[vsnet-alert 23489] Re: ASASSN-18ey = MAXI J1820+070 : brighter

Josch Hambsch hambsch at telenet.be
Sat Aug 17 20:49:07 JST 2019

Dear Mariko,

I have sent the recent observations to the VSNET team.


-----Original Message-----
From: vsnet-alert [mailto:vsnet-alert-bounces at ooruri.kusastro.kyoto-u.ac.jp] On Behalf Of mkimura
Sent: Samstag, 17. August 2019 12:09
To: vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp; vsnet-outburst at ooruri.kusastro.kyoto-u.ac.jp
Subject: [vsnet-alert 23488] ASASSN-18ey = MAXI J1820+070 : brighter

ASASSN-18ey = MAXI J1820+070 : brighter

As reported by Keito, this object entered the 2nd rebrightening, and is brighter than 15 mag now.
This rebrightening seems to be an inside-out outburst considering ATel #13014.  Keisuke already found two weeks ago that this object has not yet returned back to the quiescent state (ATel #12988).

It is noteworthy that this object is the 2nd black-hole binary showing multiple rebrightenings in the history of the studies of black-hole X-ray transients (The 1st object was V518 Per).  Considering the similarities with WZ Sge-type dwarf novae, this object likely has a small binary mass ratio defined as the mass ratio of the secondary star with respect to the primary black hole.
This 2nd rebrightening gives us an great opportunity to investigate the veiled nature of accretion disks around black holes.
Further observations are encouraged.


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