adsabs/SciX_UAT_keywords huggingface dataset:
Cepheids with Giant Companions. I. Revealing a Numerous Population of Double-lined Binary Cepheids

Masses of classical Cepheids of 3-11 M⊙ are predicted by theory but those measured clump between 3.6-5 M⊙. As a result, their mass-luminosity relation is poorly constrained, impeding our understanding of basic stellar physics and the Leavitt Law. All Cepheid masses come from the analysis of 11 binary systems, including only five that are double lined and well suited for accurate dynamical mass determination. We present a project to analyze a new, numerous group of Cepheids in double-lined binary (SB2) systems to provide mass determinations in a wide mass interval and study their evolution. We analyze a sample of 41 candidate binary LMC Cepheids spread along the P-L relation, which are likely accompanied by luminous red giants, and present indirect and direct indicators of their binarity. In a spectroscopic study of a subsample of 18 brightest candidates, for 16 we detected lines of two components in the spectra, already quadrupling the number of Cepheids in SB2 systems. Observations of the whole sample may thus lead to quadrupling all the Cepheid mass estimates available now. For the majority of our candidates, erratic intrinsic period changes dominate over the light-travel-time effect due to binarity. However, the latter may explain the periodic phase modulation for four Cepheids. Our project paves the way for future accurate dynamical mass determinations of Cepheids in the LMC, Milky Way, and other galaxies, which will potentially increase the number of known Cepheid masses even 10-fold, hugely improving our knowledge about these important stars. * Based on observations collected at the European Southern Observatory, Chile. † This paper includes data gathered with the 6.5 m Magellan Clay Telescope at Las Campanas Observatory, Chile.

Keywords: cepheid variable stars; delta cepheid variable stars; spectroscopic binary stars; late-type giant stars
A Semiblind PCA-based Foreground Subtraction Method for 21 cm Intensity Mapping

The principal component analysis (PCA) method and the singular value decomposition (SVD) method are widely used for foreground subtraction in 21 cm intensity mapping experiments. We show their equivalence, and point out that the condition for completely clean separation of foregrounds and cosmic 21 cm signal using the PCA/SVD is unrealistic. We propose a PCA-based foreground subtraction method, dubbed the "singular vector projection (SVP)" method, which exploits a priori information of the left and/or right singular vectors of the foregrounds. We demonstrate with simulation tests that this new, semiblind method can reduce the error of the recovered 21 cm signal by orders of magnitude, even if only the left and/or right singular vectors in the largest few modes are exploited. The SVP estimators provide a new, effective approach for 21 cm observations to remove foregrounds and uncover the physics in the cosmic 21 cm signal.

Keywords: cosmology; astronomical methods; h i line emission; principal component analysis
Sodium Brightening of (3200) Phaethon near Perihelion

Sunskirting asteroid (3200) Phaethon has been repeatedly observed in Solar Terrestrial Relations Observatory (STEREO) Heliospheric Imager 1 (HI1) imagery to anomalously brighten and produce an antisunward tail for a few days near each perihelion passage, phenomena previously attributed to the ejection of micron-sized dust grains. Color imaging by the Solar and Heliospheric Observatory (SOHO) Large Angle Spectrometric Coronagraph (LASCO) during the 2022 May apparition indicates that the observed brightening and tail development instead capture the release of sodium atoms, which resonantly fluoresce at the 589.0/589.6 nm D lines. While HI1's design bandpass nominally excludes the D lines, filter degradation has substantially increased its D line sensitivity, as quantified by the brightness of Mercury's sodium tail in HI1 imagery. Furthermore, the expected fluorescence efficiency and acceleration of sodium atoms under solar radiation readily reproduce both the photometric and morphological behaviors observed by LASCO and HI1 during the 2022 apparition and the 17 earlier apparitions since 1997. This finding connects Phaethon to the broader population of sunskirting and sungrazing comets observed by SOHO, which often also exhibit bright sodium emission with minimal visible dust, but distinguishes it from other sunskirting asteroids without detectable sodium production under comparable solar heating. These differences may reflect variations in the degree of sodium depletion of near-surface material and thus the extent and/or timing of any past or present resurfacing activity.

