Solar Masses Research Articles

Spectral Indices and Evidence of Wave–Wave Modulation in Observations of the Interplanetary Magnetic Field

We present wave and turbulence observations from the DSCOVR spacecraft during the 2017 September solar flare and coronal mass ejection (CME) events. On September 4–12, the spectral index within the magnetic field power spectral density inertial range was consistent with Kolmogorov −5/3. This is despite the 9 days being composed of a complex mix of different features, including solar flares, solar energetic particle events, and CMEs. When analyzing shorter time periods, the spectral index varies. For two days where there were consecutive CMEs, the index follows Kraichnan–Iroshinikov −3/2, while on two quiet days, it was a mixture of −1, −3/2, and −2. The inertial range spectral index taken over the entire 9 days hides or averages out spectral features that occur over shorter time periods. We use a more realistic estimate of the amount of Doppler shifting into the spacecraft frame to show that the break frequencies on most days were located close to the H+ cyclotron frequency. We present evidence of wave–wave modulation and suggest that lower-frequency waves in the solar wind can modulate the growth rates/propagation of ion cyclotron waves, providing a method to transfer energy in the solar wind to smaller scales. Furthermore, we suggest that the indices in the inertial range can be explained by combining containment due to wave generation/propagation and stochastic Brownian motion in the solar wind. When these two phenomena are equal, they combine to create a −3/2 index.

Low-dimensional signal representations for massive black hole binary signals analysis from LISA data

The space-based gravitational wave observatory LISA will provide a wealth of information to analyze massive black hole binaries with high chirp masses, beyond $10^5$ solar masses. The large number of expected MBHBs (one event a day on average) increases the risk of overlapping between events. As well, the data will be contaminated with non-stationary artifacts, such as glitches and data gaps, which are expected to strongly impact the MBHB analysis, which mandates the development of dedicated detection and retrieval methods on long time intervals. Building upon a methodological approach we introduced for galactic binaries, in this article we investigate an original non-parametric recovery of MBHB signals from measurements with instrumental noise typical of LISA in order to tackle detection and signal reconstruction tasks on long time intervals. We investigated different approaches based on sparse signal modeling and machine learning. In this framework, we focused on recovering MBHB waveforms on long time intervals, which is a building block to further tackling more general signal recovery problems, from gap mitigation to unmixing overlapped signals. To that end, we introduced a hybrid method called SCARF (sparse chirp adaptive representation in Fourier), which combines a deep learning modeling of the merger of the MBHB with a specific adaptive time-frequency representation of the inspiral. Numerical experiments have been carried out on simulations of single MBHB events that account for the LISA response and with realistic realizations of noise. We checked the performances of the proposed hybrid method for the fast detection and recovery of the MBHB.

Hints of entanglement suppression in hyperon-nucleon scattering

Hyperon (Y=Σ,Λ)-nucleon (N=n,p) interactions are crucial for understanding the existence of neutron stars heavier than two solar masses. Amid renewed experimental efforts, we study YN scatterings from the perspective of quantum information, focusing on whether spin entanglement is suppressed in the s-wave channel, which is observed in np scattering and leads to enhanced global symmetries. Using global fits of phase shifts from experimental data, we find hints of entanglement suppression among the eight flavor channels in the strangeness S=−1 sector, similar to the np case. One exception is the Σ+p channel, where conflicting global fits lead to inconclusive outcome. We then propose “quantum” observables in Σ+p scattering to help resolve the differing global fits.

