Central Bureau for Astronomical Telegrams
IAUC 4235: 1986i; GX 17+2; VY Aqr
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Read IAUC 4236
Circular No. 4235
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
COMET CHURYUMOV-SOLODOVNIKOV (1986i)
J. B. Tatum, University of Victoria, provides the following
precise positions. The July 20 position is of a smudge on a plate
severely blackened by moonlight.
1986 UT R.A. (1950.0) Decl.
July 19.42153 21 44 07.07 -15 11 23.7
19.44861 21 44 03.88 -15 12 27.2
20.45035 21 41 56.70 -15 49 47.9
Total visual magnitude estimate by C. S. Morris, Whitaker
Peak, CA (0.26-m reflector): July 19.47 UT, 12.8; coma diameter
1.3, some central condensation, tail 1' long in p.a. ~ 280).
GX 17+2
P. Hertz and K. S. Wood, Naval Research Laboratory, write:
"During continuing analysis of data obtained with the A-1 experiment
on HEAO 1 we discovered an apparent 19.5 +/- 0.2 hr x-ray periodicity
in the bright galactic bulge source GX 17+2 = 4U 1813-14 =
Ser X-2. The data consist of x-ray flux determinations spaced
unevenly in time: 56 were obtained during 1977 Sept. 23-30 and 79
during 1978 Mar. 21-28. During the 1978 observations GX 17+2 had a
steady flux of ~ 230 ufu, with several flares to ~ 365 ufu. The
nonflaring data show an approximately sinusoidal variation with a
peak-to-peak flux range of ~ 50 ufu. The probability that the
variation is spurious is < 0.01 percent, and evidence for several
subharmonics is seen in the power spectrum. The flares appear to
be periodic with the 19.5-hr period, and they occur preferentially
near the peak of the sinusoidal variation. In 1977 the source flux
decreased from ~ 315 to ~ 235 ufu over the 7-day period, and a
flare to ~ 420 ufu was observed at the end of the period. No periodic
variations were observed in the 1977 data. The 19.5-hr period
is consistent with that of a close binary if the companion star is
slightly evolved, as in the case of V818 Sco = Sco X-1. Observers
with data covering these timescales are encouraged to search for
this period, particularly if their observations are near 1978 Mar."
VY AQUARII
Magnitude estimates by R. H. McNaught, Coonabarabran, N.S.W.:
May 24.80 UT, 14.5; 25.64, 14.6:; 26.83, [14.8; 30.80, [15.6.
1986 July 22 (4235) Brian G. Marsden
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