adsabs/SciX_UAT_keywords huggingface dataset:
Detection of Carbon Monoxide's 4.6 Micron Fundamental Band Structure in WASP-39b's Atmosphere with JWST NIRSpec G395H

Carbon monoxide (CO) is predicted to be the dominant carbon-bearing molecule in giant planet atmospheres and, along with water, is important for discerning the oxygen and therefore carbon-to-oxygen ratio of these planets. The fundamental absorption mode of CO has a broad, double-branched structure composed of many individual absorption lines from 4.3 to 5.1 μm, which can now be spectroscopically measured with JWST. Here we present a technique for detecting the rotational sub-band structure of CO at medium resolution with the NIRSpec G395H instrument. We use a single transit observation of the hot Jupiter WASP-39b from the JWST Transiting Exoplanet Community Early Release Science (JTEC ERS) program at the native resolution of the instrument (R ~ 2700) to resolve the CO absorption structure. We robustly detect absorption by CO, with an increase in transit depth of 264 ± 68 ppm, in agreement with the predicted CO contribution from the best-fit model at low resolution. This detection confirms our theoretical expectations that CO is the dominant carbon-bearing molecule in WASP-39b's atmosphere and further supports the conclusions of low C/O and supersolar metallicities presented in the JTEC ERS papers for WASP-39b.

Keywords: exoplanet atmospheres; transmission spectroscopy; near infrared astronomy
Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph: Equatorial Latitudes in L Dwarf Atmospheres Are Cloudier

We report direct observational evidence for a latitudinal dependence of dust cloud opacity in ultracool dwarfs, indicating that equatorial latitudes are cloudier than polar latitudes. These results are based on a strong positive correlation between the viewing geometry and the mid-infrared silicate absorption strength in mid-L dwarfs using mid-infrared spectra from the Spitzer Space Telescope and spin axis inclination measurements from available information in the literature. We confirmed that the infrared color anomalies of L dwarfs positively correlate with dust cloud opacity and viewing geometry, where redder objects are inclined equator-on and exhibit more opaque dust clouds, while dwarfs viewed at higher latitudes and with more transparent clouds are bluer. These results show the relevance of viewing geometry to explain the appearance of brown dwarfs and provide insight into the spectral diversity observed in substellar and planetary atmospheres. We also find a hint that dust clouds at similar latitudes may have higher opacity in low-surface gravity dwarfs than in higher-gravity objects.

Keywords: l dwarfs; brown dwarfs; extrasolar gaseous giant planets; solar system gas giant planets; exoplanet atmospheres; planetary atmospheres
The Coupling of Galactic Dark Matter Halos with Stellar Bars

Resonant torques couple stellar bars to dark matter halos. Here we use high-resolution numerical simulations to demonstrate long-term angular momentum transfer between stellar bars and dark matter orbits of varying orientation. We show that bar-driven reversals of dark matter orbit orientations can play a surprisingly large role in the evolution of the bar pattern speed. In predominantly prograde (corotating) halos, dark matter orbits become trapped in the stellar bar, forming a parallel dark matter bar. This dark matter bar reaches more than double the vertical height of the stellar bar. In halos dominated by retrograde orbits, a dark matter wake forms oriented perpendicular to the stellar bar. These dark matter overdensities provide a novel space to look for dark matter annihilation or decay signals. We predict that the Milky Way hosts a dark matter bar aligned with the stellar bar as well as a dark matter wake, the near side of which should extend from the Galactic center to a galactic longitude of l ≈ 323°.

