June 28, 2012: IAU Central Bureau Electronic Telegram 3155 (Daniel W. E. Green, ed.) announces the discovery (reported by A. Klotz on behalf of the TAROT collaboration) of a supernova in ESO 139-G28 on 2012 June 24.27 UT at R magnitude 14.6 +/- 0.1, using public images of the 0.25-m TAROT robotic telescope at La Silla, Chile.
Near-infrared spectra indicating the object to be a Type Ia supernova discovered a few days before maximum were obtained by E. Y. Hsiao, M. M. Phillips, N. Morrell, and C. Contreras (Las Campanas Observatory); J. Prieto (Princeton University); and G. H. Marion (Harvard-Smithsonian Center for Astrophysics), on 2012 June 26.7 UT with the Folded-port Infrared Echellette (FIRE) spectrograph on the 6.5-m Magellan Baade Telescope.
Hsiao et al. report that the spectrum of SN 2012db is similar to that of SN 2002cr at five days before maximum (Marion et al. 2009, A.J., 138, 727; http://adsabs.harvard.edu/abs/2009AJ....138..727M).
SN 2012db was initially designated PSN J17484870-6042193 when it was posted on the Central Bureau's TOCP webpage
Additional R-band CCD magnitudes for 2012db: 2012 June 6.302 UT, <17.9 (Klotz, via TAROT); 21.269, 14.7 (Klotz, via TAROT; pre-discovery); 25.4, 15.5 Bessell R (Ernesto Guido, Nick Howes, and Giovanni Sostero; remotely with the Faulkes Telescope South, Siding Spring).
Coordinates: RA 17 48 48.70 Decl. -60 42 19.3 (2000.0)
SN 2012db is offset 17" west and 4" north of the nucleus of ESO 139-G28.
Guido, Howes, and Sostero report position end figures 48.63s, 19.0"; annotated confirmation image posted at http://bit.ly/MvHRUT; animation comparing image and the 1990 red DSS posted at website URL http://bit.ly/KneUqF.
Charts for SN 2012db may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp).
Observations of SN 2012db should be submitted to the AAVSO using the name "SN 2012db".
Congratulations to the TAROT collaboration on its discovery!
This AAVSO Special Notice was compiled by Elizabeth O. Waagen.
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