Energy Dependent Intensity Variation of the Persistent X-ray Emission of Magnetars Observed with Suzaku

TL;DR

This study analyzes Suzaku data of 11 magnetars, revealing significant energy-dependent intensity variations in their persistent X-ray emission, supporting a micro-burst emission model and suggesting different emission regions for soft and hard X-ray components.

Contribution

It provides observational evidence for the micro-burst model of magnetar persistent emission and demonstrates energy-dependent intensity variations using Suzaku data.

Findings

Significant excess RMS intensity variations in all magnetars studied.

RMS variations increase with energy in some magnetars.

Different regions likely emit soft and hard X-ray components.

Abstract

Emission mechanism of the magnetars is still controversial while various observational and theoretical studies have been made. In order to investigate mechanisms of both the persistent X-ray emission and the burst emission of the magnetars, we have proposed a model that the persistent X-ray emission consists of numerous micro-bursts of various sizes. If this model is correct, intensity Root Mean Square (RMS) variations of the persistent emission exceed the values expected from the Poisson distribution. Using $Suzaku$ archive data of 11 magnetars (22 observations), the RMS intensity variations were calculated from 0.2 keV to 70 keV. As a result, we found significant excess RMS intensity variations from all the 11 magnetars. We suppose that numerous mircro-bursts constituting the persistent X-ray emission cause the observed variations, suggesting that the persistent X-ray emission and the burst emission have identical emission mechanisms. In addition, we found that the RMS intensity variations clearly increase toward higher energy bands for 4 magnetars (6 observations). The energy dependent RMS intensity variations imply that the soft thermal component and the hard X-ray component are emitted from different regions far apart from each other.