The close binary system EG Cephei

Erdem, A.; Budding, E.; Demirçan, Osman; Değirmenci, Ö. L.; Gulmen, O.; Sezer, C.

doi:10.1002/asna.200410356

Cited by 15 publications

(16 citation statements)

References 13 publications

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“…Photoelectric light curves and their solutions have been presented by several investigators; for references, see Erdem et al (2005). The system shows a β Lyrae-type light curve with minima of about 1.0 and 0.3 mag deep.…”

Section: Eg Cepmentioning

confidence: 99%

Radial Velocity Studies of Close Binary Stars. Xiii

Ruciński

Pribulla

Mochnacki

et al. 2008

The Astronomical Journal

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Radial velocity (RV) measurements and sine-curve fits to the orbital RV variations are presented for ten close binary systems: EG Cep, V1191 Cyg, V1003 Her, BD+7• 3142, V357 Peg, V407 Peg, V1123 Tau, V1128 Tau, HH UMa, and PY Vir. While most of the studied eclipsing systems are contact binaries, EG Cep is a detached or a semidetached double-lined binary and V1003 Her is a close binary of an uncertain type seen at a very low inclination angle. We discovered two previously unknown triple systems, BD+7• 3142 and PY Vir, both with late spectral-type (K2V) binaries. Of interest is the low mass-ratio (q = 0.106) close binary V1191 Cyg showing an extremely fast period increase; the system has a very short period for its spectral type and shows a W-type light curve, a feature rather unexpected for such a low mass-ratio system.

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Section: Eg Cepmentioning

confidence: 99%

Radial Velocity Studies of Close Binary Stars. Xiii

Ruciński

Pribulla

Mochnacki

et al. 2008

The Astronomical Journal

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“…It is noteworthy that the MT process is capable of driving the orbital evolution in the limited temporal range of ETV diagrams at rates similar to the wind-driven ML counterparts (NKARL11), implying that these two mechanisms might be strongly competitive (see also Erdem et al 2005Erdem et al , 2007a. Consequently, ML through stellar winds should not be neglected in systems of semi-detached or contact configuration.…”

Section: Discussionmentioning

confidence: 99%

Efficiency of ETV diagrams as diagnostic tools for long-term period variations

Nanouris

Kalimeris

Antonopoulou

et al. 2015

A&A

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Context. The credibility of an eclipse timing variation (ETV) diagram analysis is investigated for various manifestations of the mass transfer and gravitational radiation processes in binary systems. The monotonicity of the period variations and the morphology of the respective ETV diagrams are thoroughly explored in both the direct impact and the accretion disk mode of mass transfer, accompanied by different types of mass and angular momentum losses (through a hot-spot emission from the gainer and via the L2/L3 points). Aims. Our primary objective concerns the traceability of each physical mechanism by means of an ETV diagram analysis. Also, possible critical mass ratio values are sought for those transfer modes that involve orbital angular momentum losses strong enough to dictate the secular period changes even when highly competitive mechanisms with the opposite direction act simultaneously. Methods. TheJ −Ṗ relation that governs the orbital evolution of a binary system is set to provide the exact solution for the period and the function expected to represent the subsequent eclipse timing variations. The angular momentum transport is parameterized through appropriate empirical relations, which are inferred from semi-analytical ballistic models. Then, we numerically determine the minimum temporal range over which a particular mechanism is rendered measurable, as well as the critical mass ratio values that signify monotonicity inversion in the period modulations. Results. Mass transfer rates comparable to or greater than 10 −8 M yr −1 are measurable for typical noise levels of the ETV diagrams, regardless of whether the process is conservative. However, the presence of a transient disk around the more massive component defines a critical mass ratio (q cr ≈ 0.83) above which the period turns out to decrease when still in the conservative regime, rendering the measurability of the anticipated variations a much more complicated task. The effects of gravitational radiation proved to be rather undetectable, except for systems with physical characteristics that only refer to cataclysmic variables. Conclusions. The monotonicity of the period variations and the curvature of the respective ETV diagrams depend strongly on the accretion mode and the degree of conservatism of the transfer process. Unlike the hot-spot effects, the Lagrangian points L2 and L3 support very efficient routes of strong angular momentum loss. It is further shown that escape of mass via the L3 point -when the donor is the less massive component -safely provides critical mass ratios above which the period is expected to decrease, no matter how intense the process is.

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“…However, a further argue on the absence of secular changes of the P orb in the ETV can be considered useful. For this the formula for secular period changes (∆P orb /P orb ) suggested by Erdem et al (2005):…”

Section: Evolutionmentioning

confidence: 99%

“…Using the parameters of Table 1, assuming typical values for the k and r A parameters (cf. k = 0.32, r A = 10a, Erdem et al 2005), and adopting a typicalṁ trans for Algols (i.e. 10 −8 M ⊙ yr −1 ), that will lead to very low ∆P orb (i.e.…”

Section: Evolutionmentioning

confidence: 99%

KIC 8553788: A pulsating Algol with an extreme mass ratio

Liakos

2018

A&A

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Context. The present research paper focuses on the eclipsing binary KIC 8553788 which belongs to two different types of binary systems regarding its physical properties. In particular, it is one of the 71 oscillating stars of Algol type that have been discovered so far and one of the 6 that have been published based on high cadence photometric data of the Kepler mission. In addition, it is one of the four semi-detached binaries of the group of R CMa type systems, while its pulsating component has the fourth fastest frequency among the δ Scuti stars-members of semi-detached binaries. Detailed light curves, spectroscopic and pulsation analyses are presented, while possible explanation scenarios for the evolution of the system involving past mass transfer, mass loss and/or angular momentum loss due to the presence of a tertiary component are discussed.Aims. The goal of the study is to extract the pulsational characteristics of the oscillating star of the system, to estimate the absolute parameters of its components and to provide possible explanation for its extreme evolutionary status. Methods. Ground-based spectroscopic observations using the 2.3 m "Aristarchos" telescope were obtained and used for the estimation of the spectral type of the primary component and to model the light curves of the system with higher certainty. The short cadence photometric data provided by the Kepler mission were analysed using standard eclipsing binary modelling techniques, while Fourier analysis was applied on their residuals aiming to reveal the properties of the intrinsic oscillations. The resulted photometric model was combined with published radial velocity curve to obtain accurate absolute parameters for the components of the system. Results. The results show that the primary component of the system is of A8 spectral type, has a mass of 1.6 M ⊙ , and a radius of 2 R ⊙ . It is a relatively fast pulsator of δ Scuti type that oscillates in 89 frequency modes with the dominant one to be 58.26 cycles day −1 . On the other hand, the secondary component has a mass of only 0.07 M ⊙ , a radius of 1 R ⊙ , and a temperature of 4400 K. In addition, it was found to be magnetically active with migrating cool spots on its surface. Conclusions. KIC 8553788 according to its geometrical configuration and its pulsational properties belongs to the group of the oscillating stars of Algol type, while according to its very low mass ratio and its relatively short orbital period belongs also to the group of R CMa stars. If confirmed by radial velocity data of the secondary component, the system would have the lowest mass ratio that has ever been found in semi-detached systems and it can be considered as one of the most extreme cases.

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The close binary system EG Cephei

Cited by 15 publications

References 13 publications

Radial Velocity Studies of Close Binary Stars. Xiii

Radial Velocity Studies of Close Binary Stars. Xiii

Efficiency of ETV diagrams as diagnostic tools for long-term period variations

KIC 8553788: A pulsating Algol with an extreme mass ratio

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