The new magnetar SGR J1830-0645 in outburst

Abstract

The magnetar SGR J1830-0645 was discovered in outburst in October 2020. We studied its X-ray properties during the first month of the outburst using XMM-Newton, NuSTAR and Swift observations. The shape and amplitude of the pulse profile varied significantly with energy. The broadband spectrum was well described using two absorbed blackbody components plus a faint power law component at high energies. Phase-resolved spectral analysis of the data suggests that the emission could be attributed to thermal photons from a single heated region with a complex shape on the star surface undergoing resonant Compton scattering on charged particles located in the magnetosphere. Modelling the evolutionary path of the magnetar with our magneto-thermal evolutionary codes indicates that SGR J1830 was born ≈23 kyr ago with a dipolar magnetic field of ∼10¹⁵ G, slightly larger than the current value.