Central Bureau for Astronomical Telegrams
IAUC 4845: PSR 0531+21; BERKELEY 87
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Circular No. 4845
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
PSR 0531+21
A. G. Lyne and R. S. Pritchard, University of Manchester,
communicate: "A discontinuity has occurred in the rotation rate
of the Crab Nebula pulsar, PSR 0531+21. Observations at 610 MHz
using a 13-m antenna at Jodrell Bank show that there was
fractional increase in frequency of (6.7 +/- 0.2) x 10E-8
between 9h and 10h UT on Aug. 29. This frequency change is
about twice that observed for the large glitch of 1975 (Lohsen
1975, Nature} 258}, 688."
BERKELEY 87
V. F. Polcaro, Istituto di Astrofisica Spaziale, CNR,
Frascati, and Universita 'La Sapienza', Rome; F. Giovannelli,
Istituto di Astrofisica Spaziale, CNR, Frascati; R. K. Manchanda,
Physics Department, Space Physics Group, AADF, Canberra; L.
Norci and C. Rossi, Istituto di Astronomia, Universita 'La
Sapienza'; and G. Tessicini, Osservatorio Astronomico, Bologna,
write: "We announce the discovery with the Loiano 1.52-m
telescope (+ Boller and Chivens 26767 spectrograph + CCD RCA camera)
of a strong, diffuse C IV (580.1-581.2 nm) emission in the Berkeley
87 cluster near the WR star ST3 (which shows strong emission
from O VI, C IV, and He II). The diffuse emission seems to
cover the entire core of Berkeley 87. This young open cluster
is embedded in the ON2 molecular clouds complex at the boundary
of the Cygnus X region. Its position is fully compatible with
the unidentified COS-B source 2GC 075+00. A weak, hard x-ray
source, positionally coincident with the cluster, was identified
during a slew by the EXOSAT satellite. The UHURU and HEAO-A1
catalogs report sources compatible with the position of
Berkeley 87. We can assume that the envelope of ST3 is strongly
interacting with the cluster's interstellar medium. In particular,
the ON2 association contains the compact HII region G75.77+0.34,
whose angular distance from the center of the cluster is on the
order of 1'. The density of this cloud was evaluated as 10E5
cmE-3. We suggest that the interaction of the ST3 stellar wind
with this cloud generates a shock wave that can accelerate to
relativistic velocities the energetic particles emitted by the
numerous early-type stars contained in the cluster. This mechanism
can originate the high-energy emission. Further observations,
mainly at high energies, are needed."
1989 September 1 (4845) Daniel W. E. Green
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