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IAUC 5557: 1992k; PSR 0833-45

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IAUC number

                                                  Circular No. 5557
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505

     The following additional positions have been reported:

     1992 UT             R.A. (2000) Decl.        m1    Observer
     July  5.46597    4 57 14.57   +34 42 04.6    9     Helin
           5.47523    4 57 16.76   +34 41 44.2            "
           6.456      5 01.9       +34 06         9.2   Morris

E. Helin, K. Lawrence, L. Lee, and D. Moraru (Palomar).  0.46-m
   Schmidt telescope.  Measurer K. Lawrence.  Second film very dark.
C. S. Morris (near Mt. Wilson, CA).  0.26-m reflector.  Comet well
   condensed with 1'.8 coma.

PSR 0833-45
     M. Strickman and J. E. Grove, Naval Research Laboratory; and
S. Matz and M. Ulmer, Northwestern University, on behalf of the
OSSE team, report:  "PSR 0833-45, the Vela pulsar, was observed by
the OSSE instrument onboard the Compton Gamma Ray Observatory during
the intervals 1991 Aug. 22-Sept. 5, 1992 Apr. 23-28, and May 7-
14.  Using radio ephemerides supplied to the Compton instrument
teams by J. Taylor et al. (1992, private communication) for the
above intervals, OSSE data with 4-ms time resolution were folded at
the radio period.  The resulting light curves indicate positive
detections of the pulsar in the energy bands 0.06-0.17 and 0.20-0.55
MeV, with an overall statistical significance of about 4-sigma
distributed over the three observation periods.  No significant flux
was detected in the energy band 0.69-1.8 MeV, and only a marginally
positive flux was observed in the 1.8- to 8.7-MeV band.  The phase-
averaged pulsed fluxes observed in these energy bands are (3.8 +/-
1.1) x 10E-4, (1.8 +/- 0.5) x 10E-4, (0.1 +/- 2.4) x 10E-5, and
(7.1 +/- 3.3) x 10E-6 photons cmE-2 sE-1 MeVE-1, respectively.  The
fluxes have been derived by fitting a template model to the light
curve for each band.  The quoted uncertainties are based on counting
statistics.  The observed light curve generally resembles the
light curve at higher gamma-ray energies (e.g., Bennett et al.
1977, A.Ap. 61, 279), consisting of two peaks separated by about
0.45 in phase.  The second peak is significantly lower and broader
than the primary, and there is no significant interpulse observed.
The first peak lags the radio peak by an amount in approximate
agreement with observations at higher energies (e.g., Buccheri et
al. 1978, A.Ap. 69, 141)."

1992 July 6                    (5557)            Daniel W. E. Green

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