Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates

TL;DR

This study analyzes the spectra of magnetar candidates' quiescent emission and bursts, revealing a common two-blackbody model and correlations suggesting a shared emission mechanism, with some sources showing additional non-thermal components.

Contribution

It demonstrates that both quiescent and burst spectra of magnetar candidates can be modeled by a two-blackbody function, indicating a unified emission process.

Findings

Spectra are well fitted by a two-blackbody model.

A consistent temperature ratio (~0.4) between two blackbodies.

Some AXPs exhibit excess emission above 7 keV, indicating a non-thermal component.

Abstract

Spectral studies of quiescent emission and bursts of magnetar candidates using XMM-Newton, Chandra and Swift data are presented. Spectra of both the quiescent emission and the bursts for most magnetar candidates are reproduced by a photoelectrically absorbed two blackbody function (2BB). There is a strong correlation between lower and higher temperatures of 2BB (kT_LT and kT_HT) for the magnetar candidates of which the spectra are well reproduced by 2BB. In addition, a square of radius for kT_T (R_LT^2) is well correlated with a square of radius for kT_HT (R_HT^2). A ratio kT_LT/kT_HT ~ 0.4 is nearly constant irrespective of objects and/or emission types (i.e., the quiescent emission and the bursts). This would imply a common emission mechanism among the magnetar candidates. The relation between the quiescent emission and the bursts might be analogous to a relation between microflares and solar flares of the sun. Three AXPs (4U 0142+614, 1RXS J170849.0-400910 and 1E 2259+586) seem to have an excess above ~7 keV which well agrees with a non-thermal hard component discovered by INTEGRAL.