Phase-dependent Evolution within the Large Luminosity Range of 1A 0535+262 Observed by Insight-HXMT during 2020 Giant Outburst

Journal
Date Issued
2022
Author(s)
Kong, Ling-Da
•
Zhang, Shu
•
Ji, Long
•
Doroshenko, Victor
•
Santangelo, Andrea
•
•
Frontera, Filippo
•
Li, Jian
•
Chen, Yu-Peng
•
Wang, Peng-Ju
•
Chang, Zhi
•
Qu, Jin-Lu
•
Zhang, Shuang-Nan
DOI
Abstract
We have performed phase-resolved spectral analysis of the accreting pulsar 1A 0535+262 based on observations of Insight-HXMT during the 2020 type II outburst of the source. We focus on the two-dimensional dependence of the cyclotron resonance scattering features (CRSFs) along the outburst time and at different phases. The fundamental CRSF line (f-CRSF) shows different time- and phase-dependent behaviors. At higher luminosity, the phase profile of the f-CRSF energy changes from a single peak to double peaks, with the transition occurring at MJD 59185. On the contrary, the first harmonic CRSF (first CRSF) at ∼100 keV is only detected within a narrow phase range (0.8−1.0) accompanied by a shallow f-CRSF line. Based on these results, we speculate that when the source enters the supercritical regime, the higher accretion column height can significantly enhance the harmonic line at a narrow phase through an "anti-pencil" beam at a higher energy band. At the same time, it will also affect the behavior of the fundamental line.
Volume
932
Issue
2
Start page
106
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2022ApJ...932..106K
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open.access
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