scholarly journals Lorentz Factor Evolution Patterns within Relativistic Jets of GRBs and AGNs

2016 ◽  
Vol 12 (S324) ◽  
pp. 78-81
Author(s):  
Hai-Ming Zhang ◽  
Da-Bin Lin ◽  
Ting-Ting Lin ◽  
Bao-Rong Liu ◽  
Xiao-Li Huang ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Empirical Relation ◽  
Lorentz Factor ◽  
Jet Physics ◽  
Spectral Energy ◽  
Relativistic Jets ◽  
Evolution Pattern ◽  
Relativistic Jet ◽  
Γ Ray

AbstractThe Lorentz factor (Γ) is an important parameter related to the relativistic jet physics. We study the evolution patterns of Γ within gamma-ray burst (GRB) and active galactic nuclear jets for individual GRB 090168, GRB 140508A, and 3C 454.3. By estimating the Γ values for well-separated pulses in GRBs 090618 and 140508A with an empirical relation derived from typical GRBs, we find that the Γ evolution pattern in the two GRBs are different. The increasing-to-coasting evolution pattern of Γ in GRB 090618 likely indicates that the GRB fireball is still being accelerated in the prompt phase. The clear decrease evolution pattern of Γ in GRB 140508A suggests the deceleration of the fireball components. By deriving the Γ value through fitting their spectral energy distribution in different flares of 3C 454.3, a pattern of Γ-tracking-γ-ray flux is clearly found, likely indicating that the observed gamma-ray flares are being due to the Doppler boosting effect to the jet emission.

scholarly journals Temporal correlation between the optical and γ-ray flux variations in the blazar 3C 454.3

2019 ◽  
Vol 486 (2) ◽  
pp. 1781-1795 ◽  
Author(s):  
Bhoomika Rajput ◽  
C S Stalin ◽  
S Sahayanathan ◽  
Suvendu Rakshit ◽  
Amit Kumar Mandal
Keyword(s):  
Spectral Energy Distribution ◽  
Broad Band ◽  
Temporal Correlation ◽  
Lorentz Factor ◽  
Degree Of Polarization ◽  
Spectral Energy ◽  
Long Duration ◽  
Γ Ray ◽  
Optical Flux ◽  
Optical Flare

ABSTRACT Blazars show optical and γ-ray flux variations that are generally correlated, although there are exceptions. Here we present anomalous behaviour seen in the blazar 3C 454.3 based on an analysis of quasi-simultaneous data at optical, ultraviolet, X-ray, and γ-ray energies, spanning about 9 yr from 2008 August to 2017 February. We have identified four time intervals (epochs), A, B, D, and E, when the source showed large-amplitude optical flares. In epochs A and B the optical and γ-ray flares are correlated, while in D and E corresponding flares in γ-rays are weak or absent. In epoch B the degree of optical polarization strongly correlates with changes in optical flux during a short-duration optical flare superimposed on one of long duration. In epoch E the optical flux and degree of polarization are anticorrelated during both the rising and declining phases of the optical flare. We carried out broad-band spectral energy distribution (SED) modelling of the source for the flaring epochs A,B, D, and E, and a quiescent epoch, C. Our SED modelling indicates that optical flares with absent or weak corresponding γ-ray flares in epochs D and E could arise from changes in a combination of parameters, such as the bulk Lorentz factor, magnetic field, and electron energy density, or be due to changes in the location of the γ-ray-emitting regions.

scholarly journals The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413

2019 ◽  
Vol 487 (1) ◽  
pp. 181-197 ◽  
Author(s):  
Daniel Kynoch ◽  
Hermine Landt ◽  
Martin J Ward ◽  
Chris Done ◽  
Catherine Boisson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Uv Spectroscopy ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Physical Models ◽  
Spectral Energy ◽  
Narrow Line ◽  
Relativistic Jet ◽  
Γ Ray ◽  
Apply Physical

ABSTRACT We present a multifrequency study of PKS J1222+0413 (4C +04.42), currently the highest redshift γ-ray emitting narrow-line Seyfert 1 (γ-NLS1). We assemble a broad spectral energy distribution (SED) including previously unpublished datasets: X-ray data obtained with the NuSTAR and Neil Gehrels Swift observatories; near-infrared, optical, and UV spectroscopy obtained with VLT X-shooter; and multiband radio data from the Effelsberg telescope. These new observations are supplemented by archival data from the literature. We apply physical models to the broad-band SED, parametrizing the accretion flow and jet emission to investigate the disc–jet connection. PKS J1222+0413 has a much greater black hole mass than most other NLS1s, MBH ≈ 2 × 108 M$\odot$, similar to those found in flat spectrum radio quasars (FSRQs). Therefore this source provides insight into how the jets of γ-NLS1s relate to those of FSRQs.

