A Search for Pulsars in Steep Spectrum Radio Sources

TL;DR

This study conducted a time-domain search for pulsars in 44 steep spectrum radio sources using the Ooty telescope but found no new pulsars, discussing potential reasons and alternative detection methods.

Contribution

First systematic search for pulsars in steep spectrum sources using semi-coherent dedispersion at 327 MHz, exploring reasons for non-detections and proposing new search strategies.

Findings

No new pulsars detected in the sample.

Steep spectrum sources may be pulsars or a new Galactic source class.

Detection challenges include scattering and axis alignment.

Abstract

We report on a time-domain search for pulsars in 44 steep spectrum radio sources originally identified from recent imaging surveys. The time-domain search was conducted at 327 MHz using the Ooty radio telescope, and utilized a semi-coherent dedispersion scheme retaining the sensitivity even for sub-millisecond periods up to reasonably high dispersion measures. No new pulsars were found. We discuss the nature of these steep spectrum sources and argue that majority of the sources in our sample should either be pulsars or a new category of Galactic sources. Several possibilities that could hinder detection of these sources as pulsars, including anomalously high scattering or alignment of the rotation and magnetic axes, are discussed in detail, and we suggest unconventional search methods to further probe these possibilities.