Absolute Dimensions and Evolutionary Status of the Semi-detached Algol W Ursae Minoris

Abstract

Double-lined eclipsing binaries allow accurate and direct determination of fundamental parameters such as mass and radius for each component, and they provide important constraints on the stellar structure and evolution models. In this study, we aim to determine a unique set of binary parameters for the Algol system W UMi and to examine its evolutionary status. New high-resolution time-series spectroscopic observations were carried out during 14 nights from April 2008 to March 2011, and a total of 37 spectra were obtained using the Bohyunsan Optical Echelle Spectrograph. We measured the radial velocities (RVs) for both components, and the effective temperature of the primary star was found to be T eff,1 = 9310 ± 90 K by a comparison of the observed spectra and the Kurucz models. The physical parameters of W UMi were derived by an analysis of our RV data together with the multi-band light curves of Devinney et al. (1970). The individual masses, radii, and luminosities of both components are M 1 = 3.68 ± 0.10 M ⊙ and M 2 = 1.47 ± 0.04 M ⊙ , R 1 = 3.88 ± 0.03 R ⊙ and R 2 = 3.13 ± 0.03 R ⊙ , and L 1 = 102 ± 1 L ⊙ and L 2 = 7.3 ± 0.1 L ⊙ , respectively. A comparison of these parameters with theoretical stellar models showed that the primary component lies in the main-sequence band, while the less massive secondary is noticeably evolved.The results indicate that the initially more massive star became the present secondary by losing most of its own mass via mass transfer to the companion (present primary).

Investigation of near-contact semi-detached binary WUMi through observations and evolutionary models

“…During the model atmosphere analysis, the value of surface gravity of the primary component (log g 1 =3.83±0.02), which was calculated from the results obtained from the simultaneous analysis of the light and radial velocity curves, was taken as constant in order to avoid parameter degeneration. All atmosphere parameters were found in accordance with the values given by Park et al (2018). On the other hand, although Park et al (2018) made spectral analysis under the assumption solar metallicity, our results displayed higher metallicity than the Sun for the system.…”

“…All atmosphere parameters were found in accordance with the values given by Park et al (2018). On the other hand, although Park et al (2018) made spectral analysis under the assumption solar metallicity, our results displayed higher metallicity than the Sun for the system.…”

“…The spectroscopic orbital parameters given in Table 2 were used as input parameters in the simultaneous analysis of light and RV curves data. According to the orbital parameters, it is clear that the semi-amplitude for the RV changes in the secondary component (K 2 ≈197±3 km s −1 ) and mass ratio of the companion stars (q=0.460) were found to be different from those given by Park et al (2018).…”

“…In order to model the spectra of W UMi, especially the dominant more massive, hotter companion, the observed spectrum at the orbital phase of about 0.5 was used. We preferred the spectrum given by Park et al (2018) since the spectrum is around the secondary minimum and also has higher resolution. It is almost impossible to determine the atmospheric properties of the cooler secondary companion of W UMi because of its low light contribution (5-10%) to the total light of the target in the optical region.…”

Physical Nature of the Eclipsing δ Scuti Star AO Serpentis

“…Finally, we found the respective values for effective temperature (T eff ) and projected rotational velocity (v sin i) through a χ 2 minimization of the differences between the observed spectrum and the synthetic spectra. This is the same process that was applied by Hong et al (2017Hong et al ( , 2019, Lee et al (2018Lee et al ( , 2020, and Park et al (2018). The results are shown in Figure 1.…”