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IAUC 3939: VW Hyi; AM Her; LSS 2018

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                                                  Circular No. 3939
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

     J. Heise, F. Paerels and H. van der Woerd, Space Research
Laboratory, Utrecht, telex: "We have discovered x-ray pulsations
from the dwarf nova VW Hyi during a superoutburst.  The observations
were carried out with EXOSAT after learning of the onset of
the outburst from F. Bateson and the New Zealand variable star
observers. Three observations on 1983 Nov. 15, 21 and 25 revealed
periods of 14.05 +/- 0.23, 14.06 +/- 0.06, and 14.073 +/- 0.008 s.  The
data are consistent with coherent pulsations throughout the 10-day
observing interval, covering the peak and decay portion of the
outburst. The x-ray flux is very soft.  Pulse fractions are 20-30
percent, and the pulse is nearly sinusoidal.  This periodicity is
not seen in optical data taken around the same time.  We shall
continue observing VW Hyi with EXOSAT during the expected superoutburst
in 1984 May.  Optical coverage is requested: contact us at
telephone 31-30-937145 or telex (Netherlands) 47224 ASTRO NL."

     T. Mazeh, Tel Aviv University; K. Kieboom, Technion, Haifa;
and J. Heise, Space Research Laboratory, Utrecht, report that
photometric observations made at the Wise Observatory indicate that
AM Her is still at its low state: Mar. 9.06-9.08 UT, V ~ 15 (with
variations of ~ 0.3 mag), B = 15.3; 12.08, V = 15.3, B = 15.3.

LSS 2018
     J. S. Drilling, Louisiana State University, reports that LSS
2018 (R.A. = 10h52m5, Decl. = -48deg31', equinox 1950.0; B ~ 12), the
central star of the planetary nebula DS1 (Drilling 1983, Ap.J. 270,
L13) is variable.  Analysis of five nights of photometric observations
by J. Bravo and himself at Cerro Tololo Interamerican Observatory
shows a sinusoidal light variation with a period of 8.57
hr and range in B of 0.5 mag: the first maximum was observed on
Apr. 6.165 UT.  Preliminary analysis of 21 high-resolution spectra
of the He II 469-nm absorption line on Apr. 13 and 14 indicates a
sinusoidal variation in radial velocity with the same period and a
range in velocity of 140-150 km/s.  A minimum in the radial
velocity occurred near Apr. 13.215 UT, 2.1-hr before maximum light.

1984 April 25                  (3939)              Brian G. Marsden

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