E. Oblak | Université de Franche-Comté (original) (raw)

Papers by E. Oblak

Astronomy and Astrophysics, 2007

A procedure for the automatic classification of eclipsing binaries is presented. The procedure is... more A procedure for the automatic classification of eclipsing binaries is presented. The procedure is based on the data from 1029 classified systems and allows for the classification of a given system based on a set of observational parameters, even if the set is incomplete. The procedure is applied to six large surveys of eclipsing variables. About 5300 systems were classified for the first time and can be used for the determination of the astrophysical parameters of their components.

Astronomy and Astrophysics, 2006

A new catalogue of 6330 eclipsing variable stars is presented. The catalogue was developed from t... more A new catalogue of 6330 eclipsing variable stars is presented. The catalogue was developed from the General Catalogue of Variable Stars (GCVS) and its textual remarks by including recently published information about classification of 843 systems and making corresponding corrections of GCVS data. The catalogue 1 represents the largest list of eclipsing binaries classified from observations.

Astronomy and Astrophysics, 2001

We present new astrometric and photometric data for 253 visual double stars of the "intermediate"... more We present new astrometric and photometric data for 253 visual double stars of the "intermediate" class, i.e. with angular separations in the range 1 to 15 arcsec. The multi-colour observations were obtained in 1992-94 as part of the ESO Key Programme "Visual Double Stars" performed at La Silla Observatory (Chile). Differential magnitudes and colours have been secured in a systematic way while component magnitudes and colour indices have been determined in the V and I passbands of the Cousins standard system in good photometric conditions only. Internal and mean external errors are smaller than respectively 0.01 mag and a few hundreths of a magnitude (typically less than 0.03 mag). Relative positions are obtained as a by-product with internal errors of the order of 0.006 in angular separation (corresponding to pixel width ×0.02) and 0.07 • in position angle. Final accuracies are thoroughly discussed: we illustrate the overall excellent quality of the data and estimate the quality degradation for angular separations barely larger than the width of the seeing disk.

Astronomy and Astrophysics, 2001

From speckle observations made with the PISCO speckle camera at the Pic du Midi Observatory, we p... more From speckle observations made with the PISCO speckle camera at the Pic du Midi Observatory, we present high angular resolution astrometric data for 43 binary stars already observed by the Hipparcos satellite. This sample consists of mainly new Hipparcos eclipsing binaries with a visual companion closer than one arcsecond, chosen with the aim to study the dynamical implications of a third component on the observational parameters of the eclipsing system. In addition, we also included a selection of close visual binaries with few speckle data in order to analyse possible systematic departures between the speckle and the non-speckle orbits. The reduction method and the results are presented in detail. For the close visual binaries we confront our observations with the ephemerides based on the best known orbits. For the wide visual binaries the confrontation is made directly with the Hipparcos data. Our observations are consistent both with previous speckle data and with most of the Hipparcos measurements.

Astronomy and Astrophysics, 2003

Serious discrepancies have recently been observed between predictions of stellar evolution models... more Serious discrepancies have recently been observed between predictions of stellar evolution models in the 0.7-1.1 M⊙ mass range and accurately measured properties of binary stars with components in this mass range. We study one of these objects, the eclipsing binary UV Piscium, which is particularly interesting because Popper (1997) derived age estimates for each component which differed by more than a factor of two. In an attempt to solve this significant discrepancy (a difference in age of 11 Gyr), we compute a large grid of stellar evolution models with the CESAM code for each component. By fixing the masses to their accurately determined values (relative error smaller than 1% for both stars), we consider a wide range of possible metallicities Z (0.01 to 0.05), and Helium content Y (0.25 to 0.34) uncorrelated to Z. In addition, the mixing length parameter αMLT is left as another free parameter. We obtain a best fit in the T eff -radius diagram for a common chemical composition (Z, Y )=(0.012, 0.31), but a different MLT parameter αMLT,A= 0.95±0.12(statistical)+0.30(systematic) and αMLT,B= 0.65±0.07(stat)+0.10(syst). The apparent age discrepancy found by Popper (1997) disappears with this solution, the components being coeval to within 1%. This suggests that fixing αMLT to its solar value (∼1.6), a common hypothesis assumed in most stellar evolutionary models, may not be correct. Secondly, since αMLT is smaller for the less massive component, this suggests that the αMLT parameter may decrease with stellar mass, showing yet another shortcoming of the mixing length theory to explain stellar convection. This trend needs further confirmation with other binary stars with accurate data.

