The underlying particle acceleration mechanism in blazars and the radiation mechanism of the blazar high-energy spectral component are still not well understood. Multi-wavelength polarization signatures can provide unique constraints on the blazar radiation and plasma physics. This talk aims to emphasize the need of the multi-zone picture for the blazar leptonic and hadronic models. Under such...
I will show that current mm-to-X-ray polarization trends, observed during recent IXPE campaigns for HBLs, and the ROBOPOL trend for Fermi blazars, relating the fractional polarization to the peak frequency of the synchrotron emission, can be successfully reproduced by a multi-zone scenario without the need for an energy-stratified scenario. I will also discuss some implications for the...
Recent advancements in gamma-ray observations and theoretical modeling are transforming our understanding of relativistic jets across scales, from black hole X-ray binaries (BHXBs) to active galactic nuclei (AGN). Jets are efficient cosmic ray (CR) accelerators to PeV energies, contributing to the diffuse gamma-ray and neutrino fluxes. In BHXBs, jets persist even during quiescence, like the...
I discuss recent results of a leptohadronic model applied to a sample of 32 BL Lac objects associated with IceCube high-energy alert events. The model is constrained using multi-wavelength observations as well as optical spectral analyses, which provide valuable information on the source environment. For masquerading BL Lacs, including TXS 0506+056, the model predicts high neutrino fluxes,...
Recent multi-wavelength observations of gamma-ray burst afterglows observed in the TeV energy range challenge the simplest Synchrotron Self-Compton (SSC) interpretation of this emission and are consistent with a single power-law component spanning over eight orders of magnitude in energy. To interpret this generic behaviour in the single-zone approximation without adding further free...
Four tidal disruption events—Sw J1644, Sw J1112, Sw J2058, and AT 2022cmc—have been identified as exhibiting luminous jets accompanied by rapidly declining non-thermal X-ray emissions. In this talk, I will discuss our recent work on modeling the multi-wavelength emissions from the jetted TDE AT2022cmc, where a two-component jet is considered to interpret the spectral and temporal signatures of...
To identify the sources of cosmic-rays, and characterize their astrophysical properties we need to exploit the full potential of multi-messenger observations in combination with theoretical models. We aim to ease the theoretical interpretation of multi-messenger datasets by providing to the community a minimization tool using the open-source Python package Gammapy.
For this purpose,...
Blazar jets are prolific sources of high energy electromagnetic radiation but their emission region, the “blazar zone”, is uncertain because of the inherent limitation of our head-on view of the jets. Emission models vary in both the acceleration mechanism powering the blazar zone and the latter’s extent and location. Here we have adopted a model of magnetic reconnection that drives continuous...
We investigate ultra-fast outflows (UFOs) in active galactic nuclei (AGN) as potential sources of ultra-high-energy cosmic rays (UHECRs), focusing on cosmic-ray nuclei, an aspect not explored previously. These large-scale, mildly-relativistic outflows are a common feature of AGN. We study the cosmic-ray spectrum and maximum energy attainable in these environments with 3D CRPropa simulations...
The detection by the KM3NeT experiment of the ultra-high-energy event KM3-230213A is a milestone in neutrino astrophysics. With an energy estimated at ~220 PeV, it is the most energetic neutrino observed to date, challenging the current understanding of the cosmic spectrum. Its observation opens the question of its astrophysical origin. Blazars and their relativistic jets have been proposed as...
The electromagnetic flare of the flat-spectrum radio quasar (FSRQ) 3C 454.3 in November 2010 was the brightest $\gamma$-ray flare ever observed by the Fermi-LAT from a blazar. We performed the data analysis of the multiwavelength (from infrared photons to $\gamma$ rays) quasi-simultaneous one-day-averaged spectral-energy distributions (SEDs) for seven days of the flare and modelled the...
Blazars are a subclass of Active Galactic Nuclei (AGN) powered by the accretion of matter to a supermassive black hole (SMBH). Charged particles can be accelerated in the jets produced near the SMBH and produce non-thermal radiation relativistically boosted in the observer's frame. Recently a high-energy neutrino has been detected from the direction of a distant blazar known as TXS 0506+056,...
Blazars are luminous astrophysical objects that show a high variability in brightness. They emit powerful relativistic jets which are aligned with the observer's line of sight. The broad emission from radio up to gamma rays can be explained by interactions of non-thermal particles in the jet. Nonetheless, the origin of the high-energy emission of blazars is still not clear. Various theoretical...
This talk will discuss recent work on the connection between blazar flares and high-energy astrophysical neutrinos. Using the time-dependent lepto-hadronic code OneHaLe, we analysed the spectral energy distributions and light curves of several bright γ-ray flares observed by the Fermi Large Area Telescope. The results indicate that the calorimetric estimates for neutrino production rates...
Rapid flux variability over a large range of wavelengths is a well-known signature of emission from blazars, with variability time scales of the order of a few days and below frequently observed at high energies.
Different radiative models with varying degrees of complexity are being developed to either reproduce individual flare events or overall statistical behaviour, but a general picture...
Supermassive black holes reside in the center of galaxies and are characterised that not even light can escape their gravitational pull.
However, in their direct vicinity high-energies flares occur, particles are accelerated to highest energies and relativistic outflows are launched.
In order to understand these phenomena we perform GRMHD simulations of accreting black holes taking magnetic...
