adsabs/SciX_UAT_keywords huggingface dataset:
Molecules with ALMA at Planet-forming Scales (MAPS). XIV. Revealing Disk Substructures in Multiwavelength Continuum Emission

Constraining dust properties of planet-forming disks via high-angular-resolution observations is fundamental to understanding how solids are trapped in substructures and how dust growth may be favored or accelerated therein. We use ALMA dust continuum observations of the Molecules with ALMA at Planet-forming Scales (MAPS) disks and explore a large parameter space to constrain the radial distribution of solid mass and maximum grain size in each disk, including or excluding dust scattering. In the nonscattering model, the dust surface density and maximum grain size profiles decrease from the inner disks to the outer disks, with local maxima at the bright ring locations, as expected from dust trapping models. The inferred maximum grain sizes from the inner to outer disks decrease from 1 cm to 1 mm. For IM Lup, HD 163296, and MWC 480 in the scattering model, two solutions are compatible with their observed inner disk emission: one solution corresponding to a maximum grain size of a few millimeters (similar to the nonscattering model), and the other corresponding to a size of a few hundred micrometers. Based on the estimated Toomre parameter, only IM Lup-which shows a prominent spiral morphology in millimeter dust-is found to be gravitationally unstable. The estimated maximum Stokes number in all the disks lies between 0.01 and 0.3, and the estimated turbulence parameters in the rings of AS 209 and HD 163296 are close to the threshold where dust growth is limited by turbulent fragmentation. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: circumstellar dust; interstellar scattering; radiative transfer; radio continuum emission; protoplanetary disks
Spectroscopically Identified Cataclysmic Variables from the LAMOST Survey. II. Period Estimates

We examine a sample of 340 cataclysmic variables (CVs) from the latest data release of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey, along with 18 objects that are newly classified as CVs. In this paper, we focus on investigating the photometric behaviors of these CVs using data from time-domain surveys. The orbital periods of three new and five previously known objects are determined from the long-term light curves displaying eclipses or ellipsoidal variations, and/or time-resolved spectra from LAMOST. For another 16 CVs with measured periods, it is more reliable to obtain consistent periods using light curves from different surveys, as the periods derived from single-site data are still questionable. Follow-up observations are needed to confirm whether the periods have physical meanings or are orbital-related. In our sample, we find that most of the objects have longer periods above the 2 ~ 3 hr gap. Besides period estimates, we also carry out a separate detailed analysis of some valuable CVs, in terms of spectral characteristics and subtype determination. Finally, we discuss the observational properties of this sample, including the distributions of orbital periods, absolute magnitudes, and the statistical properties of each subclass of CVs. In addition, we pick out six non-CV systems, including five illumination-effect binaries, as well as one hot subdwarf, that we came across when searching for CVs, and we investigate their properties based on the spectra and photometric data.

Keywords: cataclysmic variable stars; spectroscopy; photometry; period determination
Stellar Characterization and a Chromospheric Activity Analysis of a K2 Sample of Planet-hosting Stars

Effective temperatures, surface gravities, and iron abundances were derived for 109 stars observed by the K2 mission using equivalent width measurements of Fe I and Fe II lines. Calculations were carried out in local thermodynamic equilibrium using Kurucz model atmospheres. Stellar masses and radii were derived by combining the stellar parameters with Gaia Data Release 3 parallaxes, V magnitudes, and isochrones. The derived stellar and planetary radii have a median internal precision of 1.8% and 2.3%, respectively. The radius gap near R planet ∼ 1.9 R ⊕ was detected in this K2 sample. Chromospheric activity was measured from the Ca II H and K lines using the values of , which were investigated as a function of stellar rotational period (P rot), and we found that chromospheric activity decreases with increasing P rot, although there is a large scatter in (∼0.5) for a given P rot. The activity levels in this sample reveal a paucity of F and G dwarfs with intermediate activity levels (the Vaughan–Preston gap). The effect that stellar activity might have on the derivation of stellar parameters was investigated by including magnetically sensitive Fe I lines in the analysis and we find no significant differences between parameters with and without magnetically sensitive lines, although the more active stars ( ) exhibit a larger scatter in the differences in T eff and [Fe/H].

