Constraining X-ray emission of a magnetically arrested disk by radio-loud AGNs with an extreme-ultraviolet deficit

Abstract

Aims: Active galactic nuclei (AGNs) with an extreme-ultraviolet (EUV) deficit are suggested to be powered by a magnetically arrested disk (MAD) surrounding the black hole, where the slope of EUV spectra (α_EUV) is found to possess a clearly positive relationship with the jet efficiency. In this work, we investigate the properties of X-ray emission in AGNs with an EUV deficit for the first time.
Methods: We constructed a sample of 15 objects with an EUV deficit to analyze their X-ray emission. The X-ray luminosity in 13 objects was recently processed by us, while the other two sources were gathered from archival data.
Results: It is found that the average X-ray flux of AGNs with an EUV deficit are 4.5 times larger than that of radio-quiet AGNs (RQAGNs), while the slope of the relationship between the optical-UV luminosity (L_UV) and the X-ray luminosity (L_X) is found to be similar with that of RQAGNs. For comparison, the average X-ray flux of radio-loud AGNs (RLAGNs) without an EUV deficit is about 2-3 times larger than that of RQAGNs. A strong positive correlation between α_EUV and radio loudness (R_UV) is also reported. However, there is no strong relationship between L_X and the radio luminosity (L_R).
Conclusions: Both the excess of X-ray emission of RLAGNs with an EUV deficit and the strong α_EUV − R_UV relationship can be qualitatively explained with the MAD scenario, which can help one to constrain the theoretical model of MAD.