Sazuna/UAT_keywords huggingface dataset:
The Oxidation–Deuteration Processes of Large, Astronomically Relevant Cationic Polycyclic Aromatic Hydrocarbons. In interstellar environments, gas-phase polycyclic aromatic hydrocarbon (PAH) predominantly involves (photo)fragmentation, hydrogenation, and oxidation chemical routes, which lead to the formation of complex organic species. Here the gas-phase reactions between tribenzo-naphtho-pero-pyrene (TNPP, C40H18) cations and ultraviolet, 18/16O or D atoms are investigated. The oxidized TNPP cations ([C40H18/17/16On]+, n = [1, 6]) are newly formed; the collision-induced deoxidation of oxidized TNPP cations is followed by the loss of HCO/CO units. With laser irradiation, the photo-deoxidation of oxidized TNPP cations is identified. Smaller PAH cations, [C40‑nH18‑n]+, with n = [1, 5], i.e., PAHs containing odd carbon numbers (e.g., 39, 37 C atoms), are produced. Furthermore, the oxidized–deuterated TNPP cations ([C40HmDnOx]+) are well formed upon simultaneous reaction with O and D atoms. The structure of the oxidized–deuterated TNPP cations and the bonding energy for these reaction pathways were investigated with theoretical calculations. Four oxidation bonding types are identified together with their evolution pathways. The reaction energy is relatively high, and the addition of O/D atoms to the carbon skeleton is a relatively random and independent event, i.e., with no restrictions or requirements for the carbon sites of PAH species. Consequently, the oxidized–deuterated states and forms of PAH compounds are intricate and complex. Furthermore, the calculations confirm that the loss of CO or H+CO is energetically preferable. Importantly, the formation of the carbonyl unit is confirmed. We infer that the collision/photo-induced deoxidation (loss of (H)CO units) of oxidized PAH species is involved in the top-down evolution routes of large PAHs and effectively catalyzes the potential formation of small oxygen-containing species (e.g., OH/HCO/CO) in the interstellar medium.

Keywords: Interstellar molecules, Polycyclic aromatic hydrocarbons, Laboratory astrophysics, Astrochemistry, Interstellar medium
Magnetic Activities of AD Leonis: Flares in TESS Data and Optical Spectra. We studied the flaring activities of M4.5 dwarf AD Leo to understand its stellar atmospheres and magnetic activities. We present new observational results on this highly active star, using nonsimultaneous measurement of Transiting Exoplanet Survey Satellite (TESS) data, time-series optical spectra, and Giant Meter Radio Telescope 325 MHz radio data. We revisited the rotation period of 2.23 ± 0.04 days from TESS, which matches well with previously measured literature values. We estimated an extremely rare high-energy superflare of 4.9 × 1035 erg and ∼400 minute duration with a high magnetic field strength of 1.2 kG. Interestingly, we correlated the duration of a flare event with its energy, τ ∝  , and noticed a discrepancy between stellar and solar flares suggesting a difference in coronal magnetic field strength. From time-series spectra, we observed Hα spectral flares in the range of 1030–1031 erg. A 12 minute delay in a spectral flare event was observed between the emission of the Hα and Ca II H and K lines, possibly due to their origination at different spatial locations in the chromosphere. We noticed the deviation in flare rate distribution and orbital phases indicates the presence of highly active regions. Furthermore, an occasional radio detection with a flux density of 9.46 ± 1.63 mJy at a frequency of 325 MHz might be coherent emission in the presence of the magnetic field, giving a hint of star–planet interaction.

