Supernova SN1991T Discovered in April of 1991

Discovery overview

Discovering party: Stephen Knight of Waterford, Maine
Official name: SN1991T
Category: Supernova
Subcategory: type I
Location: Galaxy NGC 4527

Official CBAT Report

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.

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