The Fermi Large Area Telescope (LAT) has recently detected a population of globular clusters (GCs) in high-energy (HE) gamma-rays. Their spectral properties and energetics are consistent with cumulative emission from a population of millisecond pulsars (MSPs) hosted by these clusters. For example, the HE spectra exhibit fairly hard power-law indices and cutoffs around a few GeV, typical of pulsed spectra measured for the gamma-ray pulsar population. The energetics may be used to constrain the number of visible MSPs in the cluster (N_vis), assuming canonical values for the average gamma-ray efficiency and spin-down power. This interpretation is indeed strengthened by the fact that the first gamma-ray MSP has now been identified in the GC NGC 6624, and this MSP is responsible for almost all of the HE emission from this cluster. On the other hand, it has been argued that the MSPs are also sources of relativistic leptons which may be reaccelerated in shocks originating in collisions of stellar winds in the cluster core, and may upscatter bright starlight and cosmic microwave background photons to very high energies. Therefore, this unpulsed component may give an independent constraint on the total number of MSPs (N_tot) hosted in the GC, for a given cluster magnetic field B and diffusion coefficient k_0. Lastly, the transport properties of the energetic leptons may be further constrained using multiwavelength data, e.g., to infer the radial dependence of k_0 and B. We present results on our modeling of the pulsed and unpulsed gamma-ray fluxes from the GC Terzan 5.
We report the discovery of gamma-ray emission from the Galactic globular cluster Terzan 5 using data taken with the Fermi Gamma-ray Space Telescope, from 2008 August 8 to 2010 January 1. Terzan 5 is clearly detected in the 0.5-20 GeV band by Fermi at ~27σlevel. This makes Terzan 5 as the second gamma-ray emitting globular cluster seen by Fermi after 47 Tuc. The energy spectrum of Terzan 5 is best represented by an exponential cutoff power-law model, with a photon index of ~1.9 and a cutoff energy at ~3.8 GeV. By comparing to 47 Tuc, we suggest that the observed gamma-ray emission is associated…
Globular clusters are old stellar systems which exhibit very-high stellar densities in their cores. The globular cluster Terzan 5 is characterized by a high stellar encounter rate and hosts the largest detected population of millisecond pulsars. It also features bright GeV gamma-ray emission and extended X-ray radiation. However, no globular clusters have been detected in very-high-energy gamma rays (VHE, E> 100 GeV) so far. In order to investigate this possibility Terzan 5 has been observed with the H.E.S.S. telescope array in this energy band. The discovery of a source of VHE gamma rays from…
Globular cluster are believed to boost the rate of compact binary mergers which may launch a certain type of cosmological gamma-ray bursts (GRBs). Therefore globular clusters appear to be potential sites to search for remnants of such GRBs. The very-high-energy (VHE) gamma-ray source HESS J1747-248 recently discovered in the direction of the Galactic globular cluster Terzan 5 is investigated for being a GRB remnant. Signatures created by the ultra-relativistic outflow, the sub-relativistic ejecta and the ionizing radiation of a short GRB are estimated for an expected age of such a remnant of t…
Diffuse X-ray emission has recently been detected from the globular cluster (GC) Terzan 5, extending out to ~2.5' from the cluster centre. This emission may arise from synchrotron radiation (SR) by energetic leptons being injected into the cluster by the resident millisecond pulsar (MSP) population that interact with the cluster field. These leptons may also be reaccelerated in shocks created by collisions of pulsar winds, and may interact with bright starlight and cosmic microwave background (CMB) photons, yielding gamma rays at very high energies (VHE) through the inverse Compton (IC) proces…
Recently, diffuse and extended sources in TeV gamma-rays as well as in X-rays have been detected in the direction of the Galactic globular cluster (GC) Terzan 5. Remarkably, this is among the brightest GCs detected in the GeV regime. The nature of both the TeV and the diffuse X-ray signal from Terzan 5 is not settled yet. These emissions most likely indicate the presence of several non-thermal radiation processes in addition to these giving rise to the GeV signal. The aim of this work is to search for diffuse X-ray emission from the GeV detected GCs M 62, NGC 6388, NGC 6541, M 28, M 80 and NGC…
