Sazuna/UAT_keywords huggingface dataset:
Cleaning Our Hazy Lens: Exploring Trends in Transmission Spectra of Warm Exoplanets. Relatively little is understood about the atmospheric composition of temperate to warm exoplanets (equilibrium temperature T eq &lt; 1000 K), as many of them are found to have uncharacteristically flat transmission spectra. Their flattened spectra are likely due to atmospheric opacity sources such as planet-wide photochemical hazes and condensation clouds. We compile the transmission spectra of 25 warm exoplanets previously observed by the Hubble Space Telescope and quantify the haziness of each exoplanet using a normalized amplitude of the water absorption feature (A H). By examining the relationships between A H and various planetary and stellar forcing parameters, we endeavor to find correlations of haziness associated with planetary properties. We adopt new statistical correlation tests that are more suitable for the small, nonnormally distributed warm exoplanet sample. Our analysis shows that none of the parameters have a statistically significant correlation with A H (p ≤ 0.01) with the addition of new exoplanet data, including the previously identified linear trends between A H and T eq or the hydrogen-helium envelope mass fraction (f HHe). This suggests that haziness in warm exoplanets is not simply controlled by any single planetary/stellar parameter. Among all the parameters we investigated, planet gravity (g p), atmospheric scale height (H), planet density (ρ p), orbital eccentricity (e), and age of the star (t age) have tentative correlations with A H. Specifically, lower H, higher g p, ρ p, e, or t age may lead to clearer atmospheres. We still need more observations and laboratory experiments to fully understand the complex physics and chemistry involved in creating hazy warm exoplanets.

Keywords: Exoplanet atmospheric composition , Extrasolar gaseous planets, Exoplanet atmospheres
A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona. We present a comprehensive radiative magnetohydrodynamic simulation of the quiet Sun and large solar active regions. The 197 Mm wide simulation domain spans from 18(10) Mm beneath the photosphere to 113 Mm in the solar corona. Radiative transfer assuming local thermal equilibrium, optically thin radiative losses, and anisotropic conduction transport provide the necessary realism for synthesizing observables to compare with remote-sensing observations of the photosphere and corona. This model self-consistently reproduces observed features of the quiet Sun, emerging and developed active regions, and solar flares up to M class. Here, we report an overview of the first results. The surface magneto-convection yields an upward Poynting flux that is dissipated in the corona and heats the plasma to over 1 MK. The quiescent corona also presents ubiquitous propagating waves, jets, and bright points with sizes down to 2 Mm. Magnetic flux bundles emerge into the photosphere and give rise to strong and complex active regions with over 1023 Mx magnetic flux. The coronal free magnetic energy, which is approximately 18% of the total magnetic energy, accumulates to approximately 1033 erg. The coronal magnetic field is clearly non-force-free, as the Lorentz force needs to balance the pressure force and viscous stress as well as drive magnetic field evolution. The emission measure from ${\mathrm{log}}_{10}T=4.5$ to ${\mathrm{log}}_{10}T\gt 7$ provides a comprehensive view of the active region corona, such as coronal loops of various lengths and temperatures, mass circulation by evaporation and condensation, and eruptions from jets to large-scale mass ejections.

Keywords: Radiative magnetohydrodynamics, Solar magnetic flux emergence, Solar extreme ultraviolet emission, Solar active regions, Solar corona, Solar magnetic fields
Exponential Fluctuations in the Modes of Orthogonal Polarization in Pulsar Radio Emission. A statistical model for the polarization of pulsar radio emission is enhanced to account for the heavy modulation of the emission, the possible covariance of the Stokes parameters, and the observed asymmetries in the distributions of total intensity, polarization, and fractional polarization, by treating the intensities of the orthogonal polarization modes as exponential random variables. The model is used to derive theoretical distributions to compare with what is observed. The resulting distributions are unimodal and generally asymmetric. The unimodality arises from the model's fundamental assumption that the orthogonal modes are superposed. The asymmetry originates primarily from different fluctuations in mode intensities. The distributions of fractional polarization are truncated at the degree of linear and circular polarization intrinsic to the modes. A number of observable parameters that quantify the statistical properties of the emission and its polarization are derived and are shown to be functions only of the ratio of the modes' mean intensities, M, suggesting their spectra coevolve according to the frequency dependence of M. This particular implementation of the model requires the modes to fluctuate differently in order to replicate the observations. Given that a single underlying emission mechanism seems unlikely to selectively modulate the mode intensities, the different fluctuations are attributed either to different emission mechanisms for the modes or to mode-dependent propagation or scattering effects in the pulsar magnetosphere.

