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Velocity-Resolved Observations of Hα Emission From Comet C/1995 O1 (Hale–Bopp) |
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| Authors: | Morgenthaler Jeffrey P Harris Walter M Scherb Frank Doane Nathaniel E Oliversen Ronald J |
| Institution: | (1) University of Wisconsin–Madison, Space Astronomy Laboratory, 1150 University Ave., Madison, WI 53706, USA;(2) Present address: NASA/Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA;(3) Department of Physics, University of Wisconsin–Madison, 1150 University Ave., Madison, WI 53706, USA;(4) Department of Astronomy, University of Wisconsin–Madison, 1150 University Ave., Madison, WI 53706, USA;(5) NASA/Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA |
| Abstract: | We present hydrogen Balmer-α spectra of comet C/1995 O1(Hale–Bopp) recorded on 5 nights from 1997 February 1 to April 19 by ahigh-resolution (Δ v = 5 km s-1) Fabry–Pérot spectrometer for a4'.1 (∼2.7 × 105 km) FOV centered 5' sunwardof the nucleus. The Hα line profile is an important diagnostic ofphotolytic heating in cometary atmospheres. Extraction of the spectrafrom the Fabry–Pérot ring images was complicated by obscuration of the telescope FOV due to Hale–Bopp's low elevation, but the measuredH-α line widths of 11–13 km s-1 (FWHM) are insensitive to the spectral extraction technique. The line widths are consistent withestimates derived from a successful model of Hale–Bopp's hydrogenLyman-α coma assuming the inner coma is opaque to Hα. Wediscuss methods for improving the spectral extraction technique andderiving a precise instrument profile which will allow the detailedshape of the line profile to constrain coma models. |
| Keywords: | C/1995 O1 (Hale– Bopp) comets Fabry– Pérot spectrometers hydrogen Balmer-α coma line widths photolytic heating |
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