The study of flaring astrophysical events in the multi-messenger approach requires instantaneous follow-up observations to better understand the nature of these events through complementary ...observational data. We present Astro-COLIBRI as a platform that integrates specific tools in the real-time multi-messenger ecosystem. The Astro-COLIBRI platform bundles and evaluates alerts about transients from various channels. It further automates the coordination of follow-up observations by providing and linking detailed information through its comprehensible graphical user interface. We present the functionalities with documented examples of Astro-COLIBRI usage through the community since its public release in August 2021. We highlight the use cases of Astro-COLIBRI for planning follow-up observations by professional and amateur astronomers, as well as checking predictions from theoretical models.
After the successful detection of cosmic high-energy neutrinos, the field of multiwavelength photon studies of active galactic nuclei (AGN) is entering an exciting new phase. The first hint of a ...possible neutrino signal from the blazar TXS 0506+056 leads to the anticipation that AGN could soon be identified as point sources of high-energy neutrino radiation, representing another messenger signature besides the established photon signature. To understand the complex flaring behavior at multiwavelengths, a genuine theoretical understanding needs to be developed. These observations of the electromagnetic spectrum and neutrinos can only be interpreted fully when the charged, relativistic particles responsible for the different emissions are modeled properly. The description of the propagation of cosmic rays in a magnetized plasma is a complex question that can only be answered when analyzing the transport regimes of cosmic rays in a quantitative way. In this paper, therefore, a quantitative analysis of the propagation regimes of cosmic rays is presented in the approach that is most commonly used to model non-thermal emission signatures from blazars, i.e., the existence of a high-energy cosmic-ray population in a relativistic plasmoid traveling along the jet axis. It is shown that in the considered energy range of high-energy photon and neutrino emission, the transition between diffusive and ballistic propagation takes place, significantly influencing not only the spectral energy distribution, but also the lightcurve of blazar flares.
Most cosmic ray particles observed derive from the explosions of massive stars. Massive stars from slightly above about 10M⊙ explode as supernovae via a mechanism which we do not know yet: two not ...mutually exclusive main ideas are an explosion driven by neutrinos, or the magneto-rotational mechanism, in which the magnetic field acts like a conveyor-belt to transport energy outwards for an explosion. Massive stars above about 25M⊙, depending on their heavy element abundance, commonly produce stellar black holes in their supernova explosions. When two such black holes find themselves in a tight binary system they finally merge in a gigantic emission of gravitational waves, events that have now been detected. The radio interferometric data demonstrate that all of these stars have powerful magnetic winds. After an introduction (Section 1) we introduce the basic concept (Section 2): Cosmic rays from exploding massive stars with winds always show two cosmic ray components at the same time: (i) the weaker polar cap component only produced by Diffusive Shock Acceleration, showing a relatively flat spectrum, and cut-off at the knee, and (ii) the stronger 4π component, which is produced by a combination of Stochastic Shock Drift Acceleration and Diffusive Shock Acceleration, with a down-turn to a steeper power-law spectrum at the knee, and a final cut-off at the ankle. In Section 3 we use the Alpha Magnetic Spectrometer (AMS) data to differentiate these two cosmic ray spectral components; these two cosmic ray components excite magnetic irregularity spectra in the plasma, and the ensuing secondary spectra can explain anti-protons, lower energy positrons, and other secondary particles. Cosmic ray electrons of the polar cap component interact with the surrounding photon field to produce positrons by triplet pair production, and in this manner may explain the higher energy positron AMS data. In Section 4 we test this paradigm with a theory of injection based on a combined effect of first and second ionization potential; this reproduces the ratio of cosmic ray source abundances to source material abundances. We can interpret the abundance data using the relation of the total number of ions enhanced by Q02A+2/3, where Q0 is the initial degree of ionization, and A is the mass number. This interpretation implies the high temperature as observed in the winds of blue super-giant stars; it also requires that cosmic ray injection happens in the shock travelling through such a wind. Most injection happens at the largest radii before slowing down due to interaction with the environment. In Section 5 we interpret the compact radio source 41.9 + 58 in the starburst galaxy M82 as a recent binary black hole merger, with an accompanying gamma ray burst. The tell-tale observational sign is the conical cleaning sweep of the relativistic jet during the merger, observed as an open cone with very low radio emission. This can also explain the Ultra High Energy Cosmic Ray (UHECR) data in the Northern sky. Thus, by studying the cosmic ray particles, their abundances at knee energies, and their spectra, we can learn about what drives these stars to produce the observed cosmic rays.
