[vsnet-alert 16141] MASTER OT J204723.04+072759.1 (ATEL)

[Taichi Kato]

MASTER OT J204723.04+072759.1

> No previous outbursts were detected by Catalina Sky Survey.

   Isn't this a previous outburst?  (combined magnitude)

1107111083058	15.81	0.07	311.8460	 7.4664	54563.49293
1107111083058	15.81	0.07	311.8460	7.4664	54563.49794

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ATEL #5255							     ATEL #5255

Title:	New CV detected by MASTER
Author:	S. Shurpakov, D. Denisenko, V. Lipunov, E. Gorbovskoy, P.
		Balanutsa, N. Tiurina, V. Kornilov, A. Belinski, N. Shatskiy, V. Chazov,
		A. Kuznetsov, V. Yecheistov (Moscow State University, SAI), V. Yurkov,
		Y. Sergienko, D. Varda, E. Sinyakov, A. Gabovich (Blagoveshchensk
		Educational University), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov,
		O. Chuvalaev, V. Poleshchuk, O. Gress, A. Frolova (Irkutsk State University),
		V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov (Ural Federal
		University), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk
		solar station of the Pulkovo observatory RAS), P. Podvorotny, V. Shumkov
		(MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci,
		C. Lopez and F. Podest (OAFA)
Queries:	lipunov2007 at gmail.com
Posted:	7 Aug 2013; 11:05 UT
Subjects:Optical, Cataclysmic Variable, Transient

MASTER OT J204723.04+072759.1 - new bright CV

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 20h
47m 23.04s +07d 27m 59.1s on 2013-08-05.60683 UT. The OT unfiltered magnitude
is 
15.5m
(limit 18.2m). The OT is seen in 6 images. There is no minor planet at
this place. We have reference image without OT on 2013-04-21.80722 UT with
unfiltered magnitude limit 16.5m. 

The OT is located within 1.5" of the faint blue star which is present on
digitized Palomar plates, in USNO-B catalogue as USNO-B1.0 0974-0693904
(20 47 22.960 +07 28 00.20 B1=20.56 B2=21.42) and in GSC 2.3.2 with jmag=21.58.
There is a ~17.5m star 6" East (in PA~100) of the OT which can contaminate
the measured magnitude of the new variable. Color-combined (BRIR) DSS finder
chart is uploaded to http://master.sai.msu.ru/static/OT/J204723+072759-BRIR5x5.jpg

The object has an UV counterpart GALEX J204723.0+072800 (FUV=21.17+/-0.34,
NUV=21.51+/-0.27). There is nothing at this position in 2MASS, 1RXS, GCVS
and AAVSO VSX. The nearest known variable star is NN Del (eclipsing binary
with the highly eccentric orbit) 10' away. No previous outbursts were detected
by Catalina Sky Survey. This area of sky in Delphinus is not covered by
SDSS. 

Based on the UV detection by GALEX and outburst amplitude (~5.5m) we conclude
that MASTER OT J204723.04+072759.1 is a new cataclysmic variable, most
likely a dwarf nova of UGSU (SU UMa) type in superoutburst. Follow up observations,
as well as checking the archival observations of this field are encouraged.
The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/204723.04072759.1.png

<center><a href="http://observ.pereplet.ru/MASTER_OT.html">List of Optical
Transients discovered by MASTER</a></center>

Global MASTER Robotic Net: http://observ.pereplet.ru