Publication Abstracts

Stothers and Chin 1983

Stothers, R., and C.-W. Chin, 1983: Possible mechanisms for the Hubble-Sandage (S Doradus) variables. Astrophys. J., 264, 583-593, doi:10.1086/160628.

The brightest nonexplosive stars known at present are the Hubble-Sandage (or S Doradus) variables. It is generally assumed that these objects consist of intrinsically luminous, massive stars embedded in clouds of circumstellar gas and dust. The unexplained long-term variability of their light is investigated in the present paper in terms of the following possible mechanisms: (1) episodic, nearly catastrophic mass loss, perhaps accompanied by temporary shrinkage of the stellar radius, in a luminous supergiant; (2) flickering of a hydrogen-burning or helium-burning shell; (3) hydrogen flashing in an evolved stellar core; (4) pulsation of a luminous supergiant envelope near the Eddington limit of radiative stability; (5) pulsation of a dense circumstellar gas or dust cloud; (6) overturning of giant convection cells (or some other kind of nonradial oscillation) ina luminous supergiant envelope; or (7) vibrational instability and mass outflow in an extremely massive main-sequence star. Among these suggestions, the second and third can be almost definitely ruled out, while the sixth and seventh ones are also rather unlikely.

Preference is given here to the notion that a sudden, massive outflow of matter may sometimes occur from the surface of an evolved supergiant of very high mass. Model calculations indicate that such a star can temporarily become quite blue and visually much fainter, although the bolometric light output of the star remains nearly constant. If the ejected cloud of matter is optically thick, the object as a whole may appear redder and hence also visually fainter (as Davidson originally suggested). In both cases, the observed sharp declines light and very slow recoveries can be adequately accounted for To explain the peculiar light oscillations with "periods" of 3-10 yr, we suggest that, if they are not simply due to rapidly recurring mass outflows, then either the stellar envelope (if the luminosity lies close to the Eddington limit) or the circumstellar cloud (if it is optically thick enough) may be undergoing bulk radial pulsations in the fundamental mode. Perhaps the outward mass flux from the star (or whatever causes this flux) drives the pulsations.

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BibTeX Citation

  author={Stothers, R. and Chin, C.-W.},
  title={Possible mechanisms for the Hubble-Sandage (S Doradus) variables},
  journal={Astrophysical Journal},

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RIS Citation

ID  - st01810u
AU  - Stothers, R.
AU  - Chin, C.-W.
PY  - 1983
TI  - Possible mechanisms for the Hubble-Sandage (S Doradus) variables
JA  - Astrophys. J.
JO  - Astrophysical Journal
VL  - 264
SP  - 583
EP  - 593
DO  - 10.1086/160628
ER  -

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