Keywords: comet tails; near-earth objects; comet volatiles; sungrazers; sunskirters; comet origins; asteroid surfaces
On the Fate of Interstellar Objects Captured by Our Solar System

With the recent discoveries of interstellar objects Oumuamua and Borisov traversing the solar system, understanding the dynamics of interstellar objects is more pressing than ever. These detections have highlighted the possibility that captured interstellar material could be trapped in our solar system. The first step in rigorously investigating this question is to calculate a capture cross section for interstellar objects as a function of hyperbolic excess velocity, which can be convolved with any velocity dispersion to compute a capture rate. Although the cross section provides the first step toward calculating the mass of alien rocks residing in our solar system, we also need to know the lifetime of the captured objects. We use an ensemble of N-body simulations to characterize a dynamical lifetime for captured interstellar objects and determine the fraction of surviving objects as a function of time (since capture). We also illuminate the primary effects driving their secular evolution. Finally, we use the resulting dynamical lifetime function to estimate the current inventory of captured interstellar material in the solar system. We find that capture from the field yields a steady-state mass of only ~10-13 M⊕, whereas the mass remaining from capture events in the birth cluster is roughly 10-9 M⊕.

Keywords: solar system; dynamical evolution; small solar system bodies; interstellar objects; kuiper belt; oort cloud
The Black Hole Mass-Color Relations for Early- and Late-type Galaxies: Red and Blue Sequences

The tight correlations between supermassive black hole (SMBH) mass (MBH) and the properties of the host galaxy have useful implications for our understanding of the growth of SMBHs and of the evolution of galaxies. Here, we present newly observed correlations between MBH and the host galaxy total UV-[3.6] color ( ${{ \mathcal C }}_{\mathrm{UV},\mathrm{tot}}$ , Pearson's r = 0.6-0.7) for a sample of 67 galaxies (20 early-type galaxies and 47 late-type galaxies) with directly measured MBH in the Galaxy Evolution Explorer/S4G survey. The colors are carefully measured in a homogeneous manner using the far-UV, near-UV, and 3.6 μm magnitudes of the galaxies and their multicomponent structural decompositions in the literature. We find that more massive SMBHs are hosted by (early- and late-type) galaxies with redder colors, but the ${M}_{\mathrm{BH}}-{{ \mathcal C }}_{\mathrm{UV},\mathrm{tot}}$ relations for the two morphological types have slopes that differ at ∼2σ level. Early-type galaxies define a red sequence in the ${M}_{\mathrm{BH}}-{{ \mathcal C }}_{\mathrm{UV},\mathrm{tot}}$ diagrams, while late-type galaxies trace a blue sequence. Within the assumption that the specific star formation rate of a galaxy (sSFR) is well traced by LUV/L3.6, it follows that the SMBH masses for late-type galaxies exhibit a steeper dependence on sSFR than those for early-type galaxies. The ${M}_{\mathrm{BH}}-{{ \mathcal C }}_{\mathrm{UV},\mathrm{tot}}$ and MBH - L3.6,tot relations for the sample galaxies reveal a comparable level of vertical scatter in the log MBH direction, approximately 5%-27% more than the vertical scatter of the MBH - σ relation. Our ${M}_{\mathrm{BH}}-{{ \mathcal C }}_{\mathrm{UV},\mathrm{tot}}$ relations suggest different channels of SMBH growth for early- and late-type galaxies, consistent with their distinct formation and evolution scenarios. These new relations offer the prospect of estimating SMBH masses reliably using the galaxy color alone. Furthermore, we show that they are capable of estimating intermediate black hole masses in low-mass early- and late-type galaxies.

