adsabs/SciX_UAT_keywords huggingface dataset:
An ACA Survey of [C I] 3P1-3P0, CO J = 4 - 3, and Dust Continuum in Nearby U/LIRGs

We present the results of surveying [C I] 3P1-3P0, 12CO J = 4 - 3, and 630 μm dust continuum emission for 36 nearby ultra/luminous infrared galaxies (U/LIRGs) using the Band 8 receiver mounted on the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array. We describe the survey, observations, data reduction, and results; the main results are as follows. (i) We confirmed that [C I] 3P1-3P0 has a linear relationship with both the 12CO J = 4 - 3 and 630 μm continuum. (ii) In NGC 6052 and NGC 7679, 12CO J = 4 - 3 was detected but [C I] 3P1-3P0 was not detected with a [C I] 3P1-3P0/12CO J = 4 - 3 ratio of ≲0.08. Two possible scenarios of weak [C I] 3P1-3P0 emission are C0-poor/CO-rich environments and an environment with an extremely large [C I] 3P1-3P0 missing flux. (iii) There is no clear evidence showing that galaxy mergers, AGNs, and dust temperatures control the ratios of [C I] 3P1-3P0/12CO J = 4 - 3 and ${L}_{[{\rm{C}}\,{\rm\small{I}}](1-0)}^{{\prime} }/{L}_{630\mu {\rm{m}}}$ . (iv) We compare our nearby U/LIRGs with high-z galaxies, such as galaxies on the star formation main sequence (MS) at z ~ 1 and submillimeter galaxies (SMGs) at z = 2-4. We found that the mean value for the [C I] 3P1-3P0/12CO J = 4 - 3 ratio of U/LIRGs is similar to that of SMGs but smaller than that of galaxies on the MS.

Keywords: galaxy evolution; extragalactic astronomy; submillimeter astronomy; starburst galaxies; luminous infrared galaxies; ultraluminous infrared galaxies; galaxy collisions; interstellar medium; interstellar line emission; co line emission
A Broadband X-Ray View of the Precessing Accretion Disk and Pre-eclipse Dip in the Pulsar Her X-1 with NuSTAR and XMM-Newton

We present a broadband X-ray timing study of the variations in pulse behavior with the superorbital cycle in the low-mass X-ray binary Her X-1. This source shows a 35 day superorbital modulation in X-ray flux that is likely caused by occultation by a warped, precessing accretion disk. Our data set consists of four joint XMM-Newton and NuSTAR observations of Her X-1 which sample a complete superorbital cycle. We focus our analysis on the first and fourth observations, which occur during the bright "main-on" phase, because these observations have strongly detected pulsations. We added an archival XMM-Newton observation during the "short-on" phase of the superorbital cycle because our observations at that phase are lower in signal to noise. We find that the energy-resolved pulse profiles show the same shape at similar superorbital phases, and the profiles are consistent with expectations from a precessing disk. We demonstrate that a simple precessing accretion disk model is sufficient to reproduce the observed pulse profiles. The results of this model suggest that the similarities in the observed pulse profiles are due to reprocessing by a precessing disk that has returned to its original precession phase. We determine that the broadband spectrum is well fit by an absorbed power law with a soft blackbody component and show that the spectral continuum also exhibits a dependence on the superorbital cycle. We also present a brief analysis of the energy-resolved light curves of a pre-eclipse dip, which shows soft X-ray absorption and hard X-ray variability during the dip.

Keywords: pulsars; low-mass x-ray binary stars
Subarcminute Localization of 13 Repeating Fast Radio Bursts Detected by CHIME/FRB

We report on improved sky localizations of 13 repeating fast radio bursts (FRBs) discovered by CHIME/FRB via the use of interferometric techniques on channelized voltages from the telescope. These so-called "baseband localizations" improve the localization uncertainty area presented in past studies by more than three orders of magnitude. The improved localization regions are provided for the full sample of FRBs to enable follow-up studies. The localization uncertainties, together with the limits on the source distances from their dispersion measures, allow us to identify likely host galaxies for two of the FRB sources. FRB 20180814A lives in a massive passive red spiral at z ~ 0.068 with very little indication of star formation, while FRB 20190303A resides in a merging pair of spiral galaxies at z ~ 0.064 undergoing significant star formation. These galaxies show very different characteristics, further confirming the presence of FRB progenitors in a variety of environments even among the repeating subclass.

