Empirical Mass Research Articles

Extracting the Possible Intrinsic Relation between the Radiative Efficiency and Mass of QSOs: A Maximum Likelihood Method and its Application to the SDSS DR7 QSOs

Abstract Radiative efficiencies of QSOs and their distribution encode rich information on the evolution of both masses and spins of massive black holes (MBHs) across cosmic time. In this paper, we develop a maximum likelihood method to statistically extract the intrinsic relation between radiative efficiency (ϵ) and mass (M •) of QSOs from their distribution on the luminosity–(empirically estimated virial) mass plane. By using mock samples, we find that strong constraint can be put on the ϵ–M • relation at redshift z ≲ 0.4 from uniform QSO samples similar to those in the Sloan Digital Sky Survey (SDSS) and from QSO samples at z ∼ 0.6 (or ≲1.0) if the magnitude limit of the survey can be ∼1–2 (or 2–3) magnitude deeper. Applying this method to the SDSS DR7 QSOs with z ≲ 0.7, we find (or ) correlation for QSOs with the masses obtained according to the H β (or Mg ii) empirical mass estimator. These contradictory results may be due to the unknown systematic errors in the two mass estimators, preventing an accurate constraint on the ϵ–M • relation by using current available QSO samples. We find that both the estimates of MBH mass and Eddington ratio distribution functions can be affected by the ϵ– relation, suggesting that the determination of this relation is important for understanding the accretion and growth history of MBHs. In the future, the intrinsic ϵ–M • relation is expected to be strongly constrained by using QSO samples obtained from surveys deeper than the SDSS if the host galaxy contamination and systematic errors of the mass estimator(s) can be well modeled or removed.

Chemical profiling of Artemisia rupestris using HPLC-IT-TOF-MS

Artemisia rupestris is widely used as a folk medicine of Uygur and Kazak with blood and detoxification, deaccumulation stagnation, clearing heat digestion and other effects. Currently, the chemical profile of A. rupestris has not been disclosed, resulting in a great obstacle for the systematic clarification of the efficacy materials and the quality evaluations. In this paper, HPLC-IT-TOF-MS was deployed to characterize the chemical constituents in A. rupestris. As a result, a total of 124 compounds were detected in 75% ethanol extract of A. rupestris. By comparing with the reference compounds, seven chlorogenic acids, and four flavonoids as well as one sesquiterpenoid were definitely identified. Moreover, twenty sesquiterpenes, sixty-five flavonoids and twenty-three chlorogenic acids were preliminarily identified by matching MS/MS spectral information with literature data and applying those empirical mass spectrometric cracking rules. In current study, the chemical composition of A. rupestris was profiled in depth, and the findings are envisioned to provide a theoretical basis for the further studies of this well-known herbal medicine, such as efficacy material characterization and quality assessment.

Turbulent mass transfer model for the simulation of liquid-solid CFB risers and its verification

Rigorous simulation of mass transfer process in liquid-solid circulating fluidized bed (LSCFB) system is challenging not only due to the fluidization but also due to the existing turbulence. In this paper, the recently developed c2¯−εc approach is introduced to characterize the turbulent mass diffusion in LSCFB riser so that the empirical turbulent mass diffusivity are abandoned. As for describing the liquid-solid turbulent flow, the kl − εl − ks − εs − Θ formulations are adopted. With the proposed model, the distributions of species concentration and phase velocity as well as solids holdup can be predicted simultaneously. In this paper the integrated model is established and simulations are conducted for a riser involving an impulse tracer test process so that the proposed model can be validated. The turbulent Schmidt number is found to be varied but not a constant throughout the riser, which reveals that the use of constant turbulent Schmidt number for the traditional model is questionable.

