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Öğe A Comprehensive Study of the Eclipsing Binaries V1241 Tau and GQ Dra(Copernicus Foundation Polish Astronomy, 2020) Ulas, B.; Gazeas, K.; Liakos, A.; Ulusoy, C.; Stateva, I; Erkan, N.; Napetova, M.We present new photometric and spectroscopic observations and analyses for the eclipsing binary systems V1241 Tau and GQ Dra. Our photometric light and radial velocity curve analyses combined with the TESS light curves show that both are conventional semi-detached binary systems. Their absolute parameters are also derived. We present the O-C analyses of the systems and we propose the most likely orbital period modulating mechanisms. Furthermore, Fourier analyses are applied to the photometric residual data of the systems to check for the pulsational behavior of the components. We conclude that the primary component of the system GQ Dra is a delta Set type pulsator with a dominant pulsation frequency of 18.58 d(-1) based on our B filter residual light curve although it cannot be verified by 30-minute cadence TESS data. No satisfactory evidence of pulsational behavior for V1241 Tau was verified. Finally, the evolutionary tracks of the components of both systems are calculated. Their locations within evolutionary diagrams are compared with other Algol-type systems.Öğe Modelling of eclipsing binary systems with pulsating components and tertiary companions: BF Vel and RR Lep(Edp Sciences S A, 2024) Liakos, A.; Moriarty, D. J. W.; Erdem, A.; West, J. F.; Evans, P.This research paper presents a comprehensive analysis of RR Lep and BF Vel, two southern short-period, semi-detached, oscillating Algols (oEA stars) that have been shown to be triple systems. We determined the spectral types of the primary components and calculated the radial velocities from spectra observed with the Australian National University's 2.3 m telescope and Wide Field Spectrograph. The spectra of the Na I D doublet confirmed the presence of tertiary components that were apparent in the broadening function analyses. During primary eclipses chromospherical activity in their secondary components was apparent in their H-alpha spectra; it was also apparent in the Na I D spectra of BF Vel with its almost complete annular eclipse. Ground-based telescopes were used for observations in several pass bands for photometric analyses. These observations were complemented by data from the Transiting Exoplanet Survey Satellite (TESS) mission, allowing us to model the light curves, followed by a detailed analysis of pulsations. Eclipse-timing variation (ETV) analyses of both systems were used to determine the most likely mechanisms modulating the orbital period. We found mass values of M-1 = 2.9 M-circle dot and M-2 = 0.75 M-circle dot for the components of RR Lep, along with M-1 = 1.93 M-circle dot and M-2 = 0.97 M-circle dot for those of BF Vel. By integrating information from photometry, spectroscopy, and ETV analysis, we found that tertiary components revolve around both systems. The primary star of RR Lep pulsates in 36 frequencies; of these, five were identified as independent modes, with the dominant one being 32.28 d(-1). The pulsating component of BF Vel oscillates in 37 frequencies, with the frequency 46.73 d(-1) revealed as the only independent mode. For both systems, a number of frequencies were found to be related to the orbital frequency. Their physical properties were compared with other oEA stars in mass-radius and Hertzsprung-Russell diagrams, while the pulsational properties of their delta Sct components were compared with currently known systems of this type within the orbital-pulsation period and logg-pulsation period diagrams.Öğe Nature of the oscillating semi-detached eclipsing binary system IO Ursae Majoris(Oxford Univ Press, 2013) Soydugan, Faruk; Soydugan, Esin; Kanvermez, C.; Liakos, A.This paper presents results from analysing spectroscopic and multicolour photometric observations of the neglected semi-detached eclipsing binary system IO Ursae Majoris (IO UMa). For the first time, the orbital parameters of the system and fundamental physical properties of its components were determined from simultaneous analysis of BVR light curves and radial velocities of the components. The masses and radii of the primary and secondary components were found to be M-1 = 2.11 +/- 0.07 M-circle dot, M-2 = 0.29 +/- 0.02 M-circle dot and R-1 = 3.00 +/- 0.04 R-circle dot and R-2 = 3.92 +/- 0.05 R-circle dot, respectively. Derived absolute parameters yield the photometric distance of IO UMa as 263 +/- 13 pc. The projected rotational velocity of the mass-accreting hotter component was measured as 34.5 +/- 2 km s(-1), just 1.28 times faster than the synchronous value. The hotter component of the system, located in the region of the instability strip, indicates pulsational variation with short period and small amplitude. Frequency analysis after subtracting the theoretical light curve from photometric data revealed that the more massive component shows delta Scuti type pulsation with four detected frequencies. The total amplitude of the variation in the V filter was found to be 0.03 mag. Mode identification using amplitude ratios and phase differences in different filters suggests that the main pulsation frequency of 22.0148 d(-1) is probably a radial mode.