Multimoment Radio Transient Detection

TL;DR

This paper introduces a multimoment spectral modulation index technique for detecting fast radio transients and effectively removing narrowband RFI, demonstrated through simulations and real data analysis.

Contribution

It presents a novel spectral modulation index method for classifying radio signals and excising narrowband interference in radio transient detection.

Findings

Effective at removing narrowband RFI

Reduces false positives from bright, misdedispersed pulses

Applicable to various signal processing scenarios

Abstract

We present a multimoment technique for signal classification and apply it to the detection of fast radio transients in incoherently dedispersed data. Specifically, we define a spectral modulation index in terms of the fractional variation in intensity across a spectrum. A signal whose intensity is distributed evenly across the entire band has a much lower modulation index than a spectrum with the same intensity localized in a single channel. We are interested in broadband pulses and use the modulation index to excise narrowband radio frequency interference (RFI) by applying a modulation index threshold above which candidate events are removed. The technique is tested both with simulations and using data from sources of known radio pulses (RRAT J1928+15 and giant pulses from the Crab pulsar). We find that our technique is effective at eliminating not only narrowband RFI but also spurious signals from bright, real pulses that are dedispersed at incorrect dispersion measures. The method is generalized to coherent dedispersion, image cubes, and astrophysical narrowband signals that are steady in time. We suggest that the modulation index, along with other statistics using higher-order moments, should be incorporated into signal detection pipelines to characterize and classify signals.