Terzan 5 is a Galactic globular cluster exhibiting prominent X-ray and gamma-ray emission. Following the discovery of extended X- ray emission in this object, we explore here archival data at several wavelengths for other unexpected emission features in the vicinity of this globular cluster. Radio data from the Effelsberg 100 metre telescope show several extended structures near Terzan 5, albeit with large uncertainties in the flux estimates and no reliable radio spectral index. In particular, a radio source extending from the location of Terzan 5 to the north-west could result from long-term …
The H.E.S.S. very-high-energy (VHE, E > 0.1 TeV) gamma-ray telescope system has discovered a new source, HESS J1747-248. The measured integral flux is (1.2 +/- 0.3) \times 10^-12 cm-2 s-1 above 440 GeV for a power-law photon spectral index of 2.5 +/- 0.3 stat +/- 0.2 sys. The VHE gamma-ray source is located in the close vicinity of the Galactic globular cluster Terzan 5 and extends beyond the H.E.S.S. point spread function (0.07 degree). The probability of a chance coincidence with Terzan 5 and an unrelated VHE source is quite low (~ 10^-4). With the largest population of identified millisecon…
Globular clusters (GCs) are established emitters of high-energy (HE, 100 MeV<E<100 GeV) γ-ray radiation which could originate from the cumulative emission of the numerous millisecond pulsars (msPSRs) in the clusters' cores or from inverse Compton (IC) scattering of relativistic leptons accelerated in the GC environment. GCs could also constitute a new class of sources in the very-high-energy (VHE, E>100 GeV) γ-ray regime, judging from the recent detection of emission from the direction of Terzan 5 with the H.E.S.S. telescope array. To search for VHE γ-ray sources associated with other GCs, and…
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 us to carry out the first detailed correlation study with several cluster properties. We found strong correlations between the observed gamma-ray luminosities and four cluster parameters: stellar encounter rate, metallicity [Fe/H], and energy densities of the soft photons at the cluster locations. These "fundamental planes" of gamma-ray GCs put an intimate re…
Globular clusters are large collections of old stars that are orbiting the core of a galaxy. Our Milky Way Galaxy has about 160 known clusters, with perhaps more to be discovered. We first accumulated the necessary parameters for 16 clusters and ran a numerical model that predicts the inverse Compton gamma-ray flux expected from each cluster. We also reanalysed data from 16 clusters observed by the H.E.S.S. very-high-energy (> 100 GeV) gamma-ray telescopes. We confirmed the detection of Terzan 5 and found flux upper limits for the remaining 15 sources that were consistent with published result…
The recent Fermi detection of the globular cluster (GC) 47 Tucanae highlighted the importance of modeling collective gamma-ray emission of millisecond pulsars (MSPs) in GCs. Steady flux from such populations is also expected in the very high energy (VHE) domain covered by ground-based Cherenkov telescopes. We present pulsed curvature radiation (CR) as well as unpulsed inverse Compton (IC) calculations for an ensemble of MSPs in the GCs 47 Tucanae and Terzan 5. We demonstrate that the CR from these GCs should be easily detectable for Fermi, while constraints on the total number of MSPs and the …
This paper discusses the relation between the study of the fluxes of cosmic rays, gamma rays and neutrinos, and the connection of these observations with the newly born field of gravitational wave astronomy.
This white paper describes the contributions of the VERITAS gamma-ray telescope array to the CF6-A subgroup of the 'Cosmic Frontier' working group, part of the Snowmass Community Summer Study 2013.
We will review the main channels of gamma ray emission due to the acceleration and propagation of cosmic rays, discussing the cases of both galactic and extra-galactic cosmic rays and their connection with gamma rays observations.
The PeV gamma ray background produced in the interactions of ultra high energy cosmic rays with the ambient matter and radiations during their propagation in the Milky Way has been calculated in this paper. If the primary ultra high energy cosmic rays are produced from Galactic point sources then those point sources are also emitting PeV gamma rays. We discuss that the detection of galactocentric PeV gamma rays in the future would be a signature of the presence of EeV cosmic accelerators in the Milky Way.
