X-ray Halo of the Pulsar 4U 1538–52 from SRG Data

Abstract

We present the first results of the SRG observation of the pulsar 4U 1538–52 based on ARC-XC and eROSITA data. An extended emission in the form of a halo is detected around the source in the 0.5–8 keV energy band. Our simulation has shown that its surface brightness distribution can be described by a two-component model composed of a flat disk \({\sim}250^{\prime\prime}\) in radius and a \(\beta\)-model with a characteristic size \({\sim}480^{\prime\prime}\). We have constructed a broadband spectrum of 4U 1538–52 in the energy range 0.5–30 keV, which can be fitted by a weakly absorbed (\(N_{\textrm{H}}\simeq 0.7\times 10^{22}\) cm\({}^{-2}\)) power law with a high-energy cutoff. In addition, iron emission lines are detected in the pulsar spectrum at 6–7 keV. We show that the observed halo spectrum is considerably softer (a power-law index \({\simeq}2.8\)) than the pulsar spectrum (a power-law index \({\simeq}0.9\)), consistent with the predictions of theoretical models for the X-ray scattering by dust.