scholarly journals The FRB–SGR connection

2020 ◽  
Vol 499 (2) ◽  
pp. 2319-2326 ◽  
Author(s):  
J I Katz
Keyword(s):  
Compton Scattering ◽  
Gamma Ray ◽  
Coulomb Repulsion ◽  
Lorentz Factor ◽  
Common Source ◽  
Curvature Radiation ◽  
Pattern Speed ◽  
Statistical Argument ◽  
Fast Radio Burst ◽  
Soft Gamma Repeater

ABSTRACT The discovery that the Galactic Soft Gamma Repeater (SGR) 1935+2154 emitted Fast Radio Burst (FRB) 200428 simultaneous with a gamma-ray flare, demonstrated the common source and association of these phenomena. If FRB radio emission is the result of coherent curvature radiation, the net charge of the radiating ‘bunches’ or waves may be inferred from the radiated fields, independent of the mechanism by which the bunches are produced. A statistical argument indicates that the radiating bunches must have a Lorentz factor ⪆ 10. The observed radiation frequencies indicate that their phase velocity (pattern speed) corresponds to Lorentz factors ⪆ 100. Coulomb repulsion implies that the electrons making up these bunches have yet larger Lorentz factors, limited by their incoherent curvature radiation. These electrons also Compton scatter the soft gamma-rays of the SGR. In FRB 200428, the power they radiated coherently at radio frequencies exceeded that of Compton scattering, but in more luminous SGR outbursts, Compton scattering dominates, precluding the acceleration of energetic electrons. This explains the absence of a FRB associated with the giant 2004 December 27 outburst of SGR 1806−20. SGR with luminosity ≳ 1042 erg s–1 are predicted not to emit FRB, while those of lesser luminosity can do so. ‘Superbursts’ like FRB 200428 are produced when narrowly collimated FRB are aligned with the line of sight; they are unusual, but not rare, and ‘cosmological’ FRB may be superbursts.

scholarly journals Detection of the Geminga pulsar with MAGIC hints at a power-law tail emission beyond 15 GeV

2020 ◽  
Vol 643 ◽  
pp. L14
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Gamma Ray ◽  
Low Energy ◽  
Significance Level ◽  
Inverse Compton Scattering ◽  
Curvature Radiation ◽  
Sensitivity Range ◽  
Inverse Compton ◽  
First Time

We report the detection of pulsed gamma-ray emission from the Geminga pulsar (PSR J0633+1746) between 15 GeV and 75 GeV. This is the first time a middle-aged pulsar has been detected up to these energies. Observations were carried out with the MAGIC telescopes between 2017 and 2019 using the low-energy threshold Sum-Trigger-II system. After quality selection cuts, ∼80 h of observational data were used for this analysis. To compare with the emission at lower energies below the sensitivity range of MAGIC, 11 years of Fermi-LAT data above 100 MeV were also analysed. From the two pulses per rotation seen by Fermi-LAT, only the second one, P2, is detected in the MAGIC energy range, with a significance of 6.3σ. The spectrum measured by MAGIC is well-represented by a simple power law of spectral index Γ = 5.62 ± 0.54, which smoothly extends the Fermi-LAT spectrum. A joint fit to MAGIC and Fermi-LAT data rules out the existence of a sub-exponential cut-off in the combined energy range at the 3.6σ significance level. The power-law tail emission detected by MAGIC is interpreted as the transition from curvature radiation to Inverse Compton Scattering of particles accelerated in the northern outer gap.

scholarly journals e±-rich GRB Fireball and Infrared Flashes

2003 ◽  
Vol 214 ◽  
pp. 331-332
Author(s):  
Zhuo Li ◽  
Z. G. Dai ◽  
T. Lu
Keyword(s):  
Gamma Ray ◽  
Lorentz Factor ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Rapid Response ◽  
Model Parameters ◽  
Wide Range ◽  
Very High Energy ◽  
Very High

Gamma-ray bursts (GRBs) are believed to originate from ultra-relativistic fireballs, with initial Lorentz factor η ∼ 102 − 103. However very high energy photons may still suffer from γγ interaction. We show here that in a wide range of model parameters, the resulting pairs may dominate electrons associated with the fireball baryons. This may provide an explanation for the rarity of prompt optical detections. A rapid response to the GRB trigger at the IR band would detect such a strong flash.

Saturated Compton scattering models for the soft gamma-ray repeater bursts

1997 ◽  
Author(s):  
I. A. Smith ◽  
E. P. Liang ◽  
A. Crider ◽  
D. Lin ◽  
M. Kusunose
Keyword(s):  
Compton Scattering ◽  
Gamma Ray

scholarly journals An Explanation for Pulsar Mode Changing Phenomenon

1996 ◽  
Vol 160 ◽  
pp. 225-226
Author(s):  
B. Zhang ◽  
G.J. Qiao ◽  
W.P. Lin ◽  
J.L. Han
Keyword(s):  
Resonant Frequency ◽  
Compton Scattering ◽  
High Energy ◽  
Switching Effect ◽  
Inverse Compton Scattering ◽  
Thermal Peak ◽  
Curvature Radiation ◽  
Inverse Compton ◽  
High Energy Particles