Keywords: M dwarf stars, Starspots, Stellar flares, Magnetic fields, Habitable planets
The Fallibility of Equipartition Magnetic Field Strengths from Synchrotron Emission Using Synthetically Observed Galaxies. Understanding the role that magnetic fields play on the stage of galaxy formation requires accurate methods for inferring the properties of extragalactic magnetic fields. Radio synchrotron emission has been the most promising avenue to infer magnetic field strengths across galaxies, with the application of a central assumption: that galactic cosmic rays are in energy equipartition with the magnetic field. In this work, we leverage flexible synthetic observations of a high-resolution magnetohydrodynamic simulation of a Milky Way–like galaxy to review whether true equipartition is capable of reproducing radio observations of galaxies, and investigate its impact on the inference of magnetic field strengths when varying the properties and density distribution of the cosmic rays. We find that imposing equipartition (regardless of scale length) results in cosmic ray electron densities that are unable to generate either the amplitude or the shape of the radio intensity profiles typically observed in spiral galaxies. Instead, observationally motivated smooth distributions of cosmic ray electrons across the galaxy provide a remarkable match to observations. We further demonstrate that assuming equipartition with those mock observations can lead to significant overestimation of the magnetic field strength. This misestimation varies with cosmic ray electron densities, cosmic ray spectrum power-law index, and galactic environment, aggravated in inter-arm regions and attenuated in star-forming regions. Our results promote caution when assuming equipartition in observations, and suggest that additional theoretical and numerical work is required to leverage the upcoming generation of radio observations poised to revolutionize our understanding of astrophysical magnetic fields.

Keywords: Disk galaxies, Spiral galaxies, Magnetohydrodynamical simulations, Cosmic rays, Astrophysical magnetism, Radio continuum emission, Astronomical simulations, Extragalactic magnetic fields
The Impact of Extended CO<SUB>2</SUB> Cross Sections on Temperate Anoxic Planet Atmospheres. Our interpretation of terrestrial exoplanet atmospheric spectra will always be limited by the accuracy of the data we use as input in our forward and retrieval models. Ultraviolet molecular absorption cross sections are one category of these essential model inputs; however, they are often poorly characterized at the longest wavelengths relevant to photodissociation. Photolysis reactions dominate the chemical kinetics of temperate terrestrial planet atmospheres. One molecule of particular importance is CO2, which is likely present in all terrestrial planet atmospheres. The photolysis of CO2 can introduce CO and O, as well as shield tropospheric water vapor from undergoing photolysis. This is important because H2O photolysis produces OH, which serves as a major reactive sink to many atmospheric trace gases. Here, we construct CO2 cross-section prescriptions at 195 K and 300 K extrapolated beyond 200 nm from measured cross sections. We compare results from the implementation of these new cross sections to the most commonly used CO2 prescriptions for temperate terrestrial planets with Archean-like atmospheres. We generally find that the observational consequences of CO2 dissociation beyond 200 nm are minimal so long as our least conservative (highest opacity) prescription can be ruled out. Moreover, implementing our recommended extended CO2 cross sections does not substantially alter previous results that show the consequential photochemical impact of extended H2O cross sections.

Keywords: Exoplanets, Planetary atmospheres, Carbon dioxide, Habitable planets, Exoplanet atmospheres
Resolving an Asteroseismic Catastrophe: Structural Diagnostics from p-mode Phase Functions off the Main Sequence. On the main sequence, the asteroseismic small frequency separation δν02 between radial and quadrupole p-modes is customarily interpreted to be a direct diagnostic of internal structure. Such an interpretation is based on a well-known integral estimator relating δν02 to a radially averaged sound-speed gradient. However, this estimator fails, catastrophically, when evaluated on structural models of red giants: their small separations must therefore be interpreted differently. We derive a single expression that both reduces to the classical estimator when applied to main-sequence stellar models and reproduces the qualitative features of the small separation for stellar models of very evolved red giants. This expression indicates that the small separations of red giants scale primarily with their global seismic properties as  , rather than being in any way sensitive to their internal structure. Departures from this asymptotic behavior, during the transition from the main-sequence to red giant regimes, have been recently reported in open-cluster Christensen–Dalsgaard (C-D) diagrams from K2 mission data. Investigating them in detail, we demonstrate that they occur when the convective envelope boundary passes a specific acoustic distance—roughly one-third of a wavelength at  —from the center of the star, at which point radial modes become maximally sensitive to the position of the boundary. The shape of the corresponding features on ϵp and C-D (or r02) diagrams may be useful in constraining the nature of convective boundary mixing in the context of undershooting beneath a convective envelope.

