The Spectrum of the Recycled PSR J0437–4715 and Its White Dwarf Companion

• Published in: The Astrophysical journal 2012-02, Vol.746 (1), p.6-19
• Main Authors: Durant, Martin, Kargaltsev, Oleg, Pavlov, George G, Kowalski, Piotr M, Posselt, Bettina, van Kerkwijk, Marten H, Kaplan, David L
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; GAMMA RADIATION; GAMMA SPECTRA; HYDROGEN; NEUTRON STARS; PULSARS; Recycled; Spectra; Spectral emissivity; STELLAR ATMOSPHERES; TEMPERATURE DISTRIBUTION; Thermal emission; WHITE DWARF STARS; X RADIATION; X-rays
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/746/1/6

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 (T sub(eff) = 3950 + or - 150 K, log g = 6.98 + or - 0.15, R sub(WD) = (1.9 + or - 0.2) x 10 super(9) cm) fits our spectral data remarkably well for the known mass and distance (M = 0.25 + or - 0.02 M sub([middot in circle]), d = 156.3 + or - 1.3 pc), yielding the white dwarf age ([tau] sub(WD) = 6.0 + or - 0.5 Gyr). In the UV, we find a spectral shape consistent with thermal emission from the bulk of the neutron star surface, with surface temperature between 1.25 x 10 super(5) and 3.5 x 10 super(5) K. 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 cutoff power-law component ([Gamma] = 1.56 + or - 0.01, E sub(cut) = 1.1 + or - 0.2 GeV) that is seen in gamma rays and perhaps even extends to the near-UV.