Tracking Hidden Magnetospheric Fluctuations in Accretion-powered Pulsars With a Kalman Filter
Abstract
X-ray flux and pulse period fluctuations in an accretion-powered pulsar convey important information about the disk–magnetosphere interaction. It is shown that simultaneous flux and period measurements can be analysed with a Kalman filter based on the standard magnetocentrifugal accretion torque to generate accurate time-dependent estimates of three hidden state variables, which fluctuate stochastically and cannot be measured directly: the mass accretion rate, the Maxwell stress at the disk–magnetosphere boundary, and the radiative efficiency of accretion onto the stellar surface. The inferred fluctuation statistics carry implications for the physics of hydromagnetic instabilities at the disk–magnetosphere boundary and searches for continuous gravitational radiation from low-mass X-ray binaries.
Additional Information
© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. The authors thank Katie Auchettl for discussions about X-ray observations of accretion-powered pulsars. We are also grateful to the anonymous referee for specific feedback and concrete suggestions about the idealizations in the accretion physics, which clarified several important points and inspired the calculations in Appendices B and C. This research was supported by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), grant number CE170100004. NJO'N is the recipient of a Melbourne Research Scholarship.Attached Files
Published - Melatos_2023_ApJ_944_64.pdf
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Additional details
- Eprint ID
- 119841
- Resolver ID
- CaltechAUTHORS:20230307-205876300.21
- CE170100004
- Australian Research Council
- University of Melbourne
- Created
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2023-05-13Created from EPrint's datestamp field
- Updated
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2023-05-13Created from EPrint's last_modified field
- Caltech groups
- TAPIR