The Eddington Limit and Soft Gamma Repeaters

Abstract

Observed intensities and inferred distances of soft gamma repeaters imply luminosities in excess of the nominal (electron-scattering opacity) Eddington limit by four to six orders of magnitude. I review the physical basis of this limit. Accretional luminosities may exceed it if energy is hydrodynamically coupled from accreting matter to closed field lines where it forms a pair gas. This magnetically confined pair gas radiates roughly a black body spectrum with $k_B T_e \approx 23$ KeV, consistent with observations, at a luminosity up to $\sim 3 \times 10^{44}$ erg s$^{-1}$ for a surface field of $10^{13}$ gauss. Magnetic transparency is not required. I discuss the minutes-long continuing emission of March 5, 1979, steady counterparts to SGR, their spin periods and the recoil problem.