2014MNRAS.442.2580P

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 (FX > 2.5x10^- 11^erg/cm2/s at 14-195 keV, and {verbar}b{verbar} > 5°). We then use it to estimate the space density (ρ) 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 ×10^-7 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 Swift-BAT have 14-195 keV luminosities of ∼ 10³³erg/s, there is evidence of a fainter population at LX ∼ 10³¹erg/s. We find that a population of IPs with this luminosity may have a space density as large as 5x10^–6/pc3. 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.