VLT/X-shooter Spectroscopy Of The Candidate Black Hole X-ray Binary MAXI J1659-152

MAXI J1659-152 which was discovered using Swift as a Gamma-ray-burst, was later on confirmed as a candidate Galactic black-hole X-ray binary. The source was intensively followed up by Swift and RXTE during its X-ray outburst and was revealed as a shortest period (2.4 hrs) black-hole X-ray binary. Following the X-ray outburst, we triggered the ESO-Very Large Telescope and obtained the optical and the near-infrared spectra of the source with the X-shooter spectrograph. The source was in low-hard state during our observations. The spectrum includes many broad ( 2000 km/s) double peaked hydrogen and helium emission features. Two important results of our observations include the linear trend seen in the peak separation of the H lines with respect to the energy of their upper transitional levels and the considerable variability seen in the red-wing of the spectral line profiles between the two subsequent exposures. From our observations we estimated the distance to the source as 4 +/- 1 kpc. We would like to present these results in the context of the accretion flows in the compact black hole X-ray binaries.