Disk precession to explain the super-orbital modulation of LMC X-4: results from the Swift monitoring campaign
arXiv:2202.07703 · doi:10.1093/mnras/stac450
Abstract
We studied the spectral changes of the high-mass X-ray binary system LMC X-4 to understand the origin and mechanisms beyond its super-orbital modulation (30.4 days). To this aim, we obtained a monitoring campaign with Swift/XRT (0.3-10 keV) and complemented these data with the years-long Swift/BAT survey data (15-60 keV). We found a self-consistent, physically motivated, description of the broadband X-ray spectrum using a Swift/XRT and a NuSTAR observation at the epoch of maximum flux. We decomposed the spectrum into the sum of a bulk+thermal Comptonization, a disk-reflection component and a soft contribution from a standard Shakura-Sunyaev accretion disk. We applied this model to 20 phase-selected Swift spectra along the super-orbital period. We found a phase-dependent flux ratio of the different components, whereas the absorption column does not significantly vary. The disk emission is decoupled with respect to the hard flux. We interpret this as a geometrical effect in which the inner parts of the disk are tilted with respect to the obscuring outer regions.
arXiv comment14 pages, 15 figures, Accepted for publication in MNRAS
References in corpus (34)
- The Swift/BAT Hard X-ray Transient Monitor
- Optimal binning of X-ray spectra and response matrix design
- Thermal and Bulk Comptonization in Accretion-Powered X-Ray Pulsars
- Precessing warped accretion discs in X-ray binaries
- Cyclotron lines in highly magnetized neutron stars
- Magnetic Screening in Accreting Neutron Stars
- Origin of the Soft Excess in X-ray Pulsars
- The ephemeris, orbital decay, and masses of 10 eclipsing HMXBs
- A Systematic Search for Periodicities in RXTE/ASM Data
- Study of the accreting pulsar 4U 0115+634 with a bulk and thermal Comptonization model
- Characterizing X-ray binary long-term variability
- Cyclotron Line Variability
- Nature of the Soft Spectral Component in the X-ray Pulsars SMC X-1 and LMC X-4
- The 0.1-100 keV Spectrum of LMC X-4 in the High State: Evidence for a High Energy Cyclotron Absorption Line
- Numerical solution of the radiative transfer equation: X-ray spectral formation from cylindrical accretion onto a magnetized neutron star
- The NuSTAR X-ray Spectrum of Hercules X-1: A Radiation-Dominated Radiative Shock
- Timing and spectral studies of LMC X-4 in high and low states with Beppo-SAX: Detection of pulsations in the soft spectral component
- Warping and Precession of Accretion Disks Around Magnetic Stars: Nonlinear Evolution
- Spectral variations of the X-ray binary pulsar LMC X-4 during its long period intensity variation and a comparison with Her X-1
- Pulse-phase spectroscopy of SMC X-1 with Chandra and XMM-Newton: reprocessing by a precessing disk?
- Dependence of the orbital modulation of X-rays from 4U 1820-303 on the accretion rate
- X-ray reprocessing: Through the eclipse spectra of high mass X-ray binaries with XMM-Newton
- Suzaku X-ray Spectra and Pulse Profile Variations during the Superorbital Cycle of LMC X-4
- Long term flux variations in Cen X-3: clues from flux dependent orbital modulation and pulsed fraction
- Modeling the precession of the warped inner accretion disk in the pulsars LMC X-4 and SMC X-1 with NuSTAR and XMM-Newton
- Spectroscopic Signatures of the Superorbital Period in the Neutron Star Binary LMC X-4
- Observations of the X-ray pulsar LMC X-4 with NuSTAR: limit on the magnetic field and tomography of the system in the fluorescent iron line
- Reproductions of super-orbital X-ray light-curves with the precessing accretion ring model and implications on accretion flows through accretion rings
- Long-Term INTEGRAL and RXTE Observations of the X-Ray Pulsar LMC X-4
- Determination of parameters of long-term variability of the X-ray pulsar LMC X-4
- Ionized Reflection Spectra from Accretion Disks Illuminated by X-ray Pulsars
- Discovery of pulsation dropout and turn-on during the high state of the accreting X-ray pulsar LMC X-4
- Peculiarities of super-Eddington flares from the X-ray pulsar LMC X-4 with NuSTAR
- Comprehensive broadband study of accreting neutron stars with Suzaku: Is there a bi-modality in the X-ray spectrum?