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ASAS-SN Discovery of a Type Ia SN at maximum light

ATel #5110; J. L. Prieto (Princeton), S. Villanueva Jr., M. Fausnaugh, B. J. Shappee, K. Z. Stanek, C. S. Kochanek, 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 6 Jun 2013; 13:43 UT
Credential Certification: Jose L. Prieto (jose@obs.carnegiescience.edu)

Subjects: Optical, Supernovae, Transient

uring the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"; ATel #4987, #4999, #5010, #5082, #5102), using data from the double 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient close to the detection threshold of the survey:

  
Object       RA (J2000)   DEC (J2000)      Disc. UT Date      Approx. Disc. V mag  
ASASSN-13an  13:45:36.21  -07:19:32.62     2013 June 5.34              16.5     

ASASSN-13an was discovered in images obtained 2013 UT June 5.34, but it was also detected in images obtained on 2013 UT May 27. It was undetected (V > 17) in images obtained 2013 April 20 and earlier. Images obtained by S. Villanueva Jr. with the MDM 2.4m telescope (+OSMOS) on 2013 June 6.3 confirmed the detection of the new transient at ~3.3" W and 1.2" N from its host galaxy 2MASX J13453653-0719350. The confirmation image can be found here. A low-resolution spectrum obtained with OSMOS (range 3900-6900 Angstroms, FWHM res. = 7 Angs) shows that ASASSN-13an is a Type Ia SN around maximum light. After correcting for the recession velocity of the host galaxy (z=0.0216, measured from H-alpha emission line detected in the spectrum), we measure the velocity of the minimum of the Si II 6355 absorption feature at v(SiII minimum) = -10000 km/s. The Si II 6355 and 5972 features show a clear asymmetry. If the blue side of the features is interpreted as a second component it has v ~ -15000 km/s. The spectrum is shown here.