Viscous excretion discs around Be stars

Umin Lee, Hideyuki Saio, Yoji Osaki

Research output: Contribution to journalArticlepeer-review

183 Citations (Scopus)


We discuss the properties of geometrically thin viscous Keplerian excretion discs around Be stars. The inner boundary of the disc is assumed to be located at the equatorial surface of the central star. We assume that angular momentum is transferred by some mechanism from the interior to the equatorial surface of the central star and hence matter is supplied at the inner boundary of the disc at a certain rate (excretion rate). The matter drifts outward in the disc because the angular momentum of the matter is exchanged by the effect of viscous stress. For mass excretion rates similar to the mass-loss rate estimated for Be stars, the irradiative heating by the central star is as important for the disc structure as the viscous heating in the disc. Although the irradiative heating has a stabilizing effect on thermal instability which is familiar in accretion discs in dwarf novae, we show that the irradiated excretion discs around Be stars have a thermally unstable region when the mass excretion rate is ∼ 10-7 M/yr-1. The inner part of the disc is optically thick, while the outer low temperature region (Teff ≲ 7000 K) is optically thin. The optically thick region is larger for a larger excretion rate.

Original languageEnglish
Pages (from-to)432-437
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 1991 May 1
Externally publishedYes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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