Serbian Astronomical Journal最新文献

{"title":"Relativistic Length Agony Continued","authors":"D. Redžić","doi":"10.2298/SAJ1488055R","DOIUrl":"https://doi.org/10.2298/SAJ1488055R","url":null,"abstract":"We made an attempt to remedy recent confusing treatments of some basic \u0000 relativistic concepts and results. Following the argument presented in an \u0000 earlier paper (Redžic 2008b), we discussed the misconceptions that are \u0000 recurrent points in the literature devoted to teaching relativity such as: \u0000 there is no change in the object in Special Relativity, illusory character of \u0000 relativistic length contraction, stresses and strains induced by Lorentz \u0000 contraction, and related issues. We gave several examples of the traps of \u0000 everyday language that lurk in Special Relativity. To remove a possible \u0000 conceptual and terminological muddle, we made a distinction between the \u0000 relativistic length reduction and relativistic FitzGerald-Lorentz \u0000 contraction, corresponding to a passive and an active aspect of length \u0000 contraction, respectively; we pointed out that both aspects have fundamental \u0000 dynamical contents. As an illustration of our considerations, we discussed \u0000 briefly the Dewan-Beran-Bell spaceship paradox and the ‘pole in a barn’ \u0000 paradox. [Projekat Ministarstva nauke Republike Srbije, br. 171028]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1488055R","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672353","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":"Binary star astrometry with milli and sub-milli arcsecond precision","authors":"S. Jankov, Z. Cvetkovic, R. Pavlović","doi":"10.2298/SAJ1488001J","DOIUrl":"https://doi.org/10.2298/SAJ1488001J","url":null,"abstract":"The past several decades have seen accelerating progress in improving binary \u0000 stars fundamental parameters determinations, as new observational techniques \u0000 have produced visual orbits of many spectroscopic binaries with a milli \u0000 arcsecond precision. Modern astrometry is rapidly approaching the goal of \u0000 sub-milli arcsecond precision, and although presently this precision has been \u0000 achieved only for a limited number of binary stars, in the near future this \u0000 will become a standard for very large number of objects. In this paper we \u0000 review the representative results of techniques which have already allowed \u0000 the sub-milli arcsecond precision like the optical long baseline \u0000 interferometry, as well as the precursor techniques such as speckle \u0000 interferometry, adaptive optics and aperture masking. These techniques \u0000 provide a step forward from milli to sub-milli arcsecond precision, allowing \u0000 even short period binaries to be resolved, and often resulting in orbits \u0000 allowing precisions in stellar dynamical masses better than 1%. We point out \u0000 that such unprecedented precisions should allow for a significant improvement \u0000 of our comprehension of stellar physics and other related astrophysical \u0000 topics.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1488001J","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672127","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":"A spectral atlas of λ Bootis stars","authors":"E. Paunzen, U. Heiter","doi":"10.2298/saj1488075p","DOIUrl":"https://doi.org/10.2298/saj1488075p","url":null,"abstract":"Since the discovery of λ Bootis stars, a permanent confusion about their \u0000 classification can be found in literature. This group of non-magnetic, \u0000 Population I, metal-poor A to F-type stars, has often been used as some sort \u0000 of trash can for \"exotic\" and spectroscopically dubious objects. Some \u0000 attempts have been made to establish a homogeneous group of stars which share \u0000 the same common properties. Unfortunately, the flood of \"new\" information \u0000 (e.g. UV and IR data) led again to a whole zoo of objects classified as λ \u0000 Bootis stars, which, however, are apparent non-members. To overcome this \u0000 unsatisfying situation, a spectral atlas of well established λ Bootis stars \u0000 for the classical optical domain was compiled. It includes intermediate \u0000 dispersion (40 and 120A mm-1) spectra of three λ Bootis, as well as \u0000 appropriate MK standard stars. Furthermore, \"suspicious\" objects, such as \u0000 shell and Field Horizontal Branch stars, have been considered in order to \u0000 provide to classifiers a homogeneous reference. As a further step, a high \u0000 resolution (8A mm-1) spectrum of one \"classical\" λ Bootis star in the same \u0000 wavelength region (3800-4600A) is presented. In total, 55 lines can be used \u0000 for this particular star to derive detailed abundances for nine heavy \u0000 elements (Mg, Ca, Sc, Ti, Cr, Mn, Fe, Sr and Ba).","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/saj1488075p","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672370","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":"Gaia science alerts and the observing facilities of the Serbian-Bulgarian mini-network telescopes","authors":"G. Damljanovic, O. Vince, S. Boeva","doi":"10.2298/SAJ1488085D","DOIUrl":"https://doi.org/10.2298/SAJ1488085D","url":null,"abstract":"The