Keywords: galaxy dark matter halos; barred spiral galaxies; computational astronomy
New Analytic Solutions for Galaxy Evolution. II. Wind Recycling, Galactic Fountains, and Late-type Galaxies

We generalize the analytic solutions presented in Pantoni et al. by including a simple yet effective description of wind recycling and galactic fountains, with the aim of self-consistently investigating the spatially averaged time evolution of the gas, stellar, metal, and dust content in disk-dominated late-type galaxies (LTGs). Our analytic solutions, when supplemented with specific prescriptions for parameter setting and with halo accretion rates from N-body simulations, can be exploited to reproduce the main statistical relationships followed by local LTGs; these involve, as a function of the stellar mass, the star formation efficiency, the gas mass fraction, the gas/stellar metallicity, the dust mass, the star formation rate, the specific angular momentum, and the overall mass/metal budget. Our analytic solutions allow us to easily disentangle the diverse role of the main physical processes ruling galaxy formation in LTGs; in particular, we highlight the crucial relevance of wind recycling and galactic fountains in efficiently refurnishing the gas mass, extending the star formation timescale, and boosting the metal enrichment in gas and stars. All in all, our analytic solutions constitute a transparent, handy, and fast tool that can provide a basis for improving the (sub-grid) physical recipes presently implemented in more sophisticated semi-analytic models and numerical simulations, and can serve as a benchmark for interpreting and forecasting current and future spatially averaged observations of local and higher redshift LTGs.

Keywords: late-type galaxies; galaxy evolution; galaxy formation; galaxy fountains
Global Impact of Emerging Internetwork Fields on the Low Solar Atmosphere

Small-scale, newly emerging internetwork (IN) magnetic fields are considered a viable source of energy and mass for the solar chromosphere and possibly the corona. Multiple studies show that single events of flux emergence can indeed locally heat the low solar atmosphere through interactions of the upward propagating magnetic loops and the preexisting ambient field lines. However, the global impact of the newly emerging IN fields on the solar atmosphere is still unknown. In this paper, we study the spatiotemporal evolution of IN bipolar flux features and analyze their impact on the energetics and dynamics of the quiet-Sun atmosphere. We use high-resolution, multiwavelength, coordinated observations obtained with the Interface Region Imaging Spectrograph, Hinode, and the Solar Dynamics Observatory to identify emerging IN magnetic fields and follow their evolution. Our observational results suggest that only the largest IN bipoles are capable of heating locally the low solar atmosphere, while the global contribution of these bipoles appears to be marginal. However, the total number of bipoles detected and their impact estimated in this work is limited by the sensitivity level, spatial resolution, and duration of our observations. To detect smaller and weaker IN fields that would maintain the basal flux, and examine their contribution to the chromospheric heating, we will need higher resolution, higher sensitivity, and longer time series obtained with current and next-generation ground- and space-based telescopes.

Keywords: solar magnetic fields; solar photosphere; solar chromosphere; solar transition region; solar magnetic flux emergence
Speckle Space-Time Covariance in High-contrast Imaging

We introduce a new framework for point-spread function subtraction based on the spatiotemporal variation of speckle noise in high-contrast imaging data where the sampling timescale is faster than the speckle evolution timescale. One way that space-time covariance arises in the pupil is as atmospheric layers translate across the telescope aperture and create small, time-varying perturbations in the phase of the incoming wavefront. The propagation of this field to the focal plane preserves some of that space-time covariance. To utilize this covariance, our new approach uses a Karhunen-Loève transform on an image sequence, as opposed to a set of single reference images as in previous applications of Karhunen-Loève Image Processing (KLIP) for high-contrast imaging. With the recent development of photon-counting detectors, such as microwave kinetic inductance detectors, this technique now has the potential to improve contrast when used as a post-processing step. Preliminary testing on simulated data shows this technique can improve contrast by at least 10%-20% from the original image, with significant potential for further improvement. For certain choices of parameters, this algorithm may provide larger contrast gains than spatial-only KLIP.

