Optical Analysis and Modeling of HD96670, a new Black Hole X-ray Binary Candidate

Sebastian Gomez; Jonathan E. Grindlay

doi:10.3847/1538-4357/abf24c

paper

Optical Analysis and Modeling of HD96670, a new Black Hole X-ray Binary Candidate

arXiv:2211.04518 · doi:10.3847/1538-4357/abf24c

Abstract

We report on optical observations and modeling of HD96670, a single-line spectroscopic binary in the Carina OB2 association. We collected 10 epochs of optical spectroscopy, and optical photometry on 17 non-consecutive nights on the source. We construct a radial velocity curve from the spectra, and update the orbital period of the binary to be $P = 5.28388 \pm 0.00046$ days. The spectra show oxygen and helium absorption, consistent with an O-type primary. We see no evidence for spectral lines from the secondary star in the binary. We model the optical light curve and radial velocity curve simultaneously using the Wilson-Devinney code and find a best fit mass of $M_{1} = 22. 7_{- 3.6}^{+ 5.2} M_{⊙}$ for the primary, and $M_{2} = 6. 2_{- 0.7}^{+ 0.9} M_{⊙}$ for the secondary. An object of this mass is consistent with either a B-type star, or a black hole. Given that we see no absorption lines from the secondary, in combination with an observed hard power-law X-ray spectrum with $Γ = 2.6$ detected past 10 keV, maybe produced by wind accretion onto the secondary, we conclude that the secondary is most likely a black hole. We see asymmetrical helium lines with a shape consistent with the presence of a third star. If the secondary is indeed a black hole, this system would add to the small sample of only four possible black hole high mass X-ray binaries in the galaxy.

14 pages, 8 figured, Accepted to ApJ May 2021

Optical Analysis and Modeling of HD96670, a new Black Hole X-ray Binary Candidate

Abstract

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