Discovery of TeV γ-ray emission from the neighbourhood of the supernova remnant G24.7+0.6 by MAGIC

Abstract

SNR G24.7+0.6 is a 9.5 kyrs radio and gamma-ray supernova remnant evolving in a dense medium. In the GeV regime, SNR G24.7+0.6 (3FHL J1834.1-0706e/FGFS J1834.1-0706) shows a hard spectral index (Gamma similar to 2) up to 200 GeV, which makes it a good candidate to be observed with Cherenkov telescopes such as MAGIC. We observed the field of view of SNR G24.7+0.6 with the MAGIC telescopes for a total of 31 h. We detect very high-energy gamma-ray emission from an extended source located 0.34 degrees away from the centre of the radio SNR. The new source, named MAGIC J1835-069 is detected up to 5 TeV, and its spectrum is well-represented by a power-law function with spectral index of 2.74 +/- 0.08. The complexity of the region makes the identification of the origin of the very high-energy emission difficult; however, the spectral agreement with the LAT source and overlapping position at less than 1.5 sigma point to a common origin. We analysed 8 yr of Fermi-LAT data to extend the spectrum of the source down to 60 MeV. Fermi-LAT and MAGIC spectra overlap within errors and the global broad-band spectrum is described by a power law with exponential cut-off at 1.9 +/- 0.5 TeV. The detected gamma-ray emission can be interpreted as the results of proton-proton interaction between the supernova and the CO-rich surrounding.