Core Mass Research Articles

Forming giant planets around late-M dwarfs: Pebble accretion and planet–planet collision

We propose a pebble-driven core accretion scenario to explain the formation of giant planets around the late-M dwarfs of M★=0.1– 0.2 M⊙. In order to explore the optimal disk conditions for giant planet, we performed N-body simulations to investigate the growth and dynamical evolution of both single and multiple protoplanets in the disks with both inner viscously heated and outer stellar irradiated regions. The initial masses of the protoplanets are either assumed to be equal to 0.01 M⊕ or calculated based on the formula derived from streaming instability simulations. Our findings indicate that massive planets are more likely to form in disks with longer lifetimes, higher solid masses, moderate to high levels of disk turbulence, and larger initial masses of protoplanets. In the single protoplanet growth cases, the highest planet core mass that can be reached is generally lower than the threshold necessary to trigger rapid gas accretion, which impedes the formation of giant planets. Nonetheless, in multi-protoplanet cases, the cores can exceed the pebble isolation mass barrier aided by frequent planet–planet collisions. This consequently speeds their gas accretion up and promotes giant planet formation, making the optimal parameter space to grow giant planets substantially wider. Taken together, our results suggest that even around very-low-mass stellar hosts, the giant planets with orbital periods of ≲100 days are still likely to form when lunar-mass protoplanets first emerge from planetesimal accretion and then grow rapidly by a combination of pebble accretion and planet–planet collisions in disks with a high supply of a pebble reservoir >50 M⊕ and a turbulent level of αt ~ 10−3−10−2.

Effects of tidal deformation on planetary phase curves

With the continuous improvement in the precision of exoplanet observations, it has become feasible to probe for subtle effects that can enable a more comprehensive characterization of exoplanets. A notable example is the tidal deformation of ultra-hot Jupiters by their host stars, whose detection can provide valuable insights into the planetary interior structure. In this work we extend previous research on modeling deformation in transit light curves by proposing a straightforward approach to account for tidal deformation in phase curve observations. The planetary shape is modeled as a function of the second fluid Love number for radial deformation h2f. For a planet in hydrostatic equilibrium, h2f provides constraints on the interior structure of the planet. We show that the effect of tidal deformation manifests across the full orbit of the planet as its projected area varies with phase, thereby allowing us to better probe the planet’s shape in phase curves than in transits. Comparing the effects and detectability of deformation by different space-based instruments (JWST, HST, PLATO, CHEOPS, and TESS), we find that the effect of deformation is more prominent in infrared observations where the phase curve amplitude is the largest. A single JWST phase curve observation of a deformed planet, such as WASP-12 b, can allow up to a 17σ measurement of h2f compared to 4σ from transit-only observation. This high-precision h2f measurement can constrain the core mass of the planet to within 19% of the total mass, thus providing unprecedented constraints on the interior structure. Due to the lower phase curve amplitudes in the optical, the other instruments provide ≤ 4σ precision on h2f depending on the number of phase curves observed. We also find that detecting deformation from infrared phase curves is less affected by uncertainty in limb darkening, unlike detection in transits. Finally, the assumption of sphericity when analyzing the phase curve of deformed planets can lead to biases in several system parameters (radius, dayside and nightside temperatures, and hotspot offset, among others), thereby significantly limiting their accurate characterization.

