[IAUC] CBET 2754: 20110630 : PSN J17592296+0617267 IN NGC 6509

[quai en eps.harvard.edu]

                                                  Electronic Telegram No. 2754
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 J17592296+0617267 IN NGC 6509
     Further to CBET 2745, J. Kelly, S. B. Cenko, W. Li, and A. V. Filippenko
report the LOSS discovery of an apparent supernova on unfiltered KAIT images.
The object was designated PSN J17592296+0617267 when posted at the Central
Bureau's TOCP webpage.  The discovery observation is tabulated below.

   2011 UT        R.A. (2000.0) Decl.      Mag.      Offset
   June 24.37   17 59 22.96  + 6 17 26.7   18.5    34".4 W, 13".6 N

Additional CCD magnitudes (unfiltered unless noted otherwise) for PSN
J17592296+0617267:  a co-added frame from June 2 to 19 UT, [19.8 (KAIT); June
24.37, 18.6 (KAIT); 25.426, 18.2 (J. Brimacombe, Cairns, Australia; position
end figures 23s.03, 25".7); 25.925, 18.2 (Federica Luppi, Schiaparelli
Observatory, Varese, Italy, 0.36-m f/7.9 reflector + Bessell R filter;
position end figures 22s.99, 26".1); 26.333, 18.7 (Brimacombe; position
end figures 22s.99, 26".5).  Luppi adds that nothing is visible at this
position on Digitized Sky Survey red, blue, and infrared images (limiting
red mag about 19.5 on 1991 June 16); her image is posted at website URL
http://www.astrogeo.va.it/pub/TOCP/PSN_N6509.jpg.  Brimacombe's image from
June 25 is posted at http://www.flickr.com/photos/43846774@N02/5868925873/.
Brimacombe's image from June 26 is posted at the following website URL:
http://www.flickr.com/photos/43846774@N02/5875580438/.

     J. M. Silverman, S. B. Cenko, P. E. Nugent, and A. V. Filippenko,
University of California, Berkeley, report that inspection of a CCD spectrum
(range 340-1000 nm), obtained on June 29 UT with the 10-m Keck I telescope (+
LRIS), shows that PSN J17592296+0617267 very closely resembles SN 2008S at
early phases (Smith et al. 2009, Ap.J. 697, L49).  Strong, intermediate-width
(FWHM roughly 1000 km/s) hydrogen Balmer and Ca II near-infrared triplet
emission lines are superposed on a relatively featureless continuum, and there
are very narrow (unresolved) prominent [Ca II] emission lines as well.  Thus,
this object is most likely a "supernova impostor" resembling a type-IIn
supernova, but resulting from the outburst of a luminous blue variable star.
Note that the Ca II H and K absorption lines are extremely strong, yet Na I D
absorption is weak, suggesting that the Ca II lines are of circumstellar
origin and may well be variable; further spectroscopic monitoring is
encouraged.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2011 CBAT
2011 June 30                     (CBET 2754)              Daniel W. E. Green