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IAUC 6187: 1995 O1; PSR J0538+2817

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                                                  Circular No. 6187
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

COMET 1995 O1
     Independent reports of the visual discoveries of a new comet
have been received from Alan Hale and Thomas Bopp, with available
observations given below.  All observers note the comet to be
diffuse with some condensation and no tail, motion toward the west-

     1995 UT           R.A. (2000) Decl.        m1       Observer
     July 23.264      18 44.23     -32 13.6    10.5      Hale
          23.30       18 46        -32.6       10.8      Stevens
          23.375      18 44.17     -32 11.2              Hale

A. Hale (Cloudcroft, NM).  0.41-m reflector.
J. Stevens and T. Bopp (near Stanfield, AZ).  0.44-m f/4.5 Dobsonian
  reflector.  Comet found while observing M70.

PSR J0538+2817
     X. Sun, Max-Planck-Institut fur Extraterrestrische Physik
(MPIEP) and Institute of High Energy Physics, Beijing; B.
Aschenbach, W. Becker, and J. Truemper, MPIEP; and S. Anderson and
A. Wolszczan, Pennsylvania State University, report the discovery
of x-ray emission from the radio pulsar PSR J0538+2817 in S147 (=
G180.0-1.7; cf. IAUC 6012) at count rates of 0.048 +/- 0.013 and
0.051 +/- 0.012 count/s in the broad (0.8-2.0 keV) and hard (0.5-2.0
keV) energy bands, respectively:  "The x-ray source was detected
during the ROSAT All Sky Survey at R.A. = 5h38m26s.0, Decl. =
+28o17'15" (equinox 2000.0), which is only 14" away from the radio
pulsar (Anderson et al. 1995, work in progress), well within the
error of the ROSAT PSPC position.  There is no other object in the
vicinity of the source in the SIMBAD and GSC databases.  The short
survey exposure time does not permit a timing analysis or a search
for a compact nebula emission, although a large complex diffuse
emission associated with SNR S147 was detected in the hard-energy
band.  Assuming a blackbody spectrum and a 10-km-radius emission
area, and adopting the column density (1.2 x 10E21) and distance
(1.5 kpc) derived from the radio-dispersion measure, the energy
distribution of photons can be used to constrain the temperature
and luminosity to about 0.1 keV and 3 x 10E32 erg/s.  This
temperature is in rough agreement with the prediction of standard
neutron star cooling models using the spin-down age of 6 x 10E5 yr."

1995 July 23                   (6187)            Daniel W. E. Green

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