The black hole ( BH ) candidate SWIFT J1753.5–0127 has remained active since the onset of its 2005 outburst . Emission lines in the optical spectrum were observed at the very beginning of the outburst , but since then the spectrum has been featureless making a precise BH mass estimation impossible . Here we present results from our optical and ultraviolet ( UV ) observations of SWIFT J1753.5–0127 taken in 2012–2013 . Our new observations show extremely broad , double-peaked emission lines in the optical and UV spectra . The optical data also show narrow absorption and emission features with nearly synchronous and significant Doppler motions . A radial velocity study of these lines which we associate with the secondary star , yields a semi-amplitude of K _ { 2 } =382 km s ^ { -1 } . A time-series analysis of the spectral and photometric data revealed a possible orbital periodicity of 2.85 h , significantly shorter than the reported 3.2 h periodic signal by Zurita et al . The observed variability properties argue against a low orbital inclination angle and we present several observational arguments in favour of the BH interpretation . However , the measured radial velocity semi-amplitude of the donor star and the short orbital period imply that SWIFT J1753.5–0127 has one of the lowest measured mass function for a BH in a low-mass X-ray binary . We show that the compact object mass in excess of 5 M _ { \odot } is highly improbable . Thus , SWIFT J1753.5–0127 is a BH binary that has one of the shortest orbital period and hosts probably one of the smallest stellar mass BH found to date .