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).

OO Dra is a short-period Algol system with a δ Sct-like pulsator. We obtained timeseries spectra between 2016 February and May to derive the fundamental parameters of the binary star and to study its evolutionary scenario. The radial velocity (RV) curves for both components were presented, and the effective temperature of the hotter and more massive primary was determined to be T eff,1 = 8260 ± 210 K by comparing the disentangling spectrum and the Kurucz models. Our RV measurements were solved with the BV light curves of Zhang et al. (2014) using the Wilson-Devinney binary code. The absolute dimensions of each component are determined as follows:Comparison with stellar evolution models indicated that the primary star resides inside the δ Sct instability strip on the main sequence, while the cool secondary component is noticeably overluminous and oversized. We demonstrated that OO Dra is an oscillating post-mass transfer R CMa-type binary; the originally more massive star became the low-mass secondary component through mass loss caused by stellar wind and mass transfer, and the gainer became the pulsating primary as the result of mass accretion. The R CMa stars, such as OO Dra, are thought to have formed by non-conservative binary evolution and ultimately to evolve into EL CVn stars.

We present the first high-resolution spectra for the eclipsing binary V404 Lyr showing γ Dor pulsations, which we use to study its absolute properties. By fitting models to the disentangling spectrum of the primary star, we found that it has an effective temperature of T eff,1 = 7, 330 ± 150 K and a rotational velocity of v 1 sini = 148 ± 18 km s −1 . The simultaneous analysis of our double-lined radial velocities and the pulsation-subtracted Kepler data gives us accurate stellar and system parameters of V404 Lyr. The masses, radii, and luminosities are M 1 = 2.17±0.06 M ⊙ , R 1 = 1.91±0.02 R ⊙ , and L 1 = 9.4±0.8 L ⊙ for the primary, and M 2 = 1.42±0.04 M ⊙ , R 2 = 1.79±0.02 R ⊙ , and L 2 = 2.9±0.2 L ⊙ for the secondary. The tertiary component orbiting the eclipsing pair has a mass of M 3b = 0.71±0.15 M ⊙ in an orbit of P 3b = 642±3 days, e 3b = 0.21±0.04, and a 3b = 509±2 R ⊙ . The third light of l 3 = 4.1 ± 0.2% could be partly attributable to the K-type circumbinary object. By applying a multiple frequency analysis to the eclipsesubtracted light residuals, we detected 45 frequencies with signal to noise amplitude ratios larger than 4.0. Identified as independent pulsation modes, seven frequencies (f 1 − f 6 , f 9 ), their new pulsation constants, and the location in the Hertzsprung-Russell diagram indicate that the pulsating primary is a γ Dor-type variable star.

We present the Kepler photometry of KIC 6048106 exhibiting O'Connell effect and multiperiodic pulsations. Including a starspot on either of the components, light-curve synthesis indicates that this system is a semi-detached Algol with a mass ratio of 0.211, an orbital inclination of 73.9 deg, and a large temperature difference of 2,534 K. To examine in detail both spot variations and pulsations, we separately analyzed the Kepler time-series data at the interval of an orbital period by an iterative way. The results reveal that the variable asymmetries of the light maxima can be interpreted as the changes of a magnetic cool spot on the secondary component with time. Multiple frequency analyses were performed in the outside-eclipse light residuals after removal of the binarity effects from the observed Kepler data. We detected 30 frequencies with signal to noise amplitude ratios larger than 4.0, of which six (f 2 -f 6 and f 10 ) can be identified as high-order (17 ≤ n ≤ 25) low-degree (ℓ = 2) gravity-mode pulsations that were stable during the observing run of 200 d. In contrast, the other frequencies may be harmonic and combination terms. For the six frequencies, the pulsation periods and pulsation constants are in the ranges of 0.352−0.506 d and 0.232−0.333 d, respectively. These values and the position on the HR diagram demonstrate that the primary star is a γ Dor variable. The evolutionary status and the pulsation nature of KIC 6048106 are discussed.

