Sazuna/UAT_keywords huggingface dataset:
Addressing Distribution Discrepancies in Pulsar Candidate Identification via Bayesian-neural-network-based Multimodal Incremental Learning. With the advancement of astronomical observation technology and the substantial increase in data volume, traditional methods for pulsar identification are increasingly challenged by the dynamic nature of data distributions. To address this, our study introduces a multimodal incremental learning approach utilizing Bayesian neural networks. This method enables the model to adapt to new data distributions while preserving the knowledge of previous data. In our experiments, we utilized pulsar data sets from two telescopes and compared our new method with traditional techniques. The research results demonstrate that our method performs comparably to traditional methods across all evaluation metrics, while showing a significant improvement in handling data distribution discrepancy, with the F1-score increasing from approximately 70% to over 95%. Specifically, our model achieved an accuracy of 97.93%, a recall of 96.13%, and an F1-score of 97.02% under conditions of distributional disparities. These findings not only confirm the model's capability to adapt to dynamic data environments but also effectively address the challenges of data distribution discrepancy, significantly enhancing the predictive accuracy of pulsar identification in the context of evolving and variable radio frequency interference environments.

Keywords: Astronomy data modeling, Astronomical object identification, Convolutional neural networks, Astronomy data analysis, Pulsars, Radio pulsars
Twinkle: A GPU-based Binary-lens Microlensing Code with the Contour Integration Method. With the rapidly increasing rate of microlensing planet detections, microlensing modeling software faces significant challenges in computation efficiency. Here, we develop the Twinkle code, an efficient and robust binary-lens modeling software suite optimized for heterogeneous computing devices, especially GPUs. Existing microlensing codes have the issue of catastrophic cancellation that undermines the numerical stability and precision, and Twinkle resolves them by refining the coefficients of the binary-lens equation. We also devise an improved method for robustly identifying ghost images, thereby enhancing computational reliability. We have advanced the state of the art by optimizing Twinkle specifically for heterogeneous computing devices by taking into account the unique task and cache memory dispatching patterns of GPUs, while the compatibility with the traditional computing architectures of CPUs is still maintained. Twinkle has demonstrated an acceleration of approximately 2 orders of magnitude (≳102×) on contemporary GPUs. The enhancement in computational speed of Twinkle will translate to the delivery of accurate and highly efficient data analysis for ongoing and upcoming microlensing projects. Both GPU and CPU versions of Twinkle are open-source and publicly available.

Keywords: Gravitational microlensing exoplanet detection, Open source software, Binary lens microlensing, Finite-source photometric effect, GPU computing
Bayesian Approach to Equipartition Estimation of Magnetic Field Strength. Magnetic fields, together with cosmic rays (CRs), play an important role in the dynamics and evolution of galaxies, but are difficult to estimate. Energy equipartition between magnetic fields and CRs provides a convenient way to approximate magnetic field strength from radio observations. We present a new approach for calculating the equipartition magnetic field strength based on Bayesian methods. In this approach, the magnetic field is a random variable that is distributed according to a posterior distribution conditional on synchrotron emission and the size of the emitting region. It allows for the direct application of the general formulas for total and polarized synchrotron radiation without the need to invert these formulas, which has limited the equipartition method to highly simplified cases. We have derived the equipartition condition for the case of different low-energy breaks, slopes, and high-energy cutoffs of power-law spectra of the CR proton and electron distributions. The derived formalism was applied in the general case of a magnetic field consisting of both uniform and randomly oriented field components. The applied Bayesian approach naturally provides the uncertainties in the estimated magnetic field strengths resulting from the uncertainties in the observables and the assumed values of the unknown physical parameters. In the examples presented, we used two different Markov Chain Monte Carlo methods to generate the posterior distribution of the magnetic field. We have also developed a web application called BMAG that implements the described approach for different models and observational parameters of real sources.

