Bright X-ray binaries are thought to be promising candidates for detecting continuous gravitational waves, because it is possible that the spin-up torques provided by accretion are offset by gravitational wave emission to maintain their equilibrium spin periods. A long-standing project led by Monash PhD student Shanika Galaudage has sought to use the most sensitive X-ray data available for the two best candidates, Sco X-1 and Cyg X-2, to make a deep search for pulsations that would measure the spin of the compact object in these systems. The analysis was extremely challenging, particularly for Sco X-1; that source is so bright that highly unusual data modes need to be selected for observations with the RXTE/PCA, which complicates the data reduction. Unfortunately we found no strong evidence of pulsations, but we did derive the deepest limits on pulse amplitudes ever. The paper describing our results has now been accepted by MNRAS.

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Labels: 2021, gravitational waves