1995A&A...296..117V

We have computed static mass-radius relations for low-mass white dwarfs defined by surface gravities in the range g=10⁷-10⁸cm/s². We have assumed pure helium interiors without a hydrogen envelope and carbon interiors with and without a hydrogen envelope. Surface boundary conditions also assume non-zero effective temperatures at 49,000≤T_eff≤61,000K. Although generally applicable to isolated low-mass white dwarfs, these models are particularly interesting for the interpretation of the class of low-mass He white dwarfs that potentially emerge from close binary evolution. We discuss in particular the case of Feige 24 for which Vennes & Thorstensen (1994AJ....108.1881V) have proposed a low mass and large radius based on their gravitational redshift measurement. The binary parameters of Feige 24 are consistent with the population of He white dwarf + red dwarf close binaries predicted by theory but also with a population having a more common carbon interior with a thick hydrogen envelope. We demonstrate that a thin hydrogen layer is unlikely.