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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.
Within the magnetar scenario, the twisted magnetosphere model appears very promising in explaining the persistent X-ray emission from the Soft Gamma Repeaters and the Anomalous X-ray Pulsars (SGRs and AXPs). In the first two papers of the series, we
We present results from a coordinated $XMM$-$Newton$+$NuSTAR$ observation of the type 1.8 Seyfert galaxy IRAS 13197-1627. This is a highly complex source, with strong contributions from relativistic reflection from the inner accretion disk, neutral a
We present broadband (3 -- 78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power-law in this energy band, spatially resolved spe
We present an X-ray spectral analysis of the high-mass binary 4U~1700-37 during its hard-soft state evolution. We use the BeppoSAX, Suzaku and RXTE (Rossi X-ray Timing Explorer), Suzaku and BeppoSAX observations for this investigation. We argue that
We report on a new NuSTAR observation and on the ongoing Swift XRT monitoring campaign of the peculiar source 1E 161348-5055, located at the centre of the supernova remnant RCW 103, which is recovering from its last outburst in June 2016. The X-ray s