Central Bureau for Astronomical Telegrams
IAUC 8456: C/2004 V6-V13; 2004gt, 2004gv
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Circular No. 8456
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)
COMETS C/2004 V6-V13
Further to IAUC 8455, all the SOHO comets announced there were
Kreutz sungrazers except for C/2004 V9 and C/2004 V10, which belong
to the Marsden group. Marsden adds (MPEC 2004-X73) that C/2004 V9
may be identical with C/1999 J6, with a 5.49-yr period. Also, S.
Hoenig reports that he learned of the appearance of C/2004 V13 on
the C3 images from J. Sachs, who evidently was the first to notice
it.
SUPERNOVAE 2004gt AND 2004gv
K. Kinugasa and H. Kawakita, Gunma Astronomical Observatory;
and H. Yamaoka, Kyushu University, report that a low-resolution
spectrogram (range 390-750 nm) of SN 2004gt, taken on Dec. 17.8 UT
with the Gunma 0.65-m telescope (+ GCS), shows He I 587.6-nm
absorption prominently, suggesting that it is a type-Ib supernova
near maximum light. A W-shaped absorption around 500 nm is also
prominent. Adopting the NED recession velocity (1648 km/s), the
expansion velocity (deduced from the absorption minimum of He I) is
about 12000 km/s.
M. Ganeshalingam, B. J. Swift, and A. V. Filippenko,
University of California, Berkeley, report that inspection of CCD
spectra (range 330-1060 nm), obtained on Dec. 18 UT with the Shane
3-m reflector at Lick Observatory, reveals that SN 2004gt (IAUC
8454) is of type Ib/Ic, not far from maximum brightness. The He
I/Na I absorption near 570 nm is strong, but the only clear He I
line is an absorption trough near 1040 nm attributed to He I
1083-nm. Other type-Ic supernovae have shown evidence for a small
quantity of He (e.g., SN 1994I; Filippenko et al. 1995, Ap.J. 450,
L11). The substantial strength of the O I 777.4-nm trough in SN
2004gt is more consistent with a type-Ic than a type-Ib
classification (Matheson et al. 2001, A.J. 121, 1648), though type
Ib is still a possibility. It is difficult to distinguish
unambiguously between the Ib and Ic subclasses with a single
optical spectrum obtained near maximum brightness; further
observations are thus encouraged.
Ganeshalingam, Swift, F. J. D. Serduke, and Filippenko add
that inspection of CCD spectra obtained on Dec. 17 UT reveals that
SN 2004gv (IAUC 8454) is probably of type Ib/Ic, not far from
maximum brightness. The O I 777.4-nm line is weak, perhaps
suggesting that the supernova is of type Ib rather than Ic
(Matheson et al. 2001, A.J. 121, 1648). SN 2004gv appears to be
associated with young stars in the outskirts of the type-S0 host
galaxy, as evidenced by narrow emission lines typical of H II
regions.
(C) Copyright 2004 CBAT
2004 December 18 (8456) Daniel W. E. Green
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