Monochromatic gamma-rays are thought to be the smoking gun signal for identifying the dark matter annihilation. However, the flux of monochromatic gamma-rays is usually suppressed by the virtual quantum effects since dark matter should be neutral and does not couple with gamma-rays directly. In the work we study the detection strategy of the monochromatic gamma-rays in a future space-based detector. The monochromatic gamma-ray flux is calculated by assuming supersymmetric neutralino as a typical dark matter candidate. We discuss both the detection focusing on the Galactic center and in a scan …
It is well known that the diffuse gamma-rays are produced by the collisions between the galactic cosmic rays with the stellar matter (Hayakawa-Morrison Hypothesis). In this paper the author tries to estimate the contribution of star flares in the low energy component of the diffuse component of the galactic gamma-rays. It is expected that high energy part of the disuse component of the galactic gamma-rays reflects the power spectrum of galactic cosmic rays with gamma= -2.75 (in differential). In the galactic disk and bulge, there are more than 100 billion stars. They might often make flare and…
We present results from an emission code that assumes millisecond pulsars (MSPs) to be sources of relativistic particles in globular clusters (GCs) and models the resulting spectral energy distribution (SED) of Galactic GCs due to these particle's interaction with the cluster magnetic and soft-photon fields. We solve a transport equation for leptons and calculate inverse Compton (IC) and synchrotron radiation (SR) to make predictions for the flux expected from Galactic GCs. We perform a parameter study and also constrain model parameters for three GCs using gamma-ray and X-ray data. We next st…
In over two years of operation Fermi-LAT has revolutionized our knowledge of the gamma-ray sky. Interstellar gamma rays are part of this new era and allow unprecedented tests for models of cosmic rays in the Galaxy. The extension to lower energies with INTEGRAL/SPI data is also evolving. The global multiwavelength luminosity of the Milky Way has been derived, with implications for the Galactic energy balance and the radio-FIR correlation.
We show that a collisionless shock necessarily forms during the shock breakout of a supernova (SN) surrounded by an optically thick wind. An intense non-thermal flash of <~ MeV gamma rays, hard X-rays and multi-TeV neutrinos is produced simultaneously with and following the soft X-ray breakout emission, carrying similar or larger energy than the soft emission. The non-thermal flash is detectable by current X-ray telescopes and may be detectable out to 10's of Mpc by km-scale neutrino telescopes.
The upper limit on the flux of ultra high energy neutrinos from gamma-ray bursts (GRBs) that was reported recently by the IceCube collaboration contradicts predictions based on the Fireball model of GRBs, but does not exclude GRBs as a main source of ultra-high energy cosmic rays.
Combined data from gamma-ray telescopes and cosmic-ray detectors have produced some new surprising insights regarding intergalactic and galactic magnetic fields, as well as extragalactic background light. We review some recent advances, including a theory explaining the hard spectra of distant blazars and the measurements of intergalactic magnetic fields based on the spectra of distant sources. Furthermore, we discuss the possible contribution of transient galactic sources, such as past gamma-ray bursts and hypernova explosions in the Milky Way, to the observed flux of ultrahigh-energy cosmic-…
In this contribution we model the non-thermal emission (from radio to gamma-rays) produced in the compact (and recently detected) colliding wind region in the multiple stellar system Cyg OB2 #5. We focus our study on the detectability of the produced gamma-rays.
Pulsars are known to be efficient accelerators that produce copious amounts of relativistic particles and inject them into the Galactic medium. The radiation emitted by such a pulsar wind can be seen from radio through gamma-rays as a pulsar-wind nebula (PWN). Here we overview and summarize recent progress in X-ray and TeV observations of PWNe.
The High-Altitude Water Cherenkov Observatory, or HAWC, is carrying out an unbiased survey of cosmic rays and gamma rays from the Northern Hemisphere between 100 GeV and 100 TeV. HAWC is currently the only high-uptime wide-field TeV observatory in operation, and has a robust program to search for flares and other transient sources of gamma rays. The detector is also well suited to observe spatially extended regions of gamma-ray emission and cosmic-ray anisotropy. HAWC recently concluded its first year of data taking with the complete detector. The results include not only observations of many …
The microquasar Cygnus X-3 was detected at high energies by the gamma-ray space telescopes AGILE and Fermi. The gamma-ray emission is transient, modulated with the orbital period and seems related to major radio flares, i.e. to the relativistic jet. The GeV gamma-ray flux can be substantially attenuated by internal absorption with the ambient X-rays. In this study, we examine quantitatively the effect of pair production in Cygnus X-3 and put constraints on the location of the gamma-ray source. Cygnus X-3 exhibits complex temporal and spectral patterns in X-rays. During gamma-ray flares, the X-…
The number of plausible associations of extended VHE (TeV) sources with pulsars has been steadily growing, suggesting that many of these sources are pulsar wind nebulae (PWNe). Here we overview the recent progress in X-ray and TeV observations of PWNe and summarize their properties.
