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arXiv · 0705.2693

The Black Hole Binary Nova Scorpii 1994 (GRO J1655-40): An improved chemical analysis

J. I. Gonzalez Hernandez·R. Rebolo·G. Israelian
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Abstract

The chemical analysis of secondary stars of low mass X-ray binaries provides an opportunity to study the formation processes of compact objects, either black holes or neutron stars. Following the discovery of overabundances of $\alpha$-elements in the HIRES/Keck spectrum of the secondary star of Nova Scorpii 1994 (Israelian et al. 1999), we obtained UVES/VLT high-resolution spectroscopy with the aim of performing a detailed abundance analysis of this secondary star. Using a $\chi2$-minimization procedure and a grid of synthetic spectra, we derive the stellar parameters and atmospheric abundances of O, Mg, Al, Ca, Ti, Fe and Ni, using a new UVES spectrum and the HIRES spectrum.The abundances of Al, Ca, Ti, Fe and Ni seem to be consistent with solar values, whereas Na, and especially O, Mg, Si and S are significantly enhanced in comparison with Galactic trends of these elements. A comparison with spherically and non-spherically symmetric supernova explosion models may provide stringent constraints to the model parameters as mass-cut and the explosion energy, in particular from the relative abundances of Si, S, Ca, Ti, Fe and Ni. Most probably the black hole in this system formed in a hypernova explosion of a 30--35 \Msun progenitor star with a mass-cut in the range 2--3.5 \Msun. However, these models produce abundances of Al and Na almost ten times higher than the observed values.

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J. I. Gonzalez Hernandez, R. Rebolo, G. Israelian. 2007-05-18. The Black Hole Binary Nova Scorpii 1994 (GRO J1655-40): An improved chemical analysis. https://doi.org/10.1051/0004-6361:20077141

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