Multi-epoch X-ray spectral analysis of the narrow-line Seyfert 1 galaxy Mrk 478

Abstract

A multi-epoch X-ray spectral and variability analysis is conducted for the narrow-line Seyfert 1 (NLS1) active galactic nucleus (AGN) Mrk 478. All available X-ray data from XMM-Newton and Suzaku satellites, spanning from 2001 to 2017, are modelled with a variety of physical models including partial covering, soft-Comptonisation, and blurred reflection, to explain the observed spectral shape and variability over the 16 years. All models are a similar statistical fit to the data sets, though the analysis of the variability between data sets favours the blurred reflection model. In particular, the variability can be attributed to changes in flux of the primary coronal emission. Different reflection models fit the data equally well, but differ in interpretation. The use of REFLIONX predicts a low disc ionisation and power law dominated spectrum, while RELXILL predicts a highly ionised and blurred reflection dominated spectrum. A power law dominated spectrum might be more consistent with the normal X-rayto-UV spectral shape (α ox ). Both blurred reflection models suggest a rapidly spinning black hole seen at a low inclination angle, and both require a sub-solar (∼ 0.5) abundance of iron. All physical models require a narrow emission feature at 6.7 keV likely attributable to Fe XXV emission, while no evidence for a narrow 6.4 keV line from neutral iron is detected.

A broadband X-ray spectral study of the Seyfert 1 galaxy ESO 141--G055 with XMM-Newton and NuSTAR

“…We think that the spin measurement is real but the absence of any broad Fe line prevents us from making any strong claim on the spin of the black hole. We note that similar results have been previously found by Waddell et al (2019) in other Seyfert 1s where narrow Fe line is detected. In addition, we required an OVII emission line in this fit which indicates ionized emission from the disk.…”

“…The fit worsens statistically if we freeze the spin to zero ( ∆χ 2 ∼ 300). The maximally spinning black hole scenario has also been detected in previous studies in other Seyfert 1 galaxies (Ghosh et al 2016;García et al 2019;Ghosh et al 2018;Waddell et al 2019). This high value of the spin is usually associated with a broad Fe Kα which we do not detect in any of our spectra.…”

“…However, certain model parameters exhibited extreme values in certain fits which helped in ruling the models out e.g., in the sources HE 1143-1810 (Ursini et al 2020) and Zw 229.015 (Tripathi et al 2019) the ionized disk reflection model was not found suitable to describe the soft excess because the iron abundance, the inclination angle and reflection fraction were too low compared to normal values expected in Seyfert 1 galaxies. On the other hand, in Mrk 478 (Waddell et al 2019), the flux variability between data sets favoured the ionized reflection over thermal Comptonisation model.…”

“…We investigated the broadband multi-epoch data in detail to identify its possible origin. Recent studies show that blurred ionized reflection from the accretion disk can explain the origin of soft excess in several Seyfert 1 galaxies such as Mrk 509 (García et al 2019), 1H 0323+342 (Ghosh et al 2018) and Mrk 478 (Waddell et al 2019). On the other hand, the intrinsic thermal Comptonisation model can describe the soft X-ray excess better in the sources such as Ark 120 (Vaughan et al 2004;Porquet et al 2018), Mrk 530 (Ehler et al 2018), HE 1143-1810 (Ursini et al 2020) and Zw 229.015 (Tripathi et al 2019).…”

A Suzaku sample of unabsorbed narrow-line and broad-line Seyfert 1 galaxies – I. X-ray spectral properties

“…Furthermore, ionised iron emission features have been reported in both NLS1 and BLS1 AGN (e.g. Patrick et al 2012;Mantovani et al 2016;Ehler et al 2018;Waddell et al 2019). Overall, this suggests that the presence of ionised iron emission is similar for NLS1 and BLS1 galaxies.…”