ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS survey.However,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational insta...ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS survey.However,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational instability strip on the log g-T diagram ofδScuti pulsating stars.To understand the physical properties of the variable star,we observed it by the 1.0-m Cassegrain reflecting telescope at Yunnan Observatories.Multi-color light curves in B,V,R_c and I_c bands were obtained and are analyzed by using the W-D program.It is found that this variable star is a shallow-contact binary with an EB-type light curve and an orbital period of 0.3781 d rather than aδScuti star.It is a W-subtype contact binary with a mass ratio of 1.135(±0.019)and a fill-out factor of 10.4%(±5.6)%.The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn,ⅡPer and GW Tau.All of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation theory.The linear ephemeris was corrected by using 303 new determined times of light minimum.It is detected that the O-C curve shows a sinusoidal variation that could be explained by the light-travel-time effect via the presence of a cool red dwarf.The present investigation reveals that some of theδScuti-type stars beyond the red edge of pulsating instability strip on the log g-T diagram are misclassified eclipsing binaries.To understand their structures and evolutionary states,more studies are required in the future.展开更多
Eclipsing binary stars with a pulsating component are powerful tools that allow us to probe the stellar interior structure and the evolutionary statuses with a good accuracy. Therefore, in this study, spectroscopic an...Eclipsing binary stars with a pulsating component are powerful tools that allow us to probe the stellar interior structure and the evolutionary statuses with a good accuracy. Therefore, in this study, spectroscopic and photometric examinations of an eclipsing binary system V948 Her are presented. The primary component of the system is classified to be a candidate 3 Scuti variable in the literature. The fundamental stellar, atmospheric and orbital parameters, and the surface abundance of the star were determined and the pulsation behaviour was investigated in this study. The orbital parameters were derived by the analysis of radial velocity and SuperWASP light curves. The spectral classification was found to be F2V. The initial atmospheric parameters of the primary component were derived by analysis of the spectral energy distribution and hydrogen lines. The final atmospheric parameters and chemical abundances of the primary component were obtained by using the method of spectrum synthesis. As a result, the final atmospheric parameters were determined as Teff= 7100±200 K, log 9= 4.34±0.1 cgs and ζ = 2.2 4± 0.2 km s^-1. The surface abundance was found to be similar to solar. The fundamental stellar parameters of both components were also obtained to be M = 1.722 4±0.123, 0.762 4± 0.020 Me, R = 1.655 4± 0.034,M,R= 0.689 ± 0.016 R for primary and secondary components, respectively. The pulsation characteristic of the primary component was examined using SuperWASP data and the pulsation period was found to be ~0.038 d. The position of the primary pulsating component was also obtained inside the instability strip of δ Sct stars. The primary component of V948 Her was defined to be a Sct variable.展开更多
Non periodic ordered sequences obtained by production rules in formal grammars are applied to the analysis of the multi-periodicity of the δ-Scuti type variable star V784 Cas. An artificial light curve for V784 Cas i...Non periodic ordered sequences obtained by production rules in formal grammars are applied to the analysis of the multi-periodicity of the δ-Scuti type variable star V784 Cas. An artificial light curve for V784 Cas is generated by a non deterministic derivation in a context-sensitive grammar by concatenation of two sinusoidal fragments following certain word sequences. The two basic building blocks represent temporal segments in a golden ratio and the number of long and short segments in a word are also in a golden ratio.展开更多
Stellar structure and evolution theory is one of the bases in modern astronomy.Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology,since the inner information is brought ...Stellar structure and evolution theory is one of the bases in modern astronomy.Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology,since the inner information is brought to the stellar surface by the global oscillating waves and becomes observable.For stellar evolutionary speed(i.e.,how long timescale does a star stay at a special evolution phase?),because of the insurmountable gap between the timescales of the evolutionary history of human civilization and a star,it can only be roughly tested by ensemble of stars in different evolutionary stages in most cases,and all the snapshots of these stars make up our global view of stellar evolution.The effect of stellar evolution on the structure and the corresponding global size of a pulsating star will lead to tiny period variations of its pulsation modes,which are the most valuable indicators of its evolutionary state and can be used to test the stellar evolution theory by a single star rather than ensemble of stars.Here,we report a High-AmplitudeδScuti star AE Ursae Majoris,which is located in the post main-sequence(MS)evolutionary stage and its observed linear period variation rate can be practically ascribed to its evolutionary effect.The result tests the stellar evolution theory from the pre-MS to post-MS with an unprecedented precision by a single star,and the framework can be extended to other type of pulsating stars to perform precise evolutionary asteroseismology,which aims to test the current stellar evolution theory in different evolutionary stages,discover the discrepancies between the theory and observations,and ultimately build a complete and precise stellar evolution theory to backtrack the history of each of these stars.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11933008,11703080 and 11803084)the Yunnan Natural Science Foundation(No.2018FB006)。
文摘ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS survey.However,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational instability strip on the log g-T diagram ofδScuti pulsating stars.To understand the physical properties of the variable star,we observed it by the 1.0-m Cassegrain reflecting telescope at Yunnan Observatories.Multi-color light curves in B,V,R_c and I_c bands were obtained and are analyzed by using the W-D program.It is found that this variable star is a shallow-contact binary with an EB-type light curve and an orbital period of 0.3781 d rather than aδScuti star.It is a W-subtype contact binary with a mass ratio of 1.135(±0.019)and a fill-out factor of 10.4%(±5.6)%.The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn,ⅡPer and GW Tau.All of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation theory.The linear ephemeris was corrected by using 303 new determined times of light minimum.It is detected that the O-C curve shows a sinusoidal variation that could be explained by the light-travel-time effect via the presence of a cool red dwarf.The present investigation reveals that some of theδScuti-type stars beyond the red edge of pulsating instability strip on the log g-T diagram are misclassified eclipsing binaries.To understand their structures and evolutionary states,more studies are required in the future.
