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We report results of the INTEGRAL Target of Opportunity observations of thetransient X-ray burster XTE J1810-189. The observations were performed on April3--6, 2008, soon after the discovery of the source and near the peak of itsoutburst. That time the source had a flux of about 50 mCrab and exhibited ahard Comptonized X-ray spectrum extending well above 100 keV. Beingapproximated by a power law with an exponetial cut-off in the broad 3--100 keVenergy band it gave the average photon index $\Gamma\simeq 1.6$ and$kT_{cutoff}\simeq 67$ keV. We found only slight indications for changes in theindex during the observation ($\Gamma$ first steady decreased from $\sim 2.0$to $\sim1.3$ and then increased back to $\sim 2.0$). However the $N_{\rmn H}$value measured by absorption in the low energy part of the spectrum changeddrastically and very irregularly (from $\sim 4\times 10^{22}$ till $\sim100\times 10^{22}$ cm$^{-2}$). There were 10 type I X-ray bursts detected fromthe source during these TOO observations. Assuming that the Eddingtonluminosity was reached during the burst with the highest peak flux we get anupper estimate for a distance to the source $D=6.4\pm0.6$ kpc. From the X-rayburst parameters we conclude that this LMXB harboures an evolved star.

Results of INTEGRAL TOO observation of the transient X-ray burster XTE J1810-189