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IAUC 7296: C/1999 U3; 1999em

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                                                  Circular No. 7296
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 U3 (LINEAR)
     Preliminary parabolic orbital elements by the undersigned from
the observations on IAUC 7295:

     T = 1999 Sept.12.27 TT           Peri. =  58.82
                                      Node  = 324.90    2000.0
     q = 1.8098 AU                    Incl. =  20.58

1999 TT     R. A. (2000) Decl.   Delta     r    Elong. Phase    m1
Oct. 29     3 27.34   +58 10.6   1.085   1.905  132.8   22.5   16.5
Nov.  3     3 26.69   +58 32.3   1.091   1.926  135.1   21.3   16.5
      8     3 25.42   +58 40.2   1.101   1.948  137.2   20.2   16.6
     13     3 23.81   +58 34.3   1.114   1.972  139.1   19.2   16.7
     18     3 22.13   +58 15.5   1.132   1.998  140.8   18.2   16.8


SUPERNOVA 1999em IN NGC 1637
     S. Jha, P. Challis, P. Garnavich, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, report that a spectrum was
obtained on Oct. 30.34 UT by M. Calkins with the F. L. Whipple
Observatory (FLWO) 1.5-m telescope (+ FAST spectrograph), revealing
SN 1999em to be a type-II event at an early epoch.  The spectrum
exhibits a very blue continuum with P-Cyg profiles of H-alpha,
H-beta, H-gamma, and He I (rest 587.6 nm).  The supernova
photospheric expansion velocity, measured using the H-beta
absorption trough, is 10 300 km/s, adopting the NASA/IPAC
Extragalactic Databse recession velocity (717 km/s) for NGC 1637.
The spectrum also shows narrow interstellar Na I D (EW = 0.17 nm)
at the redshift of NGC 1637, implying that the supernova may be
partly obscured by dust.  Concurrent images of SN 1999em, taken by
K. Stanek with the FLWO 1.2-m telescope, yield a precise position
for the supernova of R.A. = 4h41m27s.05, Decl. = -2o51'45".8
(equinox 2000.0, uncertainty +/- 0".3), which is 15".4 west and
17".0 south (not north as reported on IAUC 7294) of the host galaxy
nucleus.
     J. S. Deng, H. L. Cao, D. W. Xu, Y. Lu, H. B. Li, Y. L. Qiu,
and J. Y. Hu, Beijing Astronomical Observatory (BAO), report that a
low-dispersion spectrum (range 380-740 nm) of SN 1999em was
obtained on Oct. 29.7 UT with the BAO 2-m telescope, showing the
supernova to be a young type-II event.  The spectrum exhibits a
very blue continnum with broad emission features of H-alpha, H-beta,
H-gamma, H-delta, and Na I D.  The narrow Na I D absorption line
indicates a recession velocity for NGC 1637 of 710 km/s.

                      (C) Copyright 1999 CBAT
1999 October 31                (7296)            Daniel W. E. Green

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