Metal-enriched Pair-instability Supernovae: Effects of Rotation

In this paper, we revisit metal-enriched rotating pair-instability supernovae (PISNe) models for metallicities consistent with the Small Magellanic Cloud, the Large Magellanic Cloud (LMC), and 0.1Z ⊙. By calculating multiple models, we intend to clarify mass ranges and the ejected 56Ni masses from the PISNe, and mass-loss histories for progenitors. We find that the choice of the Wolf–Rayet (WR) mass-loss rates is important, and we adopt the recently proposed rate of Sander & Vink, which covers the mass ranges for PISNe progenitors. We show that slow rotation lowers the PISN range because the core mass increases by rotational mixing. On the other hand, when we assume a typical rotation speed for observed OB stars, the mass-loss increase becomes more significant, and the final stellar masses are lower than in nonrotating models. As a result, the typical mass range for bright supernovae (SNe), with a 56Ni mass higher than 10M ⊙ for these fast-rotating models is more than 400 and 350M ⊙ for LMC and 0.1Z ⊙ metallicities, respectively. It is interesting that unlike in previous works, we find oxygen-rich progenitors for most cases. This O-rich progenitor may be consistent with the recently identified PISN candidate SN2018ibb. He-rich progenitors are seen only for relatively dim and metal-poor (Z ≲ 0.1Z ⊙) PISNe. We also discuss the black hole mass gap for metal-enriched PISNe, and we show that the upper bound for the gap is lower than in the Population III case.

A possible critical heating from decay reaction and new upper limit of the magnetic monopole flux for the supermassive white dwarfs

We present the new upper limit of the magnetic monopole (MM) flux and discuss three MM models of the heating resource for supermassive white dwarfs (WDs) by considering the effect of temperature on thermonuclear reaction and mass radius relation of WDs based on the catalytic nuclear decay by MM. We discuss the luminosity and compared it with the observations to apply to 25 supermassive WDs. We find the maxnium of the number of MM captured can be 9.6943×1011\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.6943\ imes 10^{11}$$\\end{document}, and 9.0671×1011\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.0671\ imes 10^{11}$$\\end{document} for O+Ne core high mass WDs (e.g., WD J055631.17+130639.78), and C+O core high mass WDs (e.g., WD J055631.17+130639.78), respectively. The luminosities increase with the increasing of the temperature and are agreed well with the observations for model (III). The differences are no more than one, and three orders of magnitude higher than observations for model (III), and (I, II), respectively. Finaly, we find that the maxnium of the upper limits of the MM flux ϕm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi _{m}$$\\end{document} due to RC effect can be 9.1071×10-15\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.1071\ imes 10^{-15}$$\\end{document}, and 2.7670×10-14\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2.7670\ imes 10^{-14}$$\\end{document} for O+Ne and C+O core high mass WDs, respectively. Our results are about one and two orders of magnitude higher than those of Abbasi et al. (EPJC 69:361, 2010) (Albert et al. in JHEP 07:054, 2017) for O+Ne, and C+O core mass WDs, respectively, and can be about three and four orders of magnitude higher than those of Aartsen et al. (EPJC 76:133, 2016) (Ic40, Ic86), respectively. Our results show that the monopole-catalyzed nucleon decay could prevent WDs from cooling down into a stellar graveyard by keeping them hot.

The dynamic centres of infrared-dark clouds and the formation of cores

ABSTRACT High-mass stars have an enormous influence on the evolution of the interstellar medium in galaxies, so it is important that we understand how they form. We examine the central clumps within a sample of seven infrared-dark clouds (IRDCs) with a range of masses and morphologies. We use 1-pc-scale observations from the Northern Extended Millimeter Array (NOEMA) and the IRAM 30m telescope to trace dense cores with 2.8-mm continuum, and gas kinematics in C18O, HCO+, HNC, and N2H+ (J = 1–0). We supplement our continuum sample with six IRDCs observed at 2.9 mm with the Atacama Large Millimeter/submillimeter Array (ALMA), and examine the relationships between core- and clump-scale properties. We have developed a fully automated multiple-velocity component hyperfine line-fitting code called mwydyn which we employ to trace the dense gas kinematics in N2H+ (1–0), revealing highly complex and dynamic clump interiors. We find that parsec-scale clump mass is the most important factor driving the evolution; more massive clumps are able to concentrate more mass into their most massive cores – with a log-normally distributed efficiency of around 9 per cent – in addition to containing the most dynamic gas. Distributions of linewidths within the most massive cores are similar to the ambient gas, suggesting that they are not dynamically decoupled, but are similarly chaotic. A number of studies have previously suggested that clumps are globally collapsing; in such a scenario, the observed kinematics of clump centres would be the direct result of gravity-driven mass inflows that become ever more complex as the clumps evolve, which in turn leads to the chaotic mass growth of their core populations.

