Deep searches for decameter wavelength pulsed emission from radio-quiet gamma-ray pulsars

TL;DR

This study conducted deep low-frequency radio observations of gamma-ray pulsars, finding no definitive signals but establishing upper flux limits and confirming faint radio emission from one pulsar, advancing understanding of radio-quiet gamma-ray pulsars.

Contribution

It provides the first deep low-frequency search results for multiple radio-quiet gamma-ray pulsars and sets upper limits on their flux densities at decameter wavelengths.

Findings

No periodic signals detected above 8σ threshold.

Confirmed faint radio emission from pulsar J1732-3131.

Established upper limits on flux densities for other pulsars.

Abstract

We report the results of (a) extensive follow-up observations of the gamma-ray pulsar J1732-3131 that has been recently detected at decameter wavelengths, and (b) deep searches for counterparts of 9 other radio-quiet gamma-ray pulsars at 34 MHz, using the Gauribidanur radio telescope. No periodic signal from J1732-3131 could be detected above a detection threshold of $8\sigma$, even with an effective integration time of more than 40 hours. However, the average profile obtained by combining data from several epochs, at a dispersion measure of 15.44 pc/cc, is found to be consistent with that from the earlier detection of this pulsar at a confidence level of 99.2 %. We present this consistency between the two profiles as an evidence that J1732-3131 is a faint radio pulsar with an average flux density of 200--400 mJy at 34 MHz. Detection sensitivity of our deep searches, despite the extremely bright sky background at such low frequencies, is generally comparable to that of higher frequency searches for these pulsars, when scaled using reasonable assumptions about the underlying pulsar spectrum. We provide details of our deep searches, and put stringent upper limits on the decameter wavelength flux densities of several radio-quiet gamma-ray pulsars.