Sazuna/UAT_keywords huggingface dataset:
Research on High-Precision Radial Velocity Retrieval Method Using an Individual Narrow Spectral Line Based on CODES. The coherent-dispersion spectrometer (CODES) for exoplanet detection relies on the radial velocity (RV) method, detecting exoplanets by measuring the Doppler shifts in the stellar spectrum. The CODES utilizes a novel asymmetric designed Sagnac interferometer, which amplifies the minute wavelength shifts caused by Doppler shifts, converting them into more sensitive phase variations of the interference fringes. To investigate the detection capability of an individual spectral line on CODES, this paper develops a new RV retrieval algorithm MOST (Maximum likelihood estimation Optimized via Sequential quadratic programming and Tuna search optimization), which is based on the relationship between photon arrival probability and interference fringes and incorporates the statistical characteristics of photon Poisson distribution to achieve parameter estimation. The zero-finding problem in the Maximum Likelihood Estimation (MLE) is transformed into an optimization problem. Further, the Tuna Search Optimization algorithm and Sequential Quadratic Programming algorithm are utilized to solve the unknown model parameters in the MLE. The Monte Carlo simulation results demonstrate that under a noise-free environment, the RV retrieval precision for an individual spectral line can reach a level below 0.1 m s−1. In the presence of noise, the retrieval precision can maintain within 1.0 m s−1 when the signal-to-noise ratio reaches 92.4 for absorption line, and 85.7 for emission line. Further laser Doppler shift experiments on CODES show an average absolute error of −0.27 m s−1. This study provides the first RV detection capability of CODES with an individual line, offering valuable theoretical guidance and technical reference for the design of high-precision RV measurement methods and high-resolution astronomical spectrometers.

Keywords: Radial velocity, Stellar spectral lines
Integrated Collision-aware Target Assignment and Motion Planning for Fiber Positioners in Multi-object Spectrographs. Large-scale spectroscopic surveys rely on thousands of densely packed fiber positioners to reconfigure between fields, where overlapping workspaces introduce a risk of mechanical collisions. Existing approaches typically separate target assignment from collision avoidance, leading to suboptimal performance, while real-time collision detection remains computationally expensive. In this work, we present an integrated framework for collision-aware field reconfiguration that combines three key innovations. First, a collision-aware target assignment strategy is introduced to minimize potential conflicts during allocation. Second, a segmented motion planning approach based on safety zones is developed to guide positioners through collision-free trajectories under dense packing conditions. Third, a lightweight real-time collision detection algorithm monitors deviations with low computational overhead. The framework is evaluated using a configuration modeled on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope. Simulation results demonstrate that the proposed method decreases collision incidence by a factor of 2─10 while maintaining target allocation efficiency. The framework is readily applicable to other θ─φ fiber positioning systems, offering a practical and hardware-independent solution to enhance survey performance.

Keywords: Astronomical instrumentation, Algorithms, Spectroscopy
Inferring Neutron Star Merger Ejecta Morphology with Kilonovae. In this study we incorporate a new grid of kilonova simulations produced by the Monte Carlo radiative transfer code SuperNu in an inference pipeline for astrophysical transients and evaluate their performance. These simulations contain four different two-component ejecta morphology classes. We analyze follow-up observational strategies by Vera Rubin Observatory in optical and James Webb Space Telescope (JWST) in mid-infrared (MIR). Our analysis suggests that, within these strategies, it is possible to discriminate between the four different morphologies only when late-time JWST observations in MIR are available. We conclude that follow-ups by the new Vera Rubin Observatory alone are not sufficient to determine ejecta morphology. Additionally, we make comparisons between surrogate models based on radiative transfer simulation grids by SuperNu and POSSIS, by analyzing the historic kilonova AT2017gfo that accompanied the gravitational wave event GW170817. We show that both SuperNu and POSSIS models provide similar fits to photometric observations but their qualitative interpretations differ.

