2001/04/05 by J. P. Cassinelli, N. A. Miller, W. L. Waldron +3 · 5 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Doppler effect #Emission spectrum #Line (geometry) #O-type star #Physics #Spectral line #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/320916
published as 2001 ApJ 554:L55 · 4 pages, LaTeX, 3 eps figures, To appear in ApJL
arxiv created 2001/04/05 · openalex publication_date 2001/06/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report on a 67 ks High-Energy Transmission Grating observation of the optically brightest early O star ζ Puppis (O4 f). Many resolved X-ray lines are seen in the spectra over a wavelength range of 5-25 Å. Chandra has sufficient spectral resolution to study the velocity structure of isolated X-ray line profiles and to distinguish the individual forbidden, intercombination, and resonance ( fir ) emission lines in several He-like ions, even where the individual components are strongly Doppler-broadened. In contrast to X-ray line profiles in other hot stars, ζ Pup shows blueshifted and skewed line profiles, providing the clearest and most direct evidence that the X-ray sources are embedded in the stellar wind. The broader the line, the greater the blueward centroid shift tends to be. The N VII line at 24.78 Å is a special case, showing a flat-topped profile. This indicates that it is formed in regions beyond most of the wind attenuation. The sensitivity of the He-like ion fir lines to a strong UV radiation field is used to derive the radial distances at which lines of S XV, Si XIII, Mg XI, Ne IX, and O VII originate. The formation radii correspond well with a continuum optical depth of unity at the wavelength of each line complex, indicating that the X-ray line emission is distributed throughout the stellar wind. However, the S XV emission lines form deeper in the wind than expected from standard wind-shock models.