-
Jonathan Biteau ({UNIV PARIS-SACLAY}UMR9012)18/11/2026 14:00
The extragalactic sky at the highest energies is shaped by the complex interplay between relativistic messengers and the diffuse electromagnetic fields through which they propagate. Grounded in multi-messenger frameworks and empirical models of cosmic-ray transport, this talk provides a comprehensive synthesis of very-high-energy gamma-ray and ultra-high-energy cosmic-ray propagation across...
Aller à la page de la contribution -
Gwenael GIACINTI (APC Paris)18/11/2026 14:45
Gamma-ray observations provide important information on cosmic-ray (CR) propagation in our Galaxy.First, we present a new model of CR propagation in the Milky Way, where CRs are injected at discrete transient sources in the disc. We then calculate the corresponding diffuse Galactic gamma-ray emission. We find that the diffuse gamma-ray emission above 100 TeV is very clumpy, and does not...
Aller à la page de la contribution -
Irina Dvorkin (Institut d'Astrophysique de Paris)18/11/2026 15:05
The detection of gravitational waves from compact-binary coalescences by LIGO–Virgo–KAGRA has opened a new window onto the Universe. As detector sensitivities improve, and with the advent of future observatories such as LISA and the Einstein Telescope, the number and diversity of individually detectable gravitational-wave sources will increase dramatically. Yet many more sources will remain...
Aller à la page de la contribution -
Yoann GÉNOLINI (LAPTh, Annecy)18/11/2026 15:25
Over the past decade, a wealth of new data has ushered in an era of precision cosmic-ray physics. By revealing previously unanticipated features in cosmic-ray spectra, these observations challenge current paradigms of Galactic cosmic-ray acceleration and transport. When it comes to modeling cosmic-ray transport in magnetic turbulence, existing theoretical models still struggle to accurately...
Aller à la page de la contribution -
Enrico Peretti (APC)18/11/2026 16:15
The origin of Galactic PeV cosmic rays remains one of the central questions in high-energy astrophysics. Stellar-mass compact objects, such as ultraluminous X-ray sources and microquasars, launch powerful outflows that inflate wind bubbles or produce collimated jets, naturally giving rise to long-lived shock fronts where diffusive shock acceleration can operate efficiently. In this...
Aller à la page de la contribution -
Emilie Parent (Institut de Planétologie et d'Astrophysique de Grenoble)18/11/2026 16:30
The Galactic bulge is expected to host a large population of old millisecond pulsars (MSPs), which could contribute substantially to unresolved X-ray emission and the elusive Fermi-LAT Galactic-centre gamma-ray excess (GCE). Yet few pulsars have been detected toward the Galactic centre, where particularly severe observational biases make MSPs more difficult to find.
Propulsing is an...
Aller à la page de la contribution -
Rebecca Diesing (University of Chicago)18/11/2026 16:45
Merging galaxy clusters exhibit strong observational evidence for efficient cosmic ray acceleration, particularly in the form of synchrotron-emitting radio relics and halos. These particles are likely accelerated at merger and accretion shocks. However, in the presence of the large diffusion coefficients one would expect in the relatively unmagnetized intracluster medium (ICM), long...
Aller à la page de la contribution -
Dr Adrian Faucher (IPAG)18/11/2026 17:00
Globular clusters (GCs) are known to host an important population of millisecond pulsars (MSPs). Terzan 5, located at 5.5 kpc from Earth, contains 49 known MSPs, with additional sources expected to remain undetected due to dispersion and instrumental sensitivity limits. These unresolved MSPs are expected to contribute to the diffuse radio emission observed towards the cluster. Using...
Aller à la page de la contribution -
Olivier Martineau (LPNHE)18/11/2026 17:08
I will present the status and perspectives of the two projects for radio detection of UHE cosmic particles in which CNRS is involved.
Aller à la page de la contribution -
Claire Guepin (LUPM)18/11/2026 17:15
-
Matteo Cerruti (Université de Paris - APC), Susanna Diana VERGANI (CNRS-Observatoire de Paris)19/11/2026 09:00
-
Mouad Gnaoui (IAP, Sorbonne Université)19/11/2026 09:45
Gamma Ray Burst prompt emission is widely attributed to radiation from accelerated electrons within ultra-relativistic ejecta. The detection of high energy components in several GRBs, along with the theoretical predictions of inverse Compton scattering, suggest the presence of abundant photons above the pair production threshold in the comoving frame. Under such conditions, photon-photon...