The gravitational-wave emission from the explosion of a 15 solar mass star with rotation and magnetic fields

ABSTRACT Gravitational waveform predictions from 3D simulations of explosions of non-rotating massive stars with no magnetic fields have been extensively studied. However, the impact of magnetic fields and rotation on the core-collapse supernova gravitational-wave signal is not well understood beyond the core-bounce phase. Therefore, we perform four magnetohydrodynamical simulations of the explosion of a $15\, {\rm M}_{\odot }$ star with the SFHx and SFHo equations of state. All of the models start with a weak magnetic field strength of $10^{8}$ G, and two of the models are rapidly rotating. We discuss the impact of the rotation and magnetic fields on the gravitational-wave signals. We find that the weak pre-collapse fields do not have a significant impact on the gravitational-wave signal amplitude. With rapid rotation, the f/g-mode trajectory can change in shape, and the dominant emission band becomes broader. We include the low-frequency memory component of the gravitational-wave signal from both matter motions and neutrino emission anisotropy. We show that including the gravitational waves from anisotropic neutrino emission increases the supernova gravitational-wave detection distances for the Einstein Telescope. The gravitational waves from anisotropic neutrino emission would also be detectable out to Mpc distances by a moon-based gravitational-wave detector.

Building Mass Optimization to Reduce Solar Radiation in High Rise Building by Using Parametric Approach

Buildings use 40% of global primary energy, therefore their design and use affect climate change. Building performance analysis can assist architects predict performance before construction with parametric design tools. Radiance can be reduced via a parametric mass, lowering cooling load and energy use. The study uses theoretical and computational research to explain, forecast, and analyze events, whereas parametric design optimizes complicated geometries using mathematical parameters and algorithms. Environmental analysis in Grasshopper with the Ladybug plugin uses Rhinoceros. This plugin provides solar radiation, and climate analysis capabilities. To determine the most energy-efficient building design, the research links independent and dependent variables such solar radiation intensity and building mass. The study uses Surabaya weather data and high rise buildings. The land is formed like a square, with a 15-degree slope to the north and is flanked by low-rise buildings. As a result, the location receives the most direct sunlight during the day. Then, solar radiation analysis. It helps optimize passive solar design solutions. According to the modelling results, solar radiation on the top and west sides are particularly large and dominant in 65.37 and 32.69 kWh/m2. Meanwhile, the north, east and south sides receive very little solar radiation. The following simulation considers the optimal direction, which is to extend west-east and face to the south. A multi-towered megastructure is a high-rise building that responds best to solar radiation. The total solar radiation value is 3,718,100 kWh. It can accommodate large spaces with large mass composition but relatively low total solar radiation values. The building towers provide shade to each other, thereby reducing direct radiation from the sun to the building. The sides of the building's podium are also shaded, so the top of the building is partially red.

Widespread disruption of resonant chains during protoplanetary disk dispersal

We describe the evolution of low mass planets in a dispersing protoplanetary disk around a Solar mass star. The disk model is based on the results of , which describes a region of the inner disk where the direction of the migration torque is outwards due to the diffusion of the stellar magnetic field into the disk and the resultant gradual increase in surface density outwards. We demonstrate that the magnetospheric rebound phase in such a disk leads to diverging orbits for double and triple planet systems, and the disruption of a high fraction of the initial resonant chains. We present simulations of three planet systems, with masses based on the observed triple planet systems observed by the Kepler satellite, within the context of this model. The final distribution of nearest neighbour period ratios provides an excellent fit to the observations, provided that the initial configurations {}. The occurrence rate of planets as a function of orbital period also provides a good match to the observations, for final orbital periods P<20~days. These results suggest that the period and period ratio distributions of low mass planets are primarily set in place during the disk dispersal epoch, and may not require significant dynamical evolution thereafter.

GalaxyFlow: upsampling hydrodynamical simulations for realistic mock stellar catalogues