Keywords: Radio pulsars
The Location and Angle Distribution of Magnetic Reconnection in the Solar Corona. A major unresolved issue in solar physics is the nature of the reconnection events that may give rise to the extreme temperatures measured in the solar corona. In the nanoflare heating paradigm of coronal heating, localized reconnection converts magnetic energy into thermal energy, producing multithermal plasma in the corona. The properties of the corona produced by magnetic reconnection, however, depend on the details of the reconnection process. A significant challenge in understanding the details of reconnection in magnetohydrodynamic (MHD) models is that these models are frequently only able to tell us that reconnection has occurred, but there is significant difficulty in identifying precisely where and when it occurred. In order to properly understand the consequences of reconnection in MHD models, it is crucial to identify reconnecting field lines and where along the field lines reconnection occurs. In this work, we analyze a fully 3D MHD simulation of a realistic sunspot topology, driven by photospheric motions, and we present a model for identifying reconnecting field lines. We also present a proof-of-concept model for identifying the location of reconnection along the reconnecting field lines, and use that to measure the angle at which reconnection occurs in the simulation. We find evidence that magnetic reconnection occurs preferentially near field line footpoints, and discuss the implications of this for coronal heating models.

Keywords: Magnetohydrodynamics, Magnetic fields, Solar corona, Solar magnetic reconnection
Detectability of Rotational Modulation in Kepler Sun-like Stars as a Function of Age. We examine how the fraction f of stars for which rotational modulation has been detected in Kepler light curves depends on the stellar mass M ⋆ and age t ⋆. Our sample consists of ≈850 FGK stars hosting transiting planet candidates detected from the prime Kepler mission. For these stars, atmospheric parameters have been derived using high-resolution spectra from the California-Kepler survey, and rotational modulation has been searched in Kepler light curves homogeneously. We fit stellar models to the atmospheric parameters, Gaia parallax, and Two Micron All Sky Survey magnitude of these stars and obtain samples drawn from the posterior probability distributions for their masses and ages under a given, uninformative prior. We combine them with the result of rotational modulation search to simultaneously infer the mass-age distribution of the sample as well as f(M ⋆, t ⋆), in a manner that fully takes into account mass and age uncertainties of individual stars. We find that f remains near unity up to t ⋆ ~ 3 Gyr and drops to almost zero by t ⋆ ~ 5 Gyr, although the trend is less clearly detected for stars with ≲0.9 M ⊙ due to weaker age constraints. This finding is consistent with a view that the detection of rotational modulation is limited by photometric precision to younger stars that exhibit higher-amplitude modulation, and suggests that the detectability of rotational modulation in Kepler light curves is insensitive to metallicity and activity cycles for stars younger than the Sun.

Keywords: Starspots, Light curves, Stellar magnetic fields, Stellar activity, Stellar rotation
Establishing Dust Rings and Forming Planets within Them. Radio images of protoplanetary disks demonstrate that dust grains tend to organize themselves into rings. These rings may be a consequence of dust trapping within gas pressure maxima, wherein the local high dust-to-gas ratio is expected to trigger the formation of planetesimals and eventually planets. We revisit the behavior of dust near gas pressure perturbations enforced by a planet in two-dimensional, shearing-box simulations. While dust grains collect into generally long-lived rings, particles with a small Stokes parameter τ  s  &lt; 0.1 tend to advect out of the ring within a few drift timescales. Scaled to the properties of ALMA disks, we find that rings composed of larger particles (τ  s  ≥ 0.1) can nucleate a dust clump massive enough to trigger pebble accretion, which proceeds to ingest the entire dust ring well within ~1 Myr. To ensure the survival of the dust rings, we favor a nonplanetary origin and typical grain size τ  s  ≲ 0.05-0.1. Planet-driven rings may still be possible but if so we would expect the orbital distance of the dust rings to be larger for older systems.

