Spectroscopic evidence for a low-mass black hole in SWIFT J1753.5−0127

• DOI: 10.1093/mnras/stu1924
• Publication Date: 2014-10-21T00:27:43Z
• Authors: Vitaly V. Neustroev; Alexandra Veledina; Juri Poutanen; Sergey V. Zharikov; Sergey S. Tsygankov; George Sjoberg; Jari J. E. Kajava
• Keywords: Swift; Orbital period; Black hole (networking); Radial velocity; Be star; Orbital inclination

The black hole (BH) candidate SWIFT J1753.5-0127 has remained active since the onset of its 2005 outburst. Emission lines in optical spectrum were observed at very beginning outburst, but then been featureless making a precise BH mass estimation impossible. Here we present results from our and UV observations taken 2012-2013. Our new show extremely broad, double-peaked emission spectra. data also narrow absorption features with nearly synchronous significant Doppler motions. A radial velocity study these which associate secondary star, yields semi-amplitude K_2=382 km/s. time-series analysis spectral photometric revealed possible orbital periodicity 2.85 h, significantly shorter than reported 3.2 h periodic signal by Zurita et al. variability properties argue against low inclination angle several observational arguments favour interpretation. However, measured donor star short period imply that one lowest function for low-mass X-ray binary. We compact object excess 5 Msun is highly improbable. Thus, binary shortest hosts probably smallest stellar-mass found to date.