Keywords: supermassive black holes; cd galaxies; elliptical galaxies; lenticular galaxies; spiral galaxies; galaxy colors; galaxy photometry; galaxy nuclei; galaxy structure
The Combined Effects of Vertical and Horizontal Shear Instabilities in Stellar Radiative Zones

Shear instabilities can be the source of significant amounts of turbulent mixing in stellar radiative zones. Past attempts at modeling their effects (either theoretically or using numerical simulations) have focused on idealized geometries, where the shear is either purely vertical or purely horizontal. In stars, however, the shear can have arbitrary directions with respect to gravity. In this work, we use direct numerical simulations to investigate the nonlinear saturation of shear instabilities in a stably stratified fluid, where the shear is sinusoidal in the horizontal direction and either constant or sinusoidal in the vertical direction. We find that in the parameter regime studied here (nondiffusive, fully turbulent flow), the mean vertical shear does not play any role in controlling the dynamics of the resulting turbulence, unless its Richardson number is smaller than 1 (approximately). As most stellar radiative regions have a Richardson number much greater than 1, our result implies that the vertical shear can essentially be ignored in the computation of the vertical mixing coefficient associated with shear instabilities for the purpose of stellar evolution calculations, even when it is much larger than the horizontal shear (as in the solar tachocline, for instance).

Keywords: astrophysical fluid dynamics; hydrodynamics; stellar evolution; stellar physics; hydrodynamical simulations; stellar rotation; solar rotation; stellar processes
Low-albedo Surfaces of Lava Worlds

Hot super-Earths are exoplanets with short orbital periods (<10 days), heated by their host stars to temperatures high enough for their rocky surfaces to become molten. A few hot super-Earths exhibit high geometric albedos (>0.4) in the Kepler band (420-900 nm). We are motivated to determine whether reflection from molten lava and quenched glasses (a product of rapidly cooled lava) on the surfaces of hot super-Earths contribute to the observationally inferred high geometric albedos. We experimentally measure reflection from rough- and smooth-textured quenched glasses of both basalt and feldspar melts. For lava reflectance values, we use specular reflectance values of molten silicates from non-crystalline solids literature. Integrating the empirical glass reflectance function and non-crystalline solids reflectance values over the dayside surface of the exoplanet at secondary eclipse yields an upper limit for the albedo of a lava-quenched glass planet surface of ∼0.1. We conclude that lava planets with solid (quenched glass) or liquid (lava) surfaces have low albedos. The high albedos of some hot super-Earths are most likely explained by atmospheres with reflective clouds (or, for a narrow range of parameter space, possibly Ca/Al oxide melt surfaces). Lava planet candidates in TESS data can be identified for follow-up observations and future characterization.

Keywords: exoplanet surface characteristics; experimental techniques; super earths; exoplanet atmospheres; exoplanet surface composition; interdisciplinary astronomy
Formation of Lunar Basins from Impacts of Leftover Planetesimals

The Moon holds important clues to the early evolution of the solar system. Some 50 impact basins (crater diameter D > 300 km) have been recognized on the lunar surface, implying that the early impact flux was much higher than it is now. The basin-forming impactors were suspected to be asteroids released from an inner extension of the main belt (1.8-2.0 au). Here we show that most impactors were instead rocky planetesimals left behind at ~0.5-1.5 au after the terrestrial planet accretion. The number of basins expected from impacts of leftover planetesimals largely exceeds the number of known lunar basins, suggesting that the first ~200 Myr of impacts are not recorded on the lunar surface. The Imbrium basin formation (age ≃3.92 Gyr; impactor diameter d ≳ 100 km) occurs with a 15%-35% probability in our model. Imbrium must have formed unusually late to have only two smaller basins (Orientale and Schrödinger) forming afterwards. The model predicts ≃20 d > 10 km impacts on the Earth 2.5-3.5 Gyr ago (Ga), which is comparable to the number of known spherule beds in the late Archean.

Keywords: solar system formation; lunar impacts
Methods for the Detection of Stellar Rotation Periods in Individual TESS Sectors and Results from the Prime Mission

For ongoing studies of the role of rotation in stellar evolution, we require large catalogs of rotation periods for testing and refining gyrochronology. While there is a wealth of data from the Kepler and K2 missions, the Transiting Exoplanet Survey Satellite (TESS) presents both an opportunity and a challenge: despite its all-sky coverage, rotation periods remain hard to detect. We analyzed individual TESS sectors to detect short-period stellar rotation, using only parameters measured from light curves for a robust and unbiased method of evaluating detections. We used random forest classifiers for vetting, trained on a large corpus of period measurements in Kilodegree Extremely Little Telescope data from the Oelkers et al. catalog and using TESS full-frame image light curves generated by eleanor. Finally, using data from the first 26 sectors of TESS, we analyzed 432,704 2 minutes cadence single-sector light curves for FGKM dwarfs. We detected 16,800 periods in individual sector light curves, covering 10,909 distinct targets, and we present a catalog of the median period for each target as measured by a Lomb–Scargle periodogram.

