HAWC, the High Altitude Water Cherenkov gamma-ray observatory, is an extended air shower array optimized to survey and monitor celestial sources of TeV gamma rays over two thirds of the sky. Located at 4100m of altitude in the Northern slope of Volcán Sierra Negra, Central Mexico, HAWC has been in full-operations mode for over nine years. Taking over MILAGRO, its direct predecessor, HAWC has detected over ninety sources of very high-energy γ rays, mostly related to pulsars, engines of previously unknown TeV halos, together with energetic supernova remnants, star forming regions and microquasars, some of these emitting well above 100 TeV. Beyond the Milky Way, HAWC has found evidence of TeV photon emission from about half a dozen relatively nearby active galactic nuclei. Operated by a multi-national collaboration, HAWC is one of the most relevant scientific projects undertaken by Mexico.

The effects of chemical treatment on the radiation-shielding properties of Philippine natural zeolites were investigated using EpiXS following the EPICS2017 library. The zeolites were studied using X-ray diffraction and energy-dispersive X-ray spectroscopy. The acid treatment eliminated Fe and Ca, having a negative impact on the cross-section of the HCl-modified zeolite. The mass attenuation coefficients of the raw, NaOH- and HCl-modified zeolites at 1332 keV were 0.0545, 0.0544 and 0.0548 cm2 g–1, respectively. At 100–10,000 keV, the linear attenuation coefficient depends on the density and increases in the order HCl-modified > NaOH-modified > raw zeolite. In the energy range of 100–16,000 keV, the mean free path and half-value layer values are in the order of HCl-modified < NaOH-modified < raw zeolite. The raw and NaOH-modified zeolites have comparable effective atomic numbers, whereas the HCl-treated zeolite has significantly lower such values.

Thanks to the data of the WISE all-sky survey we discovered that the non-thermal infrared emission of blazars, the largest population of associated γ-ray sources, has peculiar spectral properties. Here we provide a summary of all results achieved on the infrared–γ-ray connection. We also show results on the latest statistical analysis of the tight correlation between the mid-infrared colors and the γ-ray spectral index for Fermi blazars, a connection that links both emitted powers and spectral shapes of particles accelerated in blazar jets over ten decades in frequency of the electromagnetic spectrum. Finally, we outline all developments performed in the last decade achieved using the infrared– γ-ray connection to discover hundreds of new blazars within the sample of unidentified γ-ray sources thanks to optical spectroscopic observations.

Acceleration times of particles responsible for the gamma-rays in supernova remnants (SNRs) are comparable with SNR age. If the number of particles starting acceleration was varying during early times after the supernova explosion then this variation should be reflected in the shape of the gamma-ray spectrum. In order to analyse this effect, we consider the time variation of the radio spectral index in SN1987A and solution of the non-stationary equation for particle acceleration. We reconstruct evolution of the particle injection in SN1987A, apply it to derive the particle momentum distribution in IC443 and model its gamma-ray spectrum. We show that: i) observed break in the proton spectrum around 50 GeV in IC443 is a consequence of the variation of the cosmic ray injection; ii) shape of the hadronic gamma-ray spectrum in SNRs critically depends on the temporal variation of the cosmic ray injection in the immediate post explosion phases.

Gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. The Cherenkov Telescope Array (CTA) is an international initiative to build the next-generation ground-based gamma-ray observatory which will have a factor of 5-10 improvement in sensitivity in the 100 GeV - 10 TeV range and an extension to energies well below 100 GeV and above 100 TeV. CTA is planned to consist of two arrays (one in the North and another in the South Hemisphere) and will provide the deepest insight ever reached into the non-thermal high-energy Universe and its particle accelerators.

PSR B1259 – 63 is a 47 ms radio pulsar with a high spin-down luminosity which is in a close, highly eccentric 3·5 yr orbit about a bright stellar companion. The binary system may be a detectable source of hard ã γ-rays produced by inverse Compton scattering of photons from the B2e star SS2883 by electrons and positrons in the pulsar wind. The star provides an enormous density of optical photons in the vicinity of the pulsar, particularly at epochs near periastron. We calculate the emission from the unshocked region of the pulsar wind, assuming that it terminates at a shock where it attains pressure balance with the companion’s wind. The spectra and light curves for the inverse Compton emission from the shock-terminated wind are compared with those for an unterminated wind. If the pulsar’s wind is weaker than that from the companion star, the termination of the wind decreases the inverse Compton flux, particularly near periastron. The termination shock geometry has the effect of decreasing the asymmetry of the γ-ray light curve around periastron, which arises because of the asymmetrical variation of the scattering angle.

