adsabs/SciX_UAT_keywords huggingface dataset:
Failed Solar Eruption of a Multithermal Flux Rope

A magnetic flux rope (FR), hosting hot plasma, is thought to be central to the physics of coronal mass ejections. Such FRs are widely observed with passbands of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory that are sensitive to emission from the hot plasma around 10 MK. In contrast, observations of warmer (around 1 MK) counterparts of FRs are sparse. In this study, we report the failed eruption of a multithermal FR, hosting both hot and warm plasma. On 2015 May 1, a hot channel appeared in the AIA high-temperature passbands out of the southeastern solar limb to the south of a nearby flare, and then erupted outward. During the eruption, it rotated perpendicular to the erupting direction. The hot channel stopped erupting, and disappeared gradually, showing a failed eruption. During the hot channel eruption, a warm channel appeared sequentially in the AIA low-temperature passbands. It underwent a similar evolution, including the failed eruption, rotation, and disappearance, to the hot channel. A bright compression front is formed in front of the warm channel eruption in AIA low-temperature images. Under the hot and warm channel eruptions, a small flare occurred, upon which several current sheets, connecting the erupting channels and the underneath flare, formed in the AIA high-temperature passbands. Investigating the spatial and temporal relation between the hot and warm channels, we suggest that both channels twist together, constituting the same multithermal FR that has plasma with the high and low temperatures.

Keywords: solar filaments; solar ultraviolet emission; plasma physics; solar corona; solar flares; solar magnetic reconnection
The Nonuniformity of Poleward Flux Transport on the Solar Surface: A Statistical Method Applied to Solar Cycles 21-24

The poleward migration of the active regions' magnetic flux on the solar surface plays an important role in the development of the large-scale field development, especially the polar-field reversal, which is a key process in the Babcock-Leighton-type solar dynamos. The poleward flux transport is nonuniform, centered around poleward surges as suggested by previous observations. The strong, long-lasting surges are related to activity complexes, and often result in violent polar-field reversal. However, the nonuniformity of poleward flux transport has not been evaluated quantitatively. We propose a statistical method to analyze the poleward flux transport during solar cycles 21-24 by considering the frequency distributions of the magnetic field at latitudes of poleward surges occurring during solar cycles. The nonuniformity is quantified as the kurtosis statistics representing the tailedness of the distributions. We test the method on results of surface flux transport simulations, and apply it to WSO, National Solar Observatory, MWO, and HMI data. We confirm that the poleward surges are of significance during solar cycles 21-24 in general. The kurtosis within a solar cycle is affected by different latitudes of the magnetic field and different data sources. The southern hemisphere of cycle 24 exhibits the largest kurtosis, agreeing with the super-surge concept from previous work. The significant nonuniformity of poleward flux transport originates from the nonrandomness of active regions, which favors the activity complexes as the origin of poleward surges.

Keywords: solar magnetic fields; solar surface; solar active regions
Molecules with ALMA at Planet-forming Scales (MAPS): A Circumplanetary Disk Candidate in Molecular-line Emission in the AS 209 Disk

We report the discovery of a circumplanetary disk (CPD) candidate embedded in the circumstellar disk of the T Tauri star AS 209 at a radial distance of about 200 au (on-sky separation of 1.″4 from the star at a position angle of 161°), isolated via 13CO J = 2-1 emission. This is the first instance of CPD detection via gaseous emission capable of tracing the overall CPD mass. The CPD is spatially unresolved with a 117 × 82 mas beam and manifests as a point source in 13CO, indicating that its diameter is ≲14 au. The CPD is embedded within an annular gap in the circumstellar disk previously identified using 12CO and near-infrared scattered-light observations and is associated with localized velocity perturbations in 12CO. The coincidence of these features suggests that they have a common origin: an embedded giant planet. We use the 13CO intensity to constrain the CPD gas temperature and mass. We find that the CPD temperature is ≳35 K, higher than the circumstellar disk temperature at the radial location of the CPD, 22 K, suggesting that heating sources localized to the CPD must be present. The CPD gas mass is ≳0.095 M Jup ≃ 30 M ⊕ adopting a standard 13CO abundance. From the nondetection of millimeter continuum emission at the location of the CPD (3σ flux density ≲26.4 μJy), we infer that the CPD dust mass is ≲0.027 M ⊕ ≃ 2.2 lunar masses, indicating a low dust-to-gas mass ratio of ≲9 × 10-4. We discuss the formation mechanism of the CPD-hosting giant planet on a wide orbit in the framework of gravitational instability and pebble accretion.

