The calm after the storm: XMM-Newton observation of SGR 1806-20 two months after the Giant Flare of 2004 December 27

Abstract

XMM-Newton observed the soft gamma repeater SGR 1806-20 about two months after its 2004 December 27 giant flare. A comparison with the previous observations taken with the same instrument in 2003-2004 shows that the pulsed fraction and the spin-down rate have significantly decreased and that the spectrum slightly softened. These changes may indicate a global reconfiguration of the neutron star magnetosphere. The spectral analysis confirms that the presence of a blackbody component in addition to the power-law is required. Since this additional component is consistent with being constant with respect to the earlier observations, we explore the possibility of describing the long-term spectral evolution as only due to the power-law variations. In this case, the slope of the power-law does not significantly change and the spectral softening following the giant flare is caused by the increase of the relative contribution of the blackbody over the power-law component.

arXiv comment5 pages, 2 figures, accepted for publication in A&A Letters

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• SGRs and AXPs as rotation powered massive white dwarfs
• The first XMM-Newton observations of the Soft Gamma-ray Repeater SGR 1900+14
• Two years of INTEGRAL monitoring of the Soft Gamma-Ray Repeater SGR 1806-20: from quiescence to frenzy
• The Giant Flare of December 27, 2004 from SGR 1806-20
• Magnetar oscillations pose challenges for strange stars
• SGR 1806-20 about two years after the giant flare: Suzaku, XMM-Newton and INTEGRAL observations
• The Sleeping Monster: NuSTAR observations of SGR 1806-20, 11 years after the Giant Flare
• XMM-Newton observations of SGR 1806-20 over seven years following the 2004 Giant Flare
• X-ray emission from isolated neutron stars
• Five years of SGR 1900+14 observations with BeppoSAX
• XMM-Newton observations of Soft Gamma-ray Repeaters
• Pulse Frequency Fluctuations of Magnetars
• Long term spectral variability in the Soft Gamma-ray Repeater SGR 1900+14
• Long term spectral variability in the soft gamma ray repeater SGR 1900+14
• Magnetars' Giant Flares: the case of SGR 1806-20
• Searching for small-scale diffuse emission around SGR 1806-20