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

{"title":"Analyzing The December 2013 Orphan Gamma-Ray Flare From 3C 279","authors":"T. Lewis, J. Finke, P. Becker","doi":"10.22323/1.354.0075","DOIUrl":"https://doi.org/10.22323/1.354.0075","url":null,"abstract":"Multiwavelength monitoring of the blazar 3C 279 observed a very bright, 12-hour, orphan gamma-ray flare on 20 Dec 2013 with a uniquely hard Fermi-LAT spectrum and high Compton dominance. We work with a one-zone, leptonic model with both first- and second-order Fermi acceleration, which now reproduces the unique flaring behavior. We present a simplified analytic electron energy distribution to provide intuition about how particle acceleration shapes multi-wavelength blazar jet emission spectra. The contributions of individual processes in relativistic jets is fundamental to understanding the particle energy budget in the formation and propagation of astrophysical jets. We show that first- and second-order Fermi acceleration are sufficient to explain the flare, and that magnetic reconnection is not needed. Our analysis suggests that the flare is initiated by an increase in the particle energies due to shock acceleration, which also increases the stochastic acceleration. The higher energy particle preferentially occupy the outer jet, along the sheath, which decreases the apparent magnetic field and synchrotron radiation, while increasing electron exposure to the broad line region photon fields, driving up the external Compton emission.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"38 10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130882841","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":"Propagation and stability of relativistic jets","authors":"M. Perucho","doi":"10.22323/1.354.0099","DOIUrl":"https://doi.org/10.22323/1.354.0099","url":null,"abstract":"A simple look at the steady high-energy Universe reveals a clear correlation with outflows generated around compact objects (winds and jets). In the case of relativistic jets, they are thought to be produced as a consequence of the extraction of rotational energy from a Kerr black hole (Blandford-Znajek), or from the disc (Blandford-Payne). A fraction of the large energy budget provided by accretion and/or black hole rotational energy is invested into jet formation. After formation, the acceleration and collimation of these outflows allow them to propagate to large distances away from the compact object. The synchrotron cooling times demand that re-acceleration of particles takes place along the jets to explain high-energy and very-high-energy emission from kiloparsec scales. At these scales, jets in radio galaxies are divided in two main morphological/luminosity types, namely, Fanaroff-Riley type I and II (FRI, FRII), the latter being more luminous, collimated and edge-brightened than the former, which show clear hints of decollimation and deceleration. In this contribution, I summarise a set of mechanisms that may contribute to dissipate magnetic and kinetic energy: Magnetohydrodynamic instabilities or jet-obstacle interactions trigger shocks, shearing and mixing, which are plausible scenarios for particle acceleration. I also derive an expression for the expected distance in which the entrainment by stellar winds starts to be relevant, which is applicable to FRI jets. Finally, I discuss the differences in the evolutionary scenarios and the main dissipative mechanisms that take place in extragalactic and microquasar jets.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123658998","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":"Calibrating The Power Of Relativistic Jets","authors":"L. Foschini, M. Lister, T. Hovatta, Y. Kovalev, P. Romano, S. Vercellone, A. Lähteenmäki, T. Savolainen, M. Tornikoski, E. Angelakis, M. Berton, V. Braito, S. Ciroi, M. Kadler, P. Burd","doi":"10.22323/1.354.0070","DOIUrl":"https://doi.org/10.22323/1.354.0070","url":null,"abstract":"There are several methods to calculate the radiative and kinetic power of relativistic jets, but their results can differ by one or two orders of magnitude. Therefore, it is necessary to perform a calibration of the jet power, to understand the reasons for these differences (whether wrong hypotheses or intrinsic source variability), and if it is possible to converge to a reliable measurement of this physical quantity. We present preliminary results of a project aimed at calibrating the power of relativistic jets in active galactic nuclei (AGN) and X-ray binaries (XRB). We started by selecting all the AGN associations with known redshift in the Fourth Fermi LAT Gamma-Ray Catalog (4FGL). We then calculated the radiative and/or kinetic powers from available data or we extracted this information from literature. We compare the values obtained for overlapping samples and highlight early conclusions.