Serbian Astronomical Journal最新文献

{"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":"1 1","pages":"75-84"},"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":"188 1","pages":"85-93"},"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":"188 1","pages":"45-54"},"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":"2014 1","pages":"37-44"},"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":"1 1","pages":"23-28"},"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":"1 1","pages":"99-101"},"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":"187 1","pages":"11-18"},"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":"187 1","pages":"1-10"},"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}

{"title":"Globular Cluster Star Classification: Application to M13","authors":"R. Caimmi","doi":"10.2298/SAJ1386025C","DOIUrl":"https://doi.org/10.2298/SAJ1386025C","url":null,"abstract":"Starting from recent determination of Fe, O, Na abundances on a restricted \u0000 sample (N = 67) of halo and thick disk stars, a natural and well motivated \u0000 selection criterion is defined for the classification globular cluster stars. \u0000 An application is performed to M13 using a sample (N = 113) for which Fe, O, \u0000 Na abundances have been recently inferred from observations. A comparison is \u0000 made between the current and earlier M13 star classifications. Both O and Na \u0000 empirical differential abundance distributions are determined for each class \u0000 and for the whole sample (with the addition of Fe in the last case) and \u0000 compared with their theoretical counterparts due to cosmic scatter obeying a \u0000 Gaussian distribution whose parameters are inferred from related subsamples. \u0000 The occurrence of an agreement between the empirical and theoretical \u0000 distributions is interpreted as absence of significant chemical evolution and \u0000 vice versa. The procedure is repeated with regard to four additional classes \u0000 depending on whether oxygen and sodium abundance is above (stage CE) or below \u0000 (stage AF) a selected threshold. Both O and Na empirical differential \u0000 abundance distributions, related to the whole sample, exhibit a linear fit \u0000 for the AF and CE stage. Within the errors, the oxygen slope for the CE stage \u0000 is equal and of opposite sign with respect to the sodium slope for AF stage, \u0000 while the contrary holds when dealing with the oxygen slope for the AF stage \u0000 with respect to the sodium slope for the CE stage. In the light of simple \u0000 models of chemical evolution applied to M13, oxygen depletion appears to be \u0000 mainly turned into sodium enrichment for [O/H]≥ -1.35 and [Na/H]≤ -1.45, \u0000 while one or more largely preferred channels occur for [O/H]< -1.35 and \u0000 [Na/H]> -1.45. In addition, the primordial to the current M13 mass ratio can \u0000 be inferred from the true sodium yield in units of the sodium solar \u0000 abundance. Though the above results are mainly qualitative due to large \u0000 (-+1.5 dex) uncertainties in abundance determination, still the exhibited \u0000 trend is expected to be real. The proposed classification of globular cluster \u0000 stars may be extended in a twofold manner, namely to: (i) elements other than \u0000 Na and Fe and (ii) globular clusters other than M13.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"2013 1","pages":"25-45"},"PeriodicalIF":0.5,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ1386025C","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68672031","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","authors":"R. Caimmi","doi":"10.2298/SAJ130924004C","DOIUrl":"https://doi.org/10.2298/SAJ130924004C","url":null,"abstract":"Linear [Q/H]-[O/H] relations, Q = Na, Mg, Si, Ca, Ti, Cr, Fe, Ni, are \u0000 inferred from a sample (N = 67) of recently studied FGK-type dwarf stars in \u0000 the solar neighbourhood including different populations (Nissen and Schuster \u0000 2010, Ramirez et al. 2012), namely LH (N = 24, low-α halo), HH (N = 25, \u0000 high-α halo), KD (N = 16, thick disk), and OL (N = 2, globular cluster \u0000 outliers). Regression line slope and intercept estimators and related \u0000 variance estimators are determined. With regard to the straight line, \u0000 [Q/H]=aQ[O/H]+bQ, sample stars are displayed along a \"main sequence\", [Q,O] \u0000 = [aQ, bQ, ΔbQ], leaving aside the two OL stars, which, in most cases (e.g. \u0000 Na), lie outside. The unit slope, aQ = 1, implies Q is a primary element \u0000 synthesised via SNII progenitors in the presence of a universal stellar \u0000 initial mass function (defined as simple primary element). In this respect, \u0000 Mg, Si, Ti, show âQ = 1 within -+2^σâQ; Cr, Fe, Ni, within -+3^σâQ; Na, Ca, \u0000 within -+r^σâQ, r > 3. The empirical, differential element abundance \u0000 distributions are inferred from LH, HH, KD, HA = HH + KD subsamples, where \u0000 related regression lines represent their theoretical counterparts within the \u0000 framework of simple MCBR (multistage closed box + reservoir) chemical \u0000 evolution models. Hence, the fractional yields, ^pQ/^pO, are determined and \u0000 (as an example) a comparison is shown with their theoretical counterparts \u0000 inferred from SNII progenitor nucleosynthesis under the assumption of a \u0000 power-law stellar initial mass function. The generalized fractional yields, \u0000 CQ=ZQ/ZaQ O, are determined regardless of the chemical evolution model. \u0000 The ratio of outflow to star formation rate is compared for different \u0000 populations in the framework of simple MCBR models. The opposite situation \u0000 of element abundance variation entirely due to cosmic scatter is also \u0000 considered under reasonable assumptions. The related differential element \u0000 abundance distribution fits to the data, as well as its counterpart inferred \u0000 in the opposite limit of instantaneous mixing in the presence of chemical \u0000 evolution, while the latter is preferred for HA subsample.","PeriodicalId":48878,"journal":{"name":"Serbian Astronomical Journal","volume":"187 1","pages":"19-41"},"PeriodicalIF":0.5,"publicationDate":"2013-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2298/SAJ130924004C","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68671849","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}