Growth of Massive Molecular Cloud Filament by Accretion Flows. I. Slow-shock Instability versus Ambipolar Diffusion

The Herschel Gould Belt Survey showed that stars form in dense filaments in nearby molecular clouds. Recent studies suggest that massive filaments are bound by the slow shocks caused by accretion flows onto the filaments. The slow shocks are known to be unstable to corrugation deformation of the shock front. Corrugation instability could convert the accretion flow's ram pressure into turbulent pressure that influences the width of the filament, which, according to theory, determines the self-gravitational fragmentation scale and core mass. In spite of its importance, the effect of slow-shock instability on star-forming filaments has not been investigated. In addition, the linear dispersion relation obtained from ideal magnetohydrodynamics (MHD) analysis shows that the most unstable wavelength of shock corrugation is infinitesimally small. In the scale of dense filaments, the effect of ambipolar diffusion can suppress the instability at small scales. This study investigates the influence of ambipolar diffusion on the instability of the slow shock. We perform two-dimensional MHD simulations to examine the linear growth of the slow-shock instability, considering the effect of ambipolar diffusion. The results demonstrate that the most unstable scale of slow-shock instability is approximately 5 times the length scale of ambipolar diffusion ℓ AD calculated using post-shock variables, where ℓ AD corresponds to the scale where the magnetic Reynolds number for ambipolar diffusivity is unity.

Characterizing the Ordinary Broad-line Type Ic SN 2023pel from the Energetic GRB 230812B

We report observations of the optical counterpart of the long gamma-ray burst (GRB) GRB 230812B and its associated supernova (SN) SN 2023pel. The proximity (z = 0.36) and high energy (E γ,iso ∼ 1053 erg) make it an important event to study as a probe of the connection between massive star core collapse and relativistic jet formation. With a phenomenological power-law model for the optical afterglow, we find a late-time flattening consistent with the presence of an associated SN. SN 2023pel has an absolute peak r-band magnitude of M r = −19.46 ± 0.18 mag (about as bright as SN 1998bw) and evolves on quicker timescales. Using a radioactive heating model, we derive a nickel mass powering the SN of M Ni = 0.38 ± 0.01 M ⊙ and a peak bolometric luminosity of L bol ∼ 1.3 × 1043 erg s−1. We confirm SN 2023pel’s classification as a broad-line Type Ic SN with a spectrum taken 15.5 days after its peak in the r band and derive a photospheric expansion velocity of v ph = 11,300 ± 1600 km s−1 at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta mass M ej = 1.0 ± 0.6 M ⊙ and kinetic energy EKE=1.3−1.2+3.3×1051erg . We find that GRB 230812B/SN 2023pel has SN properties that are mostly consistent with the overall GRB-SN population. The lack of correlations found in the GRB-SN population between SN brightness and E γ,iso for their associated GRBs across a broad range of 7 orders of magnitude provides further evidence that the central engine powering the relativistic ejecta is not coupled to the SN powering mechanism in GRB-SN systems.

Spatial Characterization of Sports Economic Linkages - Based on an Evolutionary Game Theory Perspective

Abstract There exists an important connection between the development of the sports economy and the development of spatial characteristics, but the current development of spatial characteristics of sports economic linkages suffers from the lack of identification and screening of the subjects of interest and the inability to articulate the structure of the interests of each subject. The article adopts the research paradigm based on rooted theory to encode the game phenomenon of the spatial characteristics of sports economic linkages and constructs an evolutionary game model that integrates the sports administrative regulator, the supply side of community public sports services, and the demand side. The optimal equilibrium strategy to promote the sustainable development of urban community public sports services spatial governance is also explored by combining the Jacobian matrix and simulation experiments. Although the tripartite subjects play different dynamic roles at different stages of transformation, they all converge to the steady state of (1, 1, 1) in the end. In addition, the three have different evolutionary processes. First, the probability of choosing the support strategy in the economic core area decreases and then rises, while the probability of government support and mass recognition both increase. The economic core area, government support, and mass recognition are all experiencing a gradual increase. Finally, the probability of mass recognition shows a first decline and then a rise, while the probability of economic core area and government support continues to show an increase, and the three finally evolve into a (1, 1, 1) strategy steady state.

