adsabs/SciX_UAT_keywords huggingface dataset:
OSSOS Finds an Exponential Cutoff in the Size Distribution of the Cold Classical Kuiper Belt

The cold main classical Kuiper Belt consists of the nonresonant small solar system bodies with low orbital inclinations and orbital semimajor axes between 42.4 and 47.7 au. These objects likely formed in situ, and the population has experienced minimal collisional modification since formation. Using the Outer Solar System Origins Survey ensemble sample and characterization, combined with constraints from deeper surveys and supported by evidence from the Minor Planet Center catalog and the Deep Ecliptic Survey, we determine the absolute magnitude Hr distribution of the cold classical belt from Hr ≃ 5 to 12 (roughly diameters of 400-20 km). We conclude that the cold population's Hr distribution exhibits an exponential cutoff at large sizes. Exponential cutoffs at large sizes are not a natural outcome of pairwise particle accretion, but exponentially tapered power-law size distributions are a feature of numerical simulations of planetesimal formation via a streaming instability. Our observation of an exponential cutoff agrees with previous observational inferences that no large objects (D ≳ 400 km) exist in the cold population. We note that the asymptotic slope of the Hr distribution is consistent with α ~ 0.4. This asymptotic slope is also found in streaming instability modeling of planetesimal formation and is thus not necessarily associated with achieving collisional equilibrium. Studies of the trans-Neptunian region are providing the parameters that will enable future streaming-instability studies to determine the initial conditions of planetesimal formation in the ≈45 au region of the Sun's protoplanetary disk.

Keywords: classical kuiper belt objects; trans-neptunian objects; kuiper belt
The Demographics of Kepler's Earths and Super-Earths into the Habitable Zone

Understanding the occurrence of Earth-sized planets in the habitable zone of Sun-like stars is essential to the search for Earth analogs. Yet a lack of reliable Kepler detections for such planets has forced many estimates to be derived from the close-in (2 < P orb < 100 days) population, whose radii may have evolved differently under the effect of atmospheric mass-loss mechanisms. In this work, we compute the intrinsic occurrence rates of close-in super-Earths (~1-2 R ⊕) and sub-Neptunes (~2-3.5 R ⊕) for FGK stars (0.56-1.63 M ⊙) as a function of orbital period and find evidence of two regimes: where super-Earths are more abundant at short orbital periods, and where sub-Neptunes are more abundant at longer orbital periods. We fit a parametric model in five equally populated stellar mass bins and find that the orbital period of transition between these two regimes scales with stellar mass, like ${P}_{\mathrm{trans}}\propto {M}_{* }^{1.7\pm 0.2}$ . These results suggest a population of former sub-Neptunes contaminating the population of gigayear-old close-in super-Earths, indicative of a population shaped by atmospheric loss. Using our model to constrain the long-period population of intrinsically rocky planets, we estimate an occurrence rate of ${{\rm{\Gamma }}}_{\oplus }={15}_{-4}^{+6} \% $ for Earth-sized habitable zone planets, and predict that sub-Neptunes may be ~ twice as common as super-Earths in the habitable zone (when normalized over the natural log-orbital period and radius range used). Finally, we discuss our results in the context of future missions searching for habitable zone planets.

Keywords: exoplanets; habitable planets; exoplanet atmospheres; super earths; mini neptunes
The Rotation of the Nonrigid Earth at the Second Order. II. The Poincaré Model: Nonsingular Complex Canonical Variables and Poisson Terms

We develop a Hamiltonian analytical theory for the rotation of a Poincaré Earth model (rigid mantle and liquid core) at the second order with respect to the lunisolar potential and moving ecliptic term. Since the Andoyer variables considered in the first-order solution present virtual singularities, i.e., vanishing divisors, we introduce a set of nonsingular complex canonical variables. This choice allows for applying the Hori canonical perturbation method in a standard way. We derive analytical expressions for the first- and second-order solutions of the precession and nutation of the angular momentum axis (Poisson terms). Contrary to first-order theories, there is a part of the Poisson terms that does depend on the Earth's structure. The resulting numerical amplitudes, not incorporated in the International Astronomical Union nutation standard, are not negligible considering current accuracies. They are at the microarcsecond level for a few terms, with a very significant contribution in obliquity of about 40 μas for the nutation argument with period -6798.38 days. The structure-dependent amplitudes present a large amplification with respect to the rigid model due to the fluid core resonance. The features of such resonance, however, are different from those found in first-order solutions. The most prominent is that it does not depend directly on the second-order nutation argument but rather on the combination of first-order arguments generating it. It entails that some first-order approaches, like those based on the transfer function, cannot be applied to obtain the second-order contributions.

