Modeling the precession of the warped inner accretion disk in the pulsars LMC X-4 and SMC X-1 with NuSTAR and XMM-Newton

Abstract

We present a broad-band X-ray study of the effect of superorbital periods on X-ray spectra and pulse profiles in the neutron star X-ray binaries LMC X-4 and SMC X-1. These two sources display periodic or quasi-periodic variations in luminosity on the order of tens of days which are known to be superorbital, and are attributed to warped, precessing accretion disks. Using joint NuSTAR and XMM-Newton observations that span a complete superorbital cycle, we examine the broad-band spectra of these sources and find the shape to be well described by an absorbed power law with a soft blackbody component. Changes in spectral shape and pulse profile shape are periodic with superorbital period, as expected from a precessing disk. We perform X-ray tomography using the changes in pulse profiles to model the geometry and kinematics of the inner accretion disk. Our simple beam and inner disk geometric model indicates that the long term changes in soft pulse shape and phase are consistent with reprocessed emission from a precessing inner disk.

arXiv commentUpdated with version accepted to ApJ. 16 pages, 13 figures

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Cited by in corpus (12)

• On the equations of warped disc dynamics
• Is superorbital modulation in SMC X-1 caused by absorption in warped precessing accretion disc?
• Broadband mHz QPOs and spectral study of LMC X$-$4 with AstroSat
• A broad-band X-ray view of the precessing accretion disk and pre-eclipse dip in the pulsar Her X-1 with NuSTAR and XMM-Newton
• Evolution of the spin, spectrum and super-orbital period of the ultraluminous X-ray pulsar M51 ULX7
• Common patterns in pulse profiles of High Mass X-ray Binaries
• Extending the baseline for SMC X-1's spin and orbital behavior with NuSTAR stray light
• Investigating the superorbital modulations in 4U 1909+07, IGR J16418-4532 and IGR J16479-4514 with Swift XRT, BAT and NuSTAR observations
• Discovery of Quasi Periodic Oscillations in the persistent X-ray emission of Accreting Binary X-ray Pulsar LMC X-4
• Monitoring Observations of SMC X-1's Excursions (MOOSE) I: Program Description and Initial High-State Spectral Results
• Disk precession to explain the super-orbital modulation of LMC X-4: results from the Swift monitoring campaign
• Constraining the evolution of the unstable accretion disk in SMC X-1 with NICER