On January 20, 2017 Dr Aleksandar Kubičela, a doyen of astronomy in Serbia and one of the founders of astrophysical investigations at the Astronomical Observatory of Belgrade, passed away. Dr Aleksandar Kubičela (nickname Aks) was born on March 22, 1930 in Bela Crkva as the second child of father Djuro and mother Maria. He spent his childhood and finished his primary education in Bela Crkva (in 1941). After a break in education due to World War II, he finished high school (Gimnazija in Bela Crkva) on June 21, 1949, as an excellent student. He showed a great interest in astronomy and in the same year (1949), he moved to Belgrade, where he started to study astronomy (at the Faculty of Science of Belgrade University). However, his financial situation was very bad, and he had sought for a job (to finance his studies). Naturally, first he tried to find a job at the Astronomical Observatory of Belgrade and asked the authorities of Belgrade Observatory for such an opportunity. From documents at the Astronomical Observatory of Belgrade (Radovanac 2012) one can see that in the same year (1949) he was accepted upon his written request, to be employed at the Astronomical Observatory (as a student who is enrolled in the first year of the study of astronomy). He received a position of “Junior hydro-metheorogical technician” and started to work at the Observatory as well to study astronomy at the Faculty of Science of Belgrade University. In 1952, he received a position as “Hydrogeological technician”. From the archive of the Astronomical Observatory, it can be seen that he enlisted military service from September 1957 until November 1958, he again started to work at the Astronomical Observatory from November 15, 1958 as the “Technical staff” of the Observatory (Document 919/1 of the Astronomical Observatory issued on November 15, 1958), but now as a member of the Division for Solar activity. From the document (issued in 1960) about the work validation of the Astronomical Observatory staff (filled by A. Kubičela), it can be seen that he was involved in observations of variable stars, Sun
{"title":"Aleksandar Kubičcela (1930-2017) - An Astrophysical Research Pioneer at the Astronomical Observatory of Belgrade","authors":"L. Popović, I. Vince","doi":"10.2298/SAJ1896029P","DOIUrl":"https://doi.org/10.2298/SAJ1896029P","url":null,"abstract":"On January 20, 2017 Dr Aleksandar Kubičela, a doyen of astronomy in Serbia and one of the founders of astrophysical investigations at the Astronomical Observatory of Belgrade, passed away. Dr Aleksandar Kubičela (nickname Aks) was born on March 22, 1930 in Bela Crkva as the second child of father Djuro and mother Maria. He spent his childhood and finished his primary education in Bela Crkva (in 1941). After a break in education due to World War II, he finished high school (Gimnazija in Bela Crkva) on June 21, 1949, as an excellent student. He showed a great interest in astronomy and in the same year (1949), he moved to Belgrade, where he started to study astronomy (at the Faculty of Science of Belgrade University). However, his financial situation was very bad, and he had sought for a job (to finance his studies). Naturally, first he tried to find a job at the Astronomical Observatory of Belgrade and asked the authorities of Belgrade Observatory for such an opportunity. From documents at the Astronomical Observatory of Belgrade (Radovanac 2012) one can see that in the same year (1949) he was accepted upon his written request, to be employed at the Astronomical Observatory (as a student who is enrolled in the first year of the study of astronomy). He received a position of “Junior hydro-metheorogical technician” and started to work at the Observatory as well to study astronomy at the Faculty of Science of Belgrade University. In 1952, he received a position as “Hydrogeological technician”. From the archive of the Astronomical Observatory, it can be seen that he enlisted military service from September 1957 until November 1958, he again started to work at the Astronomical Observatory from November 15, 1958 as the “Technical staff” of the Observatory (Document 919/1 of the Astronomical Observatory issued on November 15, 1958), but now as a member of the Division for Solar activity. From the document (issued in 1960) about the work validation of the Astronomical Observatory staff (filled by A. Kubičela), it can be seen that he was involved in observations of variable stars, Sun","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"196 1","pages":"29-36"},"PeriodicalIF":0.5,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43236145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The aim of the paper is to present the digitization of the results of last observations of bright stars made by the Belgrade vertical circle ASKANIA N◦80118 (D = 190 mm, f = 2578 mm) at the Astronomical Observatory of Belgrade. The observations are mainly made by Djuro Bozhichkovich in the period between 1982 and 1985. All of the found observational data and intermediary results are referenced and presented and some research possibilities are suggested.
