Timing Properties of the X-Ray Accreting Pulsar 1A 0535+262 Studied with Insight-HXMT
Peng-Ju Wang, Ling-Da Kong, Shuang‐Nan Zhang, Victor Doroshenko, A. Santangelo, Long Ji, Emre Seyit Yorgancioglu, Yupeng Chen, Shuang‐Nan Zhang, Jin‐Lu Qu, M. Y. Ge, Jian Li, Zhi Chang, Lian Tao, Jing-Qiang Peng, Qing-Cang Shui
Abstract
Abstract We report results on the timing analysis of the 2020 giant outburst of 1A 0535+262, using broadband data from Insight-HXMT. The analysis of the pulse profile evolution from the subcritical-luminosity to the supercritical-luminosity regime is presented for the first time. We found that the observed pulse profile exhibits a complex dependence on both energy and luminosity. A dip structure at the energy of the cyclotron resonant scattering features is found for the first time in the pulse fraction–energy relation of 1A 0535+262, when the outburst evolves in a luminosity range from 4.8 × 10 37 to 1.0 × 10 38 erg s −1 . The observed structure is luminosity dependent and appears around the source critical luminosity (∼6.7 × 10 37 erg s −1 ).