adsabs/SciX_UAT_keywords huggingface dataset:
Are Faint Supernovae Responsible for Carbon-enhanced Metal-poor Stars?

Mixing and fallback models in faint supernova models are supposed to reproduce the abundance patterns of observed carbon-enhanced metal-poor (CEMP) stars in the Galactic halo. A fine-tuning of the model parameters for individual stars is required to reproduce the observed ratios of carbon to iron. We focus on extremely metal-poor stars formed out of the ejecta from the mixing and fallback models using a chemical evolution model. Our chemical evolution models take into account the contribution of individual stars to chemical enrichment in host halos, together with their evolution in the context of the hierarchical clustering. Parameterized models of mixing and fallback models for Population III faint supernovae are implemented in the chemical evolution models with merger trees to reproduce the observed CEMP stars. A variety of choices for model parameters on star formation and metal pollution by faint supernovae are unable to reproduce the observed stars with $[\mathrm{Fe}/{\rm{H}}]\lesssim -4$ and $[{\rm{C}}/{\rm{H}}]\gtrsim -2$ , which are the majority of CEMP stars among the lowest-metallicity stars. Only possible solution is to form stars from small ejecta mass, which produces an inconsistent metallicity distribution function. We conclude that not all the CEMP stars are explicable by the mixing and fallback models. We also tested the contribution of binary mass transfers from AGB stars that are also supposed to reproduce the abundances of known CEMP stars. This model reasonably reproduces the distribution of carbon and iron abundances simultaneously only if we assume that long-period binaries are favored at $[\mathrm{Fe}/{\rm{H}}]\lesssim -3.5$ .

Keywords: galaxy chemical evolution; chemical enrichment; halo stars; population ii stars; population iii stars
Reconstructing the Assembly of Massive Galaxies. I. The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at z ≈ 2

We study the relationship between the morphology and star formation history (SFH) of 361 quiescent galaxies (QGs) at redshift <z obs> ≈ 2, with stellar mass $\mathrm{log}{M}_{* }\geqslant 10.3$ , selected with the UVJ technique. Taking advantage of panchromatic photometry covering the rest-frame UV-to-NIR spectral range ( ≈40 bands), we reconstruct the nonparametric SFH of the galaxies with the fully Bayesian SED fitting code PROSPECTOR. We find that the half-light radius R e , observed at z obs, depends on the formation redshift of the galaxies, z form, and that this relationship depends on M *. At $\mathrm{log}{M}_{* }\lt 11$ , the relationship is consistent with ${R}_{e}\propto {\left(1+{z}_{\mathrm{form}}\right)}^{-1}$ , in line with the expectation that the galaxies' central density depends on the cosmic density at the time of their formation, i.e., the "progenitor effect." At $\mathrm{log}{M}_{* }\gt 11$ , the relationship between R e and z form flattens, suggesting that mergers become increasingly important for the size growth of more massive galaxies after they quenched. We also find that the relationship between z form and galaxy compactness similarly depends on M *. While no clear trend is observed for QGs with $\mathrm{log}{M}_{* }\gt 11$ , lower-mass QGs that formed earlier, i.e., with larger z form, have larger central stellar-mass surface densities, both within the R e (Σ e ) and central 1 kpc (Σ1 kpc), and also larger M 1 kpc/M *, the fractional mass within the central 1 kpc. These trends between z form and compactness, however, essentially disappear if the progenitor effect is removed by normalizing the stellar density with the cosmic density at z form. Our findings highlight the importance of reconstructing the SFH of galaxies before attempting to infer their intrinsic structural evolution.

Keywords: apparent magnitude; galaxy evolution; galaxy structure; high-redshift galaxies; quenched galaxies
Accretion Disk Size and Updated Time-delay Measurements in the Gravitationally Lensed Quasar SDSS J165043.44+425149.3

