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Journal articles on the topic 'Synchrotron Self Compton (SSC)'

Author: Grafiati

Published: 6 September 2023

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1

BÖTTCHER, MARKUS. "MODELING INTERMEDIATE BL LAC OBJECTS DETECTED BY VERITAS." International Journal of Modern Physics D 19, no. 06 (2010): 873–78. http://dx.doi.org/10.1142/s0218271810017135.

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Modeling implications of recent VERITAS discoveries of Intermediate BL Lac Objects (IBLs) are presented. Leptonic jet models for the IBLs W Comae (z = 0.102) and 3C 66A (z = 0.444) are, in principle, viable with only synchrotron and synchrotron self-Compton (SSC) components, but more plausible parameters can be achieved including an external infrared radiation field as source for Compton upscattering to produce the observed VHE gamma-ray emission. The unknown redshift of PKS 1424+240 makes a theoretical interpretation difficult. A pure SSC model seems to be sufficient to represent its SED, and

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2

Jacovich, Taylor E., Paz Beniamini, and Alexander J. van der Horst. "Modelling synchrotron self-Compton and Klein–Nishina effects in gamma-ray burst afterglows." Monthly Notices of the Royal Astronomical Society 504, no. 1 (2021): 528–42. http://dx.doi.org/10.1093/mnras/stab911.

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ABSTRACT We present an implementation of a self-consistent way of modelling synchrotron self-Compton (SSC) effects in gamma-ray burst afterglows, with and without approximated Klein–Nishina suppressed scattering for the afterglow modelling code boxfit, which is currently based on pure synchrotron emission. We discuss the changes in spectral shape and evolution due to SSC effects, and comment on how these changes affect physical parameters derived from broad-band modelling. We show that SSC effects can have a profound impact on the shape of the X-ray light curve using simulations including thes

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Banasinski, Piotr, та Wlodek Bednarek. "Inhomogeneous SSC model for the γ-ray production in jets of microquasars". Proceedings of the International Astronomical Union 10, S313 (2014): 382–83. http://dx.doi.org/10.1017/s1743921315002537.

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AbstractWe present an inhomogeneous synchrotron self-Compton (SSC) model for active parts of jets in low mass microquasars. We compare results of our model computed, for typical parameters of microquasars, with the sensitivity of Fermi-LAT.

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Yamasaki, Shotaro, and Tsvi Piran. "Analytic modelling of synchrotron self-Compton spectra: Application to GRB 190114C." Monthly Notices of the Royal Astronomical Society 512, no. 2 (2022): 2142–53. http://dx.doi.org/10.1093/mnras/stac483.

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ABSTRACT Observations of TeV emission from early gamma-ray burst (GRB) afterglows revealed the long sought for inverse Compton (IC) upscattering of the lower energy synchrotron. However, it turned out that the long hoped for ability to easily interpret the synchrotron self-Compton (SSC) spectra didn’t materialize. The TeV emission is in the Klein–Nishina (KN) regime and the simple Thomson regime SSC spectrum is modified, complicating the scene. We describe here a methodology to obtain an analytic approximation to an observed spectrum and infer the conditions at the emitting region. The methodo

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BANASIŃSKI, PIOTR, and WLODEK BEDNAREK. "THE OPTICALLY THICK HOMOGENEOUS SSC MODEL: APPLICATION TO RADIO GALAXY NGC 1275." International Journal of Modern Physics: Conference Series 28 (January 2014): 1460205. http://dx.doi.org/10.1142/s2010194514602051.

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We consider the Synchrotron Self-Compton (SSC) model for jets in active galaxies in which produced γ-ray photons can be absorbed in collisions with the synchrotron radiation already at the emission region. In terms of such modified SSC model, we argue that the higher emission stages should be characterised by γ-ray spectra extending to lower energies due to the efficient absorption of the highest energy γ-rays. As an example, we show that different emission stages of the nearby radio galaxy NGC 1275 could be explained by such scenario.

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Fedorova, Elena, Bohdan Hnatyk, Antonino Del Popolo, Anatoliy Vasylenko, and Vadym Voitsekhovskyi. "Non-Thermal Emission from Radio-Loud AGN Jets: Radio vs. X-rays." Galaxies 10, no. 1 (2022): 6. http://dx.doi.org/10.3390/galaxies10010006.

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We consider the sample of 55 blazars and Seyferts cross-correlated from the Planck all-sky survey based on the Early Release Compact Source Catalog (ERCSC) and Swift BAT 105-Month Hard X-ray Survey. The radio Planck spectra vs. X-ray Swift/XRT+BAT spectra of the active galactic nuclei (AGN) sample were fitted with the simple and broken power law (for the X-ray spectra taking into account also the Galactic neutral absorption) to test the dependencies between the photon indices of synchrotron emission (in radio range) and synchrotron self-Compton (SSC) or inverse-Compton emission (in X-rays). We

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ZACHARIAS, MICHAEL, and REINHARD SCHLICKEISER. "TIME-DEPENDENT SSC COOLING EFFECTS ON BLAZAR EMISSION." International Journal of Modern Physics: Conference Series 28 (January 2014): 1460181. http://dx.doi.org/10.1142/s2010194514601811.

