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ATLAS discovery of bright nuclear transient flux in NGC4708 : ATLAS16bdg

ATel #9151; J. Tonry, L. Denneau, B. Stalder, A. Heinze, A. Sherstyuk (IfA, University of Hawaii), A. Rest (STScI), K. W. Smith, S. J. Smartt, D. Wright, D. R. Young (Queen's University Belfast), M. Huber, K. C. Chambers, H. Flewelling, M. Willman, N. Primak, A. Schultz, B. Gibson, E. Magnier, C. Waters, J. Tonry, R. J. Wainscoat (IfA, Hawaii)
on 14 Jun 2016; 11:50 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Stephen Smartt (s.smartt@qub.ac.uk)

Subjects: Optical, AGN, Supernovae, Transient

Referred to by ATel #: 9165

ATLAS is a twin 0.5m telescope system on Haleakala and Mauna Loa. The first unit is operational on Haleakala and is robotically surveying the sky. Two filters are used, cyan and orange (denoted c and o, all mags in AB system), more information is 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 high significance transient flux from the core of NGC4708. This is an SA-type galaxy at D=64 Mpc (mu = 34.0), which does not have a catalogued AGN. Transient flux was first detected at m_c = 18.1 on MJD=57544.3 and 4 days later rose to m_c=17. It is currently at m_o=16.3 or M_o = -17.8 (For reference MJD 57553 = 2016 06 14.)

The Pan-STARRS Survey for Transients (Huber et al. ATel #7153) and the Pan-STARRS1 Science Consortium Surveys (Smartt et al. ATel #5850) have covered this object over the last few years. Some residual flux at the galaxy centre is visible in the difference images, at i ~ 19.0 and w ~ 19.5. Without further analysis it is hard to tell if this real variability or subtraction residuals. The transient flux of the object ATLAS16bdg == AT2016cvn (on the TNS) is 3 magnitudes brighter than any possible historical variability. We consider this a candidate for either a circum-nuclear supernova or a tidal disruption event. Further multi wavelength observations are encouraged.

 
 
Name      | ATLAS Name | RA (J2000)  | Dec (J2000) | Disc. Date | Disc Mag |   z     
AT2016cvn | ATLAS16bdg | 12:49:41.34 | -11:05:34.3 |  57544.31  |  18.1  c | 0.013896  
 
 
Obs Date                  Mag  Filter  
57544.32    2016-06-05.32 18.1  c 
57548.32    2016-06-09.32 17.0  c 
57552.31    2016-06-13.31 16.3  o