We analyze variability in 15-season optical lightcurves from the doubly imaged lensed quasar SDSS J165043.44+425149.3 (SDSS1650), comprising five seasons of monitoring data from the Maidanak Observatory (277 nights in total, including the two seasons of data previously presented in Vuissoz et al.), five seasons of overlapping data from the Mercator telescope (269 nights), and 12 seasons of monitoring data from the US Naval Observatory, Flagstaff Station at lower cadence (80 nights). We update the 2007 time-delay measurement for SDSS1650 with these new data, finding a time delay of ${\rm{\Delta }}{t}_{\mathrm{AB}}=-{55.1}_{-3.7}^{+4.0}$ days, with image A leading image B. We analyze the microlensing variability in these lightcurves using a Bayesian Monte Carlo technique to yield measurements of the size of the accretion disk at λ rest = 2420 Å, finding a half-light radius of log(r 1/2/cm) = ${16.19}_{-0.58}^{+0.38}$ assuming a 60° inclination angle. This result is unchanged if we model 30% flux contamination from the broad-line region. We use the width of the Mg II line in the existing Sloan Digital Sky Survey spectra to estimate the mass of this system's supermassive black hole, finding M BH = 2.47 × 109 M ⊙. We confirm that the accretion disk size in this system, whose black hole mass is on the very high end of the M BH scale, is fully consistent with the existing quasar accretion disk size–black hole mass relation.

Keywords: quasar microlensing; quasars; gravitational lensing; gravitational microlensing
Sunspot Observations at the Eimmart Observatory and in Its Neighborhood during the Late Maunder Minimum (1681-1718)

The Maunder Minimum (1645-1715; hereafter MM) is generally considered as the only grand minimum in the chronological coverage of telescopic sunspot observations. Characterized by scarce sunspot occurrences and their asymmetric concentrations in the southern solar hemisphere, the MM has frequently been associated with a special state of solar dynamo activity. As such, it is important to analyze contemporary observational records and improve our understanding of this peculiar interval, whereas the original records are frequently preserved in historical archives and can be difficult to access. In this study, we consult historical archives in the National Library of Russia, St. Petersburg, and analyze a series of sunspot observations conducted at the Eimmart Observatory from 1681 to 1709, which is the second-richest sunspot data set produced during the MM, following La Hire's series, among existing data sets. We have further extended our analyses to neighboring observations to extend our investigations up to 1718. We first analyze source documents and descriptions of observational instruments. Our analyses have significantly revised the existing data set, removed contaminations, and updated and labeled them as Eimmart Observatory (78 days), Altdorf Observatory (4 days), Hoffmann (22 days), and Wideburg (25 days). The revisions have updated the temporal coverage of the contemporary sunspot observations from 73.4% to 66.9% from 1677 to 1709. We have also derived the positions of the observed sunspot groups in comparison with contemporary observations. Our results indicate hemispheric asymmetry in the MM and recovery of sunspot groups in both hemispheres after 1716, supporting the common paradigm of the MM.

Keywords: maunder minimum; sunspot cycle; sunspot groups; sunspot number; solar activity; solar-terrestrial interactions
Detection of 2-4 GHz Continuum Emission from ɛ Eridani

The nearby star ɛ Eridani has been a frequent target of radio surveys for stellar emission and extraterrestrial intelligence. Using deep 2-4 GHz observations with the Very Large Array, we have uncovered a 29 μJy compact, steady continuum radio source coincident with ɛ Eridani to within 0"06 (≲2σ; 0.2 au at the distance of the star). Combining our data with previous high-frequency continuum detections of ɛ Eridani, our observations reveal a spectral turnover at 6 GHz. We ascribe the 2-6 GHz emission to optically thick, thermal gyroresonance radiation from the stellar corona, with thermal free-free opacity likely becoming relevant at frequencies below 1 GHz. The steep spectral index (α ≃ 2) of the 2-6 GHz spectrum strongly disfavors its interpretation as stellar-wind-associated thermal bremsstrahlung (α ≃ 0.6). Attributing the entire observed 2-4 GHz flux density to thermal free-free wind emission, we thus derive a stringent upper limit of 3 × 10-11 M⊙ yr-1 on the mass-loss rate from ɛ Eridani. Finally, we report the nondetection of flares in our data above a 5σ threshold of 95 μJy. Together with the optical nondetection of the most recent stellar maximum expected in 2019, our observations postulate a likely evolution of the internal dynamo of ɛ Eridani.