Keywords: Astrophysical dust processes, Gas-to-dust ratio, Protoplanetary disks, Planet formation
Dusty, Self-obscured Transients from Stellar Coalescence. We discuss the central role that dust condensation plays in shaping the observational appearance of outflows from coalescing binary systems. As binaries begin to coalesce, they shock-heat and expel material into their surroundings. Depending on the properties of the merging system, this material can expand to the point where molecules and dust form, dramatically increasing the gas opacity. We use the existing population of luminous red novae to constrain the thermodynamics of these ejecta, then apply our findings to the progressive obscuration of merging systems in the lead up to their coalescence. Compact progenitor stars near the main sequence or in the Hertzsprung gap along with massive progenitor stars have sufficiently hot circumstellar material to remain unobscured by dust. By contrast, more extended, low-mass giants should become completely optically obscured by dust formation in the circumbinary environment. We predict that 30%-50% of stellar-coalescence transients for solar-mass stars will be dusty, infrared-luminous sources. Of these, the optical transients may selectively trace complete merger outcomes while the infrared transients trace common envelope ejection outcomes.

Keywords: Stellar mergers, Transient sources, Circumstellar matter, Circumstellar dust, Common envelope evolution
SDSS-IV MaNGA: Unveiling Galaxy Interaction by Merger Stages with Machine Learning. We use machine-learning techniques to classify galaxy merger stages, which can unveil physical processes that drive the star formation and active galactic nucleus (AGN) activities during galaxy interaction. The sample contains 4690 galaxies from the integral field spectroscopy survey SDSS-IV MaNGA and can be separated into 1060 merging galaxies and 3630 nonmerging or unclassified galaxies. For the merger sample, there are 468, 125, 293, and 174 galaxies (1) in the incoming pair phase, (2) in the first pericentric passage phase, (3) approaching or just passing the apocenter, and (4) in the final coalescence phase or post-mergers. With the information of projected separation, line-of-sight velocity difference, Sloan Digital Sky Survey (SDSS) gri images, and MaNGA Hα velocity map, we are able to classify the mergers and their stages with good precision, which is the most important score to identify interacting galaxies. For the two-phase classification (binary; nonmerger and merger), the performance can be high (precision &gt; 0.90) with LGBMClassifier. We find that sample size can be increased by rotation, so the five-phase classification (nonmerger, and merger stages 1, 2, 3, and 4) can also be good (precision &gt; 0.85). The most important features come from SDSS gri images. The contribution from the MaNGA Hα velocity map, projected separation, and line-of-sight velocity difference can further improve the performance by 0%-20%. In other words, the image and the velocity information are sufficient to capture important features of galaxy interactions, and our results can apply to all the MaNGA data, as well as future all-sky surveys.

Keywords: Surveys, Galaxy interactions, Astronomy data analysis, Astrostatistics, Galaxy evolution
The 2020 Eclipse of R Aquarii in the Near-infrared: Mid-eclipse Observations of Disk Distress. The Mira in the bright, dusty, symbiotic binary R Aquarii undergoes eclipses of multiyear duration every ~44 yr by a large, opaque accretion disk. The 2020 eclipse was confirmed by I-band photometry. High-resolution M- and K-band spectra were observed near the midpoint of the eclipse, in 2020 August and September. The 4.5-5.5 μm spectrum during eclipse is a complex blend of disk and Mira features. Continuum emission from the disk region contributes to both the 2.3 μm and 4.6 μm region. The lowest energy vibration-rotation CO lines contain multiple absorption features from ~780 K gas flowing across the disk away from the Mira. CO fundamental and overtone emission lines are also present. The eccentricity of the orbit results in significant orbital variation in the size of the Roche lobes. At periastron the Roche radius of the secondary is ~4.0 au, smaller than both the 5 au geometric radius for the disk and estimates for the disk size from models. Fundamental band CO 2-1 emission originates from a thin, eccentric ring with inner radius ~4.75 au and outer radius ~6.9 au. The CO emission is identified with regions where the disk has been disrupted near the time of periastron. CO 3-2 fundamental band lines and low-excitation lines in the CO 2-0 and 3-1 overtone bands originate in a Mira-facing spot, 6.3 au from the accretion disk center, near the inner Lagrange point.