Exploring the Mass-loss Histories of the Red Supergiants*

Abstract We report mid- to far-infrared imaging and photometry from 7 to 37 μm with SOFIA/FORCAST and 2 μm adaptive optics imaging with LBTI/LMIRCam of a large sample of red supergiants (RSGs) in four Galactic clusters: RSGC1, RSGC2 = Stephenson 2, RSGC3, and NGC 7419. The RSGs in these clusters cover their expected range in luminosity and initial mass from ≈9 to more than 25 M ⊙. The population includes examples of very late-type RSGs such as MY Cep, which may be near the end of the RSG stage, high-mass-losing maser sources, yellow hypergiants, and post-RSG candidates. Many of the stars and almost all of the most luminous have spectral energy distributions (SEDs) with extended infrared excess radiation at the longest wavelengths. To best model their SEDs, we use the DUSTY code with a variable radial density distribution function to estimate their mass-loss rates. Our –luminosity relation for 42 RSGs basically follows the classical de Jager curve, but at luminosities below 105 , we find a significant population of RSGs with below the de Jager relation. At luminosities above 105 L ⊙, there is a rapid transition to higher mass-loss rates that approximates and overlaps the de Jager curve. We recommend that instead of using a linear relation or single curve, the empirical –luminosity relation is better represented by a broad band. Interestingly, the transition to much higher at about 105 L ⊙ corresponds approximately to an initial mass of 18–20 M ⊙, which is close to the upper limit for RSGs becoming Type II supernovae.

Dependence of Mass–Dimensional Relationships on Median Mass Diameter

Retrievals of ice cloud properties require accurate estimates of ice particle mass. Empirical mass–dimensional (m–D) relationships in the form m = a D b are widely used and usually universally applied across the complete range of particle sizes. For the first time, the dependence of a and b coefficients in m–D relationships on median mass diameter (Dmm) is studied. Using combined cloud microphysical data collected during the Olympic Mountains Experiment and coincident observations from Airborne Precipitation Radar Third Generation, Dmm-dependent (a, b) coefficients are derived and represented as surfaces of equally plausible solutions determined by some tolerance in the chi-squared difference χ 2 that minimizes the difference between observed and retrieved radar reflectivity. Robust dependences of a and b on Dmm are shown with both parameters significantly decreasing with Dmm, leading to smaller effective densities for larger Dmm ranges. A universally applied constant m–D relationship overestimates the mass of large aggregates when Dmm is between 3–6 mm and temperatures are between −15–0 °C. Multiple m–D relations should be applied for different Dmm ranges in retrievals and simulations to account for the variability of particle sizes that are responsible for the mass and thus for the variability of particle shapes and densities.

The Physics of Possibility: Victorian Fiction, Science, and Gender

The Physics of Possibility: Victorian Fiction, Science, and Gender

Systematic study of Coulomb displacement energy based on the Coulomb energy empirical formula and mass model

In this study, starting from the nuclear binding energy, we studied the empirical formula of the Coulomb energy systematically. Beginning with the simplest empirical formula, we added the Coulomb exchange term, pairing correlation, and shell correction, to calculate the Coulomb energy more precisely. In addition, we investigated the Coulomb displacement energy of widely used mass models. The discrepancies between the calculation results and experimental data might be caused by the missing of the isospin breaking terms of strong interactions in theory. By investigating these discrepancies, we found that the results obtained by microscopic theories presented a distinctive systematical behavior. Thus, these theories can be improved by including isospin breaking terms. However, in the results obtained by phenomenological models, the systematical behavior is unclear. This occurs because it is difficult for the information of the microscopic nuclear structure to be absorbed into the parameters of phenomenological models.

