Central Bureau for Astronomical Telegrams
IAUC 6475: P/1996 S1; NGC 6624
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Circular No. 6475
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 P/1996 S1 (HOLT-OLMSTEAD)
J. V. Scotti, University of Arizona, reports his recovery of
comet P/1990 R2 (= 1990k = 1990 XVIII) with the Spacewatch
telescope at Kitt Peak. The comet appears essentially stellar with
a slight hint of diffuseness, and is close to the prediction on MPC
23482 (ephemeris on MPC 26588).
1996 UT R.A. (2000) Decl. m1
Sept.19.20204 21 39 56.19 -29 50 18.2 20.2
19.21964 21 39 55.54 -29 50 10.1 20.1
19.23678 21 39 54.95 -29 50 02.9 20.1
20.20399 21 39 23.78 -29 42 54.9 20.6
20.22183 21 39 23.17 -29 42 48.2 20.5
20.23900 21 39 22.61 -29 42 39.2 20.4
NGC 6624
S. F. Anderson, B. Margon, and E. W. Deutsch, University of
Washington; R. A. Downes, Space Telescope Science Institute; and R.
G. Allen, University of Arizona, report: "A Hubble Space Telescope
observation of the ultraviolet-bright counterpart to the 11-min
binary x-ray source in the core of the globular cluster NGC 6624
(King et al. 1993, Ap.J. 413, L117) shows a highly-statistically
significant ultraviolet flux modulation with an 11.5-min (+/- 0.2
min) period, consistent with the 685-s period of the known x-ray
modulation. The ultraviolet amplitude is very large compared with
the observed x-ray oscillations: x-ray variations are generally
reported as 2-3 percent peak-to-peak, whereas our data show an
amplitude of order 17 +/- 4 percent in the range 125-250 nm. These
Faint Object Spectrograph data also have spectral resolution of 0.7
nm, so later analysis may reveal spectral-dependent fluctuations in
this amplitude. Arons and King (1993, Ap.J. 413, L121) have
predicted periodic ultraviolet fluctuations in this shortest-known-
period binary system, due to the cyclically changing aspect of the
x-ray-heated face of the secondary star. However, this predicted
modulation has never before been observed. Employing their
formalism, which invokes a number of different physical assumptions,
we infer a system orbital inclination between about 35 and 55 deg.
Additional observations of this exotic system are badly needed."
(C) Copyright 1996 CBAT
1996 September 20 (6475) Daniel W. E. Green
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