Keywords: protoplanetary disks; planet formation; radio interferometry; millimeter astronomy; submillimeter astronomy; exoplanet formation
The σHβ -based Dimensionless Accretion Rate and Its Connection with the Corona for AGNs

With respect to the Hβ FWHM (FWHMHβ ), the broad Hβ line dispersion (σ Hβ ) was preferred as a velocity tracer to calculate the single-epoch supermassive black hole mass (M BH) suggested by Yu et al. For a compiled sample of 311 broad-line active galactic nuclei (AGNs) with measured hard X-ray photon index (z < 0.7), σ Hβ and the optical Fe II relative strength (R Fe) are measured from their optical spectra, which are used to calculate σ Hβ -based virial M BH and dimensionless accretion rate ( $\dot{M}$ ). With respect to FWHMHβ , it is found that the mean value of σ Hβ -based M BH is on average larger by 0.26 dex and the mean value of σ Hβ -based $\dot{M}$ is on average smaller by 0.51 dex. It is found that there exists a nonlinear relationship between the Eddington ratio (L Bol/L Edd) and $\dot{M}$ , i.e., ${L}_{\mathrm{Bol}}/{L}_{\mathrm{Edd}}\propto {\dot{M}}^{0.56\pm 0.01}$ . This nonlinear relationship comes from the accretion efficiency η, which is smaller for AGNs with higher $\dot{M}$ . We find a strong bivariate correlation of the fraction of energy released in the corona F X with $\dot{M}$ and M BH, ${F}_{{\rm{X}}}\propto {\dot{M}}^{-0.57\pm 0.05}{M}_{\mathrm{BH}}^{-0.54\pm 0.06}$ . The flat slope of -0.57 ± 0.05 favors the shear stress tensor of the accretion disk being proportional to the geometric mean of gas pressure and total pressure. We find a strong bivariate relation of Γ with $\dot{M}$ and F X, ${\rm{\Gamma }}\propto {\dot{M}}^{-0.21\pm 0.02}{F}_{{\rm{X}}}^{0.02\pm 0.04}$ . The hard X-ray spectrum becomes softer with increasing F X, although the scatter is large.

Keywords: active galactic nuclei; supermassive black holes; emission line galaxies
Modeling the High-energy Ionizing Output from Simple Stellar and X-Ray Binary Populations

We present a methodology for modeling the joint ionizing impact due to a "simple X-ray population" (SXP) and its corresponding simple stellar population (SSP), where "simple" refers to a single age and metallicity population. We construct composite spectral energy distributions (SEDs) including contributions from ultraluminous X-ray sources and stars, with physically meaningful and consistent consideration of the relative contributions of each component as a function of instantaneous burst age and stellar metallicity. These composite SEDs are used as input for photoionization modeling with Cloudy, from which we produce a grid for the time- and metallicity-dependent nebular emission from these composite populations. We make the results from the photoionization simulations publicly available. We find that the addition of the SXP prolongs the high-energy ionizing output from the population-and correspondingly increases the intensity of nebular lines such as He II λ1640,4686, [Ne V] λ3426,14.3 μm, and [O IV] 25.9 μm by factors of at least two relative to models without an SXP spectral component. This effect is most pronounced for instantaneous bursts of star formation on timescales >10 Myr and at low metallicities (~0.1 Z ⊙), due to the imposed time- and metallicity-dependent behavior of the SXP relative to the SSP. We propose nebular emission line diagnostics accessible with JWST suitable for inferring the presence of a composite SXP + SSP, and we discuss how the ionization signatures compare to models for sources such as intermediate-mass black holes.

