Size and disk-like shape of the broad-line region of ESO399-IG20

TL;DR

This study uses photometric reverberation mapping to measure the size and shape of the broad-line region in ESO399-IG20, revealing a nearly face-on disk-like geometry with a size of 16-20 light days.

Contribution

First detailed reverberation mapping of ESO399-IG20 determining BLR size, shape, and inclination using photometric data and light curve modeling.

Findings

BLR size is 16-20 light days.

BLR has a disk-like geometry seen nearly face-on.

Rejection of spherical BLR model.

Abstract

We present photometric reverberation mapping of the narrow-line Seyfert 1 galaxy ESO399-IG20 performed with the robotic 15 cm telescope VYSOS-6 at the Cerro Armazones Observatory. Through the combination of broad- and narrow-band filters we determine the size of the broad-line emitting region (BLR) by measuring the time delay between the variability of the continuum and the H_alpha emission line. We use the flux variation gradient method to separate the host galaxy contribution from that of the active galactic nucleus (AGN), and to calculate the 5100A luminosity L_AGN of the AGN. Both measurements permit us to derive the position of ESO399-IG20 in the BLR size -- AGN luminosity R_BLR-L_AGN^0.5 diagram. We infer the basic geometry of the BLR through modelling of the light curves. The pronounced sharp variability patterns in both the continuum and the emission line light curves allow us to reject a spherical BLR geometry. The light curves are best fitted by a disk-like BLR seen nearly face-on with an inclination angle of 6+/-3 degrees and with an extension from 16 to 20 light days.