2008/02/24 by Tamara W. Reimer, William F. Welsh, Koji Mukai +2
Earth and Planetary Sciences · Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Cataclysmic variable star #Dwarf nova #Gamma-ray bursts and supernovae #High-pressure geophysics and materials #Intermediate polar #Orbital period #Photometry (optics) #Physics #Polar #Stars #White dwarf #astro-ph
paper · pdf · doi:10.1086/587043
To be published in The Astrophysical Journal
arxiv created 2008/02/24 · openalex publication_date 2008/04/28 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present optical and X-ray time series photometry of EI UMa that reveal modulation at 746 and 770 s, which we interpret as the white dwarf spin and spin-orbit sidebands. These detections, combined with previous X-ray studies, establish EI UMa as an intermediate polar. We estimate the mass accretion rate to be ~3.6 × 10 17 g s −1 , which is close to, and likely greater than, the critical rate above which dwarf nova instabilities are suppressed. We also estimate the white dwarf to have a large magnetic moment μ > (3.4 ± 0.2) × 10 33 G cm 3 . The high mass accretion rate and magnetic moment imply the existence of an accretion ring rather than a disk, and along with the relatively long orbital period, these suggest that EI UMa is a rare example of a prepolar cataclysmic variable.