Keywords: radio transient sources
HAWC Search for High-mass Microquasars

Microquasars with high-mass companion stars are promising very high energy (VHE; 0.1-100 TeV) gamma-ray emitters, but their behaviors above 10 TeV are poorly known. Using the High Altitude Water Cerenkov (HAWC) observatory, we search for excess gamma-ray emission coincident with the positions of known high-mass microquasars (HMMQs). No significant emission is observed for LS 5039, Cyg X-1, Cyg X-3, and SS 433 with 1523 days of HAWC data. We set the most stringent limit above 10 TeV obtained to date on each individual source. Under the assumption that HMMQs produce gamma rays via a common mechanism, we have performed source-stacking searches, considering two different scenarios: (I) gamma-ray luminosity is a fraction ϵγ of the microquasar jet luminosity, and (II) VHE gamma rays are produced by relativistic electrons upscattering the radiation field of the companion star in a magnetic field B. We obtain ϵγ < 5.4 × 10-6 for scenario I, which tightly constrains models that suggest observable high-energy neutrino emission by HMMQs. In the case of scenario II, the nondetection of VHE gamma rays yields a strong magnetic field, which challenges synchrotron radiation as the dominant mechanism of the microquasar emission between 10 keV and 10 MeV.

Keywords: gamma-ray sources; high mass x-ray binary stars
Aluminum-26 Enrichment in the Surface of Protostellar Disks Due to Protostellar Cosmic Rays

The radioactive decay of aluminum-26 (26Al) is an important heating source in early planet formation. Since its discovery, there have been several mechanisms proposed to introduce 26Al into protoplanetary disks, primarily through contamination by external sources. We propose a local mechanism to enrich protostellar disks with 26Al through irradiation of the protostellar disk surface by cosmic rays accelerated in the protostellar accretion shock. We calculate the 26Al enrichment, [26Al/27Al ], at the surface of the protostellar disk in the inner au throughout the evolution of low-mass stars, from M-dwarfs to proto-Suns. Assuming constant mass accretion rates, $\dot{m}$ , we find that irradiation by MeV cosmic rays can provide significant enrichment on the disk surface if the cosmic rays are not completely coupled to the gas in the accretion flow. Importantly, we find that low accretion rates, $\dot{m}\lt {10}^{-7}$ M⊙ yr-1, are able to produce canonical amounts of 26Al, ${[}^{26}\mathrm{Al}{/}^{27}\mathrm{Al}]\approx 5\times {10}^{-5}$ . These accretion rates are experienced at the transition from Class I- to Class II-type protostars, when it is assumed that calcium-aluminum-rich inclusions condense in the inner disk. We conclude that irradiation of the inner disk surface by cosmic-ray protons accelerated in accretion shocks at the protostellar surface may be an important mechanism to produce 26Al. Our models show protostellar cosmic rays may be a viable model to explain the enrichment of 26Al found in the solar system.

Keywords: protostars; protoplanetary disks; cosmic rays; interstellar medium; star formation; nuclear abundances; cosmic ray nucleosynthesis; meteorite composition; chondrites
Twenty Years of SpeX: Accuracy Limits of Spectral Slope Measurements in Asteroid Spectroscopy

We examined two decades of SpeX/NASA Infrared Telescope Facility observations from the Small Main-Belt Asteroid Spectroscopic Survey (SMASS) and the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) to investigate uncertainties and systematic errors in reflectance spectral slope measurements of asteroids. From 628 spectra of 11 solar analogs used for calibration of the asteroid spectra, we derived an uncertainty of on slope measurements over 0.8-2.4 μm. Air mass contributes to -0.92% μm-1 per 0.1 unit air mass difference between the asteroid and the solar analog and therefore for an overall 2.8% μm-1 slope variability in SMASS and MITHNEOS designed to operate within 1.0-1.3 air mass. No additional observing conditions (including the parallactic angle, seeing, and humidity) were found to contribute systematically to slope change. We discuss implications for asteroid taxonomic classification works. Uncertainties provided in this study should be accounted for in future compositional investigation of small bodies to distinguish intrinsic heterogeneities from possible instrumental effects.

