Constraints on the space density of intermediate polars from the   Swift-BAT survey
  We construct a complete, hard X-ray flux-limited sample of intermediate polars (IPs) from the Swift-BAT 70-month survey, by imposing selection cuts in flux and Galactic latitude ($F_X > 2.5 \times 10^{-11}\,\mathrm{erg\,cm^{-2}s^{-1}}$ at 14--195~keV, and $|b|>5^\circ$). We then use it to estimate the space density ($\rho$) of IPs. Assuming that this sample of 15 long-period systems is representative of the intrinsic IP population, the space density of long-period IPs is $1^{+1}_{-0.5} \times 10^{-7}\,\mathrm{pc^{-3}}$. The Swift-BAT data also allow us to place upper limits on the size of a hypothetical population of faint IPs that is not included in the flux-limited sample. While most IPs detected by BAT have 14--195~keV luminosities of $\sim 10^{33} {\rm erg s^{-1}}$, there is evidence of a fainter population at $L_X \sim 10^{31} {\rm erg s^{-1}}$. We find that a population of IPs with this luminosity may have a space density as large as $5\times 10^{-6}\,\mathrm{pc^{-3}}$. Furthermore, these low-luminosity IPs, despite appearing rare in observed samples, are probably at least as intrinsically common as the brighter systems that are better represented in the known IP sample. 
Magaretha L. Pretorius and Koji Mukai
astro-ph.SR astro-ph.HE