Photometric binaries in 14 Magellanic Cloud star clusters

Binary stars play a major role in determining the dynamic evolution of star clusters. We used images collected with the Hubble Space Telescope to study fourteen star clusters of the Magellanic Clouds that span an age interval between ∼0.6 and 2.1 Gyr and masses of 104 − 105 M⊙. We estimated the fraction of binary systems composed of two main-sequence stars and the fraction of candidate blue-straggler stars (BSSs). Moreover, we derived the structural parameters of the cluster, including the core radius, central density, mass function, and total mass. We find that the fraction of binaries with a mass ratio larger than 0.7 ranges from ∼7% in NGC 1846 to ∼20% in NGC 2108. The radial and luminosity distribution can change from one cluster to another. However, when we combine the results from all the clusters, we find that binaries follow a flat radial trend and no significant correlation with the mass of the primary star. We find no evidence for a relation between the fractions of binaries and BSSs. We combined the results on binaries in the studied Magellanic Cloud clusters with those obtained for 67 Galactic globular clusters and 78 open clusters. We detect a significant anti-correlation between the binary fraction in the core and the mass of the host cluster. However, star clusters with similar masses exhibit a wide range of binary fractions. Conversely, there is no evidence of a correlation between the fraction of binaries and the cluster age or the dynamic age.

Integrated high performance microfluidic organic analysis instrument for planetary and space exploration.

The exploration of our solar system to characterize the molecular organic inventory will enable the identification of potentially habitable regions and initiate the search for biosignatures of extraterrestrial life. However, it is challenging to perform the required high-resolution, high-sensitivity chemical analyses in space and in planetary environments. To address this challenge, we have developed a microfluidic organic analyzer (MOA) instrument that consists of a multilayer programmable microfluidic analyzer (PMA) for fluidic processing at the microliter scale coupled with a microfabricated glass capillary electrophoresis (CE) wafer for separation and analysis of the sample components. Organic analytes are labeled with a functional group-specific (e.g. amine, organic acid, aldehyde) fluorescent dye, separated according to charge and hydrodynamic size by capillary electrophoresis (CE), and detected with picomolar limit of detection (LOD) using laser-induced fluorescence (LIF). Our goal is a sensitive automated instrument and autonomous process that enables sample-in to data-out performance in a flight capable format. We present here the design, fabrication, and operation of a technology development unit (TDU) that meets these design goals with a core mass of 3 kg and a volume of <5 L. MOA has a demonstrated resolution of 2 × 105 theoretical plates for relevant amino acids using a 15 cm long CE channel and 467 V cm-1. The LOD of LIF surpasses 100 pM (0.01 ppb), enabling biosignature detection in harsh environments on Earth. MOA is ideally suited for probing biosignatures in potentially habitable destinations on icy moons such as Europa and Enceladus, and on Mars.

