1,721,122 research outputs found
An Eccentric Planet Orbiting the Polar V808 Aurigae
No full textAbstract We analyze 15 yr of eclipse timings of the polar V808 Aur. The rapid ingress/egress of the white dwarf and bright accretion region provide timings as precise as a few tenths of a second for rapid cadence photometric data. We find that between 2015 and 2018, the eclipse timings deviated from a linear ephemeris by more than 30 s. The rapid timing change is consistent with the periastron passage of a planet in an eccentric orbit about the polar. The best-fit orbital period is 11 ± 1 yr and we estimate a projected mass of M sin ( i ) = 6.8 ± 0.7 Jupiter masses. We also show that the eclipse timings are correlated with the brightness of the polar with a slope of 1.1 s mag −1 . This is likely due to the change in the geometry of the accretion curtains as a function of the mass transfer rate in the polar. While an eccentric planet offers an excellent explanation to the available eclipse data for V808 Aur, proposed planetary systems in other eclipsing polars have often struggled to accurately predict future eclipse timings
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
Physics in the extreme: X-ray and optical studies of magnetic white dwarfs and related objects
No full textIn this thesis, we present results from optical and X-ray studies of compact binary systems. These observations are used to constrain orbital parameters - mainly periods and inclinations for several cataclysmic variables - and examine the accretion structures within the systems. In Chapters 3 and 4, optical and X-ray studies of two interesting cataclysmic variables systems, Lanning 386 and MASTER OTJ192328.22+612413.5, are presented. The X-ray and optical data of these objects suggest that both systems have a high inclination and harbour weakly magnetic white dwarfs with spin periods 17-22 min. There is also a strong focus on studying the long term behaviour in intermediate polars in this thesis. Chapter 5 presents results from Kepler observations of FO Aquarii taken over 69 consecutive days. The shape of the light curve is consistent with the outer edge of the accretion disc being eclipsed and the detected period is longer than the last reported period of 1254.284(16) s, suggesting that FO Aqr was now spinning down, and had a positive P˙ at the time of the observations. Chapter 6 continues the work on FO Aquarii, and presents X-ray data taken during a low accretion state. The X-ray spectrum shows an increase in the ratio of the soft X-ray flux to the hard X-ray flux due to a change in the partial covering fraction of the white dwarf and a change in the hydrogen column density within the disc. XMM-Newton observations of FO Aqr during the subsequent recovery suggest that the system had not yet returned to its typical high state by November 2016. The spin period of the white dwarf in 2014 and 2015 is refined to 1254.3342(8) s. Chapter 7 focuses on CSS120422:J111127+571239, an “evolved main-sequence” channel cataclysmic variable. We present spectroscopy of CSS120422:J111127+571239 using the COS FUV instrument on the Hubble Space Telescope and using the MODS spectrograph on the Large Binocular Telescope. The UV spectrum shows Si IV, N V and He II, but no detectable C IV. The anomalous nitrogen/carbon ratio is seen in a small number of other CVs and confirms a unique binary evolution. We also present and compare the optical spectrum of V418 Ser and advocate that it is also an evolved main-sequence system. Finally, Chapter 8 presents results on UW Coronae Borealis, a low mass X-ray x Abstract binary that shows both Type 1 X-ray and optical bursts. The orbital period is refined to 110.97680(1) min. 17 optical bursts are presented, with 10 of these bursts being resolved temporally. The average e-folding time of 19 ± 3s for the bursts is consistent with the previously found value. Optical bursts are observed during a previously identified gap in orbital phase centred on φ = 0.967, meaning the reprocessing site is not eclipsed as previously thought. Finally, the apparent P-Cygni profiles present in some of the atomic lines in the optical spectra are due to transient absorption, which suggests the origin of the absorption is not a wind from the primary
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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