adsabs/SciX_UAT_keywords huggingface dataset:
APPLESOSS: A Producer of ProfiLEs for SOSS. Application to the NIRISS SOSS Mode

The SOSS mode of the Near Infrared Imager and Slitless Spectrograph instrument is poised to be one of the workhorse modes for exoplanet atmosphere observations with the newly launched James Webb Space Telescope (JWST). One of the challenges of the SOSS mode, however, is the physical overlap of the first two diffraction orders of the G700XD grism on the detector. Recently, the ATOCA algorithm was developed and implemented as an option in the official JWST pipeline, as a method to extract SOSS spectra by decontaminating the detector-that is, separating the first and second orders. Here, we present A Producer of ProfiLEs for SOSS (APPLESOSS), which generates the spatial profiles for each diffraction order upon which ATOCA relies. We validate APPLESOSS using simulated SOSS time series observations of WASP-52 b, and compare it to ATOCA extractions using two other spatial profiles (a best and worst case scenario on-sky), as well as a simple box extraction performed without taking into account the order contamination. We demonstrate that APPLESOSS profiles retain a high degree of fidelity to the true underlying spatial profiles, and therefore yield accurate extracted spectra. We further confirm that the effects of the order contamination for relative measurements (e.g., exoplanet transmission or emission observations) is small-the transmission spectrum obtained from each of our four tests, including the contaminated box extraction, is consistent at the ~1σ level with the atmosphere model input into our noiseless simulations. We further confirm via a retrieval analysis that the atmosphere parameters (metallicity and C/O) obtained from each transmission spectrum are consistent with the true underlying values.

Keywords: transmission spectroscopy; exoplanets; exoplanet atmospheres; astronomy data analysis; astronomical techniques
Modeling the Transport of Nonthermal Particles in Flares Using Fokker-Planck Kinetic Theory

We describe a new approach for modeling the transport of high-energy particles accelerated during flares from the acceleration region in the solar corona until their eventual thermalization in the flare footpoint. Our technique numerically solves the Fokker-Planck equation and includes forces corresponding to Coulomb collisions in a flux loop with nonuniform ionization, synchrotron emission reaction, magnetic mirroring, and a return current electric field. Our solution to the Fokker-Planck equation includes second-order pitch angle and momentum diffusion. It is applicable to particles of arbitrary mass and charge. By tracking the collisions, we predict the bremsstrahlung produced as these particles interact with the ambient stellar atmosphere. This can be compared directly with observations and used to constrain the accelerated particle energy distribution. We have named our numerical code FP and distributed it for general use. We demonstrate its effectiveness in several test cases.

Keywords: solar flares; solar x-ray flares; solar flare spectra; stellar flares; non-thermal radiation sources; computational methods; solar magnetic fields
PHANGS-JWST First Results: Mid-infrared Emission Traces Both Gas Column Density and Heating at 100 pc Scales

We compare mid-infrared (mid-IR), extinction-corrected Hα, and CO (2-1) emission at 70-160 pc resolution in the first four PHANGS-JWST targets. We report correlation strengths, intensity ratios, and power-law fits relating emission in JWST's F770W, F1000W, F1130W, and F2100W bands to CO and Hα. At these scales, CO and Hα each correlate strongly with mid-IR emission, and these correlations are each stronger than the one relating CO to Hα emission. This reflects that mid-IR emission simultaneously acts as a dust column density tracer, leading to a good match with the molecular-gas-tracing CO, and as a heating tracer, leading to a good match with the Hα. By combining mid-IR, CO, and Hα at scales where the overall correlation between cold gas and star formation begins to break down, we are able to separate these two effects. We model the mid-IR above I ν = 0.5 MJy sr-1 at F770W, a cut designed to select regions where the molecular gas dominates the interstellar medium (ISM) mass. This bright emission can be described to first order by a model that combines a CO-tracing component and an Hα-tracing component. The best-fitting models imply that ~50% of the mid-IR flux arises from molecular gas heated by the diffuse interstellar radiation field, with the remaining ~50% associated with bright, dusty star-forming regions. We discuss differences between the F770W, F1000W, and F1130W bands and the continuum-dominated F2100W band and suggest next steps for using the mid-IR as an ISM tracer.

