Since the discovery of λ Bootis stars, a permanent confusion about their classification can be found in literature. This group of non-magnetic, Population I, metal-poor A to F-type stars, has often been used as some sort of trash can for "exotic" and spectroscopically dubious objects. Some attempts have been made to establish a homogeneous group of stars which share the same common properties. Unfortunately, the flood of "new" information (e.g. UV and IR data) led again to a whole zoo of objects classified as λ Bootis stars, which, however, are apparent non-members. To overcome this unsatisfying situation, a spectral atlas of well established λ Bootis stars for the classical optical domain was compiled. It includes intermediate dispersion (40 and 120A mm-1) spectra of three λ Bootis, as well as appropriate MK standard stars. Furthermore, "suspicious" objects, such as shell and Field Horizontal Branch stars, have been considered in order to provide to classifiers a homogeneous reference. As a further step, a high resolution (8A mm-1) spectrum of one "classical" λ Bootis star in the same wavelength region (3800-4600A) is presented. In total, 55 lines can be used for this particular star to derive detailed abundances for nine heavy elements (Mg, Ca, Sc, Ti, Cr, Mn, Fe, Sr and Ba).
自从发现牧夫座λ星以来，关于它们的分类一直存在混淆。这组非磁性的，第I族，缺乏金属的A到f型恒星，经常被用作某种“外来”和光谱可疑物体的垃圾桶。有些人试图建立一个具有相同共同性质的同质恒星群。不幸的是，大量的“新”信息(例如紫外和红外数据)再次导致了一大批被归类为λ牧夫座恒星的天体，然而，它们显然不是成员。为了克服这种不满意的情况，编制了经典光学域λ牧夫座恒星的光谱图谱。它包括三个λ牧夫座的中间色散(40和120A mm-1)光谱，以及适当的MK标准恒星。此外，为了给分类器提供同质参考，还考虑了“可疑”天体，如壳星和场水平分支星。进一步，给出了一颗“经典”λ牧夫座恒星在相同波长区域(3800-4600A)的高分辨率(8A mm-1)光谱。总共有55条谱线可以用于这颗特殊的恒星，以获得9种重元素(Mg, Ca, Sc, Ti, Cr, Mn, Fe, Sr和Ba)的详细丰度。
{"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}
The astrometric European Space Agency (ESA) Gaia mission was launched in December 19, 2013. One of the tasks of the Gaia mission is production of an astrometric catalog of over one billion stars and more than 500000 extragalactic sources. The quasars (QSOs), as extragalactic sources and radio emitters, are active galactic nuclei objects (AGNs) whose coordinates are well determined via Very Long Baseline Interferometry (VLBI) technique and may reach sub-milliarcsecond accuracy. The QSOs are the defining sources of the quasi-inertial International Celestial Reference Frame (ICRF) because of their core radio morphology, negligible proper motions (until sub-milliarcsecond per year), and apparent point-like nature. Compact AGNs, visible in optical domain, are useful for a direct link of the future Gaia optical reference frame with the most accurate radio one. Apart from the above mentioned activities, Gaia has other goals such as follow-up of transient objects. One of the most important Gaia's requirements for photometric alerts is a fast observation and reduction response, that is, submition of observations within 24 hours. For this reason we have developed a pipeline. In line with possibilities of our new telescope (D(cm)/F(cm)=60/600) at the Astronomical Station Vidojevica (ASV, of the Astronomical Observatory in Belgrade), we joined the Gaia-Follow-Up Network for Transients Objects (Gaia-FUN-TO) for the photometric alerts. Moreover, in view of the cooperation with Bulgarian colleagues (in the frst place, SV), one of us (GD) initiated a local mini-network of Serbian { Bulgarian telescopes useful for the Gaia-FUN-TO and other astronomical purposes. During the next year we expect a new 1.4 m telescope at ASV site. The speed of data processing (from observation to calibration server) could be one day. Here, we present an overview of our activities in the Gaia-FUN-TO which includes establishing Serbian { Bulgarian mini-network (of five telescopes at three sites, ASV in Serbia, Belogradchik and Rozhen in Bulgaria), the Gaia-FUN-TO test observations, and some results. [Projekat Ministarstva nauke Republike Srbije, br. 176011: Dynamics and kinematics of celestial bodies and systems, br. 176004: Stellar physics, i br. 176021: Visible and invisible matter in nearby galaxies: theory and observations]