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Blazars are among the most violent sources in the cosmos exhibiting flaring states with remarkably different variability time scales. Especially rapid flares with flux doubling time scales of the order of minutes have been puzzling for quite some time. Many modeling attempts use the well known linear and steady-state scenario for the cooling and emission processes in the jet, albeit the obvious strongly time-dependent nature of flares. Due to the feedback of the self-produced synchrotron radiation with additional scattering by the relativistic electrons, the synchrotron-self Compton (SSC) effe

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Feng, Yaru, Shaoming Hu, Ruixin Zhou та Songbo Gao. "Explaining the Multiwavelength Emission of γ-ray Bright Flat-Spectrum Radio Quasar 3C 454.3 in Different Activity States". Universe 8, № 11 (2022): 585. http://dx.doi.org/10.3390/universe8110585.

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The origin of gamma-ray flares of blazars is still an open issue in jet physics. In this work, we reproduce the multiwavelength spectral energy distribution (SED) of flat-spectrum radio quasars 3C 454.3 under a one-zone leptonic scenario, investigate the variation of the physical parameters in different activity states, and analyze the possible origin of its γ-ray outburst. Based on the analysis of multiwavelength quasi-simultaneous observations of 3C 454.3 during MJD 55,400–56,000, we consider that the radiation includes synchrotron (Syn), synchrotron self-Compton (SSC), and external Compton

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9

Fraija, N., M. G. Dainotti, Sahil Ugale, Debarpita Jyoti, and Donald C. Warren. "Synchrotron Self-Compton Afterglow Closure Relations and Fermi-LAT-detected Gamma-Ray Bursts." Astrophysical Journal 934, no. 2 (2022): 188. http://dx.doi.org/10.3847/1538-4357/ac7a9c.

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Abstract The Fermi Large Area Telescope (Fermi-LAT) Collaboration reported the Second Gamma-ray Burst Catalog (2FLGC), which comprises a subset of 29 bursts with photon energies above 10 GeV. Although the standard synchrotron forward-shock model has successfully explained the gamma-ray burst (GRB) afterglow observations, energetic photons higher than 10 GeV from these transient events can hardly be described in this scenario. We present the closure relations (CRs) of the synchrotron self-Compton (SSC) afterglow model in the adiabatic and radiative scenario, and when the central engine injects

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10

Joshi, Jagdish C., and Soebur Razzaque. "Modelling synchrotron and synchrotron self-Compton emission of gamma-ray burst afterglows from radio to very-high energies." Monthly Notices of the Royal Astronomical Society 505, no. 2 (2021): 1718–29. http://dx.doi.org/10.1093/mnras/stab1329.

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ABSTRACT Synchrotron radiation from a decelerating blastwave is a widely accepted model of radio to X-ray afterglow emission from gamma-ray bursts (GRBs). GeV gamma-ray emission detected by the Fermi Large Area Telescope (LAT) and the duration of which extends beyond the prompt gamma-ray emission phase is also compatible with broad features of afterglow emission. We revisit the synchrotron self-Compton (SSC) emission model from a decelerating blastwave to fit multiwavelength data from three bright GRBs, namely GRB 190114C, GRB 130427A, and GRB 090510. We constrain the afterglow model parameter

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11

Wang, Xiang-Gao, Yuan-Zhuo Chen, Xiao-Li Huang, et al. "GRB 110213A: A Study of Afterglow Electromagnetic Cascade Radiation." Astrophysical Journal 939, no. 1 (2022): 39. http://dx.doi.org/10.3847/1538-4357/ac937c.

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Abstract We obtained well-sampled optical photometry of GRB 110213A, including Swift/UVOT and XRT. Combining our data from those of other ground-based telescopes, we present 15 optical multicolor light curves showing similar shapes with two peaks. In contrast, in the X-ray band, only a single peak is observed between the two optical peaks. Temporal and spectral analysis of GRB 110213A shows that the X-rays differ from the optical for Phases I–III (before the second peak of the optical band at ∼5.6 ks). Moreover, they have the same spectral behavior at late times (Phases IV–VI). These data indi

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Zhang, H., I. M. Christie, M. Petropoulou, J. M. Rueda-Becerril, and D. Giannios. "Inverse Compton signatures of gamma-ray burst afterglows." Monthly Notices of the Royal Astronomical Society 496, no. 1 (2020): 974–86. http://dx.doi.org/10.1093/mnras/staa1583.

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ABSTRACT The afterglow emission from gamma-ray bursts (GRBs) is believed to originate from a relativistic blast wave driven into the circumburst medium. Although the afterglow emission from radio up to X-ray frequencies is thought to originate from synchrotron radiation emitted by relativistic, non-thermal electrons accelerated by the blast wave, the origin of the emission at high energies (HE; ≳GeV) remains uncertain. The recent detection of sub-TeV emission from GRB 190114C by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) raises further debate on what powers the very high

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13

Nava, Lara. "Gamma-ray Bursts at the Highest Energies." Universe 7, no. 12 (2021): 503. http://dx.doi.org/10.3390/universe7120503.

