[vsnet-chat 7440] On NGC 300 OT in 2008

[Taichi Kato]

   The existence of a bipolar outflow (in a progenitor OH/IR star)
and a high luminosity remind me of CK Vul (if the suggested identification
with the remnant nebulosity is correct).

cf.
http://adsabs.harvard.edu/abs/2007MNRAS.378.1298H

   By analogy, NGC300Var2008 might undergo repeated outbursts ?!

   And it might be worth noting the analogy with V838 Mon was also
proposed in CK Vul, too:

http://adsabs.harvard.edu/abs/2003A%26A...399..695K

===

http://arxiv.org/abs/0901.0198

The 2008 Luminous Optical Transient in the Nearby Galaxy NGC 300
Authors: Howard E. Bond 
(1), Alceste Z. Bonanos (1), Roberta M. Humphreys (2), L.A.G. Berto 
Monard (3), Jose L. Prieto (4), Frederick M. Walter (5) ((1) STScI, 
(2) U. Minnesota, (3) Bronberg Obs., (4) Ohio State U., (5) Stony 
Brook U.)
(Submitted on 1 Jan 2009)

Abstract: A luminous optical transient (OT) that appeared in NGC 300
in early 2008 had a 
maximum brightness, Mv ~ -13, intermediate between classical novae 
and supernovae. We present ground-based photometric and spectroscopic 
monitoring and adaptive-optics imaging of the OT, as well as pre- and 
post-outburst space-based imaging with HST and Spitzer. The optical 
spectrum at maximum showed an F-type supergiant photosphere with 
superposed emission lines of hydrogen, Ca II, and [Ca II], similar to 
the spectra of low-luminosity Type IIn "supernova impostors" like SN 
2008S, as well as cool hypergiants like IRC +10420. The emission 
lines have a complex, double structure, indicating a bipolar outflow 
with velocities of ~75 km/s. The energy released in the eruption was 
 ~2 x 10^47 ergs, most of it emitted in the first 2 months. By 
registering new HST images with deep archival frames, we have 
precisely located the OT site, and find no detectable optical 
progenitor brighter than broad-band V magnitude 28.5. However, 
archival Spitzer images reveal a bright, non-variable mid-IR 
pre-outburst source. We conclude that the NGC 300 OT was a heavily 
dust-enshrouded luminous star, of ~10-15 Msun, which experienced an 
eruption that cleared the surrounding dust and initiated a bipolar 
wind. The progenitor was likely an OH/IR source which had begun to 
evolve on a blue loop toward higher temperatures, but the precise 
cause of the outburst remains uncertain.