Using Chandra data taken on 2008 June , we detected pulsations at 2.594 39 ( 4 ) s in the soft gamma-ray repeater SGR 1627–41 .
This is the second measurement of the source spin period and allows us to derive for the first time a long-term spin-down rate of ( 1.9 \pm 0.4 ) \times 10 ^ { -11 } s s ^ { -1 } .
From this value we infer for SGR 1627–41 a characteristic age of \sim 2.2 kyr , a spin-down luminosity of \sim 4 \times 10 ^ { 34 } erg s ^ { -1 } ( one of the highest among sources of the same class ) , and a surface dipole magnetic field strength of \sim 2 \times 10 ^ { 14 } G. These properties confirm the magnetar nature of SGR 1627–41 ; however , they should be considered with caution since they were derived on the basis of a period derivative measurement made using two epochs only and magnetar spin-down rates are generally highly variable .
The pulse profile , double-peaked and with a pulsed fraction of ( 13 \pm 2 ) % in the 2–10 keV range , closely resembles that observed by XMM-Newton in 2008 September .
Having for the first time a timing model for this SGR , we also searched for a pulsed signal in archival radio data collected with the Parkes radio telescope nine months after the previous X-ray outburst .
No evidence for radio pulsations was found , down to a luminosity level \sim 10–20 times fainter ( for a 10 % duty cycle and a distance of 11 kpc ) than the peak luminosity shown by the known radio magnetars .