Keywords: emission line galaxies; ultraluminous x-ray sources; starburst galaxies; stellar populations; photoionization
An Additional Note to "A New Insight into the Linear Theory of Magnetoacoustic Waves in the Homogeneous Flux Tubes with an Abrupt Boundary"

This is to address the criticism expressed in the article (Goedbloed & Poedts 2024) referred to as GP[24] about the work (Yelagandula 2023) referred to as Y[23]. It will be shown that the dispersion relation obtained in Y[23] is indeed correct within the framework of the ZSER model discussed in Y[23] despite the correct criticism of GP[24] about the electrodynamic boundary condition.

Keywords: solar coronal loops
A Reader Friendly Formalism for the Circumstellar Material-supernova Ejecta Interaction Model

The interaction of a SN ejecta with a pre-existing circumstellar material (CSM) is one of the most promising energy sources for a variety of optical transients. Recently, a semi-analytic method developed by Chatzopoulos et al. (2012, hereafter CWV12) has been commonly used to describe the optical light curve behaviors under such a scenario. We find that the expressions for many key results in CWV12 are too complicated for readers to make order of magnitude estimation or parameter dependency judgement. Based on the same physical picture, here we independently re-derive all the formulae and re-establish a set of reader friendly formula expressions. Nevertheless, we point out and correct some minor errors or typos existing in CWV12.

Keywords: supernovae; light curves; circumstellar shells
An ALMA Survey of λ Orionis Disks: From Supernovae to Planet Formation

Protoplanetary disk surveys by the Atacama Large Millimeter/submillimeter Array (ALMA) are now probing a range of environmental conditions, from low-mass star-forming regions like Lupus to massive OB clusters like σ Orionis. Here we conduct an ALMA survey of protoplanetary disks in λ Orionis, an ∼5 Myr old OB cluster in Orion with dust mass sensitivities comparable to the surveys of nearby regions (∼0.4 M⊕). We assess how massive OB stars impact planet formation, in particular from the supernova that may have occurred ∼1 Myr ago in the core of λ Orionis; studying these effects is important, as most planetary systems, including our solar system, are likely born in cluster environments. We find that the effects of massive stars, in the form of presupernova feedback and/or a supernova itself, do not appear to significantly reduce the available planet-forming material otherwise expected at this evolved age. We also compare a lingering massive "outlier" disk in λ Orionis to similar systems in other evolved regions, hypothesizing that these outliers host companions in their inner disks that suppress disk dispersal to extend the lifetimes of their outer primordial disks. We conclude with numerous avenues for future work that highlight how λ Orionis still has much to teach us about perhaps one of the most common types of planet-forming environments in the Galaxy.

Keywords: protoplanetary disks; circumstellar disks; millimeter astronomy; planet formation; exoplanet formation; submillimeter astronomy; ob stars; supernovae; surveys
Magnetic Connectivity between the Light Bridge and Penumbra in a Sunspot

A light bridge is a prominent structure commonly observed within a sunspot. Its presence usually triggers a wealth of dynamics in a sunspot and has a lasting impact on sunspot evolution. However, the fundamental structure of light bridges is still not well understood. In this study, we used the high-resolution spectropolarimetry data obtained by the Solar Optical Telescope on board the Hinode satellite to analyze the magnetic and thermal structure of a light bridge at AR 12838. We also combined the high-cadence $1700\,\mathring{\rm A} $ channel data provided by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to study the dynamics on this bridge. We found a pair of blue and red Doppler shift patches at two ends of this bridge; this pattern appears to be the convective motion directed by the horizontal component of the magnetic field aligned with the spine of the bridge. Paired upward and downward motions imply that the light bridge could have a two-legged or undulating magnetic field. Significant 4 minute oscillations in the emission intensity of the $1700\,\mathring{\rm A} $ bandpass were detected at two ends, which overlapped the paired blue- and redshift patches. The oscillatory signals at the light bridge and the penumbra were highly correlated with each other. Although they are separated in space at the photosphere, the periodicity seems to have a common origin from underneath the sunspot. Therefore, we infer that the light bridge and penumbra could share a common magnetic source and become fragmented at the photosphere by magnetoconvection.

