adsabs/SciX_UAT_keywords huggingface dataset:
Evolution of Kinetic and Magnetic Energy in a Large Magnetic Prandtl Number System

Many regions of the universe are in a state of hot, magnetized, and ionized X-ray emitting plasmas. We numerically simulated the energy spectrum of this highly viscous and conductive system. Without magnetic field, the fluctuating plasma motion decays in a relatively large viscous scale l ν (~1/k ν ). However, the magnetic field extends the viscous scale to the magnetic diffusivity one l η (~1/k η ) yielding a unique energy spectrum. Numerical simulation shows that kinetic and magnetic energy spectrum are E V ~ k -3.7 and E M ~ k -0.85 in the extended viscous scale regime. To explain this extraordinary power law, we set up two simultaneous differential equations for E V and E M and solved them using Eddy Damped Quasi Normal Markovianized approximation. Focusing on the most dominant terms, we analytically derived the spectrum relation ${E}_{M}^{2}\sim {k}^{2}{E}_{V}$ consistent with the simulation data. We also simulated the same system with helical energy. The inversely cascaded magnetic energy makes the spectrum steeper. This inverse energy transfer, in addition to the external magnetic field and instabilities, provides us a clue to the diversified spectra characterized by E V ~ k -3.8 - k -3.07 and E M ~ k -2.17 - k -0.27 with large magnetic Prandtl number.

Keywords: magnetohydrodynamics
The Open Cluster Chemical Abundances and Mapping Survey. IV. Abundances for 128 Open Clusters Using SDSS/APOGEE DR16

The Open Cluster Chemical Abundances and Mapping (OCCAM) survey aims to constrain key Galactic dynamical and chemical evolution parameters by the construction of a large, comprehensive, uniform, infrared-based spectroscopic data set of hundreds of open clusters. This fourth contribution from the OCCAM survey presents analysis using Sloan Digital Sky Survey/APOGEE DR16 of a sample of 128 open clusters, 71 of which we designate to be "high quality" based on the appearance of their color-magnitude diagram. We find the APOGEE DR16 derived [Fe/H] abundances to be in good agreement with previous high-resolution spectroscopic open cluster abundance studies. Using the high-quality sample, we measure Galactic abundance gradients in 16 elements, and find evolution of some of the [X/Fe] gradients as a function of age. We find an overall Galactic [Fe/H] versus RGC gradient of -0.068 ± 0.001 dex kpc-1 over the range of 6 < RGC < 13.9 kpc; however, we note that this result is sensitive to the distance catalog used, varying as much as 15%. We formally derive the location of a break in the [Fe/H] abundance gradient as a free parameter in the gradient fit for the first time. We also measure significant Galactic gradients in O, Mg, S, Ca, Mn, Cr, Cu, Na, Al, and K, some of which are measured for the first time. Our large sample allows us to examine four well-populated age bins in order to explore the time evolution of gradients for a large number of elements and comment on possible implications for Galactic chemical evolution and radial migration.

Keywords: open star clusters; galactic abundances; milky way evolution; chemical abundances
Limits on Protoplanet Growth by Accretion of Small Solids

This paper identifies constraints on the growth of a small planetary core (0.3 M⊕) that accretes millimeter-sized pebbles from a gaseous disk. We construct time-dependent spherical envelope models that capture physical processes that are not included in existing global hydrodynamic simulations, including particle size evolution, dust transport, and realistic gas equations of state. We assume a low enough disk density that pebbles are marginally coupled to the gas and are trapped efficiently near the core Bondi radius. Pebbles then drift rapidly enough to experience erosion by sandblasting, mutual collisions, and sublimation of water ice. We find that pebble fragmentation is more efficient than dust resticking. Therefore the high pebble accretion rate ${\dot{M}}_{p}$ needed to build a core of mass >M⊕ leads to a high envelope metallicity and grain opacity. Above ${\dot{M}}_{p}\sim 1\times {10}^{-7}\,{M}_{\oplus }$ yr-1, and without other luminosity sources, convective motions expand near the Bondi radius. The warm, dusty, and turbulent envelope buffers the inward drift of pebble debris: given a turbulent concentration factor fturb ≳ 1 near the lower convective boundary, the core growth rate is limited to 1 × 10-7 fturb M⊕ yr-1 and the e-folding time 3/fturb Myr. The remainder of the solid debris is expelled as highly processed silicates. Pebble ice never reaches the core, and the envelope contains comparable amounts of H2/He and metals. We interpret our results using simpler steady models and semianalytical estimates. Future global simulations incorporating the processes modeled here are needed to understand the influence of rotation and vertical disk structure.

