On the long and short nulls, modes and interpulse emission of radio pulsar B1944+17

TL;DR

This study analyzes pulsar B1944+17's nulling behavior, mode changes, polarization, and geometry, revealing nearly aligned rotation, distinct null types, and complex emission modes with drifting subpulses.

Contribution

It provides detailed single pulse analysis, polarization data, and geometric modeling, uncovering the pulsar's nearly aligned geometry and the nature of its nulls and emission modes.

Findings

70% nulling with nulls at mode boundaries

Four emission modes with drifting subpulses

Nearly aligned rotator with 2-degree magnetic inclination

Abstract

We present a single pulse study of pulsar B1944+17, whose non-random nulls dominate nearly 70% of its pulses and usually occur at mode boundaries. When not in the null state, this pulsar displays four bright modes of emission, three of which exhibit drifting subpulses. B1944+17 displays a weak interpulse whose position relative to the main pulse we find to be frequency independent. Its emission is nearly 100% polarized, its polarization-angle traverse is very shallow and opposite in direction to that of the main pulse, and it nulls approximately two-thirds of the time. Geometric modeling indicates that this pulsar is a nearly aligned rotator whose alpha value is hardly 2 degrees--i.e., its magnetic axis is so closely aligned with its rotation axis that its sightline orbit remains within its conal beam. The star's nulls appear to be of two distinct types: those with lengths less than about 8 rotation periods appear to be pseudonulls--that is, produced by "empty" sightline traverses through the conal beam system; whereas the longer nulls appear to represent actual cessations of the pulsar's emission engine.