The cores of Arp 220, the closest ultra-luminous infrared starburst galaxy, provide an opportunity to study interactions of cosmic rays under extreme conditions. In this paper, we model the populations of cosmic rays produced by supernovae in the central molecular zones of both starburst nuclei. We find that ~65 - 100% of cosmic rays are absorbed in these regions due to their huge molecular gas contents, and thus, the nuclei of Arp 220 nearly complete proton calorimeters. As the cosmic ray protons collide with the interstellar medium, they produce secondary electrons that are also contained wi…
The $γ$-ray emission observed in several classes of Galactic and extragalactic astrophysical sources appears to be linked to accreting black holes and rotational powered neutron stars. These systems are prodigious cosmic accelerators, and are also potential sources of the UHE cosmic rays detected by several experiments and VHE neutrinos. We review a recent progress in our understanding of these objects, and demonstrate how recent and future observations can be employed to probe the conditions in the sources.
Very high-energy gamma-ray measurements of distant blazars can be well explained by secondary gamma rays emitted by cascades induced by ultra-high-energy cosmic rays. The secondary gamma rays will enable one to detect a large number of blazars with future ground based gamma-ray telescopes such as Cherenkov Telescope Array (CTA). We show that the secondary emission process will allow CTA to detect 100, 130, 150, 87, and 8 blazars above 30 GeV, 100 GeV, 300 GeV, 1 TeV, and 10 TeV, respectively, up to $z\sim8$ assuming the intergalactic magnetic field (IGMF) strength $B=10^{-17}$ G and an unbiase…
Recent Fermi and VERITAS observations of the prototypical Type Ia supernova remnant (SNR) Tycho have discovered gamma-rays with energies E in the range from ~0.4 GeV to 10 TeV. Crucial for the theory of Galactic cosmic-ray origin is whether the gamma-rays from SNRs are produced by accelerated hadrons (protons and ions), or by relativistic electrons. Here we show that the broadband radiation spectrum of Tycho can be explained within the framework of a two-zone leptonic model, which is likely to apply to every SNR. A model with hadrons can also fit the radiation spectrum. The hadronic origin of …
Gamma-ray bursts (GRBs) are the most violent explosions in the universe, seen primarily as bright, short flashes of gamma-rays. Long GRBs are most likely associated with the violent death of a very massive star. They are thus believed to originate within regions of recent or ongoing star formation with various bright, young stars, for instance, OB associations. GRBs have been detected in gamma-rays by satellite-borne gamma-ray telescopes at MeV - GeV energies, but could potentially also emit gamma-rays at even higher energies (Very-High-Energy [VHE] gamma-rays: E > 100 GeV), as observed by gro…
Starburst galaxies exhibit in their central regions a highly increased rate of supernovae, the remnants of which are thought to accelerate energetic cosmic rays up to energies of ~ 10^15 eV. We report the detection of gamma rays -- tracers of such cosmic rays -- from the starburst galaxy NGC 253 using the H.E.S.S. array of imaging atmospheric Cherenkov telescopes. The gamma-ray flux above 220 GeV is F = (5.5 +/- 1.0stat +/- 2.8sys) x 10^-13 ph. s-1 cm-2, implying a cosmic-ray density about three orders of magnitude larger than that in the center of the Milky Way. The fraction of cosmic-ray ene…
Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) and M82 (Acciari et al., 2009. It has been claimed that pion production due to cosmic rays accelerated in supernova remnants interacting with the interstellar gas is responsible for the observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left behind by the supernovae contribute to the TeV luminosity in a major way. A single pulsar wind nebula produces about ten times the total luminosity of the Sun at energies above 1 TeV during a lifetime of 10^5 years. …
Context: Cosmic rays are thought to be accelerated at supernova remnant (SNR) shocks, but conclusive evidence is lacking. Aims: New data from ground-based gamma-ray telescopes and the Large Area Telescope on the Fermi Gamma-ray Space Telescope are used to test this hypothesis. A simple model for gamma-ray production efficiency is compared with measured gamma-ray luminosities of SNRs, and the GeV to TeV fluxes ratios of SNRs are examined for correlations with SNR ages. Methods: The supernova explosion is modeled as an expanding spherical shell of material that sweeps up matter from the surround…
RXJ1713.7-3946 is a key object to check the supernova remnant paradigm of the origin of Galactic cosmic rays. While the origin of its gamma-ray emission (hadronic versus leptonic) is still debated, the hard spectrum at GeV energies reported by the Fermi collaboration is generally interpreted as a strong argument in favor of a leptonic scenario. On the contrary, we show that hadronic interactions can naturally explain the gamma-ray spectrum if gas clumps are present in the supernova remnant shell. The absence of thermal X-rays from the remnant fits well within this scenario.
