Central Bureau for Astronomical Telegrams
IAUC 4147: GX 17+2; U Gem; 1985n; 1985p
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Circular No. 4147
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
GX 17+2
A. Langmeier, G. Hasinger, M. Sztajno, J. Trumper, and W.
Pietsch, Max-Planck-Institut fur Extraterrestrische Physik,
Garching, report: "During the first 5000 s of EXOSAT observations
from 1984 Aug. 7.792-8.167 UT, GX 17+2 (= 4U 1813-14) showed quasiperiodic
oscillations (QPOs) with a centroid frequency of 2.4 +/- 0.4
Hz. The FWHM of the peak in the power spectrum was 4.3 +/- 1.1 Hz
and the equivalent sinusoidal amplitude (rms) modulation was 4
percent. There was no indication of low-frequency noise. The QPOs
were detected at a count rate of ~ 1050 cts/s (per 0.08 m**2 effective
area, 1-20 keV), which corresponds to ~ 1.4 x 10**-11 J m**2 s**-1.
They disappeared above 1150 cts/s and were also not observed during
1985 Aug. 8.750-9.208, when the count rate varied between 1150 and
1300 cts/s. Stella et al. (IAUC 4102) discovered QPOs from GX 17+2
with a centroid frequency of 7.2 Hz (1.2 percent amplitude modulation)
when the source was below 1.3 x 10**11 J m**2 s**-1 (the count
rates quoted by them are per 0.14 m**2 effective area)."
U GEMINORUM
J. A. Mattei, AAVSO, reports that the recent outburst of U Gem
(cf. IAUC 4120) was the longest recorded one since 1856, and this
object has again reached its minimum state, as indicated by the
following visual magnitude estimates: Oct. 11.4 UT, 9.2 (G. Dyck,
N. Dartmouth, MA); 15.45, 9.9 (L. Cook, Concord, CA); 22.34, 9.7
(C. Scovil, Stamford, CT); Nov. 5.45, 10.1 (Cook); 8.51, 10.6
(Cook); 19.22, 13.6 (Dyck); Dec. 9.2, 13.8 (Dyck).
PERIODIC COMET BOETHIN (1985n)
Total visual magnitude estimates: Nov. 1.4 UT, ~ 11 (W. A.
Bradfield, near Adelaide, South Australia, 0.25-m reflector); 3.44,
10.3 (D. A. J. Seargent, The Entrance, N.S.W., 0.15-m reflector);
6.46, 10.0 (Seargent); 6.46, 10.1 (R. McNaught, Siding Spring
Observatory, 0.15-m reflector); 12.46, 9.5 (McNaught, 20x120
binoculars); 14.17, 10.2 (A. Hale, Whitaker Peak, CA, 0.20-m reflector).
PERIODIC COMET CIFFREO (1985p)
Total visual magnitude estimates by J.-C. Merlin, Le Creusot,
France (0.40-m reflector): Dec. 2.83 UT, 12.3; 4.80, 12.4.
1985 December 13 (4147) Daniel W. E. Green
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