engleski

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

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. 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. 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 detections. 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 contemporaneous Fermi-LAT data of the sources. The TeV and GeV observations are compared in order to evaluate the acceleration parameters for leptons and hadrons. 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 L_p < 0.15 L_e.

Novae ; cataclysmic variables ; Gamma-rays ; stars ; Binaries ; general ; Stars ; activity

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