2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/10560We introduce a simple and convenient fitting formula for the thermal annihilation line from pair plasmas in cosmic sources. The fitting formula is accurate to 0.04\% and is valid at all photon energies and temperatures of interest. The commonly used Gaussian line profile is not a good approximation for broader lines.4 pages; l-aa style; 2 postscript figures; Proceedings of 3rd Compton Gamma-Ray Observatory Symposium, Munich, 1995Astrophysicstext