本文的目的是介绍贝尔格莱德天文台的贝尔格莱德垂直圆ASKANIA N◦80118 (D = 190 mm, f = 2578 mm)对明亮恒星的最后观测结果的数字化。这些观测主要是由Djuro Bozhichkovich在1982年至1985年期间进行的。本文参考并介绍了所有观测资料和中间结果，并提出了一些研究的可能性。
{"title":"Digitization of the Belgrade Astronomical Observatory's vertical circle observational heritage","authors":"S. Segan, M. Šegan-Radonjić","doi":"10.2298/SAJ1897035S","DOIUrl":"https://doi.org/10.2298/SAJ1897035S","url":null,"abstract":"The aim of the paper is to present the digitization of the results of last observations of bright stars made by the Belgrade vertical circle ASKANIA N◦80118 (D = 190 mm, f = 2578 mm) at the Astronomical Observatory of Belgrade. The observations are mainly made by Djuro Bozhichkovich in the period between 1982 and 1985. All of the found observational data and intermediary results are referenced and presented and some research possibilities are suggested.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"1 1","pages":"35-38"},"PeriodicalIF":0.5,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present photometric observations and transit solutions of the exoplanets XO-2b, HAT-P-18b and WASP 80b. Our solution of the XO-2b transit gave system parameters whose values are close to those of the previous studies. The solutions of the new transits of HAT-P-18b and WASP 80b differ from the previous ones by bigger stellar and planet radii. We obtained new values of the target initial epochs corresponding to slightly different periods. Our investigation reaffirmed that small telescopes can be used successfully for the study of exoplanets orbiting stars brighter than 13 mag.
{"title":"Observations and Modeling of the Transiting Exoplanets XO-2b, HAT-P-18b, and WASP-80b","authors":"D. Kjurkchieva, V. Popov, N. Petrov","doi":"10.2298/SAJ1795041K","DOIUrl":"https://doi.org/10.2298/SAJ1795041K","url":null,"abstract":"We present photometric observations and transit solutions of the exoplanets XO-2b, HAT-P-18b and WASP 80b. Our solution of the XO-2b transit gave system parameters whose values are close to those of the previous studies. The solutions of the new transits of HAT-P-18b and WASP 80b differ from the previous ones by bigger stellar and planet radii. We obtained new values of the target initial epochs corresponding to slightly different periods. Our investigation reaffirmed that small telescopes can be used successfully for the study of exoplanets orbiting stars brighter than 13 mag.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"195 1","pages":"41-46"},"PeriodicalIF":0.5,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48768227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
modified Fourier transform. The synthetic resonant proper elements adjusted to a given secular resonance helped to prove the existence of Astraea asteroid family. The preliminary assessment of stability with time of proper elements computed by means of the analytical theory provides a good indication of their poorer performance with respect to their synthetic counterparts, and advocates in favor of ceasing their
{"title":"Computation of Asteroid Proper Elements: Recent Advances","authors":"Z. Knežević","doi":"10.2298/SAJ170407005K","DOIUrl":"https://doi.org/10.2298/SAJ170407005K","url":null,"abstract":"modified Fourier transform. The synthetic resonant proper elements adjusted to a given secular resonance helped to prove the existence of Astraea asteroid family. The preliminary assessment of stability with time of proper elements computed by means of the analytical theory provides a good indication of their poorer performance with respect to their synthetic counterparts, and advocates in favor of ceasing their","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"194 1","pages":"1-8"},"PeriodicalIF":0.5,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49313320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A satellite orbiting around an isolated spherical planet with no atmosphere would indefinitely follow the same elliptic orbit, without any variation of the trajectory. However, for the case of real Earth this simple picture is greatly altered by perturbing forces, usually classified into two major groups: (i) Perturbations of the total gravity field that acts on the satellite. These effects can appear due to gravitational attraction of Sun and Moon (gravity effects of other celestial bodies are negligible), but also as a result of the variation of Earth’s gravitational attraction, caused by flattening at the poles and other departures from spherical symmetry, such as the ”pear-shape” effect. When analyzing satellite dynamics, the total gravity perturbation is considered to be the sum of all particular contributions, independent on the satellite mass, size or geometry. (ii) Non-gravitational effects, proportional to the area-to-mass ratio of the satellite. Here we primarily consider the air drag, caused by rapid movement of a satellite through the upper atmosphere, but also effects