The recent detection of the gravitational wave event GW170817, produced by the coalescence of two neutron stars, and of its optical-infrared counterpart, powered by the radioactive decay of r-process elements, has opened a new window to gamma-ray astronomy: the direct detection of photons coming from such decays. Here we calculate the contribution of kilonovae to the diffuse gamma-ray background in the MeV range, using recent results on the spectra of the gamma-rays emitted in individual events, and we compare it with that from other sources. We find that the contribution from kilonovae is not…
The LAT instrument on the Fermi Gamma-Ray Space Telescope is performing an all-sky survey from 20 MeV to 300 GeV with unprecedented statistics and angular resolution. This is providing a wealth of new information on the non-thermal emission from the Galactic interstellar medium with implications for cosmic rays and Galactic structure. First results at intermediate latitudes have already shown good agreement with predictions based on direct measurements of cosmic rays, suggesting that at least the local (within about 1 kpc from the Sun) gamma-ray emission is understood. We will present the firs…
Dark matter candidates such as weakly-interacting massive particles are predicted to annihilate or decay into Standard Model particles leaving behind distinctive signatures in gamma rays, neutrinos, positrons, antiprotons, or even anti-nuclei. Indirect dark matter searches, and in particular those based on gamma-ray observations and cosmic ray measurements could detect such signatures. Here we review the strengths and limitations of this approach and look into the future of indirect dark matter searches.
Recently, gamma-ray telescopes AGILE and Fermi observed several middle-aged supernova remnants (SNRs) interacting with molecular clouds. It is likely that their gamma rays arise from the decay of neutral pions produced by the inelastic collision between cosmic rays (CRs) and nucleons, which suggests that SNRs make the bulk of Galactic CRs. In this letter, we provide the analytical solution of the distribution of CRs that have escaped from a finite-size region, which naturally explains observed broken power-law spectra of the middle-aged SNRs. In addition, the typical value of the break energy …
The angular, spectral and temporal features of the highest energy protons and accompanying them secondary neutrinos and synchrotron gamma-rays propagating through the intergalactic magnetic and radiation fields are studied using the analytical solutions of the Boltzmann transport equation obtained in the limit of the small-angle and continuous-energy-loss approximation.
TeV gamma-rays have been observed from blazars as well as from radio galaxies like M87 and Cen A. In leptonic models, gamma-rays above the pair production threshold can escape from the ultra-relativistic jet, since large Lorentz factors reduce the background photon densities compared to those required for isotropic emission. Here we discuss an alternative scenario, where VHE photons are generated as secondaries from UHECR interaction in the AGN core. We show that TeV gamma-rays can escape from the core despite large IR and UV backgrounds. For the special case of Cen A, we study if the various …
The nearest active radio galaxy Centaurus (Cen) A is a gamma-ray emitter in GeV to TeV energy scale. The High Energy Stereoscopic System (H.E.S.S.) and non-simultaneous Fermi-LAT observation indicate an unusual spectral hardening above few GeV energies in the gamma-ray spectrum of Cen A. Very recently the H.E.S.S. observatory resolved the kilo parsec (kpc)-scale jets in Centaurus A at TeV energies. On the other hand, the Pierre Auger Observatory (PAO) detects a few ultra high energy cosmic ray (UHECR) events from Cen-A. The proton blazar inspired model, which considers acceleration of both ele…
On March 7, 2011 from 19:48:00 to 20:03:00 UT, the solar neutron telescope located at Mt. Sierra Negra, Mexico (4,600m) observed a 8.8sigma enhancement. In this paper, we would like to try to explain this enhancement by a hypothesis that a few GeV gamma-rays arrived at the top of the mountain produced by the Sun. We postulate that protons were accelerated at the shock front. They precipitate at the solar surface and produced those gamma-rays. If hypothesis is confirmed, this enhancement is the first sample of GeV gamma-rays observed by a ground level detector.
