Parkes observations for project P852 semester 2013OCTS

A recently-discovered magnetar near the Galactic Centre, J1745-2900, appears to be the source of both low-dispersion radio pulses (implying that it's nearby) and high-dispersion radio pulses (implying that it's far away). We believe that the low-dispersion radio pulses actually originate in the Earth's atmosphere, from particle cascades caused by high-energy gamma-rays from the magnetar. This hypothesis has a range of implications - including discrete subpulses from individual cascades, correlation with the Earth's magnetic field, and the near-field anisotropic nature of the radio emission - which we can test with the Parkes telescope. If successful, this would be the first detection of atmospheric particle cascades in this frequency range, the first radio detection of gamma-ray-initiated cascades at any frequency, and a demonstration of a potential new technique for gamma-ray astronomy.

近日发现的银心附近磁星J1745-2900，似乎同时是低色散射电脉冲与高色散射电脉冲的起源——前者暗示该天体距离较近，后者则暗示其距离遥远。我们认为，这些低色散射电脉冲实则源自地球大气层，由该磁星发出的高能伽马射线引发的粒子级联所产生。该假说具备多项可验证推论，包括单个粒子级联产生的离散子脉冲、与地球磁场的相关性，以及射电辐射的近场各向异性特性，我们可通过帕克斯望远镜（Parkes Telescope）对其开展检验。若验证成功，这将是该频段内大气粒子级联的首次探测，亦是任意频段下伽马射线引发级联的首次射电探测，同时可证明一种用于伽马射线天文学的潜在新技术。