Keywords: exoplanets; stellar activity; spectroscopy; parallax; stellar types; fundamental parameters of stars; a stars
Dynamical Evolution of Closely Packed Multiple Planetary Systems Subject to Atmospheric Mass Loss

A gap in exoplanets' radius distribution has been widely attributed to the photoevaporation threshold of their progenitors' gaseous envelope. Giant impacts can also lead to substantial mass loss. The outflowing gas endures tidal torque from the planets and their host stars. Alongside the planet-star tidal and magnetic interaction, this effect leads to planets' orbital evolution. In multiple super-Earth systems, especially in those that are closely spaced and/or contain planets locked in mean motion resonances, modest mass loss can lead to dynamical instabilities. In order to place some constraints on the extent of planets' mass loss, we study the evolution of a series of idealized systems of multiple planets with equal masses and a general scaled separation. We consider mass loss from one or more planets either in the conservative limit or with angular momentum loss from the system. We show that the stable preservation of idealized multiple planetary systems requires either a wide initial separation or a modest upper limit in the amount of mass loss. This constraint is stringent for the multiple planetary systems in compact and resonant chains. Perturbation due to either impulsive giant impacts between super-Earths or greater than a few percent mass loss can lead to dynamical instabilities.

Keywords: exoplanet dynamics; exoplanet formation; exoplanet evolution
The Architecture of Multiplanet Systems as a Tracer of Their Formation Mechanisms

Exoplanets observed by the Kepler telescope exhibit a bimodal, radius distribution, which is known as the radius gap. We explore an origin of the radius gap, focusing on multiplanet systems. Our simple theoretical argument predicts that type I planetary migration produces different configurations of protoplanets with different masses and such different configurations can result in two distinguishable populations of small-sized multiplanet systems. We then perform an observational analysis to verify this prediction. In the analysis, multiple Kolmogorov-Smirnov tests are applied to the observed systems, using the statistical measures that are devised to systematically characterize the properties of multiplanet systems. We find with 99.5% confidence that the observed, small-sized multiplanet systems are divided into two distinct populations. The distinction likely originates from different spatial distributions of protoplanets, which are determined by type I migration and subsequently trigger giant impact. We also show that these distinct populations are separated around the radius gap when the gas surface density of protoplanetary disks is ~102 g cm-2 in the vicinity of the host stars. This work therefore emphasizes the importance of planetary migration and the inner disk properties.

Keywords: planet formation; planetary migration; super earths; mini neptunes; protoplanetary disks; exoplanet dynamics
Astrobiology eXploration at Enceladus (AXE): A New Frontiers Mission Concept Study

The Saturnian moon Enceladus presents a unique opportunity to sample the contents of a subsurface liquid water ocean in situ via the continuous plume formed over its south polar terrain using a multi-flyby mission architecture. Previous analyses of the plume's composition by Cassini revealed an energy-rich system laden with salts and organic compounds, representing an environment containing most of the ingredients for life as we know it. Following in the footsteps of the Cassini-Huygens mission, we present Astrobiology eXploration at Enceladus (AXE), a New Frontiers class Enceladus mission concept study carried out during the 2021 NASA Planetary Science Summer School program at the Jet Propulsion Laboratory, California Institute of Technology. We demonstrate that a scientifically compelling geophysical and life-detection mission to Enceladus can be carried out within the constraints of a New Frontiers-5 cost cap using a modest instrument suite, requiring only a narrow angle, high-resolution telescopic imager, a mass spectrometer, and a high-gain antenna for radio communications and gravity science measurements. Using a multi-flyby mission architecture, AXE would evaluate the habitability and potential for life at Enceladus through a synergistic combination of in situ chemical analysis measurements aimed at directly detecting the presence of molecular biosignatures, along with geophysical and geomorphological investigations to contextualize chemical biosignatures and further evaluate the habitability of Enceladus over geologic time.

