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 0.2–3 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 + 0.4 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 pc ≈ 14 − 5 + 7 m and a temperature of T s = 2.9 − 0.4 + 0.6 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 s ≈ 3.9 × 10 14 G . The observations are in good agreement with the predictions of the partially screened gap model, which assumes the existence of small-scale surface magnetic field structures in the polar cap region.