Keywords: Neutron stars, R-process, Transient detection, Radiative transfer simulations, Support vector machine
Optimizing Ground-layer Turbulence Prediction Using an Instrumented Drone. Predicting atmospheric and turbulence conditions has become increasingly crucial for the astronomical community and free-space optical communications. With the advent of the next generation of extremely large telescopes, accurate forecasts of atmospheric conditions several hours before observations are essential. Similarly, in free-space optical communications, the propagation of optical signals is strongly influenced by atmospheric conditions and optical turbulence, leading to signal degradation. To address these challenges, a numerical approach combining the Weather Research and Forecasting model and optical turbulence models has been applied to predict turbulence above the Calern site at the Côte d'Azur Observatory in France. While the results have been promising, limitations remain in accurately predicting properties within the atmospheric ground layer. To enhance the prediction in the ground layer, we implemented an optimization process using a drone equipped with instruments to measure meteorological parameters, including pressure, temperature, humidity, and wind. These in situ measurements enable the acquisition of vertical profiles of meteorological parameters with high temporal and spatial resolution in the lower atmosphere. The gathered data have been used to refine the initial conditions of the simulations, leading to an improvement in turbulence prediction.

Keywords: Optical observation, Planetary boundary layers, Astronomical optics, Atmospheric refraction, Astronomical instrumentation, Atmospheric effects, Astronomical location
FOSSIL. IV. The Significance-convergence Test—An Algorithm for Selecting Reliable Rotation Periods of Small Solar System Bodies. Manual review to select a reliable rotation period of small solar system bodies (SSSBs) is a very time-consuming process. With the growing volume of lightcurve data collected by wide-field, high-cadence surveys, such manual inspection has become impractical and unsustainable. In response to this challenge, we present a new algorithm, called the significance-convergence test, which provides a quantitative way to select reliable rotation periods of SSSBs obtained from these wide-field, high-cadence surveys. This algorithm was developed based on two simulations, each containing 162,000 synthetic lightcurves generated according to the observational conditions and data properties of the surveys from the phase I of the Formation of the Outer Solar System: an Icy Legacy (FOSSIL I) and Pan-STARRS 1 (PS1). Using two parameters extracted from period analysis, the successful recoveries of the input rotation periods from the synthetic lightcurves can be distinguished from unsuccessful recoveries and noisy lightcurves. The first parameter, 1/S, indicates the significance of the best-fit spin rate, while the second parameter, C, represents the condition of convergence of the best-fit lightcurve. This algorithm can also be used as a mapping to the conventional quality code of manual review, U, defined by Warner et al. The significance-convergence test thus provides a practical alternative to manual review, which is a time-consuming and biased process.

Keywords: Period determination, Small Solar System bodies, Wide-field telescopes, Surveys, Light curves, Period search , Time series analysis
Validating the On-axis Point Spread Function Reconstruction for Keck Adaptive Optics. The largest telescopes (8─10 m) in the world regularly deploy adaptive optics (AO) systems utilizing natural and laser guide stars in tandem with deformable mirrors to correct the turbulent effects of the atmosphere and obtain Point Spread Functions (PSF) with Full Width at Half Maximum (FWHM) of less than 100 mas. While classical techniques seek to extract the PSF from the images, reconstructing the PSF from first principles will allow resolving high angular resolution phenomena in the absence of an unresolved point source in the science field. We use PRIME, a python package for PSF reconstruction and modelling to forward model the PSFs for NIRC2 data from the Keck II telescope's AO system. We also use PRIME to fit the PSFs to a Fourier model and compare the performance between the two approaches by considering the Strehl, FWHM and the Fraction of Variance Unexplained. We then discuss the implications of our analysis for the upcoming Keck All-sky Precision Adaptive Optics upgrade on the Keck I telescope.