Keywords: disk galaxies; galaxy physics; dust continuum emission; molecular gas; infrared astronomy; millimeter astronomy; interstellar emissions; star formation
Blacklight: A General-relativistic Ray-tracing and Analysis Tool

We describe the Blacklight code, intended for postprocessing general-relativistic magnetohydrodynamic simulation data. Beyond polarized ray tracing of synchrotron radiation, it can produce a number of outputs that aid in analyzing data sets, such as maps of auxiliary quantities and false-color renderings. Additional features include support for adaptive mesh refinement input, slow-light calculations, and adaptive ray tracing. The code is written with ease of use, readability, and transparency as primary objectives, while it still achieves high performance. Blacklight is publicly available and released into the public domain.

Keywords: radiative transfer equation; general relativity; geodesics; black holes; computational methods; astronomy software; software documentation; publicly available software; public domain software
The PEPSI Exoplanet Transit Survey (PETS). II. A Deep Search for Thermal Inversion Agents in KELT-20 b/MASCARA-2 b with Emission and Transmission Spectroscopy

Recent observations have shown that the atmospheres of ultrahot Jupiters (UHJs) commonly possess temperature inversions, where the temperature increases with increasing altitude. Nonetheless, which opacity sources are responsible for the presence of these inversions remains largely observationally unconstrained. We used LBT/PEPSI to observe the atmosphere of the UHJ KELT-20 b in both transmission and emission in order to search for molecular agents which could be responsible for the temperature inversion. We validate our methodology by confirming a previous detection of Fe I in emission at 16.9σ. Our search for the inversion agents TiO, VO, FeH, and CaH results in non-detections. Using injection-recovery testing we set 4σ upper limits upon the volume mixing ratios for these constituents as low as ~1 × 10-9 for TiO. For TiO, VO, and CaH, our limits are much lower than expectations from an equilibrium chemical model, while we cannot set constraining limits on FeH with our data. We thus rule out TiO and CaH as the source of the temperature inversion in KELT-20 b, and VO only if the line lists are sufficiently accurate. *Based on data acquired with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) using the Large Binocular Telescope (LBT) in Arizona.

Keywords: exoplanet astronomy; exoplanet atmospheres; transmission spectroscopy
Fast Neutrino Cooling in the Accreting Neutron Star MXB 1659-29

Modeling of crust heating and cooling across multiple accretion outbursts of the low mass X-ray binary MXB 1659-29 indicates that the neutrino luminosity of the neutron star core is consistent with direct Urca (dUrca) reactions occurring in ~1% of the core volume. We investigate this scenario with neutron star models that include a detailed equation of state parametrized by the slope of the nuclear symmetry energy L, and a range of neutron and proton superfluid gaps. We find that the predicted neutron star mass depends sensitively on L and the assumed gaps. We discuss which combinations of superfluid gaps reproduce the inferred neutrino luminosity. Larger values of L ≳ 80 MeV require superfluidity to suppress dUrca reactions in low mass neutron stars, i.e., the proton or neutron gap is sufficiently strong and extends to high enough density. However, the largest gaps give masses near the maximum mass, making it difficult to accommodate colder neutron stars. The heat capacities of our models span the range from fully paired to fully unpaired nucleons meaning that long-term observations of core cooling could distinguish between models. As a route to solutions with a larger emitting volume, which could provide a more natural explanation for the inferred neutrino luminosity, we discuss the possibility of alternative, less efficient, fast cooling processes in exotic cores. To be consistent with the inferred neutrino luminosity, such processes must be within a factor of ~1000 of dUrca. We discuss the impact of future constraints on neutron star mass, radius, and the density dependence of the symmetry energy.

Keywords: neutron stars; neutron star cores; nuclear astrophysics; urca process
Impact of Anisotropic Cosmic-Ray Transport on the Gamma-Ray Signatures in the Galactic Center

The very high energy (VHE) emission of the central molecular zone (CMZ) is rarely modeled in 3D. Most approaches describe the morphology in 1D or simplify the diffusion to the isotropic case. In this work, we show the impact of a realistic 3D magnetic field configuration and gas distribution on the VHE γ-ray distribution of the CMZ. We solve the 3D cosmic-ray transport equation with an anisotropic diffusion tensor using the approach of stochastic differential equations as implemented in the CRPropa framework. We test two different source distributions for five different anisotropies of the diffusion tensor, covering the range of effectively fieldline-parallel diffusion to isotropic diffusion. Within the tested magnetic field configuration, the anisotropy of the diffusion tensor is close to the isotropic case, and three point sources within the CMZ are favored. Future missions such as the upcoming CTA will reveal more small-scale structures that are not yet included in the model. Therefore, a more detailed 3D gas distribution and magnetic field structure will be needed.