Keywords: stellar coronae; k stars; radio continuum emission; stellar atmospheres
A Fast and Accurate Analytic Method of Calculating Galaxy Two-point Correlation Functions

We have developed a new analytic method to calculate the galaxy two-point correlation functions accurately and efficiently, applicable to surveys with finite, regular, and mask-free geometries. We have derived simple, accurate formulas of the normalized random-random pair counts RR as functions of the survey area dimensions. We have also suggested algorithms to compute the normalized data-random pair counts DR analytically. With all edge corrections fully accounted for analytically, our method computes RR and DR with perfect accuracy and zero variance in O(1) and O(Ng) time, respectively. We test our method on a galaxy catalog from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulation. Our method calculates RR + DR at a speed 3-6 orders of magnitude faster than the brute-force Monte Carlo method and 2.5 orders of magnitude faster than tree-based algorithms. For a galaxy catalog with 10 million data points in a cube, this reduces the computation time to under 1 minute on a laptop. Our analytic method is favored over the traditional Monte Carlo method whenever applicable. Some applications in the study of correlation functions and power spectra in cosmological simulations and galaxy surveys are discussed. However, we recognize that its applicability is very limited for realistic surveys with masks, irregular shapes, and/or weighted patterns.

Keywords: two-point correlation function; large-scale structure of the universe; algorithms
Velocity Acoustic Oscillations on Cosmic Dawn 21 cm Power Spectrum as a Probe of Small-scale Density Fluctuations

We investigate the feasibility of using the velocity acoustic oscillations (VAO) features on the Cosmic Dawn 21 cm power spectrum to probe small-scale density fluctuations. In the standard cold dark matter (CDM) model, Population III stars form in minihalos and affect the 21 cm signal through Lyα and X-ray radiation. Such a process is modulated by the relative motion between dark matter and baryons, generating the VAO wiggles on the 21 cm power spectrum. In the fuzzy or warm dark matter models for which the number of minihalos is reduced, the VAO wiggles are weaker or even fully invisible. We investigate the wiggle features in the CDM with different astrophysical models and in different dark matter models. We find that (1) in the CDM model the relative streaming velocities can generate the VAO wiggles for broad ranges of parameters f *, ζ X , and f esc,LW ζ LW, though for different parameters the wiggles would appear at different redshifts and have different amplitudes. (2) For the axion model with m a ≲ 10‑19 eV, the VAO wiggles are negligible. In the mixed model, the VAO signal is sensitive to the axion fraction. For example, the wiggles almost disappear when f a ≳ 10% for m a = 10‑21 eV. Therefore, the VAO signal can be an effective indicator for small-scale density fluctuations and a useful probe of the nature of dark matter. The Square Kilometre Array-low with ∼2000 hr observation time has the ability to detect the VAO signal and constrain dark matter models.

Keywords: reionization; h i line emission; population iii stars; cold dark matter; warm dark matter; large-scale structure of the universe; intergalactic medium
Powerful Radio Sources in the Southern Sky. II. A Swift X-Ray Perspective

We recently constructed the G4Jy-3CRE, a catalog of extragalactic radio sources based on the GLEAM 4-Jy (G4Jy) sample, with the aim of increasing the number of powerful radio galaxies and quasars with similar selection criteria to those of the revised release of the Third Cambridge Catalog (3CR). The G4Jy-3CRE consists of a total of 264 radio sources mainly visible from the Southern Hemisphere. Here, we present an initial X-ray analysis of 89 G4Jy-3CRE radio sources with archival X-ray observations from the Neil Gehrels Swift Observatory. We reduced a total of 624 Swift observations, for about 0.9 Ms of integrated exposure time. We found X-ray counterparts for 59 radio sources belonging to the G4Jy-3CRE, nine of them showing extended X-ray emission. The remaining 30 sources do not show any X-ray emission associated with their radio cores. Our analysis demonstrates that X-ray snapshot observations, even if lacking uniform exposure times, as those carried out with Swift, allow us to (i) verify and/or refine the host galaxy identification; (ii) discover the extended X-ray emission around radio galaxies of the intracluster medium when harbored in galaxy clusters, as the case of G4Jy 1518 and G4Jy 1664; and (iii) detect X-ray radiation arising from their radio lobes, as for G4Jy 1863.