Keywords: Stellar convective zones, Subgiant stars, Theoretical techniques, Red giant stars, Asteroseismology
UNCOVERing the Faint End of the z ∼ 7 [O III] Luminosity Function with JWST's F410M Medium Bandpass Filter. Strong emission from doubly ionized oxygen is a beacon for some of the most intensely star-forming galaxies. JWST enables the search for this beacon in the early Universe with unprecedented sensitivity. Using UNCOVER DR1 JWST/NIRCam and Hubble Space Telescope (HST) imaging data of A2744, we identify strong (rest-frame EW &gt; 500Å) [O III]5008 emitters at z ∼ 7 based on excess F410M flux. We find N = 68 z ∼ 7 [O III] candidates, including N = 33 with deep HST coverage required to rule out lower-redshift interlopers (13.68 arcmin2 with F814W 5σ depth &gt;28 AB). Such strong emission lines can produce very red colors often misinterpreted as evidence for old, massive stellar populations, but are shown to be emission lines where we have spectra. Using this deep HST sample, we derive a new [O III] luminosity function (LF) spanning  , an order of magnitude deeper than previous z ∼ 6 studies. This LF is fit by a power law with a faint-end slope of  . Our results are consistent with the z ∼ 7 FRESCO [O III] LF across the overlapping 0.5 dex range,  . Combining both data sets, we construct an LF spanning 2 dex in luminosity, with a best-fit Schechter function:  ,  , and  erg s . There is little evolution between this LF and published [O III] LFs at 3 &lt; z &lt; 8, and no evidence of a turnover at faint luminosities. The sizes of these extreme [O III] emitters are similar to their low redshift counterparts, the Green Peas. The z ∼ 7 [O III] LF aligns with the Lyα LF at the bright end, suggesting many of these galaxies are also Lyα emitters.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution, Emission line galaxies
Three-dimensional Transport of Solids in a Protoplanetary Disk Containing a Growing Giant Planet. We present the results of combined hydrodynamic and particle tracking post-processing modeling to study the transport of small dust in a protoplanetary disk containing an embedded embryo in three dimensions. We use a suite of FARGO3D hydrodynamic simulations of disks containing a planetary embryo varying in mass up to 300 M⊕ on a fixed orbit in both high- and low-viscosity disks. We then simulate solid particles through the disk as a post-processing step using a Monte Carlo integration, allowing us to track the trajectories of individual particles as they travel throughout the disk. We find that gas advection onto the planet can carry small, well-coupled solids across the gap opened in the disk by the embedded planet for planetary masses above the pebble isolation mass. This mixing between the inner and outer disk can occur in both directions, with solids in the inner disk mixing to the outer disk as well. Additionally, in low-viscosity disks, multiple dust pile-ups in the outer disk may preserve isotopic heterogeneities, possibly providing an outermost tertiary isotopic reservoir. Throughout Jupiter's growth, the extent of mixing between isotopic reservoirs varied depending on dust size, gas turbulence, and the Jovian embryo mass.

Keywords: Meteorites, Hydrodynamical simulations, Protoplanetary disks, Solar system astronomy
Anomalous Neutral Hydrogen Column Densities in Local Interstellar Medium Clouds. Analysis of high-resolution spectra of the hydrogen and deuterium Lyα lines provides measurements of interstellar neutral hydrogen column densities N(H I) to 113 stars within 50 pc of the Sun. Plots of N(H I) versus distance through the LIC, G, Mic, and other clouds in the local interstellar medium (LISM) show very interesting properties. For the LIC and G clouds, nearly all of the observed neutral hydrogen occurs within 3 or 4 pc of the Sun with no significant additional neutral hydrogen at larger distances out to 50 pc, except for several sight lines with anomalously high N(H I). Scatter about the mean hydrogen column density in the LIC is several times larger than the measurement errors. We evaluate several possible sources of the high N(H I) sight lines. Seven sight lines with anomalously high N(H I) are aligned perpendicular to the line connecting the centers of the LIC and G clouds where the two clouds merge creating a mixed cloud region. The high N(H I) in these seven sight lines can be explained by their paths through an irregularly shaped mixed cloud region where the neutral hydrogen number density is the sum for both clouds. However, the most recent nearby supernova explosion created a shell that is seen in nearly the same direction perpendicular to the LIC/G axis and may also explain these seven high N(H I) sight lines. Other possible explanations for the high N(H I) sight lines include interstellar shocks, wakes produced by stars moving rapidly through the LISM, and regions where other clouds may overlap. *Based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS AR-09525.01A. These observations are associated with programs #12475 and #12596.

