Nature of SiO masers in late-type stars

Journal Article · Mon Sep 01 04:00:00 EDT 1980 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/158260· OSTI ID:6670223

Elitzur, M

It is shown that currently available theoretical models for SiO masers cannot explain all the recent observations, especially the maser emission from v=2 and v=3 states and the fact that the masers are observed in stars which cover a wide range of parameters, in particular mass loss rates. A new model for the SiO masers in late-type stars is therefore developed which differs from the commonly accepted picture in its two basic ingredients: (1) Unlike previous models, the proposed pump mechanism is based upon collisions rather than radiation and utilizes properties of the collision cross sections discussed elsewhere. (2) Rather than locating the masers in the expanding circumstellar shell, I suggest that the emission of strong maser spikes has its origin in material in the upper atmosphere of the star. This material takes part in large mass motions which have been the subject of numerous recent observational and theoretical studies, unrelated to SiO masers. Various features of the SiO maser spikes are particularly suggestive of the picture of large convective cells in the photospheres of red giants and supergiants, recently advocated by Schwarzschild. The model provides simple explanations for many of the observed features of SiO masers, in particular the morphology of the emission profiles, time variability, and polarization.

• Research Organization: Department of Astronomy, University of Illinois at Urban-Champaign
• OSTI ID: 6670223
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 240:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMPLIFIERS
ATMOSPHERES
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
CHALCOGENIDES
COLLISIONS
DECAY
ELECTROMAGNETIC PARTICLE DECAY
ELECTRONIC EQUIPMENT
EMISSION
ENERGY LEVELS
ENERGY-LEVEL DENSITY
ENERGY-LEVEL TRANSITIONS
EQUIPMENT
EXCITATION
EXCITED STATES
GIANT STARS
LINE WIDTHS
MASERS
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
OXIDES
OXYGEN COMPOUNDS
PARTICLE DECAY
POLARIZATION
RADIATIVE DECAY
RED GIANT STARS
SILICON COMPOUNDS
SILICON OXIDES
STARS
STELLAR ATMOSPHERES
SUPERGIANT STARS
VIBRATIONAL STATES
WEAK PARTICLE DECAY