Electronic Telegram No. 832
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://cfa-www.harvard.edu/iau/cbat.html


COMET C/2006 P1 (McNAUGHT)
     C. Snodgrass, European Southern Observatory (ESO); A. Fitzsimmons,
Queen's University, Belfast; O. Hainaut, ESO; M. Hamuy, Universidad de
Chile; D. Hutsemekers, Universite de Liege; E. Jehin, ESO; M. Jones,
Universidad de Chile; and J. Manfroid, Universite de Liege, report on
narrow-band imaging of the near-nucleus coma of comet C/2006 P1 using the
EMMI instrument on the 3.5-m New Technology Telescope at ESO.  Processing
using the Larson-Sekanina algorithm on dust-continuum filter images
(wavelength 441.7 nm; FWHM = 3.7 nm) on Jan. 29.02 UT reveals sunward
emission of a broad fan of material extending to a projected distance of
13000 km from the nucleus.  Images through a filter centered on the CN(0-0)
emission band (385.9 nm; FWHM = 4.9 nm) show strong spiral jets at p.a.
90, 230, and 330 degrees, extending to at least 32000 km from the nucleus.
Images obtained on Jan. 31.02 UT show a relatively unchanged dust
mophology, as well as jets in the CN filter at p.a. 70, 120, 210, and 330
degrees.
     Jehin, Manfroid, Snodgrass, Fitzsimmons, Hainaut, and Hutsemekers,
together with O. Marco (Universidad Santiago de Chile, Planetario), add
that that two 5-min echelle spectra, obtained as above on Jan. 29.02 UT of
the inner coma of comet C/2006 P1 (at airmass about 5.0), have revealed
very strong emissions of the Na I doublet at 589 nm (100 times stronger
than the Na I sky lines, and the brighest lines of the whole spectrum).
The slit size was 1" x 3" (sampling a region of 800 km x 2300 km
perpendicular to the line of sight and providing a dispersion of 0.0022
nm/pixel) and oriented along the sun-comet vector (p.a. 172 deg).  The
position of the lines are 589.069 and 589.669 nm, giving a velocity of
37.93 km/s -- in agreement with the nucleus velocity of 37.84 km/s.  On
Jan. 31.02, low-resolution (0.37 nm/pixel) long slit (0".5 x 200", or
400 km x 160000 km) spectra covering the full optical wavelength range
were obtained with the same telescope, along and perpendicular to the
sun-comet vector (p.a. 173 deg).  Those spectra clearly show spatially
assymetric Na I lines in the inner coma (excess in the sunward direction
for about 4500 km) and the presence all along the anti-sun direction
(over the extend of the full CCD frame, about 100") of a rather constant
emission (not present in the direction perpendicular to the tail).  This
is most probably the sign of the existence of a Na I tail like the one
observed for comet C/1995 O1 (Hale-Bopp).  On Feb. 2.02, new EMMI echelle
spectra still showed the Na I lines, but 10 times weaker.


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

                         (C) Copyright 2007 CBAT
2007 February 4                  (CBET 832)               Daniel W. E. Green