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IAUC 4102: 1985k; GX 17+2; V471 Tau

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                                                  Circular No. 4102
Central Bureau for Astronomical Telegrams
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

     C. Kowal, California Institute of Technology, reports that
Alain Maury has discovered a comet on exposures by J. Schombert
with the 1.2-m Schmidt telescope at Palomar as follows:

          1985 UT           R.A. (1950.0) Decl.      m1

          Aug. 16.331      21 50.1      - 1 31       16
               17.314      21 49.6      - 1 40

The object is diffuse with condensation and a short tail.

GX 17+2
     L. Stella, A. N. Parmar and N. E. White, EXOSAT Observatory,
communicate: "A 20-hr EXOSAT ME observation of GX 17+2 on Aug. 20-
21 has revealed the presence of 1.2-percent-rms, quasiperiodic
oscillations at an average frequency of 7.2 Hz.  The significance of
the broad peak in the power spectrum is more than 40V.  Across the
observation the overall 1-15-keV source count rate decreased almost
linearly from 1840 to 1470 cts/s.  The quasiperiodic oscillations
were only detected at count rates below 1670 cts/s.  Within the
statistical uncertainties the peak frequency and the FWHM (average
value 3 Hz) were consistent with being independent of count rate.
A red noise excess was present with an average lower law slope of
-0.5 and an average rms strength of 1.2 percent (in the 0.07-32-Hz
range).  At intermediate count rates (between 1670 and 1770 cts/s)
there was no evidence for any variability in the 0.07-256-Hz range.
At higher count rates (1770-1840 cts/s), 6-percent-rms red noise
activity was detected down to frequencies of at least 5 Hz, but
with no evidence for quasiperiodic oscillations."

     K. A. Jensen, Naval Research Laboratory, communicates: "A 28-
hr EXOSAT observation of the dA2K0V, 12.5-hr period, detached
binary V471 Tau has revealed soft x-ray pulsations from the white
dwarf.  The pulse period is 554.73 +/- 0.30 s.  The pulse profile is
double-peaked, suggesting a bipolar structure.  The two minima in
the pulse profile have intensities of 0.74 and 0.86 with respect
to the maximum intensity.  A search for evidence of a white dwarf
magnetic field is suggested.  A search for the pulse period in the
optical data base is also suggested."

1985 September 6               (4102)              Brian G. Marsden

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