ATLAS17lqv: discovery of a supernova candidate in the Kepler Campaign 15 field

ATel #10828; K. W. Smith, S. J. Smartt (Queen's University Belfast), J. Tonry, L. Denneau, B. Stalder, A. Heinze, H. Weiland (IfA, University of Hawaii), A. Rest (STScI), D. E. Wright (University of Minnesota)
on 6 Oct 2017; 14:25 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ken Smith (k.w.smith@qub.ac.uk)

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ATLAS is a twin 0.5m telescope system on Haleakala and Mauna Loa. Both units are operational and are robotically surveying the sky. Two filters are used, cyan and orange (denoted c and o, all mags in AB system), more information on http://www.fallingstar.com. While carrying out the primary mission for NEOs, we search for and publicly report stationary transients (see Tonry et al. ATel #8680).

We report a new transient source, most likely a supernova in galaxy 2MASX J15511737-1527048. We discovered ATLAS17lqv (AT2017hbf) on MJD 58024.22 == 2017-09-28.22 UTC at m_o = 17.87 +/- 0.13 (forced photometry).

ATLAS17lqv is 7.35 arcseconds from the centre of 2MASX J15511737-1527048 which is at z=0.037946 or d=162Mpc (from NED), implying an absolute magnitude of M = -18.54 (assuming m-M = 36.05 and A_o = 0.36 ). A summary of the transient's properties are shown below. Follow up observations are encouraged.

ATLAS17lqv also happens to be in the Kepler Campaign 15 (C15) field. (2MASX J15511737-1527048 is EPICID=250001081.) The proximity of transients to C15 galaxies is checked when surveying that region of the sky.

 
Name      | ATLAS Name | RA (J2000)  | Dec (J2000) | Disc. Date | Disc Mag | C15 Galaxy dist 
AT2017hbf | ATLAS17lqv | 15:51:17.65 | -15:27:10.6 |  20170928  |  17.87 o | 7.35" 

Mean daily forced photometry is shown below. Note that the object is setting, and is no longer visible to ATLAS after twilight.

 
Obs. MJD      mag  err filter    
58024.23    17.85 0.13 o 
58026.22    17.83 0.12 o 
58028.22    17.53 0.52 o