adsabs/SciX_UAT_keywords huggingface dataset:
The First Detection of a Protostellar CO Outflow in the Small Magellanic Cloud with ALMA

Protostellar outflows are one of the most outstanding features of star formation. Observational studies over the last several decades have successfully demonstrated that outflows are ubiquitously associated with low- and high-mass protostars in solar-metallicity Galactic conditions. However, the environmental dependence of protostellar outflow properties is still poorly understood, particularly in the low-metallicity regime. Here we report the first detection of a molecular outflow in the Small Magellanic Cloud with 0.2 Z ⊙, using Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.1 pc toward the massive protostar Y246. The bipolar outflow is nicely illustrated by high-velocity wings of CO(3-2) emission at ≳15 km s-1. The evaluated properties of the outflow (momentum, mechanical force, etc.) are consistent with those of the Galactic counterparts. Our results suggest that the molecular outflows, i.e., the guidepost of the disk accretion at the small scale, might be universally associated with protostars across the metallicity range of ~0.2-1 Z ⊙.

Keywords: star formation; protostars; molecular clouds; small magellanic cloud; interstellar medium; local group
Aqueous Alteration on Asteroids Simplifies Soluble Organic Matter Mixtures

Biologically relevant abiotic extraterrestrial soluble organic matter (SOM) has been widely investigated to study the origin of life and the chemical evolution of protoplanetary disks. Synthesis of biologically relevant organics, in particular, seems to require aqueous environments in the early solar system. However, SOM in primitive meteorites includes numerous chemical species besides the biologically relevant ones, and the reaction mechanisms that comprehensively explain the complex nature of SOM are unknown. Besides, the initial reactants, which formed before asteroid accretion, were uncharacterized. We examined the mass distribution of SOM extracted from three distinct Tagish Lake meteorite fragments, which exhibit different degrees of aqueous alteration though they originated from a single asteroid. We report that mass distributions of SOM in the primordial fragments are well fit by the Schulz-Zimm (SZ) model for the molecular weight distribution patterns found in chain-growth polymerization experiments. Also, the distribution patterns diverge further from SZ with increasing degrees of aqueous alteration. These observations imply that the complex nature of the primordial SOM (1) was established before severe alteration on the asteroid, (2) possibly existed before parent-body accretion, and (3) later became simplified on the asteroid. Therefore, aqueous reactions on asteroids are not required conditions for cultivating complex SOM. Furthermore, we found that overall H/C ratios of SOM decrease with increasing aqueous alteration, and the estimate of H loss from the SOM is 10%-30%. Organics seem to be a significant H2 source that may have caused subsequent chemical reactions in the Tagish Lake meteorite parent body.

Keywords: carbonaceous chondrites; solar system formation; molecule formation; solar nebulae; protoplanetary disks
Understanding Accretion Variability through TESS Observations of Taurus

Interpreting the short-timescale variability of the accreting, young, low-mass stars known as Classical T Tauri stars remains an open task. Month-long, continuous light curves from the Transiting Exoplanet Survey Satellite (TESS) have become available for hundreds of T Tauri stars. With this vast data set, identifying connections between the variability observed by TESS and short-timescale accretion variability is valuable for characterizing the accretion process. To this end, we obtained short-cadence TESS observations of 14 T Tauri stars in the Taurus star formation region along with simultaneous ground-based, UBVRI-band photometry to be used as accretion diagnostics. In addition, we combine our data set with previously published simultaneous near-UV-near-IR Hubble Space Telescope spectra for one member of the sample. We find evidence that much of the short-timescale variability observed in the TESS light curves can be attributed to changes in the accretion rate, but note significant scatter between separate nights and objects. We identify hints of time lags within our data set that increase at shorter wavelengths, which we suggest may be evidence of longitudinal density stratification of the accretion column. Our results highlight that contemporaneous, multiwavelength observations remain critical for providing context for the observed variability of these stars.

