[vsnet-alert 15789] MASTER OT J200116.78+044142.6 - CV thought to be SR?

[Denis Denisenko]

Just published in Astronomer's Telegram ATel #5098,
http://www.astronomerstelegram.org/?read=5098

Vsevolod Yecheistov has found a new optical transient in MASTER-Amur
database which is positionally consistent with a variable star
USNO-A2.0 0900-17428262 discovered by T. Kryachko, A. Samokhvalov and
B. Satovskiy (PZP, Vol. 12, No. 21, 2012). See object #35 at
http://www.astronet.ru/db/varstars/msg/1269469 (the last one in the
list).

MASTER OT J200116.78+044142.6
  20130531.670  147C  MASTER-Amur
  20130531.706  146C  MASTER-Amur

Kryachko et al. report SR: type, possible period of 39.8d and
magnitude range 16.78-19.27 (unfiltered with the red zero point).
Phased light curve is indeed not regular:
http://images.astronet.ru/pubd/2012/12/13/0001274572/35_pc-r.png

I have found that the object is blue on Palomar plates (both POSS-II
and - what's more important - POSS-I taken on the same date, namely
1953 Sep. 05). USNO-A2.0 catalog is giving blue magnitudes:
USNO-A2.0 0900-17428262 20 01 16.80 +04 41 44.1 R=17.2 B=17.4

USNO-B1.0 0946-0506020 (20 01 16.742 +04 41 43.34) has a proper motion
of (-14, -14) mas/year, not expected for a semi-regular variable which
are usually red giants. The OT also has an UV counterpart GALEX
J200116.7+044143 (FUV=21.71+/-0.35, NUV=20.63+/-0.16).

Based on the blue color, amplitude of variability and proper motion we
suggest that MASTER OT J200116.78+044142.6 is a new cataclysmic
variable, likely a dwarf nova. Spectroscopic and photometric
observations are required.

Color-combined DSS finder chart:
http://master.sai.msu.ru/static/OT/J200116+044142-BRIR5x5.jpg
Discovery and reference images:
http://master.sai.msu.ru/static/OT/200116.78044142.6.png

Denis Denisenko
Member of MASTER team at SAI MSU