Aller à la page de la contribution -
Sofia Bisero (GEPI, Observatoire de Paris, Université PSL, CNRS)19/11/2026 10:05
I will discuss the key ingredients required to model the multi-messenger emission from binary neutron star mergers, from gravitational waves to electromagnetic radiation, highlighting the main degeneracies and open questions. I will then move from individual events to populations, describing how synthetic populations can be constructed, from astrophysical assumptions to observational predictions.
Aller à la page de la contribution -
15. From numerical simulations to Bayesian inference: surrogate models for time-resolved blazar SEDsDamien BEGUE (APC)19/11/2026 10:25
Time-resolved spectral energy distributions (SEDs) provide a powerful probe of the physical evolution of highenergy sources, but extacting this information with detailed numerical models is computationally challenging. This becomes particularly prohibitive when full posterior sampling is required. To address this challenge, we developed a surrogate-modeling framework, based on convolutional...
Aller à la page de la contribution -
Dr Jonatan Jacquemin19/11/2026 11:15
Relativistic jets are observed in some accreting black-hole systems but not others. In X-ray binaries, jet production is closely associated with geometrically thicker accretion states, suggesting that disk thickness may play a fundamental role in determining whether a black hole can launch a powerful jet. We investigate this connection using global three-dimensional GRMHD simulations of...
Aller à la page de la contribution -
Georgios Vasilopoulos (National and Kapodistrian University of Athens)19/11/2026 11:30
Leptohadronic modeling of jet emission is central to interpreting multimessenger observations, but time-dependent kinetic codes such as AM3 and LeHaMoC are too slow for Bayesian fitting over high-dimensional parameter spaces. We present GRU-based neural network emulators trained on large AM3 and LeHaMoC SED libraries. They reproduce the full broadband spectra with high accuracy at millisecond...
Aller à la page de la contribution -
Zeljka Bosnjak (IAP)19/11/2026 11:45
The multi-wavelength observations of gamma-ray bursts provide insights into the physical conditions in the relativistic jets responsible for their emission. I will discuss new X-ray observations and present the properties of X-ray emission computed in the standard GRB framework of internal shocks. Numerical simulations of the emitted spectrum in the comoving frame performed for a large...
Aller à la page de la contribution -
Arthur Charlet19/11/2026 12:00
Gamma-ray bursts (GRBs) release a star's lifetime energy in seconds through an ultra relativistic jet, but the exact process behind the jet prompt emission remains unknown. In the internal shocks model, variations in the jet velocity causes the material to collide at a large distance from the source. These collisions accelerates electrons which emits this energy as gamma-rays through efficient...
Aller à la page de la contribution -
Lea Heckmann (APC)19/11/2026 12:04
The origin of astrophysical neutrinos and ultra-high-energy cosmic rays remains one of the central questions of the multi-messenger era. While numerous classes of astrophysical sources have been proposed as potential accelerators, the underlying particle acceleration and emission mechanisms remain uncertain. Combining observations across multiple messengers with advanced modeling tools is key...
Aller à la page de la contribution -
Clément Pellouin (CEA - AIM)19/11/2026 12:08
In this flash talk, I will present key features of gamma-ray burst (GRB) afterglows across the electromagnetic spectrum (X-ray plateaus, optical rebrightenings, radio variability). I will show examples of observations with the SVOM mission and discuss how they help gain physical insights into the progenitor properties (central engine and environment characteristics, particle acceleration and...
Aller à la page de la contribution -
HELENE SOL (LUTH)19/11/2026 12:12
Analysis of a sample of 1233 active galactic nuclei (AGN) common to the ICRF3 (radio VLBI), Gaia (optical), and Fermi/4FGL-DR4 (gamma-ray) catalogs makes it possible to identify the regions of these sources that are brightest in the optical and likely also in the gamma-ray bands. For the majority of them, this active zone is indiscernible from the AGN core (~ 80%), while for a significant...
Aller à la page de la contribution -
Matteo Bugli (Institut d'astrophysique de Paris - CNRS)19/11/2026 12:15
-
Anne Decourchelle (Dap/AIM, CEA Paris-Saclay)19/11/2026 14:30
Supernovae and supernova remnants (SNRs) play a fundamental role in galactic ecosystems. They are primary drivers of chemical enrichment, injecting heavy elements synthesized during stellar evolution and explosive nucleosynthesis into the interstellar medium (ISM). Their shocks heat and structure the ISM. They accelerate particles, contribute to turbulence and magnetic field amplification, and...
