[AZ-Observing] P/Holmes spectra
- From: Brian Skiff <bas@xxxxxxxxxx>
- To: amastro@xxxxxxxxxxxxxxx, az-observing@xxxxxxxxxxxxx
- Date: Sat, 27 Oct 2007 01:58:36 -0700 (MST)
Per several items on IAU Circular 8887, issued a few hours ago,
the comet spectrum is greatly dominated by a solar (reflectance)
spectrum, but in the past day or so the outer parts have begun to show
emission bands. The reports suggest the emission is rather weak
compared to the absorption spectrum. Of those mentioned only the
C2 band with the bandhead at 516nm is likely to be detectable visually
(this is one of the "Swan bands"). Excerpts follow.
\Brian
COMET 17P/HOLMES
H. Kobayashi, H. Kawakita, and A. Nishikoji, Kyoto Sangyo
University, report that they have obtained low-dispersion spectra
of comet 17P on Oct. 24.58 and 25.46 UT with a 28-cm telescope (+
F2SPEC spectrograph; range 380-750 nm, resolution 900 at 600 nm).
[i.e. an amateur-sized telescope + spectrograph...]
The comet's spectrum on Oct. 24.58 was dominated by reflected
sunlight, and there were no significant emission bands and lines
visible. The Oct. 25.46 spectrum was still dominated by reflected
sunlight, but emission bands and lines (CN and C_2 bands, as well
as [O I] emission lines) appeared in the spectrum.
R. M. Wagner, LBT Observatory; S. Starrfield, Arizona State
University; [...and a bunch of others]
write that they obtained several
long-slit spectra ....
of comet 17P on Oct. 25.181 and 25.465 UT
with the Bok 2.3-m telescope on Kitt Peak. The spectra exhibit a
strong reflected continuum arising from dust.
[...]
Molecular
emission bands of CN, C_3, C_2, and NH_2 -- typical of other
gaseous comets -- are detected, as well, and are prominent away
from the bright optocenter. Emission from CN (0-0) can be traced
out to at least 2'.4 from the optocenter in each direction.
[...]
A. Fitzsimmons, Queen's University, Belfast; [...and others]
report that spectra of comet 17P, centered on the central
condensation, were obtained on Oct. 26.05 UT using the 2.5-m Nordic
Optical Telescope [... + hi-res spectrograph] on La Palma.
The spectra are dominated by a
reflected solar spectrum from dust grains. Molecular emission bands
due to CN at 388 nm, C_3 at 405 nm, and C_2 at 516 nm are also
visible.
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