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IAUC 7152: C/1999 H3; 1999bw

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                                                  Circular No. 7152
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)


COMET C/1999 H3 (LINEAR)
     Additional observations are available on MPEC 1999-H29, from
whence the following preliminary orbital elements are taken:

     T = 1999 Aug. 17.907 TT          Peri. = 101.801
                                      Node  = 332.669   2000.0
     q = 3.50186 AU                   Incl. = 115.832

1999 TT     R. A. (2000) Decl.   Delta     r    Elong. Phase    m1
Apr. 22    19 17.68   +44 02.9   3.548   3.665   88.6   15.9   15.4
     27    19 11.41   +45 54.0   3.491   3.651   91.1   16.0   15.3
May   2    19 03.83   +47 44.4   3.439   3.639   93.3   16.0   15.3
      7    18 54.81   +49 32.5   3.392   3.627   95.3   16.1   15.2
     12    18 44.22   +51 16.3   3.351   3.615   96.9   16.1   15.2
     17    18 31.94   +52 53.5   3.317   3.604   98.3   16.1   15.2
     22    18 17.96   +54 21.5   3.290   3.594   99.2   16.1   15.1
     27    18 02.30   +55 37.9   3.270   3.584   99.8   16.2   15.1
June  1    17 45.15   +56 40.3   3.257   3.574   99.9   16.2   15.1
      6    17 26.79   +57 26.4   3.251   3.565   99.7   16.3   15.1
     11    17 07.66   +57 55.0   3.253   3.557   99.0   16.4   15.1


SUPERNOVA 1999bw IN NGC 3198
     A. V. Filippenko, W. D. Li, and M. Modjaz, University of
California at Berkeley, write:  "A CCD spectrum (range 450-710 nm,
resolution 0.7 nm) of the reported possible supernova in NGC 3198
(cf. IAUC 7149, 7150), obtained on Apr. 24 with the 3-m Shane
reflector at Lick Observatory looks very similar to that of the
type-IIn SN 1997bs in NGC 3627 (cf. IAUC 6627).  The narrow Balmer
emission lines (FWHM about 600 km/s) have a broader base with FWZI
roughly 3000 km/s, and there is a hint of weak Fe II emission near
520 nm.  Like SN 1999bw, SN 1997bs was quite subluminous (M about
-13).  Another example of an object having a similar spectrum is SN
1999Z (cf. IAUC 7107), but it was much more luminous.  The type-IIn
subclass clearly spans a very broad range of properties, as was
already known to some extent (e.g., Filippenko 1997, Ann. Rev.
Astron. Astrophys. 35, 309).  It remains to be seen whether the
explosion mechanism is core collapse in all of these objects;
perhaps in some cases the star is not fully destroyed (e.g., SN
1961V; Filippenko et al. 1995, A.J. 110, 2261)."

                      (C) Copyright 1999 CBAT
1999 April 25                  (7152)            Daniel W. E. Green

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