Keywords: enceladus; astrobiology; biosignatures; geological processes; planetary geology; saturnian satellites; mass spectrometry; flyby missions
Heavy-element Abundances in P-rich Stars: A New Site for the s-process?

The recently discovered phosphorus-rich stars pose a challenge to stellar evolution and nucleosynthesis theory, as none of the existing models can explain their extremely peculiar chemical abundances pattern. Apart from the large phosphorus enhancement, such stars also show enhancement in other light (O, Mg, Si, and Al) and heavy (e.g., Ce) elements. We have obtained high-resolution optical spectra of two optically bright phosphorus-rich stars (including a new P-rich star), for which we have determined a larger number of elemental abundances (from C to Pb). We confirm the unusual light-element abundance pattern with very large enhancements of Mg, Si, Al, and P, and possibly some Cu enhancement, but the spectrum of the new P-rich star are the only ones to reveal some C(+N) enhancement. When compared to other appropriate metal-poor and neutron-capture enhanced stars, the two P-rich stars show heavy-element overabundances similar to low neutron density s-process nucleosynthesis, with high first-peak (Sr, Y, and Zr) and second-peak (Ba, La, Ce, and Nd) element enhancements (even some Pb enhancement in one star) and a negative [Rb/Sr] ratio. However, this s-process is distinct from the one occurring in asymptotic giant branch (AGB) stars. The notable distinctions encompass larger [Ba/La] and lower Eu and Pb than their AGB counterparts. Our observations should guide stellar nucleosynthesis theoreticians and observers to identify the P-rich star progenitor, which represents a new site for s-process nucleosynthesis, with important implications for the chemical evolution of our Galaxy.

Keywords: stellar nucleosynthesis; s-process; stellar abundances; chemically peculiar stars; population ii stars
Interpolation of Turbulent Magnetic Fields and Its Consequences on Cosmic Ray Propagation

Numerical simulations of the propagation of charged particles through magnetic fields solving the equation of motion often leads to the usage of an interpolation in the case of discretely defined magnetic fields, typically given on a homogeneous grid structure. However, the interpolation method influences the magnetic field properties and, therefore, also the propagation of particles through these fields. To determine the resulting error, we compare three different interpolation routines—trilinear, tricubic, and nearest neighbor interpolation—in the case of isotropic, turbulent magnetic fields. First, we analyze the impact of the different interpolation methods on the root mean square field strength, the divergence, and the spectrum of the turbulent magnetic field. Here, the nearest neighbor interpolation shows some clear benefits compared with the trilinear method; however, that changes significantly if we consider the particle propagation. In principle, a better interpolation method also yields a better description of the particle transport. In the case of field line random walk, it is shown that none of these methods, especially not the nearest neighbor interpolation, is able to yield an accurate description of the diffusion coefficient, exposing the need for a continuous, grid-less turbulent magnetic field. We optimize the performance of an algorithm that generates such a magnetic field by more than an order of magnitude. Further, the necessary number of wave-modes is determined, so that this continuous method supports realistic simulations over a larger energy range without limitations by the available memory.

Keywords: extragalactic magnetic fields; cosmic rays; astrophysical processes; cosmic magnetic fields theory; computational methods
Statistical Analysis of Intermittency and its Association with Proton Heating in the Near-Sun Environment

