[vsnet-alert 23544] MAXI J1807+132 outburst

[Denis Denisenko d.v.denisenko@gmail.com via vsnet-alert]

Gaia has detected an outburst of this X-ray binary in Ophiuchus:

Gaia19dya = MAXI J1807+132
  20190906.141  15.60G  Gaia alerts
  20190906.215  15.68G  Gaia alerts
http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dya/

This is brighter than the maximum historical magnitude listed in AAVSO
VSX (16.1V), see
https://www.aavso.org/vsx/index.php?view=detail.top&oid=477464

ASAS-SN Sky Patrol (Shappee et al., Kochanek et al.) shows the
outburst has started between September 3rd and 5th:

MAXI J1807+132
  20190903.809  >171g   ASAS-SN
  20190905.117  16.11g  ASAS-SN
  20190905.119  15.75g  ASAS-SN
  20190905.120  16.19g  ASAS-SN
(ASAS-SN errors are 0.10-0.16 mag)

The previous outburst was observed in March 2017, see ATel #10216,
#10217 and #10227. Photometric time series are encouraged. Finder
chart from ATel #10217 (4'x4' FOV):
http://scan.sai.msu.ru/~denis/MAXIJ1807+132-BRIR-OVR.jpg

Checking the ZTF photometry at irsa.caltech.edu shows the minimum
magnitude to be 21.5r, 21.6g.

Denis Denisenko