{"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}
Very Low Frequency (VLF) and Low Frequency (LF) signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares in order to understand processes involved in propagation of VLF/LF radio signals over short paths and to estimate specific characteristics of each short path. The receiver at the Belgrade station is constantly monitoring the amplitude and phase of a coherent and subionospherically propagating LF signal operated in Sicily NSC at 45.90 kHz, and a VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with the great circle distances of 953 km and 976 km, respectively. A significant number of similarities between these short paths is a direct result of both transmitters and the receiver’s geographic location. The main difference is in transmitter frequencies. From July 2008 to February 2014 there were about 200 events that were chosen for further examination. All selected examples showed that the amplitude and phase of VLF and LF signals were perturbed by solar X-ray flares occurrence. This six-year period covers both minimum and maximum of solar activity. Simultaneous measurement of amplitude and phase of the VLF/LF signals during a solar flare occurrence was applied to evaluate the electron density profile versus altitude, to carry out the function of time over the middle Europe. [Projekat Ministarstva nauke Republike Srbije, br. 176002 i br. III4402]
为了了解甚低频(VLF) /低频(LF)无线电信号在短路径上传播的过程，并估计每个短路径的具体特征，研究了太阳x射线耀斑引起的电离层扰动。贝尔格莱德站的接收机持续监测西西里岛NSC运行频率为45.90 kHz的相干和亚层传播低频信号和Isola di Tavolara ICV运行频率为20.27 kHz的低频信号的振幅和相位，大圆距离分别为953 km和976 km。这些短路径之间的大量相似之处是发射器和接收器地理位置的直接结果。主要区别在于发射频率。从2008年7月到2014年2月，大约有200个项目被选中进行进一步的检查。所选的例子表明，太阳x射线耀斑的发生对低频和低频信号的幅值和相位产生了扰动。这6年期间包括太阳活动的最小值和最大值。在太阳耀斑发生期间，同时测量VLF/LF信号的振幅和相位，以评估电子密度分布与高度的关系，从而在中欧地区进行时间函数。[南斯拉夫]塞族共和国部长项目;[176002 .]III4402]
{"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}
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.
为了寻找星际介质中的硅烷(H2CSi)， Izuha et al.(1996)在实验室中记录了H2CSi的微波光谱，并通过其在222.055 GHz的717-616跃迁在IRC +10216, Ori KL, Sgr B2中进行了不成功的鉴定。为了找出H2CSi在星际介质中是否存在其他有助于识别的跃迁，我们考虑了25个由碰撞跃迁连接的邻H2CSi旋转能级和35个辐射跃迁，并利用LVG近似求解了辐射传递问题。我们发现919-818、918-817、101、10-919、1019-918、111、11-101、10、111、10-1019和121、12-111、11转捩的亮温大于717-616转捩的亮温。因此，这些跃迁可能有助于探测星际介质中的H2CSi。
{"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}
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]
{"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}
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.
{"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}
M. M. Vučetić, B. Arbutina, D. Urošević, A. Dobardžić, M. Pavlović, T. Pannuti, N. Petrov
We present observations of a portion of the nearby spiral galaxy IC342 using narrow band [SII] and Hα filters. These observations were carried out in November 2011 with the 2m RCC telescope at Rozhen National Astronomical Observatory in Bulgaria. In this paper we report coordinates, diameters, Hα and [SII] fluxes for 203 HII regions detected in two fields of view in IC342 galaxy. The number of detected HII regions is 5 times higher than previously known in these two parts of the galaxy. [Projekat Ministarstva nauke Republike Srbije, br. 176005: Emission nebulae: structure and evolution]
{"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}
We report the discovery of a giant double-lobed (lobe-core-lobe) radio-continuum structure associated with QSO J0443.8-6141 at z=0.72. This QSO was originally identified during the follow-up of a sample of ROSAT All Sky Survey sources at radio and optical frequencies. With a linear size of ~0.77 Mpc, QSO J0443.8-6141 is classified as a giant radio source (GRS); based on its physical properties, we classify QSO J0443.8-6141 as a FR II radio galaxy. High-resolution observations are required to reliably identify GRSs; the next generation of southern sky radio and optical surveys will be crucial to increasing our sample of these objects.
