Are broad optical balmer lines from central accretion disk in PG 1613+658?

TL;DR

This study finds that the broad Balmer lines in PG 1613+658 are likely originating from an accretion disk, based on positive correlations between line width and flux, challenging the standard virialization model.

Contribution

It provides evidence for a disk-origin of broad Balmer lines in PG 1613+658, suggesting a different BLR structure than typically assumed in AGN models.

Findings

Positive correlation between line width and flux in PG 1613+658.

Indication of gravity-dominated, disk-like BLR structure.

Challenges the standard virialization assumption for this AGN.

Abstract

In this letter, we report positive correlations between broad line width and broad line flux for the broad balmer lines of the long-term observed AGN PG 1613+658. Rather than the expected negative correlations under the widely accepted virialization assumption for AGN BLRs, the positive correlations indicate much different BLR structures of PG 1613+658 from the commonly considered BLR structures which are dominated by the equilibrium between radiation pressure and gas pressure. Therefore, accretion disk origin is preferred for the observed broad single-peaked optical balmer lines of PG 1613+658, because of the mainly gravity dominated disk-like BLRs with radial structures having few effects from radiation pressure.