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Microturbulence in the upper photosphere of Alpha Persei (F5 Ib) derived from ultraviolet spectral observationsHigh-resolution ultraviolet spectra of the moderate supergiant Alpha Per (F5 Ib) were studied to determine the dynamic state of its upper photosphere. It was found that the line-of-sight microturbulent velocity component in the region of origin of the UV spectrum is about 5 km/s, and is slightly smaller than the value derived from the visual spectrum. This is ascribed to dissipation of mechanical energy between the higher and lower layers where, respectively, the ultraviolet and visual light lines originate. Between these two levels, which are one scale height apart, the mechanical energy flux decreases to about 0.3 of its photospheric value. The consequent value for the (outward directed) turbulent acceleration is 24 cm/sec-squared, more than one half the observationally determined effective acceleration of gravity.
Document ID
19880033382
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Spaan, F. H. P.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
De Jager, C.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nieuwenhuijzen, H.
(SRON Laboratorium voor Ruimteonderzoek, Utrecht, Netherlands)
Kondo, Y.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 13, 2013
Publication Date
October 1, 1987
Publication Information
Publication: Astronomy and Astrophysics
Volume: 185
Issue: 1-2,
ISSN: 0004-6361
Subject Category
Astrophysics
Accession Number
88A20609
Distribution Limits
Public
Copyright
Other

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