scholarly journals Tracing the high energy emission of γ-ray detected radio loud quasars

2014 ◽  
Vol 10 (S313) ◽  
pp. 225-230
Author(s):  
Giulia Migliori
Keyword(s):  
Spectral Energy Distribution ◽  
High Energy ◽  
Host Galaxy ◽  
Spectral Energy ◽  
X Ray ◽  
Relativistic Jet ◽  
Quasar Jets ◽  
Γ Ray ◽  
High Energy Emission ◽  
Jet Power

AbstractWe present a multiwavelength study of the core and relativistic jet of the radio loud (RL) quasar RGB J1512+020A (z=0.20). We report the discovery of a bright, 13” extended X-ray jet with a short Chandra observation. We discuss the origin of the jet X-ray emission and its properties in comparison with sample of X-ray quasar jets. The broadband core spectrum is contributed by the emission of the central quasar, by a blazar component, responsible for the γ-ray emission detected by Fermi, and by the host galaxy. We model the non-thermal blazar spectral energy distribution (SED) and constrain the total jet power. The jet power inferred from the blazar SED modeling is in agreement with the values obtained from the total radio power, pointing to a jet that efficiently carries its power up to kiloparsec scales. The quasar emission appears intrinsically weak in the optical-UV band. The disk luminosity estimated from the broad emission lines is lower than the jet power, in agreement with recent results from observations and theory.

scholarly journals Extreme and high synchrotron peak blazars beyond 4FGL: The 2BIGB γ-ray catalogue

2020 ◽  
Vol 493 (2) ◽  
pp. 2438-2451
Author(s):  
B Arsioli ◽  
Y-L Chang ◽  
B Musiimenta
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Data Repositories ◽  
Total Contribution ◽  
Public Data ◽  
Γ Ray

ABSTRACT This paper presents the results of a γ-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP and HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11 yr of observations in the energy range between 500 MeV and 500 GeV, which results in 1160 γ-ray signatures detected down to the TS=9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS (Test Statistic) maps, and represent an improvement of ∼25 per cent for the number of EHSP and HSP currently described in γ-rays. We build the γ-ray spectral energy distribution (SED) for all the 1160 2BIGB sources, plot the corresponding γ-ray logN−logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ∼33 per cent at 100 GeV. Also, we show that the γ-ray detectability improves according to the synchrotron peak flux as represented by the figure of merit parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for ‘Second Brazil-ICRANet Gamma-ray Blazars’ catalogue, and all the broad-band models and SED data points will be available on public data repositories (OpenUniverse, GitHub, and Brazilian Science Data Center-BSDC).

scholarly journals GRB 190114C: from prompt to afterglow?

2019 ◽  
Vol 626 ◽  
pp. A12 ◽  
Author(s):  
M. E. Ravasio ◽  
G. Oganesyan ◽  
O. S. Salafia ◽  
G. Ghirlanda ◽  
G. Ghisellini ◽  
...  
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Onset Time ◽  
Lorentz Factor ◽  
Spectral Energy ◽  
Large Area ◽  
Spectral Evolution ◽  
Gamma Ray Burst

GRB 190114C is the first gamma-ray burst detected at very high energies (VHE, i.e., > 300 GeV) by the MAGIC Cherenkov telescope. The analysis of the emission detected by the Fermi satellite at lower energies, in the 10 keV–100 GeV energy range, up to ∼50 s (i.e., before the MAGIC detection) can hold valuable information. We analyze the spectral evolution of the emission of GRB 190114C as detected by the Fermi Gamma-Ray Burst Monitor (GBM) in the 10 keV–40 MeV energy range up to ∼60 s. The first 4 s of the burst feature a typical prompt emission spectrum, which can be fit by a smoothly broken power-law function with typical parameters. Starting on ∼4 s post-trigger, we find an additional nonthermal component that can be fit by a power law. This component rises and decays quickly. The 10 keV–40 MeV flux of the power-law component peaks at ∼6 s; it reaches a value of 1.7 × 10−5 erg cm−2 s−1. The time of the peak coincides with the emission peak detected by the Large Area Telescope (LAT) on board Fermi. The power-law spectral slope that we find in the GBM data is remarkably similar to that of the LAT spectrum, and the GBM+LAT spectral energy distribution seems to be consistent with a single component. This suggests that the LAT emission and the power-law component that we find in the GBM data belong to the same emission component, which we interpret as due to the afterglow of the burst. The onset time allows us to estimate that the initial jet bulk Lorentz factor Γ0 is about 500, depending on the assumed circum-burst density.