Keywords: astrophysical dust processes; planetary atmospheres; radiative transfer; planet formation
Discovery of a 0.58M ⊙, 0.9 au Companion to HIP 42313 = δ Hya

In spite of them being the main progenitors of white dwarfs, the multiplicity of intermediate mass stars is relatively less explored when compared to solar-type and O-type stars. Here we report the discovery of a new companion to the nearby 2.43M ⊙ A1V star HIP 42313 = δ Hya with a K band flux ratio of 1.3% based on a VLTI/GRAVITY interferometric observation. This new 0.58M ⊙ companion at a projected separation 16.7 mas ↔ 0.90 au explains both the Hipparcos-GaiaDR2 as well as the GaiaDR2-GaiaDR3 proper motion changes of δ Hya. Together with the previously known 0.44M ⊙ companion at ρ = 2.″7 ↔ 147 au, this makes δ Hya a hierarchical triple system. *Based on observations collected at the European Southern Observatory, Chile, Program ID 110.241W.002.

Keywords: multiple stars; a stars; optical interferometry
Transport Equation of Kappa Distributions in the Heliosphere

In this paper, we develop the transport equation of kappa, the fundamental thermodynamic parameter that labels kappa distributions of particle velocities. Using the recently developed concept of entropy defect, we are able to formulate the transport equation of kappa as a function of a general, positive or negative, rate of entropy change. Then, we derive the particular case of exchanging plasma ions with low-dimensionality, newly born pickup protons, which interact and decrease the entropy of the flow of otherwise kappa-distributed plasma protons. Finally, we apply the transport equation of kappa to the solar wind plasma protons, which leads to the radial profile of kappa values, as well as the evolution of the kappa distributions through the heliosphere. The results show that the solar wind kappa decreases with increasing heliocentric distance, corresponding to plasmas residing in stationary states far from classical thermal equilibrium. Moreover, in the outer heliosphere and the heliosheath, kappa reaches its lowest values and is spread across the far-equilibrium region of 1.5 < κ < 2.5, which coincides with independent observations provided by NASA's Interstellar Boundary Explorer mission.

Keywords: space plasmas; heliosphere; heliosheath; solar wind; pickup ions
Impact of Heavy Ions on the Structure of Current Sheets in the Gravity Field of Exoplanets and Stars

Boundary current sheets (CSs) can be formed in collisionless space plasmas in the environment of exoplanets and cold stars. Usually they represent curved surfaces carrying the electric current analogous to the well-known planetary ionospheres, magnetopauses, or stellar coronas surrounding celestial bodies. At smaller local scales, some of them can be imagined as planar current layers of a finite scale located parallel to the surface of a celestial object and, correspondingly, perpendicular to the direction of the gravitational force. In some cases, this force crossed with magnetic field can influence the dynamics of charged particles in CSs and substantially change the structure of both the current layer and the magnetic field. We have generalized our prior model, taking into account a multi-ion plasma composition and a magnetic field configuration with a shear. It is shown that, due to the drift motion of plasma particles in the crossed gravitational and magnetic fields, the structure of CSs becomes more complex, accruing asymmetric and shifted profiles of the current and plasma densities that depend on dominating current carriers and the characteristics of the magnetic shear. We discuss possible applications of the results to the interpretation of observations of boundary layers in different space plasmas.

