Serbian Astronomical Journal最新文献

{"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":null,"pages":null},"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}

{"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":null,"pages":null},"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}

{"title":"Relative-coordinate determination for visual double stars by applying Fourier transforms","authors":"Viktor Radović, R. Pavlović, Z. Cvetkovic","doi":"10.2298/saj1386065r","DOIUrl":"https://doi.org/10.2298/saj1386065r","url":null,"abstract":"We discuss the software developed for the purpose of determining the relative \u0000 coordinates (position angle θ and separation ρ) for visual double or \u0000 multiple stars. It is based on application of Fourier transforms in treating \u0000 CCD frames of these systems. The objective was to determine the relative \u0000 coordinates automatically to an extent as large as possible. In this way the \u0000 time needed for the reduction of many CCD frames becomes shorter. The \u0000 capabilities and limitations of the software are examined. Besides, the \u0000 possibility of improving is also considered. The software has been tested \u0000 and checked on a sample consisting of CCD frames of 165 double or multiple \u0000 stars obtained with the 2m telescope at NAO Rozhen in Bulgaria in October \u0000 2011. The results have been compared with the corresponding results obtained \u0000 by applying different software and the agreement is found to be very good.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/saj1386065r","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48246168","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}

{"title":"Deflection of light in equatorial plane due to Kerr-Taub-NUT body","authors":"S. Chakraborty, A. Sen","doi":"10.2298/SAJ1794023C","DOIUrl":"https://doi.org/10.2298/SAJ1794023C","url":null,"abstract":"According to General Relativity, there are factors like mass, rotation, charge and presence of Cosmological constant that can influence the path of light ray. Apart from these factors, many authors have also reported the influence of gravitomagnetism on the path of light ray. In this study we have discussed the effect of a rotating Kerr-Taub-NUT body where the strength of the gravitomagnetic monopole is represented by the NUT factor or magnetic mass. We use the null geodesic of photon method to obtain the deflection angle of light ray for a Kerr-Taub-NUT body in equatorial plane upto the fourth order term. Our study shows that the NUT factor has a noticeable effect on the path of the light ray. By considering the magnetism to be zero, the expression of bending angle gets reduced to the Kerr bending angle. However, we obtained a non-zero bending angle for a hypothetical massless, magnetic body.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673715","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}

{"title":"Solar Spectral Irradiance Variability of Some Chromospheric Emission Lines Through the Solar Activity Cycles 21-23","authors":"Ü. Göker, M. Sh. Gigolashvili, N. Kapanadze","doi":"10.2298/SAJ160126001G","DOIUrl":"https://doi.org/10.2298/SAJ160126001G","url":null,"abstract":"A study of variations of solar spectral irradiance (SSI) in the wavelength ranges 121.5 nm-300.5 nm for the period 1981-2009 is presented. We used various data for ultraviolet (UV) spectral lines and international sunspot number (ISSN) from interactive data centers such as SME (NSSDC), UARS (GDAAC), SORCE (LISIRD) and SIDC, respectively. We reduced these data by using the MATLAB software package. In this respect, we revealed negative correlations of intensities of UV (289.5 nm-300.5 nm) spectral lines originating in the solar chromosphere with the ISSN index during the unusually prolonged minimum between the solar activity cycles (SACs) 23 and 24. We also compared our results with the variations of solar activity indices obtained by the ground-based telescopes. Therefore, we found that plage regions decrease while facular areas are increasing in SAC 23. However, the decrease in plage regions is seen in small sunspot groups (SGs), contrary to this, these regions in large SGs are comparable to previous SACs or even larger as is also seen in facular areas. Nevertheless, negative correlations between ISSN and SSI data indicate that these variations are in close connection with the classes of sunspots/SGs, faculae and plage regions. Finally, we applied the time series analysis of spectral lines corresponding to the wavelengths 121.5 nm-300.5 nm and made comparisons with the ISSN data. We found an unexpected increase in the 298.5 nm line for the Fe II ion. The variability of Fe II ion 298.5 nm line is in close connection with the facular areas and plage regions, and the sizes of these solar surface indices play an important role for the SSI variability, as well. So, we compared the connection between the sizes of faculae and plage regions, sunspots/SGs, chemical elements and SSI variability. Our future work will be the theoretical study of this connection and developing of a corresponding model.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44166158","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}

