[IAUC] CBET 2531: 20101104 : COMET 103P/HARTLEY

[quai en eps.harvard.edu]

                                                  Electronic Telegram No. 2531
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET 103P/HARTLEY
     J. Bauer, Jet Propulsion Laboratory (JPL); R. Walker, Monterey Institute
for Research in Astronomy; A. Mainzer and J. Masiero, JPL; R. Beck, F. Masci,
and R. Cutri, IPAC, California Institute of Technology; E. Wright, University
of California at Los Angeles; and the WISE team -- in collaboration with M.
A'Hearn (University of Maryland), K. Meech (University of Hawaii), C. Lisse
(Applied Physics Laboratory, Johns Hopkins University), and Y. Fernandez
(University of Central Florida) -- report initial results based on 12- and
22-micron infrared photometry of comet 103P taken during May 10-11 (when the
comet was at r = 2.3 AU, Delta = 2.0 AU) by the Wide-field Infrared Survey
Explorer (Wright et al. 2010, A.J. 140, in press).  Analyses of the trail
signal present in the stacked image with an effective exposure time of 158.4
seconds yields optical-depth values near 6 x 10**-10 at a mean anomaly of 0.3
deg trailing the comet nucleus, in both 12- and 22-micron bands.  Analysis of
the dust trail yields beta-parameter values ranging from approximately 1 x
10**-4 to 2 x 10**-4, consistent with derived mean trail-grain diameters
ranging from approximately 1 to 12 mm.  Photometry of the coma at 22 microns,
combined with data from the University of Hawaii 2.2-m telescope obtained by
J. Pittichova, K. Meech, T. Riesen, and H. Kaluna on May 22 [R-band Af(rho) =
0.84 +/- 0.04 in log cm units], provide constraints on the particle size
distribution expressed as a log-number-density/log-mass slope term (alpha).
Initial results yield values of alpha = -0.88 +/- 0.10 in log N(particles/
m^2)/[log mass(kg)] units, steeper than that found for the inbound particle
fluence during the Stardust encounter of comet 81P (Green et al. 2004, J.
Geophys. Res. 109, E12S04).  The extracted nucleus signal at 12 microns is
consistent with a body of average spherical radius of 0.73 +/- 0.10 km,
assuming an emissivity of 0.9.


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                         (C) Copyright 2010 CBAT
2010 November 4                  (CBET 2531)              Daniel W. E. Green