Suzaku observation of the LINER NGC 4102

TL;DR

This study presents a comprehensive X-ray, optical, and near-infrared analysis of the LINER NGC 4102, revealing it as a Compton-thick AGN with complex absorption features and variable soft excess, enhancing understanding of LINERs' nature.

Contribution

First detailed broadband spectral analysis of NGC 4102 combining Suzaku, Chandra, Swift/BAT, optical, and near-infrared data, identifying its Compton-thick nature and complex absorption structures.

Findings

NGC 4102 is a Compton-thick AGN.

Detected ionised FeXXV emission lines.

Observed variable soft X-ray excess.

Abstract

Low ionisation nuclear emission-line region (LINER) nuclei have been claimed to be different than other active galactic nuclei (AGN) due to the presence of complex absorbing structures along the line-of-sight and/or an inefficient mode of accretion onto the supermassive black hole. However, this issue is still open. We have investigated the broad band X-ray spectrum of NGC 4102, one of the most luminous LINERs in the Swift/BAT survey. We studied a 80 ksec Suzaku spectrum of NGC 4102, together with archival Chandra and Swift/BAT observations. We also studied the optical (3.5m/TWIN at Calar Alto observatory) and near-infrared (WHT/LIRIS at Observatorio Roque los Muchachos) spectra that were taken contemporaneous to the Suzaku data. There is strong evidence that NGC 4102 is a Compton-thick AGN, as suggested by the Swift/BAT detected intrinsic continuum and the presence of a strong narrow, neutral FeKa emission line. We have also detected ionised FeXXV emission lines in the Suzaku spectrum of the source. NGC 4102 shows a variable soft excess found at a significantly higher flux state by the time of Suzaku observations when compared to Chandra observations. Finally, a complex structure of absorbers is seen with at least two absorbers apart from the Compton-thick one, derived from the X-ray spectral analysis and the optical extinction.