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.