[IAUC] CBET 3998: 20141001 : PSN J23160979-4234575 IN NGC 7552

[quai en eps.harvard.edu]

                                                  Electronic Telegram No. 3998
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


PSN J23160979-4234575 IN NGC 7552
     G. Bock, Runaway Bay, Gold Coast, Queensland, Australia, reports the
discovery by P. Marples (Loganholme, Queensland) of a possible supernova (red
mag 17.3) on a 30-s unfiltered CCD image (limiting mag 17.5) taken by Marples
on Sept. 24.46 UT with a 30-cm Meade LX200R reflector (+ SXV-H9 Starlight
Xpress camera) in the course of the Backyard Observatory Supernova Search.
The new object is located at R.A. = 23h16m09s.79, Decl. = -42d34'57".5
(equinox 2000.0; reference stars from UCAC4 catalogue), which is 10".9 west
and 7".6 north of the nucleus of the galaxy NGC 7552.  Nothing is visible at
this position on Digitized Sky Survey red and infrared images (limiting red
magnitude > 19).  An image of the variable is viewable at website URL
http://tinyurl.com/ltqr3b5.  Bock confirmed the variable at red mag about
17.3 on several 30-s images (limiting mag about 18.0) taken at his Runaway Bay
Observatory with a 0.35-m reflector on Sept. 24.5.  S. Parker, Canterbury, New
Zealand, reports that nothing is visible at this position to a limiting
magnitude of about 18.5 on his images from Sept. 2.456, 10.449, and 23.662.
The variable was designated PSN J23160979-4234575 when it was posted at the
Central Bureau's TOCP webpage.

     N. Morrell, C. Contreras, C. Gonzalez, and M. M. Phillips, Las Campanas
Observatory; M. Stritzinger, E. Y. Hsiao, C. Gall, and S. Holmbo, Aarhus
University; F. Taddia, Stockholm University; and P. Sanchez and P. Lira,
Universidad de Chile -- on behalf of the Carnegie Supernova Project -- report
that an optical spectrogram (range 360-920 nm) of PSN J23160979-4234575,
obtained with the Las Campanas du Pont telescope (+ WFCCD) on Sept. 27.2 UT,
indicates that it is a "supernova imposter".  The visual-wavelength spectrum
is dominated by narrow (FWHM about 800 km/s) Balmer emission lines of H-alpha
and H-beta.  Given the lack of discernible [Ca II] at 729.1 and 732.4 nm, Ca
II near-infrared triplet features, and the presence of Na I at 589.3 nm, the
variable is found to resemble the early spectrum of the supernova imposter
that was designated SN 2002bu (IAUC 7863; Smith et al. 2011, MNRAS 415, 773).
Consecutive broad-band optical observations with the Swope telescope spanning
Sept. 25-29 UT indicate an approximately constant absolute B-band magnitude of
-13.8.  The faint intrinsic luminosity, the nature of the visual-wavelength
spectrum, and the probable recent non-detection altogether suggests that
PSN J23160979-4234575 is a young 2008S-like supernova imposter.


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                         (C) Copyright 2014 CBAT
2014 October 1                   (CBET 3998)              Daniel W. E. Green