Central Bureau for Astronomical Telegrams
IAUC 3359: SN IN NGC 4321; Notice
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Read IAUC 3360
Circular No. 3359
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 a further
communication (cf. IAUC 3353) from the ESA-SRC supernova team:
"New observations were made with the International Ultraviolet
Explorer on Apr. 27, May 1 and 7 at both short and long wavelengths.
The flux was found to decrease steadily with time. The variations
amounted to 1.64, 2.40 and 3.17 magnitudes in the integrated band
1160-1900 A and to 0.81, 1.30 and 1.91 magnitudes in the long
wavelength band 1900-3300 A. The visual magnitude was measured to be
12.39, 12.42 and 12.66 on the three days; the corresponding color
temperatures between 1565 and 5500 A were found to be 8900, 8100
and 7400 K. The C IV 1550 A line has developed a broad intrinsic
emission superimposed on the P-Cyg profile. By using all available
spectra, the expansion velocity has been estimated to be 3900 +/- 600
km/s. In addition to several weaker lines, prominent emissions of
N IV 1488 A, N III 1750 A and possibly C III 1909 A have been identified.
The measured line intensities are consistent with an abundance
ratio N/C = 10 and an electron density of the order of 10**11
cm**-3. The distance estimate has been revised to give a value D =
12 Mpc with a possible uncertainty of ~ 30 percent. Further
scheduled observations will permit an improved determination of D.
Coordinated ground-based optical and radio observations, as well
as satellite x-ray measurements, are either in progress or scheduled
for the near future."
K. Kaila, Vantaa, Finland, reports a prediscovery observation
of the supernova on a photograph obtained on Apr. 15.9 UT. On the
Kodak 103a-O emulsion 20-min exposure with a 20-cm f/8 reflector
the supernova appears at magnitude 11-12, slightly fainter than the
nucleus of the galaxy. The limiting magnitude of the exposure ~ 14
Further photoelectric observations by R. E. Zissell, Williston
Observatory: May 1.10 UT, V = 12.09; 3.10, 12.42.
NOTICE TO CONTRIBUTORS
Further to the note on IAUC 3355, we point out that short
messages for the Central Bureau can be telephoned to 617-864-5758,
which will record messages of up to 30-s duration. It would be
helpful if longer messages were sent by telex/TWX or telegram/cablegram
to TWX 710-320-6842 ASTROGRAM CAM; or even by mail.
1979 May 11 (3359) Brian G. Marsden
Read IAUC 3360
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