Keywords: galactic cosmic rays; galactic center; gamma-rays
The Isotopic Abundances of Galactic Cosmic Rays with Atomic Number 29 ≤ Z ≤ 38

The Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer spacecraft has been operating successfully in a halo orbit about the L1 Lagrange point since late 1997. We report here the isotopic composition of the Galactic cosmic ray (GCR) elements with 29 ≤ Z ≤ 38 derived from more than 20 years of CRIS data. Using a model of cosmic-ray transport in the Galaxy and the solar system (SS), we have derived from these observations the isotopic composition of the accelerated material at the GCR source (GCRS). Comparison of the isotopic fractions of these elements in the GCRS with corresponding fractions in the solar system gives no indication of GCRS enrichment in r-process isotopes. Since a large fraction of core-collapse supernovae (CCSNe) occur in OB associations, the fact that GCRs do not contain enhanced abundances of r-process nuclides indicates that CCSNe are not the principal source of lighter (Z ≤ 38) r-process nuclides in the solar system. This conclusion supports recent work that points to binary neutron-star mergers, rather than supernovae, as the principal source of galactic r-process isotopes.

Keywords: particle astrophysics; galactic cosmic rays; interstellar medium
Relativistic X-Ray Jets from the Black Hole X-Ray Binary MAXI J1820+070

The black hole MAXI J1820+070 was discovered during its 2018 outburst and was extensively monitored across the electromagnetic spectrum. Following the detection of relativistic radio jets, we obtained four Chandra X-ray observations taken between 2018 November and 2019 June, along with radio observations conducted with the Very Large Array and MeerKAT arrays. We report the discovery of X-ray sources associated with the radio jets moving at relativistic velocities with a possible deceleration at late times. The broadband spectra of the jets are consistent with synchrotron radiation from particles accelerated up to very high energies (>10 TeV) by shocks produced by the jets interacting with the interstellar medium. The minimal internal energy estimated from the X-ray observations for the jets is ∼1041 erg, significantly larger than the energy calculated from the radio flare alone, suggesting most of the energy is possibly not radiated at small scales but released through late-time interactions.

Keywords: x-ray binary stars; relativistic jets; accretion; radio jets; galactic radio sources; stellar mass black holes
Star Formation Occurs in Dense Gas, but What Does "Dense" Mean?

We report results of a project to map HCN and ${\mathrm{HCO}}^{+}$ $J=1\to 0$ emission toward a sample of molecular clouds in the inner Galaxy, all containing dense clumps that are actively engaged in star formation. We compare these two molecular line tracers with millimeter continuum emission and extinction, as inferred from 13CO, as tracers of dense gas in molecular clouds. The fraction of the line luminosity from each tracer that comes from the dense gas, as measured by ${A}_{{\rm{V}}}\gt 8$ mag, varies substantially from cloud to cloud. In all cases, a substantial fraction (in most cases, the majority) of the total luminosity arises in gas below the ${A}_{{\rm{V}}}\gt 8$ mag threshold and outside the region of strong millimeter continuum emission. Measurements of $L(\mathrm{HCN})$ toward other galaxies will likely be dominated by such gas at lower surface densities. Substantial, even dominant, contributions to the total line luminosity can arise in gas with densities typical of the cloud as a whole (n ∼ 100 cm-3). Defining the dense clump from the HCN or ${\mathrm{HCO}}^{+}$ emission itself, similarly to previous studies, leads to a wide range of clump properties, with some being considerably larger and less dense than in previous studies. HCN and ${\mathrm{HCO}}^{+}$ have a similar ability to trace dense gas for the clouds in this sample. For the two clouds with low virial parameters, 13CO is definitely a worse tracer of the dense gas, but for the other four, it is equally good (or bad) at tracing dense gas.

