Measuring the shock-heating rate in the winds of O stars using X-ray line spectra

摘要: We present a new method for using measured X-ray emission line fluxes from O stars to determine the shock-heating rate due instabilities in their radiation-driven winds. The high densities of these winds means that embedded shocks quickly cool by local radiative emission, while cooling expansion should be negligible. Ignoring simplicity any nonradiative mixing or conductive cooling, presented here exploits idea post-shock plasma systematically passes through temperature characteristic distinct lines spectrum. In this way, observed flux distribution among can used construct cumulative probability shock strengths typical wind parcel encounters as it advects wind. apply Chandra grating spectra five with indicative effectively single massive stars. results all are quite similar: average mass element roughly one heats at least 10 6 K wind, and is strongly decreasing function temperature, consistent negative power law index n ≈ 3, implying marginal scales T −4 , hints an even steeper decline cut-off above 7 K.