PREPRINT
7B628320-ECBC-4844-91B0-DE05EB53B14B

Revisiting the Sch\"{o}nberg-Chandrasekhar limit in post main sequence stellar evolution

Shaswata Chowdhury and Tapobrata Sarkar

Submitted on 15 September 2022

Abstract

The Sch\"{o}nberg-Chandrasekhar limit in post main sequence evolution for stars of masses in the range $1.4\lesssim M/{M}_{\odot }\lesssim 6$ gives the maximum pressure that the stellar core can withstand, once the central hydrogen is exhausted. It is usually expressed as a quadratic function of $1/\alpha$, with $\alpha$ being the ratio of the mean molecular weight of the core to that of the envelope. Here, we revisit this limit in scenarios where the pressure balance equation in the stellar interior may be modified, and in the presence of small stellar pressure anisotropy, that might arise due to several physical phenomena. Using numerical analysis, we derive a three parameter dependent master formula for the limit, and discuss various physical consequences. As a byproduct, in a limiting case of our formula, we find that in the standard Newtonian framework, the Sch\"{o}nberg-Chandrasekhar limit is best fitted by a polynomial that is linear, rather than quadratic, to lowest order in $1/\alpha$.

Preprint

Comment: 12 Pages, 5 figures

Subjects: Astrophysics - Solar and Stellar Astrophysics; General Relativity and Quantum Cosmology