Central Bureau for Astronomical Telegrams
IAUC 4858: X0331+53; TeV GAMMA-RAY PULSATIONS FROM 47 Tuc
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Read IAUC 4859
Circular No. 4858
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
X0331+53
F. Makino and the Ginga Team, Institute of Space and
Astronautical Science, telex: "The All Sky Monitor onboard Ginga
discovered the recurrent x-ray transient pulsar X0331+53 (= V0332+53
= BQ Cam) in a bright x-ray outburst. The 1- to 20-keV x-ray
intensity was < 70, about 170, about 250, and about 240 mCrab
on Sept. 15.77, 18.68, 19.68, and 20.68 UT, respectively. This
is a third outburst of this source known to date, following the
ones in 1973 (Whitlock 1989, Ap.J. 344, 371) and 1983-1984 (IAUC
3891). Pointed observations with the Large Area Proportional
Counter onboard Ginga made on Sept. 19.91, 20.24, and 20.83, each
for about 30 min, yielded the preliminary heliocentric pulsation
period of 4.3767 +/- 0.0003 s; the source exhibits very hard x-ray
spectra and rapid x-ray flickering. These properties are consistent
with those observed previously."
TeV GAMMA-RAY PULSATIONS FROM 47 TUCANAE
O. C. de Jager, P. J. Meintjes, C. Brink, H. I. Nel, A. R.
North, B. C. Raubenheimer, D. J. van der Walt, and F. B. Waanders,
Potchefstroom University, R.S.A., communicate: "We have detected
significant pulsed gamma-ray emission above about 5 TeV from the
globular cluster 47 Tuc. The source was observed on 20 nights
between July 7.1 and Sept. 3.9 UT with an average duration of
9000 s per observation. We confirm the 120.2-s transient x-ray
pulsations for X0021.8-7221 found by Auriere et al. 1989 (A.Ap.
214, 113) at a chance probability of 0.0003. Radiation was found
during about 60 percent of all observations with a highly-variable
signal strength varying between 0 and 17 percent of the cosmic-ray
flux. The two most significant detections revealed pulse periods
of 120.09 +/- 0.17 s (Aug. 8.06, chance probability 0.002) and
120.10 +/- 0.23 s (Aug. 10.10, chance probability 0.00001) with
nearly all power in the fundamental harmonic. The peak TeV luminosity
is about 10E36 erg/s, which excludes the cataclysmic-variable
association and suggests that X0021.8-7221 is probably a low-mass
x-ray binary observed at high inclination, explaining the low observed
x-ray luminosity of about 10E34 erg/s. The accretion luminosity
would be above 10E37 erg/s if scaled from the observed conversion
efficiency obtained from other TeV x-ray gamma-ray binaries (e.g.,
Hercules X-1, 4U 0115+63, Vela X-1, and Centaurus X-3)."
1989 September 21 (4858) Daniel W. E. Green
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