Keywords: exoplanets; gravitation; space plasmas; magnetic fields; jovian satellites
Ground Vibrational State SiO Emission in the VLA BAaDE Survey

Using a subsample of the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey of stellar SiO masers, we explore the prevalence and characteristics of 28SiO J = 1 - 0, v = 0 emission. We identify 90 detections of maser, thermal, or composite 28SiO J = 1 - 0, v = 0 emission out of approximately 13,000 candidate spectra from the National Science Foundation's Karl G. Jansky Very Large Array (VLA). We find that the detected sources are likely asymptotic giant branch stars belonging to a bright, foreground Milky Way stellar disk population. For the 32 sources showing thermal components, we extract values for outflow velocity by fitting thermal line profiles. We find a range of circumstellar envelope expansion velocities, and compare to previously recorded OH and CO expansion velocities. This preliminary survey is already the largest study of stellar ground vibrational state SiO masers to date, and will be expanded to include the entire VLA BAaDE data set when data reduction for the 18,988 target sources is completed.

Keywords: silicon monoxide masers; circumstellar masers; evolved stars
PHANGS-JWST First Results: Stellar-feedback-driven Excitation and Dissociation of Molecular Gas in the Starburst Ring of NGC 1365?

We compare embedded young massive star clusters (YMCs) to (sub-)millimeter line observations tracing the excitation and dissociation of molecular gas in the starburst ring of NGC 1365. This galaxy hosts one of the strongest nuclear starbursts and richest populations of YMCs within 20 Mpc. Here we combine near-/mid-IR PHANGS-JWST imaging with new Atacama Large Millimeter/submillimeter Array multi-J CO (1-0, 2-1 and 4-3) and [C I] (1-0) mapping, which we use to trace CO excitation via R 42 = I CO(4-3)/I CO(2-1) and R 21 = I CO(2-1)/I CO(1-0) and dissociation via R CICO = I [CI](1-0)/I CO(2-1) at 330 pc resolution. We find that the gas flowing into the starburst ring from northeast to southwest appears strongly affected by stellar feedback, showing decreased excitation (lower R 42) and increased signatures of dissociation (higher R CICO) in the downstream regions. There, radiative-transfer modeling suggests that the molecular gas density decreases and temperature and [CI/CO] abundance ratio increase. We compare R 42 and R CICO with local conditions across the regions and find that both correlate with near-IR 2 μm emission tracing the YMCs and with both polycyclic aromatic hydrocarbon (11.3 μm) and dust continuum (21 μm) emission. In general, R CICO exhibits ~0.1 dex tighter correlations than R 42, suggesting C I to be a more sensitive tracer of changing physical conditions in the NGC 1365 starburst than CO (4-3). Our results are consistent with a scenario where gas flows into the two arm regions along the bar, becomes condensed/shocked, forms YMCs, and then these YMCs heat and dissociate the gas.

Keywords: interstellar medium; molecular gas; young massive clusters; stellar feedback; starburst galaxies; interstellar line emission; barred spiral galaxies; co line emission; agn host galaxies; dust continuum emission
A Parametric Model to Reproduce the Background of the Insight-HXMT/HE Blind Detector

The estimation of instrumental background is the basis of essentially all data analysis on observations with Insight-HXMT. The current Insight-HXMT/HE background model made by Liao et al. depends on the data from the HE blind detector, i.e., using historical data to make a preliminary estimation of the background spectra and using the real-time data from the blind detector to make a further modification. In order to decouple the dependence of background method on the blind detector, a parametric physical model has been developed to rebuild the light curve and spectrum of the HE blind detector. In this parametric model, several physical processes between the space environment and the satellite are considered to rebuild the prompt and delayed background signals of the HE blind detector. With the genetic algorithm and Markov Chain Monte Carlo procedure, the model parameters are determined by fitting the data from the HE blind detector. For all 62 energy bands in the range 28-334 keV for an exposure of 10 ks, the average systematic error of the background energy spectrum is ~2.2% and the average total error of spectrum estimation ~3.4%. It is found that more accurate background can be attained using this model than using the data from the Insight-HXMT/HE blind detector for exposures of less than 2 ks. These results show that the background of the Insight-HXMT/HE blind detector can be reproduced reliably with this parametric model and this method can also be applied to the background estimation of other detectors in principle.

Keywords: x-ray telescopes; astronomy data modeling; space vehicle instruments; x-ray detectors
The Long-term Photometric Behavior of 39 Semiregular Variable Stars

Photometric measurements of the light and color variations of 39 semiregular variable stars over a 30 yr time interval have been used to explore the systematics of these variations. These results show the complex nature of the frequency compositions of the light curves of these stars. The frequencies present in the light curves tend to be harmonic in nature, suggesting that both modes of pulsation and shape effects may be involved and the nature of the variations indicates that stochastic excitation is involved.

