Starship Asterisk*

Where in powerful jets of distant active galaxies – the mightiest and most energetic objects known – are the violent outbursts of high energy gamma-ray emission produced? Very close to the central supermassive black hole and accretion disk powering these systems, or at larger distances from the "central engine", i.e. further downstream in the jet? New insights into this long-standing question became possible recently, thanks to intensive, multi-frequency radio observations of powerful active galaxies. An international team of astronomers led by Lars Fuhrmann from the Max Planck Institute for Radio Astronomy in Bonn, Germany, used some of the best single-dish radio telescopes for several years, in combination with NASA’s Fermi Gamma-ray Space Telescope, to study the place where the high energy outbursts occur. For the first time a connection between dramatic outbursts of high energy gamma-ray emission and their counterparts at many radio frequencies has been established for a large sample of galaxies. Measuring delays in time between these events finally produced better constraints on the exact location in the vicinity of supermassive black holes where the gamma-ray outbursts take place. ...

• Monthly Notices of the RAS 441(3) 1899 (2014 Jul 01) DOI: 10.1093/mnras/stu540
  arXiv.org > astro-ph > arXiv:1403.4170 > 17 Mar 2014