AstroNote 2020-215

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DRAFT
2020-11-05 15:36:38
Type: Object/s-Discovery/Classification
ATLAS20bewg (AT2020ywx): discovery of a candidate supernova in WISEA J115326.45+105347.2 (96 Mpc)
Authors: S. Srivastav, K. W. Smith, O. McBrien, S. J. Smartt, J. Gillanders, M. Fulton, D. R. Young, L. Shingles, M. McCollum (Queen's University Belfast), T.-W. Chen (Stockholm), J. Anderson (ESO), L. Denneau, A. Heinze, J. Tonry, H. Weiland (IfA, University of Hawaii), B. Stalder (LSST), A. Rest (STScI), D. E. Wright (University of Minnesota)
Source Group: ATLAS
Keywords: Supernova
Abstract:
Here we report the ATLAS discovery of the transient ATLAS20bewg (AT2020ywx) in galaxy WISEA J115326.45+105347.2 at magnitude o = 16.53 +/- 0.06. At a distance of 96 Mpc, the transient was discovered on MJD = 59157.62 (2020-11-04.62) with an absolute magnitude of M = -18.4 +/- 0.2. The last ATLAS non-detection was over 100 days ago, indicating the transient could be an old supernova. Spectroscopic classification is encouraged.

ATLAS is a twin 0.5m telescope system on Haleakala and Mauna Loa which is robotically surveying the sky above declination -40 with a cadence of 2 days (Tonry et al. 2018, PASP,130:064505). Two filters are used, cyan and orange (denoted c and o; all mags quoted are in the AB system). While carrying out the primary mission for Near Earth Objects, we search for and publicly report stationary transients to the IAU Transient Name Server.  Data processing is carried out at Queen's University which combines automated source parameter filtering, machine learning image recognition, and spatial cross-matching with astronomical catalogues (Smith et al. 2020, PASP, 132:085002). More information is on the ATLAS homepage. We are submitting AstroNotes for transients that are either within 100 Mpc, or have some other interesting feature to bring to the community's attention, such as bright nuclear transients, slowly rising or rapidly fading objects.

We report a new transient source, most likely a supernova in the galaxy WISEA J115326.45+105347.2. We discovered ATLAS20bewg (AT2020ywx) on MJD 59157.62 == 2020-11-04.62, at m_o = 16.53 +/- 0.06. There was no detection by ATLAS on MJD 59051.27 == 2020-07-21.27, indicating that this could be an old supernova. ATLAS20bewg is offset by 0.3 arcsec north, 3.8 arcsec west from its likely host galaxy WISEA J115326.45+105347.2, which is at z = 0.022 or d = 96 Mpc (from NED), implying an absolute magnitude of M = -18.4 (assuming m-M = 34.91 and A_r = 0.06 and A_i = 0.05). A finder and forced photometry plot are attached, followup observations are encouraged.  

This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. ATLAS is primarily funded to search for near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area.  The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen's University Belfast, and the Space Telescope Science Institute. 

Show current TNS values
CatalogNameReported RAReported DECReported Obj-TypeReported RedshiftHost NameHost RedshiftRemarksTNS RATNS DECTNS Obj-TypeTNS Redshift
TNS2020ywx [ATLAS20bewg]11:53:26.233+10:53:47.2411:53:26.229+10:53:47.31