Polarization study of gamma-ray binary

Abstract

The polarization of X-ray emission is a unique tool used to investigate the magnetic field structure around astrophysical objects. In this paper, we study the linear polarization of X-ray emissions from gamma-ray binary systems based on pulsar scenarios. We discuss synchrotron emissions from pulsar wind particles accelerated by a standing shock. We explore three kinds of axisymmetric magnetic field structures: (i) toroidal magnetic fields, (ii) poloidal magnetic fields, and (iii) tangled magnetic fields. Because of the axisymmetric structure, the polarization angle of integrated emission is oriented along or perpendicular to the shock-cone axis projected on the sky and swings by 360? in one orbit. For the toroidal case, the polarization angle is always directed along the shock cone axis and smoothly changes along the orbital phase. For the poloidal/tangled magnetic field, the direction of the polarization angle depends on the system parameters and orbital phase. In one orbit, the polarization degree for the toroidal case can reach the maximum value of the synchrotron radiation (? 70%), while the maximum polarization degree for poloidal/tangled field cases is several 10%. We apply our model to bright gamma-ray binary LS 5039 and make predictions for future observations. With the expected sensitivity of the Imaging X-ray Polarimetry Explorer, linear polarization can be detected by an observation of several days if the magnetic field is dominated by the toroidal magnetic field. If the magnetic field is dominated by the poloidal/tangled field, significant detection is expected with an observation longer than 10 days.

17 pages, 13 figures

References in corpus (22)

• TeV lightcurve of PSR B1259-63/SS2883
• HESS J0632+057 : A new gamma-ray binary?
• Multiwavelength monitoring and X-ray brightening of Be X-ray binary PSR J2032+4127/MT91 213 on its approach to periastron
• A Luminous Gamma-ray Binary in the Large Magellanic Cloud
• The changing milliarcsecond radio morphology of the gamma-ray binary LS 5039
• Sign of hard X-ray pulsation from the gamma-ray binary system LS 5039
• High-Energy emissions from the Pulsar/Be binary system PSR J2032+4127/MT91 213
• Pulsar model of the high energy phenomenology of LS 5039
• NuSTAR observation of LS 5039
• Relativistic fluid modelling of gamma-ray binaries. I. The model
• High-energy emissions from the gamma-ray binary LS 5039
• Modelling the interaction between relativistic and non-relativistic winds in binary pulsar systems: strong magnetization of the pulsar wind
• GeV detection of HESS J0632+057
• Global Simulations of the Interaction of Microquasar Jets with a Stellar Wind in High-Mass X-ray Binaries
• Relativistic fluid modelling of gamma-ray binaries. II. Application to LS 5039
• A dynamical and radiation semi-analytical model of pulsar-star colliding winds along the orbit: Application to LS 5039
• Investigation of the energy dependence of the orbital light curve in LS 5039
• Radio QPO in the $\gamma$-ray-loud X-ray binary LS I +61${}^{\circ }$303
• Properties of a hypothetical cold pulsar wind in LS~5039
• A Precessing Jet Scenario for the Multi-Wavelength Long-Term Modulation of LS I +61${}^{\circ }$303
• GeV emission of gamma-ray binary with pulsar scenario
• Multi-wavelength observations of the BL Lac object Fermi J1544-0649: one year after its awakening