Revealing a hard X-ray spectral component that reverberates within one light hour of the central supermassive black hole in Ark 564

摘要

Context. Arakelian 564 (Ark 564, z = 0.0247) is an X-ray-bright narrow-line Seyfert 1 galaxy. By using advanced X-ray timing techniques, an excess of "delayed" emission in the hard X-ray band (4-7.5 keV) following about 1000 s after "flaring" light in the soft X-ray band (0.4-1 keV) was recently detected.