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

#### 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
)