Baryon-induced Collapse of Dark Matter Cores into Supermassive Black Holes

Nonlinear structure formation for fermionic dark matter particles leads to dark matter density profiles with a degenerate compact core surrounded by a diluted halo. For a given fermion mass, the core has a critical mass that collapses into a supermassive black hole (SMBH). Galactic dynamics constraints suggest a ∼100 keV/c 2 fermion, which leads to ∼107 M ⊙ critical core mass. Here, we show that baryonic (ordinary) matter accretion drives an initially stable dark matter core to SMBH formation and determines the accreted mass threshold that induces it. Baryonic gas density ρ b and velocity v b inferred from cosmological hydrosimulations and observations produce sub-Eddington accretion rates triggering the baryon-induced collapse in less than 1 Gyr. This process produces active galactic nuclei in galaxy mergers and the high-redshift Universe. For TXS 2116–077, merging with a nearby galaxy, the observed 3 × 107 M ⊙ SMBH, for Qb=ρb/vb3=0.125M⊙/(100kms−1pc)3 , forms in ≈0.6 Gyr, consistent with the 0.5–2 Gyr merger timescale and younger jet. For the farthest central SMBH detected by the Chandra X-ray satellite in the z = 10.3 UHZ1 galaxy observed by the James Webb Space Telescope (JWST), the mechanism leads to a 4 × 107 M ⊙ SMBH in 87–187 Myr, starting the accretion at z = 12–15. The baryon-induced collapse can also explain the ≈107–108 M ⊙ SMBHs revealed by JWST at z ≈ 4–6. After its formation, the SMBH can grow to a few 109 M ⊙ in timescales shorter than 1 Gyr via sub-Eddington baryonic mass accretion.

Analysis of the Sum Minimization Possibilities of Heat Exchanger Core Masses in Internal Combustion Engine Cooling Systems

Rational designs for cooling systems (CS) of internal combustion engines are formulated in the form of a series of circulation circuits. The engine is integrated into a circuit with the highest and unregulated flow of internal circuit coolant (ICC). All heat exchangers are placed in circulation circuits with relatively reduced and adjustable ICC flow rates. While the circuits are usually interconnected, they can also be designed to operate independently. This CS scheme enables the achievement of the minimum possible value of the sum of masses of exchanger cores, denoted as MΣ. The reduction in MΣ is achieved through the regulation of ICC flow in a closed circulation loop involving two heat exchangers. The variations in MΣ based on the circuit parameters have been thoroughly investigated. The reduction in MΣ can also be applicable to more intricate systems. A decrease in MΣ, under identical initial CS parameters, may occur in different magnitudes, depending on the specific features of the CS scheme and the operating conditions of the heat exchangers within it. Cooling systems, constructed with the same initial parameters and comprising multiple circulation circuits that meet all criteria for rational design, may exhibit diverse configurations. Examples of such systems are explored, and the minimum values of MΣ are calculated for each. It has been determined that the disparity in the minimum values of MΣ for such systems, while maintaining equal efficiency, can exceed 30%. The selection of the optimal CS scheme is contingent not only on achieving the minimum possible value of MΣ but also on various other factors.

The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE): Core Growth, Cluster Contraction, and Primordial Mass Segregation

The Atacama Large Millimeter/submillimeter Array (ALMA) Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE) aims to investigate the process of mass assembly and its connection to high-mass star formation theories in protoclusters in a dynamic view. We observed 11 massive (M clump ≳ 103 M ⊙), luminous (L bol ≳ 104 L ⊙), and blue-profile (infall signature) clumps by ALMA with resolution of ∼2200–5500 au (median value of 3500 au) at 350 GHz (870 μm). We identified 248 dense cores, including 106 cores showing protostellar signatures and 142 prestellar core candidates. Compared to early stage infrared dark clouds (IRDCs) by ASHES, the core mass and surface density within the ASSEMBLE clumps exhibited a significant increment, suggesting concurrent core accretion during the evolution of the clumps. The maximum mass of prestellar cores was found to be 2 times larger than that in IRDCs, indicating that evolved protoclusters have the potential to harbor massive prestellar cores. The mass relation between clumps and their most massive core (MMCs) is observed in ASSEMBLE but not in IRDCs, which is suggested to be regulated by multiscale mass accretion. The mass correlation between the core clusters and their MMCs has a steeper slope compared to that observed in stellar clusters, which can be due to fragmentation of the MMC and stellar multiplicity. We observe a decrease in core separation and an increase in central concentration as protoclusters evolve. We confirm primordial mass segregation in the ASSEMBLE protoclusters, possibly resulting from gravitational concentration and/or gas accretion.

