1,721,151 research outputs found
A Galaxy of Binaries: The impact of binary interactions on gravitational-wave sources, asteroseismic pulsations and stellar kinematics
Full text linkThesis (Ph.D.)--University of Washington, 2025Massive stars are extremely impactful across a range of astrophysics, providing essential feedback for galaxy evolution and producing transients such as supernovae and gravitational-wave mergers. The vast majority of these stars are formed in binaries and higher-order multiple systems, a large fraction of which will interact during their lifetimes and significantly alter their subsequent evolution. Despite the importance of massive stars, and the prevalence of massive binary stars, many aspects of binary stellar evolution remain uncertain across several orders of In this dissertation I describe my work in exploring the impact of binary interactions on a variety of massive stellar populations, both through rapid population synthesis and detailed 1D stellar evolution models. In particular, I consider the sensitivity of these results to major uncertainties in binary physics, with a view towards placing constraints on binary physics parameters. The culmination of this work is not only a series of scientific results and predictions, but also two new open-source codes (LEGWORK and cogsworth) that enable future community-driven investigations into these matters. In Chapter 1, I introduce the importance of massive binary stars, and outline the major uncertainties that remain, as well as some methodologies for addressing these uncertainties. After this introduction, I consider the population of gravitational-wave sources that will be detectable by the future spaced-based detector LISA (Chapters 2 & 3). Our new open-source code, LEGWORK, provides the community with a reliable resource for calculating the detectability of LISA sources and computing their evolution due to gravitational-wave emission. We use LEGWORK to explore how the rates and demographics of the galactic population of black hole and neutron star binaries are sensitive to different aspects of binary From here, I move from gravitational-waves to gravity-mode pulsations and the asteroseismology of massive stars that have accreted material from a companion (Chapter 4). With our proof-of-principle analysis, we established for the first time that mass transfer can leave a significant imprint on the asteroseismic signals of accretor stars. We showed that the rejuvenation of the convective core as a result of mass transfer leaves an imprint on the chemical composition gradient in the star. This change in gradient influences all pulsations that are sensitive to that region of the star, shifting their pulsation periods. We showed that typical asteroseismic methods for estimating the mass and age of the star (which assume single star evolution) can be significantly erroneous for accretor stars.
In the subsequent chapters, I focus on the new techniques I developed for predicting the extrinsic positions and kinematics of massive binaries, in addition to their intrinsic properties such as rates, masses and orbital periods. I present a new open-source code, cogsworth, which can be used to perform self-consistent population synthesis and galactic dynamics simulation (Chapter 5). We used cogsworth to demonstrate how the positions of massive stellar populations can inform our understanding of binary interactions. From here, I examine how ejection velocities of stars are relatively insensitive to the strength of supernova natal kicks and compare the prescriptions for these ejections across three different population synthesis codes (Chapter 6).
In Chapter 7, I use cogsworth to explore how binary interactions impact the timing and location of core-collapse supernovae. Current models for supernova feedback in hydrodynamical simulations assume that all massive stars are formed as single stars. We show that binary interactions result in both late-time and spatially-displaced supernovae. We find that more than a quarter of supernovae occur after the time of the final single star supernova, while 13% explode more than 100pc from their parent star cluster. We assessed the robustness of these predictions to a plethora of variations in binary physics, initial conditions and galaxy parameters and found these results are surprisingly insensitive to uncertainties in the parameters we considered. Given that these supernovae could have a significantly different impact on galactic feedback, we developed a new analytic model for core-collapse supernova feedback. This model includes physically-motivated metallicity-dependent transitions and reproduces the timing and velocity distributions of supernovae to within 1% and 4% respectively. Our model can be used in future hydrodynamical simulations to better account for binary evolution. This may be particularly relevant for high redshift galaxies in which the spatial extent of the galaxy is reduced, while the low-metallicity environment produces even later and more distributed supernovae. Finally in Chapter 8, I discuss the future directions of this research and consider the potential avenues for constraining binary evolution that this thesis has enabled. In Chapter 9, I summarise this thesis, concluding with the hope that the findings I presented, as well as the new open-source codes that we released, will drive forward the field of massive binary evolution
Optimizing serendipitous detections of kilonovae: cadence and filter selection
No full textThe rise of multimessenger astronomy has brought with it the need to exploit all available data streams and learn more about the astrophysical objects that fall within its breadth. One possible avenue is the search for serendipitous optical/near-infrared counterparts of gamma-ray bursts (GRBs) and gravitational-wave (GW) signals, known as kilonovae. With surveys such as the Zwicky Transient Facility (ZTF), which observes the sky with a cadence of ∼3 d, the existing counterpart locations are likely to be observed; however, due to the significant amount of sky to explore, it is difficult to search for these fast-evolving candidates. Thus, it is beneficial to optimize the survey cadence for realtime kilonova identification and enable further photometric and spectroscopic observations. We explore how the cadence of wide field-of-view surveys like ZTF can be improved to facilitate such identifications. We show that with improved observational choices, e.g. the adoption of three epochs per night on a ∼nightly basis, and the prioritization of redder photometric bands, detection efficiencies improve by about a factor of two relative to the nominal cadence. We also provide realistic hypothetical constraints on the kilonova rate as a form of comparison between strategies, assuming that no kilonovae are detected throughout the long-term execution of the respective observing plan. These results demonstrate how an optimal use of ZTF increases the likelihood of kilonova discovery independent of GWs or GRBs, thereby allowing for a sensitive search with less interruption of its nominal cadence through Target of Opportunity programs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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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