Broadband spectral study of the jet-disc emission in the radio-loud narrow-line Seyfert 1 galaxy 1H 0323+342

TL;DR

This study analyzes the broadband X-ray to UV spectrum of the radio-loud narrow-line Seyfert 1 galaxy 1H 0323+342, revealing complex emission components including a soft X-ray excess, jet emission, and a high-spin black hole.

Contribution

It applies physically motivated models to disentangle disk, corona, and jet emissions, providing insights into the black hole spin and emission mechanisms in this galaxy.

Findings

High black hole spin ($a>0.9$) inferred from spectral fitting.

Detection of a strong soft X-ray excess and jet-related UV emission.

Variable soft excess and power-law components indicated by RMS spectra.

Abstract

We present a broadband spectral study of the radio-loud narrow-line Seyfert 1 galaxy 1H~0323+342 based on multi-epoch observations performed with NuSTAR on 2014 March 15, and two simultaneous observations performed with Suzaku and Swift on 2009 July 26 and 2013 March 1. We found the presence of a strong soft X-ray excess emission, a broad but weak Fe line and hard X-ray excess emission. We used the blurred reflection (relxill) and the intrinsic disc Comptonization (optxagnf), two physically motivated models, to describe the broadband spectra and to disentangle the disk/corona and jet emission. The relxill model is mainly constrained by the strong soft X-ray excess although the model failed to predict this excess when fitted above 3keV and extrapolated to lower energies. The joint spectral analysis of the three datasets above 3keV with this model resulted in a high black hole spin ($a>0.9$) and moderate reflection fraction $R\sim 0.5$. The optxagnf model fitted to the two simultaneous datasets resulted in an excess emission in the UV band. The simultaneous UV-to-hard X-ray spectra of 1H~0323+342 are best described by a model consisting of a primary X-ray power-law continuum with $\Gamma \sim 1.8$, a blurred reflection component with $R\sim 0.5$, Comptonised disk emission as the soft X-ray excess, optical/UV emission from a standard accretion disk around a black hole of mass $\sim 10^7{\rm M_{\odot}}$ and a steep power law ($\Gamma \sim 3-3.5$) component, most likely the jet emission in the UV band. The fractional RMS variability spectra suggest that both the soft excess and the powerlaw component are variable in nature.