CHANDRAANDRXTEOBSERVATIONS OF 1E 1547.0–5408: COMPARING THE 2008 AND 2009 OUTBURSTS

Le résumé fourni par la source

We present results from Chandra X-ray Observatory and Rossi X-ray Timing Explorer ( RXTE ) observations of the magnetar 1E 1547.0−5408 (SGR J1550−5418) following the source's outbursts in 2008 October and 2009 January. During the time span of the Chandra observations, which covers days 4 through 23 and days 2 through 16 after the 2008 and 2009 events, respectively, the source spectral shape remained stable in the Chandra band, while the pulsar's spin-down rate in the same span in 2008 increased by a factor of 2.2 as measured by RXTE . This suggests decoupling between the source's spin-down and radiative changes, hence between the spin-down-inferred magnetic field strength and that inferred spectrally. The lack of spectral variation during flux decay is surprising for models of magnetar outbursts. We also found a strong anti-correlation between the phase-averaged flux and the pulsed fraction in the 2008 and 2009 Chandra data, but not in the pre-2008 measurements. We discuss these results in the context of the magnetar model.

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