We present a study on pulsations of the high-amplitudeδScuti star YZ Boo based on photometric observations in Johnson V and R bands with both the Nanshan 1-m telescope of Xinjiang Astronomical Observatory(XAO)and the...We present a study on pulsations of the high-amplitudeδScuti star YZ Boo based on photometric observations in Johnson V and R bands with both the Nanshan 1-m telescope of Xinjiang Astronomical Observatory(XAO)and the Xinglong 85-cm telescope of National Astronomical Observatories,Chinese Academy of Sciences(NAOC).Fourier analysis of the light curves reveals the fundamental radial mode and its five harmonics,with the fourth and fifth being newly detected.Thirtynine new times of maximum light are determined from the light curves,and combined with those in the literature,we construct the O-C diagram,derive a new ephemeris and determine a new value for the updated period of 0.104091579(2).In addition,the O-C diagram reveals an increasing rate of period change for YZ Boo.Theoretical models are calculated and constrained with the observationally determined parameters of YZ Boo.The mass and age of YZ Boo are hence derived as M=1.61±0.05 M_⊙ and age=(1.44±0.14)×10~9 yr,respectively.With both the frequency of the fundamental radial mode and the rate of period change,YZ Boo is located at the post main sequence stage.展开更多
Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006. High-quality photometric data provided in the literature were used to analyze the pulsation of the star, with the derived ...Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006. High-quality photometric data provided in the literature were used to analyze the pulsation of the star, with the derived multiple frequencies fitted to our new data. Besides the dominant frequency and its harmonics, one low frequency (2.27402 c d -1) is discovered, which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light. Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature, we analyzed the long-term variability of AD CMi with the O - C technique. The results provide the updated value of period of 0.122974478 days, and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system, of which some parameters are hereby deduced.展开更多
In this work,the pulsation analysis is performed on 83 high-amplitudeδScuti stars(HADS),which have been observed by the Transiting Exoplanet Survey Satellite.The results show that 49 of these HADS show single-mode pu...In this work,the pulsation analysis is performed on 83 high-amplitudeδScuti stars(HADS),which have been observed by the Transiting Exoplanet Survey Satellite.The results show that 49 of these HADS show single-mode pulsation,27 of them show radial double-modes pulsation(in which 22 of them pulsate with the fundamental and first overtone modes and five of them pulsate with the first and second overtone modes),and seven of them show radial triple-modes pulsation(three of which are newly confirmed triple-mode HADS).The histogram of the fundamental periods and the ratios between the fundamental and first overtone periods show bimodal structures,which might be caused by the stellar evolution in this specific phase.Most of the radial triple-mode HADS have a fundamental amplitude of 41-54 mmag,and 50%of them have similar amplitudes of the fundamental and first overtone pulsation modes.All these hints require further confirmation not only in observations with more HADS samples,but also in theoretical models with suitable treatments of stellar evolution and pulsation.展开更多
Data representing 864 times of light maxima of the high-amplitude δ Scuti star CY Aqr were collected from the literature,based on which,long-term period changes of the variable star were investigated.A revised period...Data representing 864 times of light maxima of the high-amplitude δ Scuti star CY Aqr were collected from the literature,based on which,long-term period changes of the variable star were investigated.A revised period and new ephemerides were given for the pulsating star.Remarkable cyclic variations were found in the O-C residuals which can be attributed to the light-time effects due to probable unseen components of the object.By using Kopal's method,the orbital parameters of the supposed component stars were derived.The solution suggests that CY Aqr is very probably in a triple system orbited eccentrically by two low-mass companions with periods of 54.2 and 47.3 yr.The lower limits on masses were estimated as0.04 M_⊙and 0.02 M_⊙,respectively,for the two hidden companions.展开更多