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Emission from Gamma-ray bursts is thought to be powered mainly by synchrotron radiation from energetic electrons. The same electrons might scatter these synchrotron seed photons to higher (>10 GeV) energies, building a distinct spectral component (synchrotron self-Compton, SSC). This process is expected to take place, but its relevance (e.g., the ratio between the SSC and synchrotron emitted power) is difficult to predict on the basis of current knowledge of physical conditions at GRB emission sites. Very high-energy radiation in GRBs can be produced also by other mechanisms, such as synchr

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Fraija, N., A. Marinelli, U. Luviano-Valenzuela, A. Galván-Gaméz, and C. Peterson-Bórquez. "Lepton-hadronic processes and high-energy neutrinos in NGC 1275." Proceedings of the International Astronomical Union 10, S313 (2014): 175–76. http://dx.doi.org/10.1017/s1743921315002148.

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AbstractThe nearby active galaxy NGC 1275, has been widely detected from radio to gamma rays. Its spectral energy distribution (SED) shows a double-peak feature, which is well explained by synchrotron self-Compton (SSC) model. However, recent TeV detections might suggest that very-high-energy γ-rays (E⩾100 GeV) may not have a leptonic origin. We test a lepto-hadronic model to describe the whole SED through SSC emission and neutral pion decay resulting from pγ interactions. Also, we estimate the neutrino events expected in a km3 Cherenkov telescope.

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Chen, Yongyun, Qiusheng Gu, Junhui Fan, et al. "General Physical Properties of Gamma-Ray-emitting Radio Galaxies." Astrophysical Journal Supplement Series 265, no. 2 (2023): 60. http://dx.doi.org/10.3847/1538-4365/acc57f.

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Abstract We study the radio galaxies with known redshifts detected by the Fermi satellite after 10 yr of data (4FGL-DR2). We use a one-zone leptonic model to fit the quasi-simultaneous multiwavelength data of these radio galaxies and study the distributions of the derived physical parameters as a function of black hole mass and accretion disk luminosity. The main results are as follows. (1) We find that the jet kinetic power of most radio galaxies can be explained by the hybrid jet model based on ADAFs surrounding Kerr black holes. (2) After excluding the redshift, there is a significant corre

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Mantovani, F., C. Valerio, W. Junor, and I. M. McHardy. "Search for Short Timescale Structural Variation of 3C 273 at 22 GHz and 43 GHz." International Astronomical Union Colloquium 164 (1998): 65–66. http://dx.doi.org/10.1017/s0252921100044559.

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AbstractThe results of VLBI observations of the quasar 3C 273, obtained during a multi-frequency campaign in late 1992 in the radio, millimeter, and X-ray bands are presented. The aim of the campaign was to test the application of the SSC (Synchrotron Self-Compton) model to 3C 273. Independent estimates are obtained through the assumption of the energy equipartition between particles and magnetic field.

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17

RICHTER, STEPHAN, and FELIX SPANIER. "A SPATIALLY RESOLVED SSC SHOCK-IN-JET MODEL." International Journal of Modern Physics: Conference Series 08 (January 2012): 392–95. http://dx.doi.org/10.1142/s2010194512004977.

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In this paper a spatially resolved, fully self-consistent SSC model is presented. The observable spectral energy distribution (SED) evolves entirely from a low energetic delta distribution of injected electrons by means of the implemented microphysics of the jet. These are in particular the properties of the shock and the ambient plasma, which can be varied along the jet axis. Hence a large variety of scenarios can be computed, e.g. the acceleration of particles via multiple shocks. Two acceleration processes, shock acceleration and stochastic acceleration, are taken into account. From the res

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18

Aguilar-Ruiz, E., N. Fraija, A. Galván-Gámez, and E. Benítez. "A two-zone model as origin of hard TeV spectrum in extreme BL lacs." Monthly Notices of the Royal Astronomical Society 512, no. 2 (2022): 1557–66. http://dx.doi.org/10.1093/mnras/stac591.

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ABSTRACT The emission of the so-called extreme BL Lacs poses challenges to the particle acceleration models. The hardness of their spectrum, ≲ 2, in the high-energy band demands unusual parameters using the standard one-zone synchrotron self-Compton (SSC) model with a deficient magnetized plasma. Some authors use either two-zone or hadronic/lepto-hadronic models to relax these atypical values. In this work, we present a lepto-hadronic two-zone model to explain the multi-wavelength observations of the six best-known extreme BL Lacs. The very-high-energy gamma-ray observations are described by t

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Peirson, Abel L., Ioannis Liodakis, and Roger W. Romani. "Testing High-energy Emission Models for Blazars with X-Ray Polarimetry." Astrophysical Journal 931, no. 1 (2022): 59. http://dx.doi.org/10.3847/1538-4357/ac6a54.

