Publications (3)0 Total impact
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M. W. Buie,
L. H. Wasserman,
R. L. Millis,
N. M. White,
R. Nye,
E. W. Dunham,
A. S. Bosh,
R. Stone,
W. B. Hubbard,
R. Hill, [......],
Klinglesmith, D., IV,
J. Sanford,
P. Schwaar,
P. Maley,
W. Owen,
L. Benner,
A. S. Rivken,
J. Spitale, R. L. Marcialis,
L. A. Lebofsky
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ABSTRACT: The sixth largest of the known asteroids, (704) Interamnia, was observed
to occult GSC 23450183 (from the HST Guide Star Catalog) by 10 teams of
observers. The chords cover the southern 60% of the profile of the
asteroid. Our occultation results indicate a best fit circular profile
with a radius of 164.6 km which is very close to the IRAS diameter. The
residuals in the fit are generally less than 10 km but some are clearly
due to topography on the object. The prediction for the event came from
transit telescope measurements which indicated a formal 1-sigma
uncertainty of 94 km. The actual track was 233 km from the prediction
for a 2.5-sigma deviation. The lack of coverage on the north end of the
object was caused by a concentration of stations more to the south based
on the transit predictions. We redetermined the rotation period of 8.70
+/- 0.06 hours from the data of Lustig and Hahn (1976). From our
additional lightcurve observations just before the occultation, we find
that H_V(alpha ) = 6.758 and the aspect was near a broad secondary
minimum in the lightcurve. At the time of the occultation, the solar
phase angle was 11 degrees and the lightcurve amplitude was 4%. The
lightcurve also clearly shows a tertiary maximum 0.15 rotations earlier
than the occultation aspect. This lightcurve structure supports the
presence of topography on the object as seen in the limb fit to the
occultation chords.
06/1997; 29:973.
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J. L. Elliot,
C. B. Olkin,
E. W. Dunham,
C. H. Ford,
D. K. Gilmore,
D. Kurtz,
D. Lazzaro,
D. M. Rank,
P. Temi,
R. M. Bandyopadhyay,
J. Barroso,
A. Barrucci,
A. S. Bosh,
M. W. Buie,
S. J. Bus,
C. C. Dahn,
D. W. Foryta,
W. B. Hubbard,
D. F. Lopes, R. L. Marcialis
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ABSTRACT: Considered as a comet, the object 2060 Chiron is unusual in two respects: it exhibits outbursts at very large distances from the Sun, and its nucleus is much larger than that of any other known comet. It is, however, similar in size to the recently discovered Kuiper-belt objects - a population of objects with orbits beyond Neptune, which are a possible source of short-period comets. This has led to the conjecture that Chiron is related to these objects, but its chaotic orbit has brought it much closer to the Sun. Here we report observations of a recent stellar occultation by Chiron which permit the identification of several features associated with Chiron's coma. The observation of discrete, jet-like features provides evidence that the coma material originates from just few, small active areas, rather than from uniform sublimations, and that the particles in at least one of these features have radii greater than 0.25 microns. The observations also suggest the presence of material in the plane of Chiron's orbit and are consistent with a gravitationally bound coma. Finally, the present data, and those from a previous occultation, constrain the radius of Chiron to lie between 83 and 156 km.
02/1995;
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C.B. Olkin,
J.L. Elliot,
H.B. Hammel,
A.R. Cooray,
S.W. McDonald,
J.A. Foust,
A.S. Bosh,
M.W. Buie,
R.L. Millis,
L.H. Wasserman,
E.W. Dunham,
L.A. Young,
R.R. Howell,
W.B. Hubbard,
R. Hill, R.L. Marcialis,
J.S. McDonald,
D.M. Rank,
J.C. Holbrook,
H.J. Reitsema
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ABSTRACT: This paper presents new results about Triton's atmospheric structure from the analysis of all ground-based stellar occultation data recorded to date, including one single-chord occultation recorded on 1993 July 10 and nine occultation lightcurves from the double-star event on 1995 August 14. These stellar occultation observations made both in the visible and in the infrared have good spatial coverage of Triton, including the first Triton central-flash observations, and are the first data to probe the altitude level 20–100 km on Triton. The small-planet lightcurve model of J. L. Elliot and L. A. Young (1992,Astron. J.103,991–1015) was generalized to include stellar flux refracted by the far limb, and then fitted to the data. Values of the pressure, derived from separate immersion and emersion chords, show no significant trends with latitude, indicating that Triton's atmosphere is spherically symmetric at ∼50-km altitude to within the error of the measurements; however, asymmetry observed in the central flash indicates the atmosphere is not homogeneous at the lowest levels probed (∼20-km altitude). From the average of the 1995 occultation data, the equivalent-isothermal temperature of the atmosphere is 47 ± 1 K and the atmospheric pressure at 1400-km radius (∼50-km altitude) is 1.4 ± 0.1 μbar. Both of these are not consistent with a model based on Voyager UVS and RSS observations in 1989 (D. F. Strobel, X. Zhu, M. E. Summers, and M. H. Stevens, 1996,Icarus120,266–289). The atmospheric temperature from the occultation is 5 K colder than that predicted by the model and the observed pressure is a factor of 1.8 greater than the model. In our opinion, the disagreement in temperature and pressure is probably due to modeling problems at the microbar level, since measurements at this level have not previously been made. Alternatively, the difference could be due to seasonal change in Triton's atmospheric structure.
Icarus.