We present the physical properties of KIC 5621294 showing light and timing variations from the Kepler photometry. Its light curve displays partial eclipses and O'Connell effect with Max II fainter than Max I, which was fitted quite well by applying third-body and spot effects to the system. The results indicate that the eclipsing pair is a classical Algol-type system with parameters of q=0.22, i=76 • .8, and ∆(T 1 -T 2 )=4,235 K, in which the detached primary component fills about 77% of its limiting lobe. Striking discrepancies exist between the primary and secondary eclipse times obtained with the method of Kwee & van Woerden. These are mainly caused by surface inhomogeneities due to spot activity detected in our light-curve synthesis. The 1,253 light-curve timings from the Wilson-Devinney code were used for a period study. It was found that the orbital period of KIC 5621294 has varied due to a periodic variation overlaid on a downward parabola. The sinusoidal variation with a period of 961 d and a semi-amplitude of 22.5 s most likely arise from a light-time effect due to a third component with a mass of M 3 sin i 3 =46.9 M Jup , which is in good agreement with that calculated from the light curve itself. If its orbital inclination is larger than about 40 • , the mass of the circumbinary object would possibly match a brown dwarf. The parabolic variation could not be fully explained by either a mass transfer between the binary components or an angular momentum via magnetic braking. It is possible that the parabola may only be the observed part of a period modulation caused by the presence of another companion in a wider orbit.

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We present a new eclipsing binary (EB) showing multiperiodic oscillations using the first three sectors of TESS photometry. The eclipse and pulsation light curves of TIC 309658221 were modeled using an iterative method to obtain a consistent photometric solution. The TESS target is a circular-orbit, detached binary system with a mass ratio of 0.349, an inclination angle of 80.42 deg, and a temperature difference of 847 K between the components. The primary component of the system lies near the red edge of the δ Sct instability region on the main-sequence band in the Hertzsprung-Russell diagram. Multiple frequency analyses were applied to the eclipse-subtracted residuals after removing the binary effects in the observed data. These resulted in the detection of 26 frequencies, of which f 1 − f 6 were independent pulsation frequencies. The 20 other frequencies could be mainly caused by orbital harmonics (f 8 and f 11 ) or combination frequencies. The period ratios and pulsation constants of the f 1 − f 6 frequencies are in the ranges of P pul /P orb = 0.010−0.013 and Q = 0.027−0.036 days, respectively, which are typical of δ Sct type. The results reveal that TIC 309658221 is an eclipsing δ Sct star with an orbital period of 7.5952 days and pulsation frequencies of 9.94−13.01 day −1 . This work demonstrates that the 2-min cadence observations of TESS are very useful for the study of pulsating EBs with multiple frequencies and low amplitudes.

IM Per is a triple star system whose eclipsing pair masses and radii are accurate to within 1%. The Transiting Exoplanet Survey Satellite (TESS) light curve of the program target exhibits partial eclipses and multiple oscillations with millimagnitude-level amplitudes. It is found that the oscillations affect eclipse timing measurements. Binary modeling of the high-quality TESS data indicates that the eclipsing components of the triple system are twin dwarfs with parameters of M 2/M 1 = 0.995, R 2/R 1 = 0.901, and Δ( – ) = 12 K in an eccentric (e = 0.049), detached configuration. The third light of l 3 = 0.054 may mostly come from a G-type tertiary companion. Our predicted parallax of 1.52 ± 0.09 mas is concurrent with the Gaia measurement of 1.52 ± 0.05 mas. Multifrequency analysis of the outside-eclipse residuals reveals 22 significant pulsation signals: 4 in the gravity-mode region (0.03−2.22 day−1) and 18 in the pressure-mode region (9.19−25.12 day−1). Of the low frequencies, f 11 and f 14 are orbital harmonics that can be identified as tidally excited modes. The pulsation periods and constants for the high frequencies, and the position in the Cepheid instability strip demonstrate that the pulsating component of IM Per is a δ Sct variable.