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Abstract Both leptonic and hadronic emission processes may contribute to blazar jet emission; which dominates in blazars’ high-energy emission component remains an open question. Some intermediate synchrotron peaked blazars transition from their low- to high-energy emission components in the X-ray band making them excellent laboratories to probe both components simultaneously, and good targets for the newly launched Imaging X-ray Polarimetry Explorer (IXPE). We characterize the spectral energy distributions for three such blazars, CGRaBS J0211+1051, TXS 0506+056, and S5 0716+714, predicting th

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WEIDINGER, MATTHIAS, and FELIX SPANIER. "MODELING THE EMISSION FROM BLAZAR JETS: THE CASE OF PKS 2155-304." International Journal of Modern Physics D 19, no. 06 (2010): 887–92. http://dx.doi.org/10.1142/s0218271810017159.

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A time-dependent synchrotron self-Compton model (SSC) which is able to motivate the used electron spectra of many SSC models as a balance of acceleration and radiative losses is introduced. Using stochastic acceleration as well as Fermi-I processes even electron spectra with a rising part can be explained, which are mandatory to fit the low state spectral energy distribution (SED) of PKS 2155-304 as constrained from Fermi LAT observations. Due to the time resolution the outburst of PKS 2155-304 observed by H.E.S.S. in 2006 can be modelled self-consistently as fluctuations along the jet axis wi

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Zeng, Yuhang, Dahai Yan, Wen Hu, and Jiancheng Wang. "A spectral hardening in the Fermi-LAT Data of 1ES 0502+675." Monthly Notices of the Royal Astronomical Society 511, no. 1 (2022): 938–42. http://dx.doi.org/10.1093/mnras/stac061.

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ABSTRACT The γ-ray spectral feature of the blazar 1ES 0502+675 is investigated by using Fermi Large Area Telescope Pass 8 data (between 100 MeV and 300 GeV) covering from 2008 August to 2021 April. A significant (∼4σ) hardening at ∼1 GeV is found in the γ-ray spectrum during a moderately flaring state (MJD 55050–55350). The photon index below and above the break energy is Γ1 = 2.36 ± 0.31 and Γ2 = 1.33 ± 0.11, respectively. In the rest of the observations, the γ-ray spectrum can be described by a power-law form with the photon index of ≈1.6. In the frame of a one-zone synchrotron self-Compton

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Gao, Hao-Xuan, Jin-Jun Geng, and Yong-Feng Huang. "Evolution patterns of the peak energy in the GRB prompt emission." Astronomy & Astrophysics 656 (December 2021): A134. http://dx.doi.org/10.1051/0004-6361/202141647.

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Context. The peak energy (Ep) exhibited during the prompt emission phase of gamma-ray bursts (GRBs) shows two different evolution patterns, namely hard-to-soft and intensity-tracking, of which the physical origin remains unknown. In addition to low-energy indices of GRB prompt spectra, the evolution patterns of Ep may be another crucial indicator with which to discriminate radiation mechanisms (e.g., synchrotron or photosphere) for GRBs. Aims. We explore the parameter space to find conditions that could generate different evolution patterns in the peak energy in the framework of synchrotron ra

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LENAIN, J. P., C. BOISSON, and H. SOL. "SSC SCENARIO FOR TEV EMISSION FROM NON-BLAZAR AGNs." International Journal of Modern Physics D 17, no. 09 (2008): 1577–84. http://dx.doi.org/10.1142/s0218271808013170.

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M 87 is the first extragalactic source detected in the TeV γ-ray domain that is not a blazar, its large scale jet not being aligned to the line of sight. We present here a multi-blob synchrotron self-Compton model accounting explicitly for large viewing angles and moderate Lorentz factors as inferred from magnetohydrodynamic simulations of jet formation, motivated by the detection of M 87 at very high energies (VHE; E > 100 GeV ). Predictions are presented for the very high-energy emission of active galactic nuclei with extended optical or X-ray jet, which could be misaligned blazars but st

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Arsioli, B., та Y.-L. Chang. "Theγ-ray emitting region in low synchrotron peak blazars". Astronomy & Astrophysics 616 (серпень 2018): A63. http://dx.doi.org/10.1051/0004-6361/201833005.

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Aims.From the early days inγ-ray astronomy, locating the origin of GeV emission within the core of an active galactic nucleus (AGN) persisted as an open question; the problem is to discern between near- and far-site scenarios with respect to the distance from the super massive central engine. We investigate this question under the light of a complete sample of low synchrotron peak (LSP) blazars which is fully characterized along many decades in the electromagnetic spectrum, from radio up to tens of GeV. We consider the high-energy emission from bright radio blazars and test for synchrotron sel

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Baghmanyan, V., та N. Sahakyan. "X-ray and γ-ray emissions from NLSy1 galaxies". International Journal of Modern Physics D 27, № 10 (2018): 1844001. http://dx.doi.org/10.1142/s0218271818440017.

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The recent observations by Fermi large area telescope (Fermi-LAT) showed that in addition to the radio galaxies and blazars, Narrow-Line Seyfert 1 (NLSy1) galaxies are also [Formula: see text]-rays emitters. NLSy1 are AGNs with optical spectral properties similar to those of Seyfert 1 galaxies, except for having narrow Balmer lines and strong optical lines. They also exhibit strong X-ray variability, steep X-ray spectra and relatively high luminosity. The multiwavelength emission properties of 1H 0323+342, SBS 0846+513 and PMN J0948+0022 are discussed, using the [Formula: see text]-ray data fr

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Harding, Alice K., Christo Venter, and Constantinos Kalapotharakos. "Very-high-energy Emission from Pulsars." Astrophysical Journal 923, no. 2 (2021): 194. http://dx.doi.org/10.3847/1538-4357/ac3084.