Keywords: exoplanet detection methods; astronomy data reduction; astronomical techniques; observational astronomy; direct imaging; coronagraphic imaging; astronomical methods; infrared astronomy; ground-based astronomy
Electron-capture Supernovae of Super-AGB Stars: Sensitivity on Input Physics

Stars of M ∼ 8-10 M⊙ on their main sequence form strongly electron-degenerate oxygen-neon-magnesium (ONeMg) cores and become super-asymptotic giant branch stars. If such an ONeMg core grows to 1.38 M⊙, electron captures on 20Ne(e, νe)20F(e, νe)20O take place and ignite O-Ne deflagration around the center. In this work, we perform two-dimensional hydrodynamical simulations of the propagation of the O-Ne flame to see whether such a flame triggers a thermonuclear explosion or induces a collapse of the ONeMg core due to subsequent electron capture behind the flame. We present a series of models to explore how the outcome depends on model parameters for a central density ranging between 109.80 and 1010.20 g cm-3, flame structures of both centered and off-centered ignition kernels, special and general relativistic effects, turbulent flame speed formulae, and the treatments of laminar burning phase. We obtain bifurcation between the electron-capture induced collapse and thermonuclear explosion depending mainly on the central density. We find that the ONeMg core obtained from stellar evolutionary models has a high tendency to collapse into a neutron star. We discuss the implications of the electron-capture supernovae in chemical evolution and the possible observational signals of this class of supernovae.

Keywords: supernovae; asymptotic giant branch stars; hydrodynamical simulations; neutron stars
Revealing the Dark Threads of the Cosmic Web

Modern cosmology predicts that matter in our universe today has assembled into a vast network of filamentary structures colloquially termed the "cosmic web." Because this matter is either electromagnetically invisible (I.e., dark) or too diffuse to image in emission, tests of this cosmic web paradigm are limited. Wide-field surveys do reveal web-like structures in the galaxy distribution, but these luminous galaxies represent less than 10% of baryonic matter. Statistics of absorption by the intergalactic medium (IGM) via spectroscopy of distant quasars support the model yet have not conclusively tied the diffuse IGM to the web. Here, we report on a new method inspired by the Physarum polycephalum slime mold that is able to infer the density field of the cosmic web from galaxy surveys. Applying our technique to galaxy and absorption-line surveys of the local universe, we demonstrate that the bulk of the IGM indeed resides in the cosmic web. From the outskirts of cosmic web filaments, at approximately the cosmic mean matter density (ρm) and ∼5 virial radii from nearby galaxies, we detect an increasing H I absorption signature toward higher densities and the circumgalactic medium, to ∼200ρm. However, the absorption is suppressed within the densest environments, suggesting shock-heating and ionization deep within filaments and/or feedback processes within galaxies.

Keywords: cosmic web; intergalactic medium; intergalactic filaments; voids; quasar absorption line spectroscopy; circumgalactic medium; galaxy evolution; galaxy quenching
Influence of an Upstream Dynamic Pressure Pulse on Venus-Solar Wind Interaction by Multispecies Magnetohydrodynamic Simulation

As an unmagnetized planet, Venus does not have a global dipole magnetic field like Earth. The solar wind interacts directly with the Venusian ionosphere. In this paper, the interaction between solar wind and the Venusian upper atmosphere is investigated by conducting a three-dimensional multispecies magnetohydrodynamic (MHD) model, in which the Venusian ionosphere is developed self-consistently by considering chemical reactions among four major ion species (H+, O2 +, O+, and CO2 +). Based on this developed MHD model, we mainly study the effects of the impulsive solar wind dynamic pressure on the interaction process. Simulation results reveal that the locations of the bow shock and magnetic pileup boundary show an abrupt compression, then expansion, and finally shrinkage to reach a new steady state with the influence of the impulsive dynamic pressure. The recovery time of the large-scale magnetic field is a few minutes. In addition, the peak escape fluxes are enhanced by about 1 order of magnitude due to the increased solar wind dynamic pressure pulse.

Keywords: venus
Mutual Inclination Excitation by Stellar Oblateness

Ultra-short-period planets (USPs) provide important clues to planetary formation and migration. It was recently found that the mutual inclinations of the planetary systems are larger if the inner orbits are closer (≲5R*) and if the planetary period ratios are larger (P2/P1 ≳ 5). This suggests that the USPs experienced both inclination excitation and orbital shrinkage. Here we investigate the increase in the mutual inclination due to stellar oblateness. We find that the stellar oblateness (within ∼1 Gyr) is sufficient to enhance the mutual inclination to explain the observed signatures. This suggests that the USPs can migrate closer to the host star in a near coplanar configuration with their planetary companions (e.g., disk migration+tides or in situ+tides), before mutual inclination gets excited due to stellar oblateness.

