Investigating X-ray Emission from Radio-detected Broad- and Narrow-line Seyfert 1 Galaxies

Abstract

Context: This paper presents a study of the X-ray emission for a sample of radio-detected (RD-) broad- and narrow-line Seyfert 1 galaxies (NLS1s and BLS1s). Aims: To investigate the X-ray emission properties of early-stage accretion activity or early jets in NLS1s. Methods: By fitting XMM-Newton X-ray spectra and combining with multi-band data from SDSS and FIRST, we conducted a statistical comparative study on the X-ray emission and multi-band correlations of NLS1s and BLS1s. Results: NLS1s and BLS1s show no significant difference in their soft X-ray blackbody temperatures, but NLS1s exhibit steeper hard X-ray photon indices and optical-to-X-ray slopes ($α_{\rm ox}$). Moreover, correlation analyses of various parameters reveal intrinsic differences in the X-ray emission between the two samples. For instance, at comparable optical luminosities, NLS1s exhibit a higher $ α_{\rm ox} $ (i.e., weaker X-ray emission), marginally distinct dependencies between radio luminosity and black hole mass in the fundamental plane, and different correlations between $α_{\rm ox} $ and radio loudness. Based on the relationship between UV luminosity and $α_{\rm ox} $ in RQ-AGN, the estimated X-ray excess ($Δα_{\rm ox} $) in both samples is positively correlated with radio loudness. RQ-BLS1s generally display the X-ray excess, whereas RQ-NLS1s tend to show an X-ray deficiency. The Eddington ratio of RQ-NLS1s derived from X-ray luminosity is lower than that inferred from optical luminosity, further supporting their intrinsically weaker X-ray emission. Conclusions: These differences in X-ray emission between NLS1s and BLS1s may ultimately stem from the earlier evolutionary stage of NLS1s. Multivariate linear fits among radio luminosity, X-ray luminosity, and radio loudness for NLS1s and BLS1s support a multi-wavelength radiative connection associated with jets.