Very Large Telescope/X-shooter Spectroscopy of the Candidate Black Hole X-Ray Binary MAXI J1659-152 in Outburst
Abstract
We present the optical to near-infrared spectrum of MAXI J1659-152 during the onset of its 2010 X-ray outburst. The spectrum was obtained with X-shooter on the ESO Very Large Telescope early in the outburst simultaneous with high-quality observations at both shorter and longer wavelengths. At the time of the observations, the source was in the low-hard state. The X-shooter spectrum includes many broad (~2000 km s-1), double-peaked emission profiles of H, He I, and He II, characteristic signatures of a low-mass X-ray binary during outburst. We detect no spectral signatures of the low-mass companion star. The strength of the diffuse interstellar bands results in a lower limit to the total interstellar extinction of AV ~= 0.4 mag. Using the neutral hydrogen column density obtained from the X-ray spectrum we estimate AV ~= 1 mag. The radial velocity structure of the interstellar Na I D and Ca II H&K lines results in a lower limit to the distance of ~4 ± 1 kpc, consistent with previous estimates. With this distance and AV , the dereddened spectral energy distribution represents a flat disk spectrum. The two 10 minute X-shooter spectra show significant variability in the red wing of the emission-line profiles, indicating a global change in the density structure of the disk, though on a timescale much shorter than the typical viscous timescale of the disk.
Based on ESO-VLT/X-shooter observations obtained using the X-shooter guaranteed time GRB program (086.A-0073).- Publication:
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The Astrophysical Journal
- Pub Date:
- February 2012
- DOI:
- 10.1088/2041-8205/746/2/L23
- arXiv:
- arXiv:1201.4883
- Bibcode:
- 2012ApJ...746L..23K
- Keywords:
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- accretion;
- accretion disks;
- binaries: close;
- black hole physics;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted for publication in ApJ Letters