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Origin and energy extent of the pulsed non-thermal X-ray emission

Identify the physical mechanism responsible for the non-thermal pulsed X-ray emission from PSR J0437−4715 and determine the energy range over which this component contributes to the phase-resolved signal, in order to assess its impact within the 0.3–3 keV band used for NICER pulse profile modeling.

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Background

PSR J0437−4715 exhibits a hard X-ray, non-thermal component that is pulsed and dominant above ~3 keV, as shown by NuSTAR. Its contribution below 3 keV could be a few percent, potentially affecting NICER analyses.

The mechanism and energy extent of this non-thermal component have not been firmly identified, so the present paper neglected its possible contribution to phase-resolved modeling.

References

However, since the mechanism responsible for the non-thermal emission remains unknown, it is difficult to assert the energy range where one might expect the pulsed non-thermal emission to be present. In the absence of a firm identification of the origin and energy extent of the pulsed non-thermal emission, we have for now neglected any potential contribution to the phase-resolved signal.

— A NICER View of the Nearest and Brightest Millisecond Pulsar: PSR J0437$\unicode{x2013}$4715 (2407.06789 - Choudhury et al., 9 Jul 2024) in Subsection 'Modeling assumptions', Section 'Discussion'