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Astrophysical Masers. I. Source Size and Saturation

1972; IOP Publishing; Volume: 174; Linguagem: Inglês

10.1086/151514

1538-4357

Peter Goldreich, Douglas A. Keeley,

Astro and Planetary Science

view Abstract Citations (156) References (2) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Astrophysical Masers. I. Source Size and Saturation Goldreich, Peter ; Keeley, Douglas A. Abstract The relation between the apparent and actual sizes of maser sources is important in determining their internal physical conditions. This relation is investigated for models of homogeneous maser clouds having spherical and tube-shape geometries. It is found that the apparent linear size of a spherical OH or H2O maser may be as much as two orders of magnitude smaller than the physical extent of the emitting cloud. On the other hand, the observed size of a maser having the shape of a thick tube is given by its transverse dimensions. The treatment of maser radiation uses rate equations for the level populations and the ordinary equation of transfer. Approximate analytic calculations are presented for all degrees of saturation. The theory is developed in terms of a multilevel scalar atom in which only two levels are coupled by the maser radiation. Thus, the effects of hyperfine splitting and polarization are ignored. Publication: The Astrophysical Journal Pub Date: June 1972 DOI: 10.1086/151514 Bibcode: 1972ApJ...174..517G full text sources ADS |