Keywords: Laser guide stars, Astronomical instrumentation, Infrared telescopes, Algorithms, Photographic astrometry
The Reset Switch Charge Decay Effect in JWST/MIRI Observations. Blocked impurity band arsenic-doped silicon detectors such as those used in the James Webb Space Telescope's Mid-Infrared Instrument were invented in the 1980s to overcome many of the unwanted second-order effects found in the photoconductor detectors of that era. However, simply by virtue of operating the detectors at deep cryogenic temperatures (&lt;10 K), non-ideal effects become inevitable, especially in the silicon readout integrated circuits that are hybridized with these detectors. Here, we describe a nonlinearity we have dubbed the Reset Switch Charge Decay effect. We discuss the physical origin and show the impact on both laboratory and flight data. Initial mitigation strategies show promise but are complicated by the fact that the magnitude of the effect depends on both the fluence and the flux of the incident signal, and the decay time appears to be readout speed dependent.

Keywords: Calibration, Astronomical instrumentation, Infrared photometry
Modeling the Environmental Drift of High Resolution Spectrographs to Enhance the RV Precision. We present a study of the instrumental drift in two high-resolution spectrographs for stellar radial velocity measurements. We use a simple model that allows one to calculate the expected drift from the measurements of temperature, pressure, and humidity of the atmosphere. By comparing the real drift with the predictions of the model, we can identify and possibly correct instabilities in the instruments produced by effects other than the atmosphere. The method allows us to improve the control of the instruments and to enhance the radial velocity performances of those instruments, which do not include simultaneous wavelength calibration. By applying this method, we measure improvements in radial velocity precision for PUCHEROS+ from 30 to 15 m s−1, and obtain a limiting radial velocity precision of 7 m s−1 in PLATOSpec.

Keywords: High resolution spectroscopy, Radial velocity, Exoplanets, Spectroscopy
The Roman Space Telescope as a Planetary Defense Asset. NASA's Nancy Grace Roman Space Telescope, slated to launch in 2026 October, will serve a critical role in the characterization and threat assessment of near-Earth Objects (NEOs), thus contributing to national and international planetary defense objectives. Operating from the Earth─Sun L2 point and observing in the near-infrared, Roman has the high sensitivity and high spatial resolution needed to measure the physical properties, compositions, and orbital trajectories of NEOs in order to understand their physical nature and potential hazards to Earth. Roman's planetary defense capabilities complement those of two wide-field survey missions: the now operational ground-based Vera C. Rubin Observatory's Legacy Survey of Space and Time and the upcoming space-based NEO Surveyor. Rubin, observing in visible light, will discover over 100,000 NEOs. NEO Surveyor, observing in the mid-infrared where NEO thermal emission peaks, will detect 200,000─300,000 NEOs, some as small as ∼20 m in diameter. With investment in developing the pipeline infrastructure required to extract information from moving target streaks, Roman will be able to observe NEOs down to the smallest sizes in order to improve our measurements of NEO orbits by 2─3 orders of magnitude, enable accurate diameter and albedo estimates in conjunction with NEO Surveyor, and reveal the spectral types and bulk compositions of the smallest NEOs. Together, these three US-led facilities will operate across the electromagnetic spectrum to form a comprehensive planetary defense network.

Keywords: Space telescopes, Near-Earth objects, Sky surveys, Surveys
AGN-Host Galaxy Image Decomposition with JWST: Limitations of Sérsic Profile Models. The ability to disentangle the light of an AGN from its host galaxy is strongly dependent on the spatial resolution and depth of the imaging. As the capabilities of imaging systems improve with time, confirming that our standard techniques adequately model the increasingly complex structures unveiled is essential. With JWST providing unprecedented image quality, we can test how measurements of galaxy morphology vary with the choice of point-spread function (PSF) and fitting software. We perform two-component Sérsic+PSF fits of the surface brightness profiles of 87 X-ray AGNs (0.1 &lt; z &lt; 4) from the CEERS survey. We create model PSFs for NIRCam F115W imaging using both PHOTUTILS and PSFEX. We find that PSFEx models consistently fail to match the radial profile of typical point sources within our sample. We then perform AGN─host decompositions on each source by creating Sérsic+PSF models using both GALFIT and ASTROPHOT. We find that GALFIT and ASTROPHOT converge to different regions of the parameter space, providing consistently differing host galaxy properties. While we can measure the AGN and host magnitudes accurately, we find that the host galaxy morphological parameters are not well-determined—the Sérsic index and effective radius are strongly covariant. Significant changes in the host galaxy parameters do not correspond to changes in the statistical quality of fit, nor to significant changes in the model's radial profile. These results indicate that the Sérsic profile does not uniquely well-represent typical AGN host galaxies in extragalactic survey fields. We also provide recommendations for studies of AGN hosts comparable to ours.

