SiO maser emission in Miras

M. D. Gray, M. Wittkowski, M. Scholz, E. M.L. Humphreys, K. Ohnaka, D. Boboltz

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)


We describe a combined dynamic atmosphere and maser propagation model of SiO maser emission in Mira variables. This model rectifies many of the defects of an earlier model of this type, particularly in relation to the infrared (IR) radiation field generated by dust and various wavelength-dependent, optically thick layers. Modelled masers form in rings with radii consistent with those found in very long baseline interferometry (VLBI) observations and with earlier models. This agreement requires the adoption of a radio photosphere of radius approximately twice that of the stellar photosphere, in agreement with observations. A radio photosphere of this size renders invisible certain maser sites with high amplification at low radii, and conceals high-velocity shocks, which are absent in radio continuum observations. The SiO masers are brightest at an optical phase of 0.1-0.25, which is consistent with observed phase lags. Dust can have both mild and profound effects on the maser emission. Maser rings, a shock and the optically thick layer in the SiO pumping band at 8.13 μm appear to be closely associated in three out of four phase samples.

Original languageEnglish
Pages (from-to)51-66
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - Mar 2009
Externally publishedYes


  • Circumstellar matter
  • Masers
  • Radio lines: stars
  • Stars: AGB and post-AGB
  • Stars: evolution

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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