Very Large Telescope/X-shooter Spectroscopy of the Candidate Black Hole X-Ray Binary MAXI J1659-152 in Outburst

Kaur, Ramanpreet; Kaper, Lex; Ellerbroek, Lucas E.; Russell, D. M.; Altamirano, Diego; Wijnands, Rudy; Yang, Yi-Jung; D'Avanzo, Paolo; de Ugarte Postigo, Antonio; Flores, Hector; Fynbo, Johan P. U.; Goldoni, Paolo; Thöne, Christina C.; van der Horst, Alexander; van der Klis, Michiel; Kouveliotou, Chryssa; Wiersema, Klaas; Kuulkers, Erik
Bibliographical reference

The Astrophysical Journal Letters, Volume 746, Issue 2, article id. L23 (2012).

Advertised on:
2
2012
Number of authors
18
IAC number of authors
0
Citations
19
Refereed citations
19
Description
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).