Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates

Spectral studies of quiescent emission and bursts of magnetar candidates based on XMM-Newton, Chandra, and Swift data are presented. Spectra of both the quiescent emission and the burst for most magnetar candidates are reproduced by a photoelectrically absorbed two-blackbody function (2BB). There is a strong correlation between the lower and higher temperatures of 2BB ( $kT_{\mathrm{LT}}$ and $kT_{\mathrm{HT}}$ ) for the magnetar candidates of which the spectra are well reproduced by 2BB. In addition, a square of radius for $kT_{\mathrm{LT}}$ ( $R_{\mathrm{LT}}^2$ ) is well correlated with a square of radius for $kT_{\mathrm{HT}}$ ( $R_{\mathrm{HT}}^2$ ). The ratio $kT_{\mathrm LT}/kT_{\mathrm HT}$ $\approx$ 0.4 is nearly constant irrespective of the objects and/or emission types (i.e., the quiescent emission and the burst). This would imply that an emission mechanism is common among the magnetar candidates. The relation between the quiescent emission and the burst might be analogous to a relation between the solar microflare and the solar flare. Three anomalous X-ray pulsars (AXPs) (4U0142 $+$ 614, 1RXSJ170849.0 $-$ 400910, and 1E 2259 $+$ 586) seem to have an excess above $\sim$ 7 keV, which well agrees with a nonthermal hard component discovered by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL).