adsabs/SciX_UAT_keywords huggingface dataset:
Characteristic Scales of Magnetic Switchback Patches Near the Sun and Their Possible Association With Solar Supergranulation and Granulation

Parker Solar Probe (PSP) data recorded within a heliocentric radial distance of 0.3 au have revealed a magnetic field dominated by Alfvénic structures that undergo large local variations or even reversals of the radial magnetic field. They are called magnetic switchbacks, they are consistent with folds in magnetic field lines within a same magnetic sector and are associated with velocity spikes during an otherwise calmer background. They are thought to originate either in the low solar atmosphere through magnetic reconnection processes or result from the evolution of turbulence or velocity shears in the expanding solar wind. In this work, we investigate the temporal and spatial characteristic scales of magnetic switchback patches. We define switchbacks as a deviation from the nominal Parker spiral direction and detect them automatically for PSP encounters 1, 2, 4, and 5. We focus in particular on a 5.1 day interval dominated by switchbacks during E5. We perform a wavelet transform of the solid angle between the magnetic field and the Parker spiral and find periodic spatial modulations with two distinct wavelengths, respectively consistent with solar granulation and supergranulation scales. In addition we find that switchback occurrence and spectral properties seem to depend on the source region of the solar wind rather than on the radial distance of PSP. These results suggest that switchbacks are formed in the low corona and modulated by the solar surface convection pattern.

Keywords: solar wind; solar physics; wavelet analysis; supergranulation; solar granulation; solar magnetic fields
Impact of the Disk Thickness on X-Ray Reflection Spectroscopy Measurements

In a previous paper, we presented an extension of our reflection model relxill_nk to include the finite thickness of the accretion disk following the prescription in Taylor & Reynolds. In this paper, we apply our model to fit the 2013 simultaneous observations by the Nuclear Spectroscopic Telescope Array (NuSTAR) and XMM-Newton of the supermassive black hole in MCG-06-30-15 and the 2019 NuSTAR observation of the Galactic black hole in EXO 1846-031. The high-quality data of these spectra had previously led to precise black hole spin measurements and very stringent constraints on possible deviations from the Kerr metric. We find that the disk thickness does not change previous spin results found with a model employing an infinitesimally thin disk, which confirms the robustness of spin measurements in high radiative efficiency disks, where the impact of disk thickness is minimal. Similar analysis on lower accretion rate systems will be an important test for measuring the effect of disk thickness on black hole spin measurements.

Keywords: astrophysical black holes; kerr black holes; x-ray astronomy; accretion
On the Heating of the Slow Solar Wind by Imbalanced Alfvén-wave Turbulence from 0.06 to 1 au: Parker Solar Probe and Solar Orbiter Observations

In this work we analyze plasma and magnetic field data provided by the Parker Solar Probe and Solar Orbiter missions to investigate the radial evolution of the heating of Alfvénic slow wind by imbalanced Alfvén-wave (AW) turbulent fluctuations from 0.06 to 1 au. in our analysis we focus on slow solar-wind intervals with highly imbalanced and incompressible turbulence (i.e., magnetic compressibility C B = δ B/B ≤ 0.25, plasma compressibility C n = δ n/n ≤ 0.25, and normalized cross helicity σ c ≥ 0.65). First, we estimate the AW turbulent dissipation rate from the wave energy equation and find that the radial profile trend is similar to the proton heating rate. Second, we find that the scaling of the empirical AW turbulent dissipation rate Q W obtained from the wave energy equation matches the scaling from the phenomenological AW turbulent dissipation rate Q CH09 (with Q CH09 ≃ 1.55Q W ) derived by Chandran & Hollweg based on the model of reflection-driven turbulence. Our results suggest that, as in the fast solar wind, AW turbulence plays a major role in the ion heating that occurs in incompressible slow-wind streams.

