Central Bureau for Astronomical Telegrams
IAUC 7637: 2001cg; 2001ch
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Circular No. 7637
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 2001cg IN IC 3900
W. D. Li, University of California at Berkeley, reports the
discovery by LOTOSS (cf. IAUC 7514) of an apparent supernova (mag
about 17.8) in unfiltered images taken with the Katzman Automatic
Imaging Telescope (KAIT) on May 28.2 and 29.2 UT. The new object
is located at R.A. = 12h55m40s.87, Decl. = +27o15'03".9 (equinox
2000.0), which is 6".0 west and 1".5 north of the nucleus of IC
3900. A KAIT image taken on May 15.2 showed nothing at this
position (limiting mag about 19.0).
A. V. Filippenko and R. Chornock, University of California at
Berkeley, write: "Inspection of a CCD spectrum (range 390-1000 nm),
obtained on May 29 UT with the Keck-II 10-m reflector, reveals that
SN 2001cg is a type-Ia supernova. The spectrum most closely
resembles those of subluminous members of the class, like SN 1991bg
and SN 1998de (e.g., Modjaz et al. 2001, PASP 113, 308), roughly
1-2 weeks past maximum brightness; the absorption at Si II 580-nm
is unusually strong relative to the Si II 615-nm line. The host
galaxy (cz = 7100 km/s, from NED) appears to have a Hubble type of
E or S0, consistent with the preponderance of early-type hosts
among other subluminous type-Ia supernovae."
SUPERNOVA 2001ch IN MCG -01-54-16
Li also reports another LOTOSS discovery of a supernova on
unfiltered KAIT images taken on May 28.5 (mag about 16.7) and 29.5
UT (mag about 16.8). SN 2001ch is located at R.A. = 21h25m59s.19,
Decl. = -3 48'46".8 (equinox 2000.0), which is about 12" west and
14" south of the diffuse nucleus of MCG -01-54-16. A KAIT image
taken on 2000 Nov. 28.3 showed nothing at this position (limiting
mag about 19.0).
Filippenko and Chornock add that a CCD spectrum (range
390-1000 nm), obtained on May 29 UT with the Keck-II 10-m
reflector, reveals that SN 2001ch is a type-Ic supernova, just
beginning to enter the nebular phase (perhaps 1-2 months past
maximum brightness). The strength of [O I] 557.7-nm emission is
comparable to that of [O I] 630.0-nm, but still weak compared with
the Ca II near-infrared triplet. The O I 777.4-nm absorption line
is strong, while lines of He I are weak or absent. The object is
superposed on bright H II regions in the disk of the host galaxy,
whose recession velocity is 2930 km/s (from NED).
(C) Copyright 2001 CBAT
2001 May 29 (7637) Daniel W. E. Green
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