Quiescent X-ray/optical counterparts of the black hole transient H 1705−250

Abstract We report the result of a new Chandra observation of the black hole X-ray transient H 1705−250 in quiescence. H 1705−250 was barely detected in the new ∼50 ks Chandra observation. With five detected counts, we estimate the source quiescent luminosity to be L X ∼ 9.1 × 1030 erg s−1 in the 0.5-10 keV band (adopting a distance of 8.6 kpc). This value is in line with the quiescent luminosities found among other black hole X-ray binaries with similar orbital periods. By using images taken with the Faulkes Telescope North, we derive a refined position of H 1705−250. We also present the long-term light curve of the optical counterpart from 2006 to 2012, and show evidence for variability in quiescence.