We use data from the first six encounters of the Parker Solar Probe and employ the partial variance of increments (PVI) method to study the statistical properties of coherent structures in the inner heliosphere with the aim of exploring physical connections between magnetic field intermittency and observable consequences such as plasma heating and turbulence dissipation. Our results support proton heating localized in the vicinity of, and strongly correlated with, magnetic structures characterized by PVI ≥ 1. We show that, on average, such events constitute ≈19% of the data set, though variations may occur depending on the plasma parameters. We show that the waiting time distribution (WT) of identified events is consistent across all six encounters following a power-law scaling at lower WTs. This result indicates that coherent structures are not evenly distributed in the solar wind but rather tend to be tightly correlated and form clusters. We observe that the strongest magnetic discontinuities, PVI ≥ 6, usually associated with reconnection exhausts, are sites where magnetic energy is locally dissipated in proton heating and are associated with the most abrupt changes in proton temperature. However, due to the scarcity of such events, their relative contribution to energy dissipation is minor. Taking clustering effects into consideration, we show that smaller scale, more frequent structures with PVI between 1 ≲ PVI ≲ 6 play a major role in magnetic energy dissipation. The number density of such events is strongly associated with the global solar wind temperature, with denser intervals being associated with higher T p .

Keywords: solar wind; space plasmas; plasma astrophysics
The Target-selection Pipeline for the Dark Energy Spectroscopic Instrument

In 2021 May, the Dark Energy Spectroscopic Instrument (DESI) began a 5 yr survey of approximately 50 million total extragalactic and Galactic targets. The primary DESI dark-time targets are emission line galaxies, luminous red galaxies, and quasars. In bright time, DESI will focus on two surveys known as the Bright Galaxy Survey and the Milky Way Survey. DESI also observes a selection of "secondary" targets for bespoke science goals. This paper gives an overview of the publicly available pipeline (desitarget) used to process targets for DESI observations. Highlights include details of the different DESI survey targeting phases, the targeting ID (TARGETID) used to define unique targets, the bitmasks used to indicate a particular type of target, the data model and structure of DESI targeting files, and examples of how to access and use the desitarget code base. This paper will also describe "supporting" DESI target classes, such as standard stars, sky locations, and random catalogs that mimic the angular selection function of DESI targets. The DESI target-selection pipeline is complex and sizable; this paper attempts to summarize the most salient information required to understand and work with DESI targeting data.

Keywords: catalogs; sky surveys; cosmology; observational cosmology; galaxy distances; galaxies; redshift surveys; quasars; milky way galaxy; astronomy data analysis; open source software; astronomy software
Linking Characteristics of the Polycyclic Aromatic Hydrocarbon Population with Galaxy Properties: A Quantitative Approach Using the NASA Ames PAH IR Spectroscopic Database

Utilizing the data and tools provided through the NASA Ames PAH IR Spectroscopic Database (PAHdb), we study the PAH component of over 900 Spitzer-IRS galaxy spectra. Employing a database-fitting approach, the average PAH size, the PAH size distribution, and PAH ionization fraction are deduced. In turn, we examine their connection with the properties of the host galaxy. We found that PAH population within galaxies consists of middle-sized PAHs with an average number of carbon atoms of $\overline{{N}_{C}}$ = 55, and a charge state distribution of ~40% ionized-60% neutral. We describe a correlation between the 6.2/11.2 μm PAH ratio with the ionization parameter ( $\gamma \equiv {({G}_{0}/{n}_{{\rm{e}}})({T}_{\mathrm{gas}}/1\ {\rm{K}})}^{0.5}$ ), a moderate correlation between the 8.6/11.2 μm PAH ratio and specific star formation rate, and a weak anticorrelation between γ and M *. From the PAHdb decomposition, we provide estimates for the 3.3 μm PAH band, not covered by Spitzer observations, and establish a correlation between the 3.3/11.2 μm PAH ratio with N C. We further deliver a library of mid-IR PAH template spectra parameterized on PAH size and ionization fraction, which can be used in galaxy spectral energy distribution fitting codes for the modeling of the mid-IR PAH emission component in galaxies.

