Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by Fermi-LAT $γ$-ray Data and FUGIN CO Data
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| Format: | Preprint |
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2026
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| author | Mizuno, Tsunefumi Sano, Hidetoshi Murase, Takeru Oka, Tomohiko Suzuki, Hiromasa Nakahara, Naohito |
| author_facet | Mizuno, Tsunefumi Sano, Hidetoshi Murase, Takeru Oka, Tomohiko Suzuki, Hiromasa Nakahara, Naohito |
| contents | LHAASO has reported 43 sub-PeV $γ$-ray sources, which are promising candidates for cosmic-ray (CR) accelerators above the PeV energy, commonly called as PeVatrons. Multi-wavelength observations are crucial for identifying the underlying particle species and estimating the CR energy content of these sources. In this work we investigate the region around LHAASO J1912+1014u (and HESS J1912+101) using Fermi-LAT $γ$-ray data and FUGIN CO data. We analyzed 15 years of Fermi-LAT data in the 0.4--409.6 GeV energy range. By improving the standard Fermi-LAT diffuse emission model, we significantly reduced the large residuals around the source in the 1.6-12.8 GeV band. We detected a statistically significant excess above the diffuse background, which likely represents $\ge$10 GeV emission associated with the LHAASO/H.E.S.S. source. The GeV excess exhibits a hard spectrum (photon index of about 2.1) and is well reproduced by interstellar gas templates with systemic velocities of about 25 $\mathrm{km~s^{-1}}$ or 60 $\mathrm{km~s^{-1}}$. We performed a comprehensive fit to the GeV--TeV spectral energy distribution. Although a leptonic scenario can reproduce the observed spectrum, a hadronic scenario is favored once electron cooling is considered. The inferred CR proton spectrum has an index of $\sim$2.2, and the total CR proton energy above 1 GeV is (1--5) $\times 10^{49}~\mathrm{erg}$, depending on the assumed velocity range of the associated interstellar gas. A stringent upper limit on diffuse X-ray emission further supports the proton PeVatron scenario. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_02208 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by Fermi-LAT $γ$-ray Data and FUGIN CO Data Mizuno, Tsunefumi Sano, Hidetoshi Murase, Takeru Oka, Tomohiko Suzuki, Hiromasa Nakahara, Naohito High Energy Astrophysical Phenomena LHAASO has reported 43 sub-PeV $γ$-ray sources, which are promising candidates for cosmic-ray (CR) accelerators above the PeV energy, commonly called as PeVatrons. Multi-wavelength observations are crucial for identifying the underlying particle species and estimating the CR energy content of these sources. In this work we investigate the region around LHAASO J1912+1014u (and HESS J1912+101) using Fermi-LAT $γ$-ray data and FUGIN CO data. We analyzed 15 years of Fermi-LAT data in the 0.4--409.6 GeV energy range. By improving the standard Fermi-LAT diffuse emission model, we significantly reduced the large residuals around the source in the 1.6-12.8 GeV band. We detected a statistically significant excess above the diffuse background, which likely represents $\ge$10 GeV emission associated with the LHAASO/H.E.S.S. source. The GeV excess exhibits a hard spectrum (photon index of about 2.1) and is well reproduced by interstellar gas templates with systemic velocities of about 25 $\mathrm{km~s^{-1}}$ or 60 $\mathrm{km~s^{-1}}$. We performed a comprehensive fit to the GeV--TeV spectral energy distribution. Although a leptonic scenario can reproduce the observed spectrum, a hadronic scenario is favored once electron cooling is considered. The inferred CR proton spectrum has an index of $\sim$2.2, and the total CR proton energy above 1 GeV is (1--5) $\times 10^{49}~\mathrm{erg}$, depending on the assumed velocity range of the associated interstellar gas. A stringent upper limit on diffuse X-ray emission further supports the proton PeVatron scenario. |
| title | Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by Fermi-LAT $γ$-ray Data and FUGIN CO Data |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2605.02208 |