ABSTRACT Cosmological N-body simulations of galaxies operate at the level of ‘star particles’ with a mass resolution on the scale of thousands of solar masses. Turning these simulations into stellar mock catalogues requires ‘upsampling’ the star particles into individual stars following the same phase-space density. In this paper, we introduce two new upsampling methods. First, we describe GalaxyFlow, a sophisticated upsampling method that utilizes normalizing flows to both estimate the stellar phase-space density and sample from it. Secondly, we improve on existing upsamplers based on adaptive kernel density estimation (KDE), using maximum likelihood estimation to fine-tune the bandwidth for such algorithms in a way that improves both the density estimation accuracy and upsampling results. We demonstrate our upsampling techniques on a neighbourhood of the Solar location in two simulated galaxies: Auriga 6 and h277. Both yield smooth stellar distributions that closely resemble the stellar densities seen in the Gaia DR3 catalogue. Furthermore, we introduce a novel multimodel classifier test to compare the accuracy of different upsampling methods quantitatively. This test confirms that GalaxyFlow more accurately estimates the density of the underlying star particles than methods based on KDE, at the cost of being more computationally intensive.

Fast-moving stars around an intermediate-mass black hole in ω Centauri

Black holes have been found over a wide range of masses, from stellar remnants with masses of 5–150 solar masses (M☉), to those found at the centres of galaxies with M > 105M☉. However, only a few debated candidate black holes exist between 150M☉ and 105M☉. Determining the population of these intermediate-mass black holes is an important step towards understanding supermassive black hole formation in the early universe1,2. Several studies have claimed the detection of a central black hole in ω Centauri, the most massive globular cluster of the Milky Way3–5. However, these studies have been questioned because of the possible mass contribution of stellar mass black holes, their sensitivity to the cluster centre and the lack of fast-moving stars above the escape velocity6–9. Here we report the observations of seven fast-moving stars in the central 3 arcsec (0.08 pc) of ω Centauri. The velocities of the fast-moving stars are significantly higher than the expected central escape velocity of the star cluster, so their presence can be explained only by being bound to a massive black hole. From the velocities alone, we can infer a firm lower limit of the black hole mass of about 8,200M☉, making this a good case for an intermediate-mass black hole in the local universe.

Spitzer Resurrector Mission: Advantages for Space Weather Research and Operations

In 1979, NASA established the Great Observatory program, which included four telescopes (Hubble, Compton, Chandra, and Spitzer) to explore the Universe. The Spitzer Space Telescope was launched in 2003 into solar orbit, gradually drifting away from the Earth. Spitzer was operated very successfully until 2020 when NASA terminated observations and placed the telescope in safe mode. In 2028, the U.S. Space Force has the opportunity to demonstrate satellite servicing by telerobotically reactivating Spitzer for astronomical observations, and in a separate experiment, carry out novel Space Weather research and operations capabilities by observing solar Coronal Mass Ejections. This will be accomplished by launching a small satellite, the Spitzer-Resurrector Mission (SRM), to rendezvous with Spitzer in 2030, positioning itself around it, and serving as a relay for recommissioning and science operations. A sample of science goals for Spitzer is briefly described, but the focus of this paper is on the unique opportunity offered by SRM to demonstrate novel Space Weather research and operations capabilities.

Feedback in the dark: a critical examination of CMB bounds on primordial black holes

If present in the early universe, primordial black holes (PBHs) would have accreted matter and emitted high-energy photons, altering the statistical properties of the Cosmic Microwave Background (CMB). This mechanism has been used to constrain the fraction of dark matter that is in the form of PBHs to be much smaller than unity for PBH masses well above one solar mass. Moreover, the presence of dense dark matter mini-halos around the PBHs has been used to set even more stringent constraints, as these would boost the accretion rates.In this work, we critically revisit CMB constraints on PBHs taking into account the role of the local ionization of the gas around them. We discuss how the local increase in temperature around PBHs can prevent the dark matter mini-halos from strongly enhancing the accretion process, in some cases significantly weakening previously derived CMB constraints. We explore in detail the key ingredients of the CMB bound and derive a conservative limit on the cosmological abundance of massive PBHs.