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Abstract Air-Cherenkov telescopes have detected pulsations at energies above 50 GeV from a growing number of Fermi pulsars. These include the Crab, Vela, PSR B1706−44, and Geminga, with the first two having pulsed detections above 1 TeV. In some cases, there appears to be very-high-energy (VHE) emission that is an extension of the Fermi spectra to high energies, while in other cases, additional higher-energy spectral components that require a separate emission mechanism may be present. We present results of broadband spectral modeling using global magnetospheric fields and multiple emission me

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Romanova, M. M., and R. V. E. Lovelace. "High-Energy Gamma and Radio Variability of Blazars in the Model of Non-Stationary Jets." Symposium - International Astronomical Union 175 (1996): 419–20. http://dx.doi.org/10.1017/s0074180900081304.

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A model has been developed for impulsive VLBI jet formation and gamma ray outbursts of Blazars. Propagation of newly expelled matter in the old channel of a jet is calculated supposing that the main driving force is the electromagnetic field. The new outflowing matter overtakes the old matter and forms double, fast or slow magnetosonic shock fronts. In the region of the fronts, the number of particles and their energy increase continuously with propagation time from the central object (Romanova and Lovelace, 1995). Accelerated electrons and positrons in the front interact with a diffuse field

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Patel, S. R., and V. R. Chitnis. "Leptonic modelling of Ton 599 in flare and quiescent states." Monthly Notices of the Royal Astronomical Society 492, no. 1 (2019): 72–78. http://dx.doi.org/10.1093/mnras/stz3490.

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ABSTRACT The flat-spectrum radio quasar Ton 599 attained its highest ever γ-ray flux state during the first week of 2017 November. Observations of the source by the Swift satellite during this period made it possible to generate a simultaneous high flux state broad-band spectral energy distribution (SED). The high flux state activity of Ton 599 is modelled in this work for the first time. We modelled one high flux state and one quiescent state of the source in order to characterize the evolution of SEDs covering the entire dynamic range of γ-ray flux observed by Fermi-LAT. An attempt was made

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Sanchez, David, Berrie Giebels, and Pascal Fortin. "The challenging SED of AP Librae." Proceedings of the International Astronomical Union 7, S284 (2011): 411–13. http://dx.doi.org/10.1017/s1743921312009532.

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AbstractMatching the broad-band emission of active galaxies with the predictions of theoretical models can be used to derive constraints on the properties of the emitting region and to probe the physical processes involved. AP Librae is the third low frequency peaked BL Lac (LBL) detected at very high energy (VHE, E>100GeV) by an Atmospheric Cherenkov Telescope; most VHE BL Lacs (34 out of 39) belong to the high-frequency and intermediate-frequency BL Lac classes (HBL and IBL). LBL objects tend to have a higher luminosity with lower peak frequencies than HBLs or IBLs. The characterization o

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Yuan, Y. H., Y. G. Zheng, J. H. Fan, J. M. Hao, and H. B. Xiao. "The Spectrum Variabilities of FSRQ 3C 273." Publications of the Astronomical Society of the Pacific 134, no. 1034 (2022): 044102. http://dx.doi.org/10.1088/1538-3873/ac5b88.

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Abstract 3C 273 is a well-studied FSRQ. In order to analyze its spectrum variabilities, we make spectroscopic observations of 3C 273 using the 2.16 m telescope at Xinglong Observatory of the National Astronomical Observatories. Based on these observations and some other spectra from the literature, we study the spectrum variabilities and the physical origin of the optical spectrum. The main results are as follows: (1) The continuum spectrum (S c ) shows obvious variabilities and displays quasi-periodic properties, P = 3.39 ± 1.13 yr, consistent with the result calculated from photometric obser

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González, Josefa Becerra. "VHE BL Lacs through the MAGIC glasses." Proceedings of the International Astronomical Union 10, S313 (2014): 64–69. http://dx.doi.org/10.1017/s174392131500188x.

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AbstractIn this contribution an overview of the latest results on the study of BL Lac objects with the MAGIC telescopes at the very high energy (VHE, E>100 GeV) gamma-rays is presented. Three new VHE sources were detected during 2014, two BL Lac objects and the gravitational lensed blazar S3 0218+357. MAGIC detected very fast intra-night variability from IC 310. This detection points to smaller emitting regions than the event horizon, this is hard to be explained in the framework of the current theoretical models. The long term multi wavelength (MWL) study of the BL Lac PKS 1424+240 shows c

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Longhua, Qin, Wang Jiancheng, Gao Quangui, et al. "Studies of extragalactic background light with TeV BL Lacertae objects." Monthly Notices of the Royal Astronomical Society 499, no. 2 (2020): 2662–71. http://dx.doi.org/10.1093/mnras/staa2634.

