2015/04/30 by Lilia Ferrario, D. de Martino, Domitilla de Martino +2 · 8 citations
Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Gamma-ray bursts and supernovae #Magnetic field #Physics #Stars #Stellar, planetary, and galactic studies #White dwarf #Zeeman effect #astro-ph.SR
paper · pdf · doi:10.1007/s11214-015-0152-0
73 pages, 22 figures, 2 large tables. Invited review chapter on Magnetic White Dwarfs to appear in Space Science Reviews, Springer
arxiv created 2015/04/30 · openalex publication_date 2015/05/11 · arxiv updated 2015/06/03 · openalex created_date 2020/11/23 · openalex updated_date 2026/08/05
In this paper we review the current status of research on the observational and theoretical characteristics of isolated and binary magnetic white dwarfs (MWDs). Magnetic fields of isolated MWDs are observed to lie in the range 103-109G. While the upper limit cutoff appears to be real, the lower limit is more difficult to investigate. The incidence of magnetism below a few 103G still needs to be established by sensitive spectropolarimetric surveys conducted on 8m class telescopes. Highly magnetic WDs tend to exhibit a complex and non-dipolar field structure with some objects showing the presence of higher order multipoles. There is no evidence that fields of highly magnetic WDs decay over time, which is consistent with the estimated Ohmic decay times scales of ~1011 yrs. MWDs, as a class, also appear to be more massive than their weakly or non-magnetic counterparts. MWDs are also found in binary systems where they accrete matter from a low-mass donor star. These binaries, called magnetic Cataclysmic Variables (MCVs) and comprise about 20-25% of all known CVs. Zeeman and cyclotron spectroscopy of MCVs have revealed the presence of fields in the range ∼ 7-230 MG. Complex field geometries have been inferred in the high field MCVs (the polars) whilst magnetic field strength and structure in the lower field group (intermediate polars, IPs) are much harder to establish. The origin of fields in MWDs is still being debated. While the fossil field hypothesis remains an attractive possibility, field generation within the common envelope of a binary system has been gaining momentum, since it would explain the absence of MWDs paired with non-degenerate companions and also the lack of relatively wide pre-MCVs.