论文标题
银河Pevatron候选者Lhaaso J2108+5157的多波长研究
Multi-wavelength study of the galactic PeVatron candidate LHAASO J2108+5157
论文作者
论文摘要
Lhaaso J2108+5157是少数已知的不明的超高能量(UHE)伽马射线源之一,没有高度能源(VHE),该来源最近是由Lhaaso合作发现的。我们在X射线带中观察到Lhaaso J2108+5157在2021年,XMM-Newton总共3.8小时,在TEV Energies中,具有大型望远镜原型(LST-1),产生49小时的良好质量数据。此外,我们分析了12年的Fermi-LAT数据,以更好地限制其高能量(HE)4FGL J2108.0+5155的发射。我们在能量E> 3 TEV的LST-1数据中发现了过量的(3.7 Sigma)。假定点状源的整个LST-1能量范围的进一步分析导致硬发射的提示(2.2 Sigma),可以用单个功率定律描述,具有光子指数伽马= 1.6 +-0.2 0.3-100 TEV之间。我们没有发现任何可能与XMM-Newton数据中的超新星残留(SNR)或Pulsar Wind Nebula(PWN)有关的显着延长发射,这对相对论电子的可能同步发射构成了强大的约束。 LST-1和LHAASO观测值可以解释为逆综合构成的相对论电子的逆性发射,其截止能量为$ 100^{+70} _ { - 30} $ tev。 X射线上限在同步加速器发射上施加的源中的低磁场与PWN或TEV Halo的假设兼容。在UHE来源附近缺乏脉冲星是PWN/TEV-HALO场景的挑战。 UHE伽玛射线也可以解释为$π^0 $衰减为主导的强烈发射,这是由于相对论质子与源方向上两个已知的分子云之一的相互作用。 LST-1频段中的硬光谱与质子兼容,质子在中年SNR周围逃脱了冲击,因为它们的低能量截止值。
LHAASO J2108+5157 is one of the few known unidentified Ultra-High-Energy (UHE) gamma-ray sources with no Very-High-Energy (VHE) counterpart, recently discovered by the LHAASO collaboration. We observed LHAASO J2108+5157 in the X-ray band with XMM-Newton in 2021 for a total of 3.8 hours and at TeV energies with the Large-Sized Telescope prototype (LST-1), yielding 49 hours of good quality data. In addition, we analyzed 12 years of Fermi-LAT data, to better constrain emission of its High-Energy (HE) counterpart 4FGL J2108.0+5155. We found an excess (3.7 sigma) in the LST-1 data at energies E > 3 TeV. Further analysis in the whole LST-1 energy range assuming a point-like source, resulted in a hint (2.2 sigma) of hard emission which can be described with a single power law with photon index Gamma = 1.6 +- 0.2 between 0.3 - 100 TeV. We did not find any significant extended emission which could be related to a Supernova Remnant (SNR) or Pulsar Wind Nebula (PWN) in the XMM-Newton data, which puts strong constraints on possible synchrotron emission of relativistic electrons. The LST-1 and LHAASO observations can be explained as inverse Compton-dominated leptonic emission of relativistic electrons with a cutoff energy of $100^{+70}_{-30}$ TeV. The low magnetic field in the source imposed by the X-ray upper limits on synchrotron emission is compatible with a hypothesis of a PWN or a TeV halo. The lack of a pulsar in the neighborhood of the UHE source is a challenge to the PWN/TeV-halo scenario. The UHE gamma rays can also be explained as $π^0$ decay-dominated hadronic emission due to interaction of relativistic protons with one of the two known molecular clouds in the direction of the source. The hard spectrum in the LST-1 band is compatible with protons escaping a shock around a middle-aged SNR because of their high low-energy cut-off.