of the solar radiation pressure. For most satellites, these are two types of force that induce major perturbations in the orbits. Many other perturbations exist, but do not normally produce large changes and will therefore be ignored here, as we aim to provide basic description. These neglected perturbations appear, among other causes, due to: upper-atmosphere winds, solar radiation reflected from Earth, Earth tides and ocean tides, precession of the Earth’s axis in space, resonance with Earth’s gravitational field and relativity effects. Although these effects will be ignored, it should be noted that they can be important for some special satellites. Parameters of the satellite orbit and its motion are given in Table 1. Several elements in the table are not self-explanatory. First, the drag coefficient Cd is a parameter that describes aerodynamic properties and is determined by the satellite geometry. The model for calculation of this coefficient, which would widely be accepted in the community, still does not exist. Values in the interval 2.1-2.3 were obtained for spherical satellites by most of the
{"title":"Satellite orbit under influence of a drag - analytical approach","authors":"M. Martinović, S. Segan","doi":"10.2298/SAJ1795053M","DOIUrl":"https://doi.org/10.2298/SAJ1795053M","url":null,"abstract":"A satellite orbiting around an isolated spherical planet with no atmosphere would indefinitely follow the same elliptic orbit, without any variation of the trajectory. However, for the case of real Earth this simple picture is greatly altered by perturbing forces, usually classified into two major groups: (i) Perturbations of the total gravity field that acts on the satellite. These effects can appear due to gravitational attraction of Sun and Moon (gravity effects of other celestial bodies are negligible), but also as a result of the variation of Earth’s gravitational attraction, caused by flattening at the poles and other departures from spherical symmetry, such as the ”pear-shape” effect. When analyzing satellite dynamics, the total gravity perturbation is considered to be the sum of all particular contributions, independent on the satellite mass, size or geometry. (ii) Non-gravitational effects, proportional to the area-to-mass ratio of the satellite. Here we primarily consider the air drag, caused by rapid movement of a satellite through the upper atmosphere, but also effects of the solar radiation pressure. For most satellites, these are two types of force that induce major perturbations in the orbits. Many other perturbations exist, but do not normally produce large changes and will therefore be ignored here, as we aim to provide basic description. These neglected perturbations appear, among other causes, due to: upper-atmosphere winds, solar radiation reflected from Earth, Earth tides and ocean tides, precession of the Earth’s axis in space, resonance with Earth’s gravitational field and relativity effects. Although these effects will be ignored, it should be noted that they can be important for some special satellites. Parameters of the satellite orbit and its motion are given in Table 1. Several elements in the table are not self-explanatory. First, the drag coefficient Cd is a parameter that describes aerodynamic properties and is determined by the satellite geometry. The model for calculation of this coefficient, which would widely be accepted in the community, still does not exist. Values in the interval 2.1-2.3 were obtained for spherical satellites by most of the","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"195 1","pages":"53-58"},"PeriodicalIF":0.5,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43115962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Here, we compare the sunspot counts and the number of sunspot groups (SGs) with variations of total solar irradiance (TSI), magnetic activity, Ca II K-flux, faculae and plage areas. We applied a time series method for extracting the data over the descending phases of solar activity cycles (SACs) 21, 22 and 23, and the ascending phases 22 and 23. Our results suggest that there is a strong correlation between solar activity indices and the changes in small (A, B, C and H-modified Zurich Classification) and large (D, E and F) SGs. This somewhat unexpected finding suggests that plage regions substantially decreased in spite of the higher number of large SGs in SAC 23 while the Ca II K-flux did not decrease by a large amount nor was it comparable with SAC 22 and relates with C and DEF type SGs. In addition to this, the increase of facular areas which are influenced by large SGs, caused a small percentage decrease in TSI while the decrement of plage areas triggered a higher decrease in the magnetic field flux. Our results thus reveal the potential of such a detailed comparison of the SG analysis with solar activity indices for better understanding and predicting future trends in the SACs.
