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IAUC 7499: P/2000 S2; 2000dn; C/1999 Y1

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IAUC number 

                                                  Circular No. 7499
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)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


COMET P/2000 S2 (SHOEMAKER-LINEAR)
     S. Nakano, Sumoto, Japan, has identified comet C/2000 S2 (cf.
IAUC 7498) with comet D/1984 W1 (Shoemaker 2), the comet now being
off from his prediction (cf. ICQ 2000 Comet Handbook) by Delta(T)
= +23.2 days or about 7.5 deg in sky position.  The following
orbital elements by Nakano are from 23 observations, 1984-2000
(mean residual 0".9):

                    Epoch = 2000 June 25.0 TT
     T = 2000 July 14.2917 TT         Peri. = 317.7452
     e = 0.666835                     Node  =  55.3594  2000.0
     q = 1.319021 AU                  Incl. =  21.6197
       a =  3.959066 AU    n = 0.1251166    P =   7.878 years

                    Epoch = 1984 Sept.17.0 TT
     T = 1984 Sept.26.6713 TT         Peri. = 317.5714
     e = 0.666745                     Node  =  55.5012  2000.0
     q = 1.319905 AU                  Incl. =  21.5897
       a =  3.960650 AU    n = 0.1250415    P =   7.882 years


SUPERNOVA 2000dn IN IC 1468
     S. Jha, P. Challis, T. Matheson, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, report that a spectrum of SN
2000dn (cf. IAUC 7498), taken by Z. Balog on Sept. 29.27 UT with
the F. L. Whipple Observatory 1.5-m telescope (+ FAST spectrograph),
shows it to be a type-Ia supernova just before maximum light.
Given the NASA/IPAC Extragalactic Database recession velocity of
9613 km/s for the host galaxy, the expansion velocity of the
supernova is 10 800 km/s, measured using the Si II (rest 635.5 nm)
feature.  The spectral-feature age of the supernova (Riess et al.
1997, A.J. 114, 722) is 3 +/- 2 days before maximum light.


COMET C/1999 Y1 (LINEAR)
     H. Fukushima, T. Nakajima and J. Watanabe, National
Astronomical Observatory, Tokyo, report that I-band CCD images,
taken with the 0.50-m telescope on Sept. 21.556 and 26.602 UT, show
an antitail of lengths 1'.65 in p.a. 31.6 deg and 2'.14 in p.a.
29.4 deg, respectively.  This antitail seems to be connected to the
edge of an elongated jetlike structure extending in p.a. 146.0 and
139.1 deg (respectively on the two dates) from the nuclear
condensation, though the condensation is offset from the
tail-extension line.

                      (C) Copyright 2000 CBAT
2000 September 29              (7499)            Daniel W. E. Green

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