Related papers: H.E.S.S. observations of massive stellar clusters
\textit{PeVatrons} are the extreme galactic accelerators capable of producing PeV particles. Recent observation of Large High Altitude Air Shower Observatory have detected UHE photons ($\geq$ 100 TeV) from 43 galactic sources. Detection of…
Galaxy clusters are the largest structures in Universe. They are very important as both cosmological probes and astrophysical laboratories. Several methods have been developed to detect galaxy clusters with different techniques (optical,…
The enormous velocities of the so called hypervelocity stars (HVSs) derive, likely, from close interactions with massive black holes, binary stars encounters or supernova explosions. In this paper, we investigate the origin of hypervelocity…
About 30 Galactic supernova remnants (SNRs) are thought to be physically associated with molecular clouds (MCs). These systems are prime \g-ray source candidates as the accelerated particles from shock fronts collide with the surrounding…
We study the stellar and wind properties of massive stars in the central cluster of the Galaxy. We use non-LTE atmosphere models including winds and line-blanketing to fit their H and K band spectra obtained with the 3D spectrograph SINFONI…
Massive stars blow powerful winds and eventually explode as supernovae. By doing so, they inject energy and momentum in the circumstellar medium, which is pushed away from the star and piles up to form a dense and expanding shell of gas.…
A large fraction of the recently discovered Galactic Very High Energy (VHE) source population remains unidentified to date. VHE gamma-ray emission traces high energy particles in these sources, but for example in case of hadronic processes…
Aims. Colliding wind binary systems have long been suspected to be high-energy (HE; 100 MeV < E < 100 GeV) {\gamma}-ray emitters. {\eta} Car is the most prominent member of this object class and is confirmed to emit phase-locked HE {\gamma}…
Supernova remnants (SNRs), star formation regions (SFRs), and pulsar wind nebulae (PWNe) are prime candidates for Galactic PeVatrons. The nonthermal high-energy (HE, $\varepsilon>100 \textrm{ MeV}$) and very high-energy (VHE,…
Nuclear star clusters are found at the centers of most galaxies. They are the densest stellar systems in the Universe, and thus have unique and interesting stellar dynamics. We review how common nuclear star clusters are in galaxies of…
We present evidence that some of the compact, luminous, young star clusters recently discovered through images taken with the Hubble Space Telescope (HST) have masses comparable to those of old Galactic globular clusters. The "super star…
The massive binary system Eta Carinae and the surrounding HII complex, the Carina Nebula, are potential particle acceleration sites from which very-high-energy (VHE; E > 100 GeV) \gamma-ray emission could be expected. This paper presents…
Massive stars play an important role in explaining the cosmic ray spectrum below the knee, possibly even up to the ankle, i.e. up to energies of 1e15 eV or 1e18.5 eV, respectively. In particular, Supernova Remnants are discussed as one of…
Since their discovery at radio wavelengths pulsars have been persistent targets for widespread multi-wave observations throughout optics, radio, X-rays, and high-energy gamma-rays. Observations with the EGRET gamma-ray telescope, on board…
In the last decade star clusters have been found in the centers of spiral galaxies across all Hubble types. We here present a spectroscopic study of the exceptionally bright (10^6 - 10^8 Lsun) but compact (Re ~ 5 pc) nuclear star clusters…
With a dynamical mass M_dyn ~ 1.3x10e5 M_sun and a lower limit M_cl>5x10e4 M_sun from star counts, Westerlund 1 is the most massive young open cluster known in the Galaxy and thus the perfect laboratory to study massive star evolution. We…
Super star clusters (SSCs), likely the progenitors of globular clusters, are one of the most extreme forms of star formation. Understanding how SSCs form is an observational challenge. Theoretical studies establish that, to form such…
Cluster of galaxies are the largest concentrations of visible mass in the Universe and therefore a fundamental topic of cosmology and astrophysics. Recent radio, EUV, and X-ray observations suggest that clusters contain large populations of…
Strongly lensed star clusters have recently been detected up to redshift $z\approx 10$ in galaxy cluster fields using the James Webb Space Telescope (JWST). When pairs of mirror images of such star clusters appear across the lensing…
Very massive stars (VMS) are defined as stars with an initial mass in excess of 100 Msun. Because of their short lifetime and the shape of the stellar mass function, they are rare objects. Only about twenty of them are known in the Galaxy…