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IAUC 3482: 2A 0526-328; HEAO Obs OF X-RAY SOURCES

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IAUC number

                                                  Circular No. 3482
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 617-864-5758

2A 0526-328
     J. van Paradijs, E. P. J. van den Heuvel and F. Verbunt, Astronomical
Institute, University of Amsterdam, write: "We made
spectroscopic observations of the optical counterpart of 2A 0526-328
(IAUC 3298) with the image-dissector scanner on the 3.6-m telescope
at the European Southern Observatory during 1979 Nov. 10.255-10.361
11.335-11.358 and 14.111-14.341 UT.  The spectra show Balmer lines
He I 447.1-, 492.1-, 501.6-, 587.6-nm and He II 468.6-nm in emission,
with variable strength.  The behavior of H-beta agrees with the
results of Watts et al. (1980; M.N. 191, 25P), showing a rather
sharp rise of the equivalent width from 1.2 to 2.3 nm (within 1
hour), and a slower decay (in 2 hours) to 1.2 nm, at which value it
remains for 2 hours.  These H-beta variations support the period of
5.186 hours proposed by Motch (IAUC 3427).  There is much less
clear variation when the data are folded with the possible
4.26-hour period, which Motch could not exclude.  The radial velocity
for H-beta shows a regular variation with a total amplitude of 120 km/s.
This is considerably smaller than the radial-velocity variations
found by Watts et al.  However, the relative phasing of H-beta radial
velocity and linestrength is in agreement with their results."

     N. E. White, S. S. Holt, E. A. Boldt and P. J. Serlemitsos,
Goddard Space Flight Center, write that HEAO 1 and 2 observations in
1978 and 1979 have confirmed the x-ray fluxes of three x-ray sources
to be modulated with periods as follows:

     4U 1822-37: 5.57-hour period (cf. IAUC 3406).  The light curve
is to first order sinusoidal with a peak-to-mean amplitude of 25
percent and the minimum centered on photometric phase ~ 0.8.  In addition,
there is a sharp feature from phase 0.0 to 0.09 wherein the
flux drops to 75 percent of the other minimum.

     2A 0311-227: 81-min period (cf. IAUC 3324).  The light curve is
sinusoidal with a peak-to-mean amplitude of 40 percent and maximum
centered on linear-polarization phase 0.5 (cf. IAUC 3327).  In addition,
there is an absorption dip from phase 0.40 to 0.47.

     4U 2129+47: 5.3-hour period (cf. Ulmer et al. 1980, Ap.J. 235,
L159).  The light curve is basically the same as that reported by
Ulmer with in addition a secondary minimum at phase ~ 0.6 about
three times less deep than the primary minimum.

1980 June 6                    (3482)              Brian G. Marsden

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