Electronic Telegram No. 4377
Central Bureau for Astronomical Telegrams
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Prepared using the Tamkin Foundation Computer Network


COMET 41P/TUTTLE-GIACOBINI-KRESAK
     M. M. Knight, University of Maryland; N. Eisner, University of Sheffield
and University of Maryland; and D. G. Schleicher and A. Thirouin, Lowell
Observatory, report on imaging of comet 41P obtained during Mar. 18-27 at
Lowell Observatory.  Data were obtained on six nights with the Hall 1.1-m
telescope and the 0.8-m telescope and were supplemented by snapshots on two
nights with the 4.3-m Discovery Channel Telescope.  Enhanced narrowband CN
images reveal the same rotating spiral-arc structure apparently composed of
two jets that were reported by Farnham et al. on CBET 4375.  Nearly identical
morphology was seen in numerous pairs of images acquired one to eight nights
apart throughout the observing window.  The apparent period (i.e., when
features appeared to match) increased from near 24 hr for a pair of images on
Mar. 19 and 21 to near 27 hr for multiple pairs of images on Mar. 26 and 27,
with a progression of apparent periods for many pairs in between.
Extrapolation of this observed trend backwards in time is roughly consistent
with the period near 20 hr during Mar. 6-9 reported by Farnham et al. (op.
cit.).  Data obtained throughout the night on several nights eliminate the
possibility of apparent periods less than 10 hr.  Enhanced C_3 images look
different from CN, notably lacking a corresponding feature to the east.
Variations in C_3 morphology are more subtle, but correlate with the CN
variations.  Enhanced dust, OH, and C_2 images exhibited significantly
different morphology from CN, and all had little discernible variation.

     Additional visual total-magnitude and coma-diameter estimates sent to the
Central Bureau:  Mar. 20.02 UT, 7.5, 20' (J. J. Gonzalez, Asturias, Spain,
10x50 binoculars); 22.58, 7.3, 16' (S. Yoshida, Mt. Hanadate, Ibaraki, Japan,
10x70 refractor); 28.10, 6.5, 25' (Gonzalez, 5x30 monocular).


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2017 CBAT
2017 March 29                    (CBET 4377)              Daniel W. E. Green