An eclipsing substellar binary in a young triple system discovered by SPECULOOS

Mass, radius, and age are three of the most fundamental parameters for celestial objects, enabling studies of the evolution and internal physics of stars, brown dwarfs, and planets. Brown dwarfs are hydrogen-rich objects that are unable to sustain core fusion reactions but are supported from collapse by electron degeneracy pressure. As they age, brown dwarfs cool, reducing their radius and luminosity. Young exoplanets follow a similar behaviour. Brown dwarf evolutionary models are relied upon to infer the masses, radii and ages of these objects. Similar models are used to infer the mass and radius of directly imaged exoplanets. Unfortunately, only sparse empirical mass, radius and age measurements are currently available, and the models remain mostly unvalidated. Double-line eclipsing binaries provide the most direct route for the absolute determination of the masses and radii of stars. Here, we report the SPECULOOS discovery of 2M1510A, a nearby, eclipsing, double-line brown dwarf binary, with a widely-separated tertiary brown dwarf companion. We also find that the system is a member of the $45\pm5$ Myr-old moving group, Argus. The system's age matches those of currently known directly-imaged exoplanets. 2M1510A provides an opportunity to benchmark evolutionary models of brown dwarfs and young planets. We find that widely-used evolutionary models do reproduce the mass, radius and age of the binary components remarkably well, but overestimate the luminosity by up to 0.65 magnitudes, which could result in underestimated photometric masses for directly-imaged exoplanets and young field brown dwarfs by 20 to 35%.

Import, export, and recycling of dissolved nutrients in the Ogeechee River estuary (Georgia, USA)

We constructed an empirical mass balance model of nutrient fluxes in the Ogeechee River estuary (Georgia, USA) from eight surveys of seasonal estuarine nutrient concentrations during 2015 and 2016. The model results indicated a net removal of dissolved phosphorus and a net production of dissolved nitrogen (N) within the estuary over an annual cycle. During summer and autumn low flow periods, much of the dissolved N discharged to the ocean seems to be recycled into the estuary in the form of phytoplankton biomass. As a result, the outwelled N is not new nitrogen fueling coastal production but is nitrogen trapped within a recycling loop across the ocean–estuarine boundary. Higher flows in the fall and winter lead to direct discharge of nutrients with minimal recycling. A balanced N budget for the Ogeechee River estuary requires that estuarine N-fixation must exceed burial and denitrification losses within the estuary.

A Joint Mass–Radius–Period Distribution of Exoplanets

Abstract The radius–period distribution of exoplanets has been characterized by the Kepler survey, and the empirical mass–radius relation by the subset of Kepler planets with mass measurements. We combine the two in order to constrain the joint mass–radius–period distribution of Kepler transiting planets. We employ hierarchical Bayesian modeling and mixture models to formulate four models with varying complexity and fit these models to the data. We find that the most complex models that treat planets with significant gaseous envelopes, evaporated core planets, and intrinsically rocky planets as three separate populations are preferred by the data and provide the best fit to the observed distribution of Kepler planets. We use these models to calculate occurrence rates of planets in different regimes and to predict masses of Kepler planets, revealing the model-dependent nature of both. When using models with envelope mass loss to calculate η ⊕, we find nearly an order of magnitude drop, indicating that many Earth-like planets discovered with Kepler may be evaporated cores which do not extrapolate out to higher orbital periods. This work provides a framework for higher-dimensional studies of planet occurrence and for using mixture models to incorporate different theoretical populations of planets.

Methane hydrate formation in a water-continuous vertical flow loop with xanthan gum

Hydrate phase transition in drilling fluid is a non-ignorable problem for developing deep-water oil, natural gas and natural gas hydrate resources. Once gas hydrates form during drilling, it will increase the difficulty of wellbore pressure management and flow assurance, which enlarges the risk of hydrate blockage and causes serious property damage and casualties. Methane hydrate formation experiments are conducted in xanthan gum (XG) aqueous solution to mimic the drilling fluid flowing condition in a vertical flow loop. The experiments reveal that the hydrate formation process is a mass transfer process and experiences four different hydrate formation periods, because of the kinetics formation and slough of hydrate shells. The subcooling temperature has a weaker impact on the hydrate formation than the flow velocity and XG. The increase of flow velocity can enhance the hydrate formation rate in drilling fluid but the increase of XG concentration can inhibit the hydrate formation. The influence mechanisms of hydrate shell kinetic slough, flow velocity and XG concentration on hydrate formation are analyzed and discussed in detail. We built a mass-transfer hydrate formation model based on the mechanism of methane molecule diffusing from gas phase to liquid phase. The empirical overall mass transfer coefficient is introduced involving the influence of hydrate shell kinetic slough, flow velocity and XG concentration. In model validation, the maximum discrepancy of the developed model decreases from 146.85% to 11.03% after using the overall mass transfer coefficient.

