Central Bureau for Astronomical Telegrams
IAUC 6336: C/1996 B2; 4U 1608-52
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Circular No. 6336
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)
COMET C/1996 B2 (HYAKUTAKE)
C. M. Lisse and M. F. A'Hearn, University of Maryland, report
observations of comet C/1996 B2 from the NASA Infrared Telescope
Facility on Feb. 7.5 UT (r = 1.90 AU, Delta = 1.57 AU): "Using a
5".6 aperture, total magnitudes are J = 12.0 +/- 0.02, H = 11.6 +/-
0.02, K = 11.5 +/- 0.02 (2-sigma errors) -- slightly redder than
the sun, suggesting the lack of icy grains -- and N = 4.06 +/- 0.16
(2 sigma). The J-N color is unusually small, suggesting either a
very low thermal emissivity or a very high albedo for the dust."
4U 1608-52
J. van Paradijs, University of Alabama in Huntsville and
University of Amsterdam; W. Zhang, Universities Space Research
Association (USRA) and Goddard Space Flight Center (GSFC); F.
Marshall and J. H. Swank, GSFC; T. Augusteijn, European Southern
Observatory; E. Kuulkers, European Space Agency; W. H. G. Lewin,
Massachusetts Institute of Technology; F. Lamb, University of
Illinois; I. Lapidus, University of Cambridge; J. Lochner and T.
Strohmayer, USRA/GSFC; M. van der Klis, University of Amsterdam; B.
Vaughan, California Institute of Technology; report: "Following
the recent outburst of 4U 1608-52 (IAUC 6331), we have observed
this low-mass x-ray binary for 3 hr on Mar. 3 with the Rossi XTE
(total exposure about 2 hr). The source showed strong quasi-
periodic intensity oscillations (QPOs) throughout the observation.
In the beginning, the QPOs were observed with a centroid frequency
of 850 Hz, a FWHM of 6.8 Hz, and a fractional rms of 6.5 percent.
Twenty minutes into the observation, the centroid frequency started
increasing and 15 min later reached 890 Hz, with a fractional rms
value of 5.2 percent and a FWHM of 15 Hz. Then the centroid
frequency started decreasing through the end of the observation,
when it reached 828 Hz with a fractional RMS of 6.8 percent and a
FWHM of 6.7 Hz. In the course of the observation, the source
intensity in the XTE/PCA band (2-60 keV) showed a slight overall
decrease from 3200 counts/s in the beginning to 3100 counts/s in
the end. The excursion to higher frequency did not correlate with
any change in intensity. With earlier detections of kHz QPOs in
the source 4U 1728-34 (IAUC 6320) and the Z source Sco X-1 (IAUC
6319), our results suggest that kHz QPO are a regular feature of
low-mass x-ray binaries."
(C) Copyright 1996 CBAT
1996 March 6 (6336) Daniel W. E. Green
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