1,721,407 research outputs found
High velocity gas in S241 and IRAS 19529+2704
No full textWe have studied S241 and IRAS 19529 + 2704 by mapping the J = 1 - 0 transition of (CO)-C-12. High-velocity gas is found in both regions, and is identified as new outflows. The physical properties of the outflows such as size, mass and mechanical momentum are derived, and the characteristics of the driving source are analyzed. A large scale rotation with an angular velocity of omega similar to 0.48 x 10(-14)/s is measured in S241. The results suggest that they are active massive star-forming regions, and the massive young stellar objects are the driving source of the outflows.Astronomy & AstrophysicsSCI(E)3ARTICLE16-102
EC 19529–4430: SALT identifies the most carbon- and metal-poor extreme helium star
No full textEC 19529−4430 was identified as a helium-rich star in the Edinburgh-Cape Survey of faint-blue objects and subsequently resolved as a metal-poor extreme helium (EHe) star in the SALT survey of chemically-peculiar hot subdwarfs. This paper presents a fine analysis of the SALT high-resolution spectrum. EC 19529−4430 has Teff = 20 700 ± 250 K, log g/cm s−2 = 3.49 ± 0.03, and an overall metallicity some 1.3 dex below solar; surface hydrogen is by number. The surface CNO ratio 1:100:8 implies that the surface consists principally of CNO-processed helium and makes EC 19529−4430 the coolest known carbon-poor and nitrogen-rich EHe star. Metal-rich analogues include V652 Her and GALEX J184559.8−413827. Kinematically, its retrograde orbit indicates membership of the galactic halo. No pulsations were detected in TESS photometry and there is no evidence for a binary companion. EC 19529−4430 most likely formed from the merging of two helium white dwarfs, which themselves formed as a binary system some 11 Gyr ago
EC 19529-4430: SALT identifies the most carbon- and metal-poor extreme helium star
Get PDFEC 19529-4430 was identified as a helium-rich star in the Edinburgh-Cape
Survey of faint-blue objects and subsequently resolved as a metal-poor extreme
helium (EHe) star in the SALT survey of chemically-peculiar hot subdwarfs. This
paper presents a fine analysis of the SALT high-resolution spectrum. EC
19529-4430 has \,K, , and an overall metallicity some 1.3 dex below solar; surface
hydrogen is by number. The surface CNO ratio 1:100:8 implies
that the surface consists principally of CNO-processed helium and makes EC
19529-4430 the coolest known carbon-poor and nitrogen-rich EHe star. Metal-rich
analogues include V652 Her and GALEX J184559.8-413827. Kinematically, its
retrograde orbit indicates membership of the galactic halo. No pulsations were
detected in TESS photometry and there is no evidence for a binary companion. EC
19529-4430 most likely formed from the merging of two helium white dwarfs,
which themselves formed as a binary system some 11 Gyr ago.Comment: 13 pages, 11 figures. MNRAS in pres
High velocity gas in S241 and IRAS 19529+2704
No full textWe have studied S241 and IRAS 19529 + 2704 by mapping the J = 1 - 0 transition of (CO)-C-12. High-velocity gas is found in both regions, and is identified as new outflows. The physical properties of the outflows such as size, mass and mechanical momentum are derived, and the characteristics of the driving source are analyzed. A large scale rotation with an angular velocity of omega similar to 0.48 x 10(-14)/s is measured in S241. The results suggest that they are active massive star-forming regions, and the massive young stellar objects are the driving source of the outflows
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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