Keywords: earth (planet); ephemerides; astronomical coordinate systems; celestial mechanics
Gas and Cosmic-Ray Properties in the MBM 53, 54, and 55 Molecular Clouds and the Pegasus Loops Revealed by H I Line Profiles, Dust, and Gamma-Ray Data

In studying the interstellar medium (ISM) and Galactic cosmic rays (CRs), uncertainty of the interstellar gas density has always been an issue. To overcome this difficulty, we used a component decomposition of the 21 cm H I emission line and used the resulting gas maps in an analysis of γ-ray data obtained by the Fermi Large Area Telescope (LAT) for the MBM 53, 54, and 55 molecular clouds and the Pegasus loop. We decomposed the ISM gas into intermediate-velocity clouds, narrow-line and optically thick H I, broad-line and optically thin H I, CO-bright H2, and CO-dark H2 using detailed correlations with the H I line profiles from the HI4PI survey, the Planck dust-emission model, and the Fermi-LAT γ-ray data. We found the fractions of the optical depth correction to the H I column density and CO-dark H2 to be nearly equal. We fitted the CR spectra directly measured at/near the Earth and the measured γ-ray emissivity spectrum simultaneously. We obtained a spectral break in the interstellar proton spectrum at ~7 GeV, and found that the γ-ray emissivity normalization agrees with the AMS-02 proton spectrum within 10%, relaxing the tension with the CR spectra previously claimed.

Keywords: galactic cosmic rays; gamma-rays; interstellar medium
An Overview of CHIME, the Canadian Hydrogen Intensity Mapping Experiment

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift scan radio telescope operating across the 400-800 MHz band. CHIME is located at the Dominion Radio Astrophysical Observatory near Penticton, BC, Canada. The instrument is designed to map neutral hydrogen over the redshift range 0.8-2.5 to constrain the expansion history of the universe. This goal drives the design features of the instrument. CHIME consists of four parallel cylindrical reflectors, oriented north-south, each 100 m × 20 m and outfitted with a 256-element dual-polarization linear feed array. CHIME observes a two-degree-wide stripe covering the entire meridian at any given moment, observing three-quarters of the sky every day owing to Earth's rotation. An FX correlator utilizes field-programmable gate arrays and graphics processing units to digitize and correlate the signals, with different correlation products generated for cosmological, fast radio burst, pulsar, very long baseline interferometry, and 21 cm absorber back ends. For the cosmology back end, the ${N}_{\mathrm{feed}}^{2}$ correlation matrix is formed for 1024 frequency channels across the band every 31 ms. A data receiver system applies calibration and flagging and, for our primary cosmological data product, stacks redundant baselines and integrates for 10 s. We present an overview of the instrument, its performance metrics based on the first 3 yr of science data, and we describe the current progress in characterizing CHIME's primary beam response. We also present maps of the sky derived from CHIME data; we are using versions of these maps for a cosmological stacking analysis, as well as for investigation of Galactic foregrounds.

Keywords: cosmology; baryon acoustic oscillations; radio telescopes; astronomical instrumentation; dark energy; h i line emission; interferometric correlation; radio interferometers; telescopes
Surveying the Giant H II Regions of the Milky Way with SOFIA. II. M17

We present our second set of results from our mid-infrared imaging survey of Milky Way giant H II regions. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) to obtain 20 and 37 μm images of the central ∼10' × 10' area of M17. We investigate the small- and large-scale properties of M17 using our data in conjunction with previous multiwavelength observations. The spectral energy distributions of individual compact sources were constructed with Spitzer-IRAC, SOFIA-FORCAST, and Herschel-PACS photometry data and fitted with massive young stellar object (MYSO) models. Seven sources were found to match the criteria for being MYSO candidates, four of which are identified here for the first time, and the stellar mass of the most massive object, UC 1, is determined to be 64 M⊙. We resolve the extended mid-infrared emission from the KW object and suggest that the angle of this extended emission is influenced by outflow. It is shown that IRS 5 decreases in brightness as a function of wavelength from the mid- to far-infrared and has several other indicators that point to it being an intermediate-mass Class II object and not an MYSO. We find that the large-scale appearance of emission in M17 at 20 μm is significantly affected by contamination from the [S III] emission line from the ionized gas of the giant H II region. Finally, a number of potential evolutionary tracers yield a consistent picture suggesting that the southern bar of M17 is likely younger than the northern bar.

