MASTER Archival Observations of the Very Bright Cataclysmic Variable ASASSN-14mv

ATel #6857; D. Denisenko, V. Lipunov, E. Gorbovskoy, N. Tiurina, P. Balanutsa, V. Kornilov, N. Shatskiy, V. Chazov, A. Kuznetsov, V. Vladimirov (Lomonosov Moscow State University, SAI), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress (Irkutsk State University), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov (Ural Federal University), A. Tlatov, D. Dormidontov, V. Senik, A. Parkhomenko (Kislovodsk Solar Station of Pulkovo Observatory), V. Yurkov, A. Gabovich, Y. Sergienko, E. Sinyakov (Blagoveshchensk Educational University), V. Shumkov, S. Shurpakov (MASTER team members)
on 29 Dec 2014; 22:22 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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Following the posting of a bright CV candidate ASASSN-14mv at ASAS-SN Transients Page (Shappee et al., 2014) with the reported coordinates RA=07:13:27.25, Dec.=+20:55:52 and V=12.8m on 2014-12-29.32 UT we have checked MASTER database (Lipunov et al., 2010) around the position of this optical transient. The earliest MASTER-Kislovodsk observations of this field in Gemini were made in October 2009, MASTER-Amur - in January 2010, and MASTER-Tunka - in January 2011.

The object was caught in the bright outburst during the first observations by MASTER-Tunka at 2011-01-31.611 UT (unfiltered magnitude 11.85) and 2011-01-31.643 UT (11.86m). The coordinates measured by the robot are: 07h 13m 27.25s, +20d 55m 54s.3. Since there were no reference images of this field in MASTER-Tunka database in January 2011, the object was not detected as a transient. The object has faded to 15.0m on the images obtained at 2011-02-26.610 and 2011-02-26.650 UT. The comparison of MASTER-Tunka images on 2011-01-31.611 UT (outburst) and on 2014-12-25.832 UT (our latest observation before the current outburst) is posted at http://master.sai.msu.ru/static/OT/ASASSN-14mv-MASTER-Tunka.jpg

The object at quiescence is identical to the blue star USNO-A2.0 1050.04925422 (07 13 27.34 +20 55 54.9 R=17.7 B=16.8) = USNO-B1.0 1109-0151352 (07 13 27.28 +20 55 53.5 pmRA=-18 pmDE=-36 B1=17.31 R1=17.94 B2=17.58 R2=14.01 I=18.07). The star was in outburst on the 1991-03-07 POSS-II red plate and at quiescence on other 8 Palomar plates. Color-combined DSS finder chart is uploaded to http://master.sai.msu.ru/static/OT/ASASSN-14mv-BRIR.jpg (10'x10' FOV). There is an UV counterpart GALEX J071327.3+205553 (FUV=17.98+/-0.04) = GALEX J071327.5+205553 (NUV=17.43+/-0.02). There was no detection by ROSAT All-Sky Survey. This area of sky is not covered by SDSS. NEAT project has 77 images of this field from 1995 Dec. 24 to 2002 Oct. 04. No additional outbursts were detected.

However, probably the oldest outburst of this object was registered more than 75 years ago on the Heidelberg Astronomical Plates number D4995, D4996 and D4998 taken by A. Bohrmann on 1938-03-24 and 1938-03-25.

2011 outburst was also observed (but not detected as a transient) by Mount Lemmon Survey, see the light curve of MLS J071327.3+205553. Observations on 2011-01-26.243 UT (15.5m) were made on the rising stage of the outburst, and 2011-03-05.173 UT (15.3m) - on the fading part. Judging from the duration, 2011 outburst was definitely a superoutburst.

Based on the blue color, proper motion and outburst amplitude (~5m), ASASSN-14mv is a new cataclysmic variable, most likely a dwarf nova of SU UMa (UGSU) subtype. Photometric time series are required to determine the period of superhumps.

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