Very-high-energy {\gamma}-ray observations of novae and dwarf novae with the MAGIC telescopes

TL;DR

This study used MAGIC telescopes to search for very-high-energy gamma-ray emission from novae and dwarf novae, finding no significant signals but setting upper limits that inform particle acceleration models.

Contribution

First combined TeV and GeV observations of novae and dwarf novae, providing constraints on particle acceleration and emission mechanisms in these explosive events.

Findings

No significant TeV gamma-ray emission detected.

Upper limits established on TeV flux and spectrum.

Constraints on proton to electron luminosity ratio in nova explosions.

Abstract

Context. In the last five years the Fermi Large Area Telescope (LAT) instrument detected GeV {\gamma}-ray emission from five novae. The GeV emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. In this case it is expected that protons in the same conditions can be accelerated to much higher energies. Consequently they may produce a second component in the {\gamma}-ray spectrum at TeV energies. Aims. We aim to explore the very-high-energy domain to search for {\gamma}-ray emission above 50 GeV and to shed light on the acceleration process of leptons and hadrons in nova explosions. Methods. We have performed observations with the MAGIC telescopes of the classical nova V339 Del shortly after the 2013 outburst, triggered by optical and subsequent GeV {\gamma}-ray detec- tions. We also briefly report on VHE observations of the symbiotic nova YY Her and the dwarf nova ASASSN-13ax. We complement the TeV MAGIC observations with the analysis of con- temporaneous Fermi-LAT data of the sources. The TeV and GeV observations are compared in order to evaluate the acceleration parameters for leptons and hadrons. Results. No significant TeV emission was found from the studied sources. We computed upper limits on the spectrum and night-by-night flux. The combined GeV and TeV observations of V339 Del limit the ratio of proton to electron luminosities to Lp<~0.15 Le.