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تسجيل مستخدم جديدMagnetar Broadband X-ray Spectra Correlated with Magnetic Fields: Suzaku Archive of SGRs and AXPs Combined with NuSTAR, Swift, and RXTE
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Studies were made of the 1-70 keV persistent spectra of fifteen magnetars as a complete sample observed with Suzaku from 2006 to 2013. Combined with early NuSTAR observations of four hard X-ray emitters, nine objects showed a hard power-law emission dominating at $gtrsim$10 keV with the 15--60 keV flux of $sim$1-$11times 10^{-11}$ ergs s$^{-1}$ cm$^{-2}$. The hard X-ray luminosity $L_{rm h}$, relative to that of a soft-thermal surface radiation $L_{rm s}$, tends to become higher toward younger and strongly magnetized objects. Updated from the previous study, their hardness ratio, defined as $xi=L_{rm h}/L_{rm s}$, is correlated with the measured spin-down rate $dot{P}$ as $xi=0.62 times (dot{P}/10^{-11},{rm s},{rm s}^{-1})^{0.72}$, corresponding with positive and negative correlations of the dipole field strength $B_{rm d}$ ($xi propto B_{rm d}^{1.41}$) and the characteristic age $tau_{rm c}$ ($xi propto tau_{rm c}^{-0.68}$), respectively. Among our sample, five transients were observed during X-ray outbursts, and the results are compared with their long-term 1-10 keV flux decays monitored with Swift/XRT and RXTE/PCA. Fading curves of three bright outbursts are approximated by an empirical formula used in the seismology, showing a $sim$10-40 d plateau phase. Transients show the maximum luminosities of $L_{rm s}$$sim$$10^{35}$ erg s$^{-1}$, which is comparable to those of the persistently bright ones, and fade back to $lesssim$$10^{32}$ erg s$^{-1}$. Spectral properties are discussed in a framework of the magnetar hypothesis.
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