Non-thermal electromagnetic radiation up to PeV gamma-rays from pulsar wind nebulae is powered by relativistic electron-positron plasma supplied by a central pulsar. The origin of the radio-emitting particles, however, remains unresolved because of their large number compared with that expected from pair cascades in the pulsar magnetosphere. A stochastic acceleration model has been proposed in...
Spider pulsars are compact binary systems consisting of a millisecond pulsar and a low-mass companion. The relativistic pulsar wind interacts with the companion outflow, forming an intrabinary shock (IBS) associated with particle acceleration and orbitally modulated X-ray emission. These systems may also contribute to high-energy cosmic-ray positrons and are thought to harbor some of the most...
Microquasars are radio-emitting X-ray binaries accompanied by relativistic jets. They are established sources of 100~TeV gamma rays and are considered promising candidates for cosmic-ray acceleration. Motivated by recent detections of $\sim 100~$TeV photons from Cygnus~X-1 and $\sim~$PeV photons from Cygnus~X-3 by the Large High Altitude Air Shower Observatory (LHAASO), we employ the...
Microquasars, compact binary systems with an accreting stellar-mass black hole or neutron star, are promising candidates for high-energy particle acceleration. Recently, the LHAASO collaboration reported on the detection of >100 TeV ฮณ-ray emission from five microquasars, suggesting that these sources are efficient particle accelerators. In microquasars, high-energy ฮณ-rays can be produced in...
The Sun is a high-energy emission source due to cosmic rays interacting with the solar atmosphere, but the physics of these emissions are still poorly understood. Fermi and HAWC solar gamma-ray observations have shown that the emission from GeV to TeV must be strongly affected by solar magnetic fields. I will discuss the progress in solar gamma-ray observations, and what they could tell us...
The origin of diffuse neutrinos and $\gamma-$rays is uncertain, and galaxy clusters hosting AGN and starburst galaxies are the most probable sources of these cosmic messengers. In this work, we investigate the diffuse $\gamma-$ray and neutrino emission from the Virgo, Perseus, and Coma clusters using a detailed numerical method, combining MHD simulations with Monte Carlo methods. The MHD...
Observations by the High-Altitude Water Cherenkov (HAWC) Observatory have revealed gamma-ray emission from the Galactic Center (GC) region extending beyond 100 TeV with an unbroken power law, indicating the presence of a powerful particle accelerator. If this emission is of hadronic origin, a corresponding flux of high-energy neutrinos is expected. We present an update on HAWC analyses of the...
The Galactic Plane has been established as a source of high-energy neutrino emission with a significance beyond 5 sigma using Galactic diffuse neutrino emission models. We discuss the results of a model-independent measurement of the Galactic emission with 10 years of IceCube cascade data, which provides confidence intervals on the neutrino flux and the spectral index in different regions of...
IceCube has detected neutrinos originating from the Galactic plane at 5.7ฯ suggesting the possible existence of Galactic neutrino sources. Additionally, gamma-ray observatories such as HAWC, LHAASO, and H.E.S.S. have detected Galactic gamma-ray sources with photon emission exceeding 100 TeV. If produced in hadronic interactions, these gamma-ray sources hint at the existence of Galactic...
Latest measurements of spectra of different cosmic ray elements at TeVโPeV energies, as well as the all-particle spectrum and mean logarithmic mass, provide a wealth of new information for models of Galactic cosmic ray acceleration and propagation. At the same time, a consistent interpretation of all available datasets remains challenging, and different theoretical frameworks are often not...
Title:
Explaining the Measured Cosmic-Ray Nuclei Spectra with a Dual Source-category Model
Abstract:
Preliminary results shown by the CALET (Calorimetric Electron Telescope) collaboration at the ICRC2025 conference [P. Brogi et al. POS(ICRC2025)019] indicate a break in the proton-helium ratio in the TeV energy range. Assuming cosmic-ray acceleration and propagation mechanisms to be...
