Hot Accretion onto White Dwarfs in Quiescent Dwarf Novae

Abstract

We present dynamically consistent solutions for hot accretion onto unmagnetized, rotating white dwarfs (WDs) in five quiescent dwarf novae. The measured WD rotation rates (and other system parameters) in RX And, SS Cyg, U Gem, VW Hyi and WZ Sge imply spindown of the WD by an extended hot flow emitting most of its X-rays in the vicinity of the stellar surface. In general, energy advection is absent and the flow is stable to convection and hydrodynamical outflows. In rapidly rotating systems, the X-ray luminosity provides only an upper limit on the quiescent accretion rate because of substantial stellar spindown luminosity. We suggest that the presence of hot flows in quiescent dwarf novae may limit the long-term WD rotation rates to significantly sub-Keplerian values.

7 pages, 2 eps figures. Accepted to ApJL

References in corpus (1)

• The disc instability model of dwarf-novae and low-mass X-ray binary transients

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