AstroNote 2020-166

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DRAFT
2020-08-27 22:00:41
Type: Object/s-Discovery/Classification
ATLAS20yki (AT2020scb): discovery of a candidate SN in CGCG 456-055 (72 Mpc)
Authors: 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, 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 ATLAS20yki (AT2020scb) in galaxy CGCG 456-055 at magnitude m_c = 19.20 +/- 0.18. At a distance of 72 Mpc, the transient was discovered on MJD = 59087.45 (2020-08-26.45) with an absolute magnitude of M = -15.24 +/- 0.18. The last non-detection through forced photometry was on MJD = 59085.47. 1 day later (MJD = 59088.47) the object has brightened to g = 18.5 as observed by ZTF (who discovered it simultaneously with ATLAS). 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 CGCG 456-055. We discovered ATLAS20yki (AT2020scb) on MJD 59087.45 == 2020-08-26.45, at m_c = 19.20 +/- 0.18. There was no detection by ATLAS on MJD 59085.47 == 2020-08-24.47. ATLAS20yki is offset by 7.2 arcsec north, 6.7 arcsec east from CGCG 456-055, which is at z = 0.0174 or d = 71.8 Mpc (redshift independent, from NED), implying an absolute magnitude of M = -15.24 (assuming m-M = 34.28 and A_g = 0.19 and A_r = 0.13). The candidate SN was also discovered simultaneously by ZTF (r = 19.2 mag, about 2.4 hours before ATLAS) and has brightened 1.1 days later (MJD = 59088.47) to around g = 18.5.  (See https://lasair.roe.ac.uk/object/ZTF20abwxywy/ .)  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
TNS2020scb [ATLAS20yki]00:18:25.632+18:30:59.590.017400:18:25.624+18:30:59.53SN Ic0.017429