XMM-Newton Observes the Intrabinary Shock of PSR J1959+2048

In a multi-orbit (100 ks) XMM-Newton exposure of the original black widow pulsar, PSR J1959+2048, we measure the strong orbital modulation caused by intrabinary shock (IBS) emission. The IBS light curve peak appears asymmetric, which we attribute to sweep-back effects in the companion wind. We also see evidence for an X-ray eclipse by the companion and its wind. Together with the IBS fit, this supports an edge-on i ∼ 90° view of the system and a modest ∼1.8 M⊙ mass for the recycled pulsar. Our IBS fit parameters imply a wind flux that, if persistent, would evaporate the companion within a few Gyr.