scholarly journals A new lepto-hadronic model applied to the first simultaneous multiwavelength data set for Cygnus X–1

2020 ◽  
Vol 500 (2) ◽  
pp. 2112-2126
Author(s):  
D Kantzas ◽  
S Markoff ◽  
T Beuchert ◽  
M Lucchini ◽  
A Chhotray ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
Electromagnetic Spectrum ◽  
X Rays ◽  
Relativistic Jets ◽  
Data Set ◽  
Dynamical Properties

ABSTRACT Cygnus X–1 is the first Galactic source confirmed to host an accreting black hole. It has been detected across the entire electromagnetic spectrum from radio to GeV gamma-rays. The source’s radio through mid-infrared radiation is thought to originate from the relativistic jets. The observed high degree of linear polarization in the MeV X-rays suggests that the relativistic jets dominate in this regime as well, whereas a hot accretion flow dominates the soft X-ray band. The origin of the GeV non-thermal emission is still debated, with both leptonic and hadronic scenarios deemed to be viable. In this work, we present results from a new semi-analytical, multizone jet model applied to the broad-band spectral energy distribution of Cygnus X–1 for both leptonic and hadronic scenarios. We try to break this degeneracy by fitting the first-ever high-quality, simultaneous multiwavelength data set obtained from the CHOCBOX campaign (Cygnus X–1 Hard state Observations of a Complete Binary Orbit in X-rays). Our model parametrizes dynamical properties, such as the jet velocity profile, the magnetic field, and the energy density. Moreover, the model combines these dynamical properties with a self-consistent radiative transfer calculation including secondary cascades, both of leptonic and hadronic origin. We conclude that sensitive TeV gamma-ray telescopes like Cherenkov Telescope Array (CTA) will definitively answer the question of whether hadronic processes occur inside the relativistic jets of Cygnus X–1.

scholarly journals Relativistic Jets in Gamma-Ray-Emitting Narrow-Line Seyfert 1 Galaxies

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 87 ◽  
Author(s):  
Filippo D’Ammando
Keyword(s):  
Black Hole ◽  
Gamma Ray ◽  
Broad Band ◽  
Jet Physics ◽  
Host Galaxy ◽  
Narrow Line ◽  
Relativistic Jets ◽  
Large Area ◽  
Small Black Hole ◽  
Γ Ray

Before the launch of the Fermi Gamma-ray Space Telescope satellite only two classes of active galactic nuclei (AGN) were known to generate relativistic jets and thus to emit up to the γ -ray energy range: blazars and radio galaxies, both hosted in giant elliptical galaxies. The discovery by the Large Area Telescope (LAT) on-board the Fermi satellite of variable γ -ray emission from a few radio-loud narrow-line Seyfert 1 galaxies (NLSy1) revealed the presence of an emerging third class of AGN with powerful relativistic jets. Considering that NLSy1 are usually hosted in late-type galaxies with relatively small black hole masses, this finding opened new challenging questions about the nature of these objects, the disc/jet connection, the emission mechanisms at high energies, and the formation of relativistic jets. In this review, I will discuss the broad-band properties of the γ -ray-emitting NLSy1 included in the Fourth Fermi LAT source catalog, highlighting major findings and open questions regarding jet physics, black hole mass estimation, host galaxy and accretion process of these sources in the Fermi era.

scholarly journals On the Origin of Gamma-Ray Flares from Bright Fermi Blazars

2021 ◽  
Vol 257 (2) ◽  
pp. 37
Author(s):  
Vaidehi S. Paliya ◽  
M. Böttcher ◽  
Mark Gurwell ◽  
C. S. Stalin
Keyword(s):  
Energy Distribution ◽  
Magnetic Reconnection ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Pivotal Role ◽  
Jet Physics ◽  
Spectral Energy ◽  
Electron Population ◽  
Doppler Factor

