Una supernova a M82

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Fri, 15/05/2009 - 21:20 #1
Josep Maria
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Una supernova a M82

Electronic Telegram No. 1803
Central Bureau for Astronomical Telegrams
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
[email protected] or FAX 617-495-7231 (subscriptions)
[email protected] (science)
URL http://www.cfa.harvard.edu/iau/cbat.html

A. Brunthaler, K. M. Menten, and C. Henkel, Max-Planck-Institut fuer
Radioastronomie; M. J. Reid, Harvard-Smithsonian Center for Astrophysics;
G. C. Bower, University of California, Berkeley; and H. Falcke, University
of Nijmegen and ASTRON, report the discovery of a radio supernova in M82.
The position of 2008iz is R.A. = 9h55m51s.55, Decl. = +69o40'45".8 (equinox
2000.0), which is 2".0 west and 1".3 south of the radio kinematic center
(Weliachew et al. 1984, A.Ap. 137, 335). SN 2008iz was first discovered as
a bright radio transient of unknown origin (cf. http://www.astronomerstelegram.
org/?read=2020; also, Brunthaler et al. 2009, A.Ap., in press, with a pre-
publication version posted at http://lanl.arxiv.org/abs/0904.2388). VLBI
images taken with the NRAO Very Long Baseline Array, the phased Very Large
Array, the Green Bank Telescope, and the Effelsberg 100-m telescope on 2008
May 3 and 2009 Apr. 8 at 22 GHz show (at sub-milliarcsecond resolution) a
ring-like structure with an expansion velocity of roughly 11000 km/s (for an
assumed distance of 3.6 Mpc). This confirms the supernova nature of this
source. The measured expansion rate indicates an explosion date in late
January 2008. Very Large Array observations on 2009 Apr. 27 at 1.4, 4.8,
8.4, 22, and 43 GHz indicate an optically thin syncrotron sprectrum with a
spectral index of -0.8 (typical for type-II supernovae).

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superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2009 CBAT
2009 May 15 (CBET 1803) Daniel W. E. Green