Keywords: exoplanet systems; exoplanet dynamics
Looking at Blazar Light-curve Periodicities with Gaussian Processes

Temporal analysis of blazar flux is a powerful tool to draw inferences about the emission processes and physics of these sources. In the most general case, the available light curves are irregularly sampled and influenced by gaps, and in addition are also affected by correlated noise, making their analysis complicated. Gaussian processes may offer a viable tool to assess the statistical significance of proposed periods in light curves characterized by any sampling and noise pattern. We infer the significance of the periods proposed in the literature for two well known blazars with multiple claims of possible year-long periodicity: PG 1553 + 113 and PKS 2155-304, in the high-energy and optical bands. Adding a periodic component to the modeling gives a better statistical description of the analyzed light curves. The improvement is rather solid for PG 1553 + 113, both at high energies and in the optical, while for PKS 2155-304 at high energies the improvement is not yet strong enough to allow cogent claims, and no evidence for periodicity emerged from the analysis in the optical. Modeling a light curve by means of Gaussian processes, in spite of being relatively computationally demanding, allows us to derive a wealth of information about the data under study and suggests an original analysis framework for light curves of astrophysical interest.

Keywords: blazars; gaussian processes regression; lomb-scargle periodogram; time series analysis; astrostatistics techniques
Locating the Alfvénic Speed Transition in the Solar Corona

The region through which the solar wind (SW) radial outflow speed overtakes the MHD wave speed is of interest to studies of SW formation and evolution. Alfvén wave speed, which is the characteristic propagation speed of low-frequency MHD perturbations, is derived from the magnetic field intensity and plasma mass density. In the inner coronal regions, these parameters are often estimated using empirical models based on remote sensing observations. Parker Solar Probe (PSP) orbital encounter 4 provides, for the first time, in situ coronal plasma measurements to determine Alfvén speeds within 30 solar radii of the heliocenter. We combined the PSP SW speed measurements and calculated Alfvén speeds with inner corona wind speed results from remote sensing studies. The zone of super-Alfvénic speed cross-over is estimated to range 10-27 R⊙ for the near-equatorial corona. Future PSP data will constrain this estimate further.

Keywords: solar wind; solar corona; magnetohydrodynamics
Grain Alignment in the Circumstellar Shell of IRC+10° 216

Dust-induced polarization in the interstellar medium (ISM) is due to asymmetric grains aligned with an external reference direction, usually the magnetic field. For both the leading alignment theories, the alignment of the grain's angular momentum with one of its principal axes and the coupling with the magnetic field requires the grain to be paramagnetic. Of the two main components of interstellar dust, silicates are paramagnetic, while carbon dust is diamagnetic. Hence, carbon grains are not expected to align in the ISM. To probe the physics of carbon grain alignment, we have acquired Stratospheric Observatory for Infrared Astronomy/Higch-resolution Airborne Wideband Camera-plus far-infrared photometry and polarimetry of the carbon-rich circumstellar envelope (CSE) of the asymptotic giant branch star IRC+10° 216. The dust in such CSEs are fully carbonaceous and thus provide unique laboratories for probing carbon grain alignment. We find a centrosymmetric, radial, polarization pattern, where the polarization fraction is well correlated with the dust temperature. Together with estimates of a low fractional polarization from optical polarization of background stars, we interpret these results to be due to a second-order, direct radiative external alignment of grains without internal alignment. Our results indicate that (pure) carbon dust does not contribute significantly to the observed ISM polarization, consistent with the nondetection of polarization in the 3.4 μm feature due to aliphatic CH bonds on the grain surface.