Within the disk of the Milky Way, GeV-range cosmic rays (CRs) are known to be energetically comparable to other components in the interstellar medium, while TeV-PeV-range CRs are very minor. However, the situation should be different after such CRs have escaped the disk and propagate to the scales of the much more tenuous circumgalactic medium (CGM) and/or intergalactic medium (IGM). Depending...
The First LHAASO Catalogue of Gamma-ray Sources (1LHAASO) lists 90 sources, 43 of which show ultra-high-energy (UHE) emission extending beyond 100 TeV, raising pressing questions about the identity of the underlying PeVatrons. A multiwavelength characterization of these sources is essential to constrain the particle acceleration mechanisms at work. We present a systematic search for...
Superluminous supernovae (SLSNe) are rare transients that are $\sim 10 - 100$ times more luminous than ordinary stellar explosions, reaching peak optical luminosities $\sim 10^{44} - 10^{45}$ erg s$^{-1}$. The energy source powering SLSNe remains uncertain. In this talk, I will discuss the multi-wavelength and multi-messenger signatures from the scenario in which SLSNe are powered by a newly...
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...
HiZ-GUNDAM is a candidate for JAXAโs competitive medium-class mission program, with its concept approved by ISAS/JAXA in 2018. This proposed satellite aims to play a leading role in time-domain astronomy in the 2030s by pursuing two primary scientific goals: (1) probing the early universe through the detection of high-redshift gamma-ray bursts (GRBs) and (2) enabling the rapid identification...
The High-z Gamma-ray Bursts for Unraveling the Dark Ages Mission (HiZ-GUNDAM) is dedicated to time-domain and multi-messenger astronomy, focusing on the observation of high-energy astronomical transient events, such as gamma-ray bursts (GRBs). HiZ-GUNDAM is designed to deliver rapid alerts of high-redshift GRBs through the use of its wide-field X-ray monitor, the Exploration of Ancient GRBs...
The MeV gamma-ray sky remains the least explored window in high-energy astrophysics, therefore refered to as the โMeV gapโ, with only 32 steady sources and 31 GRBs detected by COMPTEL. With COSI launching soon and other future MeV missions, it is now essential to provide quantitative predictions of what these missions will be detectable to strengthen MeV gamma-ray science cases in the...
The process of hierarchical structure formation drives powerful shocks through the merger of massive galaxy clusters and the continuous accretion of mass onto cosmic filaments and galaxy clusters. The role of these shocks in the acceleration of GeV to TeV protons and their distribution in the intra-cluster and warm-hot intergalactic medium (ICM and WHIM) is so far not well understood.
I will...
Astrophysical shocks are considered to be one of the main sources of cosmic rays in the universe. Long-term observations of gamma-ray burst (GRB) afterglows, the recent detection of >100 TeV gamma-rays from microquasars, and the discovery of fast blue optical transients (FBOTs) motivate us to investigate transrelativistic shocks, which are underexplored, in terms of microphysics, compared to...
Relativistic viscous hydrodynamics is the workhorse for modeling the quarkโgluon plasma (QGP) created in high-energy heavy-ion collisions and could play an equally crucial role in understanding hot, dense matter in neutron stars and their mergers. In contrast to commonly used IsraelโStewartโtype (IS) theories, which can exhibit acausal behavior, we consider the BemficaโDisconziโNoronhaโKovtun...
Understanding the origin and evolution of cosmic rays (CRs) across cosmic time is a key problem in high-energy astrophysics and cosmology. Recent studies suggest that the earliest CRs may have been produced at collisionless shocks driven by the supernova explosions of the first stars at z ~ 20. In this work, we explore a possible scenario for CR production across cosmic epochs, connecting...
SN 1006 is a historic supernova remnant exhibiting a bilateral shape, with non-thermal X-ray and TeV emission more prominent in two polar cap regions aligned with the ambient magnetic field. Further, a large-scale ambient density gradient is observed to be roughly perpendicular to the magnetic axis. We model the multi-wavelength spectral and spatial properties of each quadrant in SN 1006 using...