Keywords: long period variable stars; semi-regular variable stars; stellar pulsations; pulsation modes; multi-periodic pulsation; photometry
Detectable Abundance of Cyanoacetylene (HC3N) Predicted on Reduced Nitrogen-rich Super-Earth Atmospheres

We predict that cyanoacetylene (HC3N) is produced photochemically in the atmosphere of GJ 1132 b in abundances detectable by the James Webb Space Telescope (JWST), assuming that the atmosphere is hydrogen dominated and rich in molecular nitrogen (N2), methane (CH4), and hydrogen cyanide (HCN), as described by Swain et al. First, we construct line lists and cross sections for HC3N. Then we apply these cross sections and the model atmosphere of Swain et al. to a radiative transfer model in order to simulate the transmission spectrum of GJ 1132 b as it would be seen by JWST, accounting for the uncertainty in the retrieved abundances. We predict that cyanoacetylene features at various wavelengths, with a clear lone feature at 4.5 μm, observable by JWST after one transit. This feature persists within the 1σ uncertainty of the retrieved abundances of HCN and CH4. The signal is detectable for stratospheric temperatures ≲600 K and moderate stratospheric mixing (106 cm2 s-1 ≲ Kzz ≲ 108 cm2 s-1). Our results also indicate that HC3N is an important source of opacity that future retrieval models should consider.

Keywords: extrasolar rocky planets; exoplanet atmospheres
The Impact of Powerful Jets on the Far-infrared Emission of an Extreme Radio Quasar at z ∼ 6

The interactions between radio jets and the interstellar medium play a defining role for the coevolution of central supermassive black holes and their host galaxies, but observational constraints on these feedback processes are still very limited at redshifts z > 2. We investigate the radio-loud quasar PSO J352.4034-15.3373 at z ∼ 6 at the edge of the Epoch of Reionization. This quasar is among the most powerful radio emitters and the first one with direct evidence of extended radio jets (∼1.6 kpc) at these high redshifts. We analyze NOrthern Extended Millimeter Array and Atacama Large Millimeter/submillimeter Array millimeter data targeting the CO (6-5) and [C II] far-infrared (FIR) emission lines, respectively, and the underlying continuum. The broad 440 ± 80 km s-1 and marginally resolved [C II] emission line yields a systemic redshift of z = 5.832 ± 0.001. Additionally, we report a strong 215 MHz radio continuum detection, 88 ± 7 mJy, using the Giant Metrewave Radio Telescope. This measurement significantly improves the constraints at the low-frequency end of the spectral energy distribution of this quasar. In contrast to what is typically observed in high-redshift radio-quiet quasars, we show that cold dust emission alone cannot reproduce the millimeter continuum measurements. This is evidence that the strong synchrotron emission from the quasar contributes substantially to the emission even at millimeter (FIR in the rest-frame) wavelengths. This quasar is an ideal system to probe the effects of radio jets during the formation of a massive galaxy within the first gigayear of the universe.

Keywords: radio loud quasars; quasars; extragalactic radio sources; observational astronomy; active galactic nuclei; agn host galaxies; high-redshift galaxies
Multiple Transitions in Vacuum Dark Energy and H 0 Tension

We study the effects of multiple transitions in the vacuum dark energy density on the H 0 tension problem. We consider a phenomenological model in which the vacuum energy density undergoes multiple transitions in the early as well as the late universe and compare the model's predictions using the three sets of data from the cosmic microwave background, baryonic acoustic oscillations, and supernovae. The transient dark energy can be either positive (dS-like) or negative (AdS-like). We conclude that a transient late-time AdS-type vacuum energy typically yields the higher value of H 0, which can alleviate the H 0 tension. In addition, to obtain a value of H 0 comparable to the value obtained from the local cosmological measurements the spectral index n s moves toward its Harrison-Zel'dovich scale-invariant value.

