2006/10/27 by Gary D. Schmidt, Paula Szkody, Arne Henden +4 · 2 citations
Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Gamma-ray bursts and supernovae #Intermediate polar #Magnetic field #Physics #Roche lobe #Sky #Stars #Stellar, planetary, and galactic studies #White dwarf #astro-ph
paper · pdf · doi:10.1086/509613
published as Astrophys.J.654:521-526,2006 · 6 pages, 5 figures
arxiv created 2006/10/27 · openalex publication_date 2006/12/29 · arxiv updated 2014/10/13 · openalex created_date 2022/09/04 · openalex updated_date 2026/05/22
Two new magnetic white dwarf accretion binaries with extremely low mass-transfer rates have been discovered in the course of the Sloan Digital Sky Survey.Measured magnetic fields are 42 MG and 57 MG, and one system orbits with a period of just 82 min.The new systems therefore significantly expand the range in properties exhibited by the small class.The measured accretion rates are very low, 0.6 -5 × 10 -13 M ⊙ yr -1 , and multiple visits spanning more than a year confirm that this is not a short-lived characteristic.It is becoming increasingly clear that the low-Ṁ magnetic white dwarf binaries accrete by nearly complete magnetic capture of the stellar wind from the secondary star rather than by Roche lobe overflow.The accretion rates therefore provide some of the first realistic estimates of the total wind loss rates from M dwarfs.Although one or more of the eight systems known to date may be interrupted or possibly even extinct Polars, several lines of evidence suggest that most are pre-Polars whose evolution has not yet brought the secondaries into contact with their Roche surfaces.Considering the difficulties of identifying binaries over a wide range in field strength and accretion rate, it is quite possible that the space density of wind-accreting magnetic binaries exceeds that of the classical X-ray emitting, Roche-lobe overflow Polars.