A Deep Pulse Search in Eleven Low Mass X-Ray Binaries

TL;DR

This study conducted a comprehensive search for X-ray pulsations in eleven low mass X-ray binaries using extensive data, but found no evidence of pulsations, setting upper limits and suggesting weak pulsations are rare.

Contribution

It is the first systematic coherent X-ray pulsation search across a diverse set of LMXBs using a semi-coherent method with large datasets.

Findings

No evidence of X-ray pulsations detected in the studied systems.

Upper limits on pulsed amplitudes ranged from 0.14% to 2.9%.

Results imply weak pulsations are likely absent in most non-pulsating LMXBs.

Abstract

We present a systematic coherent X-ray pulsation search in eleven low mass X-ray binaries (LMXBs). We select a relatively broad variety of LMXBs, including persistent and transient sources and spanning orbital periods between 0.3 and 17 hours. We use about 3.6 Ms of data collected by the Rossi X-Ray Timing Explorer (RXTE) and XMM-Newton and apply a semi-coherent search strategy to look for weak and persistent pulses in a wide spin frequency range. We find no evidence for X-ray pulsations in these systems and consequently set upper limits on the pulsed sinusoidal semi-amplitude between 0.14% and 0.78% for ten outbursting/persistent LMXBs and 2.9% for a quiescent system. These results suggest that weak pulsations might not form in (most) non-pulsating LMXBs.