Hadronic particle acceleration in the supernova remnant SN 1006 as traced by Fermi-LAT observations

Abstract

The supernova remnant SN 1006 is a source of high-energy particles detected in the radio, X-rays, and tera-electronvolt gamma rays. It was also announced as a source of gamma rays by Fermi-LAT, but only the north-east (NE) limb was detected at a significance level of more than 5σ. Using 15 years of Fermi-LAT observations and a thorough morphological analysis above 1 GeV, we report the detection of the NE rim at the 6σ level and the southa- west (SW) rim at the 5.5σ level using radio templates from the GLEAM survey. The spectral analysis performed between 100 MeV and 1 TeV allows for the detection of a hard spectral index for the NE limb of 1.7 ± 0.1 ± 0.1, while the emission detected in the SW is reproduced well with a steeper spectral index of 2.2 ± 0.1 ± 0.1. A marginal detection (∼3σ) of emission coincident with the bright north-west Hα filament is also described with a similar spectral index of ∼2.1. We have successfully characterised the non-thermal multi-wavelength emission of the NE and SW limbs with a model in which inverse-Compton emission dominates in the NE, while proton-proton interactions becomes significant in the SW due to the enhanced density of the medium.