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IAUC 7183: 1999br; C/1999 H1

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                                                  Circular No. 7183
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
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SUPERNOVA 1999br IN NGC 4900
     F. Patat, European Southern Observatory (ESO); S. Benetti,
Telescopio Nazionale Galileo; and E. Cappellaro, L. Rizzi, and M.
Turatto, Padova, write:  "We have observed SN 1999br (cf. IAUC
7141) with the ESO 3.6-m telescope (+ EFOSC2) on May 21.02 UT at La
Silla.  A full reduction of the CCD spectrogram (range 330-1020 nm,
resolution 2.0 nm) shows that this object
(http://sc6.sc.eso.org/~fpatat/sn99br.gif) is remarkably similar to
SN 1994N (IAUC 5987) at a comparable phase.  The dominant feature
is H-alpha, blended with Ba II 649.7-nm, as shown by the
subluminous SN 1997D (Turatto et al. 1998, Ap.J. 498, L129).  The
other two lines, at 585.4 and 614.2 nm, of the same multiplet 2 of
Ba II are visible (the former blended with Na I D).  The low
expansion velocities allow us to recognize a multitude of other
lines, all accompanied by the typical P-Cyg profile.  The most
prominent features are identified as H, Na I, Ca II, Ba II, Sc II,
Fe I, and Fe II.  The expansion velocity deduced from the
absorption minimum of H-alpha is 3500 km/s, which is a very low
value if compared with 'normal' supernovae of type II.  In analogy
to the more extreme SN 1997D, the small kinetic energy, the low
temperature, and the faint magnitude (cf. Filippenko 1999, IAUC
7143) indicate that a small mass of 56Ni has been ejected by SN
1999br.  Further observations during the radioactive decay tail are
needed to prove this suggestion."

COMET C/1999 H1 (LEE)
     E. A. Bergin, Harvard-Smithsonian Center for Astrophysics
(CfA); D. A. Neufeld, Johns Hopkins University; and J. R. Stauffer,
S. C. Kleiner, Z. Wang, R. Plume, and G. J. Melnick, CfA, write:
"The 1(10)-1(01) transition of water vapor near 557 GHz has been
detected toward comet C/1999 H1 by the Submillimeter Wave Astronomy
Satellite (SWAS) at a signal-to-noise ratio of 60.  Over the period
May 19.01-23.69 UT, the average integrated antenna temperature was
1.08 +/- 0.02 K km/s within a 3'.3 x 4'.5 (FWHM) elliptical beam.
For a Haser model with an assumed water lifetime of 7.3 x 10E4 s,
the inferred production rate for ortho-water is 1.0 x 10E29 sE-1,
corresponding to a total water-production rate of 1.3 x 10E29 sE-1
if the ortho-to-para ratio is 3.  The observed line width of 1.48
+/- 0.03 km/s FWHM is broader than the instrumental profile and
suggests an intrinsic line width of about 1.0 km/s FWHM.  The data,
taken during a portion of every 97-min spacecraft orbit over a
4.68-day period, provide no obvious evidence for variability."

                      (C) Copyright 1999 CBAT
1999 May 28                    (7183)            Daniel W. E. Green

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