ASASSN-16hf: Discovery of A Probable Nova in M31

ATel #9245; J. Nicolas (Groupe SNAUDE, France), S. Kiyota (Variable Star Observers League in Japan), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, D. Godoy-Rivera, U. Basu (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory), J. M. Fernandez (Observatory Inmaculada del Molino), G. Krannich (Roof Observatory Kaufering), G. Masi (Virtual Telescope Project, Ceccano, Italy), R. S. Post (Post Astronomy), G. Stone (Sierra Remote Observatories)
on 15 Jul 2016; 02:57 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Jonathan Brown (brown@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 transient source, most likely a nova, in the nearby galaxy M31.

ASASSN-16hf (AT 2016dah) was discovered in images obtained on UT 2016-07-14.54 at V~16.4 mag. We also detect the object in images obtained on UT 2016-07-13.52 (V~16.6). We do not detect (V>17.6) the object in images taken on UT 2016-07-11.52 and before. Images obtained on 2016-07-14 by J. Nicolas and S. Kiyota confirm the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the J. Nicholas confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the J. Nicholas image.

The position of ASASSN-16hf is approximately 4053." South and 1338." East from the center of M31 (d=784 kpc, Stanek & Garnavich 1998, ApJ, 503, L131), giving an absolute V-band magnitude of approximately -8.3 (m-M=24.5, A_V=0.170). 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-16hf  00:44:41.073   +40:08:35.68     2016-07-14.54      16.4           -8.3                4268 

 
Obs. UT Date         V mag 
2016-07-11.52        >17.6 
2016-07-13.52         16.6 
2016-07-14.54         16.4 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-16xx transient names as our primary nomenclature (including supernovae, but also other classes of transients), and we encourage others to do the same. We prefer merging the names as ASASSN-16xx (AT2016xyz) to preserve, rather than anonymize, the origin of the transient.

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.