Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)最新文献

{"title":"Relativistic Jet Of Markarian 421: Observational Evidences Of Particle Acceleration Mechanisms","authors":"B. Kapanadze, S. Vercellone, P. Romano","doi":"10.22323/1.354.0015","DOIUrl":"https://doi.org/10.22323/1.354.0015","url":null,"abstract":"Markarian 421 is one the most extreme blazars characterized by a complex, unpredictable timing/spectral variability, strong X-ray outbursts in some epochs, very broad, nonthermal spectral energy distribution (SED) extending over 16–18 orders of frequency and showing a typical two\"hump\" structure. The lower-energy component, ranging from the radio to X-rays, is widely accepted to be synchrotron radiation emitted by ultra-relativistic electrons, while the origin of the higher-energy emission (the MeV–TeV range) still remains controversial (synchrotron selfCompton, external Compton, hadronic etc.). All these radiative mechanisms need the presence of highly-relativistic particles in the jet, to be initially accelerated via the Blandford-Znajek mechanism and magneto-hydrodynamic processes in the vicinity of the central super-massive black hole. However, particles lose the energy, required for the emission of the KeV photons, very quickly and the source can maintain its flaring state on the daily-weekly timescales if some additional acceleration mechanisms are continuously at work in the jet. According to the different studies and simulations, particles can gain a tremendous energy due to the propagation of relativistic shocks through the jet: by means of first-order Fermi mechanism at the shock front, or by an efficient stochastic (second-order Fermi) acceleration close to the shock, in the turbulent jet medium. Our intensive X-ray spectral study of Mrk 421 has revealed the dominance of these processes in different epochs: in some periods, the spectral curvature and the photon index showed a positive cross-correlation (expected in the framework of energy-dependent acceleration probability scenario: a particular case of first-order Fermi mechanism), and the source generally demonstrated the a spectral behaviour compatible with the stochastic (second-order Fermi) acceleration (low spectral curvature; anti-correlation between the spectral curvature and the position of the synchrotron SED peak). For our target, relativistic magnetic reconnection seems to be more important during the radio-optical flares. A jet-star interaction process could be the case during 2016 April–August when the source showed a soft gamma-ray excess.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"16 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120901204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Are jets in GRS 1758-258 precessing?","authors":"P. Luque-Escamilla, J. Martí","doi":"10.22323/1.354.0096","DOIUrl":"https://doi.org/10.22323/1.354.0096","url":null,"abstract":"The large-scale morphology of the radio jets in microquasar GRS 1758-258 has been changing in the last decades. Available radio maps show hints of apparent precession. Here, we fit data with a simple kinematical model and perform an analysis of the possible origins and implications of precession in this system. From our study, that includes an additional observing epoch, we are able to confirm the previous detection of changes in the radio jets of GRS 1758-258 far from the core. However, we tentatively suggest that these changes are more probably due to instabilities instead of jet precession.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132562148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extreme Regimes Of Emission In Relativistic Outflows","authors":"E. Derishev","doi":"10.22323/1.354.0013","DOIUrl":"https://doi.org/10.22323/1.354.0013","url":null,"abstract":"All broad-band blazar spectra display two broad and widely separated maxima. We analyse existing models, which attempt to explain non-thermal emission of blazars addressing the origin of these maxima. For various reasons that we discuss in this paper, none of these models can claim success with the entire blazar population and rather take responsibility for either GeV or TeV blazars. In addition, we analyse particle acceleration and radiation processes within joint framework, discuss extreme regimes of radiation and physical limits to the parameters of blazars’ emitting zones, and show that in many cases requirements of blazar emission models cannot fit into these fundamental limits. We also consider recent observation of sub-TeV emission from Gamma-Ray Burst afterglow in the case of GRB 190114C. Derived parameters for the emitting zone of this burst indicate that absorption of sub-TeV radiation inside the emitting zone is an important effect and are in agreement with predictions of the pair-balance model of relativistic shocks. Based on this evidence, we argue that that relativistic flows (not only in GRBs, but in a general situation as well) are very efficient in accelerating electrons and that the energy of accelerated electrons is limited not by the acceleration process itself, but rather by the back reaction from the high-energy radiation produced in the flow.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130384365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stability analysis of magnetized astrophysical relativistic jets without current sheets","authors":"N. Vlahakis, Sinnis Charalampos","doi":"10.22323/1.354.0078","DOIUrl":"https://doi.org/10.22323/1.354.0078","url":null,"abstract":"Astrophysical jets are observed as stable structures, extending in lengths several times their radii. The role of various instabilities and how they affect the observed jet properties has not been fully understood. Using the ideal relativistic MHD equations to describe jet dynamics we aim to study the stability properties through linear analysis. In this work we probe stability properties of jets without current sheets and low magnetizations, moving with mildly relativistic Lorentz factors. In particular we find the dispersion relation for kink (m = ±1) and pinch (m = 0) modes. In the former we find that a wide range of wavelengths ∼ 1 1000 jet radii equally contributes to the instability with growth rates ∼ a few 10−3c/r j, while in the latter the large wavelengths are more unstable, giving similar growth rates. Evaluating the eigenfunctions of the instability we see that they attain their highest values near the jet boundary, indicating that the instabilities are most likely of a Kelvin-Helmholtz type rather than current driven.