Hot disc of the Swift J0243.6+6124 revealed by Insight-HXMT
: Doroshenko V, Zhang SN, Santangelo A, Ji L, Tsygankov S, Mushtukov A, Qu LJ, Zhang S, Ge MY, Chen YP, Bu QC, Cao XL, Chang Z, Chen G, Chen L, Chen TX, Chen Y, Chen YB, 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, Hu W, 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 TP, Li W, Li X, Li XB, Li XF, Li YG, Li ZJ, Li ZW, Liang XH, Liao JY, Liu CZ, Liu GQ, Liu HW, Liu SZ, Liu XJ, Liu Y, Liu YN, Lu B, Lu FJ, Lu XF, Luo T, Ma X, Meng B, Nang Y, Nie JY, Ou G, Sai N, Shang RC, Song LM, Song XY, Sun L, Tan Y, Tao L, Tuo YL, Wang GF, Wang J, Wang WS, Wang YS, Wen XY, Wu BB, Wu M, Xiao GC, Xiong SL, Xu H, Xu YP, Yang YR, Yang JW, Yang S, Yang YJ, Zhang AM, Zhang CL, Zhang CM, Zhang F, Zhang HM, Zhang J, Zhang Q, Zhang T, Zhang W, Zhang WC, Zhang WZ, Zhang Y, Zhang YF, Zhang YJ, Zhang Z, Zhang ZL, Zhao HS, Zhao JL, Zhao XF, Zheng SJ, Zhu Y, Zhu YX, Zou CL, Zhang RL, Zhang RL, Zou CL, Zhu YX, Zhu Y, Zheng SJ
Publisher: OXFORD UNIV PRESS
: 2020
Monthly Notices of the Royal Astronomical Society
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
: MON NOT R ASTRON SOC
: 491
: 2
: 1857
: 1867
: 11
: 0035-8711
: 1365-2966
DOI: https://doi.org/10.1093/mnras/stz2879
: https://research.utu.fi/converis/portal/detail/Publication/46063136
We report on analysis of observations of the bright transient X-ray pulsar (XRP) Swift J0243.6+6124 obtained during its 2017-2018 giant outburst with Insight-HXMT, NuSTAR, and Swift observatories. We focus on the discovery of a sharp state transition of the timing and spectral properties of the source at super-Eddington accretion rates, which we associate with the transition of the accretion disc to a radiation pressure dominated state, the first ever directly observed for magnetized neutron star. This transition occurs at slightly higher luminosity compared to already reported transition of the source from sub- to supercritical accretion regime associate with onset of an accretion column. We argue that this scenario can only be realized for comparatively weakly magnetized neutron star, not dissimilar to other ultra-luminous X-ray pulsars, which accrete at similar rates. Further evidence for this conclusion is provided by the non-detection of the transition to the propeller state in quiescence which strongly implies compact magnetosphere and thus rules out magnetar-like fields.