Aller à la page de la contribution -
Julien Froustey (IFIC, Universitat de València)19/11/2026 15:15
Accurately modeling neutrino flavor oscillations in global simulations of core-collapse supernovae remains a major challenge, albeit a potentially crucial one for making reliable predictions. Indeed, it is now widely recognized that flavor instabilities, in which neutrino distributions computed in classical transport frameworks can be dramatically reshaped by flavor conversion, are ubiquitous...
Aller à la page de la contribution -
Phan Vo Hong Minh (LUX)19/11/2026 15:35
I will present current progress on Galactic cosmic-ray transport with a strong focus on the escape of cosmic rays around supernova remnants studied using particle-in-cell simulations. Some results concerning the transport of cosmic rays in their self-generated turbulence will be discussed together with potential observational consequences.
Aller à la page de la contribution -
Vincent Tatischeff (IJCLab)19/11/2026 15:55
Classical and recurrent novae are powered by thermonuclear runaways on the surfaces of accreting white dwarfs. Novae have emerged as an important class of astrophysical particle accelerators, as demonstrated in particular by the discovery of GeV gamma-ray emission with Fermi-LAT. In classical novae, particle acceleration is thought to occur primarily at internal shocks within the ejecta, which...
Aller à la page de la contribution -
Michelle Tsirou (Institute of Physics of the Czech Academy of Sciences (FZU))19/11/2026 16:45
Shocks are abundant in astrophysical systems, and are promising candidates for extremely efficient particle acceleration. As shocks can travel in different-density media and have a range of properties, they can give rise to colliding flows. Such may create initially double structures, bound by the forward and reverse propagating shocks. The aim of our study is to investigate the extent of...
Aller à la page de la contribution -
Lorenzo Stefanuto (Università di Torino)19/11/2026 17:00
Supernova remnants (SNRs) are generally recognized as the primary sources of Galactic cosmic-ray electrons. Models usually approximate particle injection into the interstellar medium as an instantaneous burst with a phenomenological analytical spectrum. In this work, we consider a time-dependent electron injection framework based on the Sedov-Taylor model of SNR evolution. This allows us to...
Aller à la page de la contribution -
Weipeng Yao (LUX)19/11/2026 17:15
The origin of high-energy cosmic rays remains one of the central open questions in astrophysics. Collisionless shocks are widely recognized as efficient particle accelerators, but the microphysics of early-stage ion energization -- before a fully nonlinear shock structure develops -- is still poorly constrained, particularly in regimes where large-scale interchange-type instabilities such as...
Aller à la page de la contribution -
Dr Marco Cusinato (CEA-Saclay)19/11/2026 17:30
Core-collapse supernovae are among the most powerful explosions in the universe, and they are sources of multimessenger emission, as they emit gravitational waves, neutrinos and electromagnetic radiation. In the present study, we investigate the rotation contribution in a series of state-of-the-art two dimensional core collapse supernova simulations. We identify a range of pre-collapse...
Aller à la page de la contribution -
Xingwei Gong (Observatoire de Paris)19/11/2026 17:35
Observations, numerical simulations, and laboratory experiments relevant to supernova remnant shock waves show a significant deviation of the energy partition between electrons and ions from the naive prediction based on adiabatic compression of the electron population at the shock front. High-Mach number perpendicular shock waves are mediated by plasma instabilities driven by a beam of...
Aller à la page de la contribution -
Nicolas Houry19/11/2026 17:40
Predicting the outcome of core collapse in massive stars (whether the star explodes as a supernova or collapses into a black hole) remains an open problem. The complex physics involved and the uncertainties in progenitor structure make it difficult to identify which stars are more likely to explode. Recent studies suggest that the density gradient at the interface between the silicon and...
Aller à la page de la contribution -
Raphaël Raynaud (CEA Saclay)19/11/2026 17:45
-
pierre-olivier petrucci (IPAG)20/11/2026 09:00
Accreting black holes are powerful astrophysical sources whose emission provides a unique probe of the extreme environments surrounding compact objects. Their broadband radiation, from radio to X-rays and gamma rays, reveals the complex interplay between accretion disks, relativistic jets, and outflows. I will show how we can investigate the structure and dynamics of the inner accretion flows...
