ASAS-SN Discovery of 5 New Transient Sources

ATel #5052; B. J. Shappee (Ohio State), J. L. Prieto (Princeton), C. S. Kochanek, K. Z. Stanek, J. Jencson, A. Talabere, J. F. Beacom (Ohio State), 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 7 May 2013; 17:07 UT
Credential Certification: Benjamin Shappee (shappee@astronomy.ohio-state.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 five new transient sources:

 
Object       RA (J2000)  DEC (J2000)     Disc. UT Date     Approx. Disc. V mag 
ASASSN-13af   10:01:33.2  +74:24:47      2013 April 10.38       14.7 
 
ASASSN-13ag   17:27:00.8  +18:14:22      2013 April 18.57       15.8 
 
ASASSN-13ah   18:32:11.1  +61:55:09      2013 April 23.53       15.3 
 
ASASSN-13ai    9:39:56.0  +69:56:49      2013 May 3.40          16.4 
 
ASASSN-13aj   23:16:11.6  +27:34:50      2013 May 3.59          14.5 
 
 

ASASSN-13af was present in images obtained 2013 UT Apr. 10.4 but undetected (V > 17) on 2013 UT Apr. 4.3 and earlier. This source was still detected in images obtained on 2013 UT Apr 16.5 at V~15.3. We checked in Vizier and find a faint optical source with B = 18.3 and R = 18.2 detected 6" from our ASAS-SN position (ASAS-SN has 7.5" pixels) in the USNO-A2 catalog. ASASSN-13af is a possible CV.

ASASSN-13ag was present in images obtained 2013 UT Apr. 18.6 but undetected (V > 17) on 2013 UT Apr. 16.6 and earlier. This source was detected on two epochs before it faded and was again undetected in images obtained 2013 UT Apr. 24.5. We checked in Vizier and find a faint optical source with B = 20.4 and R = 20.2 detected 4" from our ASAS-SN position in the USNO-B1 catalog. There is also a GALEX UV source detected at this position in the GALEX DR5 catalog, with FUV = 21.37 and NUV = 21.61 mag. Furthermore, there is an X-ray source detection at this location by the XMM-Newton slew survey. ASASSN-13ag is likely a CV. We note that this CV was independently discovered by CRTS as source CSS130421:172701+181421 on 2013 UT Apr. 21.4.

ASASSN-13ah was present in images obtained 2013 UT Apr. 23.5 but undetected (V > 17) on 2013 UT Apr. 19.5 and earlier. This source was still detected in images obtained on 2013 UT Apr 29.5 at V~15.7. We checked in Vizier and find a faint optical source with B = 20.3 and R = 19.9 detected 4" from our ASAS-SN position in the USNO-B1 catalog. An optical spectrum of this transient obtained by J. L. Prieto on UT Apr. 29.27 with the Dual Imaging Spectrograph on the Apache Point Observatory 3.5m-telescope shows a blue continuum with Balmer lines in absorption, except for H-alpha that is in emission, with a double-peaked profile. This spectrum is characteristic of a CV at peak, and a plot can be found here.

ASASSN-13ai was present in images obtained 2013 UT May 3.3 but undetected (V > 17) on 2013 UT Apr. 26.3 and earlier. We checked in Vizier and find a faint optical source with B = 19.1 and R = 19.1 detected 4" from our ASAS-SN position in the USNO-A2 catalog. There is also a GALEX UV source detected at this position in the GALEX DR5 catalog, with FUV = 21.14 and NUV = 20.79 mag. Furthermore, there is a ROSAT X-Ray source 7" from our ASAS-SN position. ASASSN-13ai is likely a CV.

ASASSN-13aj was present in images obtained 2013 UT May 3.6 but undetected (V > 17) on 2013 UT Apr. 24.6 and earlier. We checked in Vizier and find a faint optical source with B = 19.9 and R=19.9 detected 1" from our ASAS-SN position in the USNO-B1 catalog. There is also a GALEX UV source detected at this position in the GALEX DR5 catalog, with FUV = 21.85 and NUV = 20.56 mag. Additionally, there are no nearby galaxy near the position of ASASSN-13aj. ASASSN-13aj is a possible CV or flare.