Context. In recent years, an in-depth gamma-ray analysis of the Orion region has been carried out by the AGILE and Fermi-LAT (Large Area Telescope) teams with the aim of estimating the H2-CO conversion factor, XCO. The comparison of the data from both satellites with models of diffuse gamma-ray Galactic emission unveiled an excess at (l,b)=[213.9, -19.5], in a region at a short angular distance from the OB star k-Ori. Possible explanations of this excess are scattering of the so-called "dark gas", non-linearity in the H2-CO relation, or Cosmic-Ray (CR) energization at the k-Ori wind shock.
Aims. Concerning this last hypothesis, we want to verify whether cosmic-ray acceleration or re-acceleration could be triggered at the k-Ori forward shock, which we suppose to be interacting with a star-forming shell detected in several wavebands and probably triggered by high energy particles.
Methods. Starting from the AGILE spectrum of the detected gamma-ray excess, showed here for the first time, we developed a valid physical model for cosmic-ray energization, taking into account re-acceleration, acceleration, energy losses, and secondary electron contribution.
Results. Despite the characteristic low velocity of an OB star forward shock during its "snowplow" expansion phase, we find that the Orion gamma-ray excess could be explained by re-acceleration of pre-existing cosmic rays in the interaction between the forward shock of k-Ori and the CO-detected, star-forming shell swept-up by the star expansion. According to our calculations, a possible contribution from freshly accelerated particles is sub-dominant with respect the re-acceleration contribution. However, a simple adiabatic compression of the shell could also explain the detected gamma-ray emission. Futher GeV and TeV observations of this region are highly recommended in order to correctly identify the real physical scenario.
Type Ib supernova Master OT J120451.50+265946.6: radio emitting shock with inhomogeneities crossing through a dense shell
本文介绍了一颗Ib型超新星（SN）Master OT J120451.50+265946.6的射电观测结果。我们的低频巨米波射电望远镜（GMRT）的数据时，SN是在光学厚相观察到的频率揭示的无线电发射区的结构的不均匀性。高频Karl G. Jansky甚大阵列的数据表明，在$\sim$ 47到$\sim 87$天之间，激波正穿过致密壳层。数据$\ge 100$天以后与非均匀同步加速器自吸收模型相当吻合。我们的模型预测，不均匀性应该在晚些时候平滑。低频GMRT观测将检验这一预测。我们的研究结果表明，为了了解年轻超新星无线电发射的复杂性质，获得良好采样的宽带无线电数据的重要性。
X-rays from shock-heated gas in recurrent-nova remnants: Nested nova shells in a structured circumstellar medium
Instituto Nacional de Astrofísica, Óptica y Electrónica（墨西哥国家天体物理学、光学和电子学研究所）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Tartu Observatory, University of Tartu（塔尔图大学塔尔图天文台）
