AstroNote 2019-24

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 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 ESO 453- G 003. We discovered ATLAS19mco (AT2019gvp) on MJD 58637.42 == 2019-06-03.42, at m_c = 19.42 +/- 0.15. There was no detection by ATLAS on MJD 58635.47 == 2019-06-01.47. ATLAS19mco is offset by 8.51 arcsec south, 1.02 arcsec east from ESO 453- G 003, which is at z = 0.022 or d = 96.5 Mpc (from NED), implying an absolute magnitude of M = -16.71 (assuming m-M = 34.92 and A_g = 1.427 and A_r = 0.987). 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.