在这里，我们比较了太阳黑子数和太阳黑子群数(SGs)与太阳总辐照度(TSI)、磁活动、钙钾通量、光斑和斑块面积的变化。本文采用时间序列方法提取了太阳活动周期(SACs)第21、22和23下降阶段和第22和23上升阶段的数据。我们的研究结果表明，太阳活动指数与小(a、B、C和h修正的苏黎世分类)和大(D、E和F) SGs的变化有很强的相关性。这一出人意料的发现表明，尽管SAC 23的大SGs数量较多，但斑块区域大幅减少，而Ca II k -通量没有大量减少，也与SAC 22没有可比性，与C型和DEF型SGs有关。此外，受大SGs影响的光斑面积的增加导致TSI的百分比下降较小，而斑块面积的减少导致磁场通量的较大下降。因此，我们的研究结果揭示了将SG分析与太阳活动指数进行详细比较的潜力，可以更好地理解和预测sac的未来趋势。
{"title":"Temporal variations of different solar activity indices through the solar cycles 21-23","authors":"Ü. Göker, Jagdev Singh, Ferhat Nutku, Muthu Priyal","doi":"10.2298/SAJ1795059G","DOIUrl":"https://doi.org/10.2298/SAJ1795059G","url":null,"abstract":"Here, we compare the sunspot counts and the number of sunspot groups (SGs) with variations of total solar irradiance (TSI), magnetic activity, Ca II K-flux, faculae and plage areas. We applied a time series method for extracting the data over the descending phases of solar activity cycles (SACs) 21, 22 and 23, and the ascending phases 22 and 23. Our results suggest that there is a strong correlation between solar activity indices and the changes in small (A, B, C and H-modified Zurich Classification) and large (D, E and F) SGs. This somewhat unexpected finding suggests that plage regions substantially decreased in spite of the higher number of large SGs in SAC 23 while the Ca II K-flux did not decrease by a large amount nor was it comparable with SAC 22 and relates with C and DEF type SGs. In addition to this, the increase of facular areas which are influenced by large SGs, caused a small percentage decrease in TSI while the decrement of plage areas triggered a higher decrease in the magnetic field flux. Our results thus reveal the potential of such a detailed comparison of the SG analysis with solar activity indices for better understanding and predicting future trends in the SACs.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"195 1","pages":"59-70"},"PeriodicalIF":0.5,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48423772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Pannuti, M. Filipović, K. Luken, G. Wong, P. Manojlović, N. Maxted, Q. Roper
We present an analysis of X-ray observations made with ASCA and XMM-Newton of the Galactic supernova remnant (SNR) G311.5−0.3. Prior infrared and radio observations of this SNR have revealed a shell-like morphology at both wavelengths. The spectral index of the radio emission is consistent with synchrotron emission, while the infrared colors are consistent with emission from shocked molecular hydrogen. Also previous CO observations have indicated an interaction between G311.5−0.3 and an adjacent molecular cloud. Our previous analysis of the pointed ASCA observation made of this SNR detected X-ray emission from the source for the first time but lacked the sensitivity and the angular resolution to rigorously investigate its X-ray properties. We have analyzed an archival XMM-Newton observation that included G311.5−0.3 in the field of view: this is the first time that XMM-Newton data has been used to probe the X-ray properties of this SNR. The XMM-Newton observation confirms that the X-ray emission from G311.5−0.3 is centrally concentrated and supports the classification of this source as a mixed-morphology SNR. In addition, our joint fitting of extracted ASCA and XMM-Newton spectra favor a thermal origin for the X-ray emission over a non-thermal origin. The spectral fitting parameters for our TBABS×APEC fit to the extracted spectra are NH = 4.63 +1.87 −0.85×10 cm−2 and kT = 0.68 −0.24 keV. From these fit parameters, we derive the following values for physical parameters of the SNR: ne = 0.20 cm −3, np = 0.17 cm−3, MX = 21.4 M and P/k = 3.18×106 K cm−3.