Keywords: interstellar medium; molecular clouds; star formation
The Sensitivity of GPz Estimates of Photo-z Posterior PDFs to Realistically Complex Training Set Imperfections

The accurate estimation of photometric redshifts is crucial to many upcoming galaxy surveys, for example, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Almost all Rubin extragalactic and cosmological science requires accurate and precise calculation of photometric redshifts; many diverse approaches to this problem are currently in the process of being developed, validated, and tested. In this work, we use the photometric redshift code GPz to examine two realistically complex training set imperfections scenarios for machine learning based photometric redshift calculation: (i) where the spectroscopic training set has a very different distribution in color-magnitude space to the test set, and (ii) where the effect of emission line confusion causes a fraction of the training spectroscopic sample to not have the true redshift. By evaluating the sensitivity of GPz to a range of increasingly severe imperfections, with a range of metrics (both of photo-z point estimates as well as posterior probability distribution functions, PDFs), we quantify the degree to which predictions get worse with higher degrees of degradation. In particular, we find that there is a substantial drop-off in photo-z quality when line-confusion goes above ~1%, and sample incompleteness below a redshift of 1.5, for an experimental setup using data from the Buzzard Flock synthetic sky catalogs.

Keywords: astrostatistics; astrostatistics techniques; photometry; redshift surveys
Observational Signature of Tightly Wound Spirals Driven by Buoyancy Resonances in Protoplanetary Disks

Besides the spirals induced by the Lindblad resonances, planets can generate a family of tightly wound spirals through buoyancy resonances. The excitation of buoyancy resonances depends on the thermal relaxation timescale of the gas. By computing timescales of various processes associated with thermal relaxation, namely, radiation, diffusion, and gas-dust collision, we show that the thermal relaxation in protoplanetary disks' surface layers (Z/R ≳ 0.1) and outer disks (R ≳ 100 au) is limited by infrequent gas-dust collisions. The use of the isothermal equation of state or rapid cooling, common in protoplanetary disk simulations, is therefore not justified. Using three-dimensional hydrodynamic simulations, we show that the collision-limited slow thermal relaxation provides favorable conditions for buoyancy resonances to develop. Buoyancy resonances produce predominantly vertical motions, whose magnitude at the 12CO emission surface is of the order of 100 m s-1 for Jovian-mass planets, sufficiently large to detect using molecular line observations with ALMA. We generate synthetic observations and describe characteristic features of buoyancy resonances in Keplerian-subtracted moment maps and velocity channel maps. Based on the morphology and magnitude of the perturbation, we propose that the tightly wound spirals observed in TW Hya could be driven by a (sub-)Jovian-mass planet at 90 au. We discuss how non-Keplerian motions driven by buoyancy resonances can be distinguished from those driven by other origins. We argue that observations of multiple lines tracing different heights, with sufficiently high spatial/spectral resolution and sensitivity to separate the emission arising from the near and far sides of the disk, will help constrain the origin of non-Keplerian motions.

Keywords: protoplanetary disks; spiral arms; hydrodynamical simulations; submillimeter astronomy
Astrometric Accelerations as Dynamical Beacons: Discovery and Characterization of HIP 21152 B, the First T-dwarf Companion in the Hyades

Benchmark brown dwarf companions with well-determined ages and model-independent masses are powerful tools to test substellar evolutionary models and probe the formation of giant planets and brown dwarfs. Here, we report the independent discovery of HIP 21152 B, the first imaged brown dwarf companion in the Hyades, and conduct a comprehensive orbital and atmospheric characterization of the system. HIP 21152 was targeted in an ongoing high-contrast imaging campaign of stars exhibiting proper-motion changes between Hipparcos and Gaia, and was also recently identified by Bonavita et al. (2022) and Kuzuhara et al. (2022). Our Keck/NIRC2 and SCExAO/CHARIS imaging of HIP 21152 revealed a comoving companion at a separation of 0.″37 (16 au). We perform a joint orbit fit of all available relative astrometry and radial velocities together with the Hipparcos-Gaia proper motions, yielding a dynamical mass of ${24}_{-4}^{+6}\,{M}_{\mathrm{Jup}}$ , which is 1-2σ lower than evolutionary model predictions. Hybrid grids that include the evolution of cloud properties best reproduce the dynamical mass. We also identify a comoving wide-separation (1837″ or 7.9 × 104 au) early-L dwarf with an inferred mass near the hydrogen-burning limit. Finally, we analyze the spectra and photometry of HIP 21152 B using the Saumon & Marley (2008) atmospheric models and a suite of retrievals. The best-fit grid-based models have f sed = 2, indicating the presence of clouds, T eff = 1400 K, and $\mathrm{log}g=4.5\,\mathrm{dex}$ . These results are consistent with the object's spectral type of T0 ± 1. As the first benchmark brown dwarf companion in the Hyades, HIP 21152 B joins the small but growing number of substellar companions with well-determined ages and dynamical masses. *Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: brown dwarfs; direct imaging; t dwarfs; astrometry; orbit determination; atmospheric clouds
4-8 GHz Spectrotemporal Emission from the Galactic Center Magnetar PSR J1745-2900

