Central Bureau for Astronomical Telegrams
IAUC 6031: 1993e
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Circular No. 6031
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
PERIODIC COMET SHOEMAKER-LEVY 9 (1993e)
For the Hubble Space Telescope (HST) observing team, K. S. Noll,
Space Telescope Science Institute, reports the following results:
"Ultraviolet spectra of the central 0".9 of impact site G obtained with
the HST Faint Object Spectrograph (FOS) on July 18 show a series of
strong absorption bands over 255-293 nm that we unambiguously identify
as due to S2. A second strong absorption occurs between 180 and 230 nm
caused by a combination of enhanced NH3 and at least one other molecule.
The absorption cross section of H2S provides a good match to the spectrum,
and we regard this as a tentative identification. The absorption bands
are observable in both I/F and in ratios of the impact site spectrum
to the spectrum of the same location obtained on July 14. The spectral
resolution of the FOS for an extended source observed through the
0".9 aperture is 0.4 nm over 160-230 nm and 0.6 nm over 230-330 nm.
We note that enhancements of NH3, H2S and S2 could result from heating
and vaporization of the NH4SH and NH3 clouds. If the sulphur were cometary
in origin, we should also expect enhanced abundances of oxygen- and
carbon-bearing compounds to be detected."
No report has been received of the impact on Jupiter of fragment
P = 8, but one received via the SL9 message center notes that the
French-Spanish-Swedish observing team recorded the impact of Q = 7
(i.e., Q1 = 7a) at 10 microns with the Saclay CAMIRAS camera mounted on
the Nordic Optical Telescope at La Palma. The event occurred on July
20.848 UT and was less bright than the L impact seen yesterday.
M. Lindgren, Uppsala Astronomical Observatory, reports, also from
La Palma, that the Q impact site was in view on July 20.854 UT.
V band imaging with the Swedish solar telescope shows it to be very
similar to the nearby L site: a central dark spot and a diffuse
concentric ring. The seeing was not very good, but it was just
about possible to see an elongation of the central dark spot,
perhaps due to the double impact of Q1 and Q2.
T. Z. Martin has reported via the SL9 message center the
attempted detection of the impacts of fragments B, H and L by the
photopolarimeter radiometer on the Galileo spacecraft (using a filter
at 945 nm). No evidence was found of the B impact. The H and L
impacts were observed at equivalent earth times July 18.81388 and
19.92833 UT, the signal rising to a peak value in about 2 s and then
decreasing to background levels over 25 and 35 s, respectively.
Peak brightness corresponded to about 2 and 4 percent, respectively,
of the brightness of Jupiter itself.
1994 July 20 (6031) Brian G. Marsden
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