Constraining X-ray emission of magnetically arrested disk (MAD) by radio-loud AGNs with extreme ultraviolet (EUV) deficit

Abstract

Aims. Active galactic nuclei (AGNs) with EUV deficit are suggested to be powered by a MAD surrounding the black hole, where the slope of EUV spectra ($\alpha_{\rm EUV}$) is found to possess a well positive relationship with the jet efficiency. In this work, we investigate the properties of X-ray emission in AGNs with EUV deficit for the first time. Methods. We construct a sample of 15 objects with EUV deficit to analyse their X-ray emission. The X-ray luminosity in 13 objects are newly processed by ourself, while the other 2 sources are gathered from archival data. Results. It is found that the average X-ray flux of AGNs with EUV deficit are 4.5 times larger than that of radio-quiet AGNs (RQAGNs), while the slope of relationship between the optical-UV luminosity ($L_{\rm UV}$) and the X-ray luminosity ($L_{\rm X}$) is found to be similar with that of RQAGNs. For comparison, the average X-ray flux of radio-loud AGNs (RLAGNs) without EUV deficit is about 2-3 times larger than that of RQAGNs. A strong positive correlation between $\alpha_{\rm EUV}$ and radio-loudness ($R_{\rm UV}$) is also reported. However, there is no strong relationship between $L_{\rm X}$ and the radio luminosity ($L_{\rm R}$). Conclusions. Both the excess of X-ray emission of RLAGNs with EUV deficit and the strong $\alpha_{\rm EUV}$-$R_{\rm UV}$ relationship can be qualitatively explained with MAD scenario, which can help to constrain the theoretical model of MAD.