Sazuna/UAT_keywords huggingface dataset:
TEMPLATES: A Robust Outlier Rejection Method for JWST/NIRSpec Integral Field Spectroscopy. We describe a custom outlier rejection algorithm for JWST/NIRSpec integral field spectroscopy. This method uses a layered sigma clipping approach that adapts clipping thresholds based upon the spatial profile of the science target. We find that this algorithm produces a robust outlier rejection while simultaneously preserving the signal of the science target. Originally developed as a response to unsatisfactory initial performance of the jwst pipeline outlier detection step, this method works either as a standalone solution, or as a supplement to the current pipeline software. Comparing leftover (i.e., not flagged) artifacts with the current pipeline's outlier detection step, we find that our method results in one fifth as many residual artifacts as the jwst pipeline. However, we find a combination of both methods removes nearly all artifacts—an approach that takes advantage of both our algorithm's robust outlier rejection and the pipeline's use of individual dithers. This combined approach is what the TEMPLATES Early Release Science team has converged upon for our NIRSpec observations. Finally, we publicly release the code and Jupyter notebooks for the custom outlier rejection algorithm.

Keywords: Astronomical techniques, Astronomy data reduction, Spectroscopy
Solar Image Quality Assessment: A Proof of Concept Using Variance of Laplacian Method and its Application to Optical Atmospheric Condition Monitoring. Here we present a proof of concept for the application of the Variance of Laplacian (VL) method in quantifying the sharpness of optical solar images. We conducted a comprehensive study using over 65,000 individual solar images acquired on more than 160 days. Each image underwent processing using a VL image processing algorithm, which assigns a "score" based on the sharpness of the solar disk's edges. We studied the scores obtained from images acquired at different conditions. Our findings demonstrate that the sharpness of the images exhibits daily trends that are closely linked to the altitude of the Sun at the observation site. We observed a significant degradation in image quality only below a certain altitude threshold. Furthermore, we compared airmass formulae from the literature with our sharpness observations and concluded that the degradation could be modeled as an Image Sharpness Function (ISF), which exhibits similarities to airmass variations. In addition to assessing image quality, our method has the potential to evaluate the optical atmospheric conditions during daytime observations. Moreover, this technique can be easily and cost-effectively applied to archival or real-time images of other celestial bodies, such as the Moon, bright planets and defocused stars. Given that ISF is unique to each location and sensitive to sky conditions, the development of an ISF is not only beneficial for routine observation preparation but also essential for long-term site monitoring.

Keywords: Atmospheric effects, The Sun, Astronomy data analysis
Characterization and Optimization of Skipper CCDs for the SOAR Integral Field Spectrograph. We present results from the characterization and optimization of Skipper charge-coupled devices (CCDs) for use in a focal plane prototype for the Southern Astrophysical Research Integral Field Spectrograph (SIFS). We tested eight Skipper CCDs and selected six for SIFS based on performance results. The Skipper CCDs are 6k × 1k, 15 μm pixels, thick, fully depleted, p-channel devices that have been thinned to ∼250 μm, backside processed, and treated with an anti-reflective coating. We demonstrate a single-sample readout noise of &lt;4.3 e‑ rms pixel‑1 in all amplifiers. We optimize the readout sequence timing to achieve a readout noise of 0.5 e‑ rms pixel‑1 after 74 non-destructive measurements, which can be accomplished in a region covering 5% of the detector area in a readout time of &lt;4 minutes. We demonstrate single-photon-counting in all 24 amplifiers (four amplifiers per detector) with a readnoise of σ  N  ∼ 0.18 e‑ rms pixel‑1 after N samp = 400 samples, and we constrain the degree of nonlinearity to be ≲1% at low signal levels (0 e‑ to 50 e‑). Clock-induced charge (CIC) remains an important issue when the Skipper CCD is configured to provide a large full-well capacity. We achieve a CIC rate of &lt;1.45 × 10‑3 e‑ pixel‑1 frame‑1 for a full-well capacity of ∼900 e‑, which increases to a CIC rate of ∼3 e‑ pixel‑1 frame‑1 for full-well capacities ∼40,000–65,000 e‑. We also perform conventional CCD characterization measurements such as charge transfer inefficiency (3.44 × 10‑7 on average), dark current (∼2 × 10‑4 e‑ pixel‑1 s‑1), photon transfer curves, cosmetic defects (&lt;0.45% "bad" pixels), and charge diffusion (point-spread function &lt; 7.5 μm) to verify that these properties are consistent with expectations from conventional p-channel CCDs used for astronomy. Furthermore, we provide the first measurements of the brighter-fatter effect and absolute quantum efficiency (≳80% between 450 and 980 nm; ≳90% between 600 and 900 nm) using Skipper CCDs.