{"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}
Starting from recent determination of Fe, O, Na abundances on a restricted sample (N = 67) of halo and thick disk stars, a natural and well motivated selection criterion is defined for the classification globular cluster stars. An application is performed to M13 using a sample (N = 113) for which Fe, O, Na abundances have been recently inferred from observations. A comparison is made between the current and earlier M13 star classifications. Both O and Na empirical differential abundance distributions are determined for each class and for the whole sample (with the addition of Fe in the last case) and compared with their theoretical counterparts due to cosmic scatter obeying a Gaussian distribution whose parameters are inferred from related subsamples. The occurrence of an agreement between the empirical and theoretical distributions is interpreted as absence of significant chemical evolution and vice versa. The procedure is repeated with regard to four additional classes depending on whether oxygen and sodium abundance is above (stage CE) or below (stage AF) a selected threshold. Both O and Na empirical differential abundance distributions, related to the whole sample, exhibit a linear fit for the AF and CE stage. Within the errors, the oxygen slope for the CE stage is equal and of opposite sign with respect to the sodium slope for AF stage, while the contrary holds when dealing with the oxygen slope for the AF stage with respect to the sodium slope for the CE stage. In the light of simple models of chemical evolution applied to M13, oxygen depletion appears to be mainly turned into sodium enrichment for [O/H]≥ -1.35 and [Na/H]≤ -1.45, while one or more largely preferred channels occur for [O/H]< -1.35 and [Na/H]> -1.45. In addition, the primordial to the current M13 mass ratio can be inferred from the true sodium yield in units of the sodium solar abundance. Though the above results are mainly qualitative due to large (-+1.5 dex) uncertainties in abundance determination, still the exhibited trend is expected to be real. The proposed classification of globular cluster stars may be extended in a twofold manner, namely to: (i) elements other than Na and Fe and (ii) globular clusters other than M13.
本文从最近对冕星和厚盘星有限样本(N = 67) Fe、O、Na丰度的测定出发，定义了一个自然的、动机良好的球状星团恒星分类选择标准。应用M13使用样品(N = 113)，其中Fe, O, Na丰度最近已从观测推断。比较了当前和早期M13恒星的分类。对于每一类和整个样本(最后一种情况下添加了铁)，确定了O和Na的经验差异丰度分布，并将其与理论对应物进行比较，因为宇宙散射服从高斯分布，其参数是从相关子样本推断出来的。经验分布和理论分布之间的一致被解释为没有重要的化学演化，反之亦然。根据氧和钠的丰度是否高于(CE阶段)或低于(AF阶段)选定的阈值，对另外四个类别重复此过程。与整个样品相关的O和Na的经验差异丰度分布与AF和CE阶段呈线性拟合。在误差范围内，CE阶段的氧斜率与AF阶段的钠斜率相等且符号相反，而AF阶段的氧斜率与CE阶段的钠斜率相反。根据应用于M13的简单化学演化模型，当[O/H]≥-1.35和[Na/H]≤-1.45时，氧耗尽似乎主要转化为钠富集，而当[O/H]< -1.35和[Na/H]> -1.45时，则出现一个或多个主要优先通道。此外，原始和当前M13的质量比可以从以钠太阳丰度为单位的真实钠产量推断出来。虽然上述结果主要是定性的，因为丰度测定的不确定性较大(-+1.5指数)，但预计所展示的趋势是真实的。提出的球状星团恒星的分类可以以两种方式扩展，即:(i)除Na和Fe以外的元素和(ii)除M13以外的球状星团。
{"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}