Keywords: protoplanetary disks; stellar accretion
The Hyperluminous, Dust-obscured Quasar W2246-0526 at z = 4.6: Detection of Parsec-scale Radio Activity

WISE J224607.56-052634.9 (W2246-0526) is a hyperluminous (Lbol ≈ 1.7 × 1014 L⊙), dust-obscured, and radio-quiet quasar at redshift z = 4.6. It plays a key role in probing the transition stage between dusty starbursts and unobscured quasars in the coevolution of galaxies and supermassive black holes (SMBHs). To search for the evidence of the jet activity launched by the SMBH in W2246-0526, we performed very long baseline interferometry observations of its radio counterpart with the European VLBI Network (EVN) plus the enhanced Multi Element Remotely Linked Interferometer Network (e-MERLIN) at 1.66 GHz and the Very Long Baseline Array (VLBA) at 1.44 and 1.66 GHz. The deep EVN plus e-MERLIN observations detect a compact (size ≤ 32 pc) sub-mJy component contributing about 10% of its total flux density, which spatially coincides with the peak of dust continuum and [C II] emissions. Together with its relatively high brightness temperature ( ≥ 8 × 106 K), we interpret the component as a consequence of nonthermal radio activity powered by the central SMBH, which likely originates from a stationary jet base. The resolved-out radio emission possibly come from a diffuse jet, quasar-driven winds, or both, while the contribution by star formation activity is negligible. Moreover, we propose an updated geometry structure of its multiwavelength active nucleus and shed light on the radio quasar selection bias toward the blazars at z > 4.

Keywords: high-redshift galaxies; quasars; radio continuum emission; high-luminosity active galactic nuclei
TOI-1634 b: An Ultra-short-period Keystone Planet Sitting inside the M-dwarf Radius Valley

Studies of close-in planets orbiting M dwarfs have suggested that the M-dwarf radius valley may be well explained by distinct formation timescales between enveloped terrestrials and rocky planets that form at late times in a gas-depleted environment. This scenario is at odds with the picture that close-in rocky planets form with a primordial gaseous envelope that is subsequently stripped away by some thermally driven mass-loss process. These two physical scenarios make unique predictions of the rocky/enveloped transition's dependence on orbital separation such that studying the compositions of planets within the M-dwarf radius valley may be able to establish the dominant physics. Here, we present the discovery of one such keystone planet: the ultra-short-period planet TOI-1634 b (P = 0.989 days, $F=121{F}_{\oplus }$, ${r}_{p}={1.790}_{-0.081}^{+0.080}$ R⊕) orbiting a nearby M2 dwarf (Ks = 8.7, Rs = 0.450 R⊙, Ms = 0.502 M⊙) and whose size and orbital period sit within the M-dwarf radius valley. We confirm the TESS-discovered planet candidate using extensive ground-based follow-up campaigns, including a set of 32 precise radial velocity measurements from HARPS-N. We measure a planetary mass of ${4.91}_{-0.70}^{+0.68}$ M⊕, which makes TOI-1634 b inconsistent with an Earth-like composition at $5.9\sigma $ and thus requires either an extended gaseous envelope, a large volatile-rich layer, or a rocky composition that is not dominated by iron and silicates to explain its mass and radius. The discovery that the bulk composition of TOI-1634 b is inconsistent with that of Earth supports the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with ${M}_{s}\lesssim 0.5$ M⊙.

Keywords: planetary system formation; exoplanet structure; radial velocity; transit photometry; low mass stars
Exploring Asymmetric Substructures of the Outer Disk Based on the Conjugate Angle of the Radial Action

We use the conjugate angle of radial action (θ R ), the best representation of the orbital phase, to explore the "midplane," "north branch," "south branch," and "Monoceros area" disk structures that were previously revealed in the LAMOST K giants. The former three substructures, identified by their 3D kinematical distributions, have been shown to be projections of the phase space spiral (resulting from nonequilibrium phase mixing). In this work, we find that all of these substructures associated with the phase spiral show high aggregation in conjugate angle phase space, indicating that the clumping in conjugate angle space is a feature of ongoing, incomplete phase mixing. We do not find the Z-V Z phase spiral located in the "Monoceros area," but we do find a very highly concentrated substructure in the quadrant of conjugate angle space with the orbital phase from the apocenter to the guiding radius. The existence of the clump in conjugate angle space provides a complementary way to connect the "Monoceros area" with the direct response to a perturbation from a significant gravitationally interactive event. Using test particle simulations, we show that these features are analogous to disturbances caused by the impact of the last passage of the Sagittarius dwarf spheroidal galaxy.