Keywords: stellar rotation; period determination; astronomy data analysis; random forests
Kinematics of the Central Stars Powering Bowshock Nebulae and the Large Multiplicity Fraction of Runaway OB Stars

OB stars powering stellar bowshock nebulae (SBNe) have been presumed to have large peculiar velocities. We measured peculiar velocities of SBN central stars to assess their kinematics relative to the general O-star population using Gaia EDR3 data for 267 SBN central stars and a sample of 455 Galactic O stars to derive projected velocities v 2D. For a subset of each sample, we obtained new optical spectroscopy to measure radial velocities and identify multiple-star systems. We find a minimum multiplicity fraction of 36% ± 6% among SBN central stars, consistent with >28% among runaway Galactic O stars. The large multiplicity fraction among runaways implicates very efficient dynamical ejection rather than binary-supernova origins. The median v 2D of SBN central stars is v 2D = 14.6 km s-1, larger than the median v 2D = 11.4 km s-1 for non-bowshock O stars. Central stars of SBNe have a runaway (v 2D > 25 km s-1) fraction of 24 <?CDATA ${}_{-7}^{+9}$ %, consistent with the <?CDATA ${22}_{-3}^{+3}$ % for control-sample O stars. Most (76%) SBNe central stars are not runaways. Our analysis of alignment (ΔPA) between the nebular morphological and v 2D kinematic position angles reveals two populations: a highly aligned (σ PA = 25°) population that includes stars with the largest v 2D (31% of the sample) and a random (nonaligned) population (69%). SBNe that lie within or near H II regions comprise a larger fraction of this latter component than SBNe in isolated environments, implicating localized ISM flows as a factor shaping their orientations and morphologies. We outline a new conceptual approach to computing the solar local standard of rest motion, yielding [U ⊙, V ⊙, W ⊙] = [5.5, 7.5,4.5] km s-1.

Keywords: runaway stars; massive stars; early-type stars; stellar kinematics; ob stars; h ii regions; circumstellar dust; high-velocity stars
An Early Catalog of Planet-hosting Multiple-star Systems of Order Three and Higher

We present a catalog (status 2022 July 1) of triple and higher-order systems identified containing exoplanets based on data from the literature, including various analyses. We explore statistical properties of the systems with a focus on both the stars and the planets. So far, about 30 triple systems and one to three quadruple systems, including (mildly) controversial cases, have been found. The total number of planets is close to 40. All planet-hosting triple-star systems are highly hierarchic, consisting of a quasi-binary complemented by a distant stellar component, which is in orbit about the common center of mass. Furthermore, the quadruple systems are in fact pairs of close binaries ("double-doubles"), with one binary harboring a planet. For the different types of star-planet systems, we introduce a template for the classifications of planetary orbital configurations in correspondence to the hierarchy of the system and the planetary host. The data show that almost all stars are main-sequence stars, as expected. However, the stellar primaries tend to be more massive (i.e., corresponding to spectral types A, F, and G) than expected from single-star statistics, a finding also valid for stellar secondaries but less pronounced. Tertiary stellar components are almost exclusively low-mass stars of spectral type M. Almost all planets have been discovered based on either the Radial Velocity method or the Transit method. Both gas giants (the dominant type) and terrestrial planets (including super-Earths) have been identified. We anticipate the expansion of this database in the light of future planetary search missions.

