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We report on the results of a series of X-ray observations of the transientblack hole candidate XTE J2012+381 during the 1998 outburst performed with theBeppoSAX satellite. The observed broad-band energy spectrum can be describedwith the superposition of an absorbed disk black body, an iron line plus a highenergy component, modelled with either a power law or a Comptonisation tail.The source showed pronounced spectral variability between our fiveobservations. While the soft component in the spectrum remained almostunchanged throughout our campaign, we detected a hard spectral tail whichextended to 200 keV in the first two observations, but became barely detectableup to 50 keV in the following two. A further re-hardening is observed in thefinal observation. The transition from a hard to a soft and then back to a hardstate occurred around an unabsorbed 0.1-200 keV luminosity of 10^38 erg/s (at10 kpc). This indicates that state transitions in XTE 2012+281 are probably notdriven only by mass accretion rate, but additional physical parameters mustplay a role in the evolution of the outburst.Comment: Paper accepted for publication on A&A (macro included, 9 pages, 5  figures

The 1998 outburst of the X–ray transient XTE J2012+381 as observed with BeppoSAX