Keywords: galaxy kinematics; galaxy anticenters
Abundances of Helium, Neon, Magnesium and Phosphorus in the Atmosphere of the Bp He-weak Star HD 175156

The synthesis of two spectral intervals in the optical range allows to determine LTE abundances of helium, magnesium, phosphorus and neon for this evolved B subgiant. Compared to the solar abundances, helium, neon and phosphorus are found to be overabundant by a factor of 5, magnesium by a factor of 4. The helium line at 4471 Å recorded by two different instruments about ten years apart does not vary. Additional information on the abundances of other elements was also inferred: carbon, oxygen, aluminum, sulfur and iron have abundances very close to the solar values, in contrast nitrogen, titanium and xenon require mild overabundances.

Keywords: chemically peculiar stars; helium-weak stars
Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array

We analyze data from the Hydrogen Epoch of Reionization Array (HERA). This is the third in a series of papers on the closure phase delay spectrum technique designed to detect the H I 21 cm emission from cosmic reionization. We present the details of the data and models employed in the power spectral analysis and discuss limitations to the process. We compare images and visibility spectra made with HERA data to parallel quantities generated from sky models based on the Galactic and Extra-Galactic All-Sky MWA (GLEAM) survey, incorporating the HERA telescope model. We find reasonable agreement between images made from HERA data with those generated from the models, down to the confusion level. For the visibility spectra, there is broad agreement between model and data across the full band of ∼80 MHz. However, models with only GLEAM sources do not reproduce a roughly sinusoidal spectral structure at the tens of percent level seen in the observed visibility spectra on scales of ∼10 MHz on 29 m baselines. We find that this structure is likely due to diffuse Galactic emission, predominantly the Galactic plane, filling the far sidelobes of the antenna primary beam. We show that our current knowledge of the frequency dependence of the diffuse sky radio emission, and the primary beam at large zenith angles, is inadequate to provide an accurate reproduction of the diffuse structure in the models. We discuss some implications arising due to this missing structure in the models, in terms of calibration, and in the search for the H I 21 cm signal, as well as possible mitigation techniques.

Keywords: cosmology; cosmological evolution; radio interferometry; reionization
Analytic Post-Newtonian Astrometric and Spectroscopic Models of Orbits around Black Holes

Observations of the S stars, the cluster of young stars in the inner 0.1 pc of the Galactic center, have been crucial in providing conclusive evidence for a supermassive black hole at the center of our galaxy. Since some of the stars have orbits less than that of a typical human lifetime, it is possible to observe multiple orbits and test the weak-field regime of general relativity. Current calculations of orbits require relatively slow and expensive computations in order to perform numerical integrations for the position and momentum of each star at each observing time. In this paper, we present a computationally efficient, first-order post-Newtonian model for the astrometric and spectroscopic data gathered for the S stars. We find that future, 30 m class telescopes-and potentially even current large telescopes with very high spectroscopic resolution-may be able to detect the Shapiro effect for an S star in the next decade or so.

Keywords: general relativity; two-body problem; orbital motion; supermassive black holes; galactic center
Modeling the Solar Wind Turbulent Cascade Including Cross Helicity: With and Without Expansion

