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IAUC 7270: Cas A; C/1999 J3

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                                                  Circular No. 7270
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)


CASSIOPEIA A
     G. G. Pavlov, Pennsylvania State University; and V. E. Zavlin,
Max-Planck-Institut fur Extraterrestrische Physik, report:  "The
analyses of two observations of Cas A taken with the Einstein HRI
on 1979 Feb. 8 and 1981 Jan. 22 show a pointlike source at R.A. =
23h23m27s.85 +/- 0s.05, Decl. = +58o48'43".8 +/- 0".1, (equinox
2000.0).  This appears to be the same object reported by Tananbaum
et al. from the Chandra ACIS observation (IAUC 7246) and by
Aschenbach from the ROSAT HRI observation (IAUC 7249).  The
apparent separations between the Einstein and Chandra positions of
the source, 1".8 and 2".6, respectively, are comparable with the
position uncertainties, which indicates that the source has not
moved appreciably during the 20-yr span of observation.  The
Einstein HRI background-corrected countrates are 0.0009 +/- 0.0002
and 0.0011 +/- 0.0003 counts/s (exposure times 42 700 and 25 600
s), respectively.  The Einstein HRI, ROSAT HRI, and Chandra ACIS
countrates are consistent with the assumption that the source
spectral flux was the same at each of the four epochs.  If the
source radiates as a blackbody, its size is too small (and the
temperature too high) to interpret the radiation as emitted from
the whole surface of an isolated, cooling neutron star."


COMET C/1999 J3 (LINEAR)
     Ephemeris extension to IAUC 7252 (elements MPC 35814):

1999 TT     R. A. (2000) Decl.   Delta     r    Elong. Phase    m1
Oct.  9     7 53.65   + 6 06.6   0.576   1.030   76.5   70.6    7.5
     11     7 49.36   + 0 24.4   0.550   1.041   78.7   70.1    7.5
     13     7 44.65   - 5 47.5   0.530   1.054   80.9   69.3    7.5
     15     7 39.42   -12 23.7   0.516   1.067   83.1   68.2    7.5
     17     7 33.58   -19 15.6   0.509   1.081   85.2   66.8    7.5
     19     7 27.01   -26 11.8   0.509   1.096   87.1   65.2    7.6
     21     7 19.58   -32 59.9   0.517   1.111   88.7   63.6    7.8
     23     7 11.12   -39 28.7   0.532   1.128   90.0   61.9    7.9
     25     7 01.44   -45 29.2   0.553   1.145   90.9   60.3    8.1
     27     6 50.31   -50 55.9   0.579   1.163   91.4   58.7    8.3
     29     6 37.49   -55 46.1   0.611   1.181   91.7   57.2    8.5

     Visual m_1 estimates:  Oct. 2.07 UT, 7.9 (B. H. Granslo,
Fjellhamar, Norway, 0.07-m refractor); 5.78, 7.5 (Y. Nagai,
Yamanashi, Japan, 11x80 binoculars); 7.35, 7.7 (J. Bortle,
Stormville, NY, 20x80 binoculars).

                      (C) Copyright 1999 CBAT
1999 October 7                 (7270)            Daniel W. E. Green

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