A Pilot Study of Nulling in 22 Pulsars Using Mixture Modeling

TL;DR

This study introduces a robust mixture modeling approach to analyze pulsar nulling, revealing biases in previous methods, providing nulling fractions for 22 pulsars, and uncovering potential periodicity in nulls.

Contribution

It presents a new probabilistic method for studying pulsar nulling, improving accuracy over traditional algorithms, and offers new nulling data and timing parameters for 22 pulsars.

Findings

Demonstrates biases in previous nulling estimation methods.

Provides nulling fractions for 22 pulsars for the first time.

Finds evidence of periodic nulling in some pulsars.

Abstract

The phenomenon of pulsar nulling, observed as the temporary inactivity of a pulsar, remains poorly understood both observationally and theoretically. Most observational studies that quantify nulling employ a variant of Ritchings (1976)'s algorithm which can suffer significant biases for pulsars where the emission is weak. Using a more robust mixture model method, we study pulsar nulling in a sample of 22 recently discovered pulsars, for which we publish the nulling fractions for the first time. These data clearly demonstrate biases of the former approach and show how an otherwise non-nulling pulsar can be classified as having significant nulls. We show that the population-wide studies that find a positive correlation of nulling with pulsar period/characteristic age can similarly be biased because of the bias in estimating the nulling fraction. We use our probabilistic approach to find the evidence for periodicity in the nulls in a subset of three pulsars in our sample. In addition, we also provide improved timing parameters for 17 of the 22 pulsars that had no prior follow-up.