Keywords: catalogs; exoplanets; exoplanet systems; stellar types; interstellar dynamics; stellar physics; exoplanet catalogs; stellar astronomy; exoplanet astronomy
Catastrophic Cooling in Superwinds. II. Exploring the Parameter Space

Superwinds and superbubbles driven by mechanical feedback from super star clusters (SSCs) are common features in many star-forming galaxies. While the adiabatic fluid model can well describe the dynamics of superwinds, several observations of starburst galaxies revealed the presence of compact regions with suppressed superwinds and strongly radiative cooling, i.e., catastrophic cooling. In the present study, we employ the nonequilibrium atomic chemistry and cooling package MAIHEM, built on the FLASH hydrodynamics code, to generate a grid of models investigating the dependence of cooling modes on the metallicity, SSC outflow parameters, and ambient density. While gas metallicity plays a substantial role, catastrophic cooling is more sensitive to high mass loading and reduced kinetic heating efficiency. Our hydrodynamic simulations indicate that the presence of a hot superbubble does not necessarily imply an adiabatic outflow and vice versa. Using CLOUDY photoionization models, we predict UV and optical line emission for both adiabatic and catastrophic cooling outflows, for radiation-bounded and partially density-bounded models. Although the line ratios predicted by our radiation-bounded models agree well with observations of star-forming galaxies, they do not provide diagnostics that unambiguously distinguish the parameter space of catastrophically cooling flows. Comparison with observations suggests the possibility of minor density bounding, nonequilibrium ionization, and/or observational bias toward the central outflow regions.

Keywords: superbubbles; superclusters; cooling flows; h ii regions; starburst galaxies; emission line galaxies; lyman-break galaxies
Impact of Natal Kicks on Merger Rates and Spin-Orbit Misalignments of Black Hole-Neutron Star Mergers

The long wait for the detection of merging black hole-neutron star (BH-NS) binaries is finally over with the announcement by the LIGO/Virgo/Kagra collaboration of GW200105 and GW200115. Remarkably, the primary of GW200115 has a negative spin projection onto the orbital angular momentum, with about 90% probability. Merging BH-NS binaries are expected to form mainly through the evolution of massive binary stars in the field, since their dynamical formation in dense star clusters is strongly suppressed by mass segregation. In this Letter, we carry out a systematic statistical study of the binary stars that evolve to form a BH-NS binary, considering different metallicities and taking into account the uncertainties on the natal-kick distributions for BHs and NSs and on the common-envelope phase of binary evolution. Under the assumption that the initial stellar spins are aligned with the binary angular momentum, we show that both large natal kicks for NSs (≳150 km s-1) and high efficiencies for common-envelope ejection are required to simultaneously explain the inferred high merger rates and the large spin-orbit misalignment of GW200115.

Keywords: astrophysical black holes; black hole spin-flip; black holes; stellar mass black holes; neutron stars; gravitational wave astronomy; gravitational wave detectors; gravitational wave sources; gravitational waves
Orbital Characterization of Superbolides Observed from Space: Dynamical Association with Near-Earth Objects, Meteoroid Streams, and Identification of Hyperbolic Meteoroids

There is an unceasing incoming flux of extraterrestrial materials reaching the Earth atmosphere. Some of these objects produce luminous columns when they ablate during the hypersonic encounter with air molecules. A few fireballs occur each year bright enough to be detected from space. The source of these events is still a matter of debate, but it is generally accepted that they are of sporadic origin. We studied the NASA-JPL Center for NEOs Studies (CNEOS) fireball database to infer the dynamic origin of large bolides produced by meter-sized projectiles that impacted our planet. These likely meteorite-dropping events were recorded by the US Government satellite sensors. We estimated the false-positive rate and analyzed the time evolution of multiple orbit dissimilarity criteria concerning potential associations with near-Earth objects and meteoroid streams. We found that at least 16% of the large bolides could be associated with meteoroid streams, about 4% are likely associated with near-Earth asteroids, and 4% may be linked to near-Earth comets. This implies that a significant fraction of meter-sized impactors producing large bolides may have an asteroidal or cometary origin. In addition, we found at least three bolides having hyperbolic orbits with high tensile strength values. Meter-sized meteoroids of interstellar origin could be more common than previously thought, representing about 1% of the flux of large bolides. The inferred bulk physical properties suggest that the interstellar medium could bias these projectiles toward high strength rocks with the ability to survive prolonged exposure to the harsh interstellar space conditions.

Keywords: meteoroids; meteor streams; near-earth objects; interstellar objects