Keywords: radio active galactic nuclei; radio jets; radio lobes; radio loud quasars; galaxy clusters; galactic and extragalactic astronomy; x-ray surveys; surveys
Speckle Holography of Visual Double Stars at the 2.1 m Telescope of OAN-SPM: First Results

We present our first results of multiband Speckle Holography of components of visual double stars. The observations were performed during 2019 April at the 2.1 m telescope at the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir (México). We have observed 190 double stars with separation between 3″ and 5″. The position angle, separation and magnitude difference in three broadband optical filters (VRI) for these systems are provided. For 15 systems we found different interesting features, we have identified a close component for 9 of those systems; 5 of them are newly discovered. In the remaining 6 systems, although unresolved, we found elongations that we have been able to derive astrometric parameters if proven to be a (newly discovered) close component. This corresponds to about 8% of the sample presenting a certain feature in one of the components and about 5% of the sample having a confirmed close component.

Keywords: binary stars; holographic interferometry; astronomical techniques
Theoretical Study of the State-resolved Thermal Rate Constants for the Astrophysical Reaction Li + HD+ (V = 0, 1)

In the present study, we use the time-dependent wave packet (TDWP) method to calculate the thermal rate constants for the reaction Li + HD+(V = 0, 1) → LiH/LiD + H+/D+ in the temperature range of 200-5000 K on the potential energy surface constructed by Martinazzo et al. Total rate constants for both the V = 0 and V = 1 reactions exhibit simple Arrhenius behavior and are compared with previous isotope reactions. Total rate constants for V = 1 are several times larger than those of V = 0, particularly in the low-temperature region. For the two channels of the reaction, the vibrational excitation of HD+ greatly promotes the formation rate of the products LiH and LiD. For V = 0, the rate constants of LiH and LiD are comparable, while for V = 1, the rate constants of LiH are more than two times larger than those of LiD. The state-resolved rate constants show that the products LiH and LiD molecules can be excited to higher vibrational states and are preferably formed with hotter rotational states when the reactant HD+ is vibrationally excited. Applications of these rate constants in the modeling of the astrophysical sources are discussed.

Keywords: abundance ratios; early universe; recombination (cosmology); theoretical models; galaxies
Auroras on Planets around Pulsars

The first extrasolar planets were discovered serendipitously, by finding the slight variation in otherwise highly regular timing of the pulses, caused by the planets orbiting a millisecond pulsar. In analogy with the solar system planets, we predict the existence of aurora on planets around millisecond pulsars. We perform the first magnetohydrodynamic simulations of magnetospheric pulsar-planet interaction and estimate the radio emission from such systems. We find that the radio emission from aurora on pulsar planets could be observable with the current instruments. We provide parameters for such a detection, which would be the first radio detection of an extrasolar planet. In addition to probing the atmosphere of planets in such extreme conditions, of great interest is also the prospect of the first direct probe into the pulsar wind.

Keywords: pulsar planets; magnetohydrodynamics; aurorae
Research on the Optimal Design of the High-stability Optical System for Atmospheric Spectra in Transit Observation

Capturing the characteristics of exoplanetary atmospheres (CEA) through transit spectroscopy (TS) holds profound implications for our understanding of planetary formation and evolution. However, TS, the method employed for detecting CEA, indirectly extracts these characteristics from the subtle variations in stellar spectra during the transit process, necessitating a high level of observational stability in optical instrumentation. To mitigate observational errors in spectral energy within the optical system, this dissertation delves into the optimal design of a high-stability optical system tailored for atmospheric spectra in transit observations. Initially, a theoretical model of transit signal-to-noise ratios (S/Ns) catered to the EAC retrievals is formulated based on transit observation strategies. Subsequently, the optimal parameters and design approach for the optical system are explored through an analysis of the optical factors influencing S/N. Leveraging an observation simulator for optical instruments, the detection feasibility of the optimized optical system for capturing CEA is validated.

Keywords: transit instruments; spectrometers; infrared telescopes; astronomical simulations; exoplanet atmospheric composition
MASTER OT J030227.28+191754.5: A Dwarf Nova at a Massive Oxygen-Neon White Dwarf System?

