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Date: Tue, 30 Mar 1993 0:56:16 -0800 (PST)
From: ALEX@BKYAST.BERKELEY.EDU (ALEX FILIPPENKO, UC BERKELEY, 510-642-1813)
Subject: SN in M81!
3-30-93, 12:30 am
Dear Nova and Supernova Observers:
The object discovered by Madrid amateur astronomers in M81 is a
supernova! The spectral classification is uncertain at this time,
because the spectrum is so featureless, but it is probably Type II.
It is imperative that good optical spectra, spanning as wide a
wavelength range as possible, be obtained as often as possible during
the next few months. This will be difficult on large telescopes during
the upcoming bright run (next 2 weeks) --- but small telescopes can
easily be used to get superb spectra of such a bright object.
Again, I urge that observations be obtained throughout the spectrum:
UV, optical, and IR are particularly important in the near future, but
GRO and other satellites should try, too.
Here is a message we sent to Brian Marsden and Dan Green.
Cheers,
Alex Filippenko
***************
3-29-93, 11:55 pm
Brian and Dan,
We got it!! Here is an update which contains the information for
both the images and the spectra. You can ignore the previous version.
Cheers,
Alex
SUPERNOVA 1993J IN M81 (CHECK NAME!!)
(Discovery information from amateurs in Madrid...)
A. V. Filippenko, University of California at Berkeley, reports
that a CCD image of M81 obtained on March 30.1 UT by R. R. Treffers
and Y. Paik (also of Berkeley) with the 0.8-m reflector at Leuschner
Observatory confirms the presence of a new stellar object roughly
45" W and 160" S of the nucleus. The visual magnitude is approximately
11. Inspection of CCD spectra (range 356-731 nm) obtained on March 30.3
UT by M. Davis and D. Schlegel (also of Berkeley) with the Lick 3-m Shane
reflector reveals that the object is indeed a supernova. The continuum is
very blue and remarkably featureless. The only clear absorption lines
are narrow Na I D and Ca II H+K, undoubtedly of interstellar origin. It is
probable, but not yet certain, that the object is a Type II supernova
observed only a few days after the explosion. Note, however, that the
Type Ia SN 1991T exhibited a relatively featureless spectrum well before
maximum brightness (Filippenko et al., 1992, ApJL, L15). Depending on its
spectral type and extinction, SN 1993J may reach eighth magnitude during
the next two weeks. Aside from SN 1987A in the LMC, it is the brightest
supernova since SN 1972E in NGC 5253. Further observations throughout the
electromagnetic spectrum are urged.
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