & Astrophysics
    Astronomy and Astrophysics 06/2010; · 5.08 Impact Factor
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    ABSTRACT: The PASTEL catalogue is an update of the [Fe/H] catalogue, published in 1997 and 2001. It is a bibliographical compilation of stellar atmospheric parameters providing (Teff,logg,[Fe/H]) determinations obtained from the analysis of high resolution, high signal-to-noise spectra, carried out with model atmospheres. PASTEL also provides determinations of the one parameter Teff based on various methods. It is aimed in the future to provide also homogenized atmospheric parameters and elemental abundances, radial and rotational velocities. A web interface has been created to query the catalogue on elaborated criteria. PASTEL is also distributed through the CDS database and VizieR. To make it as complete as possible, the main journals have been surveyed, as well as the CDS database, to find relevant publications. The catalogue is regularly updated with new determinations found in the literature. As of Febuary 2010, PASTEL includes 30151 determinations of either Teff or (Teff,logg,[Fe/H]) for 16649 different stars corresponding to 865 bibliographical references. Nearly 6000 stars have a determination of the three parameters (Teff,logg,[Fe/H]) with a high quality spectroscopic metallicity. Comment: 5 pages, accepted for publication in A&A. The PASTEL catalogue can be queried at http://pastel.obs.u-bordeaux1.fr/ or http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=B/pastel
    Astronomy and Astrophysics 04/2010; · 5.08 Impact Factor
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    ABSTRACT: We present lists of proper-motions and kinematic membership probabilities in the region of 49 open clusters or possible open clusters. The stellar proper motions were taken from the Bordeaux PM2000 catalogue. The segregation between cluster and field stars and the assignment of membership probabilities was accomplished by applying a fully automated method based on parametrisations for the probability distribution functions and genetic algorithm optimisation heuristics associated with a derivative-based hill climbing algorithm for the likelihood optimization. (3 data files).
    VizieR Online Data Catalog. 03/2010; 351:69003.
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    ABSTRACT: Context. The present knowledge of common proper motion double stars is rather poor and almost entirely restricted to the Luyten LDS catalogue of 6210 pairs, to 439 pairs of Halbwachs catalogue of common proper motion stars in AGK3, and to Greaves new northern common proper motion pairs (975 pairs). Aims: We present a search for new double stars with common proper motion in the Bordeaux, PM2000, proper motion catalogue (+11degr
    Astronomy and Astrophysics 01/2010; · 5.08 Impact Factor
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    ABSTRACT: PASTEL is a bibliographical catalogue compiling determinations of stellar atmospheric parameters. It provides (Teff, logg, [Fe/H]) determinations obtained from detailed analyses of high resolution, high signal to noise spectra, carried out with the help of model atmospheres. It also provides effective temperatures Teff from various methods. PASTEL is regularly updated. The catalogue supersedes the two previous versions of the [Fe/H] catalogue (Cayrel de Strobel et al., 1997 [Cat. III/200], 2001 [Cat. III/221]). (1 data file).
    VizieR Online Data Catalog. 12/2009; 1:02029.
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    ABSTRACT: Prompted by a high optical state in 2007 September, the Whole Earth Blazar Telescope consortium organized an intensive optical, near-IR (JHK) and radio observing campaign on the intermediate BL Lac object 3C 66A throughout the fall and winter of 2007-2008. In this paper, we present data from 28 observatories in 12 countries, covering the observing season from late 2007 July through 2008 February. The source remained in a high optical state throughout the observing period and exhibited several bright flares on timescales of ~10 days. This included an exceptional outburst around 2007 September 15-20, reaching a peak brightness at R~ 13.4. Our campaign revealed microvariability with flux changes up to |dR/dt|~ 0.02 mag hr–1. Our observations do not reveal evidence for systematic spectral variability in the overall high state covered by our campaign, in agreement with previous results. In particular, we do not find evidence for spectral hysteresis in 3C 66A for which hints were found in an earlier campaign in a somewhat lower flux state. We also did not find any evidence for spectral lags in the discrete correlation functions between different optical bands. We infer a value of the magnetic field in the emission region of B~ 19 e 2/7 B τ–6/7 h D 13/7 1 G, where eB is the magnetic field equipartition fraction, τ h is the shortest observed variability timescale in units of hours, and D 1 is the Doppler factor in units of 10. From the lack of systematic spectral variability, we can derive an upper limit on the Doppler factor, D ≤ 28 τ–1/8 h e 3/16 B . This is in perfect agreement with superluminal motion measurements with the VLBI/VLBA of βapp ≤ 27 and argues against models with very high Lorentz factors of Γ 50, required for a one-zone synchrotron-self-Compton interpretation of some high-frequency-peaked BL Lac objects detected at TeV γ-ray energies.
