Central Bureau for Astronomical Telegrams
IAUC 6914: 1998cf; Var STAR NEAR NGC 4013?
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Circular No. 6914
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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SUPERNOVA 1998cf IN NGC 3504
Apparently independent discovery reports of a supernova in NGC
3504 have been received (both from observations made at Mauna Kea)
from Eric Emsellem, Observatoire de Lyon, via CCD images obtained
on Mar. 31.272 UT at the Canada-France-Hawaii Telescope (CFHT), and
from Geoffrey Clayton and Karl Gordon, Louisiana State University,
via separate J, H, and K images taken on Mar. 2.38 with the NASA
Infrared Telescope Facility. Emsellem notes that the star is
located at R.A. = 11h03m11s.21, Decl. = +27o58'21".0 (equinox
2000.0), which is 0".6 east and 5".3 south of the center of NGC
3504. Clayton provides position end figures 12s.01, 13".2.
Emsellem calculates that the object had a flux of 6.7 x 10E-16 erg
sE-1 cmE-2 AE-1 at 900 nm on Mar. 31, and he roughly estimates I
about 15. Clayton reports J = 14.5, K = 12.8 for Mar. 2. The star
was not present in January, when a K observation of NGC 3504 was
obtained with the CFHT Adaptive Optics Bonnette, and it is not
present in other archival images, including JHK images taken in May
1996 at the Kitt Peak 2.1-m telescope (Elmegreen et al. 1997, A.J.
114, 1850) and in Dec. 1997 at Mt. Laguna Observatory. Note that
this galaxy contains an apparent double nucleus, as well. P.
Garnavich, Harvard-Smithsonian Center for Astrophysics, reports
that inspection of a spectrum (range 840-900 nm) taken with the
CFHT integral spectrograph OASIS on Mar. 31.312 (and provided by
Emsellem) reveals what appears to be a broad Ca II P-Cyg profile
characteristic of a supernova.
VARIABLE STAR NEAR NGC 4013?
D. Bettoni, Osservatorio Astronomico di Padova, reports that
further examination of 12 Schmidt plates of NGC 4013 in the Asiago
archive taken during 1983-1991 shows that the star noted on IAUC
6911 is present with no appreciable difference in brightness from
the 1998 images. The star also appears at similar brightness on a
May 1938 blue photograph present in the Carnegie Atlas of Galaxies
(Sandage and Bedke 1994). B. F. Madore, NASA/IPAC Extragalactic
Database, informed Bettoni that the NED has more than 100 galaxies
(including NGC 4013) that are displayed with all stars subtracted
from the field, without obvious mention of this fact. Furthermore,
the Tully et al. images were converted to a logarithmic scale,
whereby brighter objects may be depicted as fainter than on the
original frames. Thus, though this star may be slightly variable,
it does not appear to have an amplitude anywhere near 5 magnitudes.
(C) Copyright 1998 CBAT
1998 May 22 (6914) Daniel W. E. Green
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