First business: to clean a tea pot. Income: RMB 0.20 (less than 10 US cents at the time). Second business: to clean a boiler. Income: RMB 1, 200. Three months later, incomereached RMB 240, 000. Ten years later, the co...First business: to clean a tea pot. Income: RMB 0.20 (less than 10 US cents at the time). Second business: to clean a boiler. Income: RMB 1, 200. Three months later, incomereached RMB 240, 000. Ten years later, the company had 350 subsidiaries across China and four joint ventures abroad, with an annual output value of more than RMB 300 million. The data are simple but intriguing, recording the history of the Blue展开更多
A grid of binary evolution models are calculated for the study of a blue straggler （BS） population in intermediate age （log Age = 7.85 - 8.95） star clusters. The BS formation via mass transfer and merging is studi...A grid of binary evolution models are calculated for the study of a blue straggler （BS） population in intermediate age （log Age = 7.85 - 8.95） star clusters. The BS formation via mass transfer and merging is studied systematically using our models. Both Case A and B close binary evolutionary tracks are calculated for a large range of parameters. The results show that BSs formed via Case B are generally bluer and even more luminous than those produced by Case A. Furthermore, the larger range in orbital separations of Case B models provides a probability of producing more BSs than in Case A. Based on the grid of models, several Monte-Carlo simulations of BS populations in the clusters in the age range are carded out. The results show that BSs formed via different channels populate different areas in the color magnitude diagram （CMD）. The locations of BSs in CMD for a number of clusters are compared to our simulations as well. In order to investigate the influence of mass transfer efficiency in the models and simulations, a set of models is also calculated by implementing a constant mass transfer efficiency,β=0.5, during Roche lobe overflow （Case A binary evolution excluded）. The result shows BSs can be formed via mass transfer at any given age in both cases. However, the distributions of the BS populations on CMD are different.展开更多
Based on the turbulent convection model （TCM）, we investigate chemical mixing in the bottom overshooting region of the convective envelope of intermediatemass stars, focusing on its influence on the formation and ex...Based on the turbulent convection model （TCM）, we investigate chemical mixing in the bottom overshooting region of the convective envelope of intermediatemass stars, focusing on its influence on the formation and extension of blue loops in the Hertzsprung-Russell （HR） diagram. A diffusive mixing model is adopted during the Red Giant Branch （RGB） phase. The properties of the blue loop are changed by modification of the element profiles above the H-burning shell, which results from the incomplete mixing in the bottom overshooting region when the stellar model evolves up along the RGB. Such modification of the element profiles will lead to an increase of opacity in the region just above the H-burning shell and a decrease of opacity in the outer homogeneous convection zone, which will result in a quick decrease of the H-shell nuclear luminosity LH when the stellar model evolves from the RGB tip to its bottom and, finally, a much weaker and smaller convection zone will be obtained in the stellar envelope. This helps to form a longer blue loop. The extension of the blue loop is very sensitive to the parameters （Cx and αTCM） of the diffusive mixing model and of the TCM. The results mainly show that： 1） comparing the results of the classical model with the mixing-length theory, the lengths of the obtained blue loops with different combinations of the values of Cx and αTCM are all increased and the length of the blue loop increases with the values of parameters Cx and αTCM; 2） the diffusive mixing model can significantly extend the time of stellar models lingering on the blue side of the HR diagram, even though the length of the blue loop for the 7M⊙ star has a less prominent difference between the classical and diffusive mixing model; 3） both the observations referring to the location of the Cepheid instability strip and the number ratio NB/NR of blue to red evolved stars in the Galactic open clusters can confine the two parameters in a range of 0.5 ≤ αLTCM ≤ 0.9 and 10-5 ≤ Cx ≤ 10-4 for the model of 5M⊙. However, for the case of the 7M⊙ star, there seems to be no such definite range to even only account for the observed number ratio NB/NR. In any case, our results based on the diffusive mixing model are on the whole in accordance with not only other theoretical ones but also the observations.展开更多
We present results of a time-series CCD photometry of two blue stragglers in the open cluster M67 that are also oscillating variables, S1280 and S1284. The observations obtained on 11 nights confirmed the δ Scuti-lik...We present results of a time-series CCD photometry of two blue stragglers in the open cluster M67 that are also oscillating variables, S1280 and S1284. The observations obtained on 11 nights confirmed the δ Scuti-like variability of the two stars. Four and five main pulsating frequencies are detected for S1280 and S1284, respectively, through a power spectral analysis. A preliminary mode identification indicates that the two stars are both in radial oscillation. Based on the nature of oscillation, the physical parameters of the two stars are determined, and their evolutionary status discussed.展开更多
