Speaker
Description
The ultrahigh-energy gamma-ray source LHAASO J1912+1013, designated 1LHAASO J1912+1014u in the first LHAASO catalog and detected by H.E.S.S. as HESS J1912+101, lies near the middle-aged pulsar PSR J1913+1011 and is an important target for studying Galactic cosmic-ray acceleration and propagation. We analyze LHAASO observations from 2021 March 5 to 2025 July 31 and Fermi--LAT data from 2008 August 4 to 2026 January 12 to investigate its morphology, spectrum, and possible radiation mechanisms. The LHAASO analysis reveals highly significant gamma-ray excesses in both the WCDA and KM2A energy ranges, with source-detection significances of $32.35\sigma$ and $13.63\sigma$, respectively. The emission is also significantly spatially extended in both energy ranges. The best-fit Gaussian extension radii, expressed as 68% containment radii, are $R_{68}=0.448\pm0.019^\circ$ for WCDA and $R_{68}=0.511\pm0.046^\circ$ for KM2A. Their best-fit centroids are $(\mathrm{R.A.},\mathrm{decl.})=((288.21\pm0.02)^\circ,(10.17\pm0.02)^\circ)$ and $((288.17\pm0.04)^\circ,(10.30\pm0.04)^\circ)$, respectively. The WCDA spectrum is described by a power law with an exponential cutoff, with a photon index of $2.02\pm0.23$ and a cutoff energy of $7.65\pm2.85~\mathrm{TeV}$, while the KM2A spectrum is described by a power law with a photon index of $3.69\pm0.15$. Analysis of 10--500 GeV \textit{Fermi}--LAT events shows that 4FGL J1913.3+1019 is also extended at $10.14\sigma$. A uniform-disk model gives a centroid of $((288.38\pm0.04)^\circ,(10.34\pm0.04)^\circ)$ and a radius of $0.84\pm0.02^\circ$. Its spectrum is described by a power law with a photon index of $2.17\pm0.26$. Broadband modeling from 30~GeV to 1 PeV shows that both leptonic and hadronic scenarios can reproduce the observed emission. We identify a spectral point with $\mathrm{TS}=4.4$ in the 1000--1585 TeV KM2A bin. Its robustness requires further assessment, particularly accounting for systematic uncertainties from Galactic diffuse emission, instrumental exposure, and the cosmic-ray background.
