A BLACK HOLE IN THE X-RAY TRANSIENT XTE J1859+226: THE FIRST CONFIRMED WITH GTC

We present the results of the analysis of the first black hole confirmed with GTC in the X-ray binary system XTEJ1859+226. By combining optical photometry taken with the INT, WHT and NOT with long-slit spectroscopy with OSIRIS+GTC, we have obtained an orbital period of 6.58 h, a secondary star radial velocity amplitude of K2 = 541 ± 70 km s −1 and an upper limit to the inclination of 70 � , implying a black hole mass of at least 5.4 M� .