Öğe Physical parameters of close binary systems: VIII(Royal Astronomical Society, 2021) Gazeas, K.; Zola, S.; Liakos, A.; Zakrzewski, B.; Rucinski, S. M.; Kreiner, J. M.; Ogloza, W.; Drozdz, M.; Koziel-Wierzbowska, D.; Stachowski, G.; Siwak, M.; Baran, A.; Kjurkchieva, D.; Marchev, D.; Erdem, A.; Szalankiewicz, S.This paper presents the results of a combined spectroscopic and photometric study of 20 contact binary systems: HV Aqr, OO Aql, FI Boo, TX Cnc, OT Cnc, EE Cet, RW Com, KR Com, V401 Cyg, V345 Gem, AK Her, V502 Oph, V566 Oph, V2612 Oph, V1363 Ori, V351 Peg, V357 Peg, Y Sex, V1123 Tau, and W UMa, which was conducted in the frame of the W UMa Project. Together with 51 already covered by the project and an additional 67 in the existing literature, these systems bring the total number of contact binaries with known combined spectroscopic and photometric solutions to 138. It was found that mass, radius, and luminosity of the components follow certain relations along the MS and new empirical power relations are extracted. We found that 30 per cent of the systems in the current sample show extreme values in their parameters, expressed in their mass ratio or fill-out factor. This study shows that, among the contact binary systems studied, some have an extremely low mass ratio (q < 0.1) or an ultrashort orbital period (P-orb < 0.25 d), which are expected to show evidence of mass transfer progress. The evolutionary status of these components is discussed with the aid of correlation diagrams and their physical and orbital parameters compared to those in the entire sample of known contact binaries. The existence of very short orbital periods confirms the very slow nature of the merging process, which seems to explain why their components still exist as MS stars in contact configurations even after several Gyr of evolution.Öğe Survey for ? Sct components in eclipsing binaries and new correlations between pulsation frequency and fundamental stellar characteristics(Oxford Univ Press, 2012) Liakos, A.; Niarchos, P.; Soydugan, Esin; Zasche, P.CCD observations of 68 eclipsing binary systems, candidates for containing delta Scuti components, were obtained. Their light curves are analysed using the (PERIOD)04 software for possible pulsational behaviour. For the systems QY Aql, CZ Aqr, TY Cap, WY Cet, UW Cyg, HL Dra, HZ Dra, AU Lac, CL Lyn and IO UMa, complete light curves were observed due to the detection of a pulsating component. All of them, except QY Aql and IO UMa, are analysed with modern astronomical softwares in order to determine their geometrical and pulsational characteristics. Spectroscopic observations of WY Cet and UW Cyg were used to estimate the spectral class of their primary components, while for HZ Dra radial velocities of its primary were measured. O - C diagram analysis was performed for the cases showing peculiar orbital period variations, namely CZ Aqr, TY Cap, WY Cet and UW Cyg, with the aim of obtaining a comprehensive picture of these systems. An updated catalogue of 74 close binaries including a delta Scuti companion is presented. Moreover, a connection between orbital and pulsation periods, as well as a correlation between evolutionary status and dominant pulsation frequency for these systems, is discussed.Öğe The Algol-type eclipsing binaries RW CrB and VZ Leo: new RI photometric study and search for pulsations(Springer, 2009) Ulas, B.; Niarchos, P. G.; Lampens, P.; Liakos, A.In this study we present the new R and I light curve solutions for the eclipsing binary systems RW CrB and VZ Leo, which for VZ Leo is the first one in the literature. Our new observations have been analyzed using the Wilson-Devinney code from which new geometric and photometric elements are derived. The geometry of both stars is that of a semi-detached binary system where the secondary component fills its Roche lobe while the primary component is well inside. In the case of RW CrB, asymmetry in the light curve was explained by a spot model. The orbital period changes of both systems were studied and the results indicated a period decrease which can be explained by angular momentum loss. We also investigated the possibility of pulsations of the primary components since these systems are mentioned as candidates of delta Sct type pulsation. However, a time-series analysis of the residual curves in the filter I does not indicate any evidence of periodic light variation for both systems. Finally, we compared the results obtained for both binary stars to those of similar systems.
