2017ApJ...851...61R

We describe new measurements of the remarkable Hα/UV/X-ray bow shock and pulsar wind nebula (PWN) of the isolated millisecond pulsar (MSP) PSR J2124-3358. Chandra X-ray Observatory imaging shows a one-sided jet structure with a softer equatorial outflow. KOALA integral field unit spectroscopy shows that non-radiative emission dominates the bow shock and that the Hα nebula is asymmetric about the pulsar velocity with an elongation into the plane of the sky. We extend analytic models of the contact discontinuity to accommodate such shapes and compare these to the data. Using Hubble Space Telescope UV detections of the pulsar and bow shock, radio timing distance, proper motion measurements, and the CXO-detected projected spin axis, we model the 3D PWN momentum flux distribution. The integrated momentum flux depends on the ionization of the ambient ISM, but for an expected ambient warm neutral medium, we infer I=2.4×10⁴⁵ g cm². This implies M_NS=1.6–2.1 M_☉, depending on the equation of state, which in turn suggests that the MSP gained significant mass during recycling and then lost its companion. However, this conclusion is at present tentative, since lower ionization allows ∼30 % lower masses, and uncertainty in the parallax allows up to 50% error.