Electronic Telegram No. 1294
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html


COMET 8P/TUTTLE
     M. Drahus, C. Jarchow, and P. Hartogh, Max-Planck-Institut fuer
Sonnensystemforschung; and W. Waniak, Astronomical Observatory, Jagiellonian
University; T. Bonev and G. Borisov, Institute of Astronomy, Bulgarian Academy
of Sciences; K. Czart, Torun Center for Astronomy; and M. Kueppers, European
Space Astronomy Center, report on millimeter-wavelength spectroscopy of the
HCN molecule in comet 8P using the Arizona Radio Observatory Submillimeter
Telescope on Mount Graham.  The molecule was observed through the J(3-2) line
at 265.9 GHz with spectral resolution up to 1 million.  The half-power radius
of the beam was 14.5 arcsec, corresponding to 2600 km at the comet.  With five
hours of monitoring on 2007 Dec. 30, three hours on Dec. 31, and five hours on
2008 Jan. 1, clear variability of the line profile is present, most likely
stimulated by the nucleus' rotation.  The repeatability of the spectra from
different nights is consistent with rotation periods of 5.7 hr, 7.4-7.6 hr,
and their multiplicities.  Very similar values have been found previously
(cf. IAUCs 8906, 8909); however, the period of 7.4 hr phases the spectra
noticeably better than does the period of 5.7 hr.  Multiplicities of both base
periods cannot be excluded, though they are difficult to evaluate (especially
periods longer than 15 hr), as they suffer from poor overlap or/and coverage
of the observed rotation phases.  The gas-expansion velocity, suggested by the
line profiles, is equal to 0.8 km/s.  The line area remains constant to a
precision of about 30 percent, suggesting that the production rate log Q(HCN)
= 25.45, assuming a constant rotational temperature of 60 K.
     Selected visual total-magnitude and coma-diameter estimates (cf. IAUC
8903, 8909):  Jan. 11.44 UT, 5.9, -- (D. A. J. Seargent, Cowra, N.S.W.,
Australia, naked eye); 13.39, 5.8, 20' (Y. Nagai, Gunma, Japan, 7x35
binoculars); 26.80, 6.3, 15' (J. J. Gonzalez, Asturias, Spain, 10x50
binoculars); Feb. 1.43, 6.8, 9' (S. Rae, Tauranga, New Zealand, 10x50
binoculars); 8.97, 6.7, 10' (A. Amorim, Florianopolis, Brazil, 10x50
binoculars); 24.98, 7.4, 8' (M. Goiato, Aracatuba, Brazil, 7x50 binoculars);
27.15, 7.6, 4'.8 (J. Shanklin, Rothera station, Antarctica, 0.09-m refractor);
Mar. 6.98, 7.3, 6' (J. G. de S. Aguiar, Campinas, Brazil, 25x100 binoculars);
8.96, 7.5, 10' (Amorim).


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

                         (C) Copyright 2008 CBAT
2008 March 10                    (CBET 1294)              Daniel W. E. Green