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Fragment C Observation Reports


IRTF detection of C fragment impact site

Beginning at 1994 Jul 17 7:15 UT, the NASA/Infrared Telescope Facility observed the development of a bright spot on Jupiter associated with the impact of fragment C. The NSFCAM near-infrared camera took 0.9-sec integrations every 3.6 seconds at a wavelength of 2.248 +/- 0.011 microns. Starting at 6:51 UT, the camera recorded Io and Europa, searching for a flash; no flash was obvious but the data are yet to be photometrically reduced. At 7:15 the telescope moved to Jupiter, and detected both the remnant of the A impact, with a surface brightness similar to that of the south polar hood at this wavelength, and a dim spot from fragment C. By 7:18, site C was considerably brighter than site A, but by 7:28 site C had faded to about site A's brightness, and continued to fade until about 7:40, when it was considerably fainter.

NASA/IRTF Comet Collision Science Team

SPIREX detects fragment C impact site

SPIREX detected a fragment C impact site at 07:19 UT at a wavelength of 2.36 microns. The impact site has also been monitored at 2.20 microns.

SPIREX will continue to monitor further impacts in these bands.

Mark Hereld, Hien Nguyen, Bernard J. Rauscher, Scott A. Severson Astronomy & Astrophysics Center, University of Chicago

Detection of HCN following impact C

16th July

Detection of HCN 4-3 in emission following impact of fragment C:

We observed the HCN 4-3 line at 354.505 GHz using Receiver B3i on the JCMT with a beamwidth of 14" FWHM. We tracked on the position of fragment B for over 1 hour, but did not detect anything to an rms noise of 0.2 K antenna temperature. Observations of the location of the fragment C impact point over a 30-minute period as it rotated into view produced a detection of an approx. 1-K line at the correct velocity (19 km/s). The line half-width is about 10 km/s. Subsequent observations did not result in a confirmation of the detection, but Jupiter was setting and the system temperature rapidly increasing. We are therefore not able to say whether or not the effect was short-lived.

Matt Griffin, Andre Marten, David Naylor, Gary Davis, Greg Tompkins

UKIRT/CGS4 observations of the impact of fragment C

CGS4 (with echelle at about 20 km/s resolution) on UKIRT detected dramatic changes in the spectrum near 3.5um at the location where the C fragment struck Jupiter. In addition to a bright continuum (where there previously was essentially none), the relative strengths of pre-existing emission lines of H3+ changed and many new lines appeared, very few of which are identified by us at present. In particular, at the wavelength of a previously undetectable "hot band" transition of H3+, a bright line appeared whose strength surpassed that of all other pre-existing H3+ lines. A second line, unidentified at present, succeeded in saturating its central pixel in a ten second exposure. Some of the lines seem considerably (Doppler) broadened, but, due to the high density of spectral features, confirmation will have to wait until after the observers get some sleep. The emission faded with a 1/e time of roughly 15 minutes.

Tom Geballe
Mary-Frances Jagod
Steve Miller
Tim Brooke

Japanese Observation of C & D

First report from Okayama Astrophysical Observatory.

We observed the plumes of C and D with Near-IR camera attached to 188cm telescope at Okayama Astrophysical Observatory, National Astronomical Observatory of Japan.

Thermal plume of C appeared 07:17 UT on July 17 on 2.36 micron images. It was the brightest around 07:21. The decay phase was observed over one hour. Thermal plume of D appeared 12:01 UT on July 17, but it is fainter than that of C.

J. Watanabe, T. Yamashita, H. Hasegawa, S. Takeuchi, M. Abe, Y. Hirota, E. Nishihara, A. Mori, S. Okumura,

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