Paul W. Guilbert, A. C. Fabian, Susan Stepney.
Electron-ion coupling in rapidly varying sources.

Monthly Notices of the Royal Astronomical Society, 199:19P-21P, 1982.

Summary:

The Thomson depth of sources radiating at the efficiency limit must lie near unity. This allows us to deduce a general condition on the maximum electron temperature attainable in such a source via two-body relaxation; \(kT_e < 22\) keV. The application of this result to the rapid variability observed in NGC 6814 and Cygnus X-l and to NGC 4151 is discussed.

@journal(SS-MNRAS-199,
  author = "Paul W. Guilbert and A. C. Fabian and Susan Stepney",
  title = "Electron-ion coupling in rapidly varying sources",
  journal = "Monthly Notices of the Royal Astronomical Society",
  volume = 199,
  pages = "19P--21P",
  year = 1982
)