Photometric, Spectroscopic, and Orbital Period Study of Three Early-Type Semi-Detached Systems: Xz Aql, Ux Her, and at Peg

Abstract

In this paper we present a combined photometric, spectroscopic and orbital period study of three early-type eclipsing binary systems: XZ Aql, UX Her, and AT Peg. As a result, we have derived the absolute parameters of their components and, on that basis, we discuss their evolutionary states. Furthermore, we compare their parameters with those of other binary systems and with the theoretical models. An analysis of all available up-to-date times of minima indicated that all three systems studied here show cyclic orbital changes; their origin is discussed in detail. Finally, we performed a frequency analysis for possible pulsational behavior and as a result we suggest that XZ Aql hosts a δ Scuti component. published the first light curve solution based on the spectroscopic orbit determined by Sanford (1937) and their own photometric observations. They proposed that the secondary was an evolved, low-mass, late-type star. Hill et al. (1975) estimated the primary component's spectral type as A0V -A3V for different orbital phases. Following the light curve studies of Cester et al. (1979), Mardirossian et al. (1980) and Giuricin & Mardirossian (1981), Lazaro et al. (1997) analyzed the first infrared light curves of the system in J, H and K bands, together with published B and V band light curves of Gordon & Kron (1965). They determined the parameters of the system and found that none of the components of the binary filled their Roche lobes. Although UX Her is a short-period system, they assigned it to a category of slightly detached systems, most of which, as they pointed out, were long-period systems. Djurašević et al. (2006) computed the mass ratio (q = m 2 / m 1 = 0.248) as the result of the q-search method. When combined with the results of their B and V band light curve analysis, this mass ratio value suggests a semi-detached configuration of UX Her. Kurzemnietse (1952) noted for the first time that the period was variable. Tremko et al. (2004) first published a period-variation study of the system, which excluded a mass transfer between the components as the cause of the observed variations in the orbital period of the system, since neither of the stars filled their Roche lobes according to their