Very-high-energy (VHE >~100 GeV) gamma rays are absorbed in Earth's atmosphere and thus cannot be detected directly on Earth. Their fluxes are also typically too low to efficiently study them with satellite instruments. A VHE gamma ray entering the atmosphere initiates an electromagnetic cascade that induces faint flashes of blueish Cherenkov light

In this presentation, I will review the history and literature debate about the anomalous gamma-ray emission detected towards the inner Galaxy by the Fermi-LAT telescope. The so-called Fermi GeV excess has been first discovered in the early 2010s and later characterised by several, independent, research groups. While its main features are well

The MAGIC telescopes are a stereoscopic system of two 17m mirror diameter Cherenkov telescopes for gamma-ray observations, in operation since many years on the island of La Palma at the Observatorio del Roque de los Muchachos. A new installation allows us to use those telescopes as optical intensity interferometer which enables us to measure the