Keywords: AGN host galaxies, Active galaxies, Galaxy classification systems, Active galactic nuclei, Galaxies
Photometric Constraints on Intermediate-mass Black Holes in the Galactic Centre. JWST/MIRI observations can place photometric limits on the presence of an intermediate-mass black hole (IMBH) near the Galactic Centre. The stellar complex IRS 13E, a co-moving conglomerate of young and massive stars, is a prime location to study because it has been speculated to be bound by an IMBH. Assuming a standard radiatively inefficient accretion flow (RIAF) and a minimum fractional variability of 10% of the intrinsic luminosity, the wavelength of peak emission in the spectral energy distribution for an IMBH would lie in the mid-infrared (∼5─25 μm), and the variability would be detectable in MIRI time-series observations. Monitoring fails to detect such variable emission (other than from Sgr A*) in and around the IRS 13E complex, and upper limits on a putative IMBH's intrinsic variability on timescales of minutes to ∼1 hr are ≲ 1 mJy at 12 μm and ≲2 mJy at 19 μm. These translate to luminosities ≲ 25 × 1032 erg s−1. The resulting limits on the IMBH mass and accretion rate rule out any IMBH with mass ≳103 M⊙ accreting at ≳10−6 times Eddington rate at the location of IRS 13E. Further, the observations rule out an IMBH anywhere in the central 6″ × 6″ region that is more massive than ≍ 2 × 103 M⊙ and accreting at ≥10−6 of the Eddington rate. Assuming Bondi accretion scaled to typical RIAF-accretion efficiencies, albeit somewhat uncertain, also allows us to rule out IMBHs moving with typical velocities ∼200 km s−1 and masses ≳ 2 × 103 M⊙. These methods showcase the effectiveness of photometric variability measurements in constraining the presence of accreting black holes in Galactic centre-like environments.

Keywords: Supermassive black holes, Galactic center, Time domain astronomy
Artificial Broadcasts as Galactic Populations: III. Constraints on Radio Broadcasts from the Cosmic Population of Inhabited Galaxies. Any population of artificial radio broadcasts in a galaxy contributes to its integrated radio luminosity. If this radio emission is bright enough, inhabited galaxies themselves form a cosmic population of artificial radio galaxies. We can detect these broadcasts individually or set constraints from their collective emission. Using the formalism in Papers I and II, I set bounds on the artificial radio galaxy population using both of these methodologies. Measured radio source counts set limits on radio broadcasts across the radio spectrum, including the first Search for Extraterrestrial Intelligence (SETI) constraints at ∼250 GHz. I compare these with commensal limits from background galaxies in the fields of large SETI surveys. The field limits are more powerful, but generally only over a limited luminosity range and for frequencies with dedicated SETI surveys. The limits are weaker when broadcasts clump into discrete hosts that are themselves extremely rare. I find that the abundance of Kardashev Type III radio broadcast populations is less than one in 1017 stars, about one in a million large galaxies. I also examine limits for a power-law distribution in broadcast luminosity.

