X-ray Emission from Accretion on to White Dwarfs

Abstract

We have extended calculations by Hoshi and by Aizu to produce a self-consistent model for X-radiation from accreting, possibly magnetized, white dwarfs. To generate keV X-rays the flow must be radial on to the stellar surface. We expect X-ray luminosities to be in the range |${10}^{32}-{10}^{36}\,\text{erg}\,\text{s}^{-1}$|⁠, and the spectra to be quasi-bremsstrahlung with |$kT\,\sim \,30-100\,\text{keV}$| and with a substantial low energy cut-off. The optical (bolometric) luminosity should be comparable to that emitted in the X-rays. If the white dwarf is magnetized a comparable, or greater, amount can be radiated as cyclotron emission in the infrared or optical.