我们对银河系超新星遗迹(SNR) G311.5−0.3的ASCA和XMM-Newton x射线观测结果进行了分析。先前对该信噪比的红外和射电观测在两个波长上都揭示了贝壳状的形态。射电发射的光谱指数与同步加速器发射一致，而红外颜色与受激氢分子的发射一致。此外，先前的CO观测表明G311.5−0.3与相邻的分子云之间存在相互作用。我们之前对该SNR的点ASCA观测进行的分析首次检测到源的x射线发射，但缺乏灵敏度和角分辨率来严格研究其x射线性质。我们分析了一个包含G311.5−0.3视场的xmm -牛顿观测档案:这是xmm -牛顿数据第一次被用于探测该信噪比的x射线特性。XMM-Newton观测证实了G311.5−0.3的x射线辐射是中心集中的，支持了该源的混合形态信噪比分类。此外，我们对提取的ASCA和XMM-Newton光谱的联合拟合更倾向于热源而不是非热源的x射线发射。我们的TBABS×APEC与提取光谱的拟合参数为NH = 4.63 +1.87−0.85×10 cm−2,kT = 0.68−0.24 keV。从这些拟合参数中，我们得到了信噪比的物理参数如下值:ne = 0.20 cm - 3, np = 0.17 cm - 3, MX = 21.4 M, P/k = 3.18×106 k cm - 3。
{"title":"ASCA and XMM-Newton Observations of the Galactic Supernova Remnant G311.5-0.3","authors":"T. Pannuti, M. Filipović, K. Luken, G. Wong, P. Manojlović, N. Maxted, Q. Roper","doi":"10.2298/SAJ1795023P","DOIUrl":"https://doi.org/10.2298/SAJ1795023P","url":null,"abstract":"We present an analysis of X-ray observations made with ASCA and XMM-Newton of the Galactic supernova remnant (SNR) G311.5−0.3. Prior infrared and radio observations of this SNR have revealed a shell-like morphology at both wavelengths. The spectral index of the radio emission is consistent with synchrotron emission, while the infrared colors are consistent with emission from shocked molecular hydrogen. Also previous CO observations have indicated an interaction between G311.5−0.3 and an adjacent molecular cloud. Our previous analysis of the pointed ASCA observation made of this SNR detected X-ray emission from the source for the first time but lacked the sensitivity and the angular resolution to rigorously investigate its X-ray properties. We have analyzed an archival XMM-Newton observation that included G311.5−0.3 in the field of view: this is the first time that XMM-Newton data has been used to probe the X-ray properties of this SNR. The XMM-Newton observation confirms that the X-ray emission from G311.5−0.3 is centrally concentrated and supports the classification of this source as a mixed-morphology SNR. In addition, our joint fitting of extracted ASCA and XMM-Newton spectra favor a thermal origin for the X-ray emission over a non-thermal origin. The spectral fitting parameters for our TBABS×APEC fit to the extracted spectra are NH = 4.63 +1.87 −0.85×10 cm−2 and kT = 0.68 −0.24 keV. From these fit parameters, we derive the following values for physical parameters of the SNR: ne = 0.20 cm −3, np = 0.17 cm−3, MX = 21.4 M and P/k = 3.18×106 K cm−3.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"195 1","pages":"23-31"},"PeriodicalIF":0.5,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47250353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The importance of the Lagrangian points as possible locations for large space stations, which can be utilized in interplanetary navigation, much increases as time advances. This requires an accurate analysis of locations and linear stability of these points. The linear stability of triangular points was examined in several studies [see Musielak and Quarles (2014) for a review]. Bhatnagar and Hallan (1998) studied the linear stability of relativistic triangular points. They found that these points are unstable for the range of mass ratio 0 ≤ μ ≤ 0.5, despite the fact that the non-relativistic triangular points are stable for μ < μ0 = 0.03852, where μ0 is the Routh critical mass ratio. The same problem was revisited by Douskos and Perdios (2002) and Ahmed et al. (2006) whose results showed that the relativistic triangular points are linearly stable in the range of mass ratios less than a critical value μc, i.e. 0 ≤ μ < μc. This critical value was estimated by Douskos and Perdios (2002) to be μc = μ0 − 17 √ 69/486c while