Magnetar Twists: Fermi/Gamma ray Burst Monitor (GBM) detection of SGR J1550-5418

Abstract

SGR J1550-5418 (previously known as AXP 1E 1547.0-5408 or PSR J1550-5418) went into three active bursting episodes in 2008 October and in 2009 January and March, emitting hundreds of typical Soft Gamma Repeater (SGR) bursts in soft gamma-rays. The second episode was especially intense, and our untriggered burst search on Fermi/GBM data (8-1000 keV) revealed ~450 bursts emitted over 24 hours during the peak of this activity. Using the GBM data, we identified a ~150-s-long enhanced persistent emission during 2009 January 22 that exhibited intriguing timing and spectral properties: (i) clear pulsations up to ~110 keV at the spin period of the neutron star (P ~ 2.07 s, the fastest of all magnetars), (ii) an additional (to a power-law) blackbody component required for the enhanced emission spectra with kT ~ 17 keV, (iii) pulsed fraction that is strongly energy dependent and highest in the 50-74 keV energy band. A total isotropic-equivalent energy emitted during this enhanced emission is estimated to be 2.9 x 10^{40} (D/5 kpc)^2 erg. The estimated area of the blackbody emitting region of ~0.046(D/5 kpc)^2 km^2 (roughly a few x 10^{-5} of the neutron star area) is the smallest "hot spot" ever measured for a magnetar and most likely corresponds to the size of magnetically-confined plasma near the neutron star surface.

21 pages, 5 figures, 1 table, resubmitted to ApJ after addressing the referee's comments

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Cited by in corpus (39)

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• Multimessenger astronomy with gravitational waves and high-energy neutrinos
• The Five Year Fermi/GBM Magnetar Burst Catalog
• The 2009 outburst of magnetar 1E 1547-5408: Persistent radiative and burst properties
• Quasi-Periodic Oscillations in Short Recurring Bursts of the Soft-Gamma Repeater J1550-5418
• Magnetar-like X-ray Bursts from a Rotation Powered Pulsar, PSR J1119-6127
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• Fermi/GBM Observations of SGR J0501+4516 Bursts
• Discovery of a new Soft Gamma Repeater, SGR J1833-0832
• RXTE Observations of Anomalous X-ray Pulsar 1E 1547.0-5408 During and After its 2008 and 2009 Outbursts
• Chandra and RXTE Observations of 1E 1547.0-5408: Comparing the 2008 and 2009 Outbursts
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• Chandra Observations of the High-Magnetic-Field Radio Pulsar J1718-3718
• On the trigger mechanisms for SGR giant flares
• Temporal and spectral evolution in X- and gamma-rays of magnetar 1E 1547.0-5408 since its October 2008 outburst: the discovery of a transient hard pulsed component after its January 2009 outburst
• Time resolved spectroscopy of SGR J1550-5418 bursts detected with Fermi/GBM
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• Radiative transfer simulations of magnetar flare beaming
• Dissecting magnetar variability with Bayesian hierarchical models
• Fermi-GBM Observations of the SGR J1935+2154 Burst Forest
• Extended Tails from SGR 1806-20 Bursts
• Simultaneous magnetic polar cap heating during a flaring episode from the magnetar 1RXS J170849.0-400910
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• Hard X-ray/Soft gamma-ray experiments and missions: overview and prospects
• High Frequency Radio Observations of Two Magnetars, PSR J1622$-$4950 and 1E 1547.0$-$5408
• X-ray Perspective of the Twisted Magnetospheres of Magnetars
• Fermi Gamma-ray Space Telescope
• Burst Tails from SGR J1550-5418 Observed with Rossi X-ray Timing Explorer
• Very high frequency gravitational waves from magnetars and gamma-ray burst
• SGR 1806-20 and the gravitational wave detectors EXPLORER and NAUTILUS
• Young neutron stars with soft gamma ray emission and anomalous X-ray pulsar
• Matched-filtering Line Search Methods Applied to Suzaku Data
• Correlation of Burst Behaviour with Magnetar Age
• Investigating the Recursive Short X-ray Burst Behavior of Magnetars Through Crustal Interactions