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IAUC 6005: 1994S; 1993J

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                                                  Circular No. 6005
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505

     B. Skiff, Lowell Observatory, reports the visual discovery on
June 4 UT by Larry Mitchell, Houston, TX, of a supernova (mag 14.5)
located 30" west of the center of NGC 4495 (R.A. = 12h28m.8, Decl.
= +29o26', equinox 1950.0).  A June 9 CCD observation by Skiff with
the Lowell 1.1-m Hall telescope reveals the new object (V about 14)
about 20" from the galaxy's center in p.a. 250o, situated along an
outlying spiral arm of fairly low surface brightness.  Skiff notes
that, on Palomar sky survey photographs, there is also a red star
of mag B about 17-18 (R about 15-16) located 30" from the galaxy's
center toward p.a. 290o.
     J. C. Wheeler, D. Wills, and A. Clocchiatti, University of
Texas, report:  "A reduced spectrum (range 507-787 nm, resolution
1.2 nm, uncalibrated in flux), obtained on June 9.24 UT with the
McDonald 2.7-m telescope, shows the object (offset 13" west and 7"
south from the galaxy's center) to be a type-Ia supernova close to
maximum light.  The expansion velocity determined from the Si II
and S II absorptions is about 11000 km/s.  The redshift of the
galaxy measured from H-alpha emission is z = 0.0152.  Narrow Na D
lines in absorption at this redshift (EW = 0.123 nm) suggest the
foreground absorption is at least 0.8 mag in V."

     Clocchiatti and Wheeler also communicate: "Spectra of SN 1993J
from McDonald Observatory show that emission in H-alpha is
increasing.  By May 4, the flux in H-alpha was greater than in the
[O I] or Ca II] doublets.  By June 4, the peak intensity in H-alpha
was larger than for Ca II] at 729.1 and 732.4 nm, and, pending
calibration through photometry, the total flux in H-alpha was larger
than for May 4--implying that the supernova could be brightening in
Rc.  The line can be approximated by a flat-topped profile, centered
at 656.4 nm, with FWHM = 36.5 nm.  The observations suggest that
H-alpha forms in an expanding shell heated by a mechanism other than
radioactive decay, probably interaction with circumstellar matter.
The presence of H-alpha at late times is a distinctive feature that
differentiates SN 1993J from the prior transition event SN 1987K.
Observations over all wavelengths are urged before M81 becomes

1994 June 9                    (6005)            Daniel W. E. Green

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