Volume 414, Number 2, February I 2004
|Page(s)||L13 - L16|
|Published online||19 January 2004|
Letter to the Editor
The rotational broadening and the mass of the donor star of GRS 1915+105
Institute of Space Applications and Remote Sensing, National Observatory of Athens, PO Box 20048, Athens 118 10, Greece
2 Max Planck Institute for Extraterrestrial Physics, Giessenbachstr., PF 1312, 85741 Garching, Germany e-mail: email@example.com
Corresponding author: E. T. Harlaftis, firstname.lastname@example.org
Accepted: 11 December 2003
The binary parameters of the microquasar GRS 1915+105 have been determined by the detection of Doppler-shifted 12CO and 13CO lines in its K-band spectrum (Greiner et al. [CITE]). Here, we present further analysis of the same K-band VLT spectra and we derive a rotational broadening of the donor star of km s-1 from the 12CO/13CO lines. Assuming that the K-type star is tidally locked to the black hole and is filling its Roche-lobe surface, then the implied mass ratio is . This result, combined with () = (33.5 d, 140 km s-1, 66°) gives a more refined mass estimate for the black hole, , than previously estimated, using an inclination of (Fender et al. [CITE]) as derived from the orientation of the radio jets and a more accurate distance. The mass for the early K-type giant star is , consistent with a more evolved stripped-giant donor star in GRS 1915+105 than, for example, the donor star of the prototype black-hole X-ray transient, V404 Cyg which has the longest binary period after GRS 1915+105.
Key words: stars: infrared / stars: X-ray / black hole physics / stars: binaries / stars: individual: GRS 1915+105
© ESO, 2004
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