Six mid-eclipse times of the eclipsing binary XZ And are obtained, which are analyzed together with others collected from the literature. Two sets of cyclic variations with periods of 33.43 and 100.4 yr are found if a...Six mid-eclipse times of the eclipsing binary XZ And are obtained, which are analyzed together with others collected from the literature. Two sets of cyclic variations with periods of 33.43 and 100.4 yr are found if a double-Keplerian model is used to fit the data. The 1:3 ratio of the periods suggests that both cyclic variations arise from dynamic motions of two companions rather than magnetic activity of the eclipsing pair. According to the double-Keplerian model, the companions have masses of^1.32 M_⊙and^1.33 M_⊙, respectively. Comparing with the total mass of the eclipsing pair of 3.12 M_⊙, it is obvious that XZ And is a general N-body system. The strong gravitational perturbation between the two companions invalidates the double-Keplerian model. It is strange that two Keplerian periods with a 1:3 ratio are derived from the best fits with an 'inappropriate' model. This illogical, but interesting phenomenon also appears in two other Algol systems, suggesting that our discoveries deserve attention from astronomers.展开更多
The new complete BV Rc Ic light curves and spectra of the short-period eclipsing binary XZ CMi are presented.The results from the combined analysis based on the photometric and spectroscopic data show that XZ CMi is a...The new complete BV Rc Ic light curves and spectra of the short-period eclipsing binary XZ CMi are presented.The results from the combined analysis based on the photometric and spectroscopic data show that XZ CMi is a near contact binary with the secondary component filling its critical Roche lobe while the primary filling 91%of its Roche lobe.The investigation of the O-C diagram reveals that its orbital period is continuously increasing,which is consistent with the derived configuration and caused by the mass transfer from the less massive star to the more massive one.In addition,an obvious periodic modulation with the amplitude of0.0187(±0.0016)d and a high eccentric of 0.86(±0.04)is detected,which could be the results of the light time effect as a third star with the mass no less than 0.42(±0.09)M⊙orbiting around the central eclipsing binary once every 95.7(±2.1)yr.Furthermore,we found a visual companion star at 2.4′′east by south of this system at a much greater distance by direct image.The large third light contribution found from the light curve analysis could be well explained by the existence of the third star and the fourth visual one.The similar parallax and proper motion imply that the components of this hierarchical quadruple system might be bounded by gravitation.Spectroscopic observations for two visual components were carried out by the LAMOST and 2.16 m telescopes,respectively.Their different values of[Fe/H]suggest that they were not born from the same origin.Thus,XZ CMi system is an interesting and important target to study the formation of the multiple stars.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 11705111 and U1231121)
文摘Six mid-eclipse times of the eclipsing binary XZ And are obtained, which are analyzed together with others collected from the literature. Two sets of cyclic variations with periods of 33.43 and 100.4 yr are found if a double-Keplerian model is used to fit the data. The 1:3 ratio of the periods suggests that both cyclic variations arise from dynamic motions of two companions rather than magnetic activity of the eclipsing pair. According to the double-Keplerian model, the companions have masses of^1.32 M_⊙and^1.33 M_⊙, respectively. Comparing with the total mass of the eclipsing pair of 3.12 M_⊙, it is obvious that XZ And is a general N-body system. The strong gravitational perturbation between the two companions invalidates the double-Keplerian model. It is strange that two Keplerian periods with a 1:3 ratio are derived from the best fits with an 'inappropriate' model. This illogical, but interesting phenomenon also appears in two other Algol systems, suggesting that our discoveries deserve attention from astronomers.
基金the National Natural Science Foundation of China(Grant No.11922306)the Key Science Foundation of Yunnan Province(Grant No.2017FA001)the CAS Interdisciplinary Innovation Team。
文摘The new complete BV Rc Ic light curves and spectra of the short-period eclipsing binary XZ CMi are presented.The results from the combined analysis based on the photometric and spectroscopic data show that XZ CMi is a near contact binary with the secondary component filling its critical Roche lobe while the primary filling 91%of its Roche lobe.The investigation of the O-C diagram reveals that its orbital period is continuously increasing,which is consistent with the derived configuration and caused by the mass transfer from the less massive star to the more massive one.In addition,an obvious periodic modulation with the amplitude of0.0187(±0.0016)d and a high eccentric of 0.86(±0.04)is detected,which could be the results of the light time effect as a third star with the mass no less than 0.42(±0.09)M⊙orbiting around the central eclipsing binary once every 95.7(±2.1)yr.Furthermore,we found a visual companion star at 2.4′′east by south of this system at a much greater distance by direct image.The large third light contribution found from the light curve analysis could be well explained by the existence of the third star and the fourth visual one.The similar parallax and proper motion imply that the components of this hierarchical quadruple system might be bounded by gravitation.Spectroscopic observations for two visual components were carried out by the LAMOST and 2.16 m telescopes,respectively.Their different values of[Fe/H]suggest that they were not born from the same origin.Thus,XZ CMi system is an interesting and important target to study the formation of the multiple stars.
