Studying the Influence of External Photon Fields on Blazar Spectra Using a One-Zone Hadro-Leptonic Time-Dependent Model

Zacharias, M.

doi:10.3390/physics3040069

Cited by 5 publications

(9 citation statements)

References 36 publications

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“…We use the OneHaLe code (Zacharias 2021;Zacharias et al 2022, see the appendix for a brief description) to model the timedependent evolution of the blob. In order to comply with some of the assumptions above, we have to slightly tweak the code.…”

Section: Simulationsmentioning

confidence: 99%

“…In the present work, we specifically consider the effect of γ-γ pair production on the evolution of the particle distribution and the photon fluxes. In particular, bright external photon fields can have a major influence, as they provide a significant amount of absorption for the γ rays of the emission region (e.g., Zacharias 2021). However, as these photon fields are only present in the direct vicinity of the black hole, the optical thickness for γ rays changes over time, as the blob moves down the jet.…”

Section: Introductionmentioning

confidence: 99%

“…In Sect. 3, we use the numerical code OneHaLe (Zacharias 2021;Zacharias et al 2022) to derive the light curves of a realistic simulation based on the parameters of PKS 1510-089, which is known for its bright external photon fields. We present our conclusions in Sect.…”

Section: Introductionmentioning

confidence: 99%

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Exploring the evolution of the particle distribution and the cascade in a moving, expanding emission region in blazar jets

Zacharias

2023

A&A

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Aims. Models built to explain blazar flares display a broad variety of results. In this work, we study the flare profile induced by a moving and expanding blob, with a special emphasis on γ-γ pair production. Methods. We first developed a simple semi-analytical model to study the evolution of the particle distribution in the expanding blob and show the influence of the pair production. In a second step, we produced a realistic simulation using the OneHaLe code based upon the parameters of PKS 1510-089.Results. The applied semi-analytical model shows that the pair production significantly influences the flare evolution, while the opening angle and the expansion can prolong flares considerably. The simulation based on PKS 1510-089 indicates that flares of a moving, expanding blob result in strongly wavelength-dependent light curves that may include delayed, secondary flares. Conclusions. A moving, expanding blob can cause significant flaring events, with a broad variety in terms of the light curve profiles. High-cadence multiwavelength observations are necessary for deriving the details behind the cause of the flare. Extended observations beyond the initial burst may provide important information on the opening angle and the particle content attributed to delayed secondary flares in some energy bands.

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Section: Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Exploring the evolution of the particle distribution and the cascade in a moving, expanding emission region in blazar jets

Zacharias

2023

A&A

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“…A key aspect to investigate in this scenario is to understand the role of the adiabatic expansion of the emitting region, and the consequences in terms of variation of the synchrotron selfabsorption frequency (SSA), as presented in the seminal works by McCray (1969) and van der Laan (1969) and more recently Boula et al (2018), Potter (2018), and Boula & Mastichiadis (2022). A recent analysis by Zacharias (2021) investigates the adiabatic expansion scenario, but focuses on the impact of the expansion on the usual 'double-humped' SED shape rather than on the possible relation with the radio-γ delay.…”

