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THE ASTRONOMER Electronic Circular No 3093      2015 Jly 20 15.25UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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ASASSN-15MT: CATACLYSMIC VARIABLE CANDIDATE
G Simonian et. al. Ohio State reports on The Astronomer's Telegram 7809 that
during the ongoing All Sky Automated Survey for SuperNovae, using data from
the quadruple 14-cm "Brutus" 
telescope in Haleakala, Hawaii, they discovered a transient source:

Object        RA (J2000)    DEC (J2000)  Disc. UT Date  Disc. V mag
ASASSN-15mt   19:12:35.39   +50:34:39.3  2015-07-18.42   13.7 

ASASSN-15mt was discovered at V=13.7 in "Brutus" images taken on 2015 July
18.42, but not present (V>17.5) in images taken on 2015 July 13.42. At the
position of the transient, Vizier reports a match to a faint B=20.0 USNO
source. This transient also lies within the Kepler field as KIC 12055999.
Photometry from the Kepler-INT survey (Greiss et al 2012) yields magnitudes:
U=19.1, g=19.9, r=19.5, i=19.0, Ha=18.6.

ASASSN-15mt is most likely a dwarf nova outburst.

Denis Denisenko, Sternberg Astronomical Institute reports checking the
Palomar Plates and finds a possible new variable 77" East of ASASSN-15mt.
This is likely a flaring red dwarf of UV Ceti type.

Animation of 1953, 1988 and 1990 POSS Blue plates centred at ASASSN-15mt:
http://hea.iki.rssi.ru/~denis/ASASSN-15mt-newVar-anim-Blue.gif
(200x200" FOV at 2x zoom)
The new variable is marked as 'New Var' to the left from ASASSN-15mt.

The star has B2=20.01 in USNO-B1.0 measured from 1988 June 20 plate, but it
has brightened at least to 18.8m on the 1990 July 21 POSS-II Blue plate.
Taking into account the long exposure time of POSS-II plates (60 minutes on
1990 July 21) and the short duration of UV Ceti flares (typically a minute),
the real range of variability may be much larger (up to 15m).

The variable was submitted to AAVSO VSX with the temporary name DDE 40 and
the following IDs:
USNO-B1.0 1405-0308849 = KIC 12056056 = 2MASS J19124371+5034398 = WISE
J191243.68+503439.7 J-K and W1-W2 colours are typical for red dwarfs, and
URAT1 gives a proper motion of (5.5, -19.4) mas/yr.

Finder chart centred at DDE 40:
http://hea.iki.rssi.ru/~denis/DDE40-BRIR5x5.jpg

Please take a look at this star for time-resolved photometry of ASASSN-15mt.

Guy M Hurst