Mass and efficiency optimization of a He-Xe Brayton cycle for mobile, land-based nuclear microreactors

Nuclear microreactors represent an option for distributed power generation, which can be deployed in military installations, remote off-grid villages, and locations recovering from natural disasters. Small system mass is necessary to achieve their mobility. In this study, a He-Xe gas-cooled reactor coupled with a Closed Brayton cycle (CBC) is optimized in terms of system mass and thermal efficiency. A single-channel model is developed for the reactor to predict the minimum mass according to the thermal–hydraulic limitations. Masses of the heat exchanger and turbo-machines are calculated based on empirical curves. The simple regenerative and intercooling cycles are considered. A parametric study is conducted to investigate the influence of key parameters on system mass and to explore the tradeoffs between different components that satisfy the power requirements of 8 MWe. Furthermore, the Non-dominated Sorting Genetic Algorithm (NSGA-II) is used to optimize the system mass and thermal efficiency. Optimal values of critical parameters on the Pareto Frontier are presented and discussed. Results show that the masses of the reactor core and coolers dominate the total mass in most cases, and increasing the height of the reactor core can help reduce the system mass by allowing a smaller core radius. The Pareto Frontier shows that at thermal efficiencies around 40% or below, the system mass is depressed by using large CPR, molecular weight of the mixture, height of the reactor core, and small recuperator effectiveness. Increasing the recuperator's effectiveness from about 90% is required for higher thermal efficiency design, but its mass increases dramatically and can surpass the mass share of other components. The current analysis can provide a guide for detailed system and component design.

ALMA-IMF. IX. Catalog and Physical Properties of 315 SiO Outflow Candidates in 15 Massive Protoclusters

We present a catalog of 315 protostellar outflow candidates detected in SiO J = 5 − 4 in the ALMA-IMF Large Program, observed with ∼2000 au spatial resolution, 0.339 km s−1 velocity resolution, and 2–12 mJy beam−1 (0.18–0.8 K) sensitivity. We find median outflow masses, momenta, and kinetic energies of ∼0.3 M ⊙, 4 M ⊙ km s−1, and 1045 erg, respectively. Median outflow lifetimes are 6000 yr, yielding median mass, momentum, and energy rates of Ṁ = 10−4.4 M ⊙ yr−1, Ṗ = 10−3.2 M ⊙ km s−1 yr−1, and Ė = 1 L ⊙. We analyze these outflow properties in the aggregate in each field. We find correlations between field-aggregated SiO outflow properties and total mass in cores (∼3σ–5σ), and no correlations above 3σ with clump mass, clump luminosity, or clump luminosity-to-mass ratio. We perform a linear regression analysis and find that the correlation between field-aggregated outflow mass and total clump mass—which has been previously described in the literature—may actually be mediated by the relationship between outflow mass and total mass in cores. We also find that the most massive SiO outflow in each field is typically responsible for only 15%–30% of the total outflow mass (60% upper limit). Our data agree well with the established mechanical force−bolometric luminosity relationship in the literature, and our data extend this relationship up to L ≥ 106 L ⊙ and Ṗ ≥ 1 M ⊙ km s−1 yr−1. Our lack of correlation with clump L/M is inconsistent with models of protocluster formation in which all protostars start forming at the same time.

Stellar Neutrino Emission across the Mass–Metallicity Plane

We explore neutrino emission from nonrotating, single-star models across six initial metallicities and 70 initial masses from the zero-age main sequence to the final fate. Overall, across the mass spectrum, we find metal-poor stellar models tend to have denser, hotter, and more massive cores with lower envelope opacities, larger surface luminosities, and larger effective temperatures than their metal-rich counterparts. Across the mass–metallicity plane we identify the sequence (initial CNO → 14N → 22Ne → 25Mg → 26Al → 26Mg → 30P → 30Si) as making primary contributions to the neutrino luminosity at different phases of evolution. For the low-mass models we find neutrino emission from the nitrogen flash and thermal pulse phases of evolution depend strongly on the initial metallicity. For the high-mass models, neutrino emission at He-core ignition and He-shell burning depends strongly on the initial metallicity. Antineutrino emission during C, Ne, and O burning shows a strong metallicity dependence with 22Ne(α, n)25Mg providing much of the neutron excess available for inverse-β decays. We integrate the stellar tracks over an initial mass function and time to investigate the neutrino emission from a simple stellar population. We find average neutrino emission from simple stellar populations to be 0.5–1.2 MeV electron neutrinos. Lower metallicity stellar populations produce slightly larger neutrino luminosities and average β decay energies. This study can provide targets for neutrino detectors from individual stars and stellar populations. We provide convenient fitting formulae and open access to the photon and neutrino tracks for more sophisticated population synthesis models.

