Variability of the extreme z=4.72 blazar, GB 1428+4217
arXiv:astro-ph/9907033 · doi:10.1046/j.1365-8711.1999.02910.x
Abstract
We report X-ray and radio variability of GB 1428+4217 which confirm its blazar nature. IR observations reveal a powerful optical-UV component, not obscured by dust, which is suggestive of the presence of a billion solar mass black hole, already formed by z ~ 5. A detailed comparison of the broad band spectral properties of GB 1428+4217 with those of nearby blazars shows it to be extreme, but nevertheless consistent with the trend found for nearby sources.
MNRAS, in press - 5 pages, 5 figures