Keywords: slow solar wind; interplanetary turbulence; alfven waves
Image-based Classification of Variable Stars: First Results from Optical Gravitational Lensing Experiment Data

Recently, machine learning methods have presented a viable solution for the automated classification of image-based data in various research fields and business applications. Scientists require a fast and reliable solution in order to handle increasingly large amounts of astronomical data. However, so far astronomers have been mainly classifying variable starlight curves based on various pre-computed statistics and light curve parameters. In this work we use an image-based Convolutional Neural Network to classify the different types of variable stars. We use images of phase-folded light curves from the Optical Gravitational Lensing Experiment (OGLE)-III survey for training, validating, and testing, and use OGLE-IV survey as an independent data set for testing. After the training phase, our neural network was able to classify the different types between 80% and 99%, and 77%-98%, accuracy for OGLE-III and OGLE-IV, respectively.

Keywords: rr lyrae variable stars; classification; light curve classification; astronomy data analysis; type ii cepheid variable stars; anomalous cepheid variable stars; delta scuti variable stars; eclipsing binary stars; periodic variable stars; convolutional neural networks; sky surveys
The Impacts of Modeling Choices on the Inference of Circumgalactic Medium Properties from Sunyaev-Zeldovich Observations

As the signal-to-noise of Sunyaev-Zeldovich (SZ) cross-correlation measurements of galaxies improves our ability to infer properties about the circumgalactic medium (CGM), we will transition from being limited by statistical uncertainties to systematic uncertainties. Using thermodynamic profiles of the CGM created from the IllustrisTNG (The Next Generation) simulations we investigate the importance of specific choices in modeling the galaxy sample. These choices include different sample selections in the simulation (stellar versus halo mass, color selections) and different fitting models (matching by the shape of the mass distribution, inclusion of a two-halo term). We forward model a mock galaxy sample into projected SZ observable profiles and fit these profiles to a generalized Navarro-Frenk-White profile using forecasted errors of the upcoming Simons Observatory experiment. We test the number of free parameters in the fits and show that this is another modeling choice that yields different results. Finally, we show how different fitting models can reproduce parameters of a fiducial profile, and show that the addition of a two-halo term and matching by the mass distribution of the sample are extremely important modeling choices to consider.

Keywords: circumgalactic medium; sunyaev-zeldovich effect
The Initial Conditions of Clustered Core Collapse: Multiwavelength Analysis of Oph A SM1N and N6 at 100 au Resolution

We present new Atacama Large Millimeter/submillimeter Array (ALMA) continuum and NH2D, N2D+, and H2D+ line emission at matched, ∼100 au resolution toward the dense star-forming cores SM1N and N6 within the Ophiuchus molecular cloud. We determine the density and temperature structure of SM1N based on radiative transfer modeling and simulated observations of the multiwavelength continuum emission at 0.8, 2, and 3 mm. We show that SM1N is best fit by either a broken power-law or Plummer-like density profile with high central densities (n ∼ 108 cm‑3), and an inner transition radius of only ∼80–300 au. The free-fall time of the inner region is only a few ×103 yr. The continuum modeling rules out the presence of an embedded first hydrostatic core (FHSC) or protostar. SM1N is therefore a dynamically unstable but still starless core. We find that NH2D is likely depleted at high densities within SM1N. The nonthermal velocity dispersions increase from NH2D to N2H+ and H2D+, possibly tracing increasing (but still subsonic) infall speeds at higher densities as predicted by some models of starless core contraction. Toward N6, we confirm the previous ALMA detection of a faint, embedded point source (N6-mm) in 0.8 mm continuum emission. NH2D and N2D+ avoid N6-mm within ∼100 au, while H2D+ is not strongly detected toward N6. The distribution of these tracers is consistent with heating by a young, warm object. N6-mm thus remains one of the best candidate FHSCs detected so far, although its observed (sub)millimeter luminosity remains below predictions for FHSCs.

Keywords: star formation; astrochemistry; chemical abundances; protostars; young stellar objects
Bug Found in Gaia query_object Functions of Astroquery's Python Package

This research note addresses a bug in the Gaia functionality of the astroquery Python package. The bug, which results in sources in the Gaia catalog not being returned, affects the Gaia.query_object() and Gaia.query_object_async() functions. These rely on the deprecated ADQL BOX function if width or height are specified. These functions are used in published research and as such the bug could affect peer-reviewed results. We advise any researchers using these functions to instead use the Gaia.cone_search() counterparts to these functions or the Gaia.launch_job() functions. The Gaia helpdesk have been contacted and have confirmed the behavior and may update the astroquery documentation in the coming months.

