A deep search for radio emission from three X-ray pulsars : are radio emission and X-ray pulsations anticorrelated ?

TL;DR

This study conducted a deep radio search for three X-ray pulsars, finding no radio emission and suggesting a strong anti-correlation between radio emission and X-ray pulsations in such systems.

Contribution

It provides the first stringent upper limits on radio emission from these X-ray pulsars and statistically demonstrates an anti-correlation with X-ray pulsations.

Findings

No radio emission detected at optical positions

Radio luminosity limits are significantly below those of radio-bright X-ray binaries

X-ray pulsations and radio emission are strongly anti-correlated

Abstract

We present results from a deep search for radio emission from the X-ray pulsar systems GX 1+4, GS 0834-430 and 4U 0115+63 which have variously been suggested to possess radio jets and to be good candidates for propellor ejection mechanisms. None of these sources is detected at their optical positions, to 3 sigma limits of a few hundred micro-Jy. This places upper limits on their radio luminosities and thus on the internal energy and numbers of any relativistic electrons which are three to four orders of magnitude below those of radio-bright X-ray binaries such as SS 433 and Cyg X-3. Spectral and structural information on the proposed `radio lobes' of GX 1+4 make their association with the source unlikely. The lack of detected radio emission from any X-ray pulsar system is discussed statistically, and it is found that X-ray pulsations and radio emission from X-ray binaries are strongly anti-correlated.