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Measuring the Motion of the Black Hole in GRO J16550-40

Roberto Soria·Dayal T. Wickramasinghe·Richard W. Hunstead·Kinwah Wu
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Abstract

We report optical spectroscopic observations of the Low Mass X-ray Binary GRO J1655-40 during outbursts in August-September 1994 and in June 1996. The spectra show emission and absorption lines from the accretion disk surrounding the X-ray source, which have enabled us to measure the motion of the black-hole candidate in this system. It is the first time among black-hole candidates that an emission-line radial velocity curve is seen in phase with the expected motion of the primary. The projected radial velocity semi-amplitude determined for the primary [K(X) = 76.2 +/- 7.5 km/s], combined with estimates of the projected radial velocity semi-amplitude of the companion star from previous observations [K(C) = 228.2 +/- 3.0 km/s], yields a 95% confidence limit, derived purely from kinematics, of M(X) > 5.1 M(sun) for the mass of the compact object in GRO J1655-40, confirming its black hole nature.

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Roberto Soria, Dayal T. Wickramasinghe, Richard W. Hunstead, Kinwah Wu. 1998-01-13. Measuring the Motion of the Black Hole in GRO J16550-40. https://doi.org/10.1086/311225

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