Keywords: astronomy software; software documentation; gaia
Unveiling the Interplanetary Solar Radio Bursts of the 2024 Mother's Day Solar Storm

We report on a comprehensive study of interplanetary type III radio bursts linked to X-class solar flares from NOAA active region 13664, which instigated the intense 2024 Mother's Day solar storm, marked by a geomagnetic storm of ‑412 nT, the strongest in over two decades. Utilizing novel localization techniques with direction-finding data from STEREO-A, we identify an average eastward drift of 13.°42 ± 11.°63 in radio source locations relative to GOES observations. Our analysis reveals a significant correlation between solar flare intensity and longitude (Kendall's tau = 0.535) and a strong correlation between radio flux at 1 MHz and GOES 1–8 Å soft X-ray flux (Kendall's tau = 0.648). The timing analysis shows that peak soft X-ray fluxes typically follow electron beam liftoff by 3.24 ± 4.42 minutes. These insights into solar radio burst propagation and localization enhance our understanding of solar–terrestrial interactions and improve space weather forecasting capabilities.

Keywords: radio astronomy; radio bursts
Distorted-toroidal Flux Rope Model for Heliospheric Flux Ropes

The 3D characterization of magnetic flux ropes observed in the heliosphere has been a challenging task for decades. This is mainly due to the limitations on inferring the 3D global topology and physical properties from the 1D time series from any spacecraft. To advance our understanding of magnetic flux ropes whose configuration departs from the typical stiff geometries, here we present an analytical solution for a 3D flux rope model with an arbitrary cross section and a toroidal global shape. This constitutes the next level of complexity following the elliptic-cylindrical (EC) geometry. The mathematical framework was established by Nieves-Chinchilla et al. with the EC flux rope model, which describes a magnetic topology with an elliptical cross section as a first approach to changes in the cross section. In the distorted-toroidal flux rope model, the cross section is described by a general function. The model is completely described by a nonorthogonal geometry and the Maxwell equations can be consistently solved to obtain the magnetic field and relevant physical quantities. As a proof of concept, this model is generalized in terms of the radial dependence of current density components. The last part of this paper is dedicated to a specific function, $F(\varphi )=\delta (1-\lambda \cos \varphi )$ , to illustrate possibilities of the model. This model paves the way toward the investigation of complex distortions of magnetic structures in the solar wind. Future investigations will explore these distortions in depth by analyzing specific events; studying implications for physical quantities, such as magnetic fluxes, helicity, or energy; and evaluating the force balance with the ambient solar wind that allows such distortions.

Keywords: solar wind; solar coronal mass ejections; solar evolution
The [S II] Spectral Images of the Planetary Nebula NGC 7009. II. Major Axis

We derived position-velocity density distribution diagrams along the major (PA = 77°) axis of the elliptical planetary nebula NGC 7009 with the Keck HIRES [S II] 6716/6731 Å doublet spectral images. The average densities of the main shell and knots of NGC 7009 derived from the [S II] 6716/6731 Å fluxes integrated over the line of sight indicate a density range of N e = 103.4 to 103.9 cm-3, while the local densities from the volume fraction resolved in radial velocities along the line of sight show a considerably large range of about 102.8-104.7 cm-3. The derived projection angle of the major axis of the main shell is ψ ~ 18.3° (±2°). Assuming that the main shell is an ellipsoidal shell with a ≃ 16″ and b ≃ 6″, we found the range of the expansion velocity, radius, and latitude of four knots and a hot bubble. The four knots at points in symmetrical positions are roughly aligned with the same axis of expansion of latitudes ϕ ~ ±34.5° (±0.6°): one pair expands at about 35 km s-1 close to the main ellipsoidal shell, and the other expands rapidly at about 60 km s-1 at a distance of r ~ 16″. In the latitude range ϕ = 65°-75°, the hot bubble of a relatively large structure expands rapidly with a velocity of 130-150 km s-1. The four knots and hot bubble points, which expand faster than the main shell, appear to have been formed by two to three eruptions at a different epoch from the primary structure formation.

