NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Chromospheric models for Altair (A7 IV-V)The star, Altair (A7 IV-V), is clearly shown to have Lyman-alpha emission of chromospheric origin, while no evidence is found for the Mg II emission reported in previous investigations. We present non-Local Thermodymanic Equilibrium (non-LTE) semiempirical models incorporating partial redistribution of the chromosphere of Altair that reproduce the observed Lyman-alpha emission and the Mg II resonance absorption at 2800 A. We unambiguously establihed that chromospheres exist at spectral types as early as A7 on the main sequence, and we also demonstrate that it very unlikely that the observed emission originates in a corotating expanding wind. This result represents a new challenge for chromospheric heating theories. It may indicate that both differential rotation and convection layers, at least near the equator, exist in this fast rotating (v sin i = 220 km/s) star.
Document ID
19950044738
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Ferrero, R. Freire
(Observatorie Astronomique Strasbourg, France)
Gouttebroze, P.
(Univ. Paris XI Orsey Cedex, France)
Catalano, S.
(Osservatorio Astrofisco di Catania Catania, Italy)
Marilli, E.
(Osservatorio Astrofisco di Catania Catania, Italy)
Bruhweiler, F.
(Catholic Univ. of America, Washington, DC, United States)
Kondo, Y.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Van Der Hucht, K.
(Space Research Organization Netherlands Utrecht, Netherlands)
Talavera, A.
(ESA-IUE Observatory Madrid, Spain)
Date Acquired
August 16, 2013
Publication Date
February 1, 1995
Publication Information
Publication: The Astrophysical Journal, Part 1
Volume: 439
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A76337
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available