astrometric European Space Agency (ESA) Gaia mission was launched in \u0000 December 19, 2013. One of the tasks of the Gaia mission is production of an \u0000 astrometric catalog of over one billion stars and more than 500000 \u0000 extragalactic sources. The quasars (QSOs), as extragalactic sources and radio \u0000 emitters, are active galactic nuclei objects (AGNs) whose coordinates are \u0000 well determined via Very Long Baseline Interferometry (VLBI) technique and \u0000 may reach sub-milliarcsecond accuracy. The QSOs are the defining sources of \u0000 the quasi-inertial International Celestial Reference Frame (ICRF) because of \u0000 their core radio morphology, negligible proper motions (until \u0000 sub-milliarcsecond per year), and apparent point-like nature. Compact AGNs, \u0000 visible in optical domain, are useful for a direct link of the future Gaia \u0000 optical reference frame with the most accurate radio one. Apart from the \u0000 above mentioned activities, Gaia has other goals such as follow-up of \u0000 transient objects. One of the most important Gaia's requirements for \u0000 photometric alerts is a fast observation and reduction response, that is, \u0000 submition of observations within 24 hours. For this reason we have developed \u0000 a pipeline. In line with possibilities of our new telescope \u0000 (D(cm)/F(cm)=60/600) at the Astronomical Station Vidojevica (ASV, of the \u0000 Astronomical Observatory in Belgrade), we joined the Gaia-Follow-Up Network \u0000 for Transients Objects (Gaia-FUN-TO) for the photometric alerts. Moreover, in \u0000 view of the cooperation with Bulgarian colleagues (in the frst place, SV), \u0000 one of us (GD) initiated a local mini-network of Serbian { Bulgarian \u0000 telescopes useful for the Gaia-FUN-TO and other astronomical purposes. During \u0000 the next year we expect a new 1.4 m telescope at ASV site. The speed of data \u0000 processing (from observation to calibration server) could be one day. Here, \u0000 we present an overview of our activities in the Gaia-FUN-TO which includes \u0000 establishing Serbian { Bulgarian mini-network (of five telescopes at three \u0000 sites, ASV in Serbia, Belogradchik and Rozhen in Bulgaria), the Gaia-FUN-TO \u0000 test observations, and some results. [Projekat Ministarstva nauke Republike \u0000 Srbije, br. 176011: Dynamics and kinematics of celestial bodies and systems, \u0000 br. 176004: Stellar physics, i br. 176021: Visible and invisible matter in \u0000 nearby galaxies: theory and observations]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1488085D","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672381","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":"A comparative study of measured amplitude and phase perturbations of VLF and LF radio signals induced by solar flares","authors":"D. Šulić, V. Srećković","doi":"10.2298/SAJ1488045S","DOIUrl":"https://doi.org/10.2298/SAJ1488045S","url":null,"abstract":"Very Low Frequency (VLF) and Low Frequency (LF) signal perturbations were \u0000 examined to study ionospheric disturbances induced by solar X-ray flares in \u0000 order to understand processes involved in propagation of VLF/LF radio signals \u0000 over short paths and to estimate specific characteristics of each short path. \u0000 The receiver at the Belgrade station is constantly monitoring the amplitude \u0000 and phase of a coherent and subionospherically propagating LF signal operated \u0000 in Sicily NSC at 45.90 kHz, and a VLF signal operated in Isola di Tavolara \u0000 ICV at 20.27 kHz, with the great circle distances of 953 km and 976 km, \u0000 respectively. A significant number of similarities between these short paths \u0000 is a direct result of both transmitters and the receiver’s geographic \u0000 location. The main difference is in transmitter frequencies. From July 2008 \u0000 to February 2014 there were about 200 events that were chosen for further \u0000 examination. All selected examples showed that the amplitude and phase of VLF \u0000 and LF signals were perturbed by solar X-ray flares occurrence. This six-year \u0000 period covers both minimum and maximum of solar activity. Simultaneous \u0000 measurement of amplitude and phase of the VLF/LF signals during a solar flare \u0000 occurrence was applied to evaluate the electron density profile versus \u0000 altitude, to carry out the function of time over the middle Europe. [Projekat \u0000 Ministarstva nauke Republike Srbije, br. 176002 i br. III4402]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672306","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":"Radiative transfer in silylidene molecule","authors":"M. Sharma, M. Sharma, U. P. Verma, S. Chandra","doi":"10.2298/SAJ1488037S","DOIUrl":"https://doi.org/10.2298/SAJ1488037S","url":null,"abstract":"In order to search for silylidene (H2CSi) in the interstellar medium, Izuha et al. (1996) recorded microwave spectrum of H2CSi in laboratory and made an unsuccessful attempt of its identification in IRC +10216, Ori KL, Sgr B2, through its 717-616 transition at 222.055 GHz. For finding out if there are other transitions of H2CSi which may help in its identification in the interstellar medium, we have considered 25 rotational levels of ortho-H2CSi connected by collisional transitions and 35 radiative transitions, and solved radiative transfer problem using the LVG approximation. We have found that the brightness temperatures of 919-818, 918-817, 101,10-919, 1019-918, 111,11-101,10, 111,10-1019 and 121,12-111,11 transition are larger than that of 717-616 transition. Thus, these transitions may help in detection of H2CSi in the interstellar medium.