The discovery of high-energy cosmic neutrinos opened a new window of astroparticle physics. Revealing the sources is also relevant for solving the long-standing puzzle about the origin of cosmic rays. I will discuss theoretical implications of the latest results on high-energy neutrino observations, including associations of high-energy neutrinos with galaxies hosting supermassive black holes,...
Accretion flows around supermassive black holes can emit the high energy neutrino and may significantly contribute to the IceCube neutrinos. The global structure of the magnetized accretion flows potentially affect the neutrino SEDs, while it has not yet been studied. We, therefore, carry out the calculation of SEDs of high energy neutrinos by using three dimensional general relativistic...
Neutrinos play essential roles in cooling the interiors of massive stars and serve as potential signatures of their evolution towards the eventual core collapse and supernova explosion. The intense neutrino burst from the supernova itself may reveal details of the explosion mechanism and of the formation of a neutron star or black hole. In rare supernovae where high-energy neutrinos are...
The often-considered dark matter (DM) candidates, e.g., WIMP and ALP, are in tension with observations, which motivates new proposals for DM. The recently proposed féeton dark matter, a B-L gauge boson with a small mass and a feeble coupling to the standard sector constitutes a well-motivated dark matter model consistent with cosmology, Seesaw mechanism, and leptogenesis. This model predicts...
Relativistic outflows are efficient particle accelerators, and TeV-PeV photons provide an extremely effective probe of these systems. I will discuss the latest observational results related to Galactic systems with relativistic outflows and associated gamma-ray emission, including pulsar wind nebulae and microquasars, and large-scale emission associated to particles that have escaped from such...
LHAASO is a ground-based TeV-PeV gamma-ray instrument with an unprecedentedly high sensitivity at the ultrahigh-energy band (E>100 TeV). Measurements of UHE sources provide important clues to understanding long-sought origins of PeV cosmic rays or PeVatrons. I will introduce the recent progress of LHAASO's measurements on Galactic PeVatron candidates and pulsar wind nebulae, with paying...
Pulsar Wind Nebulae (PWNe) are the prototypical Galactic relativistic accelerators. They are the most promising astrophysical labs where high-energy astrophysical processes can be investigated in details. They are also among the best studied objects in the sky, at the forefront of observational and theoretical endeavors. I will briefly review the current status of our knowledge of these...
Surveys with ground-based Cerenkov telescopes (e.g., HESS, MAGIC, and VERITAS) and space-based gamma-ray detectors (e.g., Fermi, INTEGRAL, and AGILE) have discovered a new class of binary systems that emit luminous gamma-rays. Those binaries usually comprise a stellar-mass compact object in orbit with a massive star and emit broadband radiation with non-thermal spectra peaking beyond 1 MeV,...
With the breakthrough in PeV gamma-ray astronomy brought by the LHAASO experiment, the high-energy sky is getting richer than before. Lately, LHAASO Collaboration reported the observation of a gamma-ray diffuse emission with energy up to the PeV level from both the inner and outer Galactic plane. In these spectra, there is one bump that is hard to explain by the conventional cosmic-ray...
The existence of a “knee” at a few PeV in the cosmic-ray spectrum suggests the presence of Galactic PeV proton accelerators called “PeVatrons.” The search for PeVatrons has been significantly advanced lately, thanks to the launches and operation of very-high-energy gamma-ray and high-energy neutrino observatories. This talk will present the latest observations of a few candidate PeVatrons. We...
The microquasar system SS 433 provides a unique opportunity to study mildly relativistic collimated jets in our own Galaxy. While much is known about the nature of the precessing inner jets, the dynamics at large distances from the central binary system are poorly constrained. The abrupt reappearance of non-thermal x-ray synchrotron emission at around 25 parsecs either side of the core...
Cosmic ray acceleration up to PeV energies has been suggested to take place in massive and young stellar clusters. The formation of a strong termination shock driven by the collective action of stellar winds in a compact cluster offers a promising location where efficient particle acceleration might take place. The subsequent interactions of these particles with target gas result into hadronic...
Our Galaxy is filled with cosmic rays, but the origin of PeV cosmic rays have been unknown for a long time. Recently, LHAASO discovered mysterious sub-PeV gamma-ray sources without any obvious counterparts in other wavelengths, and origins of these gamma-ray sources are also unknown. In this talk, we propose that isolated stellar-mass black holes (IBHs) wandering in molecular clouds can be the...
The center of our Milky Way galaxy hosts a series of energetic outbursts, including the well-known Fermi and eROSITA bubbles, galactic center lobes, the inner 15-pc X-ray lobes. Are they long-lasting or fast evolving explosive events? What causes these structures? Are they PeVatrons related to ultra high energy gamma ray emissions from the central molecular zone and the Galactic center? The...
In this talk, I will report the observations of the TeV emission from the brightest-of-all-time GRB 221009A by the Large High Altitude Air Shower Observatory (LHAASO). I will also present our understanding of the TeV and multi-wavelength afterglow emission of this unusual GRB.
Extragalactic plasma jets are some of the few astrophysical environments able to confine ultra-high-energy cosmic rays, but whether they are capable of accelerating these particles is unknown. In this work, we revisit particle acceleration at relativistic magnetized shocks beyond the local uniform field approximation, by considering the global transverse structure of the jet. Using large...
Blazars are astrophysical systems hosting an accreting supermassive black hole with a relativistic jet pointed along our line of sight. These sources emit radiation ranging from radio to TeV bands. The synchrotron emission produced by the relativistic motion of electrons around the jet magnetic field explains the first hump of the dual-peaked spectral energy distribution (SED), peaking between...
Context. Composite galaxies, containing both a starburst and Seyfert component, may produce very-high-energy (VHE; > 100 GeV) γ-ray emission at vastly different spatial scales ranging from several Schwarzschild radii of a supermassive black hole (SMBH) to a dozen kiloparsecs. Some cosmic-ray sources, including cores of active galaxies, heads of kiloparsec-scale jets, and galactic superwinds,...
UHECRs are composed of intermediate-mass nuclei and have a composition evolution with energy that is roughly consistent with a Peters Cycle, such that the mean rigidity is less than 5 EV, even at relatively high energy. Deflections in the Galactic magnetic field are in general large, and identifying sources by angular correlations has been impossible so far. Nonetheless, a number of...
The origin of ultra-high-energy cosmic rays remains unknown owing to the lack of definitive observational evidence and the lack of a source class without major theoretical objections. The primary challenge for cluster accretion shocks—formed by accretion of gas beyond the virial radius of galaxy clusters—is the purported lack of sufficient magnetic field strength to scatter cosmic rays at the...
