Other
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995aj....109..350h&link_type=abstract
The Astronomical Journal (ISSN 0004-6256), vol. 109, no. 1669, p. 350-358
Other
38
Absorption Spectra, Binary Stars, Chromosphere, Doppler Effect, Emission Spectra, Spatial Distribution, Starspots, H Alpha Line, Helium, Stellar Spectrophotometry
Scientific paper
A Doppler image of the spot distribution on the RS CVn star DM UMa for the epoch 1993.10 is presented. This distribution is characterized by a polar spot with appendages extending down to low latitudes and at least two isolated spots near the equator. This distribution is typical of what has been seen on other RS CVn stars. Data were simultaneously acquired on the chromospheric activity indicators provided by H alpha and He I D3 5876 A. The H alpha emission and He I absorption significantly increase at phase 0.59, near the time when an equatorial spot is in the line of sight. Possibly, this spot represents a newly emerged magnetic flux region. Such regions on the Sun are accompanied by large scale mass motions, flare activity, and increased x-ray emission and a similar region on DM UMa may account for the increased H alpha emission and He I absorption. The H alpha emission profile was found to be asymmetrical and with broad (200-300 km/s) wings at the continuum. This profile becomes more symetrical after subtracting the underlying H alpha absorption using a rotationally broadened spectrum of alpha Boo. The H alpha profile was parametrized using a narrow and a broad component. The large changes in the strength of the H alpha emission occur primarily in the broad component. The origin of this component is unknown, but it could result from large-scale mass motions or winds in the chromosphere.
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