The existence of pulsating stars in eclipsing binaries has been known for decades.These types of objects are extremely valuable systems for astronomical studies as they exhibit both eclipse and pulsation variations.Th...The existence of pulsating stars in eclipsing binaries has been known for decades.These types of objects are extremely valuable systems for astronomical studies as they exhibit both eclipse and pulsation variations.The eclipsing binaries are the only way to directly measure the mass and radius of stars with a good accuracy(≤1%),while the pulsations are a unique way to probe the stellar interior via oscillation frequencies.There are different types of pulsating stars existing in eclipsing binaries.One of them is theδScuti variables.Currently,the known number ofδScuti stars in eclipsing binaries is around 90 according to the latest catalog of these variables.An increasing number of these kinds of variables is important to understand the stellar structure,evolution and the effect of binarity on the pulsations.Therefore,in this study,we focus on discovering new eclipsing binaries withδScuti component(s).We searched within the northern Transiting Exoplanet Survey Satellite(TESS)field with a visual inspection by following some criteria such as light curve shape,the existence of pulsation like variations in the out-of-eclipse light curve and the T_(eff) values of the targets.As a result of these criteria,we discovered some targets.The orbital variations were first removed from the TESS light curves and frequency analysis was performed on the residuals.The luminosity,and absolute and bolometric magnitudes of the targets were calculated as well.To find how much of these parameters represent the primary(more luminous)binary component,we also computed the flux density ratio of the systems by utilizing the area of the eclipses.In addition,the positions of the systems in the H-R diagram were examined considering the flux density ratios.As a consequence of the investigation,we defined 38 candidateδScuti stars and also one Maia variable in eclipsing binary systems.展开更多
This paper reports analysis of an eclipsing binary system KIC 5197256 with aδSct variable component.Utilizing light-curve modeling,several stellar parameters are derived,e.g.,temperature,mass,and mass ratio.The O-C d...This paper reports analysis of an eclipsing binary system KIC 5197256 with aδSct variable component.Utilizing light-curve modeling,several stellar parameters are derived,e.g.,temperature,mass,and mass ratio.The O-C diagram is a straight line with a negative slope which means that its period is almost constant for about 2 yr.Frequency analyses are performed for the residual light curve after subtracting the binary variations.The frequency spectrum reveals that one component star is aδScuti variable.Large frequency separation is cross-identified with the histogram graph and the Fourier transform method.Based on the large separation and density relationship,the mean density of theδSct component is estimated to be 0.05 g·cm-3.Five frequencies with the same frequency spacing in the range of 25 d-1-34 d-1 are detected.Statistically,the pulsation amplitudes ofδSct stars increase with decreasing of rotations,so we propose that KIC 5197256 might have a relatively large rotational velocity,and the frequency f10 might be the rotation frequency.展开更多
New V-band CCD observations of variable star V2455 Cyg were performed during two nights in September 2017. According to all times of maximum light and new maxima, the O-C curve was analyzed.The period changes of V2455...New V-band CCD observations of variable star V2455 Cyg were performed during two nights in September 2017. According to all times of maximum light and new maxima, the O-C curve was analyzed.The period changes of V2455 Cyg were investigated and the rate of increasing period was obtained to be(1/P) d P/dt = 1.99 × 10^-7 yr-1. Frequency analysis indicated that V2455 Cyg pulsates with the radial p mode and the fundamental frequency is 10.61574 d-1. Physical parameters of V2455 Cyg at mean temperature were determined(e.g., R = 2.52 R⊙and M = 1.92 M⊙). The position of this star in the H-R diagram confirms that V2455 Cyg is a high amplitude δ Scuti star.展开更多
