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tokens: synchrotron emission. The XMM–Newton upper limit (black arrow) and the Fermi -LAT data (red squares) are from this work. The other data are taken from Aliu et al. ( 2014 ) (VERITAS – green diamonds) and Abdo et al. ( 2007 ) (MILAGRO – pink hexagons). The blue and grey butterflies are the HAWC models from Abeysekara et al. ( 2020 ) and from Abeysekara et al. ( 2017 ), plotted for comparison, but not used in the fit. We performed a binned analysis with five bins per energy decade and spatial pixel size of . In the maximum likelihood fitting, the normalization parameter of all the sources within 3° of the ROI centre, as well as the diffuse emission components, was left free to vary. Instead the parameters of all the other sources at more than 3° were fixed to the values given in the 4FGL catalogue (Abdollahi et al. 2020 ). To describe the spatial morphology of MGRO J1908+06, we used the VERITAS emission region at 3σ level (i.e. the outermost contour in Fig. 1 ), while for the spectral model we assumed a power law with photon index Γ = 1.6. This leads to a detection significance in the energy band considered. The γ-ray flux was obtained by binning the γ-ray data in the range from 10 to 1000 GeV into four energy intervals, and performing a binned likelihood analysis in each energy bin. The resulting Fermi -LAT SED is plotted in Fig. 4 . 3.3 X-ray analysis To study the X-ray emission in the vicinity of PSR J1907+0602, we used a 52 ks long observation carried out on 2010 April 26 with the XMM–Newton satellite. We analysed the data of the European Photon Imaging Camera (EPIC)-Metal Oxide Semiconductor (MOS) instrument that was operated in full frame imaging mode and with the medium thickness optical filter. We excluded time intervals with high background, resulting in net exposure times of 36 and 38 ks for the two MOS cameras. Using the Extended Source Analysis Software ( esas 3 ), we extracted the spectra from a circular region of 5 arcmin radius centred at the position of PSR J1907+0602 (excluding a circle of 30 arcsec radius around the source) and from a concentric annular region with radii 5 and 12.5 arcmin. The latter was used to estimate the X-ray background (which in this sky region is dominated by the Galactic ridge diffuse emission). Comparison of the two spectra showed no evidence for diffuse emission associated with PSR J1907+0602, with an upper limit (at 95 per cent confidence level) of 1.2 × 10 −15 erg cm −2 s −1 arcmin −2 on the surface brightness in the 1–10 keV energy range. 4 ORIGIN OF THE γ-RAY EMISSION Emission at TeV energies indicates the presence of ultrarelativistic particles that, in principle, can produce it through inverse Compton (IC) scattering of the cosmic microwave background (CMB), infrared (IR), and/or starlight seed photons by electrons, or through the decay of neutral pions resulting from proton–proton (and/or other nuclei) interactions. In this section, we first explore the possibility that a single mechanism is