SWIFT HIGHLIGHTS AND FLARES (BACK TO THE DRAWING BOARD?)

Swift opened up a new era in the study of gamma-ray burst sources (GRB). Among a variety of discoveries made possible by Swift, here we focus on GRB 090423, the event at z = 8.2 which currently holds the record of the most distant celestial object ever caught by human instrumentation. This GRB allowed us to have a direct look at the early Universe. The central engine activity giving origin to the GRB emission is also discussed starting from the observational findings of an updated GRB X-ray flares catalog.

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Evidence of X-Ray Plateaus Driven by the Magnetar Spindown Winds in Gamma-Ray Burst Afterglows

The Astrophysical Journal ◽

10.3847/1538-4357/ac2c74 ◽

2021 ◽

Vol 922 (2) ◽

pp. 102

Author(s):

Shu-Jin Hou ◽

Shuang Du ◽

Tong Liu ◽

Hui-Jun Mu ◽

Ren-Xin Xu

Keyword(s):

Gamma Ray ◽

Normal Component ◽

Gamma Ray Bursts ◽

Cutting Edge ◽

Decay Phase ◽

Gamma Ray Burst ◽

X Ray ◽

Central Engine

Abstract The central engine of gamma-ray bursts (GRBs) remains an open and cutting-edge topic in the era of multimessenger astrophysics. X-ray plateaus appear in some GRB afterglows, which are widely considered to originate from the spindown of magnetars. According to the stable magnetar scenario of GRBs, an X-ray plateau and a decay phase ∼t −2 should appear in X-ray afterglows. Meanwhile, the “normal” X-ray afterglow is produced by the external shock from a GRB fireball. We analyze the Neil Gehrels Swift GRB data, then find three gold samples that have an X-ray plateau and a decay phase ∼t −2 superimposed on the jet-driven normal component. Based on these features of the lightcurves, we argue that the magnetars should be the central engines of these three GRBs. Future joint multimessenger observations might further test this possibility, which can then be beneficial to constrain GRB physics.

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Gamma-Ray Burst Observations with BATSE

Symposium - International Astronomical Union ◽

10.1017/s0074180900114664 ◽

1998 ◽

Vol 188 ◽

pp. 159-162

Author(s):

Gerald J. Fishman

Keyword(s):

Gamma Rays ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Gamma Ray Burst ◽

New Era ◽

X Ray ◽

Time Profiles ◽

Random Direction ◽

Wide Range ◽

New Phenomena

Gamma-ray bursts (GRBs) will be recorded as one of the outstanding new phenomena discovered in astronomy this century. About once per day, a burst of gamma rays appears from a random direction on the sky. Often, the burst outshines all other sources of gamma-rays in the sky, combined. This paper reviews some of the key observed phenomenon of bursts in the hard x-ray/gamma-ray region, as observed with the BATSE experiment on the Compton Gamma Ray Observatory. The observed time profiles, spectral properties and durations of gamma-ray bursts cover a wide range. Recent breakthroughs in the observation of gamma-ray burst counterparts and afterglows in other wavelength regions have marked the beginning of a new era in gamma-ray burst research. Those observations are described in following papers in these proceedings.

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Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3090 ◽

2020 ◽

Vol 499 (4) ◽

pp. 5986-5992

Author(s):

Nikhil Sarin ◽

Paul D Lasky ◽

Gregory Ashton

Keyword(s):

Gravitational Wave ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Dipole Radiation ◽

X Ray ◽

Radiative Efficiency ◽

Central Engine ◽

Radiative Losses ◽

Wave Emission ◽

Prompt Emission

ABSTRACT The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$ suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

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