scholarly journals Spectral puzzle of the off-axis gamma-ray burst in GW170817

2019 ◽  
Vol 487 (4) ◽  
pp. 4884-4889 ◽  
Author(s):  
Kunihito Ioka ◽  
Takashi Nakamura
Keyword(s):  
Neutron Stars ◽  
Gamma Ray ◽  
Event Rate ◽  
Gamma Ray Bursts ◽  
Line Of Sight ◽  
Viewing Angle ◽  
Central Engine ◽  
Relativistic Jet ◽  
Primary Axis ◽  
First Time

ABSTRACT Gravitational waves from a merger of two neutron stars (NSs) were discovered for the first time in GW170817, together with diverse electromagnetic counterparts, providing a direct clue to the origin of short gamma-ray bursts (sGRBs). The associated sGRB 170817A was much fainter than typical, suggesting off-axis emission from a relativistic jet. However the observed prompt spectrum is inconsistent with the spectral (Amati) relation and causes the compactness problem in the simplest off-axis model. We suggest that this spectral and energetic puzzle of GRB170817A is explained if the origin of the off-axis emission arises from the off-centre jet. This emission location is generally created by the product of the rapidly declining (with angle) jet energy and the increasing beaming term. Hence the region of most luminous emission for an off-axis observer is neither the jet core around the primary axis, nor the line of sight at the viewing angle. The off-centre jet could be loaded with baryon or cocoon. The off-axis model predicts that roughly ${\sim } 10{{\ \rm per\ cent}}$ events are brighter at smaller viewing angles than sGRB 170817A, although the exact event rate sensitively depends on uncertainties of the off-centre structure. The model also predicts outliers to Amati relation, providing future tests to reveal the central engine activities.

scholarly journals Magnetar as Central Engine of Gamma-Ray Bursts: Quasi-universal Jet, Event Rate, and X-Ray Luminosity Function of Dipole Radiations

2020 ◽  
Vol 894 (1) ◽  
pp. 52
Author(s):  
Wen-Jin Xie ◽  
Le Zou ◽  
Hong-Bang Liu ◽  
Shan-Qin Wang ◽  
En-Wei Liang
Keyword(s):  
Luminosity Function ◽  
Gamma Ray ◽  
Event Rate ◽  
Gamma Ray Bursts ◽  
X Ray ◽  
Central Engine

scholarly journals Models for GRBs and diverse transients

2007 ◽  
Vol 365 (1854) ◽  
pp. 1129-1139 ◽  
Author(s):  
S.E Woosley ◽  
Weiqun Zhang
Keyword(s):  
Massive Star ◽  
Loss Rate ◽  
Gamma Ray ◽  
Mass Loss Rate ◽  
Variable Mass ◽  
Gamma Ray Bursts ◽  
Basic Model ◽  
Central Engine ◽  
Relativistic Jet ◽  
Natural Inclination

The observational diversity of gamma-ray bursts (GRBs) has been increasing, and the natural inclination is a proliferation of models. We explore the possibility that at least part of this diversity is a consequence of a single basic model for the central engine operating in a massive star of variable mass, differential rotation rate and mass loss rate. Whatever that central engine may be—and here the collapsar is used as a reference point—it must be capable of generating both a narrowly collimated, highly relativistic jet to make the GRB and a wide angle, sub-relativistic outflow responsible for exploding the star and making the supernova bright. To some extent, the two components may vary independently; therefore, it is possible to produce a variety of jet energies and supernova luminosities. We explore, in particular, the production of low-energy bursts and find a lower limit of approximately 10 48  erg s −1 to the power required for a jet to escape a massive star before that star either explodes or is accreted. Lower energy bursts and ‘suffocated’ bursts may be particularly prevalent when the metallicity is high, i.e. in the modern universe at low red shift.

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

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.

The melting of neutron stars' crystalline cores and gamma-ray bursts

1976 ◽  
Vol 39 (1) ◽  
pp. 243-249 ◽  
Author(s):  
Ju. M. Bruk ◽  
K. I. Kugel
Keyword(s):  
Neutron Stars ◽  
Gamma Ray ◽  
Gamma Ray Bursts

Gamma-ray bursts from galactic neutron stars?

1989 ◽  
Vol 10 (2) ◽  
pp. 27-37
Author(s):  
D. Hartmann ◽  
R.I. Epstein ◽  
S.E. Woosley
Keyword(s):  
Neutron Stars ◽  
Gamma Ray ◽  
Gamma Ray Bursts

scholarly journals Optical Afterglows as Probes for the Central Engine and Fireball of Gamma-Ray Bursts

2012 ◽  
Vol 8 (S290) ◽  
pp. 263-264
Author(s):  
Liang Li ◽  
En-Wei Liang ◽  
He Gao ◽  
Bing Zhang
Keyword(s):  
Statistical Analysis ◽  
Gamma Rays ◽  
Density Profile ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Gamma Ray Bursts ◽  
Prompt Gamma ◽  
Medium Density ◽  
Central Engine ◽  
Prompt Emission

AbstractWell-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are compiled from literature. We identify possible emission components based on our empirical fits and present statistical analysis for these components. We find that the flares are related to prompt emission, suggesting that they could have the same origin in different episodes. The shallow decay segment is not correlated with prompt gamma-rays. It likely signals a long-lasting injected wind from GRB central engines. Early after onset peak is closely related with prompt emission. The ambient medium density profile is likely n ∝ r−1. No correlation between the late re-brightening bump and prompt gamma-rays or the onset bump is found. They may be from another jet component.

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