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ASAS-SN Discovery of Candidate Supernova in SDSS J125258.03+322444.3

ATel #5665; B. J. Shappee, K. Z. Stanek, C. S. Kochanek, T. W-S. Holoien, J. Jencson, U. Basu, J. F. Beacom (Ohio State), J. L. Prieto (Princeton), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), J. Brimacombe (Coral Towers Observatory), D. Bersier (LJMU)
on 16 Dec 2013; 04:09 UT
Credential Certification: Benjamin Shappee (shappee@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 5667

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the recently expanded quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, possibly a supernova, in the outskirts of SDSS J125258.03+322444.3:

Object       RA (J2000)   DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-13dn  12:52:58.2  +32:25:09.3       2013 Dec. 15.60     15.7 

ASASSN-13dn was discovered in images obtained 2013 UT Dec. 15.60 at V~15.7. However, the object was also detected on Dec. 11.58, before we restarted our real-time pipeline after our expansion to 4 cameras. The discovery image showing both subtracted images can be found here with a 15" circle showing the location of the transient source. This source is undetected (V>17) in previous data taken at this location using our two camera setup (July 24.25). Additional commissioning data from our four camera setup is currently being analyzed.

The transient is approximately 25.0" North and 2.2" East of the star forming galaxy SDSS J125258.03+322444.3 (z=0.022805, d=97 Mpc from Virgo-infall corrected velocity, via NED), which would give it an absolute V mag of approx. -19.3 (m-M=34.93, A_V=0.043, Schlafly & Finkbeiner 2011) and a projected distance from the host galaxy of approximately 11.4 kpc. Follow-up observations are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN.