AstroNote 2020-58

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DRAFT
2020-03-03 19:51:40
Type: Object/s-Discovery/Classification
ATLAS20hgv (AT2020dul): discovery of a candidate supernova in NGC 5804 (59 Mpc)
Authors: M. Fulton, K. W. Smith, S. Srivastav, O. McBrien, S. J. Smartt, J. Gillanders, P. Clark, 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 ATLAS20hgv (AT2020dul) in galaxy NGC 5804. At a distance of 59 Mpc, the transient was discovered on MJD = 58902.56 (2020-02-23.56) with an absolute magnitude of M = -14.2 +/- 0.2.

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. More information is on the ATLAS homepage. We are submitting AstroNotes for transients that are either within 100 Mpc or have some other exciting 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 NGC 5804. We discovered ATLAS20hgv (AT2020dul) on MJD 58902.56 == 2020-02-23.56, at m_o = 19.64 +/- 0.19. There was no detection by ATLAS on MJD 58894.57 == 2020-02-15.57. ATLAS20hgv is offset by 19.3 arcsec north, 68.9 arcsec east from its likely host galaxy NGC 5804, which is at z = 0.014 or d = 59 Mpc (from NED), implying an absolute magnitude of M = -14.2 (assuming m-M = 33.85 and A_r = 0.04 and A_i = 0.03). We note that ATLAS20hgv is at a projected distance of 20Kpc from the likely host NGC 5804. It has risen to o=18.3 and appears close to peak  (M = -15.6) eight days after discovery, hence is intrinsically faint. Forced photometry plot is attached for reference. Follow-up observations of this young transient (which is faint and at a large distance from its host galaxy) are strongly 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 catalogues 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
TNS2020dul [ATLAS20hgv]14:57:13.902+49:40:27.82SN0.014NGC 58040.01379614:57:13.902+49:40:27.82SN Ia0.07