Theoretical growth rates, periods, and pulsation constants for long-period variables

Journal Article · Sun Aug 01 04:00:00 EDT 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/160160· OSTI ID:7042045

Fox, M W; Wood, P R

Theoretical values of the growth rate, period, and pulsation constant for the first three radial pulsation modes in red giants (Population II and galactic disk) and supergiants have been derived in the linear, nonadiabatic approximation. The effects of altering the surface boundary conditions, the effective temperature (or mixing length), and the opacity in the outer layers have been explored. In the standard models, the Q-value for the first overtone can be much larger (Q/sub 1/< or approx. =0.075) than indicated by previous isolated calculations (Q/sub 1/roughly-equal0.04); in addition, the Q-value for the fundamental mode is reduced from previous values, as is the period ratio P/sub 0//P/sub 1/. The growth rate for the fundamental mode is found to increase with luminosity on the giant branch while the growth rate for the first overtone decreases. Dynamical instabilities found in previous adiabatic models of extreme red giants do not occur when nonadiabatic effects are included in the models. In some massive, luminous models, period ratios P/sub 0//P/sub 1/approx.7 occur when P/sub 0/approx.2000--5000 days; it is suggested that the massive galactic supergiants and carbon stars which have secondary periods Papprox.2000--7000 days and primary periods Papprox.300--700 days are first-overtone pulsators in which the long secondary periods are due to excitation of the fundamental mode. Some other consequences of the present results are briefly discussed, with particular emphasis on the mode of pulsation of the Mira variables. Subject headings: stars: long-period variables: stars: pulsation: stars: supergiants

• Research Organization: Mount Stromlo and Siding Spring Observatories, Research School of Physical Sciences, The Australian National University
• OSTI ID: 7042045
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 259:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics &amp; Cosmology-- Stars &amp; Quasi-Stellar
Radio &amp; X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CONVECTION
GIANT STARS
MATHEMATICAL MODELS
MATHEMATICS
NUMERICAL ANALYSIS
OPACITY
OPTICAL PROPERTIES
OSCILLATION MODES
PHYSICAL PROPERTIES
PULSATIONS
RED GIANT STARS
STAR MODELS
STARS
SUPERGIANT STARS
VARIABLE STARS