Astronomy and Astrophysics Supplement Series, 1999

Radial velocities have been determined for a sample of 2930 B2-F5 stars, 95% observed by the Hipp... more Radial velocities have been determined for a sample of 2930 B2-F5 stars, 95% observed by the Hipparcos satellite in the north hemisphere and 80% without reliable radial velocity up to now. Observations were obtained at the Observatoire de Haute Provence with a dispersion of 80 Ä,mm(-1) with the aim of studying stellar and galactic dynamics. Radial velocities have been measured

The Astronomical Journal, 2010

ABSTRACT We present results of an analysis of all available data of the double-lined spectroscopi... more ABSTRACT We present results of an analysis of all available data of the double-lined spectroscopic and eclipsing binary HP Draconis. The analyses make use of unpublished radial velocity (RV) and extensive photoelectric photometry data as well as published Hipparcos photometric observations and RV data from Asiago Observatory. The system is eccentric and the current analyses suggest apsidal motion to be present only weakly, but a significant amount of third light is found in all three passbands, B, V, and hip. Relatively high precision has been achieved for the mass and radius among the absolute parameters with fractional error of 0.95% or better: M 1,2 = 1.133 ± 0.005, 1.094 ± 0.007 M ☉; R 1,2 = 1.371 ± 0.012, 1.052 ± 0.010 R ☉. Other derived parameters are P = 10.76152 ± 0.00019 days, a = 26.79 ± 0.04 R ☉, e = 0.0367 ± 0.0009, ω = 0.693 ± 0.037, q = 0.966 ± 004, and ΔT = 105 ± 5 K. We derive a distance to the system of 77 ± 3 pc. Comparison with Padova theoretical models for different chemical compositions suggests that the components may be of solar age and roughly solar composition, with the primary component less than half as dense as the secondary component and slightly evolved off the zero-age main sequence.

Astronomy and Astrophysics, 2007

A procedure for the automatic classification of eclipsing binaries is presented. The procedure is... more A procedure for the automatic classification of eclipsing binaries is presented. The procedure is based on the data from 1029 classified systems and allows for the classification of a given system based on a set of observational parameters, even if the set is incomplete. The procedure is applied to six large surveys of eclipsing variables. About 5300 systems were classified for the first time and can be used for the determination of the astrophysical parameters of their components.

Astronomy and Astrophysics, 2006

A new catalogue of 6330 eclipsing variable stars is presented. The catalogue was developed from t... more A new catalogue of 6330 eclipsing variable stars is presented. The catalogue was developed from the General Catalogue of Variable Stars (GCVS) and its textual remarks by including recently published information about classification of 843 systems and making corresponding corrections of GCVS data. The catalogue 1 represents the largest list of eclipsing binaries classified from observations.

Astronomy and Astrophysics, 2001

We present new astrometric and photometric data for 253 visual double stars of the "intermediate"... more We present new astrometric and photometric data for 253 visual double stars of the "intermediate" class, i.e. with angular separations in the range 1 to 15 arcsec. The multi-colour observations were obtained in 1992-94 as part of the ESO Key Programme "Visual Double Stars" performed at La Silla Observatory (Chile). Differential magnitudes and colours have been secured in a systematic way while component magnitudes and colour indices have been determined in the V and I passbands of the Cousins standard system in good photometric conditions only. Internal and mean external errors are smaller than respectively 0.01 mag and a few hundreths of a magnitude (typically less than 0.03 mag). Relative positions are obtained as a by-product with internal errors of the order of 0.006 in angular separation (corresponding to pixel width ×0.02) and 0.07 • in position angle. Final accuracies are thoroughly discussed: we illustrate the overall excellent quality of the data and estimate the quality degradation for angular separations barely larger than the width of the seeing disk.