Ahmed et al. (2006) calculated it to be μc = 0.03840. Palit et al. (2009) analyzed the stability of circular orbits in the Schwarzschild-de Sitter spacetime. Yamada and Asada (2010) computed the relativistic corrections to the Sun-Jupiter libration points. Also, Yamada and Asada (2011) continued their work and investigated collinear solutions to the general relativistic three-body problem. They proved the uniqueness of the configuration for given system parameters (the masses and the end-to-end length). Ichita et al. (2011) investigated the postNewtonian effects on Lagrange’s equilateral triangular solution for the three-body problem. For three finite masses, they found that the equilateral triangular configuration satisfies the post-Newtonian equation of motion in general relativity if and only if all three masses are equal. The post-Newtonian effects on Lagrange’s equilateral triangular solution for the three-body problem were re-examined by Yamada
{"title":"On stability of triangular points of the restricted relativistic elliptic three-body problem with triaxial and oblate primaries","authors":"K. Zahra, Z. Awad, H. Dwidar, M. Radwan","doi":"10.2298/SAJ1795047Z","DOIUrl":"https://doi.org/10.2298/SAJ1795047Z","url":null,"abstract":"The importance of the Lagrangian points as possible locations for large space stations, which can be utilized in interplanetary navigation, much increases as time advances. This requires an accurate analysis of locations and linear stability of these points. The linear stability of triangular points was examined in several studies [see Musielak and Quarles (2014) for a review]. Bhatnagar and Hallan (1998) studied the linear stability of relativistic triangular points. They found that these points are unstable for the range of mass ratio 0 ≤ μ ≤ 0.5, despite the fact that the non-relativistic triangular points are stable for μ < μ0 = 0.03852, where μ0 is the Routh critical mass ratio. The same problem was revisited by Douskos and Perdios (2002) and Ahmed et al. (2006) whose results showed that the relativistic triangular points are linearly stable in the range of mass ratios less than a critical value μc, i.e. 0 ≤ μ < μc. This critical value was estimated by Douskos and Perdios (2002) to be μc = μ0 − 17 √ 69/486c while Ahmed et al. (2006) calculated it to be μc = 0.03840. Palit et al. (2009) analyzed the stability of circular orbits in the Schwarzschild-de Sitter spacetime. Yamada and Asada (2010) computed the relativistic corrections to the Sun-Jupiter libration points. Also, Yamada and Asada (2011) continued their work and investigated collinear solutions to the general relativistic three-body problem. They proved the uniqueness of the configuration for given system parameters (the masses and the end-to-end length). Ichita et al. (2011) investigated the postNewtonian effects on Lagrange’s equilateral triangular solution for the three-body problem. For three finite masses, they found that the equilateral triangular configuration satisfies the post-Newtonian equation of motion in general relativity if and only if all three masses are equal. The post-Newtonian effects on Lagrange’s equilateral triangular solution for the three-body problem were re-examined by Yamada","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"195 1","pages":"47-52"},"PeriodicalIF":0.5,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42197169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We carried out light curve solutions of four detached binaries observed by Kepler. As a result, their orbital inclinations, temperatures and relative stellar radii were determined. KIC 10031409 