[IAUC] CBET 3416: 20130216 : SUPERNOVA 2013aa IN NGC 5643 = PSN J14323388-4413278

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                                                  Electronic Telegram No. 3416
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2013aa IN NGC 5643 = PSN J14323388-4413278
     Stuart Parker, Canterbury, New Zealand, reports the discovery of an
apparent supernova (red mag 11.9 ) on a 30-s unfiltered CCD image (limiting
mag 19) taken by himself on Feb. 13.621 UT with a 30-cm Astro-Tech AT12RC
Ritchey-Chretien astrograph (+ ST10 camera) at his Parkdale Observatory in the
course of the Backyard Observatory Supernova Search.  The new object is
located at R.A. = 14h32m33s.88, Decl. = -44d13'27".8 (equinox 2000.0;
reference stars from UCAC4 catalogues; measured by Colin Drescher, Calamvale,
Queensland, Australia), which is 74" west and 180" south of the nucleus of
the galaxy NGC 5643.  Nothing is visible at this position on an unfiltered
CCD image taken on Feb. 1.602 by Parker or on Digitized Sky Survey red and
infrared images (limiting red magnitude > 19).  Parker posted an image of
the new object at website URL http://tinyurl.com/dx7tfrx.  The variable was
designated PSN J14323388-4413278 when it was posted at the Central Bureau's
TOCP webpage and is here designated SN 2013aa based on the spectroscopic
confirmation reported below.  A. Amorim, Florianopolis, Brazil, reports
the following visual magnitude estimates for 2013aa obtained with a 0.18-m
reflector:  Feb. 16.1243, 11.6; 16.2938, 11.5.

     J. T. Parrent, Las Cumbres Observatory Global Telescope (LCOGT) and
Dartmouth College; D. Sand, Texas Tech University; and S. Valenti, M. L.
Graham, and D. A. Howell, LCOGT and University of California at Santa Barbara,
report spectroscopic observations of PSN J14323388-4413278 = SN 2013aa.  A
spectrogram (range 350-1000 nm) obtained robotically on Feb. 15.70 UT with
the FLOYDS (FTS) spectrograph shows it to be a type-Ia supernova, a few days
before maximum light.  A second spectrogram (range 350-950 nm) was also
acquired with the Gemini Multi-Object Spectrograph (GMOS) on the 8-m Gemini
South telescope on Feb. 15.38, confirming the classification.  After
correcting for the recession velocity of its host-galaxy, NGC 5643 (1199
km/s; via NED), the minimum of the Si II 635.5-nm absorption feature is found
to be blue-shifted by about 10960 km/s.  Comparisons to other spectra with
"Superfit" (Howell et al. 2005, Ap.J. 634, 1190) show similar overlap with
SN 1996X near maximum light.  By Feb. 15.38, there was no conspicuous
signature of C II 657.8-nm; however, a small depression is seen on top of
the Si II 635.5-nm emission component, at 634.7 nm, similar to that of SN
2011fe near maximum light (Pereira et al. 2013, pre-print, as posted at
website URL http://xxx.lanl.gov/abs/astro-ph/?0008463).


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                         (C) Copyright 2013 CBAT
2013 February 16                 (CBET 3416)              Daniel W. E. Green