Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-12-18
Astronomy and Astrophysics
Astrophysics
34 pages, 10 figures, 7 tables, accepted by Astronomy & Astrophysics
Scientific paper
10.1051/0004-6361:20053838
XMM-Newton observations of the O supergiant zeta Orionis (O9.7 Ib) extend knowledge of its high-resolution spectrum beyond the CVI line at 33.7 Angstroms and suggest a new framework for the interpretation of the X-ray spectra of single hot stars. All the lines are broad and asymmetric with similar velocity profiles. X-rays probably originate in the wind's terminal velocity regime in collisionless shocks controlled by magnetic fields rather than in cooling shocks in the acceleration zone. During post-shock relaxation, exchange of energy between ions and electrons is so slow that electron heating does not take place before hot gas is quenched by the majority cool gas. The observed plasma is not in equilibrium and the electron bremsstrahlung continuum is weak. Charge exchange, ionization and excitation are likely to be produced by protons. Fully thermalized post-shock velocities ensure high cross-sections and account for the observed line widths, with some allowance probably necessary for non-thermal particle acceleration. In general, the form of X-ray spectra in both single and binary stars is likely to be determined principally by the amount of post-shock electron heating: magnetically confined X-ray plasma in binary systems can evolve further towards the higher electron temperatures of equilibrium while in single stars this does not take place. The long mean-free path for Coulomb energy exchange between fast-moving ions may also inhibit the development of line-driven instabilities.
No associations
LandOfFree
A new paradigm for the X-ray emission of O stars from XMM-Newton observations of the O9.7 supergiant zeta Orionis does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A new paradigm for the X-ray emission of O stars from XMM-Newton observations of the O9.7 supergiant zeta Orionis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A new paradigm for the X-ray emission of O stars from XMM-Newton observations of the O9.7 supergiant zeta Orionis will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-4777