Detection of a possible high-confidence radio quasi-periodic oscillation in the BL Lac PKS J2134-0153

TL;DR

This study detects a significant 4.69-year radio quasi-periodic oscillation in BL Lac PKS J2134-0153 using two methods, suggesting a binary black hole system as the likely cause.

Contribution

First detection of a radio QPO in BL Lac PKS J2134-0153 using Lomb-Scargle and wavelet methods, indicating potential binary black hole activity.

Findings

QPO detected at 4.69 years with >5 sigma confidence

Consistent results from two different analysis methods

Binary black hole precession likely causes the QPO

Abstract

We have searched quasi-periodic oscillations (QPOs) for BL Lac PKS J2134-0153 in the 15 GHz radio light curve announced by the Owens Valley Radio Observatory 40-m telescope during the period from 2008-01-05 to 2019-05-18, utilizing the Lomb-Scargle periodogram (LSP) and the weighted wavelet Z-transform (WWZ) techniques. This is the first time that to search for periodic radio signal in BL Lac PKS J2134-0153 by these two methods. These two methods consistently reveal a QPO of 4.69 $\pm$ 0.14 years (>5 $\sigma$ confidence level). We discuss possible causes for this QPO, and we expected that the binary black holes scenario, where the QPO is caused by the precession of the binary black holes, is the most likely explanation. BL Lac PKS J2134-0153 thus could be a good binary black hole candidate. In the binary black holes scenario, the distance between the primary black hole and the secondary black hole is 1.83$\times$10$^{16}$ cm.