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IAUC 5239: 1991T; 1991M

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                                                  Circular No. 5239
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

     E. Waagen, AAVSO, reports the discovery of a supernova by
Stephen Knight, Waterford, ME, in NGC 4527 (R.A. = 12h31m.6, Decl. =
+2 56', equinox 1950.0).  The object has been independently reported
by Robert O. Evans, Hazelbrook, N.S.W.; by M. Villi and G. Cortini,
Monte Colombo, Italy; and by Wayne Johnson, Anza, CA.  Visual
magnitude estimates:  Apr. 4.48 UT, [15 (Evans); 9.9, [15 (Villi and
Cortini); 13.17, 14 (Knight); 14.14, 13.6 (Knight); 15.6, 13 (Evans);
15.9, 13.0 (Villi and Cortini); 16.26, 13.5 (Johnson).  The
following position was measured by R. H. McNaught, Anglo-Australian
Observatory, from an Uppsala Southern Schmidt photo taken Apr. 15.5:
R.A. = 12h31m36s.91, Decl. = +2 56'28".3; offsets from the nucleus
are 25".7 east, 44".4 north.  A nearby star of mag about 16 is located
at R.A. = 12h31m42s.80, Decl. = +2 55'15".1.  J. Mueller, Palomar
Observatory, reports that an IVN (near-infrared) plate taken Apr. 10
with the Oschin Schmidt Telescope failed to show the supernova.
     E. Cappellaro, Padua Observatory, reports:  "G. Cutispoto (
Catania Observatory) obtained the following photometry under
nonphotometric conditions with the European Southern Observatory 1-m
telescope on Apr. 16.35 UT, V = 12.9, B-V = +0.1, U-B = -0.6, V-R =
+0.1.  A CCD spectrogram (range 350-830 nm) obtained by F. La Franca
(Padua University) and C. Goldschmidt (Edinburgh University; correction
to IAUC 5237, line 5 from bottom) at the ESO 2.2-m telescope
shows a blue, almost featureless continuum, with only two strong
lines having P-Cyg profile and absorption measured at 424 and 494 nm.
The bright magnitude, the blue color, and the lack of the Balmer
lines seem to indicate a type-I SN before maximum."  R. P. Kirshner,
Harvard-Smithsonian Center for Astrophysics, notes that the feature
from 424 to 494 nm is also present on a spectrum obtained on Apr.
16.18 UT by J. Peters with the 1.5-m reflector at the Whipple
Observatory. The spectrum is highly unusual but is certainly not that of
a classic type-II or type-Ia supernova near maximum; it could well
be that of a type-I supernova in its very early stages.

     McNaught reports a position of SN 1991M (cf. IAUC 5207) from a
U.K. Schmidt J plate taken Apr. 9 by P. McKenzie when the supernova
was at mag about 15:  R.A. = 15h56m19s.20, Decl. = +17 35'59".3
(equinox 1950.0).  A star of mag 17 is located at R.A. =
15h56m18s.40, Decl. = +17 36'58".8.

1991 April 16                  (5239)             Daniel W. E. Green

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