Astronomy and Astrophysics – Astronomy
Scientific paper
May 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...426..345p&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 426, no. 1, p. 345-356
Astronomy and Astrophysics
Astronomy
19
Balmer Series, Helium, Line Shape, Low Speed, O Stars, Stellar Winds, Ultraviolet Astronomy, Ultraviolet Spectroscopy, Variability, Astronomical Photography, Charge Coupled Devices, H Alpha Line, Iue, Spectrographs, Telescopes, Time Series Analysis
Scientific paper
We describe high-quality, spectroscopic time series observations of variability at low velocities in the stellar wind of the extreme O-supergiant HD 152408. These observations were obtained during a monitoring campaign coordinated between Australia and Chile in 1992 July. Systematic variability on hourly time scales is particularly apparent in the He I lambda 5876 P Cygni profile, which diagnoses the deeper, denser region of the wind. These changes indicate the presence of evolving wind structure, which takes the form of blueward-migrating, discrete optical depth enhancements. Four distinct features are identified over approximately 5 days, spanning a velocity range of about -50 km/s at formation to about -500 km/s (i.e., greater than or approximately equal to 0.5 of the terminal velocity) at the blue edge of the He I absorption trough. Sympathetic variations are also apparent in the Balmer emission lines of HD 152408. The characteristics of these features, including their widths, column densities, and accelerations, suggest similarities to discrete absorption components commonly seen at larger velocities in UV P Cygni profiles of other O-type stars. These optical results demonstrate that frequent, systematic wind variability is present down to very large depths, and provide constraints on the stability of the low-velocity regime of hot-star winds.
Fullerton Alex W.
Prinja Raman K.
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