We present timing and spectral analysis results of the NICER and NuSTAR observations of the dwarf nova MASTER OT J030227.28+191754.5 during the 2021-2022 outburst. The soft X-ray component was found to be dominated by blackbody radiation with a temperature of ~30 eV and also showed prominent oxygen and neon emission lines. The blackbody luminosity exceeded 1034 erg s-1, which is consistent with theoretical predictions, and then decreased more than an order of magnitude in 3.5 days. The inferred abundances of oxygen and neon in the optically thin coronal region surrounding the central white dwarf (WD) are several times higher than the respective solar values. Although inconclusive, the abundance enrichment may originate from the WD, indicating that it may be mainly composed of oxygen and neon. Assuming that the blackbody radiation comes from the belt-shaped boundary layer between the WD and the accretion disk, we estimated the WD radius to be (2.9 ± 1.1) × 108 cm, which corresponds to the WD mass range of 1.15-1.34 M ⊙. If the accretion continues for another ~1 Gyr, the WD may experience an accretion-induced collapse into a neutron star and form a so-called black widow pulsar system.

Keywords: dwarf novae; x-ray sources; stellar accretion disks; cataclysmic variable stars; wz sagittae stars
Examination of Fragment Species in the Comae of Several Comets Using an Integral Field Unit Spectrograph

Spectra of the comae of four comets were obtained with an integral field unit spectrograph on the Harlan J. Smith Telescope at McDonald Observatory. The passband of the spectrograph permitted the observation of C2, C3, CH, CN, and NH2 transitions for these comets. The classical Haser model was used to derive production rates for each observed species. The production rates obtained for the comets were also used to obtain mixing ratios relative to CN. The relative abundances with respect to CN obtained for these comets vary greatly, but are largely consistent with ranges established from prior comet chemistry surveys. The notable exception is 168P/Hergenrother, which the results suggest is extremely depleted in volatiles, even with respect to many other comets designated as volatile depleted in prior surveys. The results for comet Hergenrother add to a small, but growing, body of data suggesting that there may be a subgroup of carbon-chain-depleted Jupiter-family comets that are also depleted in ammonia.

Keywords: comets; comae; neutral coma gases; molecular spectroscopy
Advancing Solar Energetic Particle Event Prediction through Survival Analysis and Cloud Computing. I. Kaplan–Meier Estimation and Cox Proportional Hazards Modeling

Solar energetic particles (SEPs) pose significant challenges to technology, astronaut health, and space missions. This initial paper in our two-part series undertakes a comprehensive analysis of the time to detection for SEPs, applying advanced statistical techniques and cloud-computing resources to deepen our understanding of SEP event probabilities over time. We employ a range of models encompassing nonparametric, semiparametric, and parametric approaches, such as the Kaplan–Meier estimator and Cox Proportional Hazards models. These are complemented by various distribution models—including exponential, Weibull, lognormal, and log-logistic distributions—to effectively tackle the challenges associated with "censored data," a common issue in survival analysis. Employing Amazon Web Services and Python's "lifelines" and "scikit-survival" libraries, we efficiently preprocess and analyze large data sets. This methodical approach not only enhances our current analysis, but also sets a robust statistical foundation for the development of predictive models, which will be the focus of the subsequent paper. In identifying the key determinants that affect the timing of SEP detection, we establish the vital features that will inform the machine-learning (ML) techniques explored in the second paper. There, we will utilize advanced ML models—such as survival trees and random survival forests—to evolve SEP event prediction capabilities. This research is committed to advancing space weather, strengthening the safety of space-borne technology, and safeguarding astronaut health.

Keywords: space weather; heliosphere; solar energetic particles; solar flares; cloud computing
BD+14°3061: A Luminous Yellow Post-AGB Star in the Galactic Halo

I report the discovery that the ninth-mag Galactic-halo star BD+14°3061 is a member of the rare class of luminous metal-poor "yellow post-AGB" stars. Its Gaia DR2 parallax implies an absolute magnitude of MV = -3.44 ± 0.27, and it is a very high-velocity star moving in a retrograde Galactic orbit. BD+14°3061 is a field analog of the half-dozen yellow PAGB stars known in Galactic globular clusters, which have closely similar absolute magnitudes. These objects are the visually brightest members of old stellar populations; their apparently narrow luminosity function makes them potentially useful as Population II standard candles. The spectral-energy distribution of BD+14°3061 out to 22 μm shows no evidence for circumstellar dust. The star is a low-amplitude semiregular pulsating variable, with typical periods of 30-32 days. A radial-velocity study suggests that it is a spectroscopic binary with a period of 429.6 days, making it similar to known binary yellow PAGB stars such as HD 46703 and BD+39°4926.

Keywords: post-asymptotic giant branch stars; evolved stars; globular star clusters; spectroscopic binary stars; semi-regular variable stars