UV Tri was observed photometrically from 1999 to 2000 at the Xinglong Station of the National Astronomical Observatories, Chinese Academy of Sciences, and was also observed with Stromgren uvbyHβ filter system at the ...UV Tri was observed photometrically from 1999 to 2000 at the Xinglong Station of the National Astronomical Observatories, Chinese Academy of Sciences, and was also observed with Stromgren uvbyHβ filter system at the Sierra Nevada Observatory (Spain) in 2000. From period analyses of the data, three pulsation frequencies, 9.3299 c d-1 10.8483 cd-1 and 3.6035 cd-1 were obtained. We derived color indices: b - y = 0.215, m1 = 0.169, c1 = 0.783, and β = 2.775. With these indices and some calibrations, we obtain: Mv = 2.44, Mbol = 2.27, logL/L = 0.99, and log Teff = 3.875. Evolutionary sequences of stellar models with 1.00-2.00 solar masses, at steps of 0.05 M, are computed. Each sequence consists of 220 evolutionary intervals. From a comparison between the observed and calculated physical parameters we conclude that UV Thi is in an early evolutionary phase before the turn-off point.展开更多
This paper reports on the discovery that an eclipsing binary system, EPIC 202843107, has aδ Scuti variable component. The phased light curve from the Kepler space telescope presents a detached configuration. The bina...This paper reports on the discovery that an eclipsing binary system, EPIC 202843107, has aδ Scuti variable component. The phased light curve from the Kepler space telescope presents a detached configuration. The binary modeling indicates that the two component stars have almost the same radius and may have experienced orbital circularization. Frequency analyses are performed for the residual light curve after subtracting the binary variations. The frequency spectrum reveals that one component star is a δ Scuti variable. A large frequency separation is cross-identified with the corresponding histogram, the Fourier transform and the echelle diagram method. The mean density of the δ Scuti component is estimated to be 0.09 g cm-3 based on the large separation and density relation. Systems like EPIC 202843107 are helpful to study the stellar evolution and physical state of binary stars.展开更多
Intensive photometric and spectral observations of the variable star V2551 Cyg are presented.The light curve shape reveals that the target is a pulsating star, contrary to its previous classification as an eclipsing b...Intensive photometric and spectral observations of the variable star V2551 Cyg are presented.The light curve shape reveals that the target is a pulsating star, contrary to its previous classification as an eclipsing binary. The period and amplitude of the light curve, the amplitudes of color changes and the radial velocity curve of V2551 Cyg are similar to those of a high-amplitude δ Scuti variable. The target seems to pulsate with the fundamental mode. However, V2551 Cyg exhibits several important peculiarities:(i) the decreasing branch of its light curve is steeper than the increasing one;(ii) the radial velocity curve has a flat section in the phase range 0.7–1.2 and short increase of the negative radial velocity at phase 0.7;(iii) the rotational velocity is quite big for a HADS star;(iv) the Fourier coefficients of V2551 Cyg are quite different from those of HADS stars. The target classification is difficult due to these peculiarities.展开更多
We used the Nanshan 1 m telescope of Xinjiang Astronomical Observatory to investigate variable stars in the region of NGC 1245. We detected 55 variable stars in the field of view, 42 of them are newly discovered: six ...We used the Nanshan 1 m telescope of Xinjiang Astronomical Observatory to investigate variable stars in the region of NGC 1245. We detected 55 variable stars in the field of view, 42 of them are newly discovered: six binaries, 22 pulsating stars, 14 unclassified variables. We discussed the physical properties and classifications of the variable stars through their light curves. The cross-matching with the members catalog of NGC 1245 suggests that 10 variable stars are identified as probable cluster members, which including one EW type binary, eight δ Scuti stars, and an unknown type variable star. Since the difference of the members catalog of the cluster and the limitations of the instrument, there are some huge differences in the variable list of NGC 1245 compared with the previous work.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 is...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
Photometric results of three δ Scuti stars, AD Ari, IP Vir and YZ Boo from new observations obtained at the:Xinglong Station of the Beijing Astronom- ical Observatory (BAO) during 2000 aELd 2001 are reported. We pres...Photometric results of three δ Scuti stars, AD Ari, IP Vir and YZ Boo from new observations obtained at the:Xinglong Station of the Beijing Astronom- ical Observatory (BAO) during 2000 aELd 2001 are reported. We present here the preliminary analyses. Detailed studies of these stars based on additional data will be published separately.展开更多