Keywords: Galaxy magnetic fields, Bayesian statistics, Magnetic fields, Supernova remnants, Bayes' Theorem, Radio continuum emission, Radio astronomy, Cosmic rays
Hinode EIS: Updated In-flight Radiometric Calibration. We present an update to the in-flight radiometric calibration of the Hinode Extreme Ultraviolet Imaging Spectrometer (EIS), revising and extending our previous studies. We analyze full-spectral EIS observations of quiet Sun (QS) and active regions (ARs) from 2007 until 2022. Using CHIANTI version 10, we adjust the EIS relative effective areas for a selection of dates with emission measure analyses of off-limb QS. We find generally good agreement (within typically ±15%) between measured and expected line intensities. We then consider selected intensity ratios for all of the dates and apply an automatic fitting method to adjust the relative effective areas. To constrain the absolute values from 2010 and later, we force agreement between EIS and Solar Dynamics Observatory Atmospheric Imaging Assembly 193 Å observations. The resulting calibration, with an uncertainty of about ±20%, is then validated in various ways, including flare line ratios from Fe XXIV and Fe XVII, emission measure analyses of cool AR loops, and several density-dependent line ratios.

Keywords: Calibration, The Sun, Solar extreme ultraviolet emission
Improving H2RG Performance in SPHEREx Brassboard Model. Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer is an upcoming NASA satellite mission to study the physics of inflation, the history of galaxy formation, and the abundance of biogenic ices in the Milky Way, obtaining the first all-sky spectroscopic survey at infrared wavelengths 0.75–5.0 μm. The instrument implements HAWAII-2RG (H2RG) detectors and custom-built Video8 electronics with multiple sampling features to optimize the H2RG noise performance, including nonsequential row reads, voltage monitoring, multiple visits to optically dark reference pixels, as well as onboard slope fitting and cosmic-ray removal. We report here the performance of a single H2RG with the readout electronics. We focus on the effectiveness of multiple reference samplings to reduce 1/f noise most relevant to the galaxy formation analysis, in particular the noise on large angular scales k &lt;0.13 [pix‑1] (∼5″–20″) where the imprints of galaxy clustering will be measured. Our characterization confirms that increased sampling of reference pixels successfully reduces the 1/f noise by ∼50% at these scales. However, the effectiveness of multiple reference reads is limited by irreducible per-pixel telegraph noise. Further noise reduction can be achieved by using optical pixels in addition to the reference pixels to remove common-mode signal offsets in each channel. Additionally, we observe that the gain of optical pixels is consistently ∼90% that of the reference pixels, prompting additional correction steps in the data reduction pipeline.

Keywords: Space telescopes, Astronomical detectors, Astronomical instrumentation, Near infrared astronomy
Magnetic Activity of TESS Objects Observed in the LAMOST Medium-resolution Spectral Survey. A combination of spectroscopic and photometric observations provides an excellent data sample for studying stellar chromospheric activity. We have combined LAMOST medium-resolution spectra with TESS 2 minute light curves and extracted over 530,000 spectra and 110,000 light curves from more than 40,000 stars. We have quantified the Hα line intensity in each spectrum and found that 38,659 spectra from 7002 stars exhibited excess Hα emission and that the intensity of stellar chromospheric activity increases with later spectral types. We also discovered that the boundary value between the saturated and unsaturated regions of chromospheric activity for different spectral type stars is around Ro = 0.1. By analyzing the TESS light curves, we identified 31,539 flare events from 4120 stars. Through these flare events, we determined that the flare-frequency proportion of stars increases with later spectral types. We have found that the power-law index of the flare-frequency distribution for F-, G-, K-, and M-type stars is around 2.0, while that for A-type stars is 1.3. Additionally, we observed that the amplitude of brightness variations caused by modulation due to starspot coverage (Reff) is positively correlated with both the flare intensity and intensity of chromospheric activity and that the chromospheric activity was generally stronger in flare stars as compared to nonflare stars. We also found that within 300 pc, the proportion of chromospherically active stars and flare stars decreases with increasing distance from the Galactic disk. Finally, we discovered six flare events from the Hα variation and estimated their energies.