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ABSTRACT Very high energy (VHE; E ≥ 100 GeV) gamma-rays from cosmological distances are attenuated by the extragalactic background light (EBL) in the infrared to ultraviolet bands. By contrasting measured versus intrinsic emission,we can derive the EBL photon density. However, we do not know the intrinsic spectra and the EBL separately, only their combined effect. Here we first present a flexible model-dependent optical depth method to study the EBL by fitting the emission spectra of TeV BL Lacertae objects (BL Lacs) via a one-zone leptonic synchrotron self-Compton model (SSC). We have little

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Ren, Jia, Yun Wang, Lu-Lu Zhang, and Zi-Gao Dai. "The Possibility of Modeling the Very High Energy Afterglow of GRB 221009A in a Wind Environment." Astrophysical Journal 947, no. 2 (2023): 53. http://dx.doi.org/10.3847/1538-4357/acc57d.

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Abstract In this paper, we model the dynamics and radiation physics of the rarity event GRB 221009A afterglow in detail. By introducing a top-hat jet that propagates in an environment dominated by stellar winds, we explain the publicly available observations of afterglow associated with GRB 221009A over the first week. It is predicted that GRB 221009A emits a luminous very high energy afterglow based on the synchrotron self-Compton (SSC) process in our model. We show the broadband spectral energy distribution (SED) analysis results of GRB 221009A and find that the SSC radiation component of GR

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Cerruti, M., W. Benbow, X. Chen, J. P. Dumm, L. F. Fortson та K. Shahinyan. "Luminous and high-frequency peaked blazars: the origin of the γ-ray emission from PKS 1424+240". Astronomy & Astrophysics 606 (жовтень 2017): A68. http://dx.doi.org/10.1051/0004-6361/201730799.

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Context. The current generation of ground-based Cherenkov telescopes, together with the LAT instrument on-board the Fermi satellite, have greatly increased our knowledge of γ-ray blazars. Among them, the high-frequency-peaked BL Lacertae object (HBL) PKS 1424+240 (z ≃ 0.6) is the farthest persistent emitter of very-high-energy (VHE; E ≥ 100 GeV) γ-ray photons. Current emission models can satisfactorily reproduce typical blazar emission assuming that the dominant emission process is synchrotron-self-Compton (SSC) in HBLs; and external-inverse-Compton (EIC) in low-frequency-peaked BL Lacertae ob

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Patel, S. R., A. Shukla, V. R. Chitnis, et al. "Broadband study of blazar 1ES 1959+650 during flaring state in 2016." Astronomy & Astrophysics 611 (March 2018): A44. http://dx.doi.org/10.1051/0004-6361/201731987.

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Aims. The nearby TeV blazar 1ES 1959+650 (z = 0.047) was reported to be in flaring state during June–July 2016 by Fermi-LAT, FACT, MAGIC and VERITAS collaborations. We studied the spectral energy distributions (SEDs) in different states of the flare during MJD 57530–57589 using simultaneous multiwaveband data with the aim of understanding the possible broadband emission scenario during the flare. Methods. The UV-optical and X-ray data from UVOT and XRT respectively on board Swift and high energy γ-ray data from Fermi-LAT were used to generate multiwaveband lightcurves as well as to obtain high

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ZHANG, JIN, SHUANG-NAN ZHANG, and EN-WEI LIANG. "BLAZAR ANTI-SEQUENCE OF SPECTRAL VARIABILITY FOR INDIVIDUAL TeV BLAZARS." International Journal of Modern Physics: Conference Series 23 (January 2013): 54–63. http://dx.doi.org/10.1142/s2010194513011070.

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We compile from literature the broadband SEDs of twelve TeV blazars observed simultaneously or quasi-simultaneously with Fermi/LAT and other instruments. Two SEDs are available for each of the objects and the state is identified as a low or high state according to its flux density at GeV/TeV band. The observed SEDs of BL Lac objects (BL Lacs) are fitted well with the synchrotron + synchrotron-self-Compton (syn+SSC) model, whereas the SEDs of the two flat spectrum radio quasars (FSRQs) need to include the contributions of external Compton scattering. In this scenario, it is found that the Doppl

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Huang, Zhi-Qiu, John G. Kirk, Gwenael Giacinti, and Brian Reville. "The Implications of TeV-detected GRB Afterglows for Acceleration at Relativistic Shocks." Astrophysical Journal 925, no. 2 (2022): 182. http://dx.doi.org/10.3847/1538-4357/ac3f38.

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Abstract Motivated by the detection of very-high-energy (VHE) gamma rays deep in the afterglow emission of a gamma-ray burst (GRB), we revisit predictions of the maximum energy to which electrons can be accelerated at a relativistic blast wave. Acceleration at the weakly magnetized forward shock of a blast wave can be limited by either the rapid damping of turbulence generated behind the shock, the effect of a large-scale ambient magnetic field, or radiation losses. Within the confines of a standard, single-zone, synchrotron self-Compton (SSC) model, we show that observations of GRB 190829A ru

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Shah, Zahir, V. Jithesh, S. Sahayanathan, and Naseer Iqbal. "Unveiling the broad-band spectral and temporal properties of PKS 0903-57 during its brightest flare." Monthly Notices of the Royal Astronomical Society 504, no. 1 (2021): 416–27. http://dx.doi.org/10.1093/mnras/stab834.