Aller à la page de la contribution -
Dr Yohan Dubois (Institut d'Astrophysique de Paris)20/11/2026 09:45
Cosmological hydrodynamical simulations are a powerful tool for modelling the complexity of galaxy formation, along with the supermassive black holes (SMBHs) at their centres. I will begin by reviewing how modern simulations model SMBH growth, including gas accretion, active galactic nucleus feedback, and black hole mergers. I will then present the resulting predicted SMBH populations and show...
Aller à la page de la contribution -
Irene Urso (LIRA, Paris Observatory)20/11/2026 10:05
Three computational steps are required to construct synthetic electromagnetic observations of black hole accretion flows, specifically source modelling, general relativistic ray tracing, and general relativistic radiative transfer (GRRT). In this talk, we review various existing approaches, highlighting their respective advantages and limitations. For source modelling, we discuss...
Aller à la page de la contribution -
Martin Lemoine (APC (Astroparticule & Cosmologie, CNRS - Université de Paris))20/11/2026 10:25
This talk will review some recent progress in numerical modelling of turbulence in extreme environments, its relevance for energy dissipation, particle tranport, and acceleration, and its connections to high-energy multimessenger astrophysics.
Aller à la page de la contribution -
Jonathan Ferreira (IPAG)20/11/2026 11:15
It is now well established that whenever a large scale magnetic field is threading an accretion disk, super fast-magnetosonic outflows are launched transporting mass, angular momentum and energy from the disk, and allowing thereby accretion. This interdependent accretion-ejection process is nowadays theoretically understood, at least in a qualitative way.
There are however several aspects...
Aller à la page de la contribution -
Rafan Muhammad20/11/2026 11:30
Accretion flows around black holes result from a complex combination between radiative cooling, advection and ejection. The Jet Emitting Disk–Standard Accretion Disk (JED–SAD) model provides a self-consistent description of these processes. Its thermal structure is computed with DYPLO, a radial solver that determines the local thermal equilibrium of the accretion flow, including quantities...
Aller à la page de la contribution -
M. Élie Sévègnes (Institut de Recherche en Astrophysique et Planétologie)20/11/2026 11:45
The geometry of black hole coronae, which is responsible for the hard X-ray emission in X-ray binaries, is still poorly constrained. Open-source radiative transfer codes are key to bridge the gap between observed spectra and semi-analytical models or first-principles plasma simulations.
Aller à la page de la contribution
In this talk, I present Fig: a new ray-tracing code usable as a stand-alone and for post-processing... -
Emile Dosso (Institut d'Astrophysique de Paris)20/11/2026 12:00
JWST observations up to z ≈ 11 have uncovered unexpected populations of high-redshift AGN, suggesting a much higher abundance of massive black holes (MBH) in the early Universe than predicted by prior extrapolations of observational datasets. However, state-of-the-art simulations of MBH accretion yield results inconsistent with these findings: they suggest that massive black holes grow too...
Aller à la page de la contribution -
Sébastien Le Bihan (APC - CNRS,UPC)20/11/2026 12:04
Stochastic particle acceleration in magnetized turbulent plasmas, such as those found in the coronae of Active Galactic Nuclei, has emerged as a key mechanism for explaining their multi-messenger emission. However, a major challenge lies in bridging the gap between the microphysical processes that govern particle acceleration and the macrophysical scales of these compact environments.
Aller à la page de la contribution
In this... -
Maxime Parra (Ehime University Japon)20/11/2026 12:08
Classical thin-disk theory explains the spectra observed in Black hole accretion disks but predicts thermal instability in the luminous regime, in sharp contrast with the long-lived soft states of X-ray binaries and the sustained luminous activity of bright quasars. Recently, the addition of full angle-dependent radiation transport in general relativistic radiation-magnetohydrodynamic...
Aller à la page de la contribution -
Razieh Ranjbar (IPM - Institute for Research in Fundamental Sciences)20/11/2026 12:12
We have investigated the influence of dark matter halos on quasi-spherical accretion onto supermassive black holes (SMBHs) using general relativistic hydrodynamic (GRHD) simulations. By incorporating Hernquist and NFW halo profiles into the BHAC code, we model accretion flows with zero and low angular momentum across a range of halo-to-BH mass ratios up to 10. Our results show that the...
Aller à la page de la contribution -
Raphaël Mignon-Risse (CNES/APC)20/11/2026 12:15
-
Lucas Guillemot (LPC2E/CNRS and Université d'Orléans)20/11/2026 14:30
-
Mattéo Sautron (ObAS)20/11/2026 15:00
Population synthesis is a powerful numerical tool that allows one to infer the parameters characterizing a given population.
