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We report on a recent bright outburst from the new X-ray binary transientMAXI J1631-479, observed in January 2019. In particular, we present the 30-200keV analysis of spectral transitions observed with INTEGRAL/IBIS during itsGalactic Plane monitoring program. In the MAXI and BAT monitoring period, weobserved two different spectral transitions between the high/soft and low/hardstates. The INTEGRAL spectrum from data taken soon before the secondtransition, is best described by a Comptonised thermal component with anelectron temperature of 30 keV and a high luminosity value of 3x10^38 erg/s in2-200 keV energy range (assuming a distance of 8 kpc). During the secondtransition, the source shows a hard, power-law spectrum. The lack of highenergy cut-off indicates that the hard X-ray spectrum from MAXI J1631-479 isdue to a non-thermal emission. Inverse Compton scattering of soft X-ray photonsfrom a non-thermal or hybrid thermal/non-thermal electron distribution canexplain the observed X-ray spectrum although a contribution to the hard X-rayemission from a jet cannot be determined at this stage. The outburst evolutionin the hardness-intensity diagram, the spectral characteristics and the riseand decay times of the outburst are suggesting this system is a black holecandidate.

Evolution of MAXI J1631-479 during the January 2019 outburst observed by INTEGRAL/IBIS