Simulations of the turbulent cascade forming in the solar wind, including cross helicity, commonly adopt a homogeneous setup, not taking into account wind expansion. Here we want to assess the predictions of decaying 3D compressible (low Mach number) MHD simulations, respectively homogeneous and with expansion, in order to examine which is the most fruitful approach to understanding the turbulent cascade in the solar wind. We follow turbulent evolution during 10 nonlinear turnover times, considering several initial values of the initial spectral slope and cross helicity. In the expanding case, the transverse sizes of the plasma volume are stretched by a factor of 5 during the simulation, corresponding to traveling from 0.2 up to 1 au. In homogeneous simulations, the relative cross helicity rises, and the Elsässer spectra E ± show "pinning," with a steep dominant spectrum and flat subdominant spectrum, the final spectral indices depending on cross helicity but not initial indices. With expansion, the relative cross helicity decreases, and dominant and subdominant spectra share the same index, with the index relaxing to an asymptotic value that generally depends on the initial index. The absence of pinning, as well as the decrease of relative cross helicity, probably both rely on the permanent injection by expansion of an excess of magnetic energy at the largest scales, equivalent to injecting subdominant energy. Also, spectra generally steepen when initially starting flatter than k -5/3 but stop evolving at a finite time/distance.

Keywords: interplanetary turbulence; solar wind; space plasmas; alfven waves; interplanetary medium; magnetohydrodynamics
Isolated Pulsar Population Synthesis with Simulation-based Inference

We combine pulsar population synthesis with simulation-based inference (SBI) to constrain the magnetorotational properties of isolated Galactic radio pulsars. We first develop a framework to model neutron star birth properties and their dynamical and magnetorotational evolution. We specifically sample initial magnetic field strengths, B, and spin periods, P, from lognormal distributions and capture the late-time magnetic field decay with a power law. Each lognormal is described by a mean, , and standard deviation, , while the power law is characterized by the index, a late. We subsequently model the stars' radio emission and observational biases to mimic detections with three radio surveys, and we produce a large database of synthetic P– diagrams by varying our five magnetorotational input parameters. We then follow an SBI approach that focuses on neural posterior estimation and train deep neural networks to infer the parameters' posterior distributions. After successfully validating these individual neural density estimators on simulated data, we use an ensemble of networks to infer the posterior distributions for the observed pulsar population. We obtain , and , for the lognormal distributions and for the power law at the 95% credible interval. We contrast our results with previous studies and highlight uncertainties of the inferred a late value. Our approach represents a crucial step toward robust statistical inference for complex population synthesis frameworks and forms the basis for future multiwavelength analyses of Galactic pulsars.

Keywords: neutron stars; radio pulsars; pulsars
Evidence of Wind Signatures in the Gas Velocity Profiles of Red Geysers

Spatially resolved spectroscopy from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey has revealed a class of quiescent, relatively common early-type galaxies termed "red geysers" that possibly host large-scale active galactic nuclei-driven winds. Given their potential importance in maintaining a low level of star formation at late times, additional evidence confirming that winds are responsible for the red geyser phenomenon is critical. In this work, we present follow-up observations with the Echellette Spectrograph and Imager (ESI) at the Keck telescope of two red geysers (z < 0.1) using multiple long slit positions to sample different regions of each galaxy. Our ESI data with a spectral resolution (R) ∼ 8000 improve upon MaNGA's resolution by a factor of 4, allowing us to resolve the ionized gas velocity profiles along the putative wind cone with an instrumental resolution of σ = 16 km s-1. The line profiles of Hα and [N II] λ6584 show asymmetric shapes that depend systematically on location: extended blue wings on the redshifted side of the galaxy and red wings on the opposite side. We construct a simple wind model and show that our results are consistent with geometric projections through an outflowing conical wind oriented at an angle toward the line of sight. An alternative hypothesis that assigns the asymmetric pattern to "beam smearing" of a rotating, ionized gas disk does a poor job matching the line asymmetry profiles. While our study features just two sources, it lends further support to the notion that red geysers are the result of galaxy-scale winds.