and KIC 11228612 reveal partial eclipses while the components of KIC 11403216 and KIC 11913071 undergo total eclipses. The secondary component of KIC 11403216 is probably a very late M dwarf or brown dwarf. The out-of-eclipse brightness of KIC 10031409, KIC 11228612 and KIC 11913071 vary with the orbital period and might be explained by spots on synchronously-rotating star(s). The out-of-eclipse variability of KIC 11403216 is with a period that is a third of its orbital period and may be due to spot on asynchronous rotating component. The resonance 1:3 needs future study of KIC 11403216.
{"title":"Light Curve Solutions and Out-of-Eclipse Variability of KIC 10031409, KIC 11228612, KIC 11403216 and KIC 11913071","authors":"D. Kjurkchieva, T. Atanasova","doi":"10.2298/SAJ1795033K","DOIUrl":"https://doi.org/10.2298/SAJ1795033K","url":null,"abstract":"We carried out light curve solutions of four detached binaries observed by Kepler. As a result, their orbital inclinations, temperatures and relative stellar radii were determined. KIC 10031409 and KIC 11228612 reveal partial eclipses while the components of KIC 11403216 and KIC 11913071 undergo total eclipses. The secondary component of KIC 11403216 is probably a very late M dwarf or brown dwarf. The out-of-eclipse brightness of KIC 10031409, KIC 11228612 and KIC 11913071 vary with the orbital period and might be explained by spots on synchronously-rotating star(s). The out-of-eclipse variability of KIC 11403216 is with a period that is a third of its orbital period and may be due to spot on asynchronous rotating component. The resonance 1:3 needs future study of KIC 11403216.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"195 1","pages":"33-39"},"PeriodicalIF":0.5,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43475276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper we present results of the spectroscopic analysis of H$alpha$ line profile of the Be star 60 Cygni. We present time evolution of the equivalent width of the H$alpha$ line profiles during years 1992 - 2016 and $V/R$ variation during years 1995 - 2016. We analyzed data from Ondřejov Observatory and from BeSS Database. The circumstellar disk of the star was present twice during years 1992 - 2016 and the second cycle shows stronger emission activity. We found out that the formation of the disk takes longer time than the disk extinction (extinction is much steeper than the formation) and that there is no evident period of changes in $V/R$ variation.
{"title":"Emission activity of the Be star 60 Cygni","authors":"Klára Šejnová, V. Votruba","doi":"10.2298/SAJ1794051S","DOIUrl":"https://doi.org/10.2298/SAJ1794051S","url":null,"abstract":"In this paper we present results of the spectroscopic analysis of H$alpha$ line profile of the Be star 60 Cygni. We present time evolution of the equivalent width of the H$alpha$ line profiles during years 1992 - 2016 and $V/R$ variation during years 1995 - 2016. We analyzed data from Ondřejov Observatory and from BeSS Database. The circumstellar disk of the star was present twice during years 1992 - 2016 and the second cycle shows stronger emission activity. We found out that the formation of the disk takes longer time than the disk extinction (extinction is much steeper than the formation) and that there is no evident period of changes in $V/R$ variation.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"2017 1","pages":"51-57"},"PeriodicalIF":0.5,"publicationDate":"2017-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48374099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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