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Near Infrared Observations of Galactic Black Hole Candidates

S. Chaty·I. F. Mirabel·P. Goldoni·S. Mereghetti·P. -A. Duc·J. Marti·R. P. Mignani
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Abstract

We report on several European Southern Observatory (ESO) near-infrared (NIR) observational campaigns aimed at understanding the nature of galactic black hole candidates. Our results, including NIR photometry of the sources GRO J1655-40, GRS 1739-278, GRS 1716-249, GRS 1121-68 and GX 339-4, show that all the sources but GRO J1655-40 are consistent with low-mass stars as the companion star of the binary system. By locating the counterparts on a colour-magnitude diagram (CMD), we better constrain the spectral type of the companion star of three of the systems considered here, and confirm a fourth one. The spectral types are respectively: M0-5 V for GRS 1716-249, F8-G2 III for GX 339-4 and later than F5 V for GRS 1739-278. We confirm the already known spectral type of the companion in GRS 1121-68 (K0-5 V). The location of GRO J1655-40 on the CMD is consistent with the sub-giant luminosity class and with this source crossing the Hertzsprung gap. However, a non-stellar emission seems to contribute to the NIR flux of this source.

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S. Chaty, I. F. Mirabel, P. Goldoni, S. Mereghetti, P. -A. Duc, J. Marti, R. P. Mignani. 2001-12-13. Near Infrared Observations of Galactic Black Hole Candidates. https://doi.org/10.1046/j.1365-8711.2002.05267.x

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