An explicit expression of the empirical factor in a widely used phase change model

Many boiling problems have been simulated by a phase change model (Lee model) involving an empirical mass transfer intensity factor. It is challenge to determine the value of this factor. An explicit expression of the mass transfer intensity factor is derived, and the accuracy of the expression is validated by comparing simulation results with theoretical solutions for two benchmark problems. The influences of various fluid properties (liquid phase density and thermal conductivity, latent heat, saturation temperature, vapor phase density and thermal conductivity) and mesh size on the mass transfer intensity factor are discussed. Results demonstrate that the mass transfer intensity factor depends on density and thermal conductivity of liquid phase, latent heat, saturation temperature and mesh size, but is independent of the density and thermal conductivity of vapor phase. Effects of vapor density and thermal conductivity on the phase interface movement are taken into account by the temperature of the interfacial cell. The expression reveals that a constant value of the mass transfer intensity factor throughout the computational domain is not reasonable, and which is the reason for divergence issue. In a specific computational cell, the value of the mass transfer intensity factor depends on the volume fraction of the liquid phase, and extremely large value of the factor should be consistent with extremely small volume fraction of the liquid phase.

Exploring the high-mass end of the stellar mass function of star-forming galaxies at cosmic noon

ABSTRACT We present the high-mass end of the galaxy stellar mass function using the largest sample to date (5352) of star-forming galaxies with M⋆ > 1011 M⊙ at cosmic noon, 1.5 < z < 3.5. This sample is uniformly selected across 17.2 deg2 (∼0.44 Gpc3 comoving volume from 1.5 < z < 3.5), mitigating the effects of cosmic variance and encompassing a wide range of environments. This area, a factor of 10 larger than previous studies, provides robust statistics at the high-mass end. Using multiwavelength data in the Spitzer/HETDEX Exploratory Large Area (SHELA) footprint, we find that the SHELA footprint star-forming galaxy stellar mass function is steeply declining at the high-mass end probing values as high as ∼10−4 Mpc3 dex−1 and as low as ∼5 × 10−8 Mpc3 dex−1 across a stellar mass range of log(M⋆/M⊙) ∼ 11–12. We compare our empirical star-forming galaxy stellar mass function at the high-mass end to three types of numerical models: hydrodynamical models from IllustrisTNG, abundance matching from the UniverseMachine, and three different semi-analytical models (SAMs; SAG, SAGE, GALACTICUS). At redshifts 1.5 < z < 3.5, we find that results from IllustrisTNG and abundance matching models agree within a factor of ∼2–10, however the three SAMs strongly underestimate (up to a factor of 1000) the number density of massive galaxies. We discuss the implications of these results for our understanding of galaxy evolution.

Experimental and modeling investigation of non-equilibrium condensate vaporization in porous systems: Effective determination of mass transfer coefficient

Condensate vaporization in porous media occurs in several processes such as remediation, absorption/adsorption in packed beds, and gas recovery. Most of modeling/simulation investigations on condensate recovery processes assume local equilibrium to model mass transfer rate of components involved in the inter-phase mass transfer phenomenon. This assumption does not seem realistic, since high fluid velocity and limited contact area may result in an appreciable deviation from the equilibrium condition. In this study, vaporization of liquid condensate components into the flowing gas stream is explored through experimental and modeling approaches. We take into account the non-equilibrium inter-phase mass transfer. A key parameter in the non-equilibrium mass transfer is the mass transfer coefficient. Lack of adequate laboratory data concerning the vaporization of condensate components into the gas phase motivated us to conduct a systematic experimental work. Taguchi design of experiment (DOE) is implemented to optimize the experiments in terms of number of runs and process conditions. To accurately estimate the mass transfer coefficient, the diffusion/dispersion and convection mass transfer mechanisms are incorporated in the modeling of condensate vaporization in porous systems for the first time. The statistical tests are also employed to assess the relative importance of diffusion/dispersion and convection mechanisms in the condensate vaporization process. The optimum levels of design factors are found using signal to noise ratio (SNR) plots generated through using the Taguchi DOE. According to the statistical analysis, the diffusion term has no considerable impact on the magnitude of the mass transfer coefficient. The experimental results also reveal that the highest relative significance/contribution (about 36%) belongs to the gas flow rate. The second place is given to the liquid type with 28.83% contribution. The gas type and mean grain size hold the third and fourth ranks with 11.8% and 10.61% contributions, respectively. The experimental results confirm non-equilibrium mass transfer over condensate vaporization event, particularly at high-velocity conditions. Combining the theoretical concepts and experimental data, new empirical mass transfer correlations are suggested in this study that can be incorporated in commercial software packages for obtaining the mass transfer coefficient with a high precision.

