Related papers: Cygnus X-3 as semi-hidden PeVatron

We calculated for the nearest active galactic nucleus (AGN), Centaurus A (Cen A), the flux of high energy cosmic rays and of accompanying secondary photons and neutrinos expected from hadronic interactions in the source. We used as two…

Current generation of ground based gamma-ray telescopes observed dozens of sources of photons above 100 TeV. Supernova remnants, pulsar wind nebulae, young stellar clusters and superbubbles are considered as possible sites of PeV-regime…

Super-Eddington accretion onto stellar-mass compact objects powers fast outflows in ultra-luminous X-ray sources (ULXs). Such outflows, which can reach mildly relativistic velocities, are often observed forming bubble structures. Wind…

Recent data on Galactic cosmic-ray (CR) leptons and hadrons gave rise to two exciting problems: on the lepton side, the origin of the rise of the CR positron fraction e+/(e- + e+) at ~10 - 300 GeV of energy; on the hadron side, the nature…

Cosmic rays (CRs) are thought to be accelerated in SNRs. The most favorable situation for proving that the main, hadronic CR component is accelerated there is when CRs interact with dense gases, such as molecular clouds (MC) which surround…

There has been a recent suggestion that Cyg X-3 contains a black hole (BH) of mass ~17 solar mass. This interpretation is closely linked to a previous claim that Cyg X-3 contains a Wolf-Rayet star of mass ~ 10 solar mass. The latter…

Recent observations of high-energy neutrinos from active galactic nuclei (AGN), NGC 1068 and TXS 0506+056, suggest that cosmic rays (CRs) are accelerated in the vicinity of the central supermassive black hole and high-energy protons and…

The mysterious very high energy gamma-ray source, TeV J2032+4130, is coincident with the powerful Cygnus OB2 stellar association, though a physical association between the two remains uncertain. It is possible that the detected very high…

The active galactic nuclei (AGNs) are widely believed to be one of the promising acceleration sites of ultrahigh-energy cosmic rays (CRs). Essentially, AGNs are powered by the gravitational energy of matter falling to supermassive black…

Recent accurate measurements of cosmic-ray (CR) protons and nuclei by ATIC-2, CREAM, and PAMELA reveal: a) unexpected spectral hardening in the spectra of CR species above a few hundred GeV per nucleon, b) a harder spectrum of He compared…

We investigate neutrino emission from gamma-ray bursts (GRBs) under alternative scenarios for prompt emission (the photospheric and synchrotron self-Compton scenarios) rather than the classical optically thin synchrotron scenario. In the…

We have used observations of Cygnus X-1 from the Compton Gamma-Ray Observatory (CGRO) and BeppoSAX to study the variation in the MeV gamma-ray emission between the hard and soft spectral states, using spectra that cover the energy range 20…

We present orbital-phase resolved I and K-band spectroscopy of Cygnus X-3. All spectra show emission lines characteristic of Wolf-Rayet stars of the WN subclass. On time scales longer than about one day, the line strengths show large…

Cygnus X-3 is a microquasar consisting of an accreting compact object orbiting around a Wolf-Rayet star. It has been detected at radio frequencies and up to high-energy gamma rays (above 100 MeV). However, many models also predict a very…

Motivated by recent IceCube observations we re-examine the idea that microquasars are high energy neutrino emitters. By stretching to the maximum the parameters of the Fermi engine we show that the nearby high-mass X-ray binary LS 5039…

We aim to explain in a unified way the experimental data on ultrahigh energy cosmic rays (UHECR) and neutrinos, using a single source class and obeying limits on the extragalactic diffuse gamma-ray background (EGRB). If UHECRs only interact…

Recent observations show that hypernovae may deposit some fraction of their kinetic energy in mildly relativistic ejecta. In the dissipation process of such ejecta in a stellar wind, cosmic ray protons can be accelerated up to $\sim…

Cosmic-ray acceleration has been a long-standing mystery and despite more than a century of study, we still do not have a complete census of acceleration mechanisms. The collision of strong stellar winds in massive binary systems creates…

The AMS Collaboration has recently released data on cosmic ray (CR) leptons and hadrons that can shed light on two exciting problems in CR physics: on one side, the origin of the rise of the CR positron fraction above ~10 GeV of energy, on…

High-energy neutrinos and photons are complementary messengers, probing violent astrophysical processes and structural evolution of the Universe. X-ray and neutrino observations jointly constrain conditions in active galactic nuclei (AGN)…