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Published December 2016 | Submitted + Published
Journal Article Open

The NuSTAR view of the non-thermal emission from PSR J0437-4715

Abstract

We present a hard X-ray Nuclear Spectroscopic Telescope Array (NuSTAR) observation of PSR J0437−4715, the nearest millisecond pulsar. The known pulsations at the apparent pulse period ∼5.76ms are observed with a significance of 3.7σ, at energies up to 20 keV above which the NuSTAR background dominates. We measure a photon index Γ = 1.50 ± 0.25 (90 per cent confidence) for the power-law fit to the non-thermal emission. It had been shown that spectral models with two or three thermal components fit the XMM–Newton spectrum of PSR J0437−4715, depending on the slope of the power-law component, and the amount of absorption of soft X-rays. The new constraint on the high-energy emission provided by NuSTAR removes ambiguities regarding the thermal components of the emission below 3keV. We performed a simultaneous spectral analysis of the XMM–Newton and NuSTAR data to confirm that three thermal components and a power law are required to fit the 0.3–20 keV emission of PSR J0437−4715. Adding a ROSAT-PSPC spectrum further confirmed this result and allowed us to better constrain the temperatures of the three thermal components. A phase-resolved analysis of the NuSTAR data revealed no significant change in the photon index of the high-energy emission. This NuSTAR observation provides further impetus for future observations with the NICER mission (Neutron Star Interior Composition Explorer) whose sensitivity will provide much stricter constraints on the equation of state of nuclear matter by combining model fits to the pulsar's phase-folded light curve with the pulsar's well-defined mass and distance from radio timing observations.

Additional Information

© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 August 26. Received 2016 August 26; in original form 2015 December 12. The authors thank the referee, Slavko Bogdanov, for very useful suggestions that significantly improved this paper. This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. The data analysis was performed with the NuSTAR Data Analysis Software (nustardas) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). SG is a FONDECYT post-doctoral fellow, funded by grant # 3150428. VMK receives support from an NSERC Discovery Grant and Accelerator Supplement, from the Centre de Recherche en Astrophysique du Québec, an R. Howard Webster Foundation Fellowship from the Canadian Institute for Advanced Study, the Canada Research Chairs Program and the Lorne Trottier Chair in Astrophysics and Cosmology. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020.

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Submitted - 1512.03957v1.pdf

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August 19, 2023
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