A multiobjective experimental based optimization to the CO2 capture process using hybrid solvents of MEA-MeOH and MEA-water

To achieve the reduction of total energy consumption of CO2 capture without the major drawbacks of conventional amine solvents, the superior performance of a blended physical-chemical solvent, MEA-MeOH, was experimentally compared with that of MEA aqueous absorbent in lab-scale absorption/desorption towers, equipped with stainless steel pall ring packings. Considering the typical industrial requirements, the main operating variables accounted for each solvent were the operating temperature (35–55 °C), amine concentration (15–30 wt%), gas flow rate (50–100 l/min), liquid flow rate (0.75–1.25 l/min), CO2 concentration in the inlet gas (5–15 mol %), and the reboiler heat duty (1.4–2.2 kW). Response surface methodology was applied to give a quadratic mathematical model for obtained empirical volumetric overall mass transfer coefficients (KGaV). Based on the drastic increase of the energy requirement for solvent regeneration, a multiobjective optimization framework has been made to achieve the maximum desirable values for the KGaV, and the absorption percentage (Φ) with the minimum energy consumption (Ω). It was suggested that under the optimum operating condition, adding methanol to an aqueous MEA solution, reduces the regeneration energy consumption by 12%, while augmenting the CO2 absorption percentage (Φ) by 9.1%.

Dynamical Masses for the Triple System HD 28363 in the Hyades Cluster

Abstract The star HD 28363 in the Hyades cluster has been known for over a century as a visual binary with a period of 40 yr. The secondary is, in turn, a single-lined spectroscopic binary with a 21 day period. Here we report extensive spectroscopic monitoring of this hierarchical triple system that reveals the spectral lines of the third star for the first time. Combined with astrometric information, this makes it possible to determine the dynamical masses of all three stars. Only six other binaries in the Hyades have had their individual component masses determined dynamically. We infer the properties of the system by combining our radial-velocity measurements with visual observations, lunar occultation measurements, and with proper motions from the Hipparcos and Gaia missions that provide a constraint on the astrometric acceleration. We derive a mass of for the visual primary, and 1.210 ± 0.021 and 0.781 ± 0.014 M ☉ for the other two stars. These measurements along with those for the other six systems establish an empirical mass–luminosity relation in the Hyades that is in broad agreement with current models of stellar evolution for the known age and chemical composition of the cluster.

WISE J072003.20-084651.2B is a Massive T Dwarf∗ †

Abstract We present individual dynamical masses for the nearby M9.5+T5.5 binary WISE J072003.20−084651.2AB, a.k.a. Scholz’s star. Combining high-precision Canada–France–Hawaii Telescope/WIRCam photocenter astrometry and Keck adaptive optics resolved imaging, we measure the first high-quality parallactic distance ( pc) and orbit ( yr period) for this system composed of a low-mass star and brown dwarf. We find a moderately eccentric orbit ( ), incompatible with previous work based on less data, and dynamical masses of 99 ± 6 and 66 ± 4 for the two components. The primary mass is marginally inconsistent (2.1σ) with the empirical mass–magnitude–metallicity relation and models of main-sequence stars. The relatively high mass of the cold ( K) brown dwarf companion indicates an age older than a few gigayears, in accord with age estimates for the primary star, and is consistent with our recent estimate of ≈70 for the stellar/substellar boundary among the field population. Our improved parallax and proper motion, as well as an orbit-corrected system velocity, improve the accuracy of the system’s close encounter with the solar system by an order of magnitude. WISE J0720−0846AB passed within 68.7 ± 2.0 kau of the Sun 80.5 ± 0.7 kyr ago, passing through the outer Oort cloud where comets can have stable orbits.

