[vsnet-alert 15640] (ATEL) ASASSN-13ad and CSS J174033.5+414756

[Taichi Kato]

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ATEL #4999							     ATEL #4999

Title:	ASAS-SN Discovery of 2 Cataclysmic Variables
Author:	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)
Queries:	jprieto at astro.princeton.edu
Posted:	22 Apr 2013; 17:40 UT
Subjects:Optical, Cataclysmic Variable, Transient

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 
href="http://skyserver.sdss3.org/dr9/en/tools/explore/obj.asp?id= 
1237663525421450638">a faint SDSS star</a> 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 <a 
href="http://www.astro.princeton.edu/~jprieto/asassn_13ae.png">here</a>.

We note that this CV was independently discovered by CRTS as source <a

href="http://nesssi.cacr.caltech.edu/catalina/20130418/1304181400734166981.html">CSS130418:174033+414756</a>.