Semiregular variable stars. (arXiv:1812.07185v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kudashkina_L/0/1/0/all/0/1">L. S. Kudashkina</a>
The studies of semiregular variables of stars by different authors are
considered, and the main theoretical and observational problems associated with
these stars are reviewed. Their evolutionary status and possible connection
with long-period variables such as Mira Ceti are discussed. Individual objects
belonging to different types of semiregular variables are described in detail.
After leaving the main sequence, the stars pass through the region of
instability of Cepheids, turning into radially pulsating variables of type
delta Cephei. These stars can be associated with semiregular variables giants
and supergiants of spectral classes F-K, which are usually denoted by the
symbol SRd. In the process of further evolution of the variables of high
luminosity fall in the region of red supergiants, becoming the type variables
SRc (or Lc), and the variables lower luminosity turn into a semiregular
variables SRab (or wrong Lb) of late spectral classes. Variables of the RV Tau
type are a class of low-mass (with masses of the order of one solar) pulsating
F-K-supergiants, which may be at the short-term evolutionary stage of
transition from the red giant to the protoplanetary nebula, which explains the
small number of stars of this type of variability. Shklovsky (1956) was the
first to point to stars of this type as the progenitors of planetary nebulae.
The studies of semiregular variables of stars by different authors are
considered, and the main theoretical and observational problems associated with
these stars are reviewed. Their evolutionary status and possible connection
with long-period variables such as Mira Ceti are discussed. Individual objects
belonging to different types of semiregular variables are described in detail.
After leaving the main sequence, the stars pass through the region of
instability of Cepheids, turning into radially pulsating variables of type
delta Cephei. These stars can be associated with semiregular variables giants
and supergiants of spectral classes F-K, which are usually denoted by the
symbol SRd. In the process of further evolution of the variables of high
luminosity fall in the region of red supergiants, becoming the type variables
SRc (or Lc), and the variables lower luminosity turn into a semiregular
variables SRab (or wrong Lb) of late spectral classes. Variables of the RV Tau
type are a class of low-mass (with masses of the order of one solar) pulsating
F-K-supergiants, which may be at the short-term evolutionary stage of
transition from the red giant to the protoplanetary nebula, which explains the
small number of stars of this type of variability. Shklovsky (1956) was the
first to point to stars of this type as the progenitors of planetary nebulae.
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