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Emission of two short hard X-ray bursts on 2009 June 5 disclosed the existence of a new soft gamma-ray repeater, now catalogued as SGR 0418+5729. After a few days, X-ray pulsations at a period of 9.1 s were discovered in its persistent emission. SGR 0418+5729 was monitored almost since its discovery with the Rossi X-ray Timing Explorer (2–10 keV energy range) and observed many times with Swift (0.2–10 keV). The source persistent X-ray emission faded by a factor of ∼10 in about 160 d, with a steepening in the decay about 19 d after the activation. The X-ray spectrum is well described by a simple absorbed blackbody, with a temperature decreasing in time. A phase-coherent timing solution over the ∼160 d time-span yielded no evidence for any significant evolution of the spin period, implying a 3σ upper limit of on the period derivative and of on the surface dipole magnetic field. Phase-resolved spectroscopy provided evidence for a significant variation of the spectrum as a function of the stellar rotation, pointing to the presence of two emitting caps, one of which became hotter during the outburst. Finally, a deep observation of the field of SGR 0418+5729 with the new Gran Telescopio Canarias 10.4-m telescope allowed us to set an upper limit on the source optical flux of , corresponding to an X-ray-to-optical flux ratio exceeding , consistent with the characteristics of other magnetars. [ABSTRACT FROM AUTHOR]

Using Chandra data taken in 2008 June, we detected pulsations at 2.594 39(4) s in the soft gamma-ray repeater SGR 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 . From this value, we infer for SGR 41 a characteristic age of ∼2.2 kyr, a spin-down luminosity of (one of the highest among sources of the same class), and a surface dipole magnetic field strength of G. These properties confirm the magnetar nature of SGR 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 per cent 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 soft gamma-ray repeater (SGR), we also searched for a pulsed signal in archival radio data collected with the Parkes radio telescope 9 months after the previous X-ray outburst. No evidence for radio pulsations was found, down to a luminosity level ∼10–20 times fainter (for a 10 per cent duty cycle and a distance of 11 kpc) than the peak luminosity shown by the known radio magnetars. [ABSTRACT FROM AUTHOR]