Central Bureau for Astronomical Telegrams
IAUC 6147: X-RAY N 1994 IN Sco; PSR 1951+32
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Circular No. 6147
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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 TWX 710-320-6842 ASTROGRAM CAM
MARSDEN@CFA.HARVARD.EDU or GREEN@CFA.HARVARD.EDU (science)
X-RAY NOVA 1994 IN SCORPIUS
B. A. Harmon, S. N. Zhang, W. S. Paciesas, and G. J. Fishman
report for the Compton Observatory BATSE Team: "Since the bright
outburst of the x-ray transient GRO J1655-40 (about 1 Crab, band
20-100 keV) in hard x-rays in 1994 Dec. (ending about Dec. 23), the
source has exhibited two additional episodes of variable high-
energy emission. The first began around 1995 Jan. 12 (IAUC 6128)
and ended about Jan. 25. The second began around Feb. 12 and is
still in progress. Both episodes show daily variations from < 50
mCrab to > 300 mCrab (band 20-100 keV). As in the 1994 outbursts,
the spectrum is a power law extending to at least 200 keV. However,
the best-fit spectral indices are harder, ranging between -2.5 and
-1.9. No unusual hard-x-ray activity was observed in the BATSE
large-area detectors during the Mir/Kvant/TTM measurements on Feb.
22 and 24 (IAUC 6143; R. Sunyaev, private communication)."
PSR 1951+32
P. V. Ramanamurthy, D. L. Bertsch, B. L. Dingus, J. A.
Esposito, C. E. Fichtel, S. D. Hunter, C. v. Montigny, R. Mukherjee,
and D. J. Thompson, Goddard Space Flight Center, NASA; J. M. Fierro,
Y. C. Lin, P. F. Michelson, and P. L. Nolan, Stanford University; G.
Kanbach, H. A. Mayer-Hasselwander, and M. Merck, Max-Planck-Institut
fur Extraterrestrische Physik; D. A. Kniffen, Hampden-Sydney College;
A. G. Lyne, University of Manchester; and J. R. Mattox, University
of Maryland, report: "We detected a sixth high-energy, gamma-ray
pulsar, PSR 1951+32, pulsating in gamma-rays at energy > 100 MeV
with the same 39.5-ms periodicity as detected at radio wavelengths,
using the data obtained during May 1991-July 1994 by the Energetic
Gamma Ray Experiment Telescope aboard the Compton Gamma Ray
Observatory. Though seen only as a weak source amidst the high
background of galactic disk emission, the pulsation in high-energy
gamma-rays is clearly seen, with the null (no pulsed emission)
hypothesis being probable only at a level of < 10E-9. The pulsed
radiation has a photon spectral index of -(1.74 +/- 0.11), and the
phase-averaged integral flux of pulsed gamma-rays is (1.6 +/- 0.2)
x 10E-7 cmE-2 sE-1 at energy > 100 MeV. There is no evidence as
yet for unpulsed emission from the object. The pulsar appears to
have an efficiency of about 0.0038 for converting its rotational
energy loss into gamma-rays at energy > 100 MeV."
1995 March 8 (6147) Daniel W. E. Green
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