Keywords: planetary nebulae; h ii regions; interstellar medium; post-asymptotic giant branch
Alert Classification for the ALeRCE Broker System: The Anomaly Detector

Astronomical broker systems, such as Automatic Learning for the Rapid Classification of Events (ALeRCE), are currently analyzing hundreds of thousands of alerts per night, opening up an opportunity to automatically detect anomalous unknown sources. In this work, we present the ALeRCE anomaly detector, composed of three outlier detection algorithms that aim to find transient, periodic, and stochastic anomalous sources within the Zwicky Transient Facility data stream. Our experimental framework consists of cross-validating six anomaly detection algorithms for each of these three classes using the ALeRCE light-curve features. Following the ALeRCE taxonomy, we consider four transient subclasses, five stochastic subclasses, and six periodic subclasses. We evaluate each algorithm by considering each subclass as the anomaly class. For transient and periodic sources the best performance is obtained by a modified version of the deep support vector data description neural network, while for stochastic sources the best results are obtained by calculating the reconstruction error of an autoencoder neural network. Including a visual inspection step for the 10 most promising candidates for each of the 15 ALeRCE subclasses, we detect 31 bogus candidates (i.e., those with photometry or processing issues) and seven potential astrophysical outliers that require follow-up observations for further analysis. 16 16 The code and the data needed to reproduce our results are publicly available at https://github.com/mperezcarrasco/AnomalyALeRCE.

Keywords: astronomy data analysis; surveys; interdisciplinary astronomy
Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution

An αΩ dynamo, combining shear and cyclonic convection in the tachocline, is believed to generate the solar cycle. However, this model cannot explain cycles in fast rotators (with minimal shear) or in fully convective stars (no tachocline); an analysis of these stars could therefore provide key insights into how these cycles work. We reexamine ASAS data for 15 M dwarfs, 11 of which are presumed fully convective; the addition of newer ASAS-SN data confirms cycles in roughly 12 of them, while presenting new or revised rotation periods for 5 stars. The amplitudes and periods of these cycles follow ${A}_{\mathrm{cyc}}\propto {P}_{\mathrm{cyc}}^{0.94\pm 0.11}$ , with P cyc/P rot ∝ Ro -1.02±0.06 (where Ro is the Rossby number), very similar to P cyc/P rot ∝ Ro -0.81±0.17 that we find for 40 previously studied FGK stars, although P cyc/P rot and α are a factor of ~20 smaller in the M stars. The very different P cyc/P rot-Ro relation seen here compared to previous work suggests that two types of dynamo, with opposite Ro dependences, operate in cool stars. Initially, a (likely α 2 or α 2Ω) dynamo operates throughout the convective zone in mid- to late-M and fast-rotating FGK stars, but once magnetic breaking decouples the core and convective envelope, a tachocline αΩ dynamo begins and eventually dominates in older FGK stars. A change in α in the tachocline dynamo generates the fundamentally different P cyc/P rot-Ro relation.

Keywords: m dwarf stars; stellar activity; stellar magnetic fields; stellar rotation
Estimating the Jet Power of Mrk 231 during the 2017-2018 Flare

Long-term 17.6 GHz radio monitoring of the broad absorption-line quasar, Mrk 231, detected a strong flare in late 2017. This triggered four epochs of Very Long Baseline Array (VLBA) observations from 8.4 to 43 GHz over a 10 week period as well as an X-ray observation with NuSTAR. This was the third campaign of VLBA monitoring that we have obtained. The 43 GHz VLBA was degraded in all epochs, with only 7 of 10 antennas available in three epochs and 8 in the first epoch. However, useful results were obtained due to a fortuitous capturing of a complete, short 100 mJy flare at 17.6 GHz, both growth and decay. This provided useful constraints on the physical model of the ejected plasma that were not available in previous campaigns. We consider four classes of models: discrete ejections (both protonic and positronic) and jetted (protonic and positronic). The most viable model is a "dissipative bright knot" in a faint background leptonic jet with an energy flux ∼1043 erg s-1. Inverse Compton scattering calculations (based on these models) in the ambient quasar photon field explains the lack of a detectable increase in X-ray luminosity measured by NuSTAR. We show that the core (the bright knot) moves toward a nearby secondary at ≈0.97c. The background jet is much fainter. Evidently, the high-frequency VLBA core does not represent the point of origin of blazar jets, in general, and optical depth "core shift" estimates of jet points of origin can be misleading.

