Conveners
Extragalactic Astrophysical accelerators
- Antonio Stamerra (Istituto Nazionale di Astrofisica (INAF))
Extragalactic Astrophysical accelerators
- Luca Foffano (Istituto Nazionale di Astrofisica (INAF))
Extragalactic Astrophysical accelerators
- Antonio Stamerra (Istituto Nazionale di Astrofisica (INAF))
Extragalactic Astrophysical accelerators
- Lara Nava (Istituto Nazionale di Astrofisica (INAF))
The physics of acceleration of charged particles in relativistic astrophysical sources represents a central question in modern high-energy astrophysics and multi-messenger astronomy. This talk will discuss modern developments in our understanding of Fermi-type processes in relativistic plasmas: acceleration at shock waves, acceleration in magnetized turbulence, and finally during the...
The detection of high energy astrophysical neutrinos is an important step towards finding the long-sought sources of cosmic rays. However, the long-exposure neutrino sky map by IceCube has not shown significant excesses so far and the sources of such energetic neutrinos remain unknown. Among the potential extragalactic neutrino sources, blazars are interesting candidates, as suggested by the...
AGN jets are the most powerful persistent emitters in the Universe, but the mechanisms through which they dissipate part of their energy flux and convey it to relativistic particles are still elusive. Despite advances on the numerical and theoretical side, the identification of the processes at work is made difficult by the huge range of spatial and temporal scales involved and by the strong...
Starburst Galaxies (SBGs) and Active Galactic Nuclei (AGNi) can launch and sustain powerful outflows of very high velocity and large opening angle.
Such winds develop a bubble structure characterized by an inner wind shock and an outer forward shock.
During the time the forward shock expands in the surrounding medium, the inner wind shock quickly decelerates while remaining strong, thereby...
Active Galactic Nuclei are the most powerful persistent sources in the Universe. Among them, blazars, AGN whose jet is pointed towards the Earth, present the most energetic emission. Lately a specific kind of blazar drew the attention of the gamma ray astronomy community: the extreme TeV blazars. These sources exhibit a peak of radiation at TeV energies and a hard intrinsic spectrum at sub-TeV...
I report here the results of a study of waiting times between Gamma-ray flares of FSRQ, defined as the time intervals between consecutive activity peaks.
I will show that this study constrains the physical mechanism responsible for gamma-ray emission.
We obtained that waiting times between flares can be...
BL Lacertae is an intermediate BL Lac object. It entered a flaring state in gamma energy range in August 2020. It was also found entering a flaring X-ray state. In this work, we examine the change in spectra of BL Lacertae with the variation in flux in X-ray energy range of 0.2-10.0 keV. For this, we took observations from the EPIC-PN instrument onboard XMM-Newton satellite. We did the...
Relativistic jets are a common manifestation of accreting black holes. Blazars are jets from supermassive black holes moving close to our line of sight. A common hypothesis for jet formation is that they are launched by powerful magnetic fields that thread the black hole. Here, I discuss the trip of the jet from the black hole to the much larger scales where it radiates. I argue that the jet...
Gamma-Ray Bursts (GRBs) are the strongest explosions in the Universe, and are powered by ultra-relativistic jets. They produce very bright emission both within the relativistic outflow (prompt gamma-ray emission, X-ray flares, reverse shock emission - optical flash and radio flare) and from the relativistic shock that they drive into the external medium (the long-lived broad-band afterglow...
The physical processes of the gamma-ray emission and particle acceleration during the prompt phase in gamma ray bursts (GRBs) are still unsettled. In order to perform an unambiguous physical modelling of observations, a clear identification of the emission mechanism is needed.
An instance of a clear identification is the synchrotron emission during the very strong flare in GRB160821A, that ...
The dominant radiation mechanism that produces the prompt emission in gamma-ray bursts (GRBs) remains a major open question. Spectral information alone has proven insufficient in elucidating its nature. Time-resolved linear polarization has the potential to distinguish between popular emission mechanisms, e.g. synchrotron radiation from electrons with a power-law energy distribution or inverse...