On the Schrödinger spectrum of a hydrogen atom with electrostatic Bopp–Landé–Thomas–Podolsky interaction between electron and proton

The Schrödinger spectrum of a hydrogen atom, modeled as a two-body system consisting of a point electron and a point proton, changes when the usual Coulomb interaction between point particles is replaced with an interaction which results from a modification of Maxwell’s law of the electromagnetic vacuum. Empirical spectral data thereby impose bounds on the theoretical parameters involved in such modified vacuum laws. In the present paper the vacuum law proposed, in the 1940s, by Bopp, Landé–Thomas, and Podolsky (BLTP) is scrutinized in such a manner. The BLTP theory hypothesizes the existence of an electromagnetic length scale of nature — the Bopp length [Formula: see text] —, to the effect that the electrostatic pair interaction deviates significantly from Coulomb’s law only for distances much shorter than [Formula: see text]. Rigorous lower and upper bounds are constructed for the Schrödinger energy levels of the hydrogen atom, [Formula: see text], for all [Formula: see text] and [Formula: see text]. The energy levels [Formula: see text], [Formula: see text], and [Formula: see text] are also computed numerically and plotted versus [Formula: see text]. It is found that the BLTP theory predicts a nonrelativistic correction to the splitting of the Lyman-[Formula: see text] line in addition to its well-known relativistic fine-structure splitting. Under the assumption that this splitting does not go away in a relativistic calculation, it is argued that present-day precision measurements of the Lyman-[Formula: see text] line suggest that [Formula: see text] must be smaller than [Formula: see text]. Finite proton size effects are found not to modify this conclusion. As a consequence, the electrostatic field energy of an elementary point charge, although finite in BLTP electrodynamics, is much larger than the empirical rest mass ([Formula: see text]) of an electron. If, as assumed in all “renormalized theories” of the electron, the empirical rest mass of a physical electron is the sum of its bare rest mass and its electrostatic field energy, then in BLTP electrodynamics the electron has to be assigned a negative bare rest mass.

Dynamical Masses for the Hyades Binary 80 Tauri

Abstract The empirical mass–luminosity relation in the Hyades cluster rests on dynamical mass determinations for five binary systems, of which one is eclipsing and the other four are visual or interferometric binaries. The last one was identified and first measured more than 20 yr ago. Here we present dynamical mass measurements for a new binary system in the cluster, 80 Tau, which is also a visual pair with a much longer orbital period of about 170 yr. Although we lack the radial-velocity information that has enabled the individual mass determinations in all of the previous binaries, we show that it is still possible to derive the component masses for 80 Tau using only astrometric observations. This is enabled by the accurate proper motion measurements from the Hipparcos and Gaia missions, which constrain the orbital acceleration in the plane of the sky. Separate proper motion values from Gaia for the primary and secondary provide a direct constraint on the mass ratio. Our mass measurements, and , are consistent with the mass–luminosity relation defined by the five previously known systems, which in turn is in good agreement with current models of stellar evolution.

The Nearby Very Low Mass Triple Star LHS 1070

Abstract The component masses and kinematic parameters of the triple star LHS 1070 are redetermined by using the three-body model. It is shown that the discrepancy between new observations and the two-body fitting results is due to the three-body effects, which justifies the necessity of using the three-body model. Numerical integration shows that the three-body system remains integrated and its hierarchical configuration remains unchanged since the formation of the components. This implies that the triple star may not be formed by a three-body encounter. Also, the possibility that the most massive component is itself a tightly bounded binary is excluded based on the redetermined dynamical mass. The improved dynamical masses of the three components are greatly helpful to constrain at the lower end of the stellar empirical mass–luminosity relation.