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THE ASTRONOMER Electronic Circular No 1655      2001 Jly 16 18.01UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK             GMH at AST.STAR.RL.AC.UK
WORLD WIDE WEB                    http://www.demon.co.uk/astronomer
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SUPERNOVA 2001dc IN NGC 5777 (Q2001/223)
As long ago as 2001 June 1, Mark Armstrong reported a very faint
object in NGC 5777 suspected of being a supernova. Although first
detected on May 30/31, it was also possibly present but fainter
on May 21/22. Lack of significant magnitude variation and its
faintness for supernova events in this galaxy, given its distance,
made it necessary to pursue a spectrum and Mark must be
congratulated not only on the discovery but for working tirelessly
in his efforts to persuade professionals to assist. The following
IAUC announcement has now appeared:

Guy M. Hurst, Basingstoke, England, reports the discovery by Mark
Armstrong (Rolvenden, Kent) of an apparent supernova at R.A. =
14h51m16s.15, Decl. = +58o59'02".8 (2000; average from three CCD
images obtained with a 0.35-m reflector), said to be 26" west and
28" north of the centre of NGC 5777.  Reported magnitudes for
SN 2001dc [unfiltered CCD data unless otherwise noted, and from
Armstrong unless otherwise noted; '--' means not visible; JKT =
Jacobus Kapteyn Telescope (via P. Meikle, Imperial College;
uncertainty +/- 0.1 mag; June 22 data obtained by D. Bramich, R.
Corradi, and P. Erwin)]:  1995 Apr. 4 UT, [20.8 (Palomar Sky Survey
red plate); Apr. 18, [21 (JKT I-band images); Apr. 24, [22.5 (PSS
blue plate); 1997 Apr. 18, -- (PSS infrared plate); 2000 Dec. 3,
--; 2001 Apr. 12, --; May 12, --; 21.977, 18.6 (prediscovery);
30.958, 18.5 (discovery; limiting mag 19.3); June 1.021, 18.5;
2.985, 18.3 (T. Boles, Coddenham, England); 22.93, B = 21.11, V =
19.83, R = 19.15, I = 18.46 (JKT).  M. Irwin (Cambridge
Astronomical Survey Unit) adds that a June 22.93 JKT image yields
position end figures 16s.21, 03".0 for SN 2001dc, which is about
14" west and 22" north of the nucleus of NGC 5777.  Meikle notes
that JKT data show that the change in brightness of SN 2001dc from
June 22.93 to July 4.92 was < 0.3 mag in B, 0.1 mag in V, and 0.05
mag in R (all 1-sigma confidence); there was marginal evidence of a
brightening in I (by -0.12 +/- 0.04).  Meikle and A. Fassia add: "A
spectrum obtained on July 10.97 at the Isaac Newton Telescope shows
a strong but quite narrow P-Cyg profile in H-alpha.  Together with
the lack of significant decline in optical brightness between June
22 and July 4, we conclude that this is a type-IIp supernova, still
in its plateau phase during this period.  Other lines identified
include Fe II (501.8 and 516.9 nm), Na I D, and the Ca II infrared
triplet.  A blueshifted absorption feature due to H-beta may also
be present, but it is close to the blue limit of the spectrum (482
nm).  The trough of the H-alpha profile is blueshifted by about
2400 km/s with respect to the emission peak.  The corresponding
figure for Na I D is 2300 km/s.  The supernova appears to be an
unusually low-energy event.  Assuming negligible extinction, the
V-band magnitude corresponds to M_V = -12.6 (adopting 32.4 as the
distance modulus for NGC 5777), compared with more typical values
(M_V = -15 to -16) for a type-IIp event during its plateau phase
(Patat et al. 1994, A.Ap. 282, 731).  Moreover, the velocity seen
in H-alpha is only about half of that normally observed during this
era.  Further photometric and spectroscopic observations are
strongly encouraged.  Of particular interest is the size of the
decline immediately following the end of the plateau phase."
IAUC 7662

Guy M Hurst