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THE ASTRONOMER Electronic Circular No 2580      2009 Sep 02 17.57UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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LBV OUTBURST IN NGC 7259 (= 'SN 2009ip')
On CBET 1928 the CHASE project reported discovery of a possible 
magnitude 17.9 supernova in NGC 7259 on 2009 Aug 26.11UT and located at: 
RA 22h 23m 08.26s DEC -28 56' 52.4" (2000) which is about 36.2"E and 
25.1"N of the centre of NGC 7259. The object was then designated SN 
2009ip on CBET 1928.

However subsequently on Astronomer's Telegram 2183, A. A. Miller (UC 
Berkeley) et. al., report that they have examined historical images of 
NGC 7259 and find that a transient consistent with the location of SN 
2009ip was present in 2005. Relative to USNO-B1, preliminary photometry 
yields that the transient was at R ~ 20.6 mag on 2005 Jun 20 (UT dates 
are used throughout) and R ~ 21.0 mag on 2005 Jul 03. On a stacked image 
from 2008 Aug 23 they did not detect the transient down to R ~ 22.0 mag.

In a ground-based KAIT image taken on 2009 Aug 30, they measure the 
object to have an unfiltered magnitude of 18.2, which corresponds to an 
absolute magnitude of M ~ -13.7 mag at the distance of NGC 7259. Using a 
HST/WFPC2 image of 1999 June 29 they identify a potential progenitor at:
RA 22h 23m 08.20s DEC -28 56' 52.6" (2000), with F606W = 21.8 mag, which 
corresponds to an absolute magnitude of M ~ -10.1 mag at the distance of 
NGC 7259.

Given the relatively faint peak absolute magnitude (for a SN) of
-13.7 mag, and the recurrent nature of the observed transient, they 
argue that SN 2009ip is not a SN. Instead, they favour two alternative 
hypotheses to explain these observations: the transient is associated 
with an outburst from a luminous blue variable (LBV) star in NGC 7259, 
or (less likely) the transient is a Galactic cataclysmic variable (CV). 
Both LBVs and CVs are observed to exhibit multiple outbursts on 
timescales of years to decades, which could potentially explain the 
observed transients from 2005 and 2009.

In yet another report, this time on Astronomer's Telegram 2184, E. 
Berger (Harvard) et.al., report they have obtained medium-resolution 
optical spectra of the object in NGC 7259 with the Magellan Echellete 
Spectrograph mounted on the Magellan/Clay 6.5-m telescope on 2009 
September 1.24 UT.  The spectra exhibit narrow (FWHM ~ 550 km/s) 
hydrogen Balmer emission lines centred at the systemic velocity of NGC 
7259.  These properties, along with a peak optical absolute magnitude of 
about -13.7 mag, previous variability at the same position, and a 
potential progenitor with M~-10 mag (ATEL #2183) indicate it is a 
luminous blue variable (LBV) outburst, similar to previous 'SN 
impostors' such as SN1997bs (Van Dyk et al. 2000, PASP, 112, 1532).

SUPERNOVA 2009ij IN UGC 10923
Further to the announcement on TA E-Circular 2577 of the discovery by 
Tom Boles of a possible supernova in UGC 10923, M. L. Graham et. al., 
Department of Physics and Astronomy, University of Victoria; and Dave 
Balam, Dominion Astrophysical Observatory (National Research Council of 
Canada), report on CBET 1935 that a noisy spectrum obtained on Sept. 
1.28 UT with the 1.82-m Plaskett Telescope of the National Research 
Council of Canada, shows it to be a type-II supernova several days past 
maximum.

Guy M Hurst