Pulsed, Polarized X-ray Emission from Neutron Star Surfaces: the Effects of Vacuum Birefringence in the Magnetosphere
arXiv:2512.22978 · doi:10.3847/1538-4357/ae313c
Abstract
Intense magnetic fields in the atmospheres of neutron stars render non-trivial angular dependence of intensity and polarization of soft X-ray emission originating from their surfaces. By tracking the complex electric field vector for each photon during its atmospheric transport and propagation in general relativistic and birefringent magnetospheres, our Monte Carlo simulation, named MAGTHOMSCATT, allows for capturing the complete polarization properties, including the intricate interplay between linearity and circularity. The new inclusion in MAGTHOMSCATT of quantum electrodynamical influences on polarization in the magnetosphere is presented. We simulate the pulsed and polarized X-ray emission from the outer layers of optically thick, fully ionized atmospheres of neutron stars, with a focus on the radiation emitted from extended polar caps of magnetars, which are the most highly magnetized neutron stars. Using the recent intensity pulse profile data for the magnetar 1RXS J11708-4009, we constrain the geometric parameters, namely the angles between the magnetic axis and the observer's viewing direction relative to the spin axis, as well as the sizes of emission regions. The distributions of these parameters and the best-fit configuration are provided. In addition, we discuss the important impacts of vacuum birefringence in the magnetosphere on increasing the linear polarization degree. A comparison with the case of a weakly magnetized neutron star, RX J0822.0-4300, is also discussed. Our simulation still needs further development, particularly to incorporate the vacuum resonance effect. Nevertheless, the formalism presented here can be employed to constrain geometric parameters for various types of neutron stars.
27 pages, 10 figures, accepted for publication in The Astrophysical Journal
References in corpus (22)
- Atmosphere Models of Magnetized Neutron Stars: QED Effects, Radiation Spectra, and Polarization Signals
- Distances to Anomalous X-ray Pulsars using Red Clump Stars
- Detailed high-energy characteristics of AXP 1RXS J170849-400910 - Probing the magnetosphere using INTEGRAL, RXTE and XMM-Newton
- Polarized x-rays from a magnetar
- Very deep X-ray observations of the Anomalous X-ray Pulsar 4U 0142+614
- XMM-Newton observations of CXOU J010043.1-721134: the first deep look at the soft X-ray emission of a magnetar
- A strong X-ray polarization signal from the magnetar 1RXS J170849.0-400910
- IXPE Detection of Polarized X-rays from Magnetars and Photon Mode Conversion at QED Vacuum Resonance
- Spectral features in isolated neutron stars induced by inhomogeneous surface temperatures
- Pulse Peak Migration during the Outburst Decay of the Magnetar SGR 1830-0645: Crustal Motion and Magnetospheric Untwisting
- Rotating vector model for magnetars
- Magnetic Pair Creation Transparency in Gamma-Ray Pulsars
- Simultaneous magnetic polar cap heating during a flaring episode from the magnetar 1RXS J170849.0-400910
- Polarized Radiation Transfer in Neutron Star Surface Layers
- Intensity and Polarization Characteristics of Extended Neutron Star Surface Regions
- X-ray Polarisation in Magnetar Atmospheres -- Effects of Mode Conversion
- Polarimetry for measuring the vacuum magnetic birefringence with quasi-static fields: a systematics study for the VMB@CERN experiment
- Measuring the Non-Axially-Symmetric Surface Temperature Distribution of the Central Compact Object in Puppis A
- X-ray polarisation signatures in bombarded magnetar atmospheres
- Monte Carlo Simulations of Polarized Radiative Transfer in Neutron Star Atmospheres
- Polarized Radiation Signals from Highly Magnetized Neutron Star Surfaces
- Pulsed and Polarized X-ray Emission from Neutron Star Surfaces