45 research outputs found
The Blue Stragglers of the Old Open Cluster NGC 188
The old (7 Gyr) open cluster NGC 188 has yielded a wealth of astrophysical
insight into its rich blue straggler population. Specifically, the NGC 188 blue
stragglers are characterized by: A binary frequency of 80% for orbital periods
less than days;Typical orbital periods around 1000 days;Typical
secondary star masses of 0.5 M; At least some white dwarf companion
stars; Modestly rapid rotation; A bimodal radial spatial distribution;
Dynamical masses greater than standard stellar evolution masses (based on
short-period binaries); Under-luminosity for dynamical masses (short-period
binaries). Extensive -body modeling of NGC 188 with empirical initial
conditions reproduces the properties of the cluster, and in particular the
main-sequence solar-type binary population. The current models also reproduce
well the binary orbital properties of the blue stragglers, but fall well short
of producing the observed number of blue stragglers. This deficit could be
resolved by reducing the frequency of common-envelope evolution during Roche
lobe overflow. Both the observations and the -body models strongly indicate
that the long-period blue-straggler binaries - which dominate the NGC 188 blue
straggler population - are formed by asymptotic-giant (primarily) and red-giant
mass transfer onto main sequence stars. The models suggest that the few
non-velocity-variable blue stragglers formed from mergers or collisions.
Several remarkable short-period double-lined binaries point to the importance
of subsequent dynamical exchange encounters, and provide at least one example
of a likely collisional origin for a blue straggler.Comment: Chapter 3, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Non-standard Hamiltonian effects on neutrino oscillations
We investigate non-standard Hamiltonian effects on neutrino oscillations,
which are effective additional contributions to the vacuum or matter
Hamiltonian. Since these effects can enter in either flavor or mass basis, we
develop an understanding of the difference between these bases representing the
underlying theoretical model. In particular, the simplest of these effects are
classified as ``pure'' flavor or mass effects, where the appearance of such a
``pure'' effect can be quite plausible as a leading non-standard contribution
from theoretical models. Compared to earlier studies investigating particular
effects, we aim for a top-down classification of a possible ``new physics''
signature at future long-baseline neutrino oscillation precision experiments.
We develop a general framework for such effects with two neutrino flavors and
discuss the extension to three neutrino flavors, as well as we demonstrate the
challenges for a neutrino factory to distinguish the theoretical origin of
these effects with a numerical example. We find how the precision measurement
of neutrino oscillation parameters can be altered by non-standard effects alone
(not including non-standard interactions in the creation and detection
processes) and that the non-standard effects on Hamiltonian level can be
distinguished from other non-standard effects (such as neutrino decoherence and
decay) if we consider specific imprint of the effects on the energy spectra of
several different oscillation channels at a neutrino factory.Comment: 30 pages, 6 figures, LaTeX, final version, published in Eur.Phys.J.
Body appreciation around the world: Measurement invariance of the Body Appreciation Scale-2 (BAS-2) across 65 nations, 40 languages, gender identities, and age.
The Body Appreciation Scale-2 (BAS-2) is a widely used measure of a core facet of the positive body image construct. However, extant research concerning measurement invariance of the BAS-2 across a large number of nations remains limited. Here, we utilised the Body Image in Nature (BINS) dataset - with data collected between 2020 and 2022 - to assess measurement invariance of the BAS-2 across 65 nations, 40 languages, gender identities, and age groups. Multi-group confirmatory factor analysis indicated that full scalar invariance was upheld across all nations, languages, gender identities, and age groups, suggesting that the unidimensional BAS-2 model has widespread applicability. There were large differences across nations and languages in latent body appreciation, while differences across gender identities and age groups were negligible-to-small. Additionally, greater body appreciation was significantly associated with higher life satisfaction, being single (versus being married or in a committed relationship), and greater rurality (versus urbanicity). Across a subset of nations where nation-level data were available, greater body appreciation was also significantly associated with greater cultural distance from the United States and greater relative income inequality. These findings suggest that the BAS-2 likely captures a near-universal conceptualisation of the body appreciation construct, which should facilitate further cross-cultural research. [Abstract copyright: Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.