Central Bureau for Astronomical Telegrams
IAUC 3353: SN IN NGC 4321; NOTICE TO SUBSCRIBERS
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Circular No. 3353
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-864-5758
SUPERNOVA IN NGC 4321
N. Panagia, European Space Agency, Villafranca, telexes the
following communication from the ESA-SRC team for observing supernovae
with the International Ultraviolet Explorer: "Observations of
the supernova in NGC 4321 were made on Apr. 22 and repeated on Apr.
24, covering the full range 1160-3200 A. The measured position is
offset by 55".8 east and 86".9 south relative to the nucleus of the
galaxy. At both epochs the spectrum is characterized by a relatively
smooth continuum on which several lines are superimposed.
The main features that are believed to originate in the supernova
envelope are identified as C IV 1550 A, SI IV 1398 A and N V 1240 A.
They display P-Cyg-like profiles. A preliminary examination of
these indicates an expansion velocity of ~ 3000 km/s. In addition,
interstellar absorption lines of Mg II, Al III, O I, C II, Si II
and S II have also been identified. They are broader than the
instrumental resolution, indicating that they originate in both our
Galaxy and the parent galaxy. The average ultraviolet flux has
been found to have decreased by a factor of 0.74 between the two
epochs. The visual magnitude has also been measured by means of
the fine-error-sensor on IUE to be 12.20 on Apr. 22 and 12.25 on
Apr. 24. The color temperature between 1565 and 5500 A has been
estimated to be 11 100 K on Apr. 22 and 10 700 K on Apr. 24. By
applying the Baade-Wesselink method the distance to NGC 4321 is
found to be 20.5 Mpc. Therefore the radius and the total luminosity
of the supernova on Apr. 22 are estimated to be 1.6 x 10**15 cm
and 2.7 x 10**43 erg/s, respectively."
Photoelectric observation by R. E. Zissell, Williston Observatory:
Apr. 25.10 UT, V = 12.16. Visual observations by K. Locher,
Grut, Switzerland: Apr. 22.08, 11.8; 24.83, 12.0 (comparison stars
USNO 11101 and 11292, V = 10.90 and 12.02, respectively).
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1979 May 1 (3353) Brian G. Marsden
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