ASAS-SN Discovery of 2 Cataclysmic Variables

ATel #4999; J. L. Prieto (Princeton), K. Hainline, R. Hickox (Dartmouth), A. Goulding (Harvard/CfA), A. Campillay, C. Gonzalez, E. Hsiao (Las Campanas Observatory), B. Shappee, C. S. Kochanek, K. Z. Stanek, J. Jencson, J. F. Beacom (Ohio State), A. Talabere (Metro High School/OSU), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), M. Dubberley, M. Elphick, S. Foale, E. Hawkins, D. Mullens, W. Rosing, R. Ross, Z. Walker (Las Cumbres Observatory)
on 22 Apr 2013; 17:40 UT
Credential Certification: Jose L. Prieto (jose@obs.carnegiescience.edu)

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During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the double 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered two new transient sources:

 Object       RA (J2000)  DEC (J2000)     Disc. UT Date     Disc. V mag 
ASASSN-13ad   20:28:51.1  -00:42:02.4    2013 April 13.59       15.8 
ASASSN-13ae   17:40:33.4  +41:47:57.3    2013 April 19.53       12.7 

ASASSN-13ad was present in images obtained 2013 UT Apr. 13 and Apr. 16, but undetected (V > 17) on 2013 UT Apr. 7 and earlier. Follow-up imaging obtained by C. Gonzalez on Apr. 21.4 with the Swope 1-m telescope at Las Campanas Observatory confirms the detection of the transient with B = 16.63 and V = 16.51 mag (+/- 0.03). This source is coincident with the position of a faint SDSS star at RA = 20:28:51.11, DEC = -00:42:05.6 (J2000). ASASSN-13ad is very likely a CV.

ASASSN-13ae was present in images obtained 2013 UT Apr. 19, but undetected (V > 17) on 2013 UT Apr. 16 and earlier. We checked in Vizier and find a faint optical source with B = 19.2 and R = 18.2 detected 2.7" from our ASAS-SN position in the USNO-A2 catalog. There is also a bright GALEX UV source detected at this position in the GALEX DR5 catalog, with FUV = 13.62 and NUV = 14.17 mag on 05/27/2007, probably an earlier outburst. An optical spectrum of this transient obtained by K. Hainline and A. Goulding on UT Apr. 21.41 with the MDM 2.4-m telescope and the OSMOS imaging spectrograph shows a blue continuum (black-body Teff = 16000 K) with Balmer and He I lines in absorption, and (probable) weak He II in emission. This spectrum is characteristic of a CV at peak, and a plot can be found here. We note that this CV was independently discovered by CRTS as source CSS130418:174033+414756.