Keywords: circumstellar dust; magnetic fields; carbonaceous grains; asymptotic giant branch stars
HEALPix Alchemy: Fast All-Sky Geometry and Image Arithmetic in a Relational Database for Multimessenger Astronomy Brokers

Efficient searches for electromagnetic counterparts to gravitational wave, high-energy neutrino, and gamma-ray burst events demand rapid processing of image arithmetic and geometry set operations in a database to cross-match galaxy catalogs, observation footprints, and all-sky images. Here we introduce HEALPix Alchemy, an open-source, pure Python implementation of a set of methods that enables rapid all-sky geometry calculations. HEALPix Alchemy is built upon HEALPix, a spatial indexing strategy that is widely used in astronomical databases as well as the native format of LIGO-Virgo-KAGRA gravitational-wave sky localization maps. Our approach leverages new multirange types built into the PostgreSQL 14 database engine. This enables fast all-sky queries against probabilistic multimessenger event localizations and telescope survey footprints. Questions such as "What are the galaxies contained within the 90% credible region of an event?" and "What is the rank-ordered list of the fields within an observing footprint with the highest probability of containing the event?" can be performed in less than a few seconds on commodity hardware using off-the-shelf cloud-managed database implementations without server-side database extensions. Common queries scale roughly linearly with the number of telescope pointings. As the number of fields grows into the hundreds or thousands, HEALPix Alchemy is orders of magnitude faster than other implementations. HEALPix Alchemy is now used as the spatial geometry engine within SkyPortal, which forms the basis of the Zwicky Transient Facility transient marshal, called Fritz.

Keywords: gravitational wave astronomy; time domain astronomy; virtual observatories; cloud computing; astronomy databases
Observational Signatures of Frame Dragging in Strong Gravity

Objects orbiting in the presence of a rotating massive body experience a gravitomagnetic frame-dragging effect, known as the Lense-Thirring effect, that has been experimentally confirmed in the weak-field limit. In the strong-field limit, near the horizon of a rotating black hole, frame dragging becomes so extreme that all objects must co-rotate with the black hole's angular momentum. In this work, we perform general relativistic numerical simulations to identify observable signatures of frame dragging in the strong-field limit that appear when infalling gas is forced to flip its direction of rotation as it is being accreted. In total intensity images, infalling streams exhibit "S"-shaped features due to the switch in the tangential velocity. In linear polarization, a flip in the handedness of spatially resolved polarization ticks as a function of radius encodes a transition in the magnetic field geometry that occurs due to magnetic flux freezing in the dragged plasma. Using a network of telescopes around the world, the Event Horizon Telescope collaboration has demonstrated that it is now possible to directly image black holes on event horizon scales. We show that the phenomena described in this work would be accessible to the next-generation Event Horizon Telescope and extensions of the array into space, which would produce spatially resolved images on event horizon scales with higher spatial resolution and dynamic range.

Keywords: accretion; magnetohydrodynamical simulations; supermassive black holes; low-luminosity active galactic nuclei; very long baseline interferometry; submillimeter astronomy; radiative transfer; polarimetry; general relativity; ergosphere
Identifying Planetary Transit Candidates in TESS Full-frame Image Light Curves via Convolutional Neural Networks

The Transiting Exoplanet Survey Satellite (TESS) mission measured light from stars in ∼75% of the sky throughout its 2 yr primary mission, resulting in millions of TESS 30-minute-cadence light curves to analyze in the search for transiting exoplanets. To search this vast data trove for transit signals, we aim to provide an approach that both is computationally efficient and produces highly performant predictions. This approach minimizes the required human search effort. We present a convolutional neural network, which we train to identify planetary transit signals and dismiss false positives. To make a prediction for a given light curve, our network requires no prior transit parameters identified using other methods. Our network performs inference on a TESS 30-minute-cadence light curve in ∼5 ms on a single GPU, enabling large-scale archival searches. We present 181 new planet candidates identified by our network, which pass subsequent human vetting designed to rule out false positives. Our neural network model is additionally provided as open-source code for public use and extension.

Keywords: exoplanet detection methods; exoplanets; neural networks; convolutional neural networks