High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars
M. Giroletti, F. Massaro, R. D'Abrusco, R. Lico, D. Burlon, N. Hurley-Walker, M. Johnston-Hollitt, J. Morgan, V. Pavlidou, M. Bell, G. Bernardi, R. Bhat, J. D. … 展开作者
M. Giroletti, F. Massaro, R. D'Abrusco, R. Lico, D. Burlon, N. Hurley-Walker, M. Johnston-Hollitt, J. Morgan, V. Pavlidou, M. Bell, G. Bernardi, R. Bhat, J. D. Bowman, F. Briggs, R. J. Cappallo, B. E. Corey, A. A. Deshpande, A. Ewall-Rice, D. Emrich, B. M. Gaensler, R. Goeke, L. J. Greenhill, B. J. Hazelton, L. Hindson, D. L. Kaplan, J. C. Kasper, E. Kratzenberg, L. Feng, D. Jacobs, N. Kurdryavtseva, E. Lenc, C. J. Lonsdale, M. J. Lynch, B. McKinley, S. R. McWhirter, D. A. Mitchell, M. F. Morales, E. Morgan, D. Oberoi, A. R. Offringa, S. M. Ord, B. Pindor, T. Prabu, P. Procopio, J. Riding, A. E. E. Rogers, A. Roshi, N. Udaya Shankar, K. S. Srivani, R. Subrahmanyan, S. J. Tingay, M. Waterson, R. B. Wayth, R. L. Webster, A. R. Whitney, A. Williams, C. L. Williams
Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies.
We characterize the spectral properties of the blazar population at low radio frequency compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources.
We cross-correlated the 6,100 deg^2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected by Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by \fermilat. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue.
We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray blazar candidates. The mean low-frequency (120--180 MHz) blazar spectral index is $\langle α_\mathrm{low} \rangle=0.57\pm0.02$: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at $\sim$GHz frequencies. Low-frequency radio flux density and gamma-ray energy flux display a mildly significant and broadly scattered correlation. Ten unidentified gamma-ray sources have a (probably fortuitous) positional match with low radio frequency sources.
Low-frequency radio astronomy provides important information about sources with a flat radio spectrum and high energy. However, the relatively low sensitivity of the present surveys still misses a significant fraction of these objects. Upcoming deeper surveys, such as the GaLactic and Extragalactic All-Sky MWA (GLEAM) survey, will provide further insight into this population.
Simultaneous Observations of Giant Pulses from the Crab Pulsar, with the Murchison Widefield Array and Parkes Radio Telescope: Implications for the Giant Pulse Emission Mechanism
Discovery of a 24-millisecond pulsar in a very long orbit with the Murchison Widefield Array
International Centre for Radio Astronomy Research, Curtin University（国际射电天文研究中心，科廷大学）；Australian SKA Regional Centre (AusSRC), Curtin University（澳大利亚SKA区域中心（AusSRC），科廷大学）；Max-Planck-Institut for Radioastronomy（马克斯·普朗克射电天文研究所）
Murchison Widefield Array Observations of Anomalous Variability: A Serendipitous Night-time Detection of Interplanetary Scintillation
我们目前的观测高振幅快速（2秒）的变化对两个明亮的，紧凑的河外射电源的几百个最明亮的无线电源中的一个30x30度MWA时代的再电离场使用默奇森宽场阵列（MWA）在155 MHz。在拒绝内在的，仪器，电离层的起源，我们认为最有可能的解释，这种变化是行星际闪烁（IPS），可能是一个大的日冕物质抛射从太阳传播的结果。这一点可以通过Ooty射电望远镜大致同期的观测得到证实。我们看到了从1e6公里的空间尺度上的结构的证据<1000 km to >。这些探测的偶然夜间性质说明了MWA为IPS研究开放的新机制，具有灵敏的夜间，宽场，低频观测。这一制度补充了传统的专门观测入侵防御系统的战略，并可实时用于促进专门的后续观测。与此同时，尽管阵列的分辨率为2弧分，但它允许对低频射电源中的紧凑（弧秒）结构进行大规模调查。
