New approach to broad line region radius in Mrk142 after considering potential short-term optical transient quasi-periodic oscillations

TL;DR

This paper proposes a new method for estimating the broad line region radius in Mrk142 by considering optical transient quasi-periodic oscillations, aligning its R-L relation with typical AGNs and improving understanding of BLR size measurements.

Contribution

It introduces a novel approach to assess BLR radius using optical QPOs, addressing the outlier status of Mrk142 in the R-L relation.

Findings

Probable optical QPOs with periods around 14 and 43 days detected in Mrk142.

The new BLRs radius estimate aligns with the R-L relation for normal BLAGNs.

Supports the fundamental nature of the R-L relation in low-redshift AGNs.

Abstract

Mrk142 has been known as the only outlier in R-L space (correlation between BLRs (broad line regions) radii and continuum luminosity) among the low redshift local reverberation mapped broad line AGNs (BLAGNs) with moderate accretion rates, due to its BLRs radius smaller than R-L expected value. Here, considering probable optical transient quasi-periodic oscillations (QPOs), a new approach to assessing the BLRs radius can be considered. Reliable transient QPOs in high-energy emissions from black hole vicinity have been reported in several normal AGNs, however there are so-far few short-term low-energy optical transient QPOs in normal BLAGNs (not the QPOs reported in blazars nor in AGNs harbouring binary BH systems). Through the photometric optical light curves well directly described by sinusoidal functions, we report probable short-term optical transient QPOs with periodicities around 14days and 43days in BLAGN Mrk142, indicating similar but scaled optical QPOs as those in high-energy bands. Considering the 14days QPOs related to reprocessing procedure, new approach to the BLRs radius can be estimated in Mrk142 through the reverberation mapping technique. The new BLRs radius of Mrk142 well follows the R-L relation, demonstrating the R-L relation is fundamental in local normal BLAGNs without ultra-high accretion rates.