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We discuss a specific population of galactic PeVatrons which may be the main source of the galactic cosmic-ray (CR) component well above PeV energies. Supernovae in compact clusters of massive stars are proposed as powerful sources of CRs,…
A long standing problem in high energy astrophysics is the nature of galactic accelerators of particles with energies above PeV. Such objects are sources of galactic cosmic rays and can produce PeV-regime photons observed by ground-based…
The H.E.S.S. experiment, an array of four Imaging Atmospheric Cherenkov Telescopes with high sensitivity and large field-of-view, has been used to search for emitters of very-high-energy (VHE, >100 GeV) gamma-rays along the Galactic plane,…
The central parsec of the Galaxy contains dozens of massive stars with a cumulative mass loss rate of ~ 10^{-3} solar masses per year. Shocks among these stellar winds produce the hot plasma that pervades the central part of the galaxy. We…
We report on Mopra observations toward the young massive star cluster RSGC 1, adjoined by, and possibly associated with the gamma-ray source HESS J1837-069. We measure the CO (J=1-0) distribution around the cluster and gamma-ray source, and…
In this paper we derive stellar parameters for the Wolf-Rayet star in the gamma Velorum binary system (WR11), from a detailed non-LTE model of its optical and infrared spectra. Compared to the study of Schaerer et al., the parameters of the…
Gamma-ray emission in the TeV range has been detected by HESS from two X-ray binaries: PSR B1259-63 and LS 5039. In both, the early-type star provides large numbers of target photons for pair-production with TeV gamma-rays. This results in…
The exclusive Galactic gamma-ray club has opened up to new members. Supernova remnants, pulsar wind nebulae, and massive binary systems hosting a compact object have recently joined the young pulsars as firmly established sources of gamma…
Globular clusters (GCs) are established emitters of high-energy (HE, 100 MeV<E<100 GeV) \gamma-ray radiation which could originate from the cumulative emission of the numerous millisecond pulsars (msPSRs) in the clusters' cores or from…
Observations with H.E.S.S. revealed a new source of very high-energy (VHE) gamma-rays above 100 GeV - HESS J1825-137 - extending mainly to the south of the energetic pulsar PSR B1823-13. A detailed spectral and morphological analysis of…
We report the Fermi Large Area Telescope (Fermi-LAT) detection of the gamma-ray emission towards the young massive star cluster RSGC 1. Using the latest source catalog and diffuse background models, we found that the diffuse gamma-ray…
Gamma-rays can be produced by the interaction of a relativistic jet and the matter of the stellar wind in the subclass of massive X-ray binaries known as "microquasars". The relativistic jet is ejected from the surroundings of the compact…
The most massive binary system Eta Carinae has been recently established as a gamma-ray source by the AGILE and Fermi-LAT detectors. The high energy spectrum of this gamma-ray source is very intriguing. It shows two clear components and a…
Most blazars are known to be hosted in giant elliptic galaxies, but their cluster environments have not been thoroughly investigated. Cluster environments may contain radiation fields of low-energy photons created by nearby galaxies and/or…
We report on the discovery of gamma-ray emission from several globular clusters (GCs), including Terzan 5, the second known gamma-ray GCs. By now, more than a dozen GCs are known to emit gamma-rays of energies above 100 MeV, thus enabling…
HESS J1825-137 is one of the most powerful and luminous TeV gamma-ray pulsar wind nebulae (PWN). To the south of HESS J1825-137, Fermi-LAT observation revealed a new region of GeV gamma-ray emission with three apparent peaks (termed here,…
The jets of microquasars with high-mass stellar companions are exposed to the dense matter field of the stellar wind. We present estimates of the gamma-ray emission expected from the jet-wind hadronic interaction and we discuss the…
Many of the recently discovered galactic very high-energy (VHE) gamma-ray sources are associated with Pulsar Wind Nebulae, which is the most populous Galactic source category at TeV energies. The extended synchrotron nebulae of these…
The recent completion and operation of the High Energy Stereoscopic System, an array of ground based imaging Cherenkov telescopes, has provided a survey with unprecedented sensitivity of the inner part of the Galaxy and revealed a new…
We report the detection of high-energy gamma-ray signal towards the young star-forming region, W40. Using 10-year Pass 8 data from the Fermi Large Area Telescope (Fermi-LAT), we extracted an extended gamma-ray excess region with a…