Keywords: spectroscopy; main belt asteroids; near-earth objects; small solar system bodies; astronomical instrumentation
Direct In Situ Measurements of a Fast Coronal Mass Ejection and Associated Structures in the Corona

We report on the first direct in situ measurements of a fast coronal mass ejection (CME) and shock in the corona, which occurred on 2022 September 5. In situ measurements from the Parker Solar Probe spacecraft near perihelion suggest two shocks, with the second one decayed, which is consistent with more than one eruption in coronagraph images. Despite a flank crossing, the measurements indicate unique features of the young ejecta: a plasma much hotter than the ambient medium, suggestive of a hot solar source, and a large plasma β implying a highly non-force-free state and the importance of thermal pressure gradient for CME acceleration and expansion. Reconstruction of the global coronal magnetic fields shows a long-duration change in the heliospheric current sheet (HCS), and the observed field polarity reversals agree with a more warped HCS configuration. Reconnection signatures are observed inside an HCS crossing as deep as the sonic critical point. As the reconnection occurs in the sub-Alfvénic wind, the reconnected flux sunward of the reconnection site can close back to the Sun, which helps balance magnetic flux in the heliosphere. The nature of the sub-Alfvénic wind after the HCS crossing as a low Mach-number boundary layer (LMBL) leads to in situ measurements of the near subsonic plasma at a surprisingly large distance. Specifically, an LMBL may provide favorable conditions for the crossings of the sonic critical point in addition to the Alfvén surface.

Keywords: solar wind; solar coronal mass ejections; shocks; solar magnetic reconnection; solar corona
Turbulent Cascade and Energy Transfer Rate in a Solar Coronal Mass Ejection

Turbulence properties are examined before, during, and after a coronal mass ejection (CME) detected by the Wind spacecraft in 2012 July. The power-law scaling of the structure functions, providing information on the power spectral density and flatness of the velocity, magnetic field, and density fluctuations, were examined. The third-order moment scaling law for incompressible, isotropic magnetohydrodynamic turbulence was observed in the preceding and trailing solar wind, as well as in the CME sheath and magnetic cloud. This suggests that the turbulence could develop sufficiently after the shock, or that turbulence in the sheath and cloud regions was robustly preserved even during the mixing with the solar wind plasma. The turbulent energy transfer rate was thus evaluated in each of the regions. The CME sheath shows an increase of energy transfer rate, as expected from the lower level of Alfvénic fluctuations and suggesting the role of the shock-wind interaction as an additional source of energy for the turbulent cascade.

Keywords: solar coronal mass ejections; interplanetary turbulence; solar wind
The Solar Wind Angular Momentum Flux as Observed by Parker Solar Probe

The long-term evolution of the Sun's rotation period cannot be directly observed, and is instead inferred from trends in the measured rotation periods of other Sun-like stars. Assuming the Sun spins down as it ages, following rotation rate ∝ age-1/2, requires the current solar angular momentum (AM) loss rate to be around 6 × 1030 erg. Magnetohydrodynamic models, and previous observations of the solar wind (from the Helios and Wind spacecraft), generally predict a values closer to 1 × 1030 erg or 3 × 1030 erg, respectively. Recently, the Parker Solar Probe (PSP) observed tangential solar wind speeds as high as ∼50 km s-1 in a localized region of the inner heliosphere. If such rotational flows were prevalent throughout the corona, it would imply that the solar wind AM-loss rate is an order of magnitude larger than all of those previous estimations. In this Letter, we evaluate the AM flux in the solar wind, using data from the first two orbits of PSP. The solar wind is observed to contain both large positive (as seen during perihelion), and negative AM fluxes. We analyze two solar wind streams that were repeatedly traversed by PSP; the first is a slow wind stream whose average AM flux fluctuates between positive and negative values, and the second is an intermediate speed stream that contains a positive AM flux (more consistent with a constant flow of AM). When the data from PSP are evaluated holistically, the average equatorial AM flux implies a global AM-loss rate of around (2.6-4.2) × 1030 erg (which is more consistent with observations from previous spacecraft).