Astronomy and Astrophysics, 2001

From speckle observations made with the PISCO speckle camera at the Pic du Midi Observatory, we p... more From speckle observations made with the PISCO speckle camera at the Pic du Midi Observatory, we present high angular resolution astrometric data for 43 binary stars already observed by the Hipparcos satellite. This sample consists of mainly new Hipparcos eclipsing binaries with a visual companion closer than one arcsecond, chosen with the aim to study the dynamical implications of a third component on the observational parameters of the eclipsing system. In addition, we also included a selection of close visual binaries with few speckle data in order to analyse possible systematic departures between the speckle and the non-speckle orbits. The reduction method and the results are presented in detail. For the close visual binaries we confront our observations with the ephemerides based on the best known orbits. For the wide visual binaries the confrontation is made directly with the Hipparcos data. Our observations are consistent both with previous speckle data and with most of the Hipparcos measurements.

Astronomy and Astrophysics, 2003

Serious discrepancies have recently been observed between predictions of stellar evolution models... more Serious discrepancies have recently been observed between predictions of stellar evolution models in the 0.7-1.1 M⊙ mass range and accurately measured properties of binary stars with components in this mass range. We study one of these objects, the eclipsing binary UV Piscium, which is particularly interesting because Popper (1997) derived age estimates for each component which differed by more than a factor of two. In an attempt to solve this significant discrepancy (a difference in age of 11 Gyr), we compute a large grid of stellar evolution models with the CESAM code for each component. By fixing the masses to their accurately determined values (relative error smaller than 1% for both stars), we consider a wide range of possible metallicities Z (0.01 to 0.05), and Helium content Y (0.25 to 0.34) uncorrelated to Z. In addition, the mixing length parameter αMLT is left as another free parameter. We obtain a best fit in the T eff -radius diagram for a common chemical composition (Z, Y )=(0.012, 0.31), but a different MLT parameter αMLT,A= 0.95±0.12(statistical)+0.30(systematic) and αMLT,B= 0.65±0.07(stat)+0.10(syst). The apparent age discrepancy found by Popper (1997) disappears with this solution, the components being coeval to within 1%. This suggests that fixing αMLT to its solar value (∼1.6), a common hypothesis assumed in most stellar evolutionary models, may not be correct. Secondly, since αMLT is smaller for the less massive component, this suggests that the αMLT parameter may decrease with stellar mass, showing yet another shortcoming of the mixing length theory to explain stellar convection. This trend needs further confirmation with other binary stars with accurate data.

Astronomy and Astrophysics Supplement Series, 1999

Radial velocities have been determined for a sample of 2930 B2-F5 stars, 95% observed by the Hipp... more Radial velocities have been determined for a sample of 2930 B2-F5 stars, 95% observed by the Hipparcos satellite in the north hemisphere and 80% without reliable radial velocity up to now. Observations were obtained at the Observatoire de Haute Provence with a dispersion of 80 Ä,mm(-1) with the aim of studying stellar and galactic dynamics. Radial velocities have been measured

The Astronomical Journal, 2010

ABSTRACT We present results of an analysis of all available data of the double-lined spectroscopi... more ABSTRACT We present results of an analysis of all available data of the double-lined spectroscopic and eclipsing binary HP Draconis. The analyses make use of unpublished radial velocity (RV) and extensive photoelectric photometry data as well as published Hipparcos photometric observations and RV data from Asiago Observatory. The system is eccentric and the current analyses suggest apsidal motion to be present only weakly, but a significant amount of third light is found in all three passbands, B, V, and hip. Relatively high precision has been achieved for the mass and radius among the absolute parameters with fractional error of 0.95% or better: M 1,2 = 1.133 ± 0.005, 1.094 ± 0.007 M ☉; R 1,2 = 1.371 ± 0.012, 1.052 ± 0.010 R ☉. Other derived parameters are P = 10.76152 ± 0.00019 days, a = 26.79 ± 0.04 R ☉, e = 0.0367 ± 0.0009, ω = 0.693 ± 0.037, q = 0.966 ± 004, and ΔT = 105 ± 5 K. We derive a distance to the system of 77 ± 3 pc. Comparison with Padova theoretical models for different chemical compositions suggests that the components may be of solar age and roughly solar composition, with the primary component less than half as dense as the secondary component and slightly evolved off the zero-age main sequence.