Impact of pions on binary neutron star mergers

We study the impact of pions in simulations of neutron star mergers and explore the impact on gravitational-wave observables. We model charged and neutral pions as a non-interacting Boson gas with a chosen, constant effective mass. We add the contributions of pions, which can occur as a condensate or as a thermal population, to existing temperature and composition dependent equations of state. Compared to the models without pions, the presence of a pion condensate decreases the characteristic properties of cold, non-rotating neutron stars such as the maximum mass, the radius and the tidal deformability. We conduct relativistic hydrodynamical simulations of neutron star mergers for these modified equations of state models and compare to the original models, which ignore pions. Generally, the inclusion of pions leads to a softening of the equation of state, which is more pronounced for smaller effective pion masses. We find a shift of the dominant postmerger gravitational-wave frequency by up to 150~Hz to higher frequencies and a reduction of the threshold binary mass for prompt black-hole formation by up to 0.07~$M_\odot$. We evaluate empirical relations between the threshold mass or the dominant postmerger gravitational-wave frequency and stellar parameters of nonrotating neutron stars. These relations are constructed to extract these stellar properties from merger observations and are built based on large sets of equation of state models which do not include pions. Comparing to our calculations with pions, we find that these empirical relations remain valid to good accuracy, which justifies their use although they neglect a possible impact of pions. We also address the mass ejection by neutron star mergers and observe a moderate enhancement of the ejecta mass by a few ten per cent. (abridged)Comment: 27 pages, 24 figures, accepted for publication in Phys. Rev.

Halal or not? Exploring Muslim perceptions of cultured meat in Singapore

Singapore was the first country to approve cultured meat for public consumption. However, it remains unclear whether Muslims, who adhere to religious dietary restrictions and constitute a significant proportion of Singapore's population, are willing to consume cultured meat. Informed by the cognitive miser model, this study explores how Muslims make sense of cultured meat through their religious beliefs, trust in different stakeholders, as well as their risk or benefit perceptions of cultured meat. The findings from online focus group discussions showed that Muslim participants would only consider consuming cultured meat if it is certified halal (i.e., compliant with Islamic laws) and they also voiced religious concerns about cultured meat. Muslims have strong trust in food regulatory authorities in providing information about the safety and halal status of cultured meat. In addition to religious concerns, Muslims had similar risk and benefit perceptions of cultured meat compared to those of the non-Muslims. Theoretical and practical implications were discussed

End-to-end kilonova models of neutron-star mergers with delayed black-hole formation

We investigate the nucleosynthesis and kilonova properties of binary neutron-star (NS) merger models which lead to intermediate remnant lifetimes of ~0.1-1seconds until black-hole (BH) formation and describe all components of material ejected during the dynamical merger phase, NS-remnant evolution, and final viscous disintegration of the BH torus after gravitational collapse. To this end we employ a combination of hydrodynamics, nucleosynthesis, and radiative-transfer tools to achieve a consistent end-to-end modeling of the system and its observables. We adopt a novel version of the Shakura-Sunyaev scheme allowing to vary the approximate turbulent viscosity inside the NS remnant independently of the surrounding disk. We find that asymmetric progenitors lead to shorter remnant lifetimes and enhanced ejecta masses, although the viscosity affects the absolute values of these characteristics. The integrated production of lanthanides and heavier elements in such binary systems is sub-solar, suggesting that the considered scenarios contribute in a sub-dominant fashion to r-process enrichment. One reason is that BH-tori formed after delayed collapse exhibit less neutron-rich conditions than typically found, and often assumed in previous BH-torus models, for early BH formation. The outflows in our models feature strong anisotropy as a result of the lanthanide-poor polar neutrino-driven wind pushing aside lanthanide-rich dynamical ejecta. Considering the complexity of the models, the estimated kilonova light curves show promising agreement with AT2017gfo after times of several days, while the remaining inconsistencies at early times could possibly be overcome in binary configurations with a more dominant neutrino-driven wind relative to the dynamical ejecta.Comment: 16 pages, 9 figures, 1 table, accepted to ApJ

Self-consistent 3D radiative transfer for kilonovae: directional spectra from merger simulations

We present three-dimensional radiative transfer calculations for the ejecta from a neutron star merger that include line-by-line opacities for tens of millions of bound-bound transitions, composition from an r-process nuclear network, and time-dependent thermalization of decay products from individual $\alpha$ and $\beta^-$ decay reactions. In contrast to expansion opacities and other wavelength-binned treatments, a line-by-line treatment enables us include fluorescence effects and associate spectral features with the emitting and absorbing lines of individual elements. We find variations in the synthetic observables with both the polar and azimuthal viewing angles. The spectra exhibit blended features with strong interactions by Ce III, Sr II, Y II, and Zr II that vary with time and viewing direction. We demonstrate the importance of wavelength-calibration of atomic data using a model with calibrated Sr, Y, and Zr data, and find major differences in the resulting spectra, including a better agreement with AT2017gfo. The synthetic spectra for near-polar inclination show a feature at around 8000 A, similar to AT2017gfo. However, they evolve on a more rapid timescale, likely due to the low ejecta mass (0.005 M$_\odot$) as we take into account only the early ejecta. The comparatively featureless spectra for equatorial observers gives a tentative prediction that future observations of edge-on kilonovae will appear substantially different from AT2017gfo. We also show that 1D models obtained by spherically averaging the 3D ejecta lead to dramatically different direction-integrated luminosities and spectra compared to full 3D calculations.Comment: 12 pages, 5 figures. Accepted by ApJ

