AstroNote 2020-126

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DRAFT
2020-06-25 11:44:25
Type: Object/s-Discovery/Classification
ATLAS20qoq (AT2020nlb): discovery of a candidate SN in MESSIER 85 (17 Mpc)
Authors: A. Townsend (Queen's University Belfast / University of Manchester), K. W. Smith, S. Srivastav, O. McBrien, S. J. Smartt, J. Gillanders, P. Clark, M. Fulton, D. O'Neill, D. R. Young, M. McCollum (Queen's University Belfast), T.-W. Chen (Stockholm), J. Anderson (ESO), L. Denneau, H. Flewelling, 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 ATLAS20qoq (AT2020nlb) in galaxy MESSIER 85. The transient was discovered on MJD 59025.3 (2020-06-25.3) at m_o = 17.44 +/- 0.08. At a host distance of 17 Mpc, this corresponds to an absolute magnitude of M = -13.7 +/- 0.2. We have a recent non-detection two days before on MJD 59023.3 (2020-06-23.3), indicating this is a newly discovered transient and most probably a very young supernova. Rapid multi-wavelength follow-up of the source is strongly 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, 13, 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, arXiv:2003.09052). 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 MESSIER 85. We discovered ATLAS20qoq (AT2020nlb) on MJD 59025.3 == 2020-06-25.3 at m_o = 17.44 +/- 0.08. There was no detection by ATLAS on MJD 59023.3 == 2020-06-23.3. ATLAS20qoq is offset by 44.3 arcsec North, 1.2 arcsec east from MESSIER 85, which is at z = 0.0024 or d = 17 Mpc (from NED), implying an absolute magnitude of M = -13.7 (assuming m-M = 31.09 and A_r = 0.07 and A_i = 0.05).

The recent non-detection and faint absolute magnitude imply this is a new transient and most likely a very young, nearby supernova. Rapid multi-wavelength follow-up of the source is strongly encouraged. A screenshot of the ATLAS forced photometry and finders are attached.

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
TNS2020nlb [ATLAS20qoq]12:25:24.181+18:12:12.52MESSIER 850.00243212:25:24.188+18:12:12.80SN Ia