Keywords: h ii regions; compact h ii region; star formation; star forming regions; massive stars; interstellar medium; protostars; infrared astronomy; infrared sources
Molecules in Cool Stars: The A2Π ‑ X2Σ+ and the B2Σ+ ‑ X2Σ+ Band Systems of CaCl

Cool red giant stars exhibit absorption bands of calcium monochloride (CaCl) in the optical region. In this work, the bands of CaCl corresponding to the A2Π ‑ X2Σ+ transition with 4 and v″ ≤ 4, and B2Σ+ ‑ X2Σ+ transition with 2 and v″ ≤ 2 are rotationally analyzed with PGOPHER, a multipurpose program for simulating and fitting molecular spectra. All bands were analyzed using high-resolution absorption spectra collected at the National Solar Observatory in 1985, calibrated with atomic lines from a high-resolution emission spectrum obtained in a separate hollow cathode experiment. The results are compared with previous laser-induced fluorescence measurements. Overall, the accuracy of spectroscopic constants for the A2Π and B2Σ+ states is improved. Scaled transition dipole moment calculations were used to obtain line strengths. Line lists are provided with Einstein A coefficients and oscillator strengths, which can be used to determine CaCl stellar abundances. Additionally, isotope splittings allowed us to estimate band origins for the 40Ca37Cl isotopologue based on band-head positions.

Keywords: spectral line lists; laboratory astrophysics
Galactic Archeology with Luminous Red Giant Oscillations in Gaia DR3 Photometry

Asteroseismology has significantly advanced the field of Galactic archeology, providing essential insights into the formation and evolution of our Galaxy. Here we present an asteroseismic analysis of 103 luminous red giant stars that were observed by Gaia in our Galaxy and the Large Magellanic Cloud. Leveraging a period–luminosity–amplitude relationship determined using data from the OGLE mission, we measure distances to these stars of up to 100 kpc, probing distances more than a factor of 2 beyond where Gaia parallaxes can be measured accurately. We have determined distance uncertainties of 8% or better for 80% of the stars in our sample and reduced known distance uncertainties for stars in this sample by more than a factor of 2 on average. Applying this approach to future Gaia data releases can provide more precise and accurate distances and constrain fundamental properties for 10,000+ stars across our Galaxy.

Keywords: asteroseismology; galactic archaeology; variable stars; stellar oscillations
Multiple Channels for the Onset of Magnetism in Isolated White Dwarfs

The presence of a strong magnetic field is a feature common to a significant fraction of degenerate stars, yet little is understood about the field's origin and evolution. New observational constraints from volume-limited surveys point to a more complex situation than a single mechanism valid for all stars. We show that in high-mass white dwarfs, which are probably the results of mergers, magnetic fields are extremely common and very strong and appear immediately in the cooling phase. These fields may have been generated by a dynamo active during the merging. Lower-mass white dwarfs, which are often the product of single-star evolution, are rarely detectably magnetic at birth, but fields appear very slowly, and very weakly, in about a quarter of them. What we may see is an internal field produced in an earlier evolutionary stage that gradually relaxes to the surface from the interior. The frequency and strength of magnetic fields continue to increase to eventually rival those of highly massive stars, particularly after the stars cool past the start of core crystallization, an effect that could be responsible for a dynamo mechanism similar to the one that is active in Earth's interior.

Keywords: magnetic stars; white dwarf stars; spectropolarimetry
Comparison of the Physical Properties of the L4 and L5 Trojan Asteroids from ATLAS Data

Jupiter has nearly 8000 known co-orbital asteroids orbiting in the L4 and L5 Lagrange points called Jupiter Trojan asteroids. Aside from the greater number density of the L4 cloud, the two clouds are in many ways considered to be identical. Using sparse photometric data taken by the Asteroid Terrestrial-impact Last Alert System for 863 L4 Trojans and 380 L5 Trojans, we derive the shape distribution for each of the clouds and find that, on average, the L4 asteroids are more elongated than the L5 asteroids. This shape difference is most likely due to the greater collision rate in the L4 cloud that results from its larger population. We additionally present the phase functions and c - o colors of 266 objects.