Design principle of anti‐corrosive photocatalyst for large‐scale hydrogen production

AbstractWith the most advances made so far in terms of photocatalyst design and preparation (inorganic photoredox nanoparticles), researchers of different expertise joined together to address sustainable energy conversion. Despite notable advancements in creating exceptionally active photocatalysts, the practical scalability of these innovations is hindered by issues such as ineffective utilization of solar energy and mass transport, recombination reactions, catalyst instability, and photo corrosion of the catalyst. In this roadmap review, we brief the fundamentals, latest progress, outstanding challenges, and novel design methodology for anticorrosive photocatalysts favorable to large‐scale hydrogen production. To enable the effective scaling of photocatalysis, beyond the inherent activity of photocatalysts, a range of additional factors are considered, with a primary focus on the design of photocatalytic systems. This review underlines the significance of well‐structured photocatalyst design and evaluation for achieving reproducibility and using dependable research methodology for conducting rigorous experiments. The recommendations are directed at reducing the uncertainty surrounding the optimism presented in published research, and we spotlight our recent research advancements. Importantly, the synergistic integration of design principles and research methodologies to enhance the anti‐corrosion properties of photocatalysts may pave the way for a practical technology to utilize solar energy for large‐scale hydrogen production efficiently.This article is categorized under: Sustainable Energy > Solar Energy

Calculation of the TOV Limit Based on Neutron Degeneracy Pressure

Original theory on the mass limit beyond which a cold, non-rotating neutron star cannot be formed, instead only stellar black holes will be created, was stipulated by J.R. Oppenheimer and G.M. Volkoff based on R.C. Tolman’s work in 1939. The limit calculated from the equation established by them is known as the TOV limit which is analogous to the Chandrasekhar limit for White Dwarfs. But the results obtained using the formula was found to be not valid today. Subsequent theoretical works place the limit in the range 1.5 to 3 solar masses. There are several basic theories and related formulae for calculating the TOV limit. In this article a different and novel approach has been adopted to calculate the TOV limit using the theory on neutron degeneracy pressure. As per present calculations, the TOV limit is around 2.928 times the solar mass. These calculations also highlight two aspects which are conceptually new; first, a black hole having mass higher than the TOV limit can also become a neutron star and both can coexist concurrently up to a certain limit; and second, that upper limit of star mass beyond which a black hole will explode in supernova before becoming a neutron star is 7.15 times the solar mass as at that stage the gravitational energy of the black hole will be equal or exceed to its nuclear binding energy.

Pulsars with the masses 2.14M⊙ and 2.27M⊙ as strange star candidates

Strange stars with maximal masses, more than the values of recently precisely measured masses of two radio pulsars: SRJ0740+6620, with the mass 2.14М⊙, and PSRJ2215+5135, with the mass 2.27М⊙, have been studied. For the examination of strange quark matter (SQM), the bag model, developed in Massachusetts Technological Institute was chosen. The observed bag model depends on vacuum pressure B, quark-gluon interaction constant αc, and strange quark mass ms. Since the transition to SQM state takes place at the energy density, not exceeding double density in atomic nuclei, neutron stars with small mass and configuration, consisting of SQM, form one family in the dependence curve of the mass M, of the equilibrium super-dense configurations, on the energy central density ρc (curve M(ρc)). The state equation of strange quark matter was studied when the vacuum pressure was constant. Groups of the values of these parameters were determined; their application in the state equation of SQM leads to the maximal mass of the equilibrium quark configurations Mmax, which are heavier than the aforementioned radio pulsars. For such configurations, the values of mass, radius, the entire number of baryons, red shift from the strange star surface were calculated, depending on the energy central density ρc. For each series with Mmax>2.14M⊙ and Mmax>2.27M⊙ the values of the mentioned integral parameters were calculated as well for super-dense configurations with 2.27and2.14 solar masses that were precisely determined from observations. According to the obtained state equations, these two radio pulsars can be the possible candidates for the strange stars.

