[vsnet-alert 21103] MASTER OT J132501.0+431846.1 - possible WZ Sge dwarf nova

[Denis Denisenko]

MASTER team has reported a large-amplitude transient in Canes Venatici
MASTER OT J132501.0+431846.1 (P. Balanutsa, V. Lipunov, R. Rebolo et al.,
ATel #10470), see http://www.astronomerstelegram.org/?read=10470

MASTER_OT_J132501.0+431846.1
  20170605.955    15.4CV    MASTER-IAC

The OT is located 3.6' NW of NGC 5145 galaxy (and 2 deg ENE of M63), but
most likely is an extreme dwarf nova of WZ Sge type. There is nothing at
this position in SDSS and PanSTARRS combined images down to ~23m.

I have confirmed the new object remotely with 0.61-m iTelescope.Net T24 in
Auberry, CA. The following photometry was obtained from sums of 3x60-sec
unfiltered exposures:

MASTER_OT_J132501.0+431846.1
  20170607.30054  14.827CV  T24
  20170607.30376  14.843CV  T24
  20170607.30652  14.861CV  T24
  20170607.30936  14.822CV  T24
  20170607.31492  14.844CV  T24
  20170607.31896  14.883CV  T24
  20170607.32193  14.843CV  T24
  20170607.32472  14.855CV  T24

I have used APASS magnitudes for two reference stars:

GSC 03031-00475 (V=12.914)
GSC 03031-00608 (V=13.909)

Positions of the object and reference stars are shown at the image
http://scan.sai.msu.ru/~denis/J132501+431846-T24-photometry.gif

The object has brightened since the discovery detection by MASTER.
Outburst amplitude is more than 8m. Observations are strongly encouraged!

Denis Denisenko
Sternberg Astronomical Institute of Moscow State University