Keywords: Extragalactic radio sources, Technosignatures, Spatial point processes, Radio source counts, Search for extraterrestrial intelligence
Attributing the Supernova Remnant RCW 89 to the Jittering Jets Explosion Mechanism. I examine recent radio observations of the supernova remnant (SNR) RCW 89 and identify a point-symmetric morphology composed of two main symmetry axes. I attribute this morphology to a jet-driven explosion in the framework of the jittering jets explosion mechanism (JJEM). To reach this conclusion, I argue that the MSH 15-52 nebula associated with the pulsar PSR B1509-58, the X-ray hand-like-shaped nebula, and RCW 89 are two separate core-collapse supernova (CCSN) remnants that interact with each other. Namely, the nebula SNR G320.4-1.2 contains two CCSN remnants (CCSNRs). In essence, I utilize the recent successes of the JJEM to account for the morphologies of point-symmetric CCSNRs, thereby explaining the morphology of RCW 89 and identifying it as a separate CCSNR. I suggest a process by which somewhat more energetic pairs of jets in the JJEM have a positive feedback on the accreted gas onto the newly born neutron star, thereby prolonging the life of the jets and explaining the occurrence of two or three energetic pairs of jets in some CCSNe. This study adds RCW 89 to the growing list of point-symmetric CCSNRs. The JJEM naturally explains these morphologies as shaped by misaligned pairs of jets that exploded these CCSNe.

Keywords: Supernova remnants, Stellar jets, Massive stars, Core-collapse supernovae
Serendipitous Discovery of a Faint Planetary Nebula in the Massive Young LMC Cluster NGC 1866. During an integral-field spectroscopic study of stars in the massive young open cluster NGC 1866 in the Large Magellanic Cloud, we serendipitously discovered a faint planetary nebula (PN). We designate it "Ka LMC 1," and find that its location near the cluster center, along with the agreement of its radial velocity with that of the cluster, imply a high probability of membership in NGC 1866. The 200 Myr age of the cluster indicates that the PN's progenitor star had an initial mass of about 3.9 M⊙. The integrated spectrum of Ka LMC 1 shows strong emission lines of [N II], consistent with it being a "Type I" nitrogen-rich PN. The nebula exhibits a classical ring morphology, with a diameter of ∼6″, corresponding to an advanced expansion age of about 18,000 yr. Archival images of NGC 1866 obtained with the Hubble Space Telescope reveal a faint blue central star. Comparison of the star's luminosity with predictions from one set of theoretical post-asymptotic-giant-branch evolutionary tracks (for single stars) implies an age roughly consistent with the dynamical age of the PN, but the agreement with alternative modern tracks is much poorer. Analysis of the emission-line spectrum suggests considerable dust extinction within the nebula; however the central star possibly suffers little reddening because we may be viewing it nearly pole-on in a bipolar PN. Our accidental discovery was made using data that are not ideal for study of Ka LMC 1; we suggest several avenues of future targeted studies that would provide valuable and nearly unique new information for constraining models of late stellar evolution.

Keywords: Post-asymptotic giant branch stars, Late stellar evolution, Planetary nebulae nuclei, Planetary nebulae, Open star clusters
BSN. IV. The First Multiband Light Curve Study of Five W UMa-type Contact Binary Systems. In this work, we present a detailed investigation of five contact binary systems of the W Ursae Majoris (W UMa) type. Multiband photometric observations were conducted using ground-based telescopes in both the northern and southern hemispheres, yielding new times of minima. O − C diagram analysis reveals that two systems exhibit parabolic trends, indicating a gradual long-term decrease in their orbital periods. The light curves were modeled using version 1.0 of the BSN application, with one system requiring the inclusion of a cool starspot to achieve a satisfactory fit. We examined empirical relationships between orbital period and fundamental parameters, identifying the period─semimajor axis (P─a) relation as the most robust correlation, which was used to estimate absolute parameters. To statistically assess thermal equilibrium, we analyzed temperature differences between components and found that 90% of systems exhibit less than 9.4% contrast. Two target systems with extremely low mass ratios were identified, and their orbital stability was evaluated. Based on the effective temperatures and component masses, two systems were classified as W-subtype and three as A-subtype. The evolutionary status of the binaries was assessed through their locations in mass─radius, mass─luminosity, and other empirical diagrams, and initial component masses as well as total mass loss were also estimated.

Keywords: Eclipsing binary stars, Astronomy data analysis, Fundamental parameters of stars