基金support from the National Natural Science Foundation of China(NSFC,Grant No.11273051)partially supported by the Chinese Academy of Sciences(CAS) “Light of West China” program(2015-XBQN-A-02)+4 种基金supported by the Strategic Priority Research Program of CAS(Grant No.XDB23040100)support from the Joint Fund of Astronomy of NSFC and CAS(Grant U1231202 and 11673003)the National Basic Research Program of China(973 Program 2014CB845700 and 2013CB834900)the LAMOST FELLOWSHIP supported by Special Funding for Advanced Users,budgeted and administrated by the Center for Astronomical MegaScience,Chinese Academy of Sciences(CAMS)support from the NSFC(No.11403088)
文摘We present a study on pulsations of the high-amplitudeδScuti star YZ Boo based on photometric observations in Johnson V and R bands with both the Nanshan 1-m telescope of Xinjiang Astronomical Observatory(XAO)and the Xinglong 85-cm telescope of National Astronomical Observatories,Chinese Academy of Sciences(NAOC).Fourier analysis of the light curves reveals the fundamental radial mode and its five harmonics,with the fourth and fifth being newly detected.Thirtynine new times of maximum light are determined from the light curves,and combined with those in the literature,we construct the O-C diagram,derive a new ephemeris and determine a new value for the updated period of 0.104091579(2).In addition,the O-C diagram reveals an increasing rate of period change for YZ Boo.Theoretical models are calculated and constrained with the observationally determined parameters of YZ Boo.The mass and age of YZ Boo are hence derived as M=1.61±0.05 M_⊙ and age=(1.44±0.14)×10~9 yr,respectively.With both the frequency of the fundamental radial mode and the rate of period change,YZ Boo is located at the post main sequence stage.
基金the National Natural Science Foundation of China
文摘Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006. High-quality photometric data provided in the literature were used to analyze the pulsation of the star, with the derived multiple frequencies fitted to our new data. Besides the dominant frequency and its harmonics, one low frequency (2.27402 c d -1) is discovered, which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light. Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature, we analyzed the long-term variability of AD CMi with the O - C technique. The results provide the updated value of period of 0.122974478 days, and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system, of which some parameters are hereby deduced.
基金support from the National Natural Science Foundation of China(NSFC)(Nos.12005124 and 12147215)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)。
文摘In this work,the pulsation analysis is performed on 83 high-amplitudeδScuti stars(HADS),which have been observed by the Transiting Exoplanet Survey Satellite.The results show that 49 of these HADS show single-mode pulsation,27 of them show radial double-modes pulsation(in which 22 of them pulsate with the fundamental and first overtone modes and five of them pulsate with the first and second overtone modes),and seven of them show radial triple-modes pulsation(three of which are newly confirmed triple-mode HADS).The histogram of the fundamental periods and the ratios between the fundamental and first overtone periods show bimodal structures,which might be caused by the stellar evolution in this specific phase.Most of the radial triple-mode HADS have a fundamental amplitude of 41-54 mmag,and 50%of them have similar amplitudes of the fundamental and first overtone pulsation modes.All these hints require further confirmation not only in observations with more HADS samples,but also in theoretical models with suitable treatments of stellar evolution and pulsation.
基金supported by the National Natural Science Foundation of China (Nos.U1331121,11373037 and U1231202)
文摘Data representing 864 times of light maxima of the high-amplitude δ Scuti star CY Aqr were collected from the literature,based on which,long-term period changes of the variable star were investigated.A revised period and new ephemerides were given for the pulsating star.Remarkable cyclic variations were found in the O-C residuals which can be attributed to the light-time effects due to probable unseen components of the object.By using Kopal's method,the orbital parameters of the supposed component stars were derived.The solution suggests that CY Aqr is very probably in a triple system orbited eccentrically by two low-mass companions with periods of 54.2 and 47.3 yr.The lower limits on masses were estimated as0.04 M_⊙and 0.02 M_⊙,respectively,for the two hidden companions.
