Switches between accretion structures during flares in 4U 1901+03
Abstract
We report on our analysis of the 2019 outburst of the X-ray accreting pulsar 4U 1901+03 observed with Insight-HXMT and NICER. Both spectra and pulse profiles evolve significantly in the decaying phase of the outburst. Dozens of flares are observed throughout the outburst. They are more frequent and brighter at the outburst peak. We find that the flares, which have a duration from tens to hundreds of seconds, are generally brighter than the persistent emission by a factor of 1.5. The pulse profile shape during the flares can be significantly different than that of the persistent emission. In particular, a phase shift is clearly observed in many cases. We interpret these findings as direct evidence of changes of the pulsed beam pattern, due to transitions between the sub- and super-critical accretion regimes on a short time scale. We also observe that at comparable luminosities the flares' pulse profiles are rather similar to those of the persistent emission. This indicates that the accretion on the polar cap of the neutron star is mainly determined by the luminosity, i.e., the mass accretion rate.
Cite
@article{arxiv.2002.08919,
title = {Switches between accretion structures during flares in 4U 1901+03},
author = {L. Ji and L. Ducci and A. Santangelo and S. Zhang and V. Suleimanov and S. Tsygankov and V. Doroshenko and A. Nabizadeh and S. N. Zhang and M. Y. Ge and L. Tao and Q. C. Bu and J. L. Qu and F. J. Lu and L. Chen and L. M. Song and T. P. Li and Y. P. Xu and X. L. Cao and Y. Chen and C. Z. Liu and C. Cai and Z. Chang and G. Chen and T. X. Chen and Y. B. Chen and Y. P. Chen and W. Cui and W. W. Cui and J. K. Deng and Y. W. Dong and Y. Y. Du and M. X. Fu and G. H. Gao and H. Gao and M. Gao and Y. D. Gu and J. Guan and C. C. Guo and D. W. Han and Y. Huang and J. Huo and S. M. Jia and L. H. Jiang and W. C. Jiang and J. Jin and L. D. Kong and B. Li and C. K. Li and G. Li and M. S. Li and W. Li and X. Li and X. B. Li and X. F. Li and Y. G. Li and Z. W. Li and X. H. Liang and J. Y. Liao and G. Q. Liu and H. X. Liu and H. W. Liu and X. J. Liu and Y. N. Liu and B. Lu and X. F. Lu and Q. Luo and T. Luo and X. Ma and B. Meng and Y. Nang and J. Y. Nie and G. Ou and X. Q. Ren and N. Sai and X. Y. Song and L. Sun and Y. Tan and Y. L. Tuo and C. Wang and G. F. Wang and J. Wang and P. J. Wang and W. S. Wang and Y. S. Wang and X. Y. Wen and B. Y. Wu and B. B. Wu and M. Wu and G. C. Xiao and S. Xiao and S. L. Xiong and J. W. Yang and S. Yang and Yan-Ji Yang and Yi-Jung Yang and Q. B. Yi and Q. Q. Yin and Y. You and A. M. Zhang and C. M. Zhang and F. Zhang and H. M. Zhang and J. Zhang and P. Zhang and T. Zhang and W. Zhang and W. C. Zhang and W. Z. Zhang and Yi Zhang and Y. F. Zhang and Y. J. Zhang and Y. H. Zhang and Yue Zhang and Z. Zhang and Z. L. Zhang and H. S. Zhao and X. F. Zhao and S. J. Zheng and D. K. Zhou and J. F. Zhou and Y. X. Zhu and Y. Zhu},
journal= {arXiv preprint arXiv:2002.08919},
year = {2020}
}
Comments
11 pages, 8 figures, accepted for publication in MNRAS