Keywords: sunspots; magnetohydrodynamics; sunspot flow; solar coronal waves; solar magnetic fields; solar magnetic reconnection
Magnetic Field Generation by an Inhomogeneous Return Current

A new generation mechanism of the magnetic field in an inhomogeneous collisionless plasma with a beam component is proposed. We show that even though the current and charge neutralities are initially satisfied, the current neutrality is eventually violated if there is an inhomogeneity, so that the magnetic field is generated. By conducting ab initio two-dimensional particle-in-cell simulations, we demonstrate that the magnetic field is generated as expected. The new generation mechanism of the magnetic field can play an important role in the current universe because cosmic rays can be regarded as the beam component in the astrophysical plasma. We propose that the first cosmic rays generate the magnetic field with a large scale at the redshift of z ≈ 20.

Keywords: cosmic magnetic fields theory; magnetic fields; galaxy magnetic fields; astrophysical magnetism; interstellar magnetic fields; cosmic rays; plasma astrophysics; plasma physics
The Impact of Inelastic Collisions with Hydrogen on NLTE Copper Abundances in Metal-poor Stars

We investigate the non-local thermodynamic equilibrium (non-LTE, hereafter NLTE) analysis for Cu I lines with the updated model atom that includes quantum-mechanical rate coefficients of Cu + H and Cu+ + H- inelastic collisions from the recent study of Belyaev et al. The influence of these data on NLTE abundance determinations has been performed for six metal-poor stars in a metallicity range of -2.59 dex ≤ [Fe/H] ≤ -0.95 dex. For Cu I lines, the application of accurate atomic data leads to a decrease in the departure from LTE and lower copper abundances compared to that obtained with Drawin's theoretical approximation. To verify our adopted copper atomic model, we also derived the LTE copper abundances of Cu II lines for the sample stars. A consistent copper abundance from the Cu I (NLTE) and Cu II (LTE) lines has been obtained, which indicates the reliability of our copper atomic model. It is noted that the [Cu/Fe] ratios increase with increasing metallicity when ~-2.0 dex < [Fe/H] < ~-1.0 dex, favoring a secondary (metallicity-dependent) copper production.

Keywords: stellar abundances; stellar physics; milky way evolution
Preliminary Target Selection for the DESI Luminous Red Galaxy (LRG) Sample

The DESI survey will observe more than 8 million candidate luminous red galaxies (LRGs) in the redshift range 0.3 < z < 1.0. Here we present a preliminary version of the DESI LRG target section developed using Legacy Surveys Data Release 8 g, r, z and W1 photometry. This selection yields a sample with a uniform surface density of ∼600 deg-2 and very low predicted stellar contamination and redshift failure rates. During DESI Survey Validation, updated versions of this selection will be tested and optimized.

Keywords: large-scale structure of the universe; observational cosmology; redshift surveys
Properties of Streamer Wave Events Observed during the STEREO Era

Transverse waves are sometimes observed in solar helmet streamers, typically after the passage of a coronal mass ejection (CME). The CME-driven shock wave moves the streamer sideways, and a decaying oscillation of the streamer is observed after the CME passage. Previous works generally reported observations of streamer oscillations taken from a single vantage point (typically the Solar and Heliospheric Observatory (SOHO) spacecraft). We conduct a data survey searching for streamer wave events observed by the COR2 coronagraphs on board the STEREO spacecraft. For the first time, we report observations of streamer wave events from multiple vantage points by using the COR2 instrument on both STEREO A and B, as well as the SOHO/LASCO C2+C3 coronagraphs. We investigate the properties of streamer waves by comparing the different events and performing a statistical analysis. Common observational features give us additional insight on the physical nature of streamer wave events. The most important conclusion is that there appears to be no relation between the speed of the CME and the phase speed of the resulting streamer wave, indicating that the streamer wave speed is determined by the physical properties of the streamer rather than the properties of the CME. This result makes streamer wave events excellent candidates for coronal seismology studies. From a comparison between the measured phase speeds and the phase speeds calculated from the measured periods and wavelengths, we could determine that the speed of the postshock solar wind flow in our streamers is around 300 km s-1.