基金the Scientific and Technological Research Council(TUBITAK)under Grant No.120F330Funding for the TESS mission is provided by the NASA Explorer Program。
文摘The existence of pulsating stars in eclipsing binaries has been known for decades.These types of objects are extremely valuable systems for astronomical studies as they exhibit both eclipse and pulsation variations.The eclipsing binaries are the only way to directly measure the mass and radius of stars with a good accuracy(≤1%),while the pulsations are a unique way to probe the stellar interior via oscillation frequencies.There are different types of pulsating stars existing in eclipsing binaries.One of them is theδScuti variables.Currently,the known number ofδScuti stars in eclipsing binaries is around 90 according to the latest catalog of these variables.An increasing number of these kinds of variables is important to understand the stellar structure,evolution and the effect of binarity on the pulsations.Therefore,in this study,we focus on discovering new eclipsing binaries withδScuti component(s).We searched within the northern Transiting Exoplanet Survey Satellite(TESS)field with a visual inspection by following some criteria such as light curve shape,the existence of pulsation like variations in the out-of-eclipse light curve and the T_(eff) values of the targets.As a result of these criteria,we discovered some targets.The orbital variations were first removed from the TESS light curves and frequency analysis was performed on the residuals.The luminosity,and absolute and bolometric magnitudes of the targets were calculated as well.To find how much of these parameters represent the primary(more luminous)binary component,we also computed the flux density ratio of the systems by utilizing the area of the eclipses.In addition,the positions of the systems in the H-R diagram were examined considering the flux density ratios.As a consequence of the investigation,we defined 38 candidateδScuti stars and also one Maia variable in eclipsing binary systems.
基金supported by the National Natural Science Foundation of China(Grant No.U2031209)。
文摘This paper reports analysis of an eclipsing binary system KIC 5197256 with aδSct variable component.Utilizing light-curve modeling,several stellar parameters are derived,e.g.,temperature,mass,and mass ratio.The O-C diagram is a straight line with a negative slope which means that its period is almost constant for about 2 yr.Frequency analyses are performed for the residual light curve after subtracting the binary variations.The frequency spectrum reveals that one component star is aδScuti variable.Large frequency separation is cross-identified with the histogram graph and the Fourier transform method.Based on the large separation and density relationship,the mean density of theδSct component is estimated to be 0.05 g·cm-3.Five frequencies with the same frequency spacing in the range of 25 d-1-34 d-1 are detected.Statistically,the pulsation amplitudes ofδSct stars increase with decreasing of rotations,so we propose that KIC 5197256 might have a relatively large rotational velocity,and the frequency f10 might be the rotation frequency.
基金supported by the Department of Physics,Payame Noor University,Tehran,Iran。
文摘New V-band CCD observations of variable star V2455 Cyg were performed during two nights in September 2017. According to all times of maximum light and new maxima, the O-C curve was analyzed.The period changes of V2455 Cyg were investigated and the rate of increasing period was obtained to be(1/P) d P/dt = 1.99 × 10^-7 yr-1. Frequency analysis indicated that V2455 Cyg pulsates with the radial p mode and the fundamental frequency is 10.61574 d-1. Physical parameters of V2455 Cyg at mean temperature were determined(e.g., R = 2.52 R⊙and M = 1.92 M⊙). The position of this star in the H-R diagram confirms that V2455 Cyg is a high amplitude δ Scuti star.
