ATLAS17gtt : discovery of a bright nuclear transient in SDSS J103859.28+261258.6

ATel #10479; 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)
on 10 Jun 2017; 00:40 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Stephen Smartt (s.smartt@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 the galaxy SDSS J103859.28+261258.6. We discovered ATLAS17gtt (AT2017eoy) on MJD 57901.34 == 2017-05-28.34 UTC at m_c = 17.4 +/- 0.03.

ATLAS17gtt is within 0.5 arcseconds from the centre of SDSS J103859.28+261258.6 which is at z= 0.043095 or d=171Mpc (from NED). Implying an absolute magnitude of M = -18.9 (assuming m-M = 36.2 and A_g = 0.09 ) A summary of the transient's properties are summarised below. Follow up observations are encouraged. A possible detection is at c=19.6 on 57893.332, indicating the object is between 14-21 days old.

 
 
Name      | ATLAS Name | RA (J2000)  | Dec (J2000) | Disc. MJD | Disc. Date  | Disc Mag 
AT2017eoy | ATLAS17gtt | 10:38:59.29 | +26:12:59.0 | 57901.34  | 20170528.34 |  17.4 c         
 
Obs. MJD      mag  err filter   
57893.33       19.6 0.30  c 
57901.33       17.4 0.03  c 
57909.27       17.1 0.05  o  
57913.30       17.2 0.07  o