Recently a substantial part of globular cluster population has been established as GeV gamma-ray sources by the Fermi-LAT telescope. We investigate possible production of the high energy gamma-rays by relativistic electrons injected from the population of fast rotating, magnetized White Dwarfs within the globular cluster. These electrons comptonize the radiation field within the globular cluster. We conclude that gamma-rays produced by electrons accelerated by the whole population of White Dwarfs within a specific cluster are on the level of detectability of the future Cherenkov telescope arra…
The gamma-ray observations of molecular clouds associated with supernova remnants are considered one of the most promising ways to search for a solution of the problem of cosmic ray origin. Here we briefly review the status of the field, with particular emphasis on the theoretical and phenomenological aspects of the problem.
HESS J1731-347 (G353.6-0.7) is one of the TeV gamma-ray SNRs which shows the shell-like morphology. We have made a new analysis of the interstellar protons toward the SNR by using both the 12CO(J=1-0) and HI datasets. The results indicate that the TeV gamma-ray shell shows significant spatial correlation with the interstellar protons at a velocity range from -90 km/s to -75 km/s, and the distance corresponding to the velocity range is ~5.2 kpc, a factor of 2 larger than the previous figure 3 kpc. The total mass of the interstellar protons is estimated to be 6.4x10^4 M_sun, 25 % of which is ato…
Slightly more than 30 years ago, Whipple detection of the Crab Nebula was the start of Very High Energy gamma-ray astronomy. Since then, gamma-ray observations of this source have continued to provide new surprises and challenges to theories, with the detection of fast variability, pulsed emission up to unexpectedly high energy, and the very recent detection of photons with energy exceeding 1 PeV. In this article we review the impact of gamma-ray observations on our understanding of this extraordinary accelerator.
It is widely believe that galactic cosmic rays are originated in supernova remnants (SNRs) where they are accelerated by diffusive shock acceleration process at supernova blast waves driven by expanding SNRs. In recent theoretical developments of the diffusive shock acceleration theory in SNRs, protons are expected to accelerate in SNRs at least up to the knee energy. If SNRs are true generator of cosmic rays, they should accelerate not only protons but also heavier nuclei with right proportion and the maximum energy of heavier nuclei should be atomic mass (Z) times that of protons. In this wo…
If ultra-high-energy cosmic rays (UHECRs) have extragalactic origins, as is widely assumed to be the case at least for the majority of cosmic rays with energies above a few EeV, secondary neutrinos and photons can be expected to be produced during the propagation of UHECRs through intergalactic space via interactions with cosmic background photons. The fluxes of such secondary particles are strongly dependent on the redshift evolution of the emissivity (number density times luminosity) of UHECR sources. We show how cosmic rays, neutrinos, and gamma rays can potentially provide complementary in…
The Milky Way is surrounded by a gravitationally bound gas corona extending up to the Galaxy's virial radius. Interactions of cosmic-ray particles with this gas give rise to energetic secondary gamma rays and neutrinos. We present a quantitative analysis of the neutrino and gamma-ray fluxes from the corona of the Milky Way together with a combined contribution of coronae of other galaxies. The high-energy neutrino flux is insufficient to explain the IceCube results, while the contribution to the FERMI-LAT diffuse gamma-ray flux is not negligible.
We demonstrate that young star clusters have a $γ$-ray surface brightness comparable to that of the diffuse Galactic emission (DGE), and estimate that their sky coverage in the direction of the inner Galaxy exceeds unity. We therefore suggest that they comprise a significant fraction of the DGE.
During the last decades, increasingly precise astronomical observations of the Galactic Centre (GC) region at radio, infrared, and X-ray wavelengths laid the foundations to a detailed understanding of the high energy astroparticle physics of this most remarkable location in the Galaxy. Recently, observations of this region in high energy (HE, 10 MeV - 100GeV) and very high energy (VHE, > 100 GeV) gamma rays added important insights to the emerging picture of the Galactic nucleus as a most violent and active region where acceleration of particles to very high energies -- possibly up to a PeV --…