In this study,we investigated the optimal concentration of nutrient-mist and NaHSO3 for cutting propagation of Juniperus squamata ’Blue Star’,as well as the variation in the contents of chlorophyll in leaves,and sol...In this study,we investigated the optimal concentration of nutrient-mist and NaHSO3 for cutting propagation of Juniperus squamata ’Blue Star’,as well as the variation in the contents of chlorophyll in leaves,and solubility carbohydrate,soluble protein and other nutrition in leaves and bases of cuttings during rooting.Cuttings of grade Ⅲ(the lenghth of cutting bases lignified from 0.1 to 0.2 cm) was treated by 1/4MS+NaHSO3(200 mg·L-1),and the rooting rate rose 35% and root qualities were improved compared with control experiment,for there were different effects among three grade cuttings.The treatment of grade Ⅲ cuttings also resulted in higher content of soluble sugar and starch of those bases during rooting,especially obviously different for fifteen days,but less effect on the chlorophyll and some nutrition content of cutting leaves.展开更多
We analyzed the B and V light curves of two EA-type binaries V211 and NV358 for the first time using the Wilson-Devinney code. Our analysis shows that V211 is a typical Algol-type binary and NV358 is a well detached b...We analyzed the B and V light curves of two EA-type binaries V211 and NV358 for the first time using the Wilson-Devinney code. Our analysis shows that V211 is a typical Algol-type binary and NV358 is a well detached binary system. As the two binaries are definite members of ω Centauri due to their proper motion, we estimated their physical parameters, obtaining M1 = 1.13 4±0.03 M⊙, R1 = 0.98±0.01 R⊙, M2 = 0.33 ±0.01 M⊙ and R2 = 0.92 ±0.01 R⊙ forV211; M1 = 1.304-0.05 M⊙, R1 = 1.03±0.01 R⊙, M2 = 0.58±0.02 M⊙ and R2 = 0.78±0.01 R⊙ for NV358. On the color-magnitude diagram of ω Centauri, V211 is located in the faint blue straggler region and its primary component is more massive than a star at the main-sequence turnoff. Therefore, V211 is a blue straggler and was formed by mass transfer from the secondary component to the primary. The age of NV358 is less than 1.93 Gyr, indicating that it is much younger than the first generation of stars in ω Centaufi. Like NV364 in ω Centaufi, NV358 should be a second-generation binary.展开更多
The Ultra Violet Imaging Telescope （UVIT） is one of the payloads on the first Indian multiwavelength satellite ASTROSAT, which is expected to be launched by the Indian Space Research Organisation （ISRO） in the yea...The Ultra Violet Imaging Telescope （UVIT） is one of the payloads on the first Indian multiwavelength satellite ASTROSAT, which is expected to be launched by the Indian Space Research Organisation （ISRO） in the year 2015. We have per- formed simulations of UV studies of old open clusters for the UVIT. The colour mag- nitude diagrams （CMDs） and spatial appearances have been created using 10 filters associated with the FUV channel （130-180 nm） and NUV channel （200-300 nm） that are available for observations on the UVIT, for the three old open clusters M67, NGC 188 and NGC 6791. The CMDs are simulated for different filter combinations, and they are used to identify the loci of various evolutionary sequences, white dwarfs, blue stragglers, red giants, subgiants, turn off stars and the main sequence of the clus- ters. The present work helps in identifying a potential area of study in the case of these three old open clusters by considering the availability of filters and the detection limits of the instrument. We also recommend filter combinations, which can be used to detect and study the above mentioned evolutionary stages. The simulations and the results presented here are essential for the optimal use of the UVIT for studies of old open clusters.展开更多
We have studied the influence of different choices of core-envelope transition point on the final merger of contact binaries with two main-sequence components. A binary of 1.00 + 0.90M⊙ with an initial orbital period...We have studied the influence of different choices of core-envelope transition point on the final merger of contact binaries with two main-sequence components. A binary of 1.00 + 0.90M⊙ with an initial orbital period of 0.35d is examined. The mass fraction of the primary mixed with the matter of the secondary, qmix, determined by the chosen core-envelope transition point, ranges from 0.04 to 1.00 in our analysis. If as qmix< 0.8, none of the helium-rich matter in the center of the primary is mixed into the envelope, and there is little distinction in the evolutionary tracks of the mergers. The timescales of the mergers remaining on the main sequence, tBS are very similar (-6.2×108yr) if qmix< 0.71, since no hydrogen-rich matter of the secondary is mixed into the core of the mergers; for qmix > 0.71, the larger qmix is, the greater the mixing, hence the longer the blue straggler lifetime, tBS, and also the greater the luminosity. For qmix= 1.00, tBS -8.5×108yr. Estimation by (?)r - (?)a = 0.0 shows that the point at which tBS begins to increase is about qmix= 0.68. In comparison with the homogeneously mixed models, the merger with a helium profile similar to that of the primary is less luminous and has a shorter tBS.展开更多