Abstract The origin of γ-ray flares observed from blazars is one of the major mysteries in jet physics. We have attempted to address this problem following a novel spectral energy distribution (SED) fitting technique that explored the flaring patterns identified in the broadband SEDs of two γ-ray bright blazars, 3C 279 (z = 0.54) and 3C 454.3 (z = 0.86), using near-simultaneous radio-to-γ-ray observations. For both sources, the γ-ray flux strongly correlates with the separation of the SED peaks and the Compton dominance. We propose that spectral hardening of the radiating electron population and/or enhancement of the Doppler factor can naturally explain these observations. In both cases, magnetic reconnection may play a pivotal role in powering the luminous γ-ray flares.

scholarly journals Rise and fall of the high-energy afterglow emission of GRB 180720B

2020 ◽  
Vol 636 ◽  
pp. A55 ◽  
Author(s):  
M. Ronchi ◽  
F. Fumagalli ◽  
M. E. Ravasio ◽  
G. Oganesyan ◽  
M. Toffano ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Energy Range ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Lorentz Factor ◽  
High Energy ◽  
Smooth Transition ◽  
Spectral Energy ◽  
Emission Region ◽  
Synchrotron Emission

The gamma-ray burst (GRB) 180720B is one of the brightest events detected by the Fermi satellite and the first GRB detected by the H.E.S.S. telescope above 100 GeV, at around ten hours after the trigger time. We analysed the Fermi (GBM and LAT) and Swift (XRT and BAT) data and describe the evolution of the burst spectral energy distribution in the 0.5 keV–10 GeV energy range over the first 500 s of emission. We reveal a smooth transition from the prompt phase, dominated by synchrotron emission in a moderately fast cooling regime, to the afterglow phase whose emission has been observed from the radio to the gigaelectronvolts energy range. The LAT (0.1–100 GeV) light curve initially rises (FLAT ∝ t2.4), peaks at ∼78 s, and falls steeply (FLAT ∝ t−2.2) afterwards. The peak, which we interpret as the onset of the fireball deceleration, allows us to estimate the bulk Lorentz factor Γ0 ∼ 150 (300) under the assumption of a circum-burst medium with a wind-like (homogeneous) density profile. We derive a flux upper limit in the LAT energy range at the time of H.E.S.S. detection, but this does not allow us to unveil the nature of the high-energy component observed by H.E.S.S. We fit the prompt spectrum with a physical model of synchrotron emission from a non-thermal population of electrons. The 0–35 s spectrum after its EF(E) peak (at 1–2 MeV) is a steep power law extending to hundreds of megaelectronvolts. We derive a steep slope of the injected electron energy distribution N(γ) ∝ γ−5. Our fit parameters point towards a very low magnetic field (B′ ∼ 1 G) in the emission region.

scholarly journals TeV Gamma–Ray Absorption and the Intergalactic Infrared Background

2001 ◽  
Vol 204 ◽  
pp. 135-149 ◽  
Author(s):  
F. W. Stecker
Keyword(s):  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
High Energy ◽  
Spectral Energy ◽  
Empirical Modelling ◽  
Infrared Spectral ◽  
Infrared Background ◽  
Γ Ray

In this paper, I will take a synoptic approach to determining the intergalactic infrared radiation field (IIRF). This approach draws on both the multi-TeV γ-ray observations and the infrared background observations and relates them via the semi-empirical modelling method of Malkan & Stecker. I discuss the evidence for an intergalactic infrared background obtained by an analysis of the HEGRA observations of the high energy γ-ray spectrum of Mrk 501 and from constraints from Mrk 421 deduced from the Whipple air Cherenkov telescope results. I will show that this evidence is in accord with the predictions made by Malkan & Stecker (1998) for the intergalactic infrared spectral energy distribution produced by galaxies. The Malkan-Stecker predictions are also in excellent agreement with mid-infrared galaxy counts. However, there may be potential problems relating these predictions with the results of the analysis of COBE–DIRBE far infrared data. The γ-ray and COBE–DIRBE observations may also need to be reconciled. I will discuss possible ways to resolve this situation including a partial nullification of the γ-ray absorption process which can hypothetically occur if Lorentz invariance is broken.

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