基金the National NaturalScience Foundation of China fOr the research grants. ElOy Rodrfguez acknowIedges partialresearch suPport
文摘UV Tri was observed photometrically from 1999 to 2000 at the Xinglong Station of the National Astronomical Observatories, Chinese Academy of Sciences, and was also observed with Stromgren uvbyHβ filter system at the Sierra Nevada Observatory (Spain) in 2000. From period analyses of the data, three pulsation frequencies, 9.3299 c d-1 10.8483 cd-1 and 3.6035 cd-1 were obtained. We derived color indices: b - y = 0.215, m1 = 0.169, c1 = 0.783, and β = 2.775. With these indices and some calibrations, we obtain: Mv = 2.44, Mbol = 2.27, logL/L = 0.99, and log Teff = 3.875. Evolutionary sequences of stellar models with 1.00-2.00 solar masses, at steps of 0.05 M, are computed. Each sequence consists of 220 evolutionary intervals. From a comparison between the observed and calculated physical parameters we conclude that UV Thi is in an early evolutionary phase before the turn-off point.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11803012, 11333002, 11673011 and 11503009)the National Defense Science and Engineering Bureau Civil Space Flight Advanced Research Project (D030201)
文摘This paper reports on the discovery that an eclipsing binary system, EPIC 202843107, has aδ Scuti variable component. The phased light curve from the Kepler space telescope presents a detached configuration. The binary modeling indicates that the two component stars have almost the same radius and may have experienced orbital circularization. Frequency analyses are performed for the residual light curve after subtracting the binary variations. The frequency spectrum reveals that one component star is a δ Scuti variable. A large frequency separation is cross-identified with the corresponding histogram, the Fourier transform and the echelle diagram method. The mean density of the δ Scuti component is estimated to be 0.09 g cm-3 based on the large separation and density relation. Systems like EPIC 202843107 are helpful to study the stellar evolution and physical state of binary stars.
基金supported partly by project DN 08/20 of the Fund for Scientific Research of the Bulgarian Ministry of Education and Scienceproject RD 08-102 of Shumen University
文摘Intensive photometric and spectral observations of the variable star V2551 Cyg are presented.The light curve shape reveals that the target is a pulsating star, contrary to its previous classification as an eclipsing binary. The period and amplitude of the light curve, the amplitudes of color changes and the radial velocity curve of V2551 Cyg are similar to those of a high-amplitude δ Scuti variable. The target seems to pulsate with the fundamental mode. However, V2551 Cyg exhibits several important peculiarities:(i) the decreasing branch of its light curve is steeper than the increasing one;(ii) the radial velocity curve has a flat section in the phase range 0.7–1.2 and short increase of the negative radial velocity at phase 0.7;(iii) the rotational velocity is quite big for a HADS star;(iv) the Fourier coefficients of V2551 Cyg are quite different from those of HADS stars. The target classification is difficult due to these peculiarities.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.11763007,11863005,and U2031204)the program of Tianshan Youth(Nos.2017Q091,and 2017Q014)+1 种基金the Youth Innovation Promotion Association CAS(Grant No.2018080)the Natural Science Foundation of Xinjiang(No.2021D01C075).
文摘We used the Nanshan 1 m telescope of Xinjiang Astronomical Observatory to investigate variable stars in the region of NGC 1245. We detected 55 variable stars in the field of view, 42 of them are newly discovered: six binaries, 22 pulsating stars, 14 unclassified variables. We discussed the physical properties and classifications of the variable stars through their light curves. The cross-matching with the members catalog of NGC 1245 suggests that 10 variable stars are identified as probable cluster members, which including one EW type binary, eight δ Scuti stars, and an unknown type variable star. Since the difference of the members catalog of the cluster and the limitations of the instrument, there are some huge differences in the variable list of NGC 1245 compared with the previous work.
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.
文摘Photometric results of three δ Scuti stars, AD Ari, IP Vir and YZ Boo from new observations obtained at the:Xinglong Station of the Beijing Astronom- ical Observatory (BAO) during 2000 aELd 2001 are reported. We present here the preliminary analyses. Detailed studies of these stars based on additional data will be published separately.
