FIOCCHI, MARIATERESAMARIATERESAFIOCCHIONORI, FRANCESCAFRANCESCAONORIBAZZANO, ANGELAANGELABAZZANOBird, A. J.A. J.BirdBodaghee, A.A.BodagheeCharles, P. A.P. A.CharlesLepingwell, V. A.V. A.LepingwellMalizia, A.A.MaliziaMasetti, N.N.MasettiNatalucci, L.L.NatalucciUbertini, P.P.Ubertini2022-02-112022-02-1120200035-8711http://hdl.handle.net/20.500.12386/31383We report on a recent bright outburst from the new X-ray binary transient MAXI J1631-479, observed in January 2019. In particular, we present the 30-200 keV analysis of spectral transitions observed with INTEGRAL/IBIS during its Galactic plane monitoring program. In the MAXI and BAT monitoring period, we observed two different spectral transitions between the high/soft and low/hard states. The INTEGRAL spectrum from data taken soon before the second transition is best described by a Comptonized thermal component with a temperature of kT<SUB>e</SUB> ∼ 30 keV and a high-luminosity value of L_{2-200 keV}∼ 3× 10^{38} erg<SUP>-1</SUP> (assuming a distance of 8 kpc). During the second transition, the source shows a hard, power-law spectrum. The lack of high energy cut-off indicates that the hard X-ray spectrum from MAXI J1631-479 is due to a non-thermal emission. Inverse Compton scattering of soft X-ray photons from a non-thermal or hybrid thermal/non-thermal electron distribution can explain the observed X-ray spectrum although a contribution to the hard X-ray emission from a jet cannot be determined at this stage. The outburst evolution in the hardness-intensity diagram, the spectral characteristics, and the rise and decay times of the outburst are suggesting that this system is a black hole candidate.STAMPAenArticle10.1093/mnras/staa068https://academic.oup.com/mnras/article/492/3/3657/5700724?login=true2020MNRAS.492.3657FFIS/05 - ASTRONOMIA E ASTROFISICA