Complex Narrow Line Seyfert 1s: High spin or high inclination?

TL;DR

This paper extends a propagation-reverberation model to include absorption effects from clumpy winds, explaining the transition in X-ray lag times between simple and complex NLS1s as an inclination-dependent phenomenon.

Contribution

It introduces a combined model of reverberation and absorption to account for lag differences, linking NLS1 classes to inclination angles and wind turbulence.

Findings

Absorption from clumpy winds can cause additional hard lags.

The model explains the transition from 200s to 30s reverberation lags.

Inclination angle determines NLS1 spectral complexity.

Abstract

Complex narrow line Seyfert 1s (NLS1s), such as 1H0707-495, differ from simple NLS1s like PG1244+026 by showing stronger broad spectral features at Fe K and larger amplitude flux variability. These are correlated: the strongest Fe K features are seen during deep dips in the light curves of complex NLS1s. There are two competing explanations for these features, one where a compact X-ray source on the spin axis of a highly spinning black hole approaches the horizon and the consequent strong relativistic effects focus the intrinsic flux onto the inner edge of a thin disc, giving a dim, reflection dominated spectrum. The other is that the deep dips are caused by complex absorption by clumps close to the hard X-ray source. The reflection dominated model is able to reproduce the very short 30s soft lag from reverberation seen in the complex NLS1 1H0707-495. However, it does not explain the characteristic switch to hard lags on longer timescales. Instead, a full model of propagating fluctuations coupled to reverberation can explain the switch in the simple NLS1 PG1244+026 using a low spin black hole. However PG1244+026 has a longer reverberation lag of $\sim 200$s. Here we extend the successful propagation-reverberation model for the simple NLS1 PG1244+026 to include the effect of absorption from clumps in a turbulent region above the disk. The resulting occultations of the inner accretion flow can introduce additional hard lags when relativistic effects are taken into account. This dilutes the soft lag from reverberation and shifts it to higher frequencies, making a smooth transition between the 200s lags seen in simple NLS1s to the 30s lags in complex NLS1s. These two classes of NLS1 could then be determined by inclination angle with respect to a clumpy, probably turbulent, failed wind structure on the disc.