MAGIC Telescopes

Oscar Blanch

The MAGIC telescopes explore the most violent phenomena of the Universe through the detection of gamma rays in the 50 GeV – 50 TeV energy range. Over the course of the past few years, MAGIC has made significant contributions to the study of the extreme astrophysical environments where VHE photons are produced, as well as to open questions in fundamental physics.

Introduction

IFAE is one of the leading institutes of the MAGIC Collaboration. We have high-level roles in the management of the Collaboration: O. Blanch is the spokesperson, and J. Rico is the coordinator of the Analysis and Publications Office. In addition, the Fundamental Physics working group was co-led through 2021 by D. Kerszberg. The MAGIC group at IFAE is responsible for the maintenance of part of the data acquisition system (receiver boards and cooling system), and of significant parts of the data analysis software. We also built and operate the official MAGIC Data Center at the Port d’Informació Científica.

During 2021, the operation of the MAGIC telescopes had to be stopped for three months due to the eruption of Cumbre Vieja at La Palma. Still, shortly after the eruption finished the MAGIC telescopes resumed operations without any significant effect related to the volcano eruption. Besides the maintenance and operation tasks, the activities of the group focused on the scientific exploitation of the instrument. M. Çolak has led the effort to look for VHE emission of millisecond Pulsars, which has led to a publication with the most relevant upper limits up to date, and finished her thesis on test of Lorentz Invariance. M. Artero has been improving reaction protocols for the MAGIC telescopes to neutrinos and gravitational waves. In addition D. Kerszberg, M. Martínez and C. Nigro contributed to a special issue on High Energy Gamma-Ray Astronomy with review articles on probing quantum gravity and data formats.

Figure 1: The MAGIC telescopes.Urs Leutenegger | MAGIC Collaboration

DETECTION OF VERY HIGH ENERGY PHOTONS FROM RS-OPHIUCHI BY THE MAGIC TELESCOPES

Novae are transient astronomical events with a sudden brightening of a point in the sky that progressively fades out usually over a period from weeks to months. They often result in a “new” star appearing in the night sky, hence the name “stella nova”. In a binary system, matter from one star can be stripped away by the other. Matter accumulated on a White Dwarf surface can eventually produce a thermonuclear explosion, outshining the companion star and causing a Nova. In some cases, the companion star provides enough material to trigger explosions every few tens of years. These are the so-called recurrent nova or recurrent symbiotic nova if the companion is a Red Giant, among which RS Ophiuchi had the most recent explosion in August 2021.

THE DETECTION OF VERY HIGH ENERGY PHOTONS FROM RS-OPHIUCHI BY THE MAGIC TELESCOPES REVEALS PROTON ACCELERATION IN THERMONUCLEAR NOVA EXPLOSIONS.

The MAGIC telescopes started observing on August 8, following the optical and Fermi-LAT alert. RS Ophiuchi is the first Nova for which very high energy gamma-rays have been detected. The data obtained with the MAGIC telescopes show that novae can emit up to at least an order of magnitude higher energies than previously thought.

The detection of gamma rays reaching 250 GeV from a recurrent symbiotic nova allowed us to obtain a deep physical insight on the population of relativistic particles accelerated by such objects. The modeling of the combined Fermi- LAT and MAGIC gamma-ray data favors the explanation of the emission via the acceleration of protons in a nova shock. Evidence towards the proton acceleration is based on: the inferred shape of the energy distribution of injected particles, the better statistical description of the gamma-ray spectral energy distribution by the proton model, and the obtained evidence of the increase of the particle maximum energies over time, consistent with lack of strong cooling. The protons in the nova shock undergo slow cooling, therefore they will be eventually able to escape the shock, carrying away a significant fraction of energy. Such protons will add to the Galactic cosmic ray budget, however primarily in the close neighborhood of novae.

Figure 1: Evolution of the gamma-ray emission of RS Ophiuchi observed by MAGIC during the 2021 outburst.