Keywords: Astronomical detectors, CCD observation, Spectroscopy
Hydrogen Epoch of Reionization Array (HERA) Phase II Deployment and Commissioning. This paper presents the design and deployment of the Hydrogen Epoch of Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements of the Epoch of Reionization. First results from the phase I array are published as of early 2022, and deployment of the phase II system is nearing completion. We describe the design of the phase II system and discuss progress on commissioning and future upgrades. As HERA is a designated Square Kilometre Array pathfinder instrument, we also show a number of "case studies" that investigate systematics seen while commissioning the phase II system, which may be of use in the design and operation of future arrays. Common pathologies are likely to manifest in similar ways across instruments, and many of these sources of contamination can be mitigated once the source is identified.

Keywords: Early universe, Radio telescopes, Radio interferometers, Reionization, Radio interferometry
Mitigation of the Brighter-fatter Effect in the LSST Camera. Thick, fully depleted charge-coupled devices are known to exhibit nonlinear behavior at high signal levels due to the dynamic behavior of charges collecting in the potential wells of pixels, called the brighter-fatter effect (BFE). The effect results in distorted images of bright calibration stars, creating a flux-dependent point-spread function that if left unmitigated, could make up a large fraction of the error budget in Stage IV weak-lensing (WL) surveys such as the Legacy Survey of Space and Time (LSST). In this paper, we analyze image measurements of flat fields and artificial stars taken at different illumination levels with the LSST Camera (LSSTCam) at SLAC National Accelerator Laboratory in order to quantify this effect in the LSSTCam before and after a previously introduced correction technique. We observe that the BFE evolves anisotropically as a function of flux due to higher-order BFEs, which violates the fundamental assumption of this correction method. We then introduce a new method based on a physically motivated model to account for these higher-order terms in the correction, and then we test the modified correction on both data sets. We find that the new method corrects the effect in flat fields better than it corrects the effect in artificial stars, which we suggest is the result of sub-pixel physics not included in this correction model. We use these results to define a new metric for the full-well capacity of our sensors and advise image processing strategies to further limit the impact of the effect on LSST WL science pathways.

Keywords: CCD photometry, CCD observation, Comparison stars, Astronomy data analysis, Astronomical detectors, Computational methods, Astronomical instrumentation, Turnoff point, Gravitational lensing shear
Optimal Fitting and Debiasing for Detectors Read Out Up-the-Ramp. This paper derives the optimal fit to a pixel's count rate in the case of an ideal detector read out nondestructively in the presence of both read and photon noise. The approach is general for any readout scheme, provides closed-form expressions for all quantities, and has a computational cost that is linear in the number of resultants (groups of reads). I also derive the bias of the fit from estimating the covariance matrix and show how to remove it to first order. The ramp-fitting algorithm I describe provides the χ 2 value of the fit of a line to the accumulated counts, which can be interpreted as a goodness-of-fit metric. I provide and describe a pure Python implementation of these algorithms that can process a 10-resultant ramp on a 4096 × 4096 detector in ≈8 s with bias removal on a single core of a 2020 Macbook Air. This Python implementation, together