Investigating the spatial representativeness of East Antarctic ice cores: a comparison of ice core and radar-derived surface mass balance over coastal ice rises and Dome Fuji

Abstract. Surface mass balance (SMB) of the Antarctic Ice Sheet must be better understood to document the current Antarctic contribution to sea-level rise. In situ point data using snow stakes and ice cores are often used to evaluate the state of the ice sheet's mass balance, as well as to assess SMB derived from regional climate models, which are then used to produce future climate projections. However, spatial representativeness of individual point data remains largely unknown, particularly in the coastal regions of Antarctica with highly variable terrain. Here, we compare ice core data collected at the summit of eight ice rises along the coast of Dronning Maud Land, as well as at the Dome Fuji site, and shallow ice-penetrating radar data over these regions. Shallow radar data have the advantage of being spatially extensive, with a temporal resolution that varies between a yearly and multi-year resolution, from which we can derive a SMB record over the entire radar survey. This comparison therefore allows us to evaluate the spatial variability of SMB and the spatial representativeness of ice-core-derived SMB. We found that ice core mean SMB is very local, and the difference with radar-derived SMB increases in a logarithmic fashion as the surface covered by the radar data increases, with a plateau ∼ 1–2 km away from the ice crest for most ice rises, where there are strong wind–topography interactions, and ∼ 10 km where the ice shelves begin. The relative uncertainty in measuring SMB also increases rapidly as we move away from the ice core sites. Five of our ice rise sites show a strong spatial representativeness in terms of temporal variability, while the other three sites show that it is limited to a surface area between 20–120 km2. The Dome Fuji site, on the other hand, shows a small difference between pointwise and area mean SMB, as well as a strong spatial representativeness in terms of temporal variability. We found no simple parameterization that could represent the spatial variability observed at all the sites. However, these data clearly indicate that local spatial SMB variability must be considered when assessing mass balance, as well as comparing modeled SMB values to point field data, and therefore must be included in the estimate of the uncertainty of the observations.

How to make giant planets via pebble accretion

Planet formation is directly linked to the birthing environment that protoplanetary disks provide. The disk properties determine whether a giant planet will form and how it evolves. The number of exoplanet and disk observations is consistently rising, however, it is not yet possible to directly link these two populations. Therefore, a deep theoretical understanding of how planets form is crucial. Giant planets are not the most common exoplanets, but their presence in a disk can have significant consequences for the evolution of the disk itself and the planetary system undergoing formation. Their presence also offers more chances of spotting observational features in the disk structure. We performed numerical simulations of planet formation via pebble and gas accretion, while including migration, in a viscously evolving protoplanetary disk, with dust growing, drifting, and evaporating at the ice lines. In our investigation of the most favorable conditions for giant planet formation, we find that these are high disk masses, early formation, and a large enough disk to host a long-lasting pebble flux, so that efficient core growth can take place before the pebble flux decays over time. Specifically, core growth needs to start before 0.9 Myr to form a giant, with an initial disk mass of 0.04 M⊙ (or higher) and the disk radius needs to be larger than 50 AU. However, small disks with the same mass allow more efficient gas accretion onto already formed planetary cores, leading to more massive gas giants. Given the right conditions, high viscosity (α = 10−3) leads to more massive cores (compared to α = 10−4) and it also enhances gas accretion. At the same time, it causes faster type II migration rates, so the giants have a decreasing final position for increasing viscosity. Intermediate dust fragmentation velocities, between 4 and 7 m s−1, provide the necessary pebble sizes and radial drift velocities for maximized pebble accretion with optimal pebble flux. The starting location of a planetary embryo defines whether a giant planet will form, with the highest fraction of giants originating between 5 and 25 AU. Finally, a dust-to-gas ratio of 0.03 can compensate for lower disk masses with fDG ≤ 0.015, but early formation is still important in order to form giant planets. We conclude that there is no specific initial parameter that leads to giant planet formation; rather, it is the outcome of a combination of complementary factors. This also implies that the diversity of the exoplanet systems is the product of the intrinsic diversity of the protoplanetary disks and it is crucial to take advantage of the increasing number and quality of observations to constrain the disk population properties and ultimately devise planet formation theories.