Keywords: jupiter trojans; multi-color photometry; sky surveys
Modeling Dense Star Clusters in the Milky Way and Beyond with the CMC Cluster Catalog

We present a set of 148 independent N-body simulations of globular clusters (GCs) computed using the code CMC (Cluster Monte Carlo). At an age of ∼10-13 Gyr, the resulting models cover nearly the full range of cluster properties exhibited by the Milky Way GCs, including total mass, core and half-light radii, metallicity, and galactocentric distance. We use our models to investigate the role that stellar-mass black holes play in the process of core collapse. Furthermore, we study how dynamical interactions affect the formation and evolution of several important types of sources in GCs, including low-mass X-ray binaries, millisecond pulsars, blue stragglers, cataclysmic variables, Type Ia supernovae, calcium-rich transients, and merging compact binaries. While our focus here is on old, low-metallicity GCs, our CMC simulations follow the evolution of clusters over a Hubble time, and they include a wide range of metallicities (up to solar), so that our results can also be used to study younger and higher-metallicity star clusters. Finally, the output from these simulations is available for download at https://cmc.ciera.northwestern.edu/home/.

Keywords: globular star clusters; stellar mass black holes; computational methods; blue straggler stars; binary stars; cataclysmic variable stars; x-ray binary stars; stellar dynamics
Star and Solar System Maps: A History of Celestial Cartography

Since antiquity, people have observed the night sky. To establish order and predictability, people made maps of the heavens. Two kinds emerged. The first were star maps, organized into constellations but focused on stellar location in the sky. Stars were placed in a coordinate system, initially based on celestial latitude and longitude oriented to the ecliptic, but later based on decl. and R.A. oriented to the celestial equator. Over time, telescopic and scientific needs called for more detailed coordinate systems, and constellation images disappeared. The second kind of heavenly map depicted the solar system and focused on planetary locations and surface characteristics. For many centuries, these were cosmological diagrams with concentric planetary and stellar circles, centered first on the Earth and then the Sun. Now such maps have no stellar boundary, and ever larger telescopes and space probes allow us to view planetary surfaces in unprecedented detail.

Keywords: history of astronomy
The Contribution of M-dwarf Flares to the Thermal Escape of Potentially Habitable Planet Atmospheres

The habitability of planets around M dwarfs (≲0.5 M ⊙) can be affected by the X-rays + extreme UV (XUV) emission of these stars, with flares occasionally increasing the XUV flux by more than 2 orders of magnitude above quiescent levels. This wavelength range can warm and ionize terrestrial planets' upper atmospheres, which expands the planetary radius and promotes atmospheric loss. In this work, we study the contribution of the XUV flux due to flares on the atmospheric escape of Earth-like planets orbiting M dwarfs through numerical simulations. We considered the first Gyr of planets with initial surface water abundances between 1 and 10 terrestrial oceans (TO), a small primordial hydrogen envelope (≤10-3 M ⊕), and with host-star masses between 0.2 and 0.6 M ⊙. In this parameter range, we find that flares can remove up to two TO more than nonflaring stars, which, in some cases, translates to a doubling of the total water loss. We also find that flaring can increase atmospheric oxygen partial pressures by hundreds of bars in some cases. These results were obtained by adding a new module for flares to the VPLanet software package and upgrading its atmospheric escape module to account for Roche lobe overflow and radiation/recombination-limited escape.