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1488037S","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672299","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":"RECONSIDERATION OF MASS-DISTRIBUTION MODELS","authors":"S. Ninkovič","doi":"10.2298/SAJ1488023N","DOIUrl":"https://doi.org/10.2298/SAJ1488023N","url":null,"abstract":"The mass-distribution model proposed by Kuzmin and Veltmann (1973) is revisited. It is subdivided into two models which have a common case. Only one of them is subject of the present study. The study is focused on the relation between the density ratio (the central one to that corresponding to the core radius) and the total-mass fraction within the core radius. The latter one is an increasing function of the former one, but it cannot exceed one quarter, which takes place when the density ratio tends to infinity. Therefore, the model is extended by representing the density as a sum of two components. The extension results into possibility of having a correspondence between the infinite density ratio and 100% total-mass fraction. The number of parameters in the extended model exceeds that of the original model. Due to this, in the extended model, the correspondence between the density ratio and total-mass fraction is no longer one-to-one; several values of the total-mass fraction can correspond to the same value for the density ratio. In this way, the extended model could explain the contingency of having two, or more, groups of real stellar systems (subsystems) in the diagram total-mass fraction versus density ratio. [Projekat Ministarstva nauke Republike Srbije, br. 176011: Dynamics and Kinematics of Celestial Bodies and Systems]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1488023N","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672168","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":"Fractional yields inferred from halo and thick disk stars (Serb. Astron. J. - 187 (2013), 19)","authors":"R. Caimmi","doi":"10.2298/SAJ1488099E","DOIUrl":"https://doi.org/10.2298/SAJ1488099E","url":null,"abstract":"Due to a wrong sign in a computer code, theoretical yield ratios have been recalculated. Related changes affect only Figs. 12-13, where theoretical yield ratios are represented as vertical bands. The correct figures are provided and differences with respect to the earlier version are mentioned. Minor corrections are also shown.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1488099E","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672433","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":"Optical observations of the nearby galaxy IC342 with narrow band [SII] and Hα filters. I","authors":"M. M. Vučetić, B. Arbutina, D. Urošević, A. Dobardžić, M. Pavlović, T. Pannuti, N. Petrov","doi":"10.2298/SAJ150911002V","DOIUrl":"https://doi.org/10.2298/SAJ150911002V","url":null,"abstract":"We present observations of a portion of the nearby spiral galaxy IC342 using \u0000 narrow band [SII] and Hα filters. These observations were carried out in \u0000 November 2011 with the 2m RCC telescope at Rozhen National Astronomical \u0000 Observatory in Bulgaria. In this paper we report coordinates, diameters, Hα \u0000 and [SII] fluxes for 203 HII regions detected in two fields of view in IC342 \u0000 galaxy. The number of detected HII regions is 5 times higher than previously \u0000 known in these two parts of the galaxy. [Projekat Ministarstva nauke \u0000 Republike Srbije, br. 176005: Emission nebulae: structure and evolution]","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2013-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672484","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":"RADIO-CONTINUUM OBSERVATIONS OF A GIANT RADIO SOURCE QSO J0443.8-6141","authors":"M. Filipović, K. Čajko, J. Collier, N. Tothill","doi":"10.2298/SAJ1387001F","DOIUrl":"https://doi.org/10.2298/SAJ1387001F","url":null,"abstract":"We report the discovery of a giant double-lobed (lobe-core-lobe) \u0000 radio-continuum structure associated with QSO J0443.8-6141 at z=0.72. This \u0000 QSO was originally identified during the follow-up of a sample of ROSAT All \u0000 Sky Survey sources at radio and optical frequencies. With a linear size of \u0000 ~0.77 Mpc, QSO J0443.8-6141 is classified as a giant radio source (GRS); \u0000 based on its physical properties, we classify QSO J0443.8-6141 as a FR II \u0000 radio galaxy. High-resolution observations are required to reliably identify \u0000 GRSs; the next generation of southern sky radio and optical surveys will be \u0000 crucial to increasing our sample of these objects.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2013-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1387001F","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672115","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}