Doppler tomography of the black hole binary A0620-00 and the origin of chromospheric emission in quiescent X-ray binaries
Abstract
Context. Doppler tomography of emission line profiles in low-mass X-ray binaries allows us to disentangle the different emission sites and study the structure and variability of accretion disks.
Aims: We present UVES high-resolution spectroscopic observations of the black hole binary A0620-00 at quiescence.
Methods: These spectroscopic data constrain the orbital parameters Porb = 0.32301405(1) d and K2 = 437.1 ± 2.0 km s-1. These values, together with the mass ratio q = M2/M1 = 0.062 ± 0.010, imply a minimum mass for the compact object of M1 sin3 i = 3.15 ± 0.10 M_⊙, consistent with previous works.
Results: The Hα emission from the accretion disk is much weaker than in previous studies, possibly because of a decrease in disk activity. Doppler imaging of the Hα line shows for the first time a narrow component coming from the secondary star, with an observed equivalent width of 1.4 ± 0.3 Å, perhaps associated to chromospheric activity. Subtracting a K-type template star and correcting for the veiling of the accretion disk yields an equivalent width of 2.8 ± 0.3 Å. A bright hot spot is also detected at the position where the gas stream trajectory intercepts the accretion disk.
Conclusions: The Hα flux associated to the secondary star is too large to be powered by X-ray irradiation. It is comparable to those observed in RS CVn binaries with similar orbital periods and is probably triggered by the rapid stellar rotation.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2010
- DOI:
- 10.1051/0004-6361/201014088
- arXiv:
- arXiv:1004.0435
- Bibcode:
- 2010A&A...516A..58G
- Keywords:
-
- black hole physics;
- accretion;
- accretion disks;
- binaries: close;
- stars: individual: V616 Mon;
- X-rays: binaries;
- stars: activity;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in Astronomy &