Section: Introductionmentioning

confidence: 99%

Radio-γ-ray response in blazars as a signature of adiabatic blob expansion

Tramacere

Sliusar

Walter

et al. 2022

A&A

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Context. Multi-wavelength light curves in long-term campaigns show that, for several blazars, the radio emission occurs with a significant delay with respect to the γ-ray band, with timescales ranging from weeks to years. Such observational evidence has long been a matter of debate, and is usually interpreted as a signature of the γ-ray emission originating upstream in the jet, with the emitting region becoming radio transparent at larger scales. Aims. In this paper, we show, by means of self-consistent numerical modelling, that the adiabatic expansion of a relativistic blob can explain these delays, reproducing lags compatible with the observed timescales. Methods. We use the JetSeT framework to reproduce the numerical modelling of the radiative and accelerative processes, reproducing the temporal evolution of a single blob, from the initial flaring activity and the subsequent expansion. We follow the spectral evolution and the corresponding light curves, investigating the relations among the observed parameters, rise time, delay, and decay time, and we identify the link with physical parameters. Results. We find that, when adiabatic expansion is active, lags due to the shift of the synchrotron frequency occur. The corresponding time lags have an offset equal to the distance in time between the flaring onset and the beginning of the expansion, whilst the rising and decaying timescales depend on the velocity of the expansion and on the time required for the source to exhibit a synchrotron self-absorption frequency below the relevant radio spectral window. We derive an inter-band response function, embedding the aforementioned parameters, and we investigate the effects of the competitions between radiative and adiabatic cooling timescales on the response. We apply the response function to long-term radio and γ-ray light curves of Mrk 421, Mrk 501, and 3C 273, finding satisfactory agreement on the log-term behaviour, and we use a Monte Carlo Markov chain approach to estimate some relevant physical parameters. We discuss applications of the presented analysis to polarization measurements and to jet collimation profile kinematics. The collimation profiles observed in radio images are in agreement with the prediction from our model.

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“…(2022). A recent analysis by Zacharias (2021) investigates the adiabatic expansion scenario, but focuses on the impact of the expansion on the usual 'double-humped' SED shape rather than on the possible relation with the radio−γ delay.…”

Section: Introductionmentioning

confidence: 99%

Radio$-γ-$ray response in blazars as a signature of adiabatic blob expansion

Tramacere,

Sliusar,

Walter

et al. 2021

Preprint

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Context. Multi-wavelength light curves in long-term campaigns show that, for several blazars, the radio emission occurs with a significant delay with respect to the γ-ray band, with timescales ranging from weeks to years. Such observational evidence has long been a matter of debate, and is usually interpreted as a signature of the γ-ray emission originating upstream in the jet, with the emitting region becoming radio transparent at larger scales. Aims. In this paper, we show, by means of self-consistent numerical modelling, that the adiabatic expansion of a relativistic blob can explain these delays, reproducing lags compatible with the observed timescales. Methods. We use the JetSeT framework to reproduce the numerical modelling of the radiative and accelerative processes, reproducing the temporal evolution of a single blob, from the initial flaring activity and the subsequent expansion. We follow the spectral evolution and the corresponding light curves, investigating the relations among the observed parameters, rise time, delay, and decay time, and we identify the link with physical parameters. Results. We find that, when adiabatic expansion is active, lags due to the shift of the synchrotron frequency occur. The corresponding time lags have an offset equal to the distance in time between the flaring onset and the beginning of the expansion, whilst the rising and decaying timescales depend on the velocity of the expansion and on the time required for the source to exhibit a synchrotron self-absorption frequency below the relevant radio spectral window. We derive an inter-band response function, embedding the aforementioned parameters, and we investigate the effects of the competitions between radiative and adiabatic cooling timescales on the response. We apply the response function to long-term radio and γ−ray light curves of Mrk 421, Mrk 501, and 3C 273, finding satisfactory agreement on the log-term behaviour, and we use a Monte Carlo Markov Chain approach to estimate some relevant physical parameters. We discuss applications of the presented analysis to polarization measurements and to jet collimation profile kinematics. The collimation profiles observed in radio images are in agreement with the prediction from our model.

show abstract

Studying the Influence of External Photon Fields on Blazar Spectra Using a One-Zone Hadro-Leptonic Time-Dependent Model

Cited by 5 publications

References 36 publications

Exploring the evolution of the particle distribution and the cascade in a moving, expanding emission region in blazar jets

Exploring the evolution of the particle distribution and the cascade in a moving, expanding emission region in blazar jets

Radio-γ-ray response in blazars as a signature of adiabatic blob expansion

Radio$-γ-$ray response in blazars as a signature of adiabatic blob expansion

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