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IAUC 7150: Poss. SN IN NGC 3198; 1999bv

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                                                  Circular No. 7150
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)

     P. Garnavich, S. Jha, and R. Kirshner, Harvard-Smithsonian
Center for Astrophysics, report that spectra of the possible
supernova in NGC 3198 (cf. IAUC 7149) were obtained with the 1.5-m
Tillinghast telescope by M. Calkins on Apr. 21.2 UT.  The spectrum
is not clearly that of a supernova.  The continuum peaks broadly
around 500 nm and declines more quickly in the blue than toward the
red.  Balmer emission lines of H-alpha, H-beta, and H-gamma are
visible.  The H-alpha line has a narrow component sitting on a
broader base, with a full width at the continuum of 2000 km/s.  CCD
images obtained by W. Brown with the Fred L. Whipple Observatory
1.2-m telescope (at the same time as the spectra) give V = 18.5.
The object has not risen in brightness significantly over the six
days since discovery (IAUC 7149), as would be expected from a
supernova caught at an early stage.
     A. V. Filippenko and T. Matheson, University of California at
Berkeley, report:  "Inspection of a CCD spectrum (range 400-860 nm)
of the possible supernova in NGC 3198, obtained on Apr. 21 by P.
Guhathakurta and A. Szomoru (University of California at Santa
Cruz) with the 3-m Shane reflector at Lick Observatory, reveals
Balmer emission lines near the galaxy redshift (630 km/s).  The
lines are unresolved, or perhaps barely resolved (FWHM = 1000
km/s), in the low-resolution data.  If this object is a supernova,
it is very subluminous:  absolute magnitude about -12 at an assumed
distance of 9 Mpc.  This is much more powerful than an ordinary
nova, but within the range of some kinds of luminous blue variable
stars.  The exact nature of the object therefore remains ambiguous."

SUPERNOVA 1999bv IN MGC +10-25-14
     S. Jha, P. Garnavich, P. Challis, and R. Kirshner, Center for
Astrophysics, report that a spectrum of SN 1999bv, obtained by M.
Calkins on Apr. 21.5 UT with the F. L. Whipple Observatory (FLWO)
1.5-m telescope (+ FAST spectrograph), indicates that it is
probably a type-Ib/c supernova.  The spectrum exhibits a flat
continuum with broad (FWHM 10 000 km/s) emission features observed
at 667, 600, 475, and 402 nm.  This is generally similar to a
spectrum of the type-Ib/c SN 1988L when it was presumed to be a few
weeks after maximum light (Filippenko 1988, A.J. 96, 1941).  Narrow
H-alpha emission from the host galaxy yields a recession velocity
of 5510 km/s.  Concurrent images taken by W. Brown with the FLWO
1.2-m telescope (+ 4shooter) yield V = 18.6 for the supernova.  SN
1999bv is within the 2.5-sigma error box of GRB 990302 (BATSE
Trigger 7440).

                      (C) Copyright 1999 CBAT
1999 April 22                  (7150)            Daniel W. E. Green

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