EUVE Observations of Soft X-Ray Emissions from Comets 6P/d'Arrest, Bradfield (C/1995 Q1), Hyakutake (C/1996 B2), and Hale-Bopp (C/1995 O1)
V. A. Krasnopolsky (Catholic University / NASA GSFC), M. J. Mumma (NASA GSFC), M. J. Abbott (Center for EUV Astrophysics)
We observed soft X-ray emissions from four comets in a range
of 70-180 eV using the Extreme Ultraviolet Explorer orbiting
observatory. Comet 6P/d'Arrest was observed on 9/4/95 at a
heliocentric distance r = 1.42 AU; its X-ray emission was
ph/s in an aperture radius
km and was offset by km from the nucleus. Data for comet Bradfield
(C/1995 Q1) are 11/7/95, r = 1.50 AU, ph/s for the same aperture. Data for comet Hyakutake
(C/1996 B2) are 3/22/96, r = 1.07 AU, ph/s for the same aperture, km.
Data for comet Hale-Bopp (C/1995 O1) are 9/14/96, r = 3.07 AU,
ph/s for the same aperture and
ph/s for km, km. X-ray spectra and correlations
of the soft X-ray emissions with the observed He 584
emissions and with gas and dust production rates in the
comets are studied to identify processes of X-ray excitation
and to determine their relative contributions.