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128164480","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":"Inclination Dependence Of The Time-Lag – Photon-Index Correlation In BHXRBs And Its Explanation With A Simple Jet Model","authors":"N. Kylafis, P. Reig","doi":"10.22323/1.354.0037","DOIUrl":"https://doi.org/10.22323/1.354.0037","url":null,"abstract":"Recently, we reported an observational correlation between a) the time-lag of the hard (9 - 15 keV) with respect to the soft (2 - 5 keV) X-ray photons in black-hole X-ray binaries (BHXRBs) and b) the power-law photon index $Gamma$ of the X-ray spectrum. This was physically explained with a simple jet model, i.e., a model where the Comptonization (the Compton upscattering of soft photons) happens in the jet. Here, we report the inclination dependence of this correlation, which we also explain with our jet model. Photons that emerge at different polar angles from the jet axis have different spectra and different time-lags. Because of this, we can explain quantitatively the type-B QPOs of GX 339-4 as resulting from a precessing jet.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134036542","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":"Generalized Fermi Acceleration","authors":"M. Lemoine","doi":"10.1103/PHYSREVD.99.083006","DOIUrl":"https://doi.org/10.1103/PHYSREVD.99.083006","url":null,"abstract":"In highly conducting astrophysical plasmas, charged particles are generically accelerated through Fermi-type processes involving repeated interactions with moving magnetized scattering centers. The present paper proposes a generalized description of these acceleration processes, by following the momentum of the particle through a continuous sequence of accelerated frames, defined in such a way that the electric field vanishes at each point along the particle trajectory. In each locally inertial frame, the Lorentz force affects the direction of motion of the particle, but the energy changes solely as a result of inertial corrections. This unified description of Fermi acceleration applies equally well in sub- and ultrarelativistic settings, in Cartesian or non-Cartesian geometries, flat or nonflat space-time. Known results are recovered in a variety of regimes—shock, turbulent and shear acceleration—and new results are derived in lieu of applications, e.g., nonresonant acceleration in relativistic turbulence, stochastic unipolar inductive acceleration and centrifugo-shear acceleration close to the horizon of a black hole.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129671624","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":"Structure of a collisionless pair jet in a magnetizedelectron-proton plasma: Flow-aligned magnetic field","authors":"M. Dieckmann, D. Folini, I. Hotz, A. Nordman, P. Dell'Acqua, A. Ynnerman, R. Walder","doi":"10.1051/0004-6361/201834393","DOIUrl":"https://doi.org/10.1051/0004-6361/201834393","url":null,"abstract":"Aims. We study the effect a guiding magnetic field has on the formation and structure of a pair jet that propagates through a collisionless electron–proton plasma at rest. Methods. We model with a particle-in-cell (PIC) simulation a pair cloud with a temperature of 400 keV and a mean speed of 0.9c (c - light speed). Pair particles are continuously injected at the boundary. The cloud propagates through a spatially uniform, magnetized, and cool ambient electron–proton plasma at rest. The mean velocity vector of the pair cloud is aligned with the uniform background magnetic field. The pair cloud has a lateral extent of a few ion skin depths. Results. A jet forms in time. Its outer cocoon consists of jet-accelerated ambient plasma and is separated from the inner cocoon by an electromagnetic piston with a thickness that is comparable to the local thermal gyroradius of jet particles. The inner cocoon consists of pair plasma, which lost its directed flow energy while it swept out the background magnetic field and compressed it into the electromagnetic piston. A beam of electrons and positrons moves along the jet spine at its initial speed. Its electrons are slowed down and some positrons are accelerated as they cross the head of the jet. The latter escape upstream along the magnetic field, which yields an excess of megaelectronvolt positrons ahead of the jet. A filamentation instability between positrons and protons accelerates some of the protons, which were located behind the electromagnetic piston at the time it formed, to megaelectronvolt energies. Conclusions. A microscopic pair jet in collisionless plasma has a structure that is similar to that predicted by a hydrodynamic model of relativistic astrophysical pair jets. It is a source of megaelectronvolt positrons. An electromagnetic piston acts as the contact discontinuity between the inner and outer cocoons. It would form on subsecond timescales in a plasma with a density that is comparable to that of the interstellar medium in the rest frame of the latter. A supercritical fast magnetosonic shock will form between the pristine ambient plasma and the jet-accelerated plasma on a timescale that exceeds our simulation time by an order of magnitude.","PeriodicalId":164251,"journal":{"name":"Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127002155","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}