... Printed in the U.S.A. ON THE CONSTANCY OF THE PHOTON INDEX OF X-RAY SPECTRA OF 4U 1728-34 THROUGH ALL SPECTRAL STATES Elena Seifina1 and Lev Titarchuk2 1 2 ,3 ,4 Sternberg Astronomical Institute, Moscow State University, Universitetsky Prospect ... We find that the X-ray broadband energy spectra of 4U 1728-34 during all spectral states can be modeled by a combination of a thermal (blackbody-like) component, a Comptonized component (which we herein denote as COMPTB), and a Gaussian component. ...