Keywords: stellar flares; exoplanet atmospheres; star-planet interactions; habitable planets
Student Dust Counter Status Report: The First 50 au

The Venetia Burney Student Dust Counter (SDC) is an in situ dust detector on board the New Horizons spacecraft measuring the interplanetary dust particle (IDP) distribution for grains with mass m > 10-12 g. SDC provides a near-continuous measure of the interplanetary dust environment, with recent results spanning beyond 50 au. This coverage includes the Edgeworth-Kuiper Belt (EKB), suggested by numerical models to be the dominant source of IDP in the outer solar system. Here we present the updated dust density distribution to 50 au and compare estimated flux values to existing theoretical models. SDC observes peak dust flux and densities near 42 au, and we expect a decay with increasing heliocentric distance. Based on SDC measurements, we also discuss the effects of IDP generation, transport, and loss on the evolution of the surfaces of EKB objects, the continual intermixing of their surface material, and the general tendency to homogenize their spectral properties. Continued SDC measurements remain critical for revealing the large-scale structure of the EKB and to guide the interpretation of dust disks around other stars. Additionally, we consider the potential of an interstellar dust (ISD) and "outer" Kuiper Belt contribution to SDC measurements and its effect on anticipated SDC flux values beyond 50 au, and we show that the inclusion of either source to the predicted model results in a noticeable deviation in anticipated SDC measurements beyond 50 au. Current and future SDC measurements also serve to constrain the relative contribution of ISD to SDC's flux and density estimates.

Keywords: interplanetary dust; kuiper belt
3HWC J0631+107/LHAASO J0631+1040: A TeV Halo Powered by the Pulsar J0631+1036?

PSR J0631+1036 is a middle-aged pulsar with properties similar to those of the nearby Geminga pulsar. It is bright in γ-rays, and has been noted as the only source possibly associated with the TeV source 3HWC J0631+107 (also the LHAASO J0631+1040). For understanding the nature of the TeV source, we analyze the GeV γ-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope for the source region. We are able to remove the pulsar's emission from the region from timing analysis, and find that the region is rather clean without possible GeV γ-ray emission present as the counterpart to the TeV source. By comparing this pulsar to Geminga and considering the spectral feature of the TeV source, we argue that it is likely the TeV halo powered by the pulsar.

Keywords: gamma-rays; pulsars
Do All Long-duration Gamma-Ray Bursts Emit GeV Photons?

GRB 190114C extends the focus of gamma-ray burst (GRB) research to the high-energy regime, in which a prime question is "Do all long-duration GRBs emit GeV photons?" Based on the Fermi Large Area Telescope (LAT) 10 yr observations, 54 GRBs initially within the Fermi-LAT field of view and with known redshift are sampled. Within 26 of these GRBs at least one GeV photon has been detected with a probability of >95%, while the other 28 GRBs have no confident GeV photon detection. We hypothesize that all the samples intrinsically emit GeV photons, and the lack of detection is due to the limited capacity of the satellite. We estimate the theoretical number of photons that LAT receives by considering the GRB energy, the distance, and the LAT effective area. Results show, within the uncertainty, that all 26 GRBs with GeV photon detection have a theoretical photon number of >1, and 27 out of 28 GRBs without GeV photon detection have a theoretical photon number of <1. This agreement tends to support our hypothesis and give an answer of "yes" to our initial question.

Keywords: gamma-ray bursters; high energy astrophysics; astronomical instrumentation
Luminous Radio Emission from the Superluminous Supernova 2017ens at 3.3 yr after Explosion

We present the results from a multiyear radio campaign of the superluminous supernova (SLSN) SN 2017ens, which yielded the earliest radio detection of an SLSN to date at the age of ~3.3 yr after explosion. SN 2017ens was not detected at radio frequencies in the first ~300 days but reached L ν ≈ 1028 erg s-1 cm-2 Hz-1 at ν ~ 6 GHz, ~1250 days post explosion. Interpreting the radio observations in the context of synchrotron radiation from the supernova shock interaction with the circumstellar medium (CSM), we infer an effective mass-loss rate $\dot{M}\approx {10}^{-4}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ at r ~ 1017 cm from the explosion's site, for a wind speed of v w = 50-60 km s-1 as measured from optical spectra. These findings are consistent with the spectroscopic metamorphosis of SN 2017ens from hydrogen poor to hydrogen rich ~190 days after explosion reported by Chen et al. SN 2017ens is thus an addition to the sample of hydrogen-poor massive progenitors that explode shortly after having lost their hydrogen envelope. The inferred circumstellar densities, implying a CSM mass up to ~0.5 M ☉, and low velocity of the ejection suggest that binary interactions (in the form of common-envelope evolution and subsequent envelope ejection) play a role in shaping the evolution of the stellar progenitors of SLSNe in the ≲500 yr preceding core collapse.

Keywords: core-collapse supernovae; extragalactic radio sources