Keywords: Stellar chromospheres, Stellar flares, Stellar activity
Evaluation of the Single-component Thermal Dust Emission Model in Cosmic Microwave Background Experiments. It is well known that multiple Galactic thermal dust emission components may exist along the line of sight, but a single-component approximation is still widely used, since a full multicomponent estimation requires a large number of frequency bands that are only available with future experiments. In light of this, we present a reliable, quantitative, and sensitive criterion to test the goodness of all kinds of dust emission estimations. This can not only give a definite answer to the quality of current single-component approximations but also help determine preconditions of future multicomponent estimations. Upon the former, previous works usually depend on a more complicated model to improve the single-component dust emission; however, our method is free from any additional model, and is sensitive enough to directly discover a substantial discrepancy between the Planck High Frequency Instrument data (100–857 GHz) and associated single-component dust emission estimations. This is the first time that the single-component estimation is ruled out by the data itself. For the latter, a similar procedure will be able to answer two important questions for estimating the complicated Galactic emissions: the number of necessary foreground components and their types.

Keywords: Interstellar dust, Astronomy data modeling, Cosmic microwave background radiation, Cosmic inflation, Interstellar medium
Identification of 4876 Bent-tail Radio Galaxies in the FIRST Survey Using Deep Learning Combined with Visual Inspection. Bent-tail radio galaxies (BTRGs) are characterized by bent radio lobes. This unique shape is mainly caused by the movement of the galaxy within a cluster, during which the radio jets are deflected by the intracluster medium. A combined method, which involves a deep learning-based radio source finder along with visual inspection, has been utilized to search for BTRGs from the Faint Images of the Radio Sky at Twenty cm survey images. Consequently, a catalog of 4876 BTRGs has been constructed, among which 3871 are newly discovered. Based on the classification scheme of the opening angle between the two jets of the galaxy, BTRGs are typically classified as either wide-angle-tail (WAT) sources or narrow-angle-tail (NAT) sources. Our catalog comprises 4424 WATs and 652 NATs. Among these, optical counterparts are identified for 4193 BTRGs. This catalog covers luminosities in the range of 1.91 × 1020 ≤ L1.4 GHz ≤ 1.45 × 1028 W Hz−1 and redshifts from z = 0.0023 to z = 3.43. Various physical properties of these BTRGs and their statistics are presented. Particularly, by the nearest neighbor method, we found that 1825 BTRGs in this catalog belong to galaxy clusters reported in literature.

Keywords: Extragalactic radio sources, Active galactic nuclei, Radio galaxies, Radio astronomy
Metallicity Dependence of Giant Planets around M Dwarfs. We investigate the stellar metallicity ([Fe/H] and [M/H]) dependence of giant planets around M dwarfs by comparing the metallicity distribution of 746 field M dwarfs without known giant planets with a sample of 22 M dwarfs hosting confirmed giant planets. All metallicity measurements are homogeneously obtained through the same methodology based on the near-infrared spectra collected with a single instrument SpeX mounted on the NASA Infrared Telescope Facility. We find that (1) giant planets favor metal-rich M dwarfs at a 4σ─5σ confidence level, depending on the band of spectra used to derive metallicity; (2) hot (a/R*≤20) and warm (a/R* &gt; 20) Jupiters do not show a significant difference in the metallicity distribution. Our results suggest that giant planets around M and FGK stars, which are already known to prefer metal-rich hosts, probably have a similar formation channel. In particular, hot and warm Jupiters around M dwarfs may have the same origin as they have indistinguishable metallicity distributions. With the refined stellar and planetary parameters, we examine the stellar metallicities and the masses of giant planets where we find no significant correlation. M dwarfs with multiple giant planets or with a single giant planet have similar stellar metallicities. Mid-to-late type M stars hosting gas giants do not show an apparent preference to higher metallicities compared with those early M dwarfs with gas giants and field M dwarfs.

