Statistical and polarization properties of giant pulses of the millisecond pulsar B1937+21

TL;DR

This study analyzes the polarization and statistical properties of giant pulses from pulsar B1937+21, revealing their random polarization behavior, power-law energy distribution, and implications for models involving magnetic reconnection.

Contribution

It provides high-resolution observational data on GPs, highlighting their polarization randomness and energy distribution, and constrains physical models of pulsar emission mechanisms.

Findings

GPs show random polarization with no preferred PA.

Energy distribution follows a broken power law with indices -2.4 and -1.6.

Scattering masks intrinsic pulse shapes, with variable smearing times.

Abstract

We have studied the statistical and polarization properties of giant pulses (GPs) emitted by the millisecond pulsar B1937+21, with high sensitivity and time resolution. The observations were made in June 2005 with the 100-m Robert C. Byrd Green Bank Telescope at S-band (2052-2116 MHz) using the Mk5A VLBI recording system, with formal time resolution of 16 ns. The total observing time was about 4.5 hours; the rate of detection of GPs was about 130 per hour at the average longitudes of the main pulse (MPGPs) and 60 per hour at the interpulse (IPGPs). While the average profile shows well-defined polarization behavior, with regular evolution of the linear polarization position angle (PA), GPs exhibit random properties, occasionally having high linear or circular polarization. Neither MPGPs nor IPGPs show a preferred PA. The cumulative probability distribution (CPD) of GP pulse energy was constructed down to the level where GPs merge with regular pulses and noise. For both MPGPs and IPGPs, the CPD follows a power law with a break, the power index changing from -2.4 at high energy to -1.6 for low energy. Pulse smearing due to scattering masks the intrinsic shape and duration of the detected GPs. The smearing time varied during the observing session within a range of a few hundred nanoseconds. The measured polarization and statistical properties of GPs impose strong constraints on physical models of GPs. Some of these properties support a model in which GPs are generated by the electric discharge caused by magnetic reconnection of field lines connecting the opposite magnetic poles of a neutron star.