Central Bureau for Astronomical Telegrams
IAUC 6030: 1993e
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Circular No. 6030
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)
D. C. Jewitt and D. J. Tholen, University of Hawaii, succeeded
in securing positions of nuclei P2 = 8b, Q1 = 7a, Q2 = 7b, R = 6, S = 5
and W = 1 with the 2.2-m reflector at Mauna Kea on July 19.3 UT, and
new orbit determinations by P. W. Chodas and D. K. Yeomans, Jet
Propulsion Laboratory, have refined the impact times on Jupiter as
follows: P2, July 20.636 UT; Q2, 20.824; Q1, 20.836; R, 21.228;
S, 21.634; W = 22.333. Observations of the impacts that have already
occurred indicate that the predictions on IAUC 6022 tended to be up
to about 0.007 day too early, and it is possible that the new predictions
will still be too early, a problem that can be attributed to
systematic errors in the Guide Star Catalogue (cf. IAUC 6017).
Among the wealth of messages received via the SL9 message
center, one from J. Klavetter indicates that the impact of the missing
fragment M = 10 (cf. IAUC 6017) was observed at the San Pedro
Martir station of the Mexican National Astronomical Observatory.
Observations mainly at 2.1 microns showed a dim spot just beyond site
C on July 20.259 UT, and it continued to brighten until 20.299.
D. Crisp reports for the IRIS observers on the 3.9-m Anglo-Australian
Telescope that the impact flash from fragment N = 9 was detected, using
rapid-sampling imaging photometry with a 2.34-micron filter rather
than K-grism drift scanning, on July 20.441 UT. The intensity of this
flash increased slowly until about 20.442, but it never exceeded 70
percent of the mean surface brightness of the south polar hood. On
resuming the observations on 20.446 after a problem with the instrument
there was no evidence of the N impact site. K-grism drift scanning
from July 20.451 to 20.458 also showed no evidence of the N impact site.
P. McGregor and M. Allen, Australian National Observatory, report that
CASPIR 2.34-micron observations showed the N impact as a faint flash
beginning on July 20.441 and lasting until 20.443, but subsequent
narrow-band imaging failed to detect the site.
Following up their earlier report (IAUC 6028), Lellouch et al.
have continued to monitor CO emission at 230-GHz with the IRAM 30-m
telescope. The detection at impact sites G and H was confirmed on July
19.8 UT at integrated intensities 1.6 and 1 K km/s, respectively.
Re-examination of data from July 17.8 UT showed the emission at
0.6 K km/s at site E and marginally at site C, and a marginal detection
from site E was also made on July 19.8. The width (FWHM) of the
clearly detected lines is constant at 2-3 km/s. Unsuccessful searches
were made for CO+ and H2S.
1994 July 20 (6030) Brian G. Marsden
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