Hot DQ White Dwarf Stars: A New Challenge to Stellar Evolution

TL;DR

This paper reports the discovery of a new class of hydrogen-deficient white dwarf stars with carbon-dominated atmospheres, challenging existing stellar evolution theories and suggesting a new post-AGB evolutionary sequence.

Contribution

It introduces a novel class of white dwarfs with unique atmospheric compositions that do not align with current post-AGB evolution models.

Findings

Discovery of hydrogen-deficient, carbon-rich white dwarfs.

Atmospheric parameters inconsistent with known theories.

Potential link to the PG 1159 star H1504+65.

Abstract

We report the discovery of a new class of hydrogen-deficient stars: white dwarfs with an atmosphere primarily composed of carbon, with little or no trace of hydrogen or helium. Our analysis shows that the atmospheric parameters found for these stars do not fit satisfactorily in any of the currently known theories of post-asymptotic giant branch (AGB) evolution, although these objects might be the cooler counter-part of the unique and extensively studied PG 1159 star H1504+65. These stars, together with H1504+65, might thus form a new evolutionary post-AGB sequence.