AstroNote 2021-224

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DRAFT
2021-08-25 15:58:43
Type: Object/s-Discovery/Classification
ATLAS21bgsc (AT2021wuf): discovery of a Ia supernova in NGC 6500/6501
Authors: S. Srivastav, K. W. Smith, S. J. Smartt, J. Gillanders, M. Fulton, D. R. Young, L. Shingles, M. McCollum, C. Richman (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 ATLAS21bgsc (AT2021wuf) in galaxy NGC 6500/6501 at magnitude o = 16.86 +/- 0.03. Assuming the host is NGC 6501 at 34 Mpc, the transient was discovered on MJD = 59449.37 (2021-08-23.37) with an absolute magnitude of M = -16.0 +/- 0.2. The last non-detection through forced photometry was on MJD = 59447.33. It has been classified as a young Ia, further followup 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 supernova in the galaxy NGC 6500/6501. We discovered ATLAS21bgsc (AT2021wuf) on MJD 59449.37 == 2021-08-23.37, at m_o = 16.86 +/- 0.03. There was no detection by ATLAS on MJD 59447.33 == 2021-08-21.33. ATLAS21bgsc could be associated with either NGC 6500 or 6501, both at z = 0.010. It is significantly offset by ~17 kpc from both galaxies. Assuming the host is NGC 6501 (d = 34 Mpc from NED), the absolute magnitude of the first detection is M_o = -16.0 (assuming m-M = 32.68 and A_r = 0.21 and A_i = 0.15). The light curve has since risen to M_o = -17.3 on MJD 59451.33 == 2021-08-25. It has been classified as a Ia by Huber et al. (TNS Classification Report No 10585). ATLAS forced photometry plot is attached, further followup observations are encouraged.  

The Asteroid Terrestrial-impact Last Alert System (ATLAS) project 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. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen's University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile. 

Show current TNS values
CatalogNameReported RAReported DECReported Obj-TypeReported RedshiftHost NameHost RedshiftRemarksTNS RATNS DECTNS Obj-TypeTNS Redshift
TNS2021wuf [ATLAS21bgsc]17:56:02.513+18:21:14.07SN Ia0.0117:56:02.510+18:21:14.08SN Ia0.01