Atomic physics of shocked plasma in the winds of massive stars
1. Atomic physics of shocked plasma
in the winds of massive stars
Maurice Leutenegger
(NASA/GSFC/CRESST/UMBC)
David Cohen (Swarthmore College)
Stan Owocki (Bartol Research Institute)
2. Outline
● Background on winds of massive stars
● Mechanisms for x-ray emission
● Mass loss rate problem
● Background on x-ray observatories
● Doppler profile diagnostics
● He-like triplet diagnostics
● Special bonus problems: optically thick x-ray
radiative transfer in a supersonic flow; Fe XVII
line ratios
3. Massive stars
● Spectral type O, early B; T ~ 30-50 kK
● M ~ 30-120 Mʘ ; L bol~ 105 – 106 Lʘ
● Mass loss rates 10-7 – 10-5 Mʘ/year (compare to
sun at 10-14 Mʘ/year); v∞ ~ 2000 km/s
2 -3
● ½Ṁv ∞
~ 10 Lbol ; Lx ~ 10-7 Lbol
● TMS ~ few 10 Myr
4. Theory of radiatively driven winds
● Radiation pressure in spectral lines becomes
much more effective due to deshadowing of
optically thick lines in a supersonic flow
34. Summary
● X-ray emission from single O star winds can be
understood in terms of the embedded wind
shock paradigm
● Independent constraints can be placed on mass
loss rates by x-ray line shapes, leading to
downward revisions factors of 2-4 from
recombination/free-free diagnostics
● He-like triplet diagnostics constrain plasma
location and confirm the EWS paradigm
35. Summary
● Resonance scattering can symmetrize line
profile shapes; we know it is important from
comparisons of resonance and
intercombination lines from the same ion
● (If there is time, ask me about Fe XVII line
ratios!)