Bibcode
González-Hernández, J. I.; Casares, J.; Rebolo, R.; Israelian, G.; Filippenko, Alexei V.; Chornock, Ryan
Bibliographical reference
The Astrophysical Journal, Volume 738, Issue 1, article id. 95 (2011).
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9
2011
Journal
Citations
34
Refereed citations
32
Description
We present a chemical abundance analysis of the secondary star in the
black hole binary V404 Cygni, using Keck I/High Resolution Spectrometer.
We adopt a χ2-minimization procedure to derive the
stellar parameters, taking into account any possible veiling from the
accretion disk. With these parameters we determine the atmospheric
abundances of O, Na, Mg, Al, Si, Ca, Ti, Fe, and Ni. The abundances of
Al, Si, and Ti appear to be slightly enhanced when comparing with
average values in thin-disk solar-type stars. The O abundance, derived
from optical lines, is particularly enhanced in the atmosphere of the
secondary star in V404 Cygni. This, together with the peculiar velocity
of this system as compared with the Galactic velocity dispersion of
thin-disk stars, suggests that the black hole formed in a supernova (SN)
or hypernova (HN) explosion. We explore different SN/HN models having
various geometries to study possible contamination of nucleosynthetic
products in the chemical abundance pattern of the secondary star. We
find reasonable agreement between the observed abundances and the model
predictions. However, the O abundance seems to be too high regardless of
the choice of explosion energy or mass cut, when trying to fit other
element abundances. Moreover, Mg appears to be underabundant for all
explosion models, which produces Mg abundances roughly two times higher
than the observed value.
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