[vsnet-alert 23490] Re: ASASSN-18ey = MAXI J1820+070 : brighter

[Berto Monard astroberto13m@gmail.com via vsnet-alert]

Hello,

Just to compare magnitudes from the present outburst to that of 2018

JD / CCD-V / CCD-Ic / CCD-Rc

2458360.25	13.58	13.26	13.34
2458371.29	13.71	13.38	13.47
2458395.28	14.69	14.41	14.42
2458559.66	14.25	13.87	13.84
2458601.62	15.70	16.6:	15.7
			
2458706.40	16.85	15.1:	16.7
2458708.36	15.48	15.20	15.06
2458709.42	15.00	14.65	14.85
2458711.25	14.54	14.15	14.38
2458713.20	14.53	14.13	14.13 / 2019 august 17.7

Uncertainties vary roughly from 0.1 to 0.5 for mags 14 to 16: don’t quote…

reference stars: UCAC4 486-079582, 486-079603, 486-079608

Regards,

Berto Monard / CBA Kleinkaroo

Sent from Mail for Windows 10

From: mkimura
Sent: Saturday, August 17, 2019 12:08 PM
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.

Regards,
Mariko