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IAUC 7464: 2000cv; C/1999 S4

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                                                  Circular No. 7464
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)

SUPERNOVA 2000cv IN PGC 39222
     S. Jha, P. Challis, and R. Kirshner, Harvard-Smithsonian
Center for Astrophysics, report:  "A spectrum (range 550-750 nm) of
SN 2000cv, obtained by P. Berlind on July 24.15 UT with the F. L.
Whipple Observatory 1.5-m telescope (+ FAST spectrograph), shows
that it is likely a type-Ia supernova near maximum light.  Though
the wavelength range is limited, the spectrum shows broad
absorption features at 581 and 627 nm that we identify as Si II.
Cross-correlation of the host-galaxy spectrum with an emission-line
template yields a recession velocity of 6120 +/- 20 km/s.  The
expansion velocity of the supernova, measured with the Si II (rest
635.5 nm) profile, is 10 200 km/s."

     C. Lisse and D. Christian, Space Telescope Science Institute;
K. Dennerl, Max-Planck-Institut fur Extraterrestrische Physik; F.
Marshall, R. Mushotzky, R. Petre, and S. Snowden, NASA/Goddard
Space Flight Center; H. Weaver, Johns Hopkins University; B.
Stroozas, University of California; and S. Wolk, Harvard-
Smithsonian Center for Astrophysics, report the first detection of
x-ray line emission due to charge exchange between cometary
neutrals and solar-wind minor ions using Chandra and EUVE:  "Using
a 960-s ACIS-S observation of comet C/1999 S4 on July 14.20 UT, the
comet was detected with a rate in the S3 chip of 0.3 count/s, with
a total integral flux of 8 x 10**-13 erg s**-1 cm**-2 over 0.2-0.7
keV and a total x-ray luminosity of 6 x 10**14 erg/s.  The ACIS-S
spectrum showed a strong line at 570 eV detected at greater than 10
sigma, due to charge exchange to O VII.  Other lines due to charge
exchange are also present (e.g., N VI, N VII at 300-500 eV, O VIII
at 650 eV) at lower S/N.  The best fit to the preliminary spectrum
is the MEKAL multiple-line emission model (Mewe et al. 1986, A.Ap.
Suppl. 65, 511) using solar elemental abundances with enhanced
oxygen and nitrogen abundances, and a plasma temperature of 0.17
keV.  The EUVE Lexan B count rate at July 14.21 was 0.06 count/s in
5400 s, for an equivalent luminosity of 1 x 10**15 erg/s at 0.16
keV.  The observed emission was found to be highly time variable on
the order of hours, enhanced by a strong solar flare propagating
radially from the sun."
     Visual m_1 estimates:  July 20.91 UT, 7.0 (N. Biver, Ablis,
France, 7x50 binoculars); 21.86, 6.7 (D. V. Fedotov, Kharkov,
Ukraine, 7x50 binoculars); 23.87, 6.2 (J. Kysely, Vlasim, Czech
Republic, 7x50 binoculars); 24.92, 6.2 (A. Baransky, Kiev, Ukraine,
12x80 binoculars).

                      (C) Copyright 2000 CBAT
2000 July 25                   (7464)            Daniel W. E. Green

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