Electronic Telegram No. 4375
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET 41P/TUTTLE-GIACOBINI-KRESAK
     T. L. Farnham, M. S. P. Kelley, D. Bodewits, and M. M. Knight, University
of Maryland, College Park; and A. Thirouin and N. Moskovitz, Lowell
Observatory, Flagstaff, report results from observations of comet 41P from the
Lowell Observatory Discovery Channel Telescope.  A sequence of enhanced
narrowband CN images, obtained during 2017 Mar. 6-9 and supplemented by an
image from 2017 Feb. 24, reveal rotating spiral-arc structures in the coma,
with one persistent jet and a second jet that is visible through part of a
rotation.  Two images obtained 19.9 hr apart show nearly identical morphology,
tightly constraining the nucleus' rotation period.  Phasing these images to
values between 19 and 21 hours suggests that viable rotation periods lie
between 19.75 and 20.05 hr, with the smoothest sequence at 19.9 hr.
Unacceptable sequences result for 10 hr, 6.6 hr, and 4 hr phasing, indicating
that the 19.9-hr period represents a single rotation.  The shape of the arcs
suggest that the positive spin axis is pointed away from the earth in the
vicinity (within about 30 deg) of R.A. = 150 deg, Decl. = +35 deg.  Enhanced
images of the dust coma show structures that remain essentially unchanged
throughout the rotation sequence.

     Total magnitudes reported by K. Kadota, Ageo, Japan, from CCD images
obtained with a 0.25-m f/5 reflector:  2016 Dec.  9.76 UT, 19.1; 28.72, 17.6;
2017 Jan. 16.67, 15.2; 28.57, 13.6; Feb. 6.68, 12.8; 19.58, 11.6; 25.74,
10.7; Mar. 4.51, 10.0.
     Selected visual total-magnitude and coma-diameter estimates sent to the
Central Bureau:  2017 Jan. 24.23 UT, 11.5, 4' (J. J. Gonzalez, Asturias,
Spain, 0.20-m reflector); 24.78, 13.8, 0'.7 (S. Yoshida, Ibaraki, Japan,
0.40-m reflector); Feb. 5.17, 12.7, 0'.6 (W. Hasubick, Buchloe, Germany,
44-cm reflector); 6.78, 13.4, 0'.8 (Yoshida); 16.02, 11.8, 2' (M. Goiato,
Aracatuba, Brazil, 0.22-m reflector); 16.84, 10.9, 4' (J. J. Gonzalez, Leon,
Spain, 0.20-m reflector); 19.47, 11.9, 3'.0 (K. Yoshimoto, Yamaguchi, Japan,
0.20-m reflector); 22.12, 11.3, 3' (Goiato); 24.55, 10.1, 9' (K. Yoshimoto,
Yamaguchi, Japan, 26x100 binoculars); 27.80, 10.0, 6' (M. Lehky, Upice
Observatory, Czech Republic, 20x100 binoculars); Mar. 1.01, 9.1, 7' (J. J.
Gonzalez, Asturias, Spain, 25x100 binoculars); 2.10, 10.2, 6' (Goiato);
3.72, 10.4, 5' (S. Yoshida, Mt. Hanadate, Ibaraki, Japan, 0.40-m reflector);
15.89, 7.8, 17' (J. J. Gonzalez, Leon, Spain, 10x50 binoculars).


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

                         (C) Copyright 2017 CBAT
2017 March 19                    (CBET 4375)              Daniel W. E. Green