SCYON Abstract

Received on May 15 2001

Eclipsing binaries with candidate CP stars II. Parameters of the system V392 Carinae

AuthorsY. Debernardi, P. North
AffiliationInstitut d'Astronomie de l'Université de Lausanne, CH- 1 290 Chavannes-des-Bois, Switzerland
Accepted byAstronomy & Astrophysics
Links NGC 2516


We present a detailed study of an eclipsing binary which had been classified Ap SrCrEu (Hartoog 1976) before being known as a binary. Radial velocities measured at the times of both quadratures allow us to obtain precise masses for both components, while the light curve yields the radii. The following ephemeris and fundamental parameters of the system were obtained:
HJD = (2447999.7656 ± 0.0041) + (3.174990 ± 0.000001) E,
e = 0.00,
i = 82.0 ± 0.1°,
M1 = 1.94 ± 0.02 Msun,
M2 = 1.88 ± 0.02 Msun,
R1 = 1.73 ± 0.03 Rsun,
R2 = 1.50 ± 0.03 Rsun,
v sin i1 = 27.6 ± 3.5 km/s,
v sin i2 = 23.6 ± 3.6 km/s.
The projected rotational velocities were determined by fitting a synthetic spectrum convolved with a rotational profile to the observed spectrum. A comparison of the spectra of V392 Car and of the normal A star Cox 98, which has the same colour indices, shows that Sr is not overabundant and the metallicity of V392 Car is the same as that of the other cluster members. Therefore, V392 Car is a normal A2 star rather than an Ap star. The position of V392 Car in the HR diagram is entirely consistent with membership of the cluster NGC 2516. An independent estimate of the distance to this cluster was done using the parameters of the eclipsing system, and found to be in agreement with the Hipparcos one. A comparison of the parameters obtained from observations with predictions of internal structure models leads to a metallicity estimate [M/H]=0 ± 0.10 dex for NGC 2516. This estimate is completely independent of any spectroscopic or photometric method (except for the Teff determination) but relies on stellar structure models.