LAUSR

The origin of the radiation observed in the region of the supernova remnant RX J1713.7−3946, one of the brightest TeV emitters, has been debated since its discovery. The existence of atomic and molecular clouds in this object supports the idea that part of the GeV gamma-ray emission in this region originates from proton–proton collisions. However, the observed column density of protons derived from observations of the gas cannot explain the whole emission. Yet there could be a fraction of protons contained in fainter structures that have not been detected so far. Here we search for faint objects in the line of sight of RX J1713.7−3946 using the principle of light extinction and the European Space Agency’s Gaia mission Data Release 2 astrometric and photometric data. We reveal and locate with precision a number of dust clouds and note that only one appears to be in the vicinity of RX J1713.7−3946. We estimate the embedded mass to be M dust  = (7.0 ± 0.6) × 10 3   M ⊙ , which might be big enough to contain the missing protons. Finally, using the fact that the supernova remnant is expected to be located in a dusty environment and that there appears to be only one such structure in the vicinity of RX J1713.7−3946, we set a very precise constraint on the supernova remnant distance, at 1.12 ± 0.01 kpc. A dust cloud in the line of sight towards supernova remnant RX J1713.7−3946—identified using Gaia data —contributes to the GeV gamma-ray emission of the region.