Are the two peaks of the Cathedral QPO real harmonics?

TL;DR

This study investigates whether the two main peaks of the cathedral QPO in XTE J1859+226 are genuine harmonics by analyzing their temporal evolution, amplitude variations, and RMS-spectra, revealing differences that challenge their harmonic interpretation.

Contribution

The paper provides a detailed analysis of the two peaks' properties, questioning the harmonic relationship hypothesis based on their differing behaviors and spectral characteristics.

Findings

The two peaks do not show synchronized amplitude variations.

Their RMS-spectra differ in shape, slope, and cut-off energy.

The results cast doubt on the harmonic nature of the peaks.

Abstract

We present a study of the two main peaks of the so-called cathedral QPO in XTE J1859+226. While looking at the temporal evolution of the two features we show that they do not manifest the same amplitude of variations of their power, and do not seem to follow the flux variations in the same way. We then present their RMS-spectra and show that they do not have the same shape, slope and cut-off energy. We discuss these different facts and try to answer the question regarding the genuineness of their harmonic relationship.