Radio magnetars are exotic sources noted for their diverse spectrotemporal phenomenology and pulse profile variations over weeks to months. Unusual for radio magnetars, the Galactic Center (GC) magnetar PSR J1745-2900 has been continually active since its discovery in 2013. We monitored the GC magnetar at 4-8 GHz for 6 hr in 2019 August-September using the Robert C. Byrd Green Bank Telescope. During our observations, the GC magnetar emitted a flat fluence spectrum over 5-8 GHz to within 2σ uncertainty. From our data, we estimate a 6.4 GHz period-averaged flux density, ${\overline{S}}_{6.4}\approx (240\pm 5)$ μJy. Tracking the temporal evolution of ${\overline{S}}_{6.4}$ , we infer a gradual weakening of GC magnetar activity during 2016-2019 relative to that between 2013 and 2015.5. Typical single pulses detected in our study reveal marginally resolved subpulses with opposing spectral indices, a feature characteristic of radio magnetars but unseen in rotation-powered pulsars. However, unlike in fast radio bursts, these subpulses exhibit no perceptible radio frequency drifts. Throughout our observing span, ≃5 ms scattered pulses significantly jitter within two stable emission components of widths 220 ms and 140 ms, respectively, in the average pulse profile.

Keywords: galactic center; magnetars; neutron stars; radio transient sources
From Neutrino- to Photon-cooled in Three Years: Can Fallback Accretion Explain the X-Ray Excess in GW170817?

Excess X-ray emission from the neutron star merger GW170817 above the predicted afterglow was recently detected t ≈ 3.4 yr post-merger. One possible origin is accretion onto the newly unshrouded black hole (BH) remnant. While fallback of bound dynamical ejecta is insufficient to generate the excess luminosity, LX ~ 5 × 1038 erg s-1, fallback from the disk wind ejecta-due to their larger mass and lower velocity-remains a possibility. We present hydrodynamic α-viscosity simulations of the post-merger disk evolution that extend to timescales t ≈ 35 s post-merger, necessary to capture the asymptotic evolution into the radiatively inefficient regime. Due to inefficient neutrino cooling, the BH accretion rate decays rapidly at late times (${\dot{M}}_{\mathrm{bh}}\propto {t}^{-{\beta }_{\mathrm{bh}}}$, where βbh ≈ 2.4-2.8), which is incompatible with the late-time excess. However, matter falls back to the inner disk from the equatorial region more gradually, ${\dot{M}}_{\mathrm{fb}}\propto {t}^{-{\beta }_{\mathrm{fb}}}$ with βfb ≈ 1.43 in our α ≈ 0.03 simulations. By the present epoch t ≈ 3.4 yr, the fallback rate has become sub-Eddington and the disk can again accrete efficiently, i.e., ${\dot{M}}_{\mathrm{bh}}\approx {\dot{M}}_{\mathrm{fb}}$, this time due to photon instead of neutrino cooling. The predicted present-day X-ray accretion luminosity, ${L}_{{\rm{X}}}\approx 0.1{\dot{M}}_{\mathrm{bh}}{c}^{2}\approx (2\mbox{--}70)\times {10}^{38}$ erg s-1 for βfb ≈ 1.43-1.66, thus supports (with caveats) an accretion-powered origin for the X-ray excess in GW170817. The suppressed BH accretion rate prior to the sub-Eddington transition, weeks to months after the merger, is key to avoid overproducing the kilonova luminosity via reprocessing.

Keywords: accretion; x-ray transient sources; neutron stars; compact radiation sources