arXiv subjects

C. Soubiran

Publications and source records attributed to C. Soubiran.

130 records · Page 8Linked to original sources

arXiv2000

Fundamental properties of the open cluster NGC 2355

NGC 2355 is an old open cluster in the outer part of the galactic disk (l=203 deg, b=+11 deg) which has been little studied until now. This paper presents the first astrometric and spectroscopic investigation of this cluster. We have measured precise absolute proper motions from old Carte du Ciel plates, POSS-I plates and recent CCD observations obtained with the Bordeaux meridian circle. The proper motion data reveal 38 highly probable cluster members down to B=15 mag within 7' of the cluster center. We have also obtained ELODIE high resolution spectra for 24 stars. Seventeen of them are confirmed to be members of the cluster on the basis of radial velocity. Eight of them are fast rotating turnoff stars for which the projected rotational velocity has been determined. The spectroscopic observations have also provided estimates of the physical parameters Teff, log(g), [Fe/H], Mv of the 24 target stars. Two stragglers have been identified in the cluster. Combining our astrometric and spectroscopic results with previous UBV photometry and recent JHKs photometry from the 2MASS survey we have derived the fundamental properties of the cluster : metallicity, age, distance, size, spatial velocity and orbit.

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arXiv1998

On-line determination of stellar atmospheric parameters Teff, log g, [Fe/H] from ELODIE echelle spectra. I - The method

We present a method estimating the atmospheric parameters Teff, log g, [Fe/H] for stars observed, even at low signal to noise ratio, with the echelle spectrograph ELODIE on the 193cm telescope at Observatoire de Haute-Provence. The method relies on the least-square comparison of the spectrum of a target star to a library of 211 spectra of reference stars for which the atmospheric parameters are well known and which were observed with the same instrument. In order to obtain a meaningful comparison between target and reference spectra, all features which are not intrinsic to the objects must be removed. This treatment involves the correction of the blaze efficiency for each order, cosmic rays hits and telluric line removal, convolution of the spectra to a common spectral resolution, wavelength scale and flux level adjustment. The library available at the present time covers the effective temperature range [4000K, 6300K], the metallicity range [-2.9, +0.35] and the gravities of both unevolved and evolved stars existing at these temperatures and metallicities. Tests performed with the actual library allow us to estimate the internal accuracy to be 86 K, 0.28 dex and 0.16 dex for Teff, log g, [Fe/H] for a target star with S/N = 100 and 102 K, 0.29 dex and 0.17 dex at S/N = 10. This accuracy will improve in the future as the number of reference stars in the library will increase. The software (named TGMET) has been installed at Observatoire de Haute-Provence for the on-line analysis of the high-resolution spectra of ELODIE, which was originally conceived for accurate radial velocity measurements.

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arXiv1998

On-line determination of stellar atmospheric parameters Teff, log g, [Fe/H] from ELODIE echelle spectra. II - The library of F5 to K7 stars

A library of 211 echelle spectra taken with ELODIE at the Observatoire de Haute-Provence is presented. It provides a set of spectroscopic standards covering the full range of gravities and metallicities in the effective temperature interval [4000 K, 6300 K]. The spectra are straightened, wavelength calibrated, cleaned of cosmic ray hits, bad pixels and telluric lines. They cover the spectral range [440 nm, 680 nm] with an instrumental resolution of 42000. For each star, basic data were compiled from the Hipparcos catalogue and the Hipparcos Input Catalogue. Radial velocities with a precision better than 100 m/s are given. Atmospheric parameters (Teff, log g, [Fe/H]) from the literature are discussed. Because of scattered determinations in the bibliography, even for the most well-known stars, these parameters were adjusted by an iterative process which takes account of common or different spectral features between the standards, using our homogeneous set of spectra. Revised values of (Teff, log g, [Fe/H]) are proposed. They are still consistent with the literature, and also lead to the self-consistency of the library, in the sense that similar spectra have similar atmospheric parameters. This adjustment was performed by using step by step a method based on the least square comparison of carefully prepared spectra, which was originally developed for the on-line estimation of the atmospheric parameters of faint field stars (companion paper in the main journal). The spectra and corresponding data will only be available in electronic form at the CDS (ftp cdsarc.u-strasbg.fr or http://cdsweb.u-strasbg.fr/Abstract.html).

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arXiv1997

A catalogue of [Fe/H] determinations : 1996 edition

The Catalogue of [Fe/H] determinations has been updated and now includes 5946 determinations for 3247 stars (with 751 stars in 84 associations, clusters or galaxies). The 700 bibliographical references are complete up to December 1995 and refer only to [Fe/H] determinations obtained from high-resolution spectroscopic observations. The Catalogue also gives the spectral type, the object type, the visual magnitude and colour, as well as determinations of the effective temperature and gravity for each star, when available. In this paper, we comment on the Catalogue, the parameters listed in it, its stellar content,and the precautions that should be observed when using it. The full Catalogue is only available in electronic form at the CDS or upon request (soubiran@observ.u-bordeaux.fr).

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