A Study of the 20 Day Superorbital Modulation in the High-Mass X-ray Binary IGR J16493-4348

Abstract

We report on Nuclear Spectroscopic Telescope Array (NuSTAR), Neil Gehrels Swift Observatory (Swift) X-ray Telescope (XRT) and Swift Burst Alert Telescope (BAT) observations of IGR J16493-4348, a wind-fed Supergiant X-ray Binary (SGXB) showing significant superorbital variability. From a discrete Fourier transform of the BAT light curve, we refine its superorbital period to be 20.058 $\pm$ 0.007 days. The BAT dynamic power spectrum and a fractional root mean square analysis both show strong variations in the amplitude of the superorbital modulation, but no observed changes in the period were found. The superorbital modulation is significantly weaker between MJD 55,700 and MJD 56,300. The joint NuSTAR and XRT observations, which were performed near the minimum and maximum of one cycle of the 20 day superorbital modulation, show that the flux increases by more than a factor of two between superorbital minimum and maximum. We find no significant changes in the 3-50 keV pulse profiles between superorbital minimum and maximum, which suggests a similar accretion regime. Modeling the pulse-phase averaged spectra we find a possible Fe K$\alpha$ emission line at 6.4 keV at superorbital maximum. The feature is not significant at superorbital minimum. While we do not observe any significant differences between the pulse-phase averaged spectral continua apart from the overall flux change, we find that the hardness ratio near the broad main peak of the pulse profile increases from superorbital minimum to maximum. This suggests the spectral shape hardens with increasing luminosity. We discuss different mechanisms that might drive the observed superorbital modulation.

arXiv comment17 pages, 14 figures, 3 tables, accepted for publication in The Astrophysical Journal on 2019 May 15

References in corpus (54)

• On the Absorption of X-rays in the Interstellar Medium
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The Swift X-ray Telescope
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• The Burst Alert Telescope (BAT) on the Swift MIDEX Mission
• On characterising the variability properties of X-ray light curves from active galaxies
• An Ultraluminous X-ray Source Powered by An Accreting Neutron Star
• Statistics: Handle with Care, Detecting Multiple Model Components with the Likelihood Ratio Test
• The Swift/BAT Hard X-ray Transient Monitor
• Magnetic Fields of Accreting X-Ray Pulsars with the Rossi X-Ray Timing Explorer
• A millisecond pulsar in a stellar triple system
• Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
• The 22-Month Swift-BAT All-Sky Hard X-ray Survey
• Precessing warped accretion discs in X-ray binaries
• The 35-Day Evolution of the Hercules X-1 Pulse Profile: Evidence For A Resolved Inner Disk Occultation of the Neutron Star
• Binary and Long-Term (Triple?) Modulations of 4U 1820$-$30 in NGC 6624
• The Palermo Swift-BAT Hard X-ray Catalogue. II- Results after 39 months of sky survey
• Long-term Properties of Accretion Disks in X-ray Binaries: I. the variable third period in SMC X-1
• Pulse-amplitude-resolved spectroscopy of bright accreting pulsars: indication of two accretion regimes
• Spectral Changes in the Hyperluminous Pulsar in NGC 5907 as a Function of Super-Orbital Phase
• On the dependence of the X-ray continuum variations with luminosity in accreting X-ray pulsars
• A 78 Day X-ray Period Detected from NGC 5907 ULX1 by Swift
• Superorbital Periodic Modulation in Wind-Accretion High-Mass X-ray Binaries from Swift BAT Observations
• Orbital Decay and Evidence of Disk Formation in the X-ray Binary Pulsar OAO 1657-415
• A tale of two periods: determination of the orbital ephemeris of the super-Eddington pulsar NGC 7793 P13
• Luminosity-dependent changes of the cyclotron line energy and spectral hardness in Cep X-4
• The superorbital variability and triple nature of the X-ray source 4U 1820-303
• Formation of wind-captured discs in Supergiant X-ray binaries : consequences for Vela X-1 and Cygnus X-1
• Variable neutron star free precession in Hercules X-1 from evolution of RXTE X-ray pulse profiles with phase of the 35-day cycle
• Cyclotron resonant scattering feature simulations. II. Description of the CRSF simulation process
• A Detailed Study of 2S 0114+650 with the RXTE
• A ~60-day super-orbital period originating from the ultraluminous X-ray pulsar in M82
• Superorbital Period in the High Mass X-ray Binary 2S 0114+650
• The X-ray binary 2S0114+650=LSI+65 010:A slow pulsar or tidally-induced pulsations?
• Tracking the Orbital and Super-orbital Periods of SMC X-1
• XMM-Newton EPIC observations of Her X-1
• Evolution of Spin, Orbital, and Superorbital Modulations of 4U 0114+650
• A Suzaku X-ray observation of one orbit of the supergiant fast X-ray transient IGR J16479-4514
• Looking at A 0535+26 at low luminosities with NuSTAR
• Suzaku Observations of Four Heavily Absorbed HMXBs
• On the possibility of disk-fed formation in supergiant high-mass X-ray binaries
• Observing the transient pulsations of SMC X-1 with NuSTAR
• Evidence for a resonant cyclotron line in IGR J16493-4348 from the Swift-BAT hard X-ray survey
• Diverse Long-Term Variability of Five Candidate High-Mass X-ray Binaries from Swift Burst Alert Telescope Observations
• Determination of parameters of long-term variability of the X-ray pulsar LMC X-4
• On the super-orbital modulation of supergiant high mass X-ray binaries
• Periodicities in X-ray Binaries from Swift/BAT Observations
• The Goodness of Simultaneous Fits in ISIS
• Unveiling the nature of IGR J16493-4348 with IR spectroscopy
• Probing the nature of IGR J16493-4348: Spectral and temporal analysis of the 1-100 keV emission
• A precessing Be disk as a possible model for occultation events in GX 304-1
• A possible phase dependent absorption feature in the transient X-ray pulsar SAX J2103.5+4545
• The Orbital Parameters of the Eclipsing High-Mass X-ray Binary Pulsar IGR J16493-4348 from Pulsar Timing

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