2009/06/03 by Yu. A. Fadeyev
Physics and Astronomy · #Adiabatic process #Amplitude #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Instability #Mechanics #Physics #Quantum mechanics #Stars #Stellar, planetary, and galactic studies #astro-ph.SR
paper · pdf · doi:10.1134/s1063773710050075
14 pages, 5 figures, submitted to Astronomy Letters
arxiv created 2009/06/03 · openalex publication_date 2010/05/01 · arxiv updated 2015/05/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Hydrodynamic calculations of nonlinear radial oscillations of LBV stars with effective temperatures 1.5 × 104 K ⩽ T eff ⩽ 3 × 104 K and luminosities 1.2 × 106 L ⊙ ⩽ L ⩽ 1.9 × 106 L ⊙ have been performed. Models for the evolutionary sequences of Population I stars (X = 0.7, Z = 0.02) with initial masses 70M ⊙ ⩽ M ZAMS ⩽ 90M ⊙ at the initial helium burning stage have been used as the initial conditions. The radial oscillations develop on a dynamical time scale and are nonlinear traveling waves propagating from the core boundary to the stellar surface. The amplitude of the velocity variations for the outer layers is several hundred km s−1, while the bolometric magnitude variations are within ΔM bol ⩽ 0 · 2. The onset of oscillations is not related to the κ-mechanism and is attributable to the instability of a self-gravitating envelope gas whose adiabatic index is close to its critical value of Γ1 = 4/3 due to the dominant contribution of radiation in the internal energy and pressure. The interval of magnitude variation periods (6 days ≤ II ≤ 31 days) encompasses all currently available estimates of the microvariability periods for LBV stars, suggesting that this type of nonstationarity is pulsational in origin.