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arXiv · 2401.12373

Multiwavelength pulsations and surface temperature distribution in the middle-aged pulsar B1055-52

Armin Vahdat·Bettina Posselt·George G. Pavlov·Patrick Weltevrede·Andrea Santangelo·Simon Johnston
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Abstract

We present a detailed study of the X-ray emission from PSR B1055-52 using XMM-Newton observations from 2019 and 2000. The phase-integrated X-ray emission from this pulsar is poorly described by existing neutron star atmosphere models. Instead, we confirm that, similar to other middle-aged pulsars, the best-fitting spectral model consists of two blackbody components, with substantially different temperatures and emitting areas, and a nonthermal component characterized by a power law. Our phase-resolved X-ray spectral analysis using this three-component model reveals variations in the thermal emission parameters with the pulsar's rotational phase. These variations suggest a nonuniform temperature distribution across the neutron star's surface, including the cold thermal component and probable hot spot(s). Such a temperature distribution can be caused by external and internal heating processes, likely a combination thereof. We observe very high pulse fractions, 60\%--80\% in the 0.7-1.5, keV range, dominated by the hot blackbody component. This could be related to temperature non-uniformity and potential beaming effects in an atmosphere. We find indication of a second hot spot that appears at lower energies (0.15-0.3, keV) than the first hot spot (0.5-1.5, keV) in the X-ray light curves, and is offset by about half a rotation period. This finding aligns with the nearly orthogonal rotator geometry suggested by radio observations of this interpulse pulsar. If the hot spots are associated with polar caps, a possible explanation for their temperature asymmetry could be an offset magnetic dipole and/or an additional toroidal magnetic field component in the neutron star crust

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Armin Vahdat, Bettina Posselt, George G. Pavlov, Patrick Weltevrede, Andrea Santangelo, Simon Johnston. 2024-01-22. Multiwavelength pulsations and surface temperature distribution in the middle-aged pulsar B1055-52. https://arxiv.org/abs/2401.12373

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