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ABSTRACT We carried a detailed spectral and temporal study of blazar PKS 0903-57 using the Fermi-LAT and Swift-XRT/UVOT observations, during its brightest flaring period MJD 58931–58970. During this period, the maximum daily averaged γ-ray flux ($\rm F_{0.1-500\, GeV}$) of $\rm 9.42\times 10^{-6}\, ph\, cm^{-2}\, s^{-1}$ is observed on MJD 58951.5, the highest γ-ray flux detected from PKS 0903-57 till now. Several high-energy (HE) photons ($\gt 10$ GeV) consistent with the source location at high probability (&gt;99 per cent) are detected, and the γ-ray light curve in the active state show

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JOSHI, M., and M. BÖTTCHER. "MODELING THE MULTIWAVELENGTH SPECTRA AND VARIABILITY OF 3C 66A IN 2003–2004." International Journal of Modern Physics A 22, no. 19 (2007): 3147–54. http://dx.doi.org/10.1142/s0217751x07036907.

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The BL Lac object 3C 66A was the target of an intensive multiwavelength monitoring campaign organized in 2003–2004. During the campaign, its spectral energy distribution (SED) was measured and flux measurements from radio to X-ray frequencies as well as upper limits in the very high energy (VHE) γ-ray regime were obtained. Here, we reproduce the SED and optical spectral variability pattern observed during our multiwavelength campaign using a time-dependent leptonic jet model. Our model could successfully simulate the observed SED and optical light curves and predict an intrinsic cutoff value f

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Meintjes, Pieter J., Pheneas Nkundabakura, Brian Van Soelen, and Alida Odendaal. "Modelling the Multifrequency SED of AGN Candidates among the Unidentied EGRET and Fermi Gamma-Ray Sources." Acta Polytechnica CTU Proceedings 1, no. 1 (2014): 163–69. http://dx.doi.org/10.14311/app.2014.01.0163.

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Of the 271 sources in the 3rd EGRET catalogue, 131 were reported as unidentied, i.e. not associated with any particular class of point source in the sky. Since the largest fraction of the EGRET sources were extragalactic, a sample of 13 extragalactic unidentied sources have been selected for multi-wavelength follow-up studies. Five of the selected EGRET sources coincide with gamma-ray flux enhancements seen in the Fermi-LAT data after one year of operation. In this article, we report the multi-wavelength properties of, among others, the 5 sources detected by Fermi-LAT from our sample of high g

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Acciari, V. A., S. Ansoldi, L. A. Antonelli, et al. "Broadband characterisation of the very intense TeV flares of the blazar 1ES 1959+650 in 2016." Astronomy & Astrophysics 638 (June 2020): A14. http://dx.doi.org/10.1051/0004-6361/201935450.

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1ES 1959+650 is a bright TeV high-frequency-peaked BL Lac object exhibiting interesting features like “orphan” TeV flares and broad emission in the high-energy regime that are difficult to interpret using conventional one-zone Synchrotron Self-Compton (SSC) scenarios. We report the results from the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) observations in 2016 along with the multi-wavelength data from the Fermi Large Area Telescope (LAT) and Swift instruments. MAGIC observed 1ES 1959+650 with different emission levels in the very-high-energy (VHE, E > 100 GeV) γ-ray band during 2016

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Marchesini, E. J., A. Paggi, F. Massaro та ін. "The γ-ray sky seen at X-ray energies". Astronomy & Astrophysics 631 (листопад 2019): A150. http://dx.doi.org/10.1051/0004-6361/201936285.

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Context. BL Lac objects are an extreme type of active galactic nuclei (AGNs) that belong to the largest population of γ-ray sources: blazars. This class of AGNs shows a double-bumped spectral energy distribution that is commonly described in terms of a synchrotron self-Compton (SSC) emission process, whereas the low-energy component that dominates their emission between the infrared and the X-ray band is tightly connected to the high-energy component that peaks in the γ-rays. Two strong connections that link radio and mid-infrared emission of blazars to the emission in the γ-ray band are well

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de Menezes, Raniere, Rodrigo Nemmen, Justin D. Finke, Ivan Almeida, and Bindu Rani. "Gamma-ray observations of low-luminosity active galactic nuclei." Monthly Notices of the Royal Astronomical Society 492, no. 3 (2020): 4120–30. http://dx.doi.org/10.1093/mnras/staa083.

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ABSTRACT The majority of the activity around nearby (z ≈ 0) supermassive black holes is found in low-luminosity active galactic nuclei (LLAGN), the most of them being classified as low-ionization nuclear emission regions. Although these sources are well studied from radio up to X-rays, they are poorly understood in γ-rays. In this work, we take advantage of the all sky-surveying capabilities of the Large Area Telescope on board Fermi Gamma-ray Space Telescope to study the whole Palomar sample of LLAGN in γ-rays. Precisely, the four radio-brightest LLAGN in the sample are identified as signific

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Huang, Yan. "Time-dependent Numerical Model for Studying the Very-high-energy Emissions of Distant Gamma-Ray Burst GRB 201216C." Astrophysical Journal 931, no. 2 (2022): 150. http://dx.doi.org/10.3847/1538-4357/ac6d52.

