Two years of INTEGRAL monitoring of the Soft Gamma-Ray Repeater SGR 1806-20: from quiescence to frenzy

Abstract

SGR 1806-20 has been observed for more than 2 years with the INTEGRAL satellite. In this period the source went from a quiescent state into a very active one culminating in a giant flare on December 27 2004. Here we report on the properties of all the short bursts detected with INTEGRAL before the giant flare. We derive their number-intensity distribution and confirm the hardness-intensity correlation for the bursts found by Gotz et al. (2004a). Our sample includes a very bright outburst that occurred on October 5 2004, during which over one hundred bursts were emitted in 10 minutes, involving an energy release of 3 x 1E42 erg. We present a detailed analysis of it and discuss our results in the framework of the magnetar model.

arXiv comment10 pages, 8 figures, to appear in A&A main journal

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• The Prelude to and Aftermath of the Giant Flare of 2004 December 27: Persistent and Pulsed X-ray Properties of SGR 1806-20 from 1993 to 2005
• Strong bursts from the anomalous X-ray pulsar 1E 1547.0-5408 observed with the INTEGRAL/SPI Anti-Coincidence Shield
• The Five Year Fermi/GBM Magnetar Burst Catalog
• Magnetars: a short review and some sparse considerations
• Identification of a Local Sample of Gamma-Ray Bursts Consistent with a Magnetar Giant Flare Origin
• Quasi-Periodic Oscillations in Short Recurring Bursts of the Soft-Gamma Repeater J1550-5418
• Magnetar Outbursts from Avalanches of Hall Waves and Crustal Failures
• SGRs in nearby galaxies: rate, luminosity function and fraction among short GRBs
• Terrestrial Consequences of Spectral and Temporal Variability in Ionizing Photon Events
• A global model of the magnetorotational instability in protoneutron stars
• The 2008 October Swift detection of X-ray bursts/outburst from the transient SGR-like AXP 1E 1547.0-5408
• A Comprehensive Study of Short Bursts from SGR 1806-20 and SGR 1900+14 Detected by HETE-2
• The Giant Flare of December 27, 2004 from SGR 1806-20
• Pulsars and magnetars
• MRI-driven $\alpha -\Omega$ dynamos in protoneutron stars
• Hard X-ray Bursts Detected by the IBIS Telescope Onboard the INTEGRAL Observatory in 2003-2004
• Konus-Wind observations of the new soft gamma-ray repeater SGR 0501+4516
• Dissecting magnetar variability with Bayesian hierarchical models
• Fermi-GBM Observations of the SGR J1935+2154 Burst Forest
• Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates
• Spectral Comparison of Weak Short Bursts to the Persistent X-rays from the Magnetar 1E 1547.0-5408 in its 2009 Outburst
• 15 years of Galactic surveys and hard X-ray Background measurements
• The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars
• Unveiling Soft Gamma-Ray Repeaters with INTEGRAL
• Strongly magnetized pulsars: explosive events and evolution
• The Fermi/LAT sky as seen by INTEGRAL/IBIS
• Long X-ray flares from the central source in RCW 103
• New Gamma-Ray Bursts Found in the Archival Data from the IBIS/ISGRI Telescope of the INTEGRAL Observatory
• The Sources of Apparently Non-Repeating FRB
• When Outliers Are Different
• SGR 1806-20 and the gravitational wave detectors EXPLORER and NAUTILUS
• Search for optical activity of SGR 1806-20
• The short bursts in SGR 1806-20, 1E 1048-5937 and SGR 0501+4516
• INTEGRAL limits on past high-energy activity from FRB 20200120E in M81
• Correlation of Burst Behaviour with Magnetar Age
• From Rare Events to a Population: Discovering Overlooked Extragalactic Magnetar Giant Flare Candidates in Archival Fermi Gamma-ray Burst Monitor Data