A "high-hard" outburst of the black hole X-ray binary GS 1354-64

Karri Koljonen, David Russell, Jesus Corral-Santana, Montserrat Armas Padilla, Teo Munoz-Darias, Fraser Lewis

Research output: Contribution to journalArticle


In the shadows of the V404 Cyg outburst in the summer of 2015, GS 1354-64 (BW Cir) went into outburst as well. We followed the evolution of the outburst at optical, UV and X-ray wavelengths using Faulkes Telescope South, SMARTS and Swift. The outburst was found to stay in the hard X-ray state, albeit being anomalously luminous with a peak X-ray luminosity exceeding 0.15 LEdd, which could be the most luminous hard state observed in a black hole X-ray binary. In this talk I will present our results showing that the the outburst evolution at all wavelengths can be explained by the disk instability model with irradiation and disk evaporation/condensation. In addition, I will present our long-term optical monitoring results that show a statistically significant, slow rise of the source brightness over the 7 years prior to the 2015 outburst. This could be the much-sought observational evidence of matter slowly accumulating in the accretion disk, and subsequently getting optically brighter, as predicted by the disk instability model.
Original languageEnglish (US)
JournalAmerican Astronomical Society, AAS Meeting #228
StatePublished - Jun 1 2016


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