Keywords: Stellar accretion disks, Multiple star evolution, Circumstellar matter, Mira variable stars, Eclipsing binary stars, Symbiotic binary stars
Detection of Ubiquitous Weak and Impulsive Nonthermal Emissions from the Solar Corona. A ubiquitous presence of weak energy releases is one of the most promising hypotheses to explain coronal heating, referred to as the nanoflare hypothesis. The accelerated electrons associated with such weak heating events are also expected to give rise to coherent impulsive emission via plasma instabilities in the meterwave radio band, making this a promising spectral window to look for their presence. Recently Mondal et al. reported the presence of weak and impulsive emissions from quiet Sun regions which seem to meet the requirements of being radio counterparts of the hypothesized nanoflares. Detection of such low-contrast weak emission from the quiet Sun is challenging and, given their implications, it is important to confirm their presence. In this work, using data from the Murchison Widefield Array, we explore the use of an independent robust approach for their detection by separating the dominant, slowly varying component of emission from the weak impulsive one in the visibility domain. We detect milli-Solar Flux Unit-level bursts taking place all over the Sun and characterize their brightness temperatures, distributions, morphologies, durations, and associations with features seen in extreme-UV images. We also attempt to constrain the energies of the nonthermal particles using inputs from the FORWARD coronal model along with some reasonable assumptions, and find them to lie in the subpico flare (~1019-1021 erg) range. In the process, we also discover perhaps the weakest type III radio burst and another that shows clear signatures of the weakest quasi-periodic pulsations.

Keywords: Solar physics, Solar coronal heating, Quiet solar corona
Exploring the Limits of Synthetic Creation of Solar EUV Images via Image-to-image Translation. The Solar Dynamics Observatory (SDO), a NASA multispectral decade-long mission that has been daily producing terabytes of observational data from the Sun, has been recently used as a use case to demonstrate the potential of machine-learning methodologies and to pave the way for future deep space mission planning. In particular, the idea of using image-to-image translation to virtually produce extreme ultraviolet channels has been proposed in several recent studies, as a way to both enhance missions with fewer available channels and to alleviate the challenges due to the low downlink rate in deep space. This paper investigates the potential and the limitations of such a deep learning approach by focusing on the permutation of four channels and an encoder-decoder based architecture, with particular attention to how morphological traits and brightness of the solar surface affect the neural network predictions. In this work we want to answer the question: can synthetic images of the solar corona produced via image-to-image translation be used for scientific studies of the Sun? The analysis highlights that the neural network produces high-quality images over 3 orders of magnitude in count rate (pixel intensity) and can generally reproduce the covariance across channels within a 1% error. However, the model performance drastically diminishes in correspondence to extremely high energetic events like flares, and we argue that the reason is related to the rareness of such events posing a challenge to model training.

Keywords: Solar extreme ultraviolet emission, Convolutional neural networks, Solar active regions, Solar activity, GPU computing, Solar telescopes
Bethe-Heitler Signature in Proton Synchrotron Models for Gamma-Ray Bursts. We study the effect of Bethe-Heitler (BeHe) pair production on a proton synchrotron model for the prompt emission in gamma-ray bursts (GRBs). The possible parameter space of the model is constrained by consideration of the synchrotron radiation from the secondary BeHe pairs. We find two regimes of interest. (1) At high bulk Lorentz factor, large radius, and low luminosity, proton synchrotron emission dominates and produces a spectrum in agreement with observations. For part of this parameter space, a subdominant (in the MeV band) power law is created by the synchrotron emission of the BeHe pairs. This power law extends up to few tens or hundreds of MeV. Such a signature is a natural expectation in a proton synchrotron model, and it is seen in some GRBs, including GRB 190114C recently observed by the MAGIC observatory. (2) At low bulk Lorentz factor, small radius, and high luminosity, BeHe cooling dominates. The spectrum achieves the shape of a single power law with spectral index α = -3/2 extending across the entire Gamma-ray Burst Monitor/Swift energy window, incompatible with observations. Our theoretical results can be used to further constrain the spectral analysis of GRBs in the guise of proton synchrotron models.

