Broadband X-ray observations of four gamma-ray narrow-line Seyfert 1 galaxies

Abstract

Narrow-line Seyfert 1 galaxies (NLS1s) is one of the few classes of active galactic nuclei (AGN) harboring powerful relativistic jets and detected in γ rays. NLS1s are well-known X-ray sources. While in non-jetted sources the origin of this X-ray emission may be a hot corona surrounding the accretion disk, in jetted objects, especially beamed ones, the contribution of corona and relativistic jet is difficult to disentangle without a proper sampling of the hard X-ray emission. For this reason, we observed with NuSTAR the first four NLS1s detected at high energy γ rays. These data, along with XMM-Newton and Swift/XRT observations, confirmed that X rays originate both in the jet and in the accretion disk corona. Time variability in hard X rays furthermore suggests that, as observed in flat-spectrum radio quasars, the dissipation region during flares could change its position from source to source, and it can be located both inside and outside the broad-line region. We find that jetted NLS1s, and other blazars as well, seem not to follow the classical fundamental plane of BH activity, which therefore should be used as a BH mass estimator in blazars with extreme care only. Our results strengthen the idea according to which γ-NLS1s are smaller and younger version of flat-spectrum radio quasars, in which both a Seyfert and a blazar component co-exist.

Hunting for the nature of the enigmatic narrow-line Seyfert 1 galaxy PKS 2004-447

“…where r is the radius of the emitting region and τ is the observed timescale. Using the 6-hour binned γ-ray light curve derived by Gokus et al (2021), the variability between adjacent points indicated that the doubling time is ∼2−4 hours, consistent with the values observed at hard X-rays by Berton et al (2019a). If we assume that the jet structure is self-similar, and that its semiopening angle is 0.1 radians, the size of the emitting region depends on the distance of the dissipation region from the central source.…”

“…This result agrees with what was found by Gallo et al (2006), who derived A(V) = 1.9 ± 1.5 from the AAT spectrum 3 . As they already pointed out, this extinction is significantly higher than what can be estimated from the X-ray spectra, which instead show negligible absorption, as confirmed by more recent observations (Kreikenbohm et al 2016;Berton et al 2019a;Gokus et al 2021). They also suggested that a possible explanation for this is a very different gas-to-dust ratio than what is seen in the Milky Way, and the jet may play a role in this by transferring material from the nucleus into the NLR.…”

“…This may indicate that the vast majority of the flux increase was due to an enhanced activity of the relativistic jet, while the accretion disk, which produces most of the ionizing photons and later affects Hβ, played a significantly smaller, although non-negligible, role. This may reflect what is seen in the X-ray spectrum of this source, which is dominated by a power-law component coming from the relativistic jet, while the thermal Comptonization model coming from the disk corona accounts for only 2% of the total flux (Gallo et al 2006;Kreikenbohm et al 2016;Berton et al 2019a). It is worth mentioning that Gokus et al (2021) did not detect any component associated with the accretion disk in their analysis of the PKS 2004-447 X-ray spectrum observed after the flare, and this agrees well with our conclusions.…”

Jetted Narrow-Line Seyfert 1 Galaxies & Co.: Where Do We Stand?

“…Other studies at infrared/optical wavelengths [18,[269][270][271][272][273][274][275][276][277][278][279] and at X-rays [254,280,281] have been done.…”

Past, Present, and Future of the Scaling Relations of Galaxies and Active Galactic Nuclei

“…This might exclude NLSy1s that are believed to be genuinely jetted, such as the ones with c-ray detections(Berton et al, 2019). Such sources are in a different accretion domain and might be more appropriately considered in the context of a scaling law with a L/L Edd dependence(Foschini, 2014).Frontiers in Astronomy and Space Sciences | www.frontiersin.org November 2021 | Volume 8 | Article 694554…”