{"title":"Long Photometric Cycles in Hot Algols","authors":"R. Mennickent","doi":"10.2298/SAJ1794001M","DOIUrl":"https://doi.org/10.2298/SAJ1794001M","url":null,"abstract":"We summarize the development of the field of Double Periodic Variables (DPVs, Mennickent et al. 2003) during the last fourteen years, placing these objects in the context of intermediate-mass close interacting binaries similar to β Persei (Algol) and β Lyrae (Sheliak) which are generally called Algols. DPVs show enigmatic long photometric cycles lasting on average about 33 times the orbital period, and have physical properties resembling, in some aspects, β Lyrae. About 200 of these objects have been found in the Galaxy and the Magellanic Clouds. Light curve models and orbitally resolved spectroscopy indicate that DPVs are semi-detached interacting binaries consisting of a near main-sequence B-type star accreting matter from a cooler giant and surrounded by an optically thick disc. This disc contributes a significant fraction of the system luminosity and its luminosity is larger than expected from the phenomenon of mass accretion alone. In some systems, an optically thin disc component is observed in well developed Balmer emission lines. The optically thick disc shows bright zones up to tens percent hotter than the disc, probably indicating shocks resulting from the gas and disc stream dynamics. We conjecture that a hotspot wind might be one of the channels for a mild systemic mass loss, since evidence for jets, winds or general mass loss has been found in β Lyrae, AUMon, HD170582, OGLE05155332-6925581 and V 393 Sco. Also, theoretical work by Van Rensbergen et al. (2008) and Deschamps et al. (2013) suggests that hotspot could drive mass loss from Algols. We give special consideration to the recently published hypothesis for the long-cycle, consisting of variable mass transfer driven by a magnetic dynamo (Schleicher and Mennickent 2017). The Applegate (1992) mechanism should modify cyclically the equatorial radius of the chromospherically active donor producing cycles of enhanced mass loss through the inner Lagrangian point. Chromospheric emission in V 393 Sco, an optically thicker hotspot in the high-state of HD170582 and evidence for magnetic fields in many Algols are observational facts supporting this picture. One of the open questions for this scenario is why, among the Algols showing evidence for magnetic fields, the DPV long-cycle is present only under some combinations of stellar parameters, particularly those including the B-type gainers. Other open questions are what are the descendants of these interesting binaries, how much mass contain the discs around the likely rapidly rotating gainers, and the role played by the outflows through the Lagrangian L2 and L3 points reported in a couple of systems.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48708198","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}

{"title":"Telescope pointing based on inertial measurement unit","authors":"D. Vujičić, R. Pavlović, Z. Cvetkovic, S. Randjić, D. Jagodić","doi":"10.2298/SAJ1794101V","DOIUrl":"https://doi.org/10.2298/SAJ1794101V","url":null,"abstract":"In this paper we study the problem of how to determine the coordinates of a \u0000 point a telescope is directed to on the basis of data obtained from a 9DOF \u0000 sensor board. On the 9DOF sensor board there are three sensors: the \u0000 gyroscope, accelerometer and magnetometer. By combining the data from all \u0000 the three sensors one obtains the Eulerian angles in the system tied to the \u0000 sensor board. The Eulerian angles are transformed into the horizontal and \u0000 equatorial coordinates in order to obtain the point the telescope is \u0000 directed to. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR32043 for the period 2011–2016, Grant no. 176011: Dynamics and kinematics of celestial bodies and systems]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47290106","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}

