Study of Eclipses for Redback Pulsar J1227–4853

Abstract

Abstract We present a multifrequency study of eclipse properties of a transitional redback millisecond pulsar J1227−4853 discovered in 2014 with the GMRT. Emission from this pulsar is eclipsed at 607 MHz for about 37% of its orbit around the superior conjunction. We observe eclipse ingress and egress transitions that last for 12% and 15% of its orbit, respectively, resulting in only 36% of the orbit being unaffected by eclipsing material. We report an excess dispersion measure (DM) at eclipse boundaries of 0.079(3) pc cm−3, and the corresponding electron column density (N e ) is 24.4(8) × 1016 cm−2. Simultaneous timing and imaging studies suggest that the eclipses in J1227−4853 are not caused by temporal smearing due to excess dispersion and scattering but could be caused by removal of pulsar flux due to cyclotron absorption of the pulsed signal by intra-binary material constraining the companion’s magnetic field. Additionally, near the inferior conjunction at orbital phases 0.71 and 0.82 the pulsed emission is significantly delayed, which is associated with a fading of the pulsed and continuum flux densities. At orbital phase ∼0.82, we measure a change in DM of 0.035(3) pc cm−3 and N e of 10.8(8) × 1016 cm−2 associated with a dimming of up to ∼30% of the peak flux density. Such flux fading around a fixed orbital phase is not reported for other eclipsing binaries. Moreover, this event around the inferior conjunction could be caused by absorption of the pulsed signal by fragmented blobs of plasma generated from mass loss through the L2 Lagrangian point.