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ASASSN-17dj: Discovery of A Probable Supernova

ATel #10155; Subo Dong (KIAA-PKU), K. Z. Stanek, J. S. Brown, T. W.-S. Holoien, C. S. Kochanek, J. Shields, T. A. Thompson (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), S. Bose, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory)
on 9 Mar 2017; 11:39 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Subo Dong (dongsubo@pku.edu.cn)

Subjects: Optical, Supernovae

Referred to by ATel #: 10162

ASASSN-17dj (AT 2017cav) was discovered in images obtained on UT 2017-03-07.58 at V~16.4 mag and was also detected on UT 2017-03-06.59 at V ~ 16.3 mag, on UT 2017-03-05.57 at V ~ 16.4 mag and on UT 2017-03-04.589 at V ~ 16.3. We do not detect (V>17.7) the object in images taken on UT 2017-02-22.63 and before. This figure shows the archival Pan-STARRS (Chambers et al. 2016, arXiv:1612.05560) g-band image of the host (left), the ASAS-SN V-band reference image (middle), and the ASAS-SN subtraction image (right). The red circle has a radius of 5" and is centered on the position of the transient in the subtraction image.

The position of ASASSN-17dj is close to that of a faint and diffuse object, probably the transient's host galaxy, in the Pan-STARRS archival image. 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-17dj  18:06:43.9   +06:50:19.6     2017-03-07.58      16.4            N/A                N/A  
Obs. UT Date         V mag  
2017-02-22.63       >17.7 
2017-03-04.59         16.3 
2017-03-05.59         16.4 
2017-03-06.59         16.3 
2017-03-07.58         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-17xx 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-17xx (AT 2017xyz) to preserve, rather than anonymize, the origin of the transient.

We 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 Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the Mt. Cuba Astronomical Foundation. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.