We present a spectroscopic study of two polar systems, V834 Cen and MR Ser observed with IUE (International Ultraviolet Explorer) obtained during the period 1982-1991 and 1982-1987 for both systems respectively, to diagnose the ultraviolet fluxes of C IV 1550 and He II 1640 emission lines originating in the accretion stream during different orbital phases. Two spectra for both systems showing the variations in line fluxes at different orbital phases in high and intermediate states are presented. We concentrated on calculating the line fluxes of C IV & He II emission lines. Our results show that there is spectral variability for the line fluxes at different times, similar to that for optical spectrum of V834 Cen [1] and similar to that for the light curves of MR Ser [2]. We attribute this spectral variability to the variations of mass accretion rate [3]. Also we found that the line fluxes of both CIV and He II for V834 Cen are greater than the line fluxes of MR Ser.
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