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Abstract Recently, the MAGIC Collaboration reported a ∼5σ statistical significance of the very-high-energy (VHE) emission from a distant gamma-ray burst (GRB), GRB 201216C. Such distant GRB may be effectively absorbed by the extragalactic background light (EBL). The origin of the VHE emission from such distant objects is still unknown. Here, we propose a numerical model for studying the afterglow emission of this distant GRB. The model solves the continuity equation governing the temporal evolution of electron distribution, and the broadband observed data can be explained by the synchrotron pl

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Huang, Yan. "Time-dependent Numerical Model for Studying the Very-high-energy Emissions of Distant Gamma-Ray Burst GRB 201216C." Astrophysical Journal 931, no. 2 (2022): 150. http://dx.doi.org/10.3847/1538-4357/ac6d52.

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Abstract Recently, the MAGIC Collaboration reported a ∼5σ statistical significance of the very-high-energy (VHE) emission from a distant gamma-ray burst (GRB), GRB 201216C. Such distant GRB may be effectively absorbed by the extragalactic background light (EBL). The origin of the VHE emission from such distant objects is still unknown. Here, we propose a numerical model for studying the afterglow emission of this distant GRB. The model solves the continuity equation governing the temporal evolution of electron distribution, and the broadband observed data can be explained by the synchrotron pl

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Abdalla, H., A. Abramowski, F. Aharonian та ін. "The γ-ray spectrum of the core of Centaurus A as observed with H.E.S.S. and Fermi-LAT". Astronomy & Astrophysics 619 (листопад 2018): A71. http://dx.doi.org/10.1051/0004-6361/201832640.

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Centaurus A (Cen A) is the nearest radio galaxy discovered as a very-high-energy (VHE; 100 GeV–100 TeV) γ-ray source by the High Energy Stereoscopic System (H.E.S.S.). It is a faint VHE γ-ray emitter, though its VHE flux exceeds both the extrapolation from early Fermi-LAT observations as well as expectations from a (misaligned) single-zone synchrotron-self Compton (SSC) description. The latter satisfactorily reproduces the emission from Cen A at lower energies up to a few GeV. New observations with H.E.S.S., comparable in exposure time to those previously reported, were performed and eight yea

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He, Xin-Bo, Pak-Hin Thomas Tam, Guang-Bo Long, Partha Sarathi Pal, Yong Zhang, and Li-Jun Zhang. "Searching for an additional high-energy component in Fermi-LAT GRB afterglows." Astronomy & Astrophysics 657 (January 2022): A111. http://dx.doi.org/10.1051/0004-6361/202040039.

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Context. The very high-energy (VHE; ≥100 GeV) component from at least two gamma-ray bursts (GRBs), that is, GRB 180720B and GRB 190114C, has been detected in the afterglow phase. It is widely discussed that the GeV to TeV emission originated from a synchrotron self-Compton (SSC) process. The VHE component may cause an upturn at the high-energy spectral ends in the Fermi-Large Area Telescope (Fermi-LAT) observing band. Aims. We aim to find out whether an additional high-energy component commonly exists in the afterglows of Fermi-LAT GRBs. This study will help us to better understand how common

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Ahnen, M. L., S. Ansoldi, L. A. Antonelli, et al. "Extreme HBL behavior of Markarian 501 during 2012." Astronomy & Astrophysics 620 (December 2018): A181. http://dx.doi.org/10.1051/0004-6361/201833704.

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Aims. We aim to characterize the multiwavelength emission from Markarian 501 (Mrk 501), quantify the energy-dependent variability, study the potential multiband correlations, and describe the temporal evolution of the broadband emission within leptonic theoretical scenarios. Methods. We organized a multiwavelength campaign to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-

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Acciari, V. A., S. Ansoldi, L. A. Antonelli, et al. "Study of the variable broadband emission of Markarian 501 during the most extreme Swift X-ray activity." Astronomy & Astrophysics 637 (May 2020): A86. http://dx.doi.org/10.1051/0004-6361/201834603.

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Context. Markarian 501 (Mrk 501) is a very high-energy (VHE) gamma-ray blazar located at z = 0.034, which is regularly monitored by a wide range of multi-wavelength instruments, from radio to VHE gamma rays. During a period of almost two weeks in July 2014, the highest X-ray activity of Mrk 501 was observed in ∼14 years of operation of the Neil Gehrels Swift Gamma-ray Burst Observatory. Aims. We characterize the broadband variability of Mrk 501 from radio to VHE gamma rays during the most extreme X-ray activity measured in the last 14 years, and evaluate whether it can be interpreted within th

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Uzdensky, D. A. "Relativistic turbulence with strong synchrotron and synchrotron self-Compton cooling." Monthly Notices of the Royal Astronomical Society 477, no. 3 (2018): 2849–57. http://dx.doi.org/10.1093/mnras/sty721.

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