Keywords: dark energy; observational cosmology; hubble constant
Recovering the CMB Signal with Machine Learning

The cosmic microwave background (CMB), carrying the inhomogeneous information of the very early universe, is of great significance for understanding the origin and evolution of our universe. However, observational CMB maps contain serious foreground contaminations from several sources, such as Galactic synchrotron and thermal dust emissions. Here, we build a deep convolutional neural network (CNN) to recover the tiny CMB signal from various huge foreground contaminations. Focusing on CMB temperature fluctuations, we find that the CNN model can successfully recover the CMB temperature maps with high accuracy, and that the deviation of the recovered power spectrum C ℓ is smaller than the cosmic variance at ℓ > 10. We then apply this method to the current Planck observations, and find that the recovered CMB is quite consistent with that disclosed by the Planck Collaboration, which indicates that the CNN method can provide a promising approach to the component separation of CMB observations. Furthermore, we test the CNN method with simulated CMB polarization maps based on the CMB-S4 experiment. The result shows that both the EE and BB power spectra can be recovered with high accuracy. Therefore, this method will be helpful for the detection of primordial gravitational waves in current and future CMB experiments. The CNN is designed to analyze two-dimensional images, thus this method is not only able to process full-sky maps, but also partial-sky maps. Therefore, it can also be used for other similar experiments, such as radio surveys like the Square Kilometer Array.

Keywords: cosmic microwave background radiation; observational cosmology; convolutional neural networks
A Systematic Search for Short-period Close White Dwarf Binary Candidates Based on Gaia EDR3 Catalog and Zwicky Transient Facility Data

Galactic short-period close white dwarf binaries (CWDBs) are important objects for space-borne gravitational-wave (GW) detectors in the millihertz frequency bands. Due to the intrinsically low luminosity, only about 25 identified CWDBs are detectable by the Laser Interferometer Space Antenna (LISA), which are also known as verification binaries (VBs). The Gaia Early Data Release 3 (EDR3) provids a catalog containing a large number of CWDB candidates, which also includes parallax and photometry measurements. We crossmatch the Gaia EDR3 and Zwicky Transient Facility public data release 8, and apply period-finding algorithms to obtain a sample of periodic variables. The phase-folded light curves are inspected, and finally we obtain a binary sample containing 429 CWDB candidates. We further classify the samples into eclipsing binaries (including 58 HW Vir-type binaries, 65 EA-type binaries, 56 EB-type binaries, and 41 EW-type binaries) and ellipsoidal variations (209 ELL-type binaries). We discovered four ultrashort period binary candidates with unique light-curve shapes. We estimate the GW amplitude of all of our binary candidates, and calculate the corresponding signal-to-noise ratio (S/N) for TianQin and LISA. We find two (six) potential GW candidates with S/Ns greater than 5 in the nominal mission time of TianQin (LISA), which increases the total number of candidate VBs for TianQin (LISA) to 18 (31).

Keywords: white dwarf stars; close binary stars; catalogs; surveys
Multiobject Spectroscopy of Galaxy Clusters at z ∼ 0.95 in the Ultra Deep Survey Field with Different Star Formation Properties and Large-scale Environments

While galaxy clusters are dominated by quiescent galaxies in the local Universe, they show a wide range in quiescent galaxy fraction (QF) at higher redshifts. Here we present the discovery of two galaxy clusters at z ∼ 0.95 with contrasting QFs despite having similar masses (log (M 200/M ⊙) ∼ 14) and spectra and redshifts of 29 galaxies in these clusters and 76 galaxies in the surrounding area. The clusters are found in the Ultra Deep Survey field and confirmed through multiobject spectroscopic observation using the Inamori Magellan Areal Camera and Spectrograph on the Magellan telescope. The two clusters exhibit QFs of and , respectively. Analysis of large-scale structures (LSSs) surrounding these clusters finds that properties of these clusters are consistent with the anticorrelation trend between the QF and the extent of surrounding LSS, found in Lee et al., which can be interpreted as a result of the replenishment of young, star-forming galaxies keeping the QF low when galaxy clusters are accompanied by rich surrounding environments.

Keywords: high-redshift galaxy clusters; galaxy clusters; large-scale structure of the universe; galaxy evolution; high-redshift galaxies; cosmic web