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114671140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling flux variability from internal shocks in relativistic jets","authors":"A. Zech, G. F. D. Clairfontaine, Z. Meliani","doi":"10.22323/1.354.0092","DOIUrl":"https://doi.org/10.22323/1.354.0092","url":null,"abstract":"Particle acceleration at stationary and moving internal shocks is one of the principal mechanisms to explain the variable emission, seen from the radio to the γ -ray band, from relativistic jets in radio-loud active galactic nuclei. To reproduce the synchrotron light curves associated with these shocks, we perform SRMHD simulations of magnetised relativistic transverse-structured jets using the AMRVAC code. Perturbations are injected at the base of a steady jet that carries stationary shocks to study the interaction between the moving and the stationary shocks. Synchrotron emission and radiative transfer are simulated in post-treatment. In a first application, the radio core of the radio-galaxy M 87 is modelled to study the flux evolution from such perturbations in the radio band and compare them against archival data. High Relativistic VII","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115150875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the interaction of pulsar winds and clumpy stellar winds","authors":"E. Kefala, V. Bosch-Ramon","doi":"10.22323/1.354.0031","DOIUrl":"https://doi.org/10.22323/1.354.0031","url":null,"abstract":"High-mass binaries hosting a non-accreting pulsar are sources of gamma rays, which are thought to originate in the wind-wind collision region. The stellar wind is expected to be clumpy, which could have important effects on the emitting flow dynamics, and thus on the associated non-thermal radiation. We adopt here a combination of Monte-Carlo and semi-analytical hydrodynamic calculations to explore the impact of clumps on the shocked wind structure on the scales of the binary system.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"171 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126063483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-wavelength properties of AGN jets: some recent highlights","authors":"L. Costamante","doi":"10.22323/1.354.0020","DOIUrl":"https://doi.org/10.22323/1.354.0020","url":null,"abstract":"Relativistic jets from Active Galactic Nuclei (AGN) are powerful sources of radiation at every wavelength, but particularly in gamma-rays. Multi-wavelength observations in the last decade, driven by the new generation of large-area GeV and TeV telescopes, have revealed several new aspects of their structure and emission properties. This paper summarizes some recent progress in our understanding of relativistic jets, focusing in particular on the following results: a) evidence against the Broad Line Region (BLR) as origin of seed photons for the inverse Compton (IC) mechanism; b) spectral variability in gamma-rays that defies the usual SED classification, c) discovery of extreme-TeV sources, which challenge standard acceleration and emission scenarios, d) evidence of relativistic motion at the VLBI scale also in high-energy peaked BL Lacs. Other fundamental topics such as ultra-fast variability, neutrino emission and M87 images at event horizon scale are only briefly mentioned, as discussed in other contributions at these proceedings.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130155378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mhd Accretion Disk Winds And The Blazar Sequence","authors":"S. Boula, D. Kazanas, A. Mastichiadis","doi":"10.22323/1.354.0009","DOIUrl":"https://doi.org/10.22323/1.354.0009","url":null,"abstract":"Fermi telescope has detected a significant number of AGNs to allow statistical treatment of their properties. Among others, it confirmed the ‘Blazar Divide’ in FSRQs and BL Lacs according to their gamma-ray spectral index and luminosity. We investigate this classification by proposing a model which reproduces in detail the broadband Blazar spectra and their statistical properties based on the physical parameters of their MHD accretion disk winds. This model describes the distribution of matter and magnetic fields in AGN at least over 5 decades in radius and it provides the vestiges of an account of the observed Blazar classification in terms of a single parameter, their mass accretion rate.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122209163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relativistic Jets From Black Hole Accretion Disc","authors":"I. Chattopadhyay, Mukesh K. Vyas, Kuldeep Singh","doi":"10.22323/1.354.0007","DOIUrl":"https://doi.org/10.22323/1.354.0007","url":null,"abstract":"Astrophysical jets from AGNs and microquasars are often relativistic and collimated. We study magnetic and radiative driving of jets to address these issues. The plasma is described by a relativistic equation of state which depends on the composition. We show that the matter content may not affect the streamline of magnetically driven jets, but the poloidal velocity and temperature distribution strongly depend on the composition of the jet. We also discuss the salient features of radiatively driven jets. Although consensus in the community precludes radiation driving to be an effective acceleration mechanism, we show that it is certainly not the case. For black holes surrounded by luminous discs, jets may be accelerated up to Lorentz factors of ∼ a few for baryon dominated jets. Interestingly, the terminal Lorentz factor may reach to a value of a few tens for lepton dominated jets. We also show that internal shocks driven by radiation are also possible in jets. Moreover, a temperature dependent scattering cross-section can produce relativistic jets that are launched with very low speeds and quite moderate temperatures, conditions which are expected in the inner region of the accretion discs. Although we have studied magnetic driving and radiative driving separately, it is apparent that both processes should be incorporated in order to solve the collimation and acceleration enigma of astrophysical jets. Relativistic Outflows VII","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"1101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122916308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gamma-ray spectrometry in the cutoff region as a key for the understanding of radiation processes in 3C 279","authors":"D. Zargaryan, C. Romoli, F. Aharonian","doi":"10.22323/1.354.0093","DOIUrl":"https://doi.org/10.22323/1.354.0093","url":null,"abstract":"We present results of spectrometric studies based on the observations of very strong 3C 279 flares in high and very-high-energy bands and discuss their implications regarding the origin of radiation mechanisms. The FSRQ 3C 279 (z=0.536) is one of the most luminous gamma-ray emitting AGN. It shows variability on time scales down to minutes during strong flares detected by the Fermi-LAT. We have analyzed LAT and Swift-XRT data for the flaring periods in June 2015 and January 2018, when the flux above 100 MeV during hourly time intervals could exceed $3 times 10^{-5}$ ph cm$^{-2}$ s$^{-1}$. The X-ray flux derived from Swift X-ray observations described by a very hard spectrum with photon index ~1.5 is typically explained by Inverse Compton scattering of low energy electrons and protons. Here we consider an alternative interpretation which describes the entire band from X-ray to very high energy as a results of synchrotron emission by ultra relativistic electrons or protons.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"134 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131052264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}