Quasi-stars, giants and the Schönberg-Chandrasekhar limit

Abstract

The Schönberg-Chandrasekhar (SC) limit is a well-established result in the understanding of stellar evolution. It provides an estimate of the point at which an evolved isothermal core embedded in an extended envelope begins to contract. We investigate contours of constant fractional mass in terms of homology invariant variables U and V and find that the SC limit exists because the isothermal core solution does not intersect all the contours for an envelope with polytropic index 3. We find that this analysis also applies to similar limits in the literature including the inner mass limit for polytropic models of quasi-stars. Consequently, any core solution that does not intersect all the fractional mass contours exhibits an associated limit and we identify several relevant cases where this is so. We show that a composite polytrope is at a fractional core mass limit when its core solution touches but does not cross the contour of the corresponding fractional core mass. We apply this test to realistic models of helium stars and find that stars typically expand when their cores are near a mass limit. Furthermore, it appears that stars that evolve into giants have always first exceeded an SC-like limit.

9 pages, 7 figures, published in MNRAS. Updated to (more closely) match published version

References in corpus (2)

• Formation of Supermassive Black Holes by Direct Collapse in Pregalactic Halos
• Quasistars: Accreting black holes inside massive envelopes

Cited by in corpus (17)

• Titans of the Early Universe: The Prato Statement on the Origin of the First Supermassive Black Holes
• Initial mass function of intermediate mass black hole seeds
• Massive black hole factories: Supermassive and quasi-star formation in primordial halos
• Structure and evolution of high-mass stellar mergers
• How realistic UV spectra and X-rays suppress the abundance of direct collapse black holes
• A UV flux constraint on the formation of direct collapse black holes
• Magnetic fields during the formation of supermassive black holes
• The X-ray binary GX 339-4/V821 Ara: the distance, inclination, evolutionary status and mass transfer
• The formation of massive primordial stars in the presence of moderate UV backgrounds
• Numerical experiments to help understand cause and effect in massive star evolution
• Little Red Dots As Late-stage Quasi-stars
• Bright vigorous winds as signposts of supermassive black hole birth
• Effects of turbulence and rotation on protostar formation as a precursor to seed black holes
• Force-feeding Black Holes
• Light or heavy supermassive black hole seeds: the role of internal rotation in the fate of supermassive stars
• Quasi-star jets as unidentified gamma-ray sources
• The Schönberg-Chandrasekhar limit in presence of small anisotropy and modified gravity