Keywords: Gamma-ray bursts, Non-thermal radiation sources, Relativistic jets
Multispacecraft Analysis of the Properties of Magnetohydrodynamic Fluctuations in Sub-Alfvénic Solar Wind Turbulence at 1 au. We present observations of three-dimensional magnetic power spectra in wavevector space to investigate the anisotropy and scalings of sub-Alfvénic solar wind turbulence at magnetohydrodynamic (MHD) scale using the Magnetospheric Multiscale spacecraft. The magnetic power distributions are organized in a new coordinate determined by wavevectors ( $\hat{{\boldsymbol{\kappa }}}$ ) and background magnetic field ( ${\widehat{{\boldsymbol{b}}}}_{0}$ ) in Fourier space. This study utilizes two approaches to determine wavevectors: the singular value decomposition method and multispacecraft timing analysis. The combination of the two methods allows an examination of the properties of magnetic field fluctuations in terms of mode compositions without any spatiotemporal hypothesis. Observations show that fluctuations (δ B ⊥1) in the direction perpendicular to $\hat{{\boldsymbol{\kappa }}}$ and ${\widehat{{\boldsymbol{b}}}}_{0}$ prominently cascade perpendicular to ${\widehat{{\boldsymbol{b}}}}_{0}$ , and such anisotropy increases with wavenumbers. The reduced power spectra of δ B ⊥1 follow Goldreich-Sridhar scalings: $\hat{P}({k}_{\perp })\propto {k}_{\perp }^{-5/3}$ and $\hat{P}({k}_{\parallel })\propto {k}_{\parallel }^{-2}$ . In contrast, fluctuations within the $\hat{k}{\hat{b}}_{0}$ plane show isotropic behaviors: perpendicular power distributions are approximately the same as parallel distributions. The reduced power spectra of fluctuations within the $\hat{k}{\hat{b}}_{0}$ plane follow the scalings $\hat{P}({k}_{\perp })\propto {k}_{\perp }^{-3/2}$ and $\hat{P}({k}_{\parallel })\propto {k}_{\parallel }^{-3/2}$ . Comparing frequency-wavevector spectra with theoretical dispersion relations of MHD modes, we find that δ B ⊥1 are probably associated with Alfvén modes. On the other hand, magnetic field fluctuations within the $\hat{k}{\hat{b}}_{0}$ plane more likely originate from fast modes based on their isotropic behaviors. The observations of anisotropy and scalings of different magnetic field components are consistent with the predictions of current compressible MHD theory. Moreover, for the Alfvénic component, the ratio of cascading time to the wave period is found to be a factor of a few, consistent with critical balance in the strong turbulence regime. These results are valuable for further studies of energy compositions of plasma turbulence and their effects on energetic particle transport.

Keywords: Interplanetary turbulence, Solar wind
The Giant Metrewave Radio Telescope Cold-HI AT z ≈ 1 Survey. We describe the design, data analysis, and basic results of the Giant Metrewave Radio Telescope Cold-HI AT z ≈ 1 (GMRT-CATz1) survey, a 510 hr upgraded GMRT HI 21 cm emission survey of galaxies at z = 0.74-1.45 in the DEEP2 survey fields. The GMRT-CAT z1 survey is aimed at characterizing HI in galaxies during and just after the epoch of peak star formation activity in the universe, a key epoch in galaxy evolution. We obtained high-quality HI 21 cm spectra for 11,419 blue star-forming galaxies at z = 0.74-1.45, in seven pointings on the DEEP2 subfields. We detect the stacked HI 21 cm emission signal of the 11,419 star-forming galaxies, which have an average stellar mass of M * ≈ 1010 M ⊙, at 7.1σ statistical significance, obtaining an average HI mass of &lt;M H I &gt; = (13.7 ± 1.9) × 109 M ⊙. This is significantly higher than the average HI mass of &lt;M H I &gt; = (3.96 ± 0.17) × 109 M ⊙ in star-forming galaxies at z ≈ 0 with an identical stellar-mass distribution. We stack the rest-frame 1.4 GHz continuum emission of our 11,419 galaxies to infer an average star formation rate (SFR) of 8.07 ± 0.82 M ⊙ yr-1. Combining our average HI mass and average SFR estimates yields an HI depletion timescale of 1.70 ± 0.29 Gyr, for star-forming galaxies at z ≈ 1, ≈3 times lower than that of local galaxies. We thus find that, although main-sequence galaxies at z ≈ 1 have a high HI mass, their short HI depletion timescale is likely to cause quenching of their star formation activity in the absence of rapid gas accretion from the circumgalactic medium.

Keywords: Radio spectroscopy, High-redshift galaxies, Neutral hydrogen clouds, Galaxy evolution