Electronic Telegram No. 4357
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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Prepared using the Tamkin Foundation Computer Network


COMET 45P/HONDA-MRKOS-PAJDUSAKOVA
     M. DiSanti, Goddard Space Flight Center, NASA; B. Bonev, American
University; N. Dello Russo and R. Vervack, Applied Physics Laboratory, Johns
Hopkins University; E. Gibb and N. Roth, University of Missouri at St. Louis;
A. McKay, Universities Space Research Association and Goddard Space Flight
Center; and H. Kawakita, Kyoto Sangyo University, report preliminary water-
production rates, and also production-rate ratios relative to H_2O, for seven
trace volatiles in the Jupiter-family comet 45P, from observations using the
new NASA Infrared Telescope Facility spectrograph, iSHELL, during January 6-8
UT (when r = 0.55-0.56 AU and Delta = 0.57-0.53 AU).  On Jan. 7, the measured
water-production rate was approximately 2 x 10**28 molecules/s, consistent
with a rotational temperature of 90 K.  Measured abundance ratios (preliminary
results) relative to H_2O (in percent) are as follows:  CO, 0.69; C_2H_2,
0.10; CH_4, 0.69; C_2H_6, 0.44; CH_3OH, 3.1; H_2CO, 0.23; HCN, 0.047.
Compared to other Jupiter-family comets, these production-rate ratios are
close to their median values for C_2H_2, H_2CO, and C_2H_6, while CO and HCN
are strongly depleted and CH_3OH is enriched.  The secure detections of CO
and especially CH_4 are of particular importance, as these two molecules have
long been significantly understudied in Jupiter-family comets.

     Cassandra Lejoly and Ellen Howell, Lunar and Planetary Laboratory,
University of Arizona, write that, using the Arecibo Planetary Radar System
during Feb. 9.52-9.59 UT, they detected comet 45P, finding that the visible
range depth was 600-650 m (estimated radius), which gives an estimated
diameter of 1200-1300 m.  The bandwidth was 4.7 Hz, which gives an estimated
period of 7.0-7.5 hours.  This assumes an equatorial view; if the sub-earth
latitude is non-zero, the rotation period could be shorter.  A coma skirt
was also observed, showing a significant amount of centimeter-sized particles
moving away from the nucleus.  The observations were made by Howell and
Lejoly, together with Edgard Rivera-Valentin, Luisa F. Zambrano-Marin, Anne
Virkki, and Patrick Taylor.

     Visual total-magnitude and coma-diameter estimates:  2016 Dec. 3.36 UT,
11.0, 1'.7 (S. Yoshida, Kita-karuizawa, Gunma, Japan, 0.40-m reflector;
diffuse but easy to see); 6.39, 10.9, 1'.2 (K. Yoshimoto, Yamaguchi, Japan,
0.25-m reflector); 16.39, 8.3, 4' (Yoshimoto, 26x100 binoculars); 17.77, 8.5,
2' (J. J. Gonzalez, Leon, Spain, 25x100 binoculars; altitude 8 deg); 22.70,
8.5, 1'.8 (W. Hasubick, Buchloe, Germany, 10-cm refractor); 24.98, 8.2, about
3' (K. Wierzchos, Tampa, FL, USA, 0.15-m reflector); 26.77, 7.3, 4' (Gonzalez,
10x50 binoculars; altitude 9 deg); 28.77, 7.2, 3' (Gonzalez, Asturias, Spain;
altitude 10 deg); 28.98, 7.6, about 3' (Wierzchos); 29.70, 7.6, 1'.6
(Hasubick); 29.77, 7.1, 2'.5 (Gonzalez; altitude 10 deg); 30.77, 7.0, 2'.5
(Gonzalez; altitude 10 deg); 31.40, 6.9, 5' (Yoshimoto, 26x100 binoculars);
2017 Jan. 1.71, 7.4, 2'.2 (Hasubick); 3.77, 6.8, 2'.5 (Gonzalez; altitude 9
deg; moonlight); 6.39, 6.6, 4' (Yoshimoto); Feb.  5.19, 7.0, 15'.7 (Hasubick,
9x63 binoculars); 6.83, 6.9, 16' (S. Yoshida, Ibaraki, Japan, 10x70
refractor); 8.24, 6.7, 22' (Gonzalez, Leon, Spain, 6x40 monocular).
     Total CCD magnitudes:  2016 Dec. 2.37 UT, 12.9 (K. Kadota, Ageo, Japan,
0.25-m reflector); 10.38, 10.9 (H. Abe, Matsue-shi, Shimane-ken, Japan, 0.26-m
reflector); 17.36, 9.0 (Kadota); 24.37, 8.3 (Kadota); 2017 Jan. 1.37, 7.6
(Kadota); 9.36, 7.3 (Kadota); 15.37, 7.3 (Kadota); Feb. 1.86, 8.1 (Kadota);
2.86, 7.2 (K. Yoshimoto, Yamaguchi, Japan, 180-mm f/2.8 lens + Nikon D5100
digital camera G channel; coma diameter 10'.2); 3.86, 7.7 (Kadota).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2017 CBAT
2017 February 10                 (CBET 4357)              Daniel W. E. Green