  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.
