Journal article
Measuring the Magnetic Dipole Moment and Magnetospheric Fluctuations of SXP 18.3 with a Kalman Filter
Joseph O'Leary, Andrew Melatos, Nicholas J O'Neill, Patrick M Meyers, Dimitris M Christodoulou, Sayantan Bhattacharya, Silas GT Laycock
The Astrophysical Journal (ApJ) | IOP Publishing | Published : 2024
Abstract
The magnetic dipole moment μ of an accretion-powered pulsar in magnetocentrifugal equilibrium cannot be inferred uniquely from time-averaged pulse period and aperiodic X-ray flux data, because the radiative efficiency η 0 of the accretion is unknown, as are the mass, radius, and distance of the star. The degeneracy associated with the radiative efficiency is circumvented if fluctuations of the pulse period and aperiodic X-ray flux are tracked with a Kalman filter, whereupon μ can be measured uniquely up to the uncertainties in the mass, radius, and distance. Here, the Kalman filter analysis is demonstrated successfully in practice for the first time on Rossi X-ray Timing Explorer observation..
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Grants
Awarded by Australian Research Council Centre of Excellence for Gravitational Wave Discovery
Awarded by National Aeronautics and Space Administration Astrophysics Data Analysis Program
Funding Acknowledgements
The authors thank Julian Carlin, Liam Dunn, Tom Kimpson, and Andres Vargas for helpful discussions about X-ray timing data and pulsar astrophysics. We also acknowledge a helpful discussion with Robin Evans regarding Kalman filter accuracy. We thank the anonymous referee for constructive feedback which improved the manuscript. This research was supported by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), grant No. CE170100004. N.J.O'N. is the recipient of a Melbourne Research Scholarship. D.M.C., S.B., and S.T.G.L. acknowledge funding through the National Aeronautics and Space Administration Astrophysics Data Analysis Program grant No. NNX14-AF77G.