Towards inferring the geometry of kilonovae

Recent analysis of the kilonova, AT2017gfo, has indicated that this event was highly spherical. This may challenge hydrodynamics simulations of binary neutron star mergers, which usually predict a range of asymmetries, and radiative transfer simulations show a strong direction dependence. Here we investigate whether the synthetic spectra from a 3D kilonova simulation of asymmetric ejecta from a hydrodynamical merger simulation can be compatible with the observational constraints suggesting a high degree of sphericity in AT2017gfo. Specifically, we determine whether fitting a simple P-Cygni line profile model leads to a value for the photospheric velocity that is consistent with the value obtained from the expanding photosphere method. We would infer that our kilonova simulation is highly spherical at early times, when the spectra resemble a blackbody distribution. The two independently inferred photospheric velocities can be very similar, implying a high degree of sphericity, which can be as spherical as inferred for AT2017gfo, demonstrating that the photosphere can appear spherical even for asymmetrical ejecta. The last-interaction velocities of radiation escaping the simulation show a high degree of sphericity, supporting the inferred symmetry of the photosphere. We find that when the synthetic spectra resemble a blackbody the expanding photosphere method can be used to obtain an accurate luminosity distance (within 4-7 per cent).Comment: 11 pages, submitted to MNRA

CONCEPTUALISING PLANT-HUMAN RELATIONS AMONG GARDENERS IN SINGAPORE

Bachelor'sBachelor of Social Sciences (Honours

Profiling of proteins secreted in the bovine oviduct reveals diverse functions of this luminal microenvironment

The oviductal microenvironment is a site for key events that involve gamete maturation, fertilization and early embryo development. Secretions into the oviductal lumen by either the lining epithelium or by transudation of plasma constituents are known to contain elements conducive for reproductive success. Although previous studies have identified some of these factors involved in reproduction, knowledge of secreted proteins in the oviductal fluid remains rudimentary with limited definition of function even in extensively studied species like cattle. In this study, we used a shotgun proteomics approach followed by bioinformatics sequence prediction to identify secreted proteins present in the bovine oviductal fluid (ex vivo) and secretions from the bovine oviductal epithelial cells (in vitro). From a total of 2087 proteins identified, 266 proteins could be classified as secreted, 109 (41%) of which were common for both in vivo and in vitro conditions. Pathway analysis indicated different classes of proteins that included growth factors, metabolic regulators, immune modulators, enzymes, and extracellular matrix components. Functional analysis revealed mechanisms in the oviductal lumen linked to immune homeostasis, gamete maturation, fertilization and early embryo development. These results point to several novel components that work together with known elements mediating functional homeostasis, and highlight the diversity of machinery associated with oviductal physiology and early events in cattle fertility

Systematics of prompt black-hole formation in neutron star mergers

This study addresses the collapse behavior of neutron star (NS) mergers expressed through the binary threshold mass M_thr for prompt black hole (BH) formation, which we determine by relativistic hydrodynamical simulations for 40 equation of state (EoS) models. M_thr can be well described by various fit formulae involving stellar parameters of nonrotating NSs. Using these relations we compute which constraints on NS radii and the tidal deformability are set by current and future merger detections revealing information about the merger product. We systematically investigate the impact of the binary mass ratio q=M_1/M_2 and assemble different fits, which make different assumptions about a-priori knowlegde. We find fit formulae for M_thr including an explicit q dependence, which are valid in a broad range of 0.7<=q<=1 and which are nearly as tight as relations for fixed mass ratios. For most EoS models except extreme cases M_thr of asymmetric mergers is equal or smaller than the one of equal-mass binaries. The impact of the binary mass asymmetry on M_thr becomes stronger with more extreme mass ratios, while M_thr is approximately constant for small deviations from q=1. We describe that a phase transition to deconfined quark matter can leave a characteristic imprint on the collapse behavior. The presence of quark matter can reduce the stability of the remnant and thus M_thr relative to a purely hadronic reference model. Comparing the threshold mass and the tidal deformability Lambda_thr of a system with M_thr can yield peculiar combinations of those two quantities, where M_thr is particularly small in relation to Lambda_thr. Hence, a combined measurement of both quantities can indicate the onset of quark deconfinement. We point out new univariate relations between M_thr and stellar properties of high-mass NSs, which can be employed for direct EoS constraints or consistency checks. (abridged)Comment: 35 pages, 13 figures, 14 tables, accepted for publication in Phys. Rev.

Profiling of proteins secreted in the bovine oviduct reveals diverse functions of this luminal microenvironment

<div><p>The oviductal microenvironment is a site for key events that involve gamete maturation, fertilization and early embryo development. Secretions into the oviductal lumen by either the lining epithelium or by transudation of plasma constituents are known to contain elements conducive for reproductive success. Although previous studies have identified some of these factors involved in reproduction, knowledge of secreted proteins in the oviductal fluid remains rudimentary with limited definition of function even in extensively studied species like cattle. In this study, we used a shotgun proteomics approach followed by bioinformatics sequence prediction to identify secreted proteins present in the bovine oviductal fluid (<i>ex vivo</i>) and secretions from the bovine oviductal epithelial cells (<i>in vitro</i>). From a total of 2087 proteins identified, 266 proteins could be classified as secreted, 109 (41%) of which were common for both <i>in vivo</i> and <i>in vitro</i> conditions. Pathway analysis indicated different classes of proteins that included growth factors, metabolic regulators, immune modulators, enzymes, and extracellular matrix components. Functional analysis revealed mechanisms in the oviductal lumen linked to immune homeostasis, gamete maturation, fertilization and early embryo development. These results point to several novel components that work together with known elements mediating functional homeostasis, and highlight the diversity of machinery associated with oviductal physiology and early events in cattle fertility.</p></div