基金the anakkale Onsekiz Mart University Research Foundation(Project No.FBA-2018-2452)for supporting this study
文摘Eclipsing binary stars with a pulsating component are powerful tools that allow us to probe the stellar interior structure and the evolutionary statuses with a good accuracy. Therefore, in this study, spectroscopic and photometric examinations of an eclipsing binary system V948 Her are presented. The primary component of the system is classified to be a candidate 3 Scuti variable in the literature. The fundamental stellar, atmospheric and orbital parameters, and the surface abundance of the star were determined and the pulsation behaviour was investigated in this study. The orbital parameters were derived by the analysis of radial velocity and SuperWASP light curves. The spectral classification was found to be F2V. The initial atmospheric parameters of the primary component were derived by analysis of the spectral energy distribution and hydrogen lines. The final atmospheric parameters and chemical abundances of the primary component were obtained by using the method of spectrum synthesis. As a result, the final atmospheric parameters were determined as Teff= 7100±200 K, log 9= 4.34±0.1 cgs and ζ = 2.2 4± 0.2 km s^-1. The surface abundance was found to be similar to solar. The fundamental stellar parameters of both components were also obtained to be M = 1.722 4±0.123, 0.762 4± 0.020 Me, R = 1.655 4± 0.034,M,R= 0.689 ± 0.016 R for primary and secondary components, respectively. The pulsation characteristic of the primary component was examined using SuperWASP data and the pulsation period was found to be ~0.038 d. The position of the primary pulsating component was also obtained inside the instability strip of δ Sct stars. The primary component of V948 Her was defined to be a Sct variable.
文摘Non periodic ordered sequences obtained by production rules in formal grammars are applied to the analysis of the multi-periodicity of the δ-Scuti type variable star V784 Cas. An artificial light curve for V784 Cas is generated by a non deterministic derivation in a context-sensitive grammar by concatenation of two sinusoidal fragments following certain word sequences. The two basic building blocks represent temporal segments in a golden ratio and the number of long and short segments in a word are also in a golden ratio.
基金support from the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP)(No.2020L0528)the Applied Basic Research Programs of Natural Science Foundation of Shanxi Province(No.202103021223320)+1 种基金support from the National Natural Science Foundation of China(NSFC)(Nos.12005124 and 12147215)support from the NSFC(Nos.11833002,12090040,and 12090042)。
文摘Stellar structure and evolution theory is one of the bases in modern astronomy.Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology,since the inner information is brought to the stellar surface by the global oscillating waves and becomes observable.For stellar evolutionary speed(i.e.,how long timescale does a star stay at a special evolution phase?),because of the insurmountable gap between the timescales of the evolutionary history of human civilization and a star,it can only be roughly tested by ensemble of stars in different evolutionary stages in most cases,and all the snapshots of these stars make up our global view of stellar evolution.The effect of stellar evolution on the structure and the corresponding global size of a pulsating star will lead to tiny period variations of its pulsation modes,which are the most valuable indicators of its evolutionary state and can be used to test the stellar evolution theory by a single star rather than ensemble of stars.Here,we report a High-AmplitudeδScuti star AE Ursae Majoris,which is located in the post main-sequence(MS)evolutionary stage and its observed linear period variation rate can be practically ascribed to its evolutionary effect.The result tests the stellar evolution theory from the pre-MS to post-MS with an unprecedented precision by a single star,and the framework can be extended to other type of pulsating stars to perform precise evolutionary asteroseismology,which aims to test the current stellar evolution theory in different evolutionary stages,discover the discrepancies between the theory and observations,and ultimately build a complete and precise stellar evolution theory to backtrack the history of each of these stars.