文摘First business: to clean a tea pot. Income: RMB 0.20 (less than 10 US cents at the time). Second business: to clean a boiler. Income: RMB 1, 200. Three months later, incomereached RMB 240, 000. Ten years later, the company had 350 subsidiaries across China and four joint ventures abroad, with an annual output value of more than RMB 300 million. The data are simple but intriguing, recording the history of the Blue
基金supported by the National Natural Science Foundation of China(Grant Nos.10973015,10773015 and 11061120454)
文摘A grid of binary evolution models are calculated for the study of a blue straggler （BS） population in intermediate age （log Age = 7.85 - 8.95） star clusters. The BS formation via mass transfer and merging is studied systematically using our models. Both Case A and B close binary evolutionary tracks are calculated for a large range of parameters. The results show that BSs formed via Case B are generally bluer and even more luminous than those produced by Case A. Furthermore, the larger range in orbital separations of Case B models provides a probability of producing more BSs than in Case A. Based on the grid of models, several Monte-Carlo simulations of BS populations in the clusters in the age range are carded out. The results show that BSs formed via different channels populate different areas in the color magnitude diagram （CMD）. The locations of BSs in CMD for a number of clusters are compared to our simulations as well. In order to investigate the influence of mass transfer efficiency in the models and simulations, a set of models is also calculated by implementing a constant mass transfer efficiency,β=0.5, during Roche lobe overflow （Case A binary evolution excluded）. The result shows BSs can be formed via mass transfer at any given age in both cases. However, the distributions of the BS populations on CMD are different.
基金supported by the National Natural Science Foundation of China(Grant Nos.10973035 and 10673030)
文摘Based on the turbulent convection model （TCM）, we investigate chemical mixing in the bottom overshooting region of the convective envelope of intermediatemass stars, focusing on its influence on the formation and extension of blue loops in the Hertzsprung-Russell （HR） diagram. A diffusive mixing model is adopted during the Red Giant Branch （RGB） phase. The properties of the blue loop are changed by modification of the element profiles above the H-burning shell, which results from the incomplete mixing in the bottom overshooting region when the stellar model evolves up along the RGB. Such modification of the element profiles will lead to an increase of opacity in the region just above the H-burning shell and a decrease of opacity in the outer homogeneous convection zone, which will result in a quick decrease of the H-shell nuclear luminosity LH when the stellar model evolves from the RGB tip to its bottom and, finally, a much weaker and smaller convection zone will be obtained in the stellar envelope. This helps to form a longer blue loop. The extension of the blue loop is very sensitive to the parameters （Cx and αTCM） of the diffusive mixing model and of the TCM. The results mainly show that： 1） comparing the results of the classical model with the mixing-length theory, the lengths of the obtained blue loops with different combinations of the values of Cx and αTCM are all increased and the length of the blue loop increases with the values of parameters Cx and αTCM; 2） the diffusive mixing model can significantly extend the time of stellar models lingering on the blue side of the HR diagram, even though the length of the blue loop for the 7M⊙ star has a less prominent difference between the classical and diffusive mixing model; 3） both the observations referring to the location of the Cepheid instability strip and the number ratio NB/NR of blue to red evolved stars in the Galactic open clusters can confine the two parameters in a range of 0.5 ≤ αLTCM ≤ 0.9 and 10-5 ≤ Cx ≤ 10-4 for the model of 5M⊙. However, for the case of the 7M⊙ star, there seems to be no such definite range to even only account for the observed number ratio NB/NR. In any case, our results based on the diffusive mixing model are on the whole in accordance with not only other theoretical ones but also the observations.
文摘We present results of a time-series CCD photometry of two blue stragglers in the open cluster M67 that are also oscillating variables, S1280 and S1284. The observations obtained on 11 nights confirmed the δ Scuti-like variability of the two stars. Four and five main pulsating frequencies are detected for S1280 and S1284, respectively, through a power spectral analysis. A preliminary mode identification indicates that the two stars are both in radial oscillation. Based on the nature of oscillation, the physical parameters of the two stars are determined, and their evolutionary status discussed.
