115 research outputs found
A Quarter-Century of Observations of Comet 10P/Tempel 2 at Lowell Observatory: Continued Spin-Down, Coma Morphology, Production Rates, and Numerical Modeling
We report on photometry and imaging of Comet 10P/Tempel 2 obtained at Lowell
Observatory from 1983 through 2011. We measured a nucleus rotation period of
8.950 +/- 0.002 hr from 2010 September to 2011 January. This rotation period is
longer than the period we previously measured in 1999, which was itself longer
than the period measured in 1988. A nearly linear jet was observed which varied
little during a rotation cycle in both R and CN images acquired during the 1999
and 2010 apparitions. We measured the projected direction of this jet
throughout the two apparitions and, under the assumption that the source region
of the jet was near the comet's pole, determined a rotational pole direction of
RA/Dec = 151deg/+59deg from CN measurements and RA/Dec = 173deg/+57deg from
dust measurements (we estimate a circular uncertainty of 3deg for CN and 4deg
for dust). Different combinations of effects likely bias both gas and dust
solutions and we elected to average these solutions for a final pole of RA/Dec
= 162 +/- 11deg/+58 +/- 1deg. Photoelectric photometry was acquired in 1983,
1988, 1999/2000, and 2010/2011. The activity exhibited a steep turn-on ~3
months prior to perihelion (the exact timing of which varies) and a relatively
smooth decline after perihelion. The activity during the 1999 and 2010
apparitions was similar; limited data in 1983 and 1988 were systematically
higher and the difference cannot be explained entirely by the smaller
perihelion distance. We measured a "typical" composition, in agreement with
previous investigators. Monte Carlo numerical modeling with our pole solution
best replicated the observed coma morphology for a source region located near a
comet latitude of +80deg and having a radius of ~10deg. Our model reproduced
the seasonal changes in activity, suggesting that the majority of Tempel 2's
activity originates from a small active region located near the pole.Comment: Accepted by AJ; 29 pages of text (preprint style), 8 tables, 7
figure
The Increasing Rotation Period of Comet 10P/Tempel 2
We imaged comet 10P/Tempel 2 on 32 nights from 1999 April through 2000 March.
R-band lightcurves were obtained on 11 of these nights from 1999 April through
1999 June, prior to both the onset of significant coma activity and perihelion.
Phasing of the data yields a double-peaked lightcurve and indicates a nucleus
rotational period of 8.941 +/- 0.002 hr with a peak-to-peak amplitude of ~0.75
mag. Our data are sufficient to rule out all other possible double-peaked
solutions as well as the single- and triple- peaked solutions. This rotation
period agrees with one of five possible solutions found in post-perihelion data
from 1994 by Mueller and Ferrin (1996, Icarus, 123, 463-477), and unambiguously
eliminates their remaining four solutions. We applied our same techniques to
published lightcurves from 1988 which were obtained at an equivalent orbital
position and viewing geometry as in 1999. We found a rotation period of 8.932
+/- 0.001 hr in 1988, consistent with the findings of previous authors and
incompatible with our 1999 solution. This reveals that Tempel 2 spun-down by
~32 s between 1988 and 1999 (two intervening perihelion passages). If the
spin-down is due to a systematic torque, then the rotation period prior to
perihelion during the 2010 apparition is expected to be an additional 32 s
longer than in 1999.Comment: Accepted by The Astronomical Journal; 22 pages of text, 3 tables, 6
figure
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