Keywords: interstellar molecules; interstellar line emission; infrared sources; interstellar medium
Analysis of Multi-hour Continuous Observations of Seven Millisecond Pulsars

Precision pulsar timing can be used for a variety of astrophysical tests, from the detection of gravitational waves to probing the properties of the interstellar medium. Here we analyze various noise contributions to pulsar timing residuals from continuous multi-hour observations of seven millisecond pulsars (MSPs). We present scintillation bandwidth measurements for all MSPs in the sample, some for the first time. We also present scintillation timescale measurements and lower limits for all MSPs for the first time. In addition, we present upper limits on the contribution of pulse phase jitter to the timing residual error for all MSPs. These long observations also allow us to constrain variations in dispersion measures (DMs) on hour-long timescales for several millisecond pulsars. We find that there are no apparent DM variations in any of the MSPs studied on these timescales, as expected. In light of new radio telescopes, such as the Canadian Hydrogen Intensity Mapping Experiment, which will be able to time many pulsars for a short time each day, we search for differences in timing precisions from continuous pulse times of arrival (TOAs) and from equivalent length time-discontinuous TOAs. We find no differences in the precision for any of the MSPs in our sample, as expected. We conclude that the TOA variations are consistent with the expected breakdown into template-fitting, jitter, and scintillation errors.

Keywords: millisecond pulsars; pulsars; interstellar medium; interstellar scintillation
Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope

The Event Horizon Telescope (EHT) has recently delivered the first resolved images of M87*, the supermassive black hole in the center of the M87 galaxy. These images were produced using 230 GHz observations performed in 2017 April. Additional observations are required to investigate the persistence of the primary image feature—a ring with azimuthal brightness asymmetry—and to quantify the image variability on event horizon scales. To address this need, we analyze M87* data collected with prototype EHT arrays in 2009, 2011, 2012, and 2013. While these observations do not contain enough information to produce images, they are sufficient to constrain simple geometric models. We develop a modeling approach based on the framework utilized for the 2017 EHT data analysis and validate our procedures using synthetic data. Applying the same approach to the observational data sets, we find the M87* morphology in 2009-2017 to be consistent with a persistent asymmetric ring of ∼40 μas diameter. The position angle of the peak intensity varies in time. In particular, we find a significant difference between the position angle measured in 2013 and 2017. These variations are in broad agreement with predictions of a subset of general relativistic magnetohydrodynamic simulations. We show that quantifying the variability across multiple observational epochs has the potential to constrain the physical properties of the source, such as the accretion state or the black hole spin.

Keywords: black holes; galaxy accretion disks; galaxy accretion; supermassive black holes; active galactic nuclei; low-luminosity active galactic nuclei; very long baseline interferometry; astronomy data modeling; radio interferometry
TESS Data for Asteroseismology (T'DA) Stellar Variability Classification Pipeline: Setup and Application to the Kepler Q9 Data

The NASA Transiting Exoplanet Survey Satellite (TESS) is observing tens of millions of stars with time spans ranging from ~27 days to about 1 yr of continuous observations. This vast amount of data contains a wealth of information for variability, exoplanet, and stellar astrophysics studies but requires a number of processing steps before it can be fully utilized. In order to efficiently process all the TESS data and make it available to the wider scientific community, the TESS Data for Asteroseismology working group, as part of the TESS Asteroseismic Science Consortium, has created an automated open-source processing pipeline to produce light curves corrected for systematics from the short- and long-cadence raw photometry data and to classify these according to stellar variability type. We will process all stars down to a TESS magnitude of 15. This paper is the next in a series detailing how the pipeline works. Here, we present our methodology for the automatic variability classification of TESS photometry using an ensemble of supervised learners that are combined into a metaclassifier. We successfully validate our method using a carefully constructed labeled sample of Kepler Q9 light curves with a 27.4 days time span mimicking single-sector TESS observations, on which we obtain an overall accuracy of 94.9%. We demonstrate that our methodology can successfully classify stars outside of our labeled sample by applying it to all ~167,000 stars observed in Q9 of the Kepler space mission.

Keywords: asteroseismology