Resumen

TINOCO ARENAS, A.; GONZALEZ BOLIVAR, M.; MEDINA COVARRUBIAS, R.  y  RAGA, A. C.. Approximate analytic solutions for the ionization structure of a pressure equilibrium Strömgren sphere. Rev. mex. astron. astrofis [online]. 2015, vol.51, n.2, pp.239-244. ISSN 0185-1101.

We present analytic models for a photoionized region in pressure equilibrium with the surrounding, neutral material. The models are based on the assumption of a linear relation between the H ionization fraction and the square of the sound speed of the gas. We show that under these assumptions the "grey" radiative transfer equation has analytic solutions that provide the ionization structure and the density of the nebula as a function of radius.

Palabras llave : ISM [HII regions].