Keck Spectroscopy of Millisecond Pulsar J2215+5135: a Moderate-MₙS, High-Inclination Binary

Original · EN

We present Keck spectroscopic measurements of the millisecond pulsar binary J2215+5135. These data indicate a neutron-star (NS) mass MₙS=1.6Mo, much less than previously estimated. The pulsar heats the companion face to TD 9000K; the large heating efficiency may be mediated by the intrabinary shock dominating the X-ray light curve. At the best-fit inclination i=88.8deg, the pulsar should be eclipsed. We find weak evidence for such eclipses in the pulsed gamma-rays; an improved radio ephemeris allows use of up to 5 times more Fermi-LAT gamma-ray photons for a definitive test of this picture. If confirmed, the gamma-ray eclipse provides a novel probe of the dense companion wind and the pulsar magnetosphere.