Central Bureau for Astronomical Telegrams
IAUC 6028: 1993e
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Circular No. 6028
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)
T. Rettig, J. Hahn, S. Tegler, M. Mumma and M. DiSanti (cf. IAUC
6019) report a "last look" detection of fragment K = 12 out at a
distance of about 20 jovian radii in a Hubble Space Telescope WFPC image
on July 18.554 UT, 21 hours prior to impact. Comparison with a June 26
image shows that the elongation of the inner coma has become even more
pronounced. This elongation is parallel to the jovian direction
and also appears slightly brighter or more extended toward Jupiter.
Preliminary analysis of the July 18 image shows only the region within
about 0".1 of the central pixel to have circular symmetry.
At 0".3-0".4 from this pixel the surface brightness aspect ratio has
increased to about 2:1 and at 0".7-0".8 to 2.5-3:1.
The K impact has been documented in reports received via the SL9
message center. SPIREX (cf. IAUC 6026) imaged the impact over the limb
at 2.36 microns on July 19.440 UT, the peak brightness appearing comparable
to that of the G impact. At Okayama Astrophysical Observatory (cf. IAUC
6025) an initial 2.36-micron flash was detected on July 19.434, followed
by an increase on July 19.438 that reached a maximum around 19.443 of
perhaps more than 20 times the brightness of Io. M. A'Hearn, University
of Maryland, reports that R filter observations at the Perth Observatory
during July 19.417-19.437 showed no hint of a flash reflected from Europa,
then in eclipse; beginning July 19.441 methane 893-nm filter observations
showed a definite prominence above the apparent limb of Jupiter having
approximately the same surface brightness as other portions of that
latitude belt. CASPIR (cf. IAUC 6024) confirmed that that there was no
reflected emission from Europa and noted the first indication of a plume
at 2.34 microns on July 19.432; on 19.434 a bright fireball was detected
and seen to grow to twice the size of the nearest remnant impact site by
19.435, after which it remained constant until 19.439, when an intense
central core brightened enough to cast diffraction spikes across the array;
as the site rotated into view the fireball increased in brightness, and
by July 19.440 it was estimated as slightly brighter than the peak
brightness of impact G yesterday.
A message-center report by E. Lellouch, M. Festou and G. Paubert
mentions that IRAM 30-m observations of site G on July 18.760 and 18.861
UT (about 25 min integration in each case) shows the CO 230-GHz line,
about 0.6 K contrast, 2.5 km/s FWHM wide and integrated intensity about
1.5 K km/s. A marginal detection at site H around July 18.819
possibly showed the line with an intensity of about 0.3 K km/s.
Further high-resolution (100 kHz or so) monitoring is urged.
1994 July 19 (6028) Brian G. Marsden
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