Spectroscopic study of the optical counterpart to the Fast X-ray Transient IGR J17544-2619 based on observations at the 1.5-m RTT-150 telescope

摘要

We present the results of our long-term photometric and spectroscopicobservations at the Russian-Turkish RTT-150 telescope for the opticalcounterpart to one of the best-known sources, representatives of the class offast X-ray transients, IGR J17544-2619. Based on our optical data, we havedetermined for the first time the orbital and physical parameters of the binarysystem by the methods of Doppler spectroscopy. We have computed theoreticalspectra of the optical counterpart by applying non-LTE corrections for selectedlines and obtained the parameters of the stellar atmosphere and the opticalstar ($T_{\rm eff}=33\,000$ K, $\log\,g=3.85$, $R=9.5\ R_{\odot},$ and $M=23\M_{\odot}$). The latter suggest that the optical star is not a supergiant ashas been thought previously.