The spectral energy distribution of PKS 2004-447: A compact steep-spectrum source and possible radio-loud narrow-line Seyfert 1 galaxy

Abstract

An investigation of the spectral energy distribution (SED) of the compact steep-spectrum (CSS) source and possible radio-loud narrow-line Seyfert 1 galaxy (NLS1), PKS 2004-447, is presented. Five out of six well-studied radio-loud NLS1 hare this dual classification [optically defined as an NLS1 with radio definition of a CSS or gigahertz-peaked spectrum (GPS) source], suggesting that the connection could have a physical origin. The SED is created from simultaneous observations (within 24 h) at radio (from Australia Telescope Compact Array), optical/near-infrared (MR) (from Siding Spring) and UV/X-ray (from XMM-Newton) wavelengths. The X-ray data show evidence of short-term variability (prima..