Oscillatory secular modes: the thermal micropulses

• Autores: Gautschy, Alfred; Althaus, Leandro Gabriel
• Año de publicación: 2007
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: White dwarfs; AGB stars; Post AGB stars; Interior stars; Oscillations of stars
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Aims. Stars in the narrow mass range of about 2.5 and 3.5 M can develop a thermally unstable He-burning shell during its ignition phase. We study, from the point of view secular stability theory, these so-called thermal micropulses and investigate their properties; the thermal pulses constitute a convenient conceptual laboratory to look thoroughly into the physical properties of a helium-burning shell during the whole thermally pulsing episode. Methods. Linear stability analyses were performed on a large number of 3 M star models toward the end of their core helium-burning and the beginning of the double shell burning phase. The stellar models were not assumed to be in thermal equilibrium. Results. The thermal mircopulses – and we conjecture all other thermal pulse episodes encountered by shell burning stars – can be understood as the nonlinear finite-amplitude realization of an oscillatory secular instability that prevails during the whole thermal pulsing episode. Hence, the cyclic nature of the thermal pulses can be traced back to a linear instability concept.
Fil: Gautschy, Alfred. No especifica;
Fil: Althaus, Leandro Gabriel. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina