Central Bureau for Astronomical Telegrams
IAUC 4100: Occn BY NEPTUNE ON 1985 Aug. 20; 1982i
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Circular No. 4100
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
OCCULTATION BY NEPTUNE ON 1985 AUGUST 20
B. Sicardy, A. Brahic, P. Bouchet, B. Grundseth, R. McLaren
and C. Perrier report their observations at 2.2 microns of an occultation
on Aug. 20 by Neptune of star No. 39 on the list of P. Nicholson,
K. Matthews and G. Gilmore; they report the occurrence of
three secondary occultations possibly corresponding to ringlike
arcs around Neptune. Bouchet, observing with the European
Southern Observatory's 1-m telescope until 13 min after emersion,
noted that the occultation by the planet lasted from ~ 5h17m17s to
6h35m45s UT (with a central flash at ~ 5h55m); secondary events
observed at ~ 4h29m and 4h44m20s (with fractional depths 0.35 and
0.15, respectively) may be interpreted as due to semi-transparent
occulting objects at ~ 94 000 km and 74 000 km from Neptune's center
in its equatorial plane. The other observers, using the 3.6-m
Canada-France-Hawaii Telescope at Mauna Kea from 8 min before
immersion, noted the Neptune occultation from ~ 5h28m00s to 6h41m20s:
a secondary event at ~ 6h53m49s (with halfwidth 1.49 s and fractional
depth 0.18) corresponds to an object 17 km wide, located ~
51 000 km from Neptune's center in its equatorial plane.
W. Hubbard, Lunar and Planetary Laboratory, communicates that
F. Vilas observed the occultation from the Cerro Tololo Interamerican
Observatory. Except for two brief guidance checks, she monitored
the star continuously from 3h29m to ~ 7h00m UT. The occultation
by Neptune itself lasted from 5h17m to 6h34m, the central
flash at 5h55m22s having a halfwidth of ~ 20 s and amounting to ~
15 percent. During pre-immersion there was only a 16 percent drop
at 3h44m35s (width ~ 1 s), possibly an instrumental effect;
specifically, the excellent record shows no secondary events at the
times reported at ESO nearby. Post-emersion data were obtained at
high air mass and there were several guiding errors. There were
possible secondary occultation events at 6h49m35s (30 percent drop,
width ~ 2 s) and at 6h53m36s (25 percent drop, width ~ 2 s).
PERIODIC COMET HALLEY (1982i)
A. L. Cochran and E. Barker, University of Texas, report:
"Observations of P/Halley with the McDonald Observatory's 2.7-m
reflector on Aug. 15 and 16 showed the comet to be diffuse with
very little central condensation. CN was detected with a Haser
production rate of log Q(CN) = 24.9. Assuming Q(OH)/Q(CN) = 500,
this implies log Q(OH) = 27.6."
1985 August 28 (4100) Brian G. Marsden
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