Central Bureau for Astronomical Telegrams
IAUC 7761: 2001gd; 2001gb, 2001gc
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Circular No. 7761
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 2001gd IN NGC 5033
S. Nakano, Sumoto, Japan, reports the discovery of an apparent
supernova (mag 16.5) by K. Itagaki, Yamagata, Japan, on CCD images
taken with a 0.60-m f/6.0 reflector on Nov. 24.820 UT. Itagaki
remarked that the new object is located about 3' north-northwest of
the center of NGC 5033, and he added that nothing was visible at
this position on a CCD frame taken on May 29 (limiting mag 19).
Nakano forwards the following precise position for SN 2001gd, which
is the average of measurements by Y. Kushida from two CCD images
taken by R. Kushida, Yatugatake South Base Observatory, with a
0.40-m f/6.3 Schmidt-Cassegrain reflector (+ CCD) in bright
twilight on Nov. 24.851 (when the new object was at mag 17.5) and
25.802 (mag 16.2): R.A. = 13h13m23s.89, Decl. = +36o38'17".7
(equinox 2000.0), which is 3'23" in p.a. 347o from the nucleus of
NGC 5033. R. Kushida adds that there is no star visible at this
location on her earlier frames taken from 1996 to Apr. 2001. SNe
1950C and 1985L appeared in this galaxy. A. Dimai, Cortina
d'Ampezzo, Italy, reports his independent discovery of SN 2001gd
(mag about 16.4) on images taken in the course of the CROSS
program (cf. IAUC 7373) with a 0.51-m telescope on Nov. 25.21 and
26.21; his position end figures for the new object are 23s.92,
18".2, which is about 52" west and 161" north of the nucleus of NGC
5033. A CROSS image taken on May 8 showed nothing at this position
(limiting mag about 18.5), and SN 2001gd does not appear on Palomar
Sky Survey red and blue plates.
SUPERNOVAE 2001gb AND 2001gc
T. Matheson, S. Jha, P. Challis, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, report that spectra (range
370-750 nm) were obtained of SN 2001gb (cf. IAUC 7758) and SN
2001gc (cf. IAUC 7759) on Nov. 22.49 and 22.25 UT by M. Calkins
with the Mt. Hopkins 1.5-m telescope (+ FAST spectrograph), showing
them both to be type-Ia supernovae. Adopting the NASA/IPAC
Extragalactic Database (NED) recession velocity of 7714 km/s for
the host galaxy of SN 2001gb, the supernova expansion velocity is
about 11 300 km/s for Si II (rest 635.5 nm); the spectral-feature
age of SN 2001gb (Riess et al. 1997, A.J. 114, 722) is 0 +/- 2 days
after maximum light. Adopting the NED recession velocity of 5783
km/s for the host galaxy, the expansion velocity of SN 2001gc is
about 16 600 km/s for Si II (rest 635.5 nm); this expansion
velocity implies an age of approximately 2 weeks before maximum,
based upon comparison with values presented by Jha et al. (1999,
Ap.J. Supp. 125, 73).
(C) Copyright 2001 CBAT
2001 November 26 (7761) Daniel W. E. Green
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