Detectability of Magnetar-Induced Vacuum Birefringence with IXPE and eXTP

TL;DR

This paper evaluates the potential of IXPE and eXTP to detect vacuum birefringence caused by magnetars, showing that current instruments can measure this effect, especially from the magnetar 1RXS J170849.0-400910.

Contribution

It provides a realistic magnetic field model and calculates measurable polarization effects, demonstrating the feasibility of detecting vacuum birefringence with upcoming X-ray observatories.

Findings

Time delay could be an order of magnitude larger than previous estimates.

Both IXPE and eXTP can measure birefringence from magnetars.

Magnetar 1RXS J170849.0-400910 is the best candidate for detection.

Abstract

We analyze the prospects of quantitatively detecting vacuum birefringence from magnetars using the IXPE and eXTP experiments. We adopt a realistic profile to model the magnetic field of magnetars, and use it to calculate the time delay and phase difference in the parallel and perpendicular components of polarization eigenmodes using Adler's integral formula. We find that the time delay could be an order of magnitude larger than previous estimates in the literature. We also calculate the Stokes parameters for all known magnetars and show that both IXPE and eXTP are capable of quantitatively measuring birefringence from magnetars, with the magnetar dubbed 1RXS J170849.0-400910 being the best candidate for detection.