Central Bureau for Astronomical Telegrams
IAUC 5478: gamma-RAY BURSTS; P/GRIGG-SKJELLERUP
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 5479
Circular No. 5478
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
gamma-RAY BURSTS
C. A. Meegan, G. J. Fishman, R. B. Wilson, W. S. Paciesas, M.
N. Brock, J. M. Horack, G. N. Pendleton, and C. Kouveliotou report
for the BATSE Science Team: "The BATSE experiment on the Compton
Gamma Ray Observatory has detected 262 cosmic gamma-ray bursts from
1991 Apr. 24 through 1992 Mar. 12. Correcting for the Earth blockage
and experiment dead-time, the full-sky gamma-ray burst rate at
the BATSE sensitivity is 800 +/- 60 events per year. The BATSE
burst location accuracy is typically 6 deg, as determined from BATSE
observations of solar flares and from bursts independently located
by other instruments. The distribution of located events is
isotropic within the statistical limits, as reported previously (IAUC
5358; Nat. 355, 143, 1992). A measure of the dipole moment with
respect to the galactic center is <cos theta> = 0.008 +/- 0.035 (
versus 0 for an isotropic distribution). A measure of the quadrupole
moment with respect to the galactic plane is <sin**2 beta> = 0.31
+/- 0.02 (versus 1/3 for an isotropic distribution). The only
nonuniformity in the observed distribution is consistent with the
nonuniformity in the measured sky exposure map. There is no apparent
clustering of bursts around the LMC, M31, or nearby clusters of
galaxies. The brightness distribution of the analyzed bursts is
inconsistent with a homogeneous, isotropic distribution. The integral
brightness distribution has a slope of about -0.8 (versus -3/2 for a
homogeneous, isotropic distribution). The average value of V/Vmax
is 0.33 +/- 0.02 (versus 1/2 for a homogeneous, isotropic
distribution)."
PERIODIC COMET GRIGG-SKJELLERUP
T. Morley, European Space Operations Centre, informs us that
the second part of the special star catalogue (cf. IAUC 5344) for
use in making observations of this comet in connection with the
Giotto encounter is now ready. The catalogue comprises 1021 reference
stars of mv 11-12 whose positions have been measured using the
Carlsberg Automatic Meridian Circle on La Palma, operated jointly by
Copenhagen University Observatory, Royal Greenwich Observatory, and
Real Instituto y Observatorio de la Armada en San Fernando. The
positions are for equinox J2000.0 and have an average accuracy in R.A.
and Decl. of 0".11. The stars lie within 15' of the ephemeris over
the period from the start of May to early July. The catalogue is
available upon request from OAD, ESOC, Robert-Bosch-Str. 5, W-6100
Darmstadt, Germany (e-mail TMORLEY@ESOC.BITNET).
1992 March 18 (5478) Daniel W. E. Green
Read IAUC 5479
Our Web policy. Index to the CBAT/MPC/ICQ pages.
