An X-ray high-frequency quasi-periodic oscillation in NGC 1365

¹ College of Science, China Three Gorges University, Yichang 443002, China
² Center for Astronomy and Space Sciences, China Three Gorges University, Yichang 443002, China
³ Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China
⁴ Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, China

^⋆ Corresponding authors; zhangpeng@ctgu.edu.cn; gcliu@ctgu.edu.cn

Received: 25 May 2024
Accepted: 12 September 2024

Abstract

This study presents the detection of a high-frequency quasi-periodic oscillation (QPO) in the Seyfert galaxy NGC 1365 based on observational data obtained by XMM-Newton in January 2004. Utilizing the weighted wavelet Z-transform (WWZ) and Lomb-Scargle periodogram (LSP) methods, a QPO signal is identified at a frequency of 2.19 × 10⁻⁴ Hz (4566 s), with a confidence level of 3.6σ. The signal is notably absent in the lower 0.2–1.0 keV energy band, with the primary contribution emerging from the 2.0–10.0 keV band, where the confidence level reaches 3.9σ. Spectral analysis shows that there are multiple absorption and emission lines in the high-energy band (> 6 keV). The correlation between the QPO frequency (f_QPO) and the mass of the central black hole (M_BH) of NGC 1365 aligns with the established logarithmic trend observed across black holes, indicating the QPO is of high frequency. This discovery provides new clues for studying the generation mechanism of QPOs in Seyfert galaxies, which helps us understand the accretion process around supermassive black holes and the characteristics of strong gravitational fields in active galactic nuclei.