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Fast spectroscopic variations on rapidly-rotating, cool dwarfs. 3: Masses of circumstellar absorbing clouds on AB DoradusNew time-resolved H alpha, Ca II H and K and Mg II h and k spectra of the rapidly-rotating K0 dwarf star AB Doradus (= HD 36705). The transient absorption features seen in the H alpha line are also present in the Ca II and Mg II resonance lines. New techniques are developed for measuring the average strength of the line absorption along lines of sight intersecting the cloud. These techniques also give a measure of the projected cloud area. The strength of the resonance line absorption provides useful new constraints on the column densities, projected surface areas, temperatures and internal turbulent velocity dispersions of the circumstellar clouds producing the absorption features. At any given time the star appears to be surrounded by at least 6 to 10 clouds with masses in the range 2 to 6 x 10(exp 17) g. The clouds appear to have turbulent internal velocity dispersions of order 3 to 20 km/s, comparable with the random velocities of discrete filamentary structures in solar quiescent prominences. Night-to-night changes in the amount of Ca II resonance line absorption can be explained by changes in the amplitude of turbulent motions in the clouds. The corresponding changes in the total energy of the internal motions are of order 10(exp 29) erg per cloud. Changes of this magnitude could easily be activated by the frequent energetic (approximately 10(exp 34) erg) x ray flares seen on this star.
Document ID
19900013163
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Cameron, A. Collier (Sussex Univ. Brighton (England)., United States)
Duncan, D. K. (Space Telescope Science Inst. Baltimore, MD., United States)
Ehrenfreund, P. (Paris VII Univ. (France). ESTEC, Noordwijk (Netherlands)., United States)
Foing, B. H. (European Space Agency. European Space Research and Technology Center Baltimore, MD., United States)
Kuntz, K. D. (Space Telescope Science Inst. Cambridge (England)., United States)
Penston, M. V. (Royal Greenwich Observatory Epping., United States)
Robinson, R. D. (Anglo-Australian Observatory Baltimore, MD., United States)
Soderblom, D. R. (Space Telescope Science Inst.)
Date Acquired
September 6, 2013
Publication Date
December 20, 1989
Subject Category
Astronomy
Report/Patent Number
NASA-CR-186563
NAS 1.26:186563
Accession Number
90N22479
Funding Number(s)
CONTRACT_GRANT: NAG5-1076
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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