On June 15th, 2015, one of black-hole binaries closest to Earth, V404 Cyg, underwent an outburst after 26 years of quiescence. The outburst was first detected by the Burst Alert Telescope on NASA's Swift satellite, which sent out an alert. TAOS telescopes automatically responded to the alert, and started to observe the black hole at 150 sec after the outburst detection. This was the earliest optical observation among numerous amount of observations by many instruments around the world triggered by this outburst.
TAOS's observation revealed that twinkles of the black hole, repetitive patterns in short-term variations, already existed in the very early stage of the outburst, which was reported in Atel#7722. This was the first time that this kind of variations in black holes were observed in optical light.
By a collaboration with Kyoto Univ. team, this result was published in the Jan. 7, 2016 issue of the journal Nature.
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