Keywords: M dwarf stars, Stellar properties, Astrostatistics, Spectroscopy, Metallicity, Extrasolar gaseous giant planets
Broad-line Region Characterization in Dozens of Active Galactic Nuclei Using Small-aperture Telescopes. We present the results of a nearly decade-long photometric reverberation mapping (PRM) survey of the Hα emission line in nearby (0.01 ≲ z ≲ 0.05) Seyfert galaxies using small (15–40 cm) telescopes. Broadband filters were used to trace the continuum emission, while narrowband filters tracked the Hα-line signal. We introduce a new PRM formalism to determine the time delay between continuum and line emission using combinations of auto- and cross-correlation functions. We obtain robust delays for 33/80 objects, allowing us to estimate the broad-line region (BLR) size. Additionally, we measure multiepoch delays for six objects whose scatter per source is smaller than the scatter in the BLR size–luminosity relation. Our study enhances the existing Hα size–luminosity relation by adding high-quality results for 31 objects, whose nuclear luminosities were estimated using the flux-variation gradient method, resulting in a scatter of 0.26 dex within our sample. The scatter reduces to 0.17 dex when the six lowest-luminosity sources are discarded, which is comparable to that found for the Hβ line. Single-epoch spectra enable us to estimate black hole masses using the Hα line and derive mass accretion rates from the iron-blend feature adjacent to Hβ. A similar trend, as previously reported for the Hβ line, is implied whereby highly accreting objects tend to lie below the size–luminosity relation of the general population. Our work demonstrates the effectiveness of small telescopes in conducting high-fidelity PRM campaigns of prominent emission lines in bright active galactic nuclei.

Keywords: Supermassive black holes, Quasars, Surveys, Reverberation mapping, Scaling relations, Active galactic nuclei, Narrow band photometry
ALMA Spectral Survey of an Eruptive Young Star, V883 Ori (ASSAY). II. Freshly Sublimated Complex Organic Molecules in the Keplerian Disk. We present an investigation of complex organic molecules (COMs) in the spatially resolved Keplerian disk around V883 Ori, an eruptive young star, based on a spectral survey carried out with the Atacama Large Millimeter/submillimeter Array in Band 6 (220.7‑274.9 GHz). We identified about 3700 molecular emission lines and discovered 23 COMs in the disk. We estimated the column densities of the COMs detected, using the iterative LTE line-fitting method. According to our analyses, using only optically thin lines is critical to deriving the reliable column densities of COMs. Therefore, covering a large frequency range is important for the studies of COMs. The most distinct phenomenon found from the spectra of the V883 Ori disk is that nitrogen-bearing COMs other than CH3CN are missing, whereas various oxygen-bearing COMs, except for the CH2OH-bearing molecules, are detected. The missing CH2OH-bearing COMs may indicate the warm water-ice dominant environment for forming COMs. We compared our results with various objects in different evolutionary stages, from Class 0 hot corinos to a solar system comet 67P/Churyumov-Gerasimenko, to examine the effect of evolution on the COM compositions. In general, the COM abundances relative to methanol in V883 Ori are higher than in the hot corinos and hot cores, while they are comparable to the cometary values. This may indicate the planet-forming material chemically evolves in the disk midplane after being accreted from the envelope. In addition, as found in the comet 67P/Churyumov-Gerasimenko, nitrogen might also be trapped as ammonium salt within the dust grains in the V883 Ori disk.