Several theoretical models explain the neutrino flux from Active Galactic Nuclei, such as NGC 1068, as originating from cosmic-ray interactions in the corona. If cosmic rays are destroyed in such dense environments, a natural question arises: where do the observed Ultra-High-Energy Cosmic Rays (UHECR) originate? In this contribution, we explore the possibility that UHECRs originate in...
On February 13, 2023, at 01:16:47 UTC, the KM3NeT neutrino telescope detected KM3-230213A, an ultra-high-energy neutrino event without an identified electromagnetic counterpart. Its unknown origin motivates a multi-energy follow-up to probe astrophysical scenarios capable of producing neutrinos across a broad energy range. We present a coordinated analysis with IceCube spanning MeV to sub-TeV...
On February 13, 2023, the KM3NeT collaboration observed KM3-230213A, the mostย energetic eventย observed to date, with an estimated energy of ~200 PeV. KM3NeT is a next-generation underwater neutrino telescope under construction in the Mediterranean Sea, which will eventually instrument a cubic kilometer of seawater. Understanding the origin of this event could shed light on the most extreme...
The highest-energy cosmic neutrino detected by the ARCA detector of KM3NeT has reignited the quest to pinpoint the sources of ultrahigh-energy cosmic rays (UHECRs; $E\gtrsim 0.1$ EeV). By uncovering the associated multimessenger signals, we investigate the origin of the 220 PeV $\nu_\mu$ event KM3-230213A from an unknown transient that accelerated cosmic rays to $\sim 10$ EeV. Unlike an...
An extremely energetic muon has been recently detected by the Cubic Kilometre Neutrino Telescope (KM3NeT), indicating the observation of a neutrino. Radio blazar PMN J0606โ0724, not detected in gamma rays, is located within the reported error region of the neutrino arrival direction, and was flaring at the time of the event. Here we demonstrate that the neutrino could be produced in a...
Data of the James Webb Space Telescope (JWST) has revealed a surprisingly large number of active galactic nuclei (AGN) populating the universe at large redshifts (5 < z < 10). The nature of these objects is not tightly constrained observationally yet. We discuss the cosmogenic neutrino flux arising from these sources if they are capable of accelerating cosmic ray protons to energies up to...
Modern astronomy relies on the combined observation of the Universe through multiple messengers, including electromagnetic radiation, cosmic rays, gravitational waves, and neutrinos. Time correlation across these channels is essential for the discovery and characterisation of transient astrophysical sources, as well as for probing the mechanisms driving the most extreme cosmic phenomena. These...
Since 2016, the IceCube Neutrino Observatory has operated a real-time alert system to identify high-energy neutrino events and promptly notify the astronomical community for electromagnetic and gravitational-wave follow-up. A major success of the program was the detection, a year later, of a high-energy neutrino from the blazar TXS 0506+056, demonstrating the power of rapid multi-messenger...
The correlation between gamma-ray and neutrino emissions due to hadronic processes in astrophysical sources is of special interest for multi-messenger astronomy as both channels of detection offer complementary information about the sources studied.
The ANTARES neutrino telescope was a 0.01 $km^{3}$ volume detector located at the bottom of the Mediterranean Sea. It operated from 2007...
Fast radio bursts (FRBs) are an extremely luminous class of very short (millisecond-duration) bursts of radio waves, which are mostly extragalactic. Despite radio telescopes such as the Canadian Hydrogen Intensity Mapping Experiment (CHIME) detecting thousands of FRBs, their origins and production mechanisms are largely unknown. Their only known source association is with an X-ray flare from...
Optical transients with timescales of months, such as supernovae (SNe) and tidal disruption events (TDEs), are candidate sources of high-energy neutrinos. Multiple neutrino detections from the same direction on a timescale of about a month provide a unique opportunity to identify such optical counterparts in the nearby Universe. In this work, we conduct an archival search for the optical...
A wide variety of transient phenomena, including gamma-ray bursts, supernovae, and novae, are expected to emit GeV neutrinos. Detecting these neutrinos provides unique insights into their emission mechanisms and particle acceleration processes. IceCube Upgrade, the densest infill array in IceCube Neutrino Observatory, features newly developed multi-PMT optical modules with close spacing. It...
