We have observed the 3.8 s pulsar CXOU J171405.7 - 381031 with XMM-Newton , and discovered the significant \dot { P } of 6.40 \pm 0.14 \times 10 ^ { -11 } s s ^ { -1 } from this source for the first time , with the aid of archival Chandra data .
The characteristic age ( 950 yr ) , the magnetic field strength ( 5 \times 10 ^ { 14 } G ) , and the spin-down luminosity ( 4.5 \times 10 ^ { 34 } erg s ^ { -1 } ) derived from P and \dot { P } lead us to conclude that CXOU J171405.7 - 381031 should be identified as a new magnetar .
The obtained characteristic age indicates that CXOU J171405.7 - 381031 is youngest among all known anomalous X-ray pulsars , which is consistent with the age estimation from the thermal X-rays of the associated supernova remnant .
The ratio between 2–10 keV luminosity and spin-down luminosity is almost unity , which implies that CXOU J171405.7 - 381031 is the key source to connect magnetars and traditional radio pulsars .