Physical origin of the non-physical spin evolution of MAXI J1820 + 070

ABSTRACT We report on the Insight-HXMT observations of new black hole X-ray binary MAXI J1820+070 during its 2018 outburst. Detailed spectral analysis via continuum fitting method shows an evolution inferred spin high soft sate. Moreover, hardness ratio, non-thermal luminosity and reflection fraction also undergo evolution, exactly coincident to period when transition takes place. The unphysical is attributed inner disc, which caused by collapse a hot corona due condensation mechanism or may be related deceleration jet-like corona. studies disc radius relation between suggest that, only at particular epoch, did edge reach innermost stable circular orbit measurement reliable. then constrain J1820 + 070 $a_*=0.2^{+0.2}_{-0.3}$. Such slowly spinning possessing strong jet suggests that activity driven mainly accretion rather than spin.