期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 405, 期 3, 页码 1787-1795出版社
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2010.16551.x
关键词
stars: neutron; pulsars: general; X-rays: individual: SGR 0418+5729
资金
- ASI (ASI/INAF) [I/011/07/0, I/010/06/0, I/088/06/0, AAE TH-058]
- CNES
- STFC
- Ramon y Cajal fellowship
- STFC [PP/E001173/1] Funding Source: UKRI
- Science and Technology Facilities Council [PP/E001173/1] Funding Source: researchfish
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 similar to 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 similar to 160 d time-span yielded no evidence for any significant evolution of the spin period, implying a 3 sigma upper limit of 1.1 x 10(-13) s s(-1) on the period derivative and of similar to 3 x 10(13) G 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 i' > 25.1 mag, corresponding to an X-ray-to-optical flux ratio exceeding 10(4), consistent with the characteristics of other magnetars.
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