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Understanding the Pulsar Multipolar Field Structure through NICER and Fermi data

Presentation #110.85 in the session “Stellar/Compact (Poster)”.

Published onApr 01, 2022
Understanding the Pulsar Multipolar Field Structure through NICER and Fermi data

Modeling of the NICER X-ray waveform of the pulsar PSR J0030+0451, aimed to constrain the neutron star mass and radius, has inferred surface hot spots (i.e., the magnetic polar caps) that imply significantly non-dipolar magnetic fields. To this end, we investigate magnetic field configurations that comprise offset dipole plus quadrupole components using static vacuum field and force-free global magnetosphere models. We compute geodesics from the observer plane to the polar caps to compute the resulting X-ray light curve and we explore, through Markov chain Monte Carlo techniques, the detailed magnetic field configurations that can reproduce the observed X-ray light curve and have discovered degeneracies. Having obtained the force-free field structures, we then compute the corresponding synchronous gamma-ray light curves and we compare these to those obtained by Fermi-LAT, to provide models consistent with both the X-ray and the gamma-ray data, thereby restricting further the multipole field parameters. An essential aspect of this approach is the proper computation of the relative phase between the synchronous X- and gamma-ray light curves. The next steps and the broader implications of this study will be discussed.

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