摘要：The supernova remnant (SNR) G338.3−0.0 spatially correlates with HESS J1640−465, which is considered the most luminous
γ-ray
source associated with a SNR in our Galaxy. The X-ray pulsar PSR J1640−4631 has been recently discovered within
the SNR shell, which could favor a leptonic origin for the detected very-high-energy (VHE)
emission. In spite of this, the origin of the VHE radiation from HESS J1640−465 has not been unambiguously clarified so
far. Indeed, a hadronic explanation cannot be ruled out by current observations. On the
basis of atomic (HI) and molecular (12CO) archival data, we determine, for the first time,
the total ambient density of protons in the region of the G338.3−0.0/HESS J1640−465 system, a critical parameter for
understanding the emission mechanisms at very high energies. The value obtained is in the
100−130 cm-3 range. Besides this, we
developed a new hadronic model to describe the spectral energy distribution (SED) of the
HESS J1640−465 source, which
includes the latest total γ-ray cross-section for proton-proton collisions
available in the literature. By using the assessed ambient proton density, we found that
the total energy in accelerated protons required to fit the data is
5.4+4.7-2.3 ×1049 erg and 1.6+1.4-0.7 ×1050 erg for a source distance of 8.5 and 13 kpc,
respectively. The case where the source distance is 8.5 kpc agrees with the typical
scenario in which the energy released is on the order of 1051 erg and ~10% of that energy is transferred
to the accelerated protons, whereas the case corresponding to a source distance of 13 kpc
requires either a higher value of the energy released in the explosion or a larger energy
fraction to accelerate protons.
关键词：ISM: supernova remnants;ISM: individual objects: SNR G338.3-0.0;gamma rays: ISM