Keywords: Ultraviolet sources, Heliopause, Stellar-interstellar interactions, Heliosphere, Interstellar clouds, Warm neutral medium, Interstellar medium wind
Energy Extraction from a Black Hole by a Strongly Magnetized Thin Accretion Disk. The presence of a strong, large-scale magnetic field in an accretion flow leads to the extraction of the rotational energy of the black hole (BH) through the Blandford–Znajek (BZ) process, believed to power relativistic jets in various astrophysical sources. We study rotational energy extraction from a BH surrounded by a highly magnetized thin disk by performing a set of 3D global GRMHD simulations. We find that the saturated flux threading the BH has a weaker dependence on BH spin, compared to highly magnetized hot (geometrically thick) accretion flows. Also, we find that only a fraction (10%–70%) of the extracted BZ power is channeled into the jet, depending on the spin parameter. The remaining energy is potentially used to launch winds or contribute to the radiative output of the disk or corona. Our simulations reveal that the presence of a strong magnetic field enhances the radiative efficiency of the disk, making it more luminous than its weakly magnetized counterpart or the standard disk model. We attribute this excess luminosity primarily to the enhanced magnetic dissipation in the intra-ISCO region. Our findings have implications for understanding X-ray corona formation and BH spin measurements, and interpreting BH transient phenomena.

Keywords: Accretion, Magnetohydrodynamics, Black holes, Stellar accretion disks, Magnetic fields
COSMOS-Web: The Role of Galaxy Interactions and Disk Instabilities in Producing Starbursts at z &lt; 4. We study of the role of galaxy–galaxy interactions and disk instabilities in producing starburst activity in galaxies out to z = 4. For this, we use a sample of 387 galaxies with robust total star formation rate measurements from Herschel, gas masses from the Atacama Large Millimeter/submillimeter Array, stellar masses and redshifts from multiband photometry, and JWST/NIRCam rest-frame optical imaging. Using mass-controlled samples, we find an increased fraction of interacting galaxies in the starburst regime at all redshifts out to z = 4. This increase correlates with star formation efficiency (SFE) but not with gas fraction. However, the correlation is weak (and only significant out to z = 2), which could be explained by the short duration of SFE increase during interaction. In addition, we find that isolated disk galaxies make up a significant fraction of the starburst population. The fraction of such galaxies with star-forming clumps ("clumpy disks") is significantly increased compared to the main-sequence disk population. Furthermore, this fraction directly correlates with SFE. This is direct observational evidence for a long-term increase of SFE maintained due to disk instabilities, contributing to the majority of starburst galaxies in our sample and hence to substantial mass growth in these systems. This result could also be of importance for explaining the growth of the most massive galaxies at z &gt; 6.

Keywords: Galaxy disks, Starburst galaxies, Galaxy interactions
A Novel Survey for Young Substellar Objects with the W-band Filter. VII. Water-bearing Objects in the Core of the ρ Ophiuchi Cloud Complex. We present a study of very low mass stars and brown dwarfs in the rich star-forming core of the ρ Ophiuchi cloud complex. The selection of the sample relies on detecting the inherent water absorption characteristic in young substellar objects. Of the 22 water-bearing candidates selected, 15 have a spectral type of M6 or later. Brown dwarf candidates too faint for membership determination by Gaia have their proper motions derived by deep-infrared images spanning 6 yr. Astrometric analysis confirms 21/22 sources as members, with one identified as a contaminant. Infrared colors and the spectral energy distribution of each water-bearing candidate are used to diagnose the mass, age, and possible existence of circumstellar dust. A total of 15 sources exhibit evidence of disks in their spectral energy distributions, as late as in M8-type objects. Spectroscopy for bright candidates has confirmed one as an M8 member and verified two sources (with disks) exhibiting signatures of magnetospheric accretion.