Analysis of the drying kinetics of sargassum using direct solar dryer and solar energy direct

This paper presents the analysis of the kinetics of sargassum drying using a direct solar dryer and the direct energy from the sun. Four mathematical models were applied: Newton, Page, Henderson and Pabis; and Midilli et al. The seaweed was brought from the coast of Cancun, Q. R, Mexico. With the direct solar dryer, a total of 6 hours were required to dry it, the final humidity ratio was 0.013. In the case of solar energy without dryer, i. e., in open air, 12 hours were required in two non-consecutive periods, and the final humidity ratio was 0.025. The solar radiation values, temperatures and mass variation were obtained as a function of time. The kinetic model that best simulated the drying process was that of Anderson and Pabis, obtained after the statistical analysis was performed, the activation energy was also obtained.

Source Region and Launch Characteristics of Magnetic-arch-blowout Solar Coronal Mass Ejections Driven by Homologous Compact-flare Blowout Jets

We study the formation of four coronal mass ejections (CMEs) originating from homologous blowout jets. All of the blowout jets originated from NOAA Active Region (AR) 11515 on 2012 July 2, within a time interval of ≈14 hr. All of the CMEs were wide (angular widths ≈ 95°–150°), and propagated with speeds ranging between ≈300 and 500 km s−1 in LASCO coronagraph images. Observations at various EUV wavelengths in Solar Dynamics Observatory/Atmospheric Imaging Assembly images reveal that in all the cases, the source region of the jets lies at the boundary of the leading part of AR 11515 that hosts a small filament before each event. Coronal magnetic field modeling based on nonlinear force-free extrapolations indicates that in each case, the filament is contained inside of a magnetic flux rope that remains constrained by overlying compact loops. The southern footpoint of each filament is rooted in the negative polarity region where the eruption onsets occur. This negative polarity region undergoes continuous flux changes, including emergence and cancellation with opposite polarity in the vicinity of the flux rope, and the EUV images reveal brightening episodes near the filament’s southeastern footpoint before each eruption. Therefore, these flux changes are likely the cause of the subsequent eruptions. These four homologous eruptions originate near adjacent feet of two large-scale loop systems connecting from that positive polarity part of the AR to two remote negative polarity regions, and result in large-scale consequences in the solar corona.

Simulations predict intermediate-mass black hole formation in globular clusters.

Intermediate-mass black holes (IMBHs) are those between 100 and 105 solar masses (M⨀); their formation process is debated. One potential origin is the growth of less massive black holes, by merging with stars and compact objects within globular clusters (GCs). However, previous simulations have indicated that this process only produces IMBHs <500 M⨀, before gravitational wave recoil ejects them from the GC. We perform star-by-star simulations of GC formation, finding that high-density star formation in a GC's parent giant molecular cloud can produce sufficient mergers of massive stars to overcome that mass threshold. We conclude that GCs can form with IMBHs ≳103M⨀, which is sufficiently massive to be retained within the GC even with the expected gravitational wave recoil.

Simulation and Analysis of a Near-Perfect Solar Absorber Based on SiO2-Ti Cascade Optical Cavity

The main development direction for current solar technology is to improve absorption efficiency and stability. To bridge this gap, we design in this paper a structure consisting of two multilayer disc stacks of different radii, one topped by a TiO2 disc and the other by a cascade disc stack composed of SiO2-Ti, for use in thermal emitters and solar absorbers. The innovation of our work is the exploitation of multiple Fabry–Perot resonances in SiO2-Ti cascade optical cavities to develop absorber bandwidths while investigating it in the field of thermal emission and many aspects affecting the efficiency of the absorber. The finite difference time domain method (FDTD) results show absorption averages as high as 96.68% with an absorption bandwidth of 2445 nm (A &gt; 90%) at 280 nm–3000 nm solar incidence and even higher weighted averages as high as 98.48% at 1.5 solar air mass (AM) illumination. In order to investigate the physical mechanisms of our designed absorber in a high absorption state, we analyzed the electric field distributions of its four absorption peaks and concluded that its high absorption is mainly caused by the coupling of multiple Fabry–Perot resonance modes in the cascaded optical cavity. While considering this high efficiency, we also investigated the effect of complex environments such as extreme high temperatures and changes in the angle of incidence of the absorber, and the results show that the thermal radiation efficiency of the emitter is 96.79% at an operating temperature of 1700 K, which is higher than its thermal radiation efficiency of 96.38% at an operating temperature of 1500 K, which is a perfect result. On the other hand, we conclude that the designed structure is independent of polarization, while the absorber still has 88.22% absorption at incidence angles of up to 60°, both in transverse electric (TE) and transverse magnetic (TM) modes. The results of this study can help improve the performance of future solar absorbers and expand their application areas.