Linear [Q/H]-[O/H] relations, Q = Na, Mg, Si, Ca, Ti, Cr, Fe, Ni, are inferred from a sample (N = 67) of recently studied FGK-type dwarf stars in the solar neighbourhood including different populations (Nissen and Schuster 2010, Ramirez et al. 2012), namely LH (N = 24, low-α halo), HH (N = 25, high-α halo), KD (N = 16, thick disk), and OL (N = 2, globular cluster outliers). Regression line slope and intercept estimators and related variance estimators are determined. With regard to the straight line, [Q/H]=aQ[O/H]+bQ, sample stars are displayed along a "main sequence", [Q,O] = [aQ, bQ, ΔbQ], leaving aside the two OL stars, which, in most cases (e.g. Na), lie outside. The unit slope, aQ = 1, implies Q is a primary element synthesised via SNII progenitors in the presence of a universal stellar initial mass function (defined as simple primary element). In this respect, Mg, Si, Ti, show âQ = 1 within -+2^σâQ; Cr, Fe, Ni, within -+3^σâQ; Na, Ca, within -+r^σâQ, r > 3. The empirical, differential element abundance distributions are inferred from LH, HH, KD, HA = HH + KD subsamples, where related regression lines represent their theoretical counterparts within the framework of simple MCBR (multistage closed box + reservoir) chemical evolution models. Hence, the fractional yields, ^pQ/^pO, are determined and (as an example) a comparison is shown with their theoretical counterparts inferred from SNII progenitor nucleosynthesis under the assumption of a power-law stellar initial mass function. The generalized fractional yields, CQ=ZQ/ZaQ O, are determined regardless of the chemical evolution model. The ratio of outflow to star formation rate is compared for different populations in the framework of simple MCBR models. The opposite situation of element abundance variation entirely due to cosmic scatter is also considered under reasonable assumptions. The related differential element abundance distribution fits to the data, as well as its counterpart inferred in the opposite limit of instantaneous mixing in the presence of chemical evolution, while the latter is preferred for HA subsample.
线性[Q/H]-[O/H]关系，Q = Na, Mg, Si, Ca, Ti, Cr, Fe, Ni，是从最近研究的太阳附近的fgk型矮星样本(N = 67)中推断出来的，包括不同的种群(Nissen and Schuster 2010, Ramirez et al. 2012)，即LH (N = 24，低α晕)，HH (N = 25，高α晕)，KD (N = 16，厚盘)和OL (N = 2，球状星团异常值)。确定了回归线斜率和截距估计量以及相关方差估计量。对于直线[Q/H]=aQ[O/H]+bQ，样本恒星沿着“主序”[Q,O] = [aQ, bQ， ΔbQ]显示，除了两颗OL星，它们在大多数情况下(例如Na)位于外面。单位斜率aQ = 1，意味着Q是在普遍恒星初始质量函数(定义为简单主元素)存在的情况下，通过SNII祖细胞合成的主元素。在这方面，Mg, Si, Ti在-+2^σ q范围内表现为 q = 1;Cr, Fe, Ni，在-+3^σ q内;Na, Ca，在-+r^σ q, r > 3。从LH, HH, KD, HA = HH + KD亚样本中推断出经验的、差异的元素丰度分布，其中相关的回归线代表了简单MCBR(多级封闭箱+储层)化学演化模型框架内的理论对应。因此，确定了分数产率^pQ/^pO，并(作为一个例子)与在幂律恒星初始质量函数假设下由SNII祖核合成推断出的理论产率进行了比较。广义分数产率CQ=ZQ/ZaQ O，与化学演化模型无关。在简单MCBR模型的框架下，比较了不同种群的流出率与恒星形成率的比值。在合理的假设下，也考虑了元素丰度变化完全由宇宙散射引起的相反情况。相关的差异元素丰度分布与数据吻合，以及在化学演化存在的瞬时混合的相反限制下推断的对应，而后者更适合HA子样品。
{"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}
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