Keywords: solar wind; stellar rotation; solar rotation; solar evolution; stellar evolution; stellar physics; solar physics
Search for Ultra-high-energy Photons from Gravitational Wave Sources with the Pierre Auger Observatory

A search for time-directional coincidences of ultra-high-energy (UHE) photons above 10 EeV with gravitational wave (GW) events from the LIGO/Virgo runs O1 to O3 is conducted with the Pierre Auger Observatory. Due to the distinctive properties of photon interactions and to the background expected from hadronic showers, a subset of the most interesting GW events is selected based on their localization quality and distance. Time periods of 1000 s around and 1 day after the GW events are analyzed. No coincidences are observed. Upper limits on the UHE photon fluence from a GW event are derived that are typically at ~7 MeV cm-2 (time period 1000 s) and ~35 MeV cm-2 (time period 1 day). Due to the proximity of the binary neutron star merger GW170817, the energy of the source transferred into UHE photons above 40 EeV is constrained to be less than 20% of its total GW energy. These are the first limits on UHE photons from GW sources.

Keywords: particle astrophysics; ultra-high-energy cosmic radiation; cosmic ray showers; gravitational wave sources; transient sources
Testing the Collisionless Nature of Dark Matter with the Radial Acceleration Relation in Galaxy Clusters

The radial acceleration relation (RAR) represents a tight empirical relation between the inferred total and baryonic centripetal accelerations, g tot = GM tot(< r)/r 2 and g bar = GM bar(< r)/r 2, observed in galaxies and galaxy clusters. The tight correlation between these two quantities can provide insight into the nature of dark matter. Here we use BAHAMAS, a state-of-the-art suite of cosmological hydrodynamical simulations, to characterize the RAR in cluster-scale halos for both cold and collisionless dark matter (CDM) and self-interacting dark matter (SIDM) models. SIDM halos generally have reduced central dark matter densities, which reduces the total acceleration in the central region when compared with CDM. We compare the RARs in galaxy clusters simulated with different dark matter models to the RAR inferred from CLASH observations. Our comparison shows that the cluster-scale RAR in the CDM model provides an excellent match to the CLASH RAR obtained by Tian et al. including the high-acceleration regime probed by the brightest cluster galaxies (BCGs). By contrast, models with a larger SIDM cross section yield increasingly poorer matches to the CLASH RAR. Excluding the BCG regions results in a weaker but still competitive constraint on the SIDM cross section. Using the RAR data outside the central r < 100 kpc region, an SIDM model with σ/m = 0.3 cm2 g-1 is disfavored at the 3.8σ level with respect to the CDM model. This study demonstrates the power of the cluster-scale RAR for testing the collisionless nature of dark matter.

Keywords: dark matter; galaxy clusters; gravitational lensing; cosmology; intracluster medium
Stellar Winds Pump the Heart of the Milky Way

The central supermassive black hole of the Milky Way, Sgr A*, accretes at a very low rate making it a very underluminous galactic nucleus. Despite the tens of Wolf-Rayet stars present within the inner parsec supplying ∼10-3 M ⊙ yr-1 in stellar winds, only a negligible fraction of this material (<10-4) ends up being accreted onto Sgr A*. The recent discovery of cold gas (∼104 K) in its vicinity raised questions about how such material could settle in the hostile (∼107 K) environment near Sgr A*. In this work we show that the system of mass-losing stars blowing winds can naturally account for both the hot, inefficient accretion flow, as well as the formation of a cold disk-like structure. We run hydrodynamical simulations using the grid-based code RAMSES starting as early in the past as possible to observe the state of the system at the present time. Our results show that the system reaches a quasi-steady state in about ∼500 yr with material being captured at a rate of ∼10-6 M ⊙ yr-1 at scales of ∼10-4 pc, consistent with the observations and previous models. However, on longer timescales (≳3000 yr) the material accumulates close to the black hole in the form of a disk. Considering the duration of the Wolf-Rayet phase (∼105 yr), we conclude that this scenario has likely already happened, and could be responsible for the more active past of Sgr A*, and/or its current outflow. We argue that the hypothesis of the mass-losing stars being the main regulator of the activity of the black hole deserves further consideration.

