ASASSN-16av: Discovery of A Type Ia Supernova in NGC 3926 NED02

ATel #8569; T. W.-S. Holoien, D. Bersier (LJMU), K. Z. Stanek, C. S. Kochanek, J. S. Brown, D. Godoy-Rivera, U. Basu (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory)
on 21 Jan 2016; 17:39 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@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 quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new type Ia supernova in the galaxy NGC 3926 NED02.

ASASSN-16av (AT 2016ac) was discovered in images obtained on UT 2016-01-18.44 at V~16.5 mag. We also detect the object in images obtained on UT 2016-01-21.64 (V~16.1), UT 2016-01-20.43 (V~16.7), UT 2016-01-19.59 (V~16.2), UT 2016-01-16.49 (V~17.4), and UT 2016-01-14.47 (V~16.9). We do not detect (V>17.9) the object in images taken on UT 2016-01-09.49 and before. This figure shows the archival DSS image of the host (left), the ASAS-SN V-band reference image of the host (center), and the ASAS-SN 2016-01-18 discovery subtraction image (right). The red circle has a radius of 5" and is centered on the position of the transient in the ASAS-SN image.

The position of ASASSN-16av is approximately 1.4" North and 0.4" West from the center of the galaxy NGC 3926 NED02 (z=0.025668, d=112 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.8 (m-M=35.25, A_V=0.075). Properties of the new source and photometry are summarized in the tables below:

 
Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-16av  11:51:28.20    +22:01:34.90        2016-01-18.44      16.5          -18.8               1.46 

 
Obs. UT Date         V mag 
2016-01-09.49        >17.9 
2016-01-14.47         16.9 
2016-01-16.49         17.4 
2016-01-19.59         16.2 
2016-01-18.44         16.5 
2016-01-20.43         16.7 
2016-01-21.64         16.1 

We obtained a low-resolution optical spectrum of ASASSN-16av on 2016-01-21.16 with the LT 2.0m telescope (+ SPRAT). The spectrum is consistent with a Type Ia a few days before maximum light at the redshift of the host. Cross-correlation with a library of supernova spectra using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) show that ASASSN-16av is a normal SN Ia at -4 days. The transient spectrum and SNID fit are can be seen in this figure.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported by NSF grant AST-1515927, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Mt. Cuba Astronomical Foundation, George Skestos, and the Robert Martin Ayers Sciences Fund. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.