Fitting the Crab Supernova with a Gamma-Ray Burst

Here, we reconsider the historical data, assuming a gamma-ray burst (GRB) as its source. A Supernova correlated with the GRB explains well the fading time observed by the ancient Chinese astronomers in the daytime and the nighttime, while the GRB power law explains the present X-rays and GeV emission of the Crab. On the grounds of a recent understanding of the first episode of binary-driven hypernova GRB (BDHN GRB) in terms of the collapse of a ten solar masses core, we propose the possible identification of the real Supernova event at an earlier time than Chinese chronicles. This work allows a new understanding of the significance of historical astronomical observations, including a fireball due to gamma-ray air shower observation and a plague of acute radiation syndrome, documented with several thousands of victims in the Eurasian area (Egypt, Iraq, and Syria).

New mechanism for primordial black hole formation from the QCD axion

We present a new mechanism for the primordial black hole (PBH) production within the QCD axion framework. We take the case where the Peccei-Quinn symmetry breaks during inflation, resulting in a NDW=1 string-wall network that reenters the horizon sufficiently late. Therefore, closed axion domain walls naturally arising in the network are sufficiently large to collapse into PBHs. Our numerical simulation shows that ∼0.3% of the total wall area is in the form of closed walls. In addition, the relic abundance of dark matter is dominantly accounted for by free axions from the collapse of open walls bounded by strings. In this framework, the abundance of PBH within dark matter is calculated to be ∼0.9%. This fraction remains unaffected by axion parameters or the reentering horizon temperature, as it is determined by the fixed proportion of closed walls in the network, governed by the principles of percolation theory. The resultant PBHs uniformly share the same mass, which spans from about 10−9 to 1 solar mass, corresponding to the classical QCD axion mass window 10−5–10−2 eV and the reentering horizon temperature 300−1 MeV. Intriguingly, PBHs in this mechanism can naturally account for the ultrashort-timescale gravitational microlensing events observed by the OGLE collaboration. Published by the American Physical Society 2024

Companion-launched jets at varying companion masses

ABSTRACT We conduct three-dimensional hydrodynamic simulations, and show that when a secondary star launches jets while interacting with a primary $0.88~\mathrm{ M}_{\rm \odot }$ giant star in a close orbit, the system can avoid entering the common envelope evolution (CEE). Instead of a fast in-spiral, the companion slowly enters the envelope as the jets facilitate the unbinding of the giant star envelope outside the companion orbit, in what is termed the grazing envelope evolution (GEE). The assumptions are that the secondary main-sequence star accretes mass via an accretion disc, and that the accretion disc launches the jets. We perform two sets of simulations with and without jets for different companion masses at the range of 0.1–0.9 M$_{\odot }$, maintaining a constant jet power in the former case of $1.5\times 10^{38}~{\rm ergs~s^{-1}}$. We examine which of the simulated systems undergo a GEE rather than a CEE and how efficiently the jets unbind the envelope. The results indicate that systems with companion masses at the range of 0.1–0.3 M$_{\odot }$ are more likely to result in a phase of GEE lasting 1–3 yr. With the smallest companion, a 0.1 solar mass star, the jets unbind 65 per cent of the envelope mass, while almost none of the envelope is unbound if jets are not present. The results of the simulations show that the GEE can serve as an alternative to the CEE, in forming short-period binaries that have compact objects and an ejected envelope.