In the past few years, gamma-ray astronomy has entered a golden age. At TeV energies, only a handful of sources were known a decade ago, but the current generation of ground-based imaging atmospheric Cherenkov telescopes has increased this number to more than one hundred. At GeV energies, the Fermi Gamma-ray Space Telescope has increased the number of known sources by nearly an order of magnitude in its first 2 years of operation. The recent detection and unprecedented morphological studies of gamma-ray emission from shell-type supernova remnants is of great interest, as these analyses are directly linked to the long standing issue of the origin of the cosmic-rays. However, these detections still do not constitute a conclusive proof that supernova remnants accelerate the bulk of Galactic cosmic-rays, mainly due to the difficulty of disentangling the hadronic and leptonic contributions to the observed gamma-ray emission. In the following, I will review the most relevant results of gamma ray astronomy concerning supernova remnants (shell-type and middle-age interacting with molecular clouds).

A very high energy (VHE) γ-radiation was detected from a flat spectrum radio quasar (FSRQ) 4C 21.35 (PKS1222+21) by MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes on June 17th 2010. 4C 21.35 is only the 3rd FSRQ detected in VHE γ-rays. With its hard spectrum (Γ = 2.72±0.34) with no apparent cut-off at energies below 130 GeV and an extremely fast variation of flux (doubling in 8.6+1.1−0.9 minutes), this detection poses a challenge to existing models of VHE γ-radiation from FSRQs. The most important results of observations performed by MAGIC telescopes are presented here, as well as some possible explanations of those results.

Microquasars are X-ray binaries that show extended radio jets. These jets can accelerate particles up to relativistic energies that produce non-thermal emission from radio to TeV, and could also make a non-negligible contribution to the galactic CRs in some energy ranges. The orbital motion and compactness of these sources allow the study of high-energy astrophysical phenomena in extreme conditions that change in accessible timescales. In this work, I briefly discuss the production of broadband non-thermal emission in microquasars, putting special emphasis on the high- and the very high-energy bands.

Dense wind of a massive star can be partially captured by a companion neutron star (NS) creating a very turbulent and magnetized transition region at some distance from the NS surface. We consider the consequences of electron and hadron acceleration at such a transition region. Electrons lose energy on the synchrotron process and the inverse Compton (IC) scattering of thermal radiation from the NS surface and/or the massive star. We calculate the synchrotron spectra (from X-rays to soft γ-rays) and IC spectra in the case of sources accreting the matter under the accretor and propeller scenarios. It is argued that a population of accreting massive binaries, recently discovered by the INTEGRAL observatory, can be detectable by the Fermi LAT telescope. On the other hand, TeV γ-ray emission from other class of massive binaries can be interpreted in terms of a magnetar accreting matter in the propeller scenario. We also calculate the expected neutrino event rates in a km2 detector produced by relativistic hadrons accelerated in such scenario.

After summarizing the geometric relationship of the RHESSI flare X-ray sources with the TRACE flare loops, and the motion modes of RHESSI flare X-ray sources, we concentrate on the newly discovered downward motion of flare looptop X-ray source. In particular, we present a new argument for the flare loop shrinkage during the impulsive phase: TRACE 195 Å loop shrinkage. The temporal behavior of 195 Å loop shrinkage and its magnitude are consistent with that revealed from the RHESSI X-ray sources. Further study shows that the TRACE 195 Å loop shrinkage is in the form of oscillation, with a period of about 150 s and an amplitude of about 300 km. We discuss this oscillatory shrinkage with respect to a numerical simulation of reconnection model.

An occulted flare occurred at about 06:07 UT on November 2, 2002. The RHESSI X-ray images show two separate parts. The lower part consists of a complete loop and the upper part a coronal source which well extends above the solar limb. The loop source shrank for about 4 minutes with a speed of $\sim$24 km s$^{-1}$ during the early impulsive phase and then expanded at $\sim$7 km s$^{-1}$, while the coronal source presented an upward motion at about 6 km s$^{-1}$. The temperature of the loop-top is always higher than that near the footpoints. The temperature of the loop increased with altitude, while that of the coronal source just showed opposite variation. These results indicate that the reconnection X-point of this flare is located in between the loop-top source and the coronal source.