Issue |
A&A
Volume 420, Number 1, June II 2004
|
|
---|---|---|
Page(s) | 371 - 382 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20034214 | |
Published online | 14 May 2004 |
The gas and dust coma of Comet C/1999 H1 (Lee)*
1
Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain e-mail: rodrigo@iaa.es
2
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: tozzi@arcetri.astro.it
3
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: hboehnha@mpia-hd.mpg.de
4
Isaac Newton Group of Telescopes, PO Box 321, 38700 Santa Cruz de La Palma, Tenerife, Spain e-mail: pleisy@ing.iac.es
Corresponding author: L. M. Lara, lara@iaa.es
Received:
20
August
2003
Accepted:
19
February
2004
Comet Lee (C/1999 H1) was observed on June 6, 1999 when it
was at rh = 0.98 AU and AU. The spectrophotometric observations,
between 0.6 and 1 μm, were aimed at the detection of the CI(1D)
doublet
9823/9850 Å. The non-detection of these
lines, with a
flux upper limit of the order of
, confirms the CO depletion already noted by other
authors. Several CN and NH2 emission bands lie in that spectral
range, making it possible to derive production rates for both species
as ~
and
,
respectively. The oxygen forbidden line at 6300 Å was used to
obtain
. Assuming that CN and NH2 are directly produced by HCN and
NH3, Comet Lee has a
and
at rh = 0.98 AU, in reasonable agreement
with what has been found in other long-period comets. The
structural analysis carried out on cometary images acquired with broad
band R Bessel filter clearly displays two pairs of ion rays likely produced
by the H2O+ doublet at 6198 and 6200 Å,
wavelengths covered by the bandpass filter. Identical
features are found in the images acquired with the Gunn i filter.
The dust brightness profiles in the east-west direction do not
deviate from a
law (with
) as expected
for a steady state model coma with a constant dust production rate and
expanding at constant velocity. The dust production rate, as obtained
from the
parameter, is ~500 cm, which compared with
the gas production rate classifies this comet as a dust poor one with
relatively high (6.5–11.7) gas-to-dust mass ratio. Analysis of the
normalized reflectivity gradient (i.e. continuum color) as a function
of ρ indicates a slight reddening of the solid component in the
coma at large cometocentric distances, whereas the average dust color
within an aperture of 20 000 km, centered at the nucleus, is ~
per 1000 Å. Mie scattering computations applied to an ensemble of
particles indicate that the dust coma is characterised by a relative
broad size distribution with a typical mean size of 1 μm. These
grains might be composed of a mixture of silicates and icy material.
Key words: comets: individual: Comet C/1999 H1 (Lee) / comets: general
© ESO, 2004
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.