The spectrum of the recycled PSR J0437-4715 and its white dwarf companion

TL;DR

This study provides a comprehensive multi-wavelength analysis of the PSR J0437-4715 binary system, revealing detailed properties of the white dwarf companion and neutron star, including temperature, atmosphere, and emission mechanisms.

Contribution

It offers the first complete spectral modeling from mid-infrared to gamma-ray for this binary, combining new observations with archival data to characterize both components.

Findings

White dwarf atmosphere fits well with Teff=3950K and radius ~1.9e9 cm.

Neutron star surface temperature estimated between 125,000K and 350,000K.

High-energy tail in X-ray consistent with gamma-ray emission extension.

Abstract

We present extensive spectral and photometric observations of the recycled pulsar/white-dwarf binary containing PSR J0437-4715, which we analyzed together with archival X-ray and gamma-ray data, to obtain the complete mid-infrared to gamma-ray spectrum. We first fit each part of the spectrum separately, and then the whole multi-wavelength spectrum. We find that the optical-infrared part of the spectrum is well fit by a cool white dwarf atmosphere model with pure hydrogen composition. The model atmosphere (Teff = 3950pm150K, log g=6.98pm0.15, R_WD=(1.9pm0.2)e9 cm) fits our spectral data remarkably well for the known mass and distance (M=0.25pm0.02Msun, d=156.3pm1.3pc), yielding the white dwarf age (tau=6.0pm0.5Gyr). In the UV, we find a spectral shape consistent with thermal emission from the bulk of the neutron star surface, with surface temperature between 1.25e5 and 3.5e5K. The temperature of the thermal spectrum suggests that some heating mechanism operates throughout the life of the neutron star. The temperature distribution on the neutron star surface is non-uniform. In the X-rays, we confirm the presence of a high-energy tail which is consistent with a continuation of the cut-off power-law component (Gamma=1.56pm0.01, Ecut=1.1pm0.2GeV) that is seen in gamma-rays and perhaps even extends to the near-UV.