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THE ASTRONOMER Electronic Circular No 2898      2013 Mar 12 19.25UT
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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DISAPPEARANCE OF SUPERGIANT PROGENITOR OF SN 2011dh
Schuyler D. Van Dyk (IPAC/Caltech) et. al. report on The Astronomer's 
Telegram 4850 that in Hubble Space Telescope (HST) Wide Field Camera 3 
(WFC3) observations at F555W and F814W with the UVIS channel, conducted 
on 2013 March 2 UT they have discovered that the yellow supergiant star, 
identified by Van Dyk et al. at the position of the Type IIb SN 2011dh 
in Messier 51, has vanished.

 From preliminary photometry extracted from the 2013 images the HST 
flight-system magnitudes of the object seen at the position of the 
supergiant and SN are F555W = 23.20 +/- 0.02 and F814W = 22.51 +/- 0.02 
mag. The brightness of the supergiant in, e.g., Van Dyk et al. (2011) 
was F555W = 21.86 +/- 0.01 and F814W = 21.22 +/- 0.01 mag.
It is therefore evident that the yellow supergiant has disappeared.

A long series of post maximum photometry by Guy Hurst of this star ended 
on 2012 January 28.545UT (using both BRT and SSON) when the magnitude 
(unfiltered) was 18.0 but the faintness prevented extension of this run.

SUPERNOVA 2013U IN PGC 29001 (R. GAGLIANO ET. AL.)
2013U   Jan  5.28   10 01 12.00  +00 19 42.3  16.6   2.0"E    4.1"S
An image at: http://www.possdata.com/PSNJ10011200+0019423.jpg
L. Tomasella: spectrum Feb 6 a peculiar type-Ia event a few days before 
maximum

SUPERNOVA 2013V IN UGC 4798 (T. CROWLEY ET. AL.)
2013V   Jan  6.41   09 08 41.54  +44 48 49.6  17.8  11.5"W   11.1"S
An image at: http://www.possdata.com/PSNJ09084154+4448496.jpg
L. Tomasella: spectrum Feb 7 type-Ia

SUPERNOVA 2013W IN UGC 5448 (R. GAGLIANO ET. AL.)
2013W   Jan  6.32   10 06 34.02  +14 25 57.8  18.0  11.2"E    3.4"S
Image at: http://www.possdata.com/PSNJ10063402+1425578.jpg
L. Tomasella: spectrum Feb 7 type-IIn

SUPERNOVA 2013X (ROTSE)
2013X   Feb  6.23   12 17 15.19  +46 43 35.9  17.9:  4.9"E    3.8"S
A spectrogram of Feb. 10.51 UT with the 9.2-m Hobby-Eberly Telescope 
indicates it  is a 1991T-like supernova about 10 days after maximum 
brightness

Guy M Hurst