{"title":"The Bicoherence Analysis of Type-C Quasiperiodic Oscillations in Swift J1727.8−1613","authors":"Haifan Zhu, Wei Wang and Ziyuan Zhu","doi":"10.3847/1538-4357/ad7587","DOIUrl":null,"url":null,"abstract":"We present the results of bicoherence analysis for Swift J1727.8−1613 during its 2023 outburst, using data from Insight-HXMT. Our analysis focused on observations with quasiperiodic oscillations (QPOs) of frequencies greater than 1 Hz, revealing that all of them belong to type-C QPOs. We found a strong correlation between the QPO frequency and the hardness ratio, as well as a linear relationship between the QPO rms and the hardness ratio. The bicoherence analysis revealed a transition from a “web” pattern to a “hypotenuse” pattern in the low-energy (LE) and high-energy (HE) bands. In the bicoherence patterns, there are correlations between horizontal and vertical bicoherence at f1 = f2 = fQPO with count rates. The diagonal structure at f1 + f2 = fQPO becomes more prominent with increasing energy. Additionally, we discovered a new bicoherence pattern in the medium energy band from 10 to 20 keV; the diagonal structure at f1 + f2 = fhar is prominent only in this energy band, which we refer to as the “parallel” pattern. The bicoherence analysis indicates that the source is likely a low-inclination source.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Astrophysical Journal","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3847/1538-4357/ad7587","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
We present the results of bicoherence analysis for Swift J1727.8−1613 during its 2023 outburst, using data from Insight-HXMT. Our analysis focused on observations with quasiperiodic oscillations (QPOs) of frequencies greater than 1 Hz, revealing that all of them belong to type-C QPOs. We found a strong correlation between the QPO frequency and the hardness ratio, as well as a linear relationship between the QPO rms and the hardness ratio. The bicoherence analysis revealed a transition from a “web” pattern to a “hypotenuse” pattern in the low-energy (LE) and high-energy (HE) bands. In the bicoherence patterns, there are correlations between horizontal and vertical bicoherence at f1 = f2 = fQPO with count rates. The diagonal structure at f1 + f2 = fQPO becomes more prominent with increasing energy. Additionally, we discovered a new bicoherence pattern in the medium energy band from 10 to 20 keV; the diagonal structure at f1 + f2 = fhar is prominent only in this energy band, which we refer to as the “parallel” pattern. The bicoherence analysis indicates that the source is likely a low-inclination source.