Central Bureau for Astronomical Telegrams
IAUC 4883: PeV ENERGY BURST FROM CRAB NEBULA; 1989v
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Circular No. 4883
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
PeV ENERGY BURST FROM CRAB NEBULA
M. V. S. Rao, Tata Institute of Fundamental Research, Bombay,
on behalf of the Kolar Gold Fields (KGF) air-shower group, communicates:
"A burst of PeV-energy radiation from the Crab was detected
on Feb. 23 from the KGF air-shower array, confirming a similar
observation from the Baksan array on the same day (V. V. Alexeenko
1989, paper presented at the Third VHE gamma-ray Astronomy meeting).
The Baksan group, searching over 64 days, found 57 events during
Feb. 23.58-23.79 UT, while the expected background was 31.1 events.
The KGF array recorded 35 events against a background of 17.8 events
during Feb. 23.54-23.67, consistent with the 35-deg difference in
longitude between the two states. The accuracy in the determination
of arrival direction of showers with our array is 2.3 deg in space
angle, obtained by analyzing the same events with two subsets of
timing detectors (odd and even), using the experimentally determined
curvature of the shower front. This is the first time that a burst
of radiation of such energies has ever been recorded simultaneously
from two widely separated stations (the chance probability is 5 x
10E-7). The KGF data show that the muon number in showers arriving
from the Crab is nearly the same as that in normal cosmic-ray
showers, thus making it difficult to understand the radiation as
being gamma-rays. This implies that either photon interactions at
high energies are similar to hadron interactions, or the primaries
are neutrinos interacting with a substantial cross section at high
energies according to some composite models, or that a new strongly-
interacting stable neutral particle is responsible for the events.
Pulsar phase analysis of the KGF data shows that all of the 17
excess events are in the first half of the phasogram, which includes
the main and interpulses seen at other wavelengths. This puts an
upper limit of 40 MeV/c2 on the mass of the new particle. The time-
averaged flux of radiation above 10E14 eV is (8 +/- 2) x 10E-12
cm-2 s-1 during the KGF burst period, corresponding to a luminosity
of 3 x 10E36 erg/s. It may be useful for other air-shower installations
to determine if the burst lasted longer; any observed activity
at other wavelengths during this period would be interesting."
COMET HELIN-ROMAN-ALU (1989v)
Total visual magnitude estimates: Oct. 17.75 UT, 10.3 (R.
Haver, Tolfa, Italy 15x80 binoculars); 20.14, 10.1 (R. A. Keen, Mt.
Thorodin, CO, 0.32-m reflector).
1989 October 23 (4883) Daniel W. E. Green
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