Keywords: agn host galaxies; early-type galaxies; elliptical galaxies; emission line galaxies; galaxies; liner galaxies; quenched galaxies; galactic winds
Sensitive Multibeam Targeted SETI Observations toward 33 Exoplanet Systems with FAST

As a major approach to looking for life beyond the Earth, the search for extraterrestrial intelligence (SETI) is committed to searching for technosignatures such as engineered radio signals that are indicative of technologically capable life. In this paper, we report a targeted SETI campaign employing an observation strategy named multibeam coincidence matching at the Five-hundred-meter Aperture Spherical radio Telescope toward 33 known exoplanet systems, searching for ETI narrowband drifting signals across 1.05-1.45 GHz in two orthogonal linear polarization directions separately. A signal at 1140.604 MHz detected from the observation toward Kepler-438 originally piqued our interest because its features are roughly consistent with assumed ETI technosignatures. However, evidences such as its polarization characteristics are able to eliminate the possibility of an extraterrestrial origin. Our observations achieve an unprecedented sensitivity because the minimum equivalent isotropic radiated power we are able to detect reaches 1.48 × 109 W.

Keywords: astrobiology; search for extraterrestrial intelligence; technosignatures; exoplanets
Evolution of a Relativistic Outflow and X-Ray Corona in the Extreme Changing-look AGN 1ES 1927+654

1ES 1927+654 is a paradigm-defying active galactic nucleus (AGN) and one of the most peculiar X-ray nuclear transients. In early 2018, this well-known AGN underwent a changing-look event, in which broad optical emission lines appeared and the optical flux increased. Yet, by 2018 July, the X-ray flux had dropped by over two orders of magnitude, indicating a dramatic change in the inner accretion flow. With three years of observations with NICER, XMM-Newton, and NuSTAR, we present the X-ray evolution of 1ES 1927+654, which can be broken down into three phases: (1) an early super-Eddington phase with rapid variability in X-ray luminosity and spectral parameters, (2) a stable super-Eddington phase at the peak X-ray luminosity, and (3) a steady decline back to the pre-outburst luminosity and spectral parameters. For the first time, we witnessed the formation of the X-ray corona, as the X-ray spectrum transitioned from thermally dominated to primarily Comptonized. We also track the evolution of the prominent, broad 1 keV feature in the early X-ray spectra and show that this feature can be modeled with blueshifted reflection (z = -0.33) from a single-temperature blackbody irradiating spectrum using xillverTDE, a new flavor of the xillver models. Thus, we propose that the 1 keV feature could arise from reflected emission off the base of an optically thick outflow from a geometrically thick, super-Eddington inner accretion flow, connecting the inner accretion flow with outflows launched during extreme accretion events (e.g., tidal disruption events). Lastly, we compare 1ES 1927+654 to other nuclear transients and discuss applications of xillverTDE to super-Eddington accretors.

Keywords: active galactic nuclei; high energy astrophysics; seyfert galaxies; supermassive black holes; x-ray transient sources
Unveiling the Small-scale Jets in the Rapidly Growing Supermassive Black Hole IZw1

Accretion of black holes at near-Eddington or super-Eddington rates represents the most powerful episode driving black hole growth, potentially occurring across various types of objects. However, the physics governing accretion and jet–disk coupling in such states remains unclear, primarily due to the difficulty in detecting associated jets, which may emit extremely weakly or exhibit episodic behavior. Only a few near/super-Eddington systems have demonstrated radio activity, and it remains uncertain whether jets exist and what their properties are in super-Eddington active galactic nuclei (AGNs) and ultraluminous X-ray sources. This uncertainty stems mainly from the complex radio emission mix, which includes contributions from jets, star formation activity, photoionized gas, accretion disk wind, and coronal activity. In this work, we conducted high-resolution, very long baseline interferometry observations to investigate jets in the highly accreting narrow-line Seyfert I system I Zw 1. Our observations successfully revealed small-scale jets (with a linear size of ∼45 pc) at both 1.5 and 5 GHz, based on the high radio brightness temperature, radio morphology, and spectral index distribution. Additionally, the parsec-scale jet observed in I Zw 1 displays a knotted morphology reminiscent of other sources accreting at similar rates. In summary, the high accretion rates and jet properties observed in the AGN I Zw 1 may support the AGN/X-ray binary analogy in this extreme state.

Keywords: active galactic nuclei; accretion; very long baseline interferometry; radio jets; seyfert galaxies