Keywords: solar coronal streamers; solar corona; solar coronal waves
The Cool Circumgalactic Medium of Low-redshift Star-forming Galaxies. I. Empirical Model and Mean Properties

We present an analytic model for the cool, T ~ 104 K, circumgalactic medium (CGM), describing the gas distribution, and thermal and ionization states. Our model assumes (total) pressure equilibrium with the ambient warm/hot CGM, photoionization by the metagalactic radiation, and allows for nonthermal pressure support, parameterized by the ratio of thermal pressures, η = P hot,th/P cool,th. We apply the model to the COS-Halos measurements and find that a nominal model with η = 3, gas distribution out to r ≈ 0.6R vir, and M cool = 3 × 109 M ⊙, corresponding to a volume filling fraction of f V,cool ≈ 1%, reproduces the H I and low/intermediate metal ions (C II, C III, Si II, Si III, and Mg II) mean column densities. Variation of ±0.5 dex in η or M cool encompasses ~2/3 of the scatter between objects. Our nominal model underproduces the measured C IV and Si IV columns, and these can be reproduced with (i) a cool phase with M cool ~ 1010 M ⊙ and η ≈ 5, or (ii) cooling or mixing gas at intermediate temperatures, with M ~ 1.5 × 1010 M ⊙ and occupying ~1/2 of the total CGM volume. For cool gas with f V,cool ≈ 1%, we estimate an upper limit on the cloud sizes, R cl ≲ 0.5 kpc. Our results suggest that for the average galaxy CGM, the mass and nonthermal support in the cool phase are lower than previously estimated, and extreme scenarios are not necessary. We estimate the rates of cool gas depletion and replenishment, and find accretion onto the galaxy can be offset, allowing ${\dot{M}}_{\mathrm{cool}}\approx 0$ over long timescales.

Keywords: circumgalactic medium; galaxy structure; galaxy evolution; quasar absorption line spectroscopy; intergalactic medium; galaxy formation; interstellar medium; galactic and extragalactic astronomy; galaxy processes
Propagation of Alfvén Waves in the Expanding Solar Wind with the Fast-Slow Stream Interaction

We carry out two-dimensional magnetohydrodynamic simulations of an ensemble of Alfvénic fluctuations propagating in a structured, expanding solar wind including the presence of fast and slow solar wind streams. Using an appropriate expanding box model, the simulations incorporate the effects of fast-slow stream shear and compression and rarefaction self-consistently. We investigate the radial and longitudinal evolution of the cross helicity, the total and residual energies and the power spectra of outward and inward Alfvénic fluctuations. The stream interaction is found to strongly affect the radial evolution of Alfvénic turbulence. The total energy in the Alfvén waves is depleted within the velocity shear regions, accompanied by the decrease of the normalized cross helicity. The presence of stream compression facilitates this process. Residual energy fluctuates around zero due to the correlation and de-correlation between the inward/outward waves but no net growth or decrease of the residual energy is observed. The radial power spectra of the inward/outward Alfvén waves show significant longitudinal variations. Kolmogorov-like spectra are developed only inside the fast and slow streams and when both the compression and shear are present. On the other hand, the spectra along the longitudinal direction show clear Kolmogorov-like inertial ranges in all cases.

Keywords: solar wind; interplanetary turbulence; alfven waves; corotating streams
SpectAcLE: An Improved Method for Modeling Light Echo Spectra

Light echoes give us a unique perspective on the nature of supernovae and nonterminal stellar explosions. Spectroscopy of light echoes can reveal details on the kinematics of the ejecta, probe asymmetry, and reveal details of ejecta interaction with circumstellar matter, thus expanding our understanding of these transient events. However, the spectral features arise from a complex interplay between the source photons, the reflecting dust geometry, and the instrumental setup and observing conditions. In this work, we present an improved method for modeling these effects in light echo spectra, one that relaxes the simplifying assumption of a light-curve-weighted sum, and instead estimates the true relative contribution of each phase of a transient event to the observed spectrum. We discuss our logic, the gains we obtain over light echo analysis methods used in the past, and prospects for further improvements. Lastly, we show how the new method improves our analysis of echoes from Tycho's supernova (SN 1572) as an example.

Keywords: supernovae; reflection nebulae