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THE ASTRONOMER Electronic Circular No 2744      2011 Jun 08 14.51UT
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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SUPERNOVA 2011dh IN M51 = PSN J13303600+4706330
Further to the discovery announcement on TA E-Circular 2743, the 
following lists apparent independent discoveries in the order they were 
received at The Central Bureau:
(1) Tom Reiland, Glenshaw, U.S.A. (June 2.189 UT, visual; 53-cm)
(2) Thomas Griga, Schwerte, Germany (June 1.967; 30.5-cm refl.)
(3) Amedee Riou, Becon, France (June 1.893; 25.4-cm refl.)
(4) Stephane Lamotte Bailey, France (June 2.036; 0.20-m Celestron8)

Reported magnitudes (from unfiltered CCD images unless noted otherwise):
2011 May 30.90, <19.5 (Herman Mikuz and B. Dintinjana); 31.954, 14.1 
(Marulla, Grenier); June 1.893, 14 (Riou); 2.036, 13.7 (Lamotte Bailey); 
2.721, 14.4 (Sun, Gao); 2.9286, 14.6 (Dupouy); 3.085, 14.6 l(Broens) ; 
3.18, 14.8 (Koff)

J. M. Silverman, S. B. Cenko, and A. V. Filippenko, University of 
California, Berkeley, report that inspection of a CCD spectrum
obtained on June 3 UT with the 10-m Keck I telescope shows it is a 
type-II supernova with well-developed P-Cyg line profiles.  The spectrum 
shows a relatively blue continuum, with the broad H-alpha emission 
component dominating over the absorption component.  After removal of 
the host-galaxy recession velocity of 600 km/s (Rush et al. 1996, Ap.J. 
473, 130), the minimum of the H-alpha absorption is blueshifted by about 
17600 km/s.

W. Li and A. V. Filippenko, report on 'The Astronomer's Telegram 3399 
that they have isolated a possible progenitor in Hubble Space Telescope 
images taken with the Advanced Camera for Surveys (ACS). It is within 
the 0".09 uncertainty of the supernova position.
The position of the candidate progenitor is measured to be:
RA 13h 30m 05.119s, DEC +47 10'11.55" (2000)

Editor:

An appeal has been received from several sources for details of images 
of Messier 51 obtained between 2011 May 30 and June 2. So, if you have 
imaged this galaxy using a telescope and a digital device, your data may 
be very useful. Please quote date and time (UT), together with details 
of equipment used and filters (if appropriate).

Guy M Hurst