Keywords: quasars; radio loud quasars; radio quiet quasars; black hole physics; galaxy accretion disks
The Bright Rim Prominences according to 2.5D Radiative Transfer

Solar prominences observed close to the limb commonly include a bright feature that, from the perspective of the observer, runs along the interface between itself and the underlying chromosphere. Despite several idealized models being proposed to explain the underlying physics, a more general approach remains outstanding. In this manuscript we demonstrate as a proof of concept the first steps in applying the Lightweaver radiative transfer framework's 2.5D extension to a "toy" model prominence + VAL3C chromosphere, inspired by recent 1.5D experiments that demonstrated a significant radiative chromosphere–prominence interaction. We find the radiative connection to be significant enough to enhance both the electron number density within the chromosphere, as well as its emergent intensity across a range of spectral lines in the vicinity of the filament absorption signature. Inclining the viewing angle from the vertical, we find these enhancements to become increasingly asymmetric and merge with a larger secondary enhancement sourced directly from the prominence underside. In wavelength, the enhancements are then found to be the largest in both magnitude and horizontal extent for the spectral line cores, decreasing into the line wings. Similar behavior is found within new Chinese Hα Solar Explorer/Hα Imaging Spectrograph observations, opening the door for subsequent statistical confirmations of the theoretical basis we develop here.

Keywords: solar prominences; solar filaments; radiative transfer; solar chromosphere
Merger Effects on the Spin and Shape Alignments of Galaxy Stellar, Cold Gas, Hot Gas, and Dark Matter Components

We present a numerical evidence supporting the scenario that the peculiar alignments of the galaxy stellar spins with the major principal axes of the local tidal tensors are produced during the quiescent evolution period when the galaxies experience no recent merger events. Analyzing the merger tree from the TNG300-1 simulation of the IllustrisTNG project, we find the latest merger epochs, a(z m ), of the galaxies, and create four a(z m )-selected samples that are controlled to share the identical mass and density distributions. For each sample, we determine the spin and shape vectors of the galaxy stellar, cold and hot gas, and dark matter components separately, and compute the average strengths of their alignments with the principal directions of the local tidal fields as well as their mutual alignment tendencies. It is found that the stellar (cold gas) spin axes of the galaxies whose latest merger events occur at earlier epochs are more strongly aligned (weakly antialigned) with the major principal axes of the tidal fields. It is also shown that, although the mass-dependent transition of the galaxy DM spins have little connection with the merger events, the morphologies, spin-shape, and shape-shear alignment strengths of the four components of the galaxies sensitively depend on a(z m ). Noting that the stellar components of the galaxies that undergo long quiescent evolution have distinctively oblate shapes and very strong spin-shape alignments, we suggest that the local tidal field might be traced by using the stellar shapes of galaxies without signatures of mergers as a proxy of their stellar spins.

Keywords: large-scale structure of the universe; galaxy evolution
Solar-cycle-related Changes in the Helium Ionization Zones of the Sun

Helioseismic data for solar cycles 23 and 24 have shown unequivocally that solar dynamics changes with solar activity. Changes in solar structure have been more difficult to detect. Basu & Mandel had claimed that the then-available data revealed changes in the He II ionization zone of the Sun. The amount of change, however, indicated the need for larger than expected changes in the magnetic fields. Now that helioseismic data spanning two solar cycles are available, we have redone the analysis using improved fitting techniques. We find that there is indeed a change in the region around the He II ionization zone that is correlated with activity. Because the data sets now cover two solar cycles, the time variation is easily discernible.

Keywords: helioseismology; solar cycle; solar interior; solar oscillations; solar physics; solar activity