Keywords: galactic center; hydrodynamics; stellar winds; accretion
Empirically Determining Substellar Cloud Compositions in the Era of the James Webb Space Telescope

Most brown dwarfs have atmospheres with temperatures cold enough to form clouds. A variety of materials likely condense, including refractory metal oxides and silicates; the precise compositions and crystal structures of predicted cloud particles depend on the modeling framework used and have not yet been empirically constrained. Spitzer has shown tentative evidence of the silicate feature in L dwarf spectra and the James Webb Space Telescope (JWST) can measure these features in many L dwarfs. Here, we present new models to predict the signatures of the strongest cloud absorption features. We investigate different cloud mineral species and determine how particle size, mineralogy, and crystalline structure change spectral features. We find that silicate and refractory clouds have a strong cloud absorption feature for small particle sizes (≤1 μm). Model spectra are compared to five brown dwarfs that show evidence of the silicate feature; models that include small particles in the upper layers of the atmosphere produce a broad cloud mineral feature, and that better match the observed spectra than the Ackerman & Marley cloud model. We simulate observations with the Mid-Infrared Instrument (MIRI) instrument on JWST for a range of nearby, cloudy brown dwarfs, demonstrating that these features could be readily detectable if small particles are present. Furthermore, for photometrically variable brown dwarfs, our predictions suggest that with JWST, by measuring spectroscopic variability inside and outside a mineral feature, we can establish silicate (or other) clouds as the cause of variability. Mid-infrared spectroscopy is a promising tool to empirically constrain the complex cloud condensation sequence in brown dwarf atmospheres.

Keywords: brown dwarfs; l dwarfs; stellar atmospheres; extrasolar gaseous giant planets; exoplanet atmospheres
Exploring the Ability of Hubble Space Telescope WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres through a Homogeneous Transmission Survey of 70 Gaseous Planets

We present analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble's Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation that our retrievals attribute to molecular species. Among these, we use Bayesian hierarchical modeling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet's mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous studies have found evidence of a mass-metallicity trend, we find no such relation within our data. For the hotter planets within our sample, we find evidence for thermal dissociation of dihydrogen and water via the H- opacity. We suggest that the general lack of trends seen across this population study could be due to (i) the insufficient spectral coverage offered by the Hubble Space Telescope's WFC3 G141 band, (ii) the lack of a simple trend across the whole population, (iii) the essentially random nature of the target selection for this study, or (iv) a combination of all the above. We set out how we can learn from this vast data set going forward in an attempt to ensure comparative planetology can be undertaken in the future with facilities such as the JWST, Twinkle, and Ariel. We conclude that a wider simultaneous spectral coverage is required as well as a more structured approach to target selection.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; bayesian statistics; surveys; hubble space telescope; astronomy data reduction; exoplanets; extrasolar gaseous planets
Symphony: Cosmological Zoom-in Simulation Suites over Four Decades of Host Halo Mass

We present Symphony, a compilation of 262 cosmological, cold-dark-matter-only zoom-in simulations spanning four decades of host halo mass, from 1011-1015 M ⊙. This compilation includes three existing simulation suites at the cluster and Milky Way-mass scales, and two new suites: 39 Large Magellanic Cloud-mass (1011 M ⊙) and 49 strong-lens-analog (1013 M ⊙) group-mass hosts. Across the entire host halo mass range, the highest-resolution regions in these simulations are resolved with a dark matter particle mass of ≈3 × 10-7 times the host virial mass and a Plummer-equivalent gravitational softening length of ≈9 × 10-4 times the host virial radius, on average. We measure correlations between subhalo abundance and host concentration, formation time, and maximum subhalo mass, all of which peak at the Milky Way host halo mass scale. Subhalo abundances are ≈50% higher in clusters than in lower-mass hosts at fixed sub-to-host halo mass ratios. Subhalo radial distributions are approximately self-similar as a function of host mass and are less concentrated than hosts' underlying dark matter distributions. We compare our results to the semianalytic model GALACTICUS, which predicts subhalo mass functions with a higher normalization at the low-mass end and radial distributions that are slightly more concentrated than Symphony. We use UNIVERSEMACHINE to model halo and subhalo star formation histories in Symphony, and we demonstrate that these predictions resolve the formation histories of the halos that host nearly all currently observable satellite galaxies in the universe. To promote open use of Symphony, data products are publicly available at http://web.stanford.edu/group/gfc/symphony.

Keywords: dark matter; galaxy abundances; n-body simulations; galaxy dark matter halos; computational methods