AbstractThere are three mechanisms to cause pulsar inner gap breakdown: the inverse Compton scattering (ICS) of the high energy particles off the thermal-peak photons, off the resonant-frequency photons and the curvature radiation (CR). The pulsar mode-changing phenomenon can be interpreted as a switching effect between theresonant ICS sparking modeand thethermal ICS sparking mode.

scholarly journals A neutron star–white dwarf binary model for periodically active fast radio burst sources

2020 ◽  
Vol 497 (2) ◽  
pp. 1543-1546 ◽  
Author(s):  
Wei-Min Gu ◽  
Tuan Yi ◽  
Tong Liu
Keyword(s):  
Neutron Star ◽  
Radio Burst ◽  
Duty Cycle ◽  
White Dwarf ◽  
Burst Activity ◽  
Compact Binary ◽  
Binary Model ◽  
Duty Cycles ◽  
Curvature Radiation ◽  
Fast Radio Burst

ABSTRACT We propose a compact binary model with an eccentric orbit to explain periodically active fast radio burst (FRB) sources, where the system consists of a neutron star (NS) with strong dipolar magnetic fields and a magnetic white dwarf (WD). In our model, the WD fills its Roche lobe at periastron, and mass transfer occurs from the WD to the NS around this point. The accreted material may be fragmented into a number of parts, which arrive at the NS at different times. The fragmented magnetized material may trigger magnetic reconnection near the NS surface. The electrons can be accelerated to an ultrarelativistic speed, and therefore the curvature radiation of the electrons can account for the burst activity. In this scenario, the duty cycle of burst activity is related to the orbital period of the binary. We show that such a model may work for duty cycles roughly from 10 min to 2 d. For the recently reported 16.35-d periodicity of FRB 180916.J0158 + 65, our model does not naturally explain such a long duty cycle, since an extremely high eccentricity (e > 0.95) is required.

scholarly journals Statistical properties of magnetar bursts and FRB 121102

2019 ◽  
Vol 491 (1) ◽  
pp. 1498-1505 ◽  
Author(s):  
Yingjie Cheng ◽  
G Q Zhang ◽  
F Y Wang
Keyword(s):  
Power Law ◽  
Time Distribution ◽  
Statistical Properties ◽  
Occurrence Rate ◽  
Waiting Time Distribution ◽  
X Ray ◽  
Central Engine ◽  
Fast Radio Burst ◽  
Soft Gamma Repeater ◽  
Critical Process

ABSTRACT In this paper, we present statistics of soft gamma repeater (SGR) bursts from SGR J1550−5418, SGR 1806−20, and SGR 1900+14 by adding new bursts from Kırmızıbayrak et al. detected with the Rossi X-ray Timing Explorer. We find that the fluence distributions of magnetar bursts are well described by power-law functions with indices 1.84, 1.68, and 1.65 for SGR J1550−5418, SGR 1806−20, and SGR 1900+14, respectively. The duration distributions of magnetar bursts also show power-law forms. Meanwhile, the waiting time distribution can be described by a non-stationary Poisson process with an exponentially growing occurrence rate. These distributive features indicate that magnetar bursts can be regarded as a self-organizing critical process. We also compare these distributions with the repeating fast radio burst (FRB) 121102. The statistical properties of repeating FRB 121102 are similar with magnetar bursts, combining with the large required magnetic field (B ≥ 1014 G) of neutron star for FRB 121102, which indicates that the central engine of FRB 121102 may be a magnetar.

scholarly journals MAGNETOHYDRODYNAMIC EFFECTS IN RELATIVISTIC EJECTA

2010 ◽  
Vol 19 (06) ◽  
pp. 991-996
Author(s):  
YOSUKE MIZUNO ◽  
BING ZHANG ◽  
BRUNO GIACOMAZZO ◽  
KEN-ICHI NISHIKAWA ◽  
PHILIP E. HARDEE ◽  
...  
Keyword(s):  
Rarefaction Wave ◽  
Gamma Ray ◽  
Flux Ratio ◽  
Lorentz Factor ◽  
Magnetic Pressure ◽  
Initial Value ◽  
Reverse Shock ◽  
Thermal Pressure ◽  
Wave Regime ◽  
Forward Shock

We study the problem of deceleration of an arbitrarily magnetized relativistic ejecta in a static unmagnetized medium and its connection to the physics of gamma-ray bursts (GRBs). By computing exact solutions of the Riemann problem describing this scenario, we find that with the same initial Lorentz factor, the reverse shock becomes progressively weaker with increasing magnetization parameter σ (the Poynting-to-kinetic flux ratio). The reverse shock becomes a rarefaction wave when σ exceeds a critical value defined by the balance between magnetic pressure in the ejecta and thermal pressure in the forward shock. In the rarefaction wave regime, the rarefied region is accelerated to a Lorentz factor that is significantly larger than the initial value due to the strong magnetic pressure in the ejecta. We discuss the implications for models of GRBs.

Sign in / Sign up

Export Citation Format

Share Document