Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21460511m&link_type=abstract
American Astronomical Society, AAS Meeting #214, #605.11
Astronomy and Astrophysics
Astronomy
Scientific paper
Late B- and early A-type supergiants are notorious for the time variability of their Hα line profiles, but the physical cause of the variations is poorly understood. Usually, the line is filled in by emission, and the blue absorption wing does not extend to the terminal wind speed, which is roughly defined by the blue edges of the ultraviolet resonance lines. On rare occasions, however, the blue wing of Hα goes strongly into absorption over a wide velocity range, from the photospheric velocity almost all the way to the terminal wind speed. This phenomenon was first described by Kaufer et al. (1996, A&A, 314, 599), who denoted it by the term, "High-Velocity Absorption Event."
In this report, high-resolution spectra from Ritter Observatory will be combined with published spectra to examine the temporal recurrence behavior and strength distribution of high-velocity absorption events and their incidence as a function of stellar parameters for the available sample of stars. All B8- and A0-type, Ia-class, stars in the sample that have been sufficiently well observed, as well as one A2-type star, show the events. However, there is some evidence that hyperluminous stars (luminosity class Ia+) do not show the events. In one of the most extensively observed stars in the sample (Rigel, B8 Ia), there is no clear periodicity in the recurrence times of the events. In addition to the strong events discovered by Kaufer et al. (1996), there is a broad distribution of more frequent, weaker events.
Ritter Observatory receives operating support from the National Science Foundation Program for Research and Education with Small Telescopes (PREST) award AST-0440784.
Markova Natalia
Morrison Nancy D.
Rother S. J.
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