Detection of 10-msec scale optical flares in the black-hole binary candidate MAXI J1820+070 (ASASSN-18ey)

ATel #11426; S. Sako, R. Ohsawa, M. Ichiki (the University of Tokyo), H. Maehara (Kyoto University), M. Morii (the Institute of Statistical Mathematics), M. Tanaka (National Astronomical Observatory of Japan), on behalf of the Tomo-e Gozen collaboration
on 16 Mar 2018; 07:10 UT
Credential Certification: Masaomi Tanaka (masaomi.tanaka@nao.ac.jp)

Tweet

We report detection of rapid optical variability in a black hole candidate MAXI J1820+070(ATel #11399, #11400, #11403, #11404, #11406, #11418, #11420, #11421, #11423, #11424, #11425). We performed high-speed photometry with time resolutions of 66.294- and 6.149-msec by using a wide-field CMOS camera, Tomo-e Gozen (Sako et al. 2016, SPIE, 9908, 99083P; Ohsawa et al. 2016, SPIE, 9913, 991339; http://www.ioa.s.u-tokyo.ac.jp/tomoe/ ), attached to the 1.05-m Kiso Schmidt telescope at Kiso observatory in Japan on March 14, 2018(UT). An optical counterpart was detected with no filter, sensitive in 350- to 700-nm (highest at ~500nm), as a point source at 18:20:21.935, +07:11:07.89 (J2000) with AB magnitude of about 12.6.

The light curve shows ~100-msec scale flare-like features with an amplitude of >100%. Quasi-periodic modulations with timescale of about 100 to 200 seconds and an amplitude of about 30% are also present in the light curve. Moreover, ~10-msec scale rapid variations are seen in the light curve with a time resolution of 6.149-msec. The light curves are shown in the following link: http://www.ioa.s.u-tokyo.ac.jp/tomoe/MAXIJ1820+070/MAXIJ1820+070.html

Further multi-wavelength and high-speed observations are encouraged to reveal the nature of the source. We plan continued monitoring of this source.

Tomo-e Gozen project: observations of MAXI J1820+070