Isolated neutron stars from Rosat and Swift

Independent of X-ray spectrum and variability, the number of INSs is <=48 (90% confidence). Restricting attention to soft (kT_eff_<200eV), non-variable X-ray sources -as in a previous study- yields an all-sky limit of <=31 INSs.

In the course of our analysis, we identify five new high-quality INS candidates for targeted follow-up observations. A future all-sky X-ray survey with eROSITA, or another mission with similar capabilities, can be expected to increase the detected population of X-ray-discovered INSs from the 8-50 in the BSC, to (for a disk population) 240-1500, which will enable a more detailed study of neutron star population models.