COSMIC-RAY TRANSPORT AND ANISOTROPIES Biermann, Peter L; Tjus, Julia Becker; Seo, Eun-Suk ...
The Astrophysical journal,
05/2013, Volume:
768, Issue:
2
Journal Article
Peer reviewed
Open access
We show that the large-scale cosmic-ray anisotropy at ~10 TeV can be explained by a modified Compton-Getting effect in the magnetized flow field of old supernova remnants. Cosmic rays arrive ...isotropically to the flow field and are then carried along with the flow to produce a large-scale anisotropy in the arrival direction. This approach suggests an optimum energy scale for detecting the anisotropy. Two key assumptions are that propagation is based on turbulence following a Kolmogorov law and that cosmic-ray interactions are dominated by transport via cosmic-ray-excited magnetic irregularities through the stellar wind of an exploding star and its shock shell. A prediction is that the amplitude is smaller at lower energies due to incomplete sampling of the velocity field and also smaller at larger energies due to smearing.
The search for the sources of high-energy cosmic rays (CRs) has made significant progress the past decade. By including multimessenger methods, the general picture of the presence of a Galactic ...component at low energies and an extragalactic one at the highest energies has been strengthened. Yet, unambiguous proof of the exact origins of CRs is missing. In this review, the current scientific status on Galactic CR sources from theory and experimental data is summarized. In particular, the focus of this review lies on the search for photon and neutrino signals from the Galaxy and their theoretical interpretation in the context of the quest for the origin of high-energy cosmic rays. The use of multiwavelength data, from radio to TeV energies, as well as the option of coincident observations of different wavelength bands in order to pin-point the sources of Galactic CRs are discussed. Finally, the objectives for the field of astroparticles to reach the goal of unambiguously identifying Galactic cosmic ray sources within the next decades are presented.
Context.
Cosmic-ray propagation is strongly dependent on the large-scale configuration of the Galactic magnetic field. In particular, the Galactic center region provides highly interesting cosmic-ray ...data from gamma-ray maps and it is clear that a large fraction of the cosmic rays detected at Earth originate in this region of the Galaxy. Yet because of confusion from line-of-sight integration, the magnetic field structure in the Galactic center is not well known and no large-scale magnetic field model exists at present.
Aims.
In this paper, we develop a magnetic field model, derived from observational data on the diffuse gas, nonthermal radio filaments, and molecular clouds.
Methods.
We derive an analytical description of the magnetic field structure in the central molecular zone by combining observational data with the theoretical modeling of the basic properties of magnetic fields.
Results.
We provide a first description of the large-scale magnetic field in the Galactic center region. We present first test simulations of cosmic-ray propagation and the impact of the magnetic field structure on the cosmic-ray distribution in the three dimensions.
Conclusions.
Our magnetic field model is able to describe the main features of polarization maps; it is particularly important to note that they are significantly better than standard global Galactic magnetic field models. It can also be used to model cosmic-ray propagation in the Galactic center region more accurately.
Abstract The very high energy (VHE) emission of the central molecular zone (CMZ) is rarely modeled in 3D. Most approaches describe the morphology in 1D or simplify the diffusion to the isotropic ...case. In this work, we show the impact of a realistic 3D magnetic field configuration and gas distribution on the VHE γ -ray distribution of the CMZ. We solve the 3D cosmic-ray transport equation with an anisotropic diffusion tensor using the approach of stochastic differential equations as implemented in the CRPropa framework. We test two different source distributions for five different anisotropies of the diffusion tensor, covering the range of effectively fieldline-parallel diffusion to isotropic diffusion. Within the tested magnetic field configuration, the anisotropy of the diffusion tensor is close to the isotropic case, and three point sources within the CMZ are favored. Future missions such as the upcoming CTA will reveal more small-scale structures that are not yet included in the model. Therefore, a more detailed 3D gas distribution and magnetic field structure will be needed.
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