Photovoltaic/thermal (PV/T) solar collectors employing phase-change nano-capsules as spectral filters: Coupled, decoupled, and partially-coupled configurations

The ineffective utilization of solar radiation poses negative impacts on the performance of photovoltaic (PV) cells in terms of their efficiency and durability. For the first time, this study numerically introduces a comparative performance analysis between multiple PV/T configurations (thermally decoupled, coupled, and partially coupled) that employ nano-encapsulated phase-change material (nano-ePCM) dispersions. The dispersions act as multi-functional fluids that can optically filter incident radiation to fit the spectral response of Si PV cells, and serve as both heat carriers and storage media to effectively cool PV cells. The water-dispersed ePCM particles are made of silica shells and paraffin cores. The numerical model developed for the proposed configurations mainly comprises of three mathematical models (thermal, optical, and electrical) that are coupled together to simulate the performance of the novel systems. To ensure that the presented results are of high accuracy and credibility, the optical, electrical, and thermal models were rigorously validated against published data. Performance of the three PV/T configurations was comparatively analyzed upon varying the PCM core material, mass flowrate, channel depth, inlet and ambient temperatures, and wind speed. The utilized dispersion exhibited a 73.8% spectral match with Si PV cells, thus hinting at the effective spectral filtration capabilities of the designed fluid. When compared to similar PV/T configurations from different literatures, total exergy efficiency enhancements of 43.2%, 76.8%, and 2.6% were evident for the coupled, decoupled, and partially coupled systems, respectively. In addition, results have shown that the thermally decoupled system outperforms the coupled and partially coupled systems in terms of thermal performance but exhibits the poorest performance when superior electrical performance is desired.

Evolutionary tracks of massive stars with different rotation and metallicity in neutrino H–R diagram

ABSTRACT Neutrino losses play a crucial role in the evolution of massive stars. We study the neutrino luminosity of stars ranging from 20 to 90 $\rm M_{\odot }$ from Zero Age Main Sequence to Fe Core Collapse (FeCC) with different rotation and metallicity in a neutrino Hertzsprung–Russell diagram. In our simulations, we consider $\rm \omega /\omega _{crit}= 0$ and 0.7 to represent non-rotation and high rotation, respectively, and set the metallicities to 0.014, 0.001, and 0.0001. During hydrogen burning stages, neutrino luminosity primarily originates from CNO cycle, and increases with higher stellar mass while decreasing with increasing metallicity. For the high metallicity models (Z = 0.014) during the helium burning stage, the reduction of the hydrogen envelope caused by a larger mass loss rate leads to a gradual decrease in neutrino luminosity. The rapid rotation results in extra mixing inside massive stars, which increases the neutrino luminosity during main sequence, while decreases the neutrino luminosity during helium burning phase. Simultaneously, the rapid rotation also increases CO core mass, which enhances the neutrino luminosity during C and O burning phase. We also investigate the effect of neutrino magnetic moment (NMM) on the massive stars. We find that the energy loss caused by the NMM does not have effects on the evolutionary destiny of massive stars, and it does not significant change the compactness at the time of FeCC.