Poster abstract details

We present results from the spectral fitting of the candidate black hole binary Swift J1753.5-0127 in an accretion state previously unseen in this source. We fit the 0.7--78 keV spectrum with a number of models, all of which include a multi-temperature disk with an inner disk temperature $kT_{in}\sim0.3$ keV and a hard power law with photon index $\Gamma\sim2$. We report on the emergence of a soft component in the X-ray spectrum and we conclude that the source has entered the soft state for the first time in its $\sim$10 year prolonged outburst. Using reasonable estimates for the distance to the source and black hole mass, we find the unabsorbed luminosity (0.7--78 keV) to be $0.26\%$ the Eddington Luminosity, making this one of the lowest luminosity soft states recorded in X-ray binaries.