XMM-Newton Observation of the Nearby Pulsar B1133+16

Abstract

We constrain the X-ray properties of the nearby (360 pc), old (5 Myr) pulsar B1133+16 with ∼100 ks effective exposure time by XMM-Newton. The observed pulsar flux in the 0.23 keV energy range is ∼10^-14 erg cm^-2 ^s-1, which results in the recording of ∼ 600 source counts with the EPIC pn and MOS detectors. The X-ray radiation is dominated by nonthermal radiation and is well described by both a single power-law model (PL) and a sum of blackbody and power-law emission (BB+PL). The BB+PL model results in a spectral photon index γ = 2.4^+0.3 <inf>0.4</inf> and a nonthermal flux in the 0.2-3 keV energy range of (7 ± 2) × 10^-15 erg cm^-2 ^s-1. The thermal emission is consistent with the blackbody emission from a small hot spot with a radius of R<inf>pc</inf> ≈ 14^{+ 7} <inf>-5</inf> m and a temperature of = T<inf>s</inf> 2.9^{+ 0.6} <inf>0.4</inf> MK. Assuming that the hot spot corresponds to the polar cap of the pulsar, we can use the magnetic flux conservation law to estimate the magnetic field at the surface B<inf>s</inf> ≈ 3.9 × 10¹⁴ G . The observations are in good agreement with the predictions of the partially screened gap model, which assumes the existence of smallscale surface magnetic field structures in the polar cap region.