文摘In this study,we investigated the optimal concentration of nutrient-mist and NaHSO3 for cutting propagation of Juniperus squamata ’Blue Star’,as well as the variation in the contents of chlorophyll in leaves,and solubility carbohydrate,soluble protein and other nutrition in leaves and bases of cuttings during rooting.Cuttings of grade Ⅲ(the lenghth of cutting bases lignified from 0.1 to 0.2 cm) was treated by 1/4MS+NaHSO3(200 mg·L-1),and the rooting rate rose 35% and root qualities were improved compared with control experiment,for there were different effects among three grade cuttings.The treatment of grade Ⅲ cuttings also resulted in higher content of soluble sugar and starch of those bases during rooting,especially obviously different for fifteen days,but less effect on the chlorophyll and some nutrition content of cutting leaves.
基金partly supported by the National Natural Science Foundation of China(Grant Nos. 11203066, 11133007, 11103074, 10973037 and 10903026)by the West Light Foundation of the Chinese Academy of Sciences
文摘We analyzed the B and V light curves of two EA-type binaries V211 and NV358 for the first time using the Wilson-Devinney code. Our analysis shows that V211 is a typical Algol-type binary and NV358 is a well detached binary system. As the two binaries are definite members of ω Centauri due to their proper motion, we estimated their physical parameters, obtaining M1 = 1.13 4±0.03 M⊙, R1 = 0.98±0.01 R⊙, M2 = 0.33 ±0.01 M⊙ and R2 = 0.92 ±0.01 R⊙ forV211; M1 = 1.304-0.05 M⊙, R1 = 1.03±0.01 R⊙, M2 = 0.58±0.02 M⊙ and R2 = 0.78±0.01 R⊙ for NV358. On the color-magnitude diagram of ω Centauri, V211 is located in the faint blue straggler region and its primary component is more massive than a star at the main-sequence turnoff. Therefore, V211 is a blue straggler and was formed by mass transfer from the secondary component to the primary. The age of NV358 is less than 1.93 Gyr, indicating that it is much younger than the first generation of stars in ω Centaufi. Like NV364 in ω Centaufi, NV358 should be a second-generation binary.
文摘The Ultra Violet Imaging Telescope （UVIT） is one of the payloads on the first Indian multiwavelength satellite ASTROSAT, which is expected to be launched by the Indian Space Research Organisation （ISRO） in the year 2015. We have per- formed simulations of UV studies of old open clusters for the UVIT. The colour mag- nitude diagrams （CMDs） and spatial appearances have been created using 10 filters associated with the FUV channel （130-180 nm） and NUV channel （200-300 nm） that are available for observations on the UVIT, for the three old open clusters M67, NGC 188 and NGC 6791. The CMDs are simulated for different filter combinations, and they are used to identify the loci of various evolutionary sequences, white dwarfs, blue stragglers, red giants, subgiants, turn off stars and the main sequence of the clus- ters. The present work helps in identifying a potential area of study in the case of these three old open clusters by considering the availability of filters and the detection limits of the instrument. We also recommend filter combinations, which can be used to detect and study the above mentioned evolutionary stages. The simulations and the results presented here are essential for the optimal use of the UVIT for studies of old open clusters.
文摘We have studied the influence of different choices of core-envelope transition point on the final merger of contact binaries with two main-sequence components. A binary of 1.00 + 0.90M⊙ with an initial orbital period of 0.35d is examined. The mass fraction of the primary mixed with the matter of the secondary, qmix, determined by the chosen core-envelope transition point, ranges from 0.04 to 1.00 in our analysis. If as qmix< 0.8, none of the helium-rich matter in the center of the primary is mixed into the envelope, and there is little distinction in the evolutionary tracks of the mergers. The timescales of the mergers remaining on the main sequence, tBS are very similar (-6.2×108yr) if qmix< 0.71, since no hydrogen-rich matter of the secondary is mixed into the core of the mergers; for qmix > 0.71, the larger qmix is, the greater the mixing, hence the longer the blue straggler lifetime, tBS, and also the greater the luminosity. For qmix= 1.00, tBS -8.5×108yr. Estimation by (?)r - (?)a = 0.0 shows that the point at which tBS begins to increase is about qmix= 0.68. In comparison with the homogeneously mixed models, the merger with a helium profile similar to that of the primary is less luminous and has a shorter tBS.