Keywords: Star formation, Protoplanetary disks, Complex organic molecules, Astrochemistry
Transdimensional Inference for Gravitational-wave Astronomy with Bilby. It has become increasingly useful to answer questions in gravitational-wave astronomy using transdimensional models, where the number of free parameters can be varied depending on the complexity required to fit the data. Given the growing interest in transdimensional inference, we introduce a new package for the Bayesian inference Library (Bilby), called tBilby. The tBilby package allows users to set up transdimensional inference calculations using the existing Bilby architecture with off-the-shelf nested samplers and/or Markov Chain Monte Carlo algorithms. Transdimensional models are particularly helpful when seeking to test theoretically uncertain predictions described by phenomenological models. For example, bursts of gravitational waves can be modeled using a superposition of N wavelets, where N is itself a free parameter. Short pulses are modeled with small values of N, whereas longer, more complicated signals are represented with a large number of wavelets stitched together. Other transdimensional models have been used to describe instrumental noise and the population properties of gravitational-wave sources. We provide a few demonstrations of tBilby, including fitting the gravitational-wave signal GW150914 with a superposition of N sine-Gaussian wavelets. We outline our plans to further develop the tBilby code suite for a broader range of transdimensional problems.

Keywords: Nested sampling, Astronomy data analysis, Bayes factor, Gravitational wave astronomy, Markov chain Monte Carlo
A Short-lived Rejuvenation during the Decades-long Changing-look Transition in the Nucleus of Mrk 1018. Changing-look active galactic nuclei (CL-AGNs), characterized by the emergence or disappearance of broad lines accompanied by extreme continuum flux variability, have drawn much attention for their potential to reveal physical processes underlying AGN evolution. We perform seven-season spectroscopic monitoring on Mrk1018, one of the earliest identified CL-AGN. Around 2020, we detect a full-cycle changing-look transition of Mrk 1018 within one year, associated with a nucleus outburst, which likely arose from the disk instability in the transition region between the outer standard rotation-dominated disk and inner advection-dominated accretion flow. Over the past 45 years, the accretion rate of Mrk 1018 changed 1000 times and the maximum Eddington ratio reached 0.02. By investigating the relation between the broad-line properties and the Eddington ratio (Lbol/LEdd), we find strong evidence that the full-cycle-type transition is regulated by accretion. There exists a turnover point in the Balmer decrement, which is observed for the first time. The broad Balmer lines change from a single peak in Types 1.0─1.2 to double peaks in Types 1.5─1.8, and the double-peak separation decreases with increasing accretion rate. We also find that the FWHM of the broad Balmer lines obeys FWHM  , as expected for a virialized broad-line region (BLR). The velocity dispersion σline follows a similar trend in Types 1.5─1.8 but displays a sharp increase in Types 1.0─1.2, resulting in a dramatic drop in FWHM/σline. These findings suggest that a virialized BLR together with accretion-dependent turbulent motions might be responsible for the diversity of BLR phenomena across the AGN population.

Keywords: Accretion, Supermassive black holes, Reverberation mapping, Active galactic nuclei, Time domain astronomy
A Geometric Approach to Estimate Background in Astronomical Images. Estimating the true background in an astronomical image is fundamental to detecting faint sources. In a typical low-photon-count astronomical image, such as in the far- and near-ultraviolet wavelength ranges, conventional methods relying on 3σ clipping and median or mode estimation often fail to capture the true background level accurately. As a consequence, differentiating true sources from noise peaks remains a challenging task. Additionally, in such images, effectively identifying and excluding faint sources during the background estimation process remains crucial, as undetected faint sources could contaminate the background. This results in overestimating the true background and obscuring the detection of very faint sources. To tackle this problem, we introduce a geometric approach based on the method of steepest descent to identify local minima in an astronomical image. The proposed algorithm, based on the minima statistics, effectively reduces the confusion between sources and background in the image, thereby ensuring a better background estimation and enhancing the reliability of faint-source detection. Our algorithm performs well compared to conventional methods in estimating the background even in crowded field images. In low-photon-count, less crowded images, our algorithm recovers the background within 10%, while traditional methods drastically underestimate it by a few orders of magnitude. In crowded fields, the conventional methods overestimate the background by ∼200% whereas our algorithm recovers the true background within ∼14%. We provide a simple prescription to create a background map using our algorithm and discuss its application in large astronomical surveys.

Keywords: Astrostatistics techniques, Sky noise, Astrostatistics tools