[IAUC] CBET 2418: 20100820 : COMET 103P/HARTLEY

[quai en cfa.harvard.edu]

                                                  Electronic Telegram No. 2418
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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 Sciences; Harvard University; 20 Oxford St.; Cambridge, MA  02138; U.S.A.
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COMET 103P/HARTLEY
     M. Knight, E. Schwieterman, and D. Schleicher, Lowell Observatory,
obtained and analyzed extensive CN narrowband images of comet
103P/Hartley on five consecutive nights (2010 Aug. 13-17) using the
Hall 1.1-m telescope at Lowell Observatory. Following the removal of
median radial profiles, an oscillating CN gas feature is seen centered
near position angle 350 deg, consistent with a side-on cork-screw jet
morphology; no dust feature other than the tail was visible in R-band
images. Intervals between 15 pairs of matching CN images from various
rotational cycles, coupled with the spacing and the outward motion of
the feature, imply a nucleus rotation period of 16.6 +/- 0.5 hr,
consistent with the result by Meech et al. (2009, BAAS 41, 1029).
Preliminary modeling suggests a moderate obliquity of the rotation
axis and a mid-latitude source location.
     Schleicher adds that he obtained six sets of narrowband photometry
of comet 103P on Aug. 11 and 12 (when r = 1.48-1.47 AU) using the Hall
1.1-m telescope, resulting in the following averaged production rates:
log Q(OH) = 27.04; equivalent log Q(water; vectorial) = 27.09;
log Q(NH) = 24.87; log Q(CN) = 24.48; log Q(C2) = 24.56;
log Q(C3) = 23.86; log Afrho(526.0 nm) = 0.93 (cf. IAUC 7342).
There is possible evidence of rotational variability, with values for
CN and C_3 lower by 10 percent on Aug. 12 vs. Aug. 11, while dust was
lower by about 20 percent. The implied very-low-dust-to-gas ratio,
based on Afrho vs Q(OH), matches Schleicher's measurements from the
1991 and 1997 apparitions.


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                         (C) Copyright 2010 CBAT
2010 August 20                   (CBET 2418)              Michael Rudenko