Rebrightening of MAXI J1820+070 (ASASSN-18ey) in X-rays
ATel #13025; Yanjun Xu (Caltech), Fiona Harrison (Caltech) and John Tomsick (UCB/SSL)
on 14 Aug 2019; 05:53 UT
Credential Certification: Yanjun Xu (yanjun@caltech.edu)
Subjects: X-ray, Black Hole, Transient
Following the report of steady optical rebrightening of the black hole X-ray transient MAXI J1820+070 (ASASSN-18ey) on August 10, 2019 (ATEL #13014), Swift observed MAXI J1820+070 with XRT twice at August 11 UT 16:12 and August 13 UT 12:40. Fitting the Swift XRT data with an absorbed power-law model (with nH fixed at 1.5e21 cm^-2), we measure the 0.5-10.0 keV flux of (4.5+/-1.4)e-13 erg/cm^2/s and (2.1+/-0.3)e-12 erg/cm^2/s for the first and second observation, respectively. This indicates a rapid brightening of MAXI J1820+070 in X-rays, with a flux increase by ~5 times in less than 2 days. The delay between the optical and X-ray brightening is expected from disk instability models and can be used to infer where the outburst began in the accretion disk (Orosz et al. 1997).
We have requested further Swift XRT monitoring of MAXI J1820+070. The rise of MAXI J1820+070 (ASASSN-18ey) in the X-ray band provides encouragement for coverage at other wavelengths.
