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

Abstract

On 2004 December 27, a highly-energetic giant flare was recorded from the magnetar candidate SGR 1806-20. In the months preceding this flare, the persistent X-ray emission from this object began to undergo significant changes. Here, we report on the evolution of key spectral and temporal parameters prior to and following this giant flare. Using the Rossi X-ray Timing Explorer, we track the pulse frequency of SGR 1806-20 and find that the spin-down rate of this SGR varied erratically in the months before and after the flare. Contrary to the giant flare in SGR 1900+14, we find no evidence for a discrete jump in spin frequency at the time of the December 27th flare (|dnu/nu| < 5 X 10^-6). In the months surrounding the flare, we find a strong correlation between pulsed flux and torque consistent with the model for magnetar magnetosphere electrodynamics proposed by Thompson, Lyutikov & Kulkarni (2002). As with the flare in SGR 1900+14, the pulse morphology of SGR 1806-20 changes drastically following the flare. Using the Chandra X-ray Observatory and other publicly available imaging X-ray detector observations, we construct a spectral history of SGR 1806-20 from 1993 to 2005. The usual magnetar persistent emission spectral model of a power-law plus a blackbody provides an excellent fit to the data. We confirm the earlier finding by Mereghetti et al. (2005) of increasing spectral hardness of SGR 1806-20 between 1993 and 2004. Contrary to the direct correlation between torque and spectral hardness proposed by Mereghetti et al., we find evidence for a sudden torque change that triggered a gradual hardening of the energy spectrum on a timescale of years. Interestingly, the spectral hardness, spin-down rate, pulsed, and phase-averaged of SGR 1806-20 all peak months before the flare epoch.

37 pages, 8 figures, 8 tables. Accepted for publication in ApJ. To appear in the Oct 20 2006 edition

Cited by in corpus (42)

• The strongest cosmic magnets: Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars
• X-ray spectra from magnetar candidates. I. Monte Carlo simulations in the non-relativistic regime
• Formation Rates and Evolution Histories of Magnetars
• A Swift gaze into the 2006 March 29th burst forest of SGR 1900+14
• Maximum gravitational-wave energy emissible in magnetar flares
• The Compact X-ray Source 1E 1547.0-5408 and the Radio Shell G327.24-0.13: A New Proposed Association between a Candidate Magnetar and a Candidate Supernova Remnant
• The Ups & Downs of Accreting X-Ray Pulsars: Decade-long observations with the Fermi Gamma-Ray Burst Monitor
• The NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154
• Exciting the Magnetosphere of the Magnetar CXOU J164710.2-455216 in Westerlund 1
• X-ray and Near-IR Variability of the Anomalous X-ray Pulsar 1E 1048.1-5937: From Quiescence Back to Activity
• General relativistic neutron stars with twisted magnetosphere
• Evidence for an abundant old population of Galactic ultra long period magnetars and implications for fast radio bursts
• Topology of magnetars external field. I. Axially symmetric fields
• Electrodynamics of Magnetars III: Pair Creation Processes in an Ultrastrong Magnetic Field and Particle Heating in a Dynamic Magnetosphere
• SGR 1806-20 about two years after the giant flare: Suzaku, XMM-Newton and INTEGRAL observations
• Axion Production in Pulsar Magnetosphere Gaps
• The Sleeping Monster: NuSTAR observations of SGR 1806-20, 11 years after the Giant Flare
• A Search for New Galactic Magnetars in Archival Chandra and XMM-Newton Observations
• NICER Observation of the Temporal and Spectral Evolution of Swift J1818.0-1607: a Missing Link between Magnetars and Rotation Powered Pulsars
• Learning About the Magnetar Swift J1834.9-0846 from its Wind Nebula
• Intermittency and Lifetime of the 625 Hz QPO in the 2004 Hyperflare from the Magnetar SGR 1806-20 as evidence for magnetic coupling between the crust and the core
• XMM-Newton observations of Soft Gamma-ray Repeaters
• On the Origin of Radio Emission from Magnetars
• Current closure through the neutron star crust
• Possible periodic activity in the short bursts of SGR 1806-20: connection to fast radio bursts
• Radiatively driven evaporation from magnetar's surface
• Quasi-periodic oscillations, charge and the gravitomagnetic theory
• X-ray Perspective of the Twisted Magnetospheres of Magnetars
• Broadband Spectral Investigations of Magnetar Bursts
• On the connection between radiative outbursts and timing irregularities in magnetars
• Evidence for a Binary Companion to the Central Compact Object 1E 1207.4-5209
• X-ray Monitoring of the Magnetar CXOU J171405.7-381031 in SNR CTB 37B
• Prospects for gamma-ray emission from magnetar regions in CTAO observations
• Repeating X-ray bursts: Interaction between a neutron star and clumps partially disrupted from a planet
• A Morphological Approach to the Pulsed Emission from Soft Gamma Repeaters
• Magnetar giant flare high-energy emission
• The short bursts in SGR 1806-20, 1E 1048-5937 and SGR 0501+4516
• X-ray emission from magnetic dissipation in the magnetar magnetosphere
• Correlation of Burst Behaviour with Magnetar Age
• A month of monitoring the new magnetar Swift J1555.2-5402 during an X-ray outburst
• The maximum dipole moments of neutron stars implied by the Barrow-Gibbons conjecture
• Searching for small-scale diffuse emission around SGR 1806-20