We present the results of our 8 year X-ray monitoring campaign on CXOU J171405.7 - 381031 , the magnetar associated with the faint supernova remnant ( SNR ) CTB 37B .
It is among the youngest by inferred spin-down age , and most energetic in spin-down power of magnetars , and may contribute , at least partially , to the GeV and TeV emission coincident with the SNR .
We use a series of Chandra , XMM-Newton , and NuSTAR observations to characterize the timing and spectral properties of the magnetar .
The spin-down rate of the pulsar almost doubled in < 1 year and then decreased slowly to a more stable value .
Its X-ray flux varied by \approx 50 \% , possibly correlated with the spin-down rate .
The 1 - 79 keV spectrum is well-characterized by an absorbed blackbody plus power-law model with an average temperature of kT = 0.62 \pm 0.04 keV and photon index \Gamma = 0.92 \pm 0.16 , or by a Comptonized blackbody with kT = 0.55 \pm 0.04 keV and an additional hard power law with \Gamma = 0.70 \pm 0.20 , In contrast with most magnetars , the pulsed signal is found to decrease with energy up to 6 keV , which is apparently caused by mixing with the hard spectral component that is pulse-phase shifted by \approx 0.43 cycles from the soft X-rays .
We also analyze the spectrum of the nearby , diffuse nonthermal source XMMU J171410.8 - 381442 , whose relation to the SNR is uncertain .