THE ASTRONOMER Electronic Circular No 510       1991 Apr 16 20.35UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP, England. Telephone:  (0256)471074 Int:+44256471074
Telex: 9312111261 Answerback: TA G                     JANET BOXES:
GMH at UK.AC.CAM.ASTRONOMY.STARLINK or GUYH at UK.AC.SUSSEX.CLUSTER
TELECOM GOLD: 10074:MIK2885                       PRESTEL 256471074
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SUPERNOVA 1991T IN NGC 4527
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 non-
photometric 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) 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.
IAUC 5239
Editor: The initial alert was received from Rob McNaught on Apr 15
and relayed by cable. Denis Buczynski responded with photographic
confirmation the same day. Mirko Villi's observation represents
the *first supernova discovery,* pre-announcement, made by a member
of UK Nova/Supernova Patrol since the programme's formation.
DWARF NOVA IN OPHIUCHUS
F. M. Bateson, Variable Star Section, Royal Astronomical Society of
New Zealand, reported (via A. C. Gilmore, Mt. John University
Observatory) the discovery on Apr. 11.62 UT of a possible nova of
mag about 10 by P. Camilleri, Cobram, Victoria. A measurement by P.
M. Kilmartin of a 0.15-m astrograph film taken by Gilmore on Apr.
14.72 yields the following accurate position:  R.A. = 17h17m14s.01,
Decl. = -26 43'28".8 (equinox 1950.0).  M. Wagner, Ohio State
University and Lowell Observatory, reports that his examination of
a spectrogram obtained Apr. 14 UT by D. Hunter reveals strong and
broad H-alpha absorption characteristic of a dwarf nova at maximum;
there were two bright objects in the spectrograph's field-of-view,
this object being the brighter one.  Available magnitude estimates,
visual unless otherwise noted:  Mar. 23, [12 (Camilleri;
photographic); Apr. 12.55, 10.7: (D. A. J. Seargent, The Entrance,
N.S.W.); 13.46 UT, 10.5 (A. Jones and D. Lester, Nelson, N.Z.);
13.55, 10.5 (P. Williams, Heathcote, N.S.W.); 13.56, 10.5
(Seargent); 15.46, 9.9 (Jones); 15.56, 11.0 (Seargent).
IAUC 5238
Guy M Hurst