The X-ray Properties of the Energetic Pulsar PSR J1838-0655

TL;DR

This paper analyzes X-ray data from multiple observatories to characterize the spectral features and high energy efficiency of the pulsar PSR J1838-0655, revealing a broken power-law spectrum and possible iron emission line.

Contribution

It presents a combined spectral analysis of PSR J1838-0655 using CHANDRA, RXTE, and SUZAKU data, identifying a broken power-law and high X-ray efficiency, and discusses the emission mechanisms involved.

Findings

Broken power-law spectrum with a break at 6.5 keV.

X-ray conversion efficiency of ~0.9%, higher than similar pulsars.

Detection of a 6.65 keV line possibly from ionized iron.

Abstract

We present and interpret several new X-ray features of the X-ray pulsar PSR J1838-0655. The X-ray data are obtained from the archival data of CHANDRA, RXTE}, and SUZAKU. We combine all these X-ray data and fit the spectra with different models. We find that the joint spectra are difficult to fit with a single power law; a broken power-law model with a break at around 6.5 keV can improve the fit significantly. The photon index changes from $\Gamma$ = 1.0 (below 6.5 keV) to $\Gamma$ = 1.5 (above 6.5 keV); this indicates a softer spectral behaviour at hard X-rays. The X-ray flux at 2-20 keV is found to be 1.6x10^{-11} ergs cm^{-2} s^{-1}. The conversion efficiency from the spin-down luminosity is ~ 0.9% at 0.8-10 keV, which is much higher than that (~ 10^{-3}% - 10^{-4}%) of the pulsars that show similar timing properties. We discuss non-thermal radiation mechanisms for the observed high X-ray conversion efficiency and find that emission from the magnetosphere of a greatly inclined rotator is the most favorable interpretation for the conversion rate and the pulse profiles at X-ray bands. A line feature close to 6.65 keV is also detected in the spectra of SUZAKU/XIS; it might be the K$_\alpha$ emission of highly ionised Fe surrounding the pulsar.