The Einstein Probe mission is rapidly increasing the number of known fast X-ray transients (FXTs), opening a new window on short-lived high-energy phenomena in the Universe. A major open question is whether these FXTs represent the softer and lower-luminosity extension of the classical long gamma-ray burst (GRB) population, or whether they include events belonging to a physically distinct...
To reveal the nature of high-energy, gamma-ray sources and identify the associated accelerator and production mechanisms, we need detailed models capable of reproducing observed energy spectra and morphologies. To produce these gamma-ray models in a hadronic scenario, we need cosmic-ray and ISM distributions in 3D, as the gamma-ray morphology is sensitive to the relative distances between the...
Massive stars are intriguing objects and key players in the cosmic cycle, yet they not totally understood, especially their fate. They, in fact, distinguish themselves from lower mass stars by the events that can take place at their death. While the majority of stars will fade away as white dwarfs, massive stars with an initial mass $\geq 8\,M_\odot$ at the end of their evolution form a...
We present an improved parametric model for neutrino emission from core-collapse supernovae that directly connects neutrino luminosity and average energy to stellar properties during the emission. Our model incorporates two critical physical processes: convection within the proto-neutron star (PNS) and the evolving dynamics of neutrinosphere radii during the early emission phase. Crucially,...
In recent years, there are some reported supernovae whose observational time and direction are close to high-energy neutrino events detected by IceCube. High-energy neutrinos from supernovae are theoretically supported by a shock and circumstellar medium (CSM) interaction scenario. We focused on one of such synchronized observations, SN 2023uqf โa Type Ibn supernovaโ, that was reported to be...
The origins of the cosmic neutrino background (CNB) and the cosmic gamma-ray background (CGB) remain uncertain. Accretion disk winds driven by active galactic nuclei (AGNs) have been proposed as possible contributors, but the background contribution they are predicted to make depends sensitively on poorly constrained wind energetics and ambient densities. In this contribution, I will revisit...
We present a generalized neutrino luminosity function for protons accelerated in the X-ray coronae of supermassive black holes in Seyfert-like galaxies. A major uncertainty in assessing the diffuse neutrino contribution of these systems is the underlying particle acceleration physics. We address this using a theoretical acceleration framework informed by plasma kinetic simulations, enabling a...
It has been shown that the turbulence acceleration in AGN coronae can account for 1-10 TeV neutrinos from some AGNs, such as the Seyfert galaxy NGC 1068. Based on this, there are attempts to explain the diffuse neutrinos observed by IceCube with the accumulated contribution from a population of AGNs, but it is found that the maximum neutrino energy is less than tens of TeV and, as a...
Blazars, a subclass of jetted active galactic nuclei, provide exceptional laboratories for astrophysical particle acceleration processes. These extreme environments have proven difficult to model in their entirety, even with multiwavelength datasets spanning from radio waves to gamma-rays. One major point of contention is the particle composition of the jet, with the main contenders being...
Recent IceCube measurements have identified the central regions of active galactic nuclei (AGN) as promising sites for cosmic-ray acceleration, largely through correlation studies with X-ray bright sources. Since X-ray emission is typically dominated by the AGN over the host galaxy, it serves as a robust proxy of the central activity correlated with the expected neutrino flux. Previous IceCube...
Radio flares have been proposed as possible signatures of astrophysical neutrino production. In TXS 0506+056, the 2017 IceCube-170922A /$gamma$-ray flare was followed by a GHz radio maximum roughly 2โ3 years later. We investigate whether this delayed radio flare can be explained by the same compact region that produced the neutrinos and $gamma$-rays, as it expands downstream and becomes less...
Little Red Dots (LRDs) are enigmatic, compact, red galaxies at high redshift, z โผ 4โ7, discovered by the James Webb Space Telescope. Broad emission lines in the absence of X-ray and radio counterparts suggest that they host accreting supermassive black holes embedded in dense gaseous envelopes. This black-hole-envelope configuration facilitates efficient photohadronic interactions and neutrino...
