Formation of very hard electron and gamma-ray spectra of flat-spectrum radio quasars in the fast-cooling regime

Yan, Dahai; Zhang, Li; Zhang, Shuang‐Nan

doi:10.1093/mnras/stw739

Cited by 12 publications

(8 citation statements)

References 63 publications

(86 reference statements)

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“…Furthermore, more physical processes could be considered instantly. For example, the scattering of electrons by various external radiation fields (Yan et al 2016) may also be an important cooling mechanism. Additionally, the electrons that are not efficiently accelerated (the low-energy electrons of Maxwellian distribution) may provide considerable lowenergy seed photons.…”

Section: Discussionmentioning

confidence: 99%

Low-energy Spectra of Gamma-Ray Bursts from Cooling Electrons

Geng

Huang

et al. 2018

ApJS

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The low-energy spectra of gamma-ray bursts' (GRBs) prompt emission are closely related to the energy distribution of electrons, which is further regulated by their cooling processes. We develop a numerical code to calculate the evolution of the electron distribution with given initial parameters, in which three cooling processes (i.e., adiabatic, synchrotron and inverse Compton cooling) and the effect of decaying magnetic field are coherently considered. A sequence of results are presented by exploring the plausible parameter space for both the fireball and the Poynting-flux-dominated regime. Different cooling patterns for the electrons can be identified and they are featured by a specific dominant cooling mechanism. Our results show that the hardening of the low-energy spectra can be attributed to the dominance of synchrotron self-Compton cooling within the internal shock model, or to decaying synchrotron cooling within the Poynting-flux-dominated jet scenario. These two mechanisms can be distinguished by observing the hard low-energy spectra of isolated short pulses in some GRBs. The dominance of adiabatic cooling can also lead to hard low-energy spectra when the ejecta is moving at an extreme relativistic speed. The information from the time-resolved low-energy spectra can help to probe the physical characteristics of the GRB ejecta via our numerical results.

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Section: Discussionmentioning

confidence: 99%

Low-energy Spectra of Gamma-Ray Bursts from Cooling Electrons

Geng

Huang

et al. 2018

ApJS

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“…For the study of expected multi-wavelength variability in the internal-shock model, we first focus on Flare C (yellow in Figure 2), which is characterized by an almost unchanged Compton dominance compared to the quiescent state during period A. One natural interpretation is that this and other flares closely sample the accelerator/injector (e.g., Yan, Zhang & Zhang 2016). Therefore, such flaring behaviour can plausibly be reproduced by merely increasing the number of radiating non-thermal electrons generated by the shock, thus enhancing the synchrotron and EIC emission at the same rate.…”

Section: C 279 -Flare Cmentioning

confidence: 99%

Multi-wavelength Variability Signatures of Relativistic Shocks in Blazar Jets

Böttcher

Baring

2019

ApJ

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Mildly-relativistic shocks that are embedded in colliding magnetohydrodynamic flows are prime sites for relativistic particle acceleration and production of strongly variable, polarized multi-wavelength emission from relativistic jet sources such as blazars and gamma-ray bursts. The principal energization mechanisms at these shocks are diffusive shock acceleration and shock drift acceleration. In recent work, we had self-consistently coupled shock acceleration and radiation transfer simulations in blazar jets in a basic one-zone scenario. These one-zone models revealed that the observed spectral energy distributions (SEDs) of blazars strongly constrain the nature of the shock layer hydromagnetic turbulence. In this paper, we expand our previous work by including full time dependence and treating two zones, one being the site of acceleration, and the second being a larger emission zone. This construction is applied to multiwavelength flares of the flat spectrum radio quasar 3C 279, fitting snap-shot SEDs and generating light curves that are consistent with observed variability timescales. We also present a generic study for the typical flaring behavior of the BL Lac object Mrk 501. The model predicts correlated variability across all wavebands, but cross-band time lags depending on the type of blazar (FSRQ vs. BL Lac), as well as distinctive spectral hysteresis patterns in all wavelength bands, from mm radio waves to gamma-rays. These evolutionary signatures serve to provide diagnostics on the competition between acceleration and radiative cooling.

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“…A similar strategy, based on an analytical solution to the steady-state electron distribution, was adopted by Lewis et al [52], also requiring a significant reduction of the magnetic field to suppress a simultaneous optical synchrotron flare. Yan et al [53] modelled the orphan-flare SED using a time-dependent single-zone model with rapid electron cooling. However, it is unclear whether a transition from the quiescent to this flaring state may be produced in a natural way.…”

Section: Summary Discussion and Conclusionmentioning

confidence: 99%

A Shock-in-Jet Synchrotron Mirror Model for Blazars

Böttcher

2021

Physics

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Reinhard Schlickeiser has made groundbreaking contributions to various aspects of blazar physics, including diffusive shock acceleration, the theory of synchrotron radiation, the production of gamma-rays through Compton scattering in various astrophysical sources, etc. This paper, describing the development of a self-consistent shock-in-jet model for blazars with a synchrotron mirror feature, is therefore an appropriate contribution to a Special Issue in honor of Reinhard Schlickeiser’s 70th birthday. The model is based on our previous development of a self-consistent shock-in-jet model with relativistic thermal and non-thermal particle distributions evaluated via Monte-Carlo simulations of diffusive shock acceleration, and time-dependent radiative transport. This model has been very successful in modeling spectral variability patterns of several blazars, but has difficulties describing orphan flares, i.e., high-energy flares without a significant counterpart in the low-frequency (synchrotron) radiation component. As a solution, this paper investigates the possibility of a synchrotron mirror component within the shock-in-jet model. It is demonstrated that orphan flares result naturally in this scenario. The model’s applicability to a recently observed orphan gamma-ray flare in the blazar 3C279 is discussed and it is found that only orphan flares with mild (≲ a factor of 2–3) enhancements of the Compton dominance can be reproduced in a synchrotron-mirror scenario, if no additional parameter changes are invoked.

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Formation of very hard electron and gamma-ray spectra of flat-spectrum radio quasars in the fast-cooling regime

Cited by 12 publications

References 63 publications

Low-energy Spectra of Gamma-Ray Bursts from Cooling Electrons

Low-energy Spectra of Gamma-Ray Bursts from Cooling Electrons

Multi-wavelength Variability Signatures of Relativistic Shocks in Blazar Jets

A Shock-in-Jet Synchrotron Mirror Model for Blazars

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