Keywords: Accretion, Brown dwarfs, Young stellar objects, Star formation, Circumstellar disks
Relative Alpha in the Magnetohydrodynamics with Open Magnetic Field Boundary and Its Application to the Solar Eruption. An instability criterion in the magnetohydrodynamics (MHD) with the open boundary of a magnetic field is proposed in this paper. We use a series of linear force-free extrapolation fields, in which the normal part of the magnetic field is fixed, to obtain the linear fitting coefficient called relative alpha by using the cojoined value of magnetic free energy and magnetic flux at the open boundary (EfΦ2) and the square of relative magnetic helicity ( ). We calculate this coefficient of the magnetic field above active regions NOAA 8210 and NOAA 11429 obtained by the photospheric-data-driven MHD model. It is found that the fitting coefficient is a good proxy of the criterion to indicate the occurrence of instability after which the magnetic reconnection happens and causes the fast release of magnetic energy. We also applied this method to the continuous evolution of the three-dimensional magnetic field of NOAA 11158 based on the measurement of the photospheric vector magnetic field of Solar Dynamics Observatory/Helioseismic and Magnetic Imager by the nonlinear force-free extrapolation method. The calculated coefficient when the major flare happened based on the extrapolation data is very close to the expected ones, which perfectly reflects the occurrence of instability, and the difference is even less than 7%. This relative alpha is very helpful to evaluate how far it is from the instability in the MHD and quantitatively estimate the occurrence of solar eruption in the space weather forecast.

Keywords: Magnetohydrodynamics
Swift-BAT GUANO Follow-up of Gravitational-wave Triggers in the Third LIGO─Virgo─KAGRA Observing Run. We present results from a search for X-ray/gamma-ray counterparts of gravitational-wave (GW) candidates from the third observing run (O3) of the LIGO─Virgo─KAGRA network using the Swift Burst Alert Telescope (Swift-BAT). The search includes 636 GW candidates received with low latency, 86 of which have been confirmed by the offline analysis and included in the third cumulative Gravitational-Wave Transient Catalogs (GWTC-3). Targeted searches were carried out on the entire GW sample using the maximum-likelihood Non-imaging Transient Reconstruction and Temporal Search pipeline on the BAT data made available via the GUANO infrastructure. We do not detect any significant electromagnetic emission that is temporally and spatially coincident with any of the GW candidates. We report flux upper limits in the 15─350 keV band as a function of sky position for all the catalog candidates. For GW candidates where the Swift-BAT false alarm rate is less than 10−3 Hz, we compute the GW─BAT joint false alarm rate. Finally, the derived Swift-BAT upper limits are used to infer constraints on the putative electromagnetic emission associated with binary black hole mergers.

Keywords: Gamma-ray bursts, Transient detection, Gravitational waves
Unraveling the Nature of HAWC J1844─034 with Fermi-LAT Data Analysis and Multiwavelength Modeling. The extended ultra-high-energy (UHE) gamma-ray source HAWC J1844─034 is closely associated with two other sources, HAWC J1843─032 and HWC J1846─025. Moreover, other gamma-ray observatories like HESS, LHAASO, and Tibet ASγ have detected UHE gamma-ray sources whose spatial positions coincide with the position of HAWC J1844─034. The UHE gamma-ray data from several observatories aid analysis of the spectral features of this source in detail at teraelectronvolt energies. Of the four pulsars near HAWC J1844─034, PSR J1844─0346 is closest to it and possibly supplies the cosmic-ray leptons to power this source. We have analyzed the Fermi─Large Area Telescope (LAT) data to explore this source's morphology and identify its spectral features in the Fermi-LAT energy band. After removing the contribution of the pulsar to the gamma-ray spectral energy distribution (SED) by pulsar-phased analysis, we obtained upper limits on the photon flux and identified the gigaelectronvolt counterpart PS J1844.2─0342 in the Fermi-LAT energy band with more than 5σ significance, which may be a pulsar wind nebula (PWN). Finally, the multiwavelength SED is modeled, assuming HAWC J1844─034 is a PWN.

Keywords: Gamma-rays, High energy astrophysics, Pulsar wind nebulae