    The Astrophysical Journal 03/2009; 694(1):174. · 6.73 Impact Factor
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    ABSTRACT: Since September 2005, the Whipple 10m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five Northern Hemisphere blazars that have already been detected at the Whipple Observatory, Markarian 421, H1426+428, Markarian 501, 1ES 1959+650 and 1ES 2344+514, are monitored routinely each night that they are visible. We report on the Markarian 421 observations taken from November 2005 to June 2006 in the gamma-ray, X-ray, optical and radio bands. During this time, Markarian 421 was found to be variable at all wavelengths probed. Both the variability and the correlations among different energy regimes are studied in detail here. A tentative correlation, with large spread, was measured between the X-ray and gamma-ray bands, while no clear correlation was evident among the other energy bands. In addition to this, the well-sampled spectral energy distribution of Markarian 421 (1101+384) is presented for three different activity levels. The observations of the other blazar targets will be reported separately.
    The Astrophysical Journal 01/2009; 695(1). · 6.73 Impact Factor
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    ABSTRACT: Context. In 2003, the Sun and the Earth passed through both the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. Aims. During this period, mutual eclipses and occultations were observed and we present the data collected.Methods. Light curves of mutual eclipses and occultations were recorded by the observers of the international campaign PHEMU03 organized by the Institut de mécanique céleste, Paris, France. Results. We completed 377 observations of 118 mutual events from 42 sites and the corresponding data are presented in this paper. For each observation, information about the telescope, receptor, site, and observational conditions are provided.Conclusions. This paper gathers all data and indicates a first estimate of its precision. This catalogue of these rare events should constitute an improved basis for accurate astrometric data useful in the development of dynamical models.
    http://dx.doi.org/10.1051/0004-6361:200810420. 01/2009;
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    G. Bourda, P. Charlot, J. -F. Le Campion
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    ABSTRACT: The ICRF, currently based on the position of 717 extragalactic radio sources observed by VLBI, is the fundamental celestial reference frame adopted by the IAU in 1997. Within the next 10 years, the European space astrometry mission Gaia, to be launched by 2011, will permit determination of the extragalactic reference frame directly in the visible for the first time. Aligning these two frames with the highest accuracy will therefore be very important in the future for ensuring consistency between the measured radio and optical positions. This paper is aimed at evaluating the current astrometric suitability of the individual ICRF radio sources which are considered appropriate for the alignment with the future Gaia frame. To this purpose, we cross-identified the ICRF and the optical catalog V\'eron-Cetty and V\'eron (2006), to identify the optically-bright ICRF sources that will be positioned with the highest accuracy with Gaia. Then we investigated the astrometric suitability of these sources by examining their VLBI brightness distribution. We identified 243 candidate ICRF sources for the alignment with the Gaia frame (with an optical counterpart brighter than the apparent magnitude 18), but only 70 of these (10% of the ICRF sources) are found to have the necessary high astrometric quality (i.e. a brightness distribution that is compact enough) for this link. Additionally, it was found that the QSOs that will have the most accurate positions in the Gaia frame tend to have less-accurate VLBI positions, most probably because of their physical structures. Altogether, this indicates that identifying other high-quality VLBI radio sources suitable for the alignment with the future Gaia frame is mandatory.
    Astronomy and Astrophysics 10/2008; · 5.08 Impact Factor
  • Minor Planet Circulars. 08/2008;

Publication Stats

227 Citations
162.51 Total Impact Points

Institutions

  • 2014
    • University of Bordeaux
      Burdeos, Aquitaine, France
  • 2006–2008
    • French National Centre for Scientific Research
      • Observatoire aquitain des sciences de l'Univers
      Lutetia Parisorum, Île-de-France, France
  • 1991
    • Bulgarian Academy of Sciences
      Ulpia Serdica, Sofia-Capital, Bulgaria