Central Bureau for Astronomical Telegrams
IAUC 3361: SN IN NGC 4321; Corr
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Circular No. 3361
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
L. Rosino, Asiago Astrophysical Observatory, reports that this
object (cf. IAUC 3348) is being followed at Asiago by F. Ciatti, P
Rafanelli, S. Ortolani and himself. The supernova appeared close
to a nebulous knot, very likely an H II region. The slow decline
of 0.5 magnitude from Apr. 20 to May 3 and the observed colors are
consistent with a type II supernova discovered around maximum. The
slow expansion velocity indicated by IUE observations (IAUC 3353,
3359) can explain the peculiar behavior of the spectrum in which
the typical type-II features have not yet (up to May 6) developed
as expected. Further observations are planned, in cooperation with
measurements at other frequencies.
G. de Vaucouleurs, University of Texas, reports the following
definitive reductions of photoelectric and visual observations by
B. Beardsley, R. Buta, B. Smith and himself with the 75-, 90- and
205-cm reflectors at the McDonald Observatory:
1979 UT mv V B-V U-B
Apr. 23.24 12.18 12.19 +0.18 -0.67
24.23 12.3l 12.11 +0.19 -0.60
25.24 12.15
26.17 12.4:
27.27 12.24 12.34 +0.27 -0.57
28.19 12.36 +0.26 -0.54
29.15 12.37 +0.29 -0.51
30.14 12.37 +0.27 -0.46
He adds that the rates of decline (0.034 magnitude per day) and
reddening (0.015 and 0.030 magnitude per day) and spectrum are
consistent with type II but that the absolute magnitude M_B = -19.0
rivals type I if the galaxy is at the distance of the Virgo cluster.
Abnormally high luminosity is confirmed by direct comparison of the
apparent magnitude of this supernova with the apparent magnitudes
of other type-II supernovae, typically 14-15 at maximum, in other
Virgo spirals.
CORRIGENDUM
On IAUC 3358, item on SS 433, the reference on lines 19-20
should read Fabian and Rees 1979, rather than 1978.
1979 May 17 (3361) Brian G. Marsden
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