2021/01/29 by S. G. Parsons, B. T. Gänsicke, M. R. Schreiber +5 · 2 citations
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy #Astrophysics #Black dwarf #Brown dwarf #Cataclysmic variable star #Common envelope #Gamma-ray bursts and supernovae #Intermediate polar #Magnetic field #Magnetism #Massive compact halo object #Physics #Stars #Stellar classification #Stellar, planetary, and galactic studies #White dwarf #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stab284
Accepted for publication in MNRAS
arxiv created 2021/01/29 · openalex publication_date 2021/02/03 · arxiv updated 2021/02/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
ABSTRACT Magnitude-limited samples have shown that 20–25 per cent of cataclysmic variables contain white dwarfs with magnetic fields of Mega Gauss strength, in stark contrast to the approximately 5 per cent of single white dwarfs with similar magnetic field strengths. Moreover, the lack of identifiable progenitor systems for magnetic cataclysmic variables leads to considerable challenges when trying to understand how these systems form and evolve. Here, we present a sample of six magnetic white dwarfs in detached binaries with low-mass stellar companions where we have constrained the stellar and binary parameters including, for the first time, reliable mass estimates for these magnetic white dwarfs. We find that they are systematically more massive than non-magnetic white dwarfs in detached binaries. These magnetic white dwarfs generally have cooling ages of more than 1 Gyr and reside in systems that are very close to Roche lobe filling. Our findings are more consistent with these systems being temporarily detached cataclysmic variables, rather than pre-cataclysmic binaries, but we cannot rule out the latter possibility. We find that these systems can display unusual asymmetric light curves that may offer a way to identify them in larger numbers in future. Seven new candidate magnetic white dwarf systems are also presented, three of which have asymmetric light curves. Finally, we note that several newly identified magnetic systems have archival spectra where there is no clear evidence of magnetism, meaning that these binaries have been previously missed. Nevertheless, there remains a clear lack of younger detached magnetic white dwarf systems.