IQRM: real-time adaptive RFI masking for radio transient and pulsar searches

TL;DR

This paper introduces IQRM, a real-time, adaptive RFI masking algorithm for radio transient and pulsar searches that improves sensitivity by effectively identifying and masking interference in short data segments without prior training.

Contribution

The paper presents IQRM, a novel non-parametric outlier detection method for real-time RFI masking that is adaptable, efficient, and integrated into existing radio transient search pipelines.

Findings

IQRM effectively reduces false positives caused by RFI.

The method is fast enough for real-time streaming applications.

IQRM demonstrates high performance on data from MeerKAT and Lovell telescopes.

Abstract

In a search for short timescale astrophysical transients in time-domain data, radio-frequency interference (RFI) causes both large quantities of false positive candidates and a significant reduction in sensitivity if not correctly mitigated. Here we propose an algorithm that infers a time-variable frequency channel mask directly from short-duration ($\sim$1 s) data blocks: the method consists of computing a spectral statistic that correlates well with the presence of RFI, and then finding high outliers among the resulting values. For the latter task, we propose an outlier detection algorithm called Inter-Quartile Range Mitigation (IQRM), that is both non-parametric and robust to the presence of a trend in sequential data. The method requires no training and can in principle adapt to any telescope and RFI environment; its efficiency is shown on data from both the MeerKAT and Lovell 76-m radio telescopes. IQRM is fast enough to be used in a streaming search and has been integrated into the MeerTRAP real-time transient search pipeline. Open-source Python and C++ implementations are also provided.