A1 Refereed original research article in a scientific journal
Switches between accretion structures during flares in 4U 1901+03
Authors: Ji L, Ducci L, Santangelo A, Zhang S, Suleimanov V, Tsygankov S, Doroshenko V, Nabizadeh A, Zhang SN, Ge MY, Tao L, Bu QC, Qu JL, Lu FJ, Chen L, Song LM, Li TP, Xu YP, Cao XL, Chen Y, Liu CZ, Cai C, Chang Z, Chen G, Chen TX, Chen YB, Chen YP, Cui W, Cui WW, Deng JK, Dong YW, Du YY, Fu MX, Gao GH, Gao H, Gao M, Gu YD, Guan J, Guo CC, Han DW, Huang Y, Huo J, Jia SM, Jiang LH, Jiang WC, Jin J, Jin YJ, Kong LD, Li B, Li CK, Li G, Li MS, Li W, Li X, Li XB, Li XF, Li YG, Li ZW, Liang XH, Liao JY, Liu BS, Liu GQ, Liu HX, Liu HW, Liu XJ, Liu YN, Lu B, Lu XF, Luo Q, Luo T, Ma X, Meng B, Nang Y, Nie JY, Ou G, Sai N, Shang RC, Song XY, Sun L, Tan Y, Tuo YL, Wang C, Wang GF, Wang J, Wang PJ, Wang WS, Wang YS, Wen XY, Wu BY, Wu BB, Wu M, Xiao GC, Xiao S, Xiong SL, Xu H, Yang JW, Yang S, Yang YJ, Yang YJ, Yi QB, Yin QQ, You Y, Zhang AM, Zhang CM, Zhang F, Zhang HM, Zhang J, Zhang P, Zhang T, Zhang W, Zhang WC, Zhang WZ, Zhang Y, Zhang YF, Zhang YJ, Zhang YH, Zhang Y, Zhang Z, Zhang Z, Zhang ZL, Zhao HS, Zhao XF, Zheng SJ, Zhou DK, Zhou JF, Zhu YX, Zhu Y, Zhuang RL
Publisher: OXFORD UNIV PRESS
Publication year: 2020
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 493
Issue: 4
First page : 5680
Last page: 5692
Number of pages: 13
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/staa569
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/47985958
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 similar to 1.5. The pulse-profile shape during the flares can be significantly different from 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 supercritical 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.
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