Aller à la page de la contribution
Within this framework, pulsars and magnetars are generated at birth and their evolution is followed up to the present epoch.
Once this evolution is modeled, detection criteria are applied in order to determine whether each object in the simulated population would be... -
Enzo Figueiredo (IPAG, CNRS, Université Grenoble Alpes)20/11/2026 15:20
Recent high-angular-resolution observations of black holes have revealed magnetospheric structures in their immediate vicinity, which may drive active galactic nuclei jets and particle acceleration. Fundamental questions persist regarding jet launching and the variability of electromagnetic emission. In this talk, I present how general relativistic kinetic plasma simulations have transformed...
Aller à la page de la contribution -
Arno Vanthieghem (Observatoire de Paris)20/11/2026 15:40
Fast radio bursts (FRBs) are among the most luminous coherent transients in the Universe, yet the physical mechanisms responsible for their emission remain poorly understood. In this talk, I will explore the kinetic physics underlying a theoretical scenario in which low-frequency fast magnetosonic waves, launched by magnetar activity, steepen as they propagate through the declining background...
Aller à la page de la contribution -
Dominic Bernardi (IPAG)20/11/2026 16:00
Magnetars are highly magnetized neutron stars characterized by their frequent, energetic X-ray bursts. Dynamic motion of magnetar crust has been theorized to fill the magnetosphere with low frequency plasma waves that eventually power the transients we observe. It was recently realized that fast magnetosonic (fast) waves, one of the two low frequency wave modes in the highly magnetized limit,...
Aller à la page de la contribution -
Adrien Soudais (Dartmouth College)20/11/2026 16:15
Magnetars are highly magnetized neutron stars whose persistent hard X-ray emission is thought to arise from resonant inverse Compton scattering of photons by relativistic particles in their magnetospheres. Unlike pulsar magnetospheres, radiation-rich magnetar magnetospheres remain largely unexplored with self-consistent kinetic simulations. Global Particle-in-Cell (PIC) simulations are an...
Aller à la page de la contribution -
Maïa Villemin (IPAG)20/11/2026 16:30
Recent observations of Sagittarius A* have revealed the presence of a hotspot orbiting close to the black hole during near-infrared and X-ray flares.
Aller à la page de la contribution
Magnetospheric eruptions have recently been proposed as a possible explanation for these flares. Using axisymmetric General Relativistic Particle-In-Cell (GRPIC) simulations, Figueiredo & al., 2026, identified quasi-periodic cycles associated... -
Gaia Bilosi (LUX)20/11/2026 16:45
Fast Radio Bursts (FRBs) are extremely bright millisecond-duration radio transients whose physical origin remains poorly understood. Among the leading progenitor candidates are magnetars: highly magnetized neutron stars capable of powering large-amplitude disturbances in their magnetospheres. In particular, starquakes can excite fast magnetosonic waves propagating across the background...
Aller à la page de la contribution -
Théo Francez (LUX - Observatoire de Paris - PSL)20/11/2026 16:49
Neutron star magnetospheres are the environments of magnetised and rapidly rotating neutron stars which often manisfest through the phenomenon of pulsar. From the electron Larmor radius to the radius of the neutron star, the tremendous scale separation has made simulations of such environments extremely challenging. While resistive force-free codes provide a good description of the...
Aller à la page de la contribution -
Léo Lam Kon Seng (LAPTh)20/11/2026 16:53
Pulsars are highly magnetized, fast-spinning neutron stars, among which millisecond pulsars (MSPs) form the oldest population. Pulsars are powerful particle accelerators, and thus efficient gamma-ray emitters, with some expected to reach the very-high energy (VHE, >100 GeV) scale. Nonetheless, VHE detections have, to date, been restricted to “normal”, young pulsars.
Aller à la page de la contribution
Unraveling the VHE... -
Alexandra Lorange20/11/2026 16:57
Millisecond pulsars are spun up during their accretion phase in a binary system. The exchange of angular momentum between the accretion disk and the star tends to align the spin and orbital angular momenta on a very short time scale compared to the accretion stage. This alignment can also be seen as the equality between two angles : the orbital inclination angle i, corresponding to the angle...
Aller à la page de la contribution -
Guillaume Voisin (LUTH, Observatoire de Paris, CNRS)20/11/2026 17:00
Choisissez le fuseau horaire
Le fuseau horaire de votre profil: