Issue |
Astron. Astrophys. Suppl. Ser.
Volume 136, Number 2, April II 1999
|
|
---|---|---|
Page(s) | 245 - 256 | |
DOI | https://doi.org/10.1051/aas:1999213 | |
Published online | 15 April 1999 |
Dust continuum imaging of C/1995 O1 (Hale-Bopp):
Rotation period and dust outflow velocity
Astronomiska Observatoriet, Box 515, SE-751 20 Uppsala, Sweden
Received:
12
March
1998
Accepted:
4
November
1998
Dust continuum imaging of comet C/1995 O1 (Hale-Bopp) was carried out
with the Swedish Vacuum Solar Telescope (SVST) on La Palma, Spain,
during the period April 21–25, 1997. CCD observations were made with
and
filters, with
band-passes excluding major cometary gaseous emissions. Images were
reduced according to standard procedure, aligned, averaged, navigated
and enhanced with azimuthal renormalisation, rotational and temporal
derivative and unsharp masking techniques.
The rotation period of the nucleus was determined to
and the
mean projected dust outflow velocity to
measured over a radius range of
. No
difference in quasi-simultaneous dust morphology between the filter
wavelengths was seen. Up to five shell envelopes were visible in the
sun-ward side of the coma out to a radius of
, separated by
a projected distance of ~
and
spiralling towards smaller radii in the direction of local
evening. Outer boundaries of shells were more sharply defined than
inner, with shell intensity maxima occurring at ~35° past the
sun-comet line in the direction of rotation. Small scale
inhomogeneities of size
were seen at
radii
. Two superposed shell systems with a
relative lag angle of ~55° were evident during the
period of observation.
The sense of rotation of dust emission features
indicates that the north pole of the nucleus was directed towards the
Earth. The shape of the incomplete spiral shell pattern
indicates that the angle between the line-of-sight and the rotation
axis of the nucleus was not very large.
Key words: comets: individual: c/1995 01 Hale-Bopp / techniques: image processing
© European Southern Observatory (ESO), 1999