{"title":"Astrometric and Photometric Study of the Open Cluster NGC 2323","authors":"M. Y. Amin, W. Elsanhoury","doi":"10.2298/SAJ160802003A","DOIUrl":"https://doi.org/10.2298/SAJ160802003A","url":null,"abstract":"We present a study of the open cluster NGC 2323 using astrometric and photometric data. In our study we used two methods that are able to separate open cluster’s stars from those that belong to the stellar background. Our results of calculations by these two methods indicate that: 1) according to the membership probability, NGC 2323 should contain 497 stars, 2) the cluster center should be at 07 02 48 . 02 and -08◦ 20′ 17 . ′′74, 3) the limiting radius of NGC 2323 is 2.31 ± 0.04 pc, the surface number density at this radius is 98.16 stars pc−2, 4) the magnitude function has a maximum at about mv = 14 mag, 5) the total mass of NGC 2323 is estimated dynamically by using astrometric data to be 890 M , and statistically by using photometric data to be 900 M , and 6) the distance and age of the cluster are found to be equal to 900 ± 100 pc, and 140 ± 20 Myr, respectively. Finally the dynamical evolution parameter τ of the cluster is about 436.2.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43920391","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}

{"title":"Eccentricity samples: implications on the potential and the velocity distribution","authors":"R. Cubarsi, M. Stojanović, S. Ninkovič","doi":"10.2298/SAJ170221004C","DOIUrl":"https://doi.org/10.2298/SAJ170221004C","url":null,"abstract":"Planar and vertical epicycle frequencies and local angular velocity are related to the derivatives up to the second order of the local potential and can be used to test the shape of the potential from stellar disc samples. These samples show a more complex velocity distribution than halo stars and should provide a more realistic test. We assume an axisymmetric potential allowing a mixture of independent ellipsoidal velocity distributions, of separable or Staeckel form in cylindrical or spherical coordinates. We prove that values of local constants are not consistent with a potential separable in addition in cylindrical coordinates and with a spherically symmetric potential. The simplest potential that fits the local constants is used to show that the harmonical and non-harmonical terms of the potential are equally important. The same analysis is used to estimate the local constants. Two families of nested subsamples selected for decreasing planar and vertical eccentricities are used to borne out the relation between the mean squared planar and vertical eccentricities and the velocity dispersions of the subsamples. According to the first-order epicycle model, the radial and vertical velocity components provide accurate information on the planar and vertical epicycle frequencies. However, it is impossible to account for the asymmetric drift which introduces a systematic bias in estimation of the third constant. Under a more general model, when the asymmetric drift is taken into account, the rotation velocity dispersions together with their asymmetric drift provide the correct fit for the local angular velocity. The consistency of the results shows that this new method based on the distribution of eccentricities is worth using for kinematic stellar samples.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68673993","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}

{"title":"Dynamical models of two lenticular galaxies: NGC 1023 and NGC 4526","authors":"S. Samurović","doi":"10.2298/saj170330006s","DOIUrl":"https://doi.org/10.2298/saj170330006s","url":null,"abstract":"We study kinematics and dynamics of two lenticular galaxies that possess globular clusters (GCs) which extend beyond approximately seven effective radii. We analyze two nearby lenticular galaxies, NGC 1023 and NGC 4526, based on their GCs. We extract the kinematics of these galaxies and use it for dynamical modeling based on the Jeans equation. The Jeans equation was solved in both the Newtonian mass-follows-light approach assuming constant mass-to-light ratio and assuming a dark halo in the Navarro-Frenk-White form. We find that while the first galaxy, NGC 1023, does not need a significant amount of dark matter, in the other galaxy, NGC 4526, the dark component fully dominates stellar matter in the total dynamical mass. In this paper we also used three different MOND approaches and found that while for both galaxies MOND models can provide successful fits of the observed velocity dispersion, in the case of NGC 4526 we have a hint of an additional dark component even in the MOND framework.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68674086","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}