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ASASSN-18ca: Discovery of A Probable Nova in M31

ATel #11275; J. Brimacombe (Coral Towers Observatory), P. Vallely, K. Z. Stanek, C. S. Kochanek, J. S. Brown, J. Shields, T. A. Thompson (Ohio State), B. J. Shappee (IfA-Hawaii), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), M. Stritzinger, S. Holmbo (Aarhus)
on 8 Feb 2018; 10:05 UT
Distributed as an Instant Email Notice Novae
Credential Certification: David Bersier (dfb@astro.livjm.ac.uk)

Subjects: Optical, Nova, Transient

Referred to by ATel #: 11292

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Leavitt" telescope in Fort Davis, Texas, we discovered a new transient source, most likely a nova, in the nearby galaxy M31.

ASASSN-18ca (AT 2018pp) was discovered in images obtained on UT 2018-02-08.07 at g~16.5 mag. We do not detect (g>18.6) the object in images taken on UT 2018-02-06.12 and before. Images obtained on 2018-02-08 by J. Brimacombe confirm the discovery of the transient.

The position of ASASSN-18ca is approximately 4543" South and 148" West from the center of M31 (d=784 kpc, Stanek & Garnavich 1998, ApJ, 503, L131), giving an absolute g-band magnitude of approximately -8.2 (m-M=24.5, A_g=0.205). Properties of the new source and photometry are summarized in the tables below:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. g mag  Approx. Abs. Mag   Offset from Host (")  
ASASSN-18ca  00:42:34.40   +40:44:26.02      2018-02-08.07       16.5           -8.2          4545 
Obs. UT Date      g mag  
2018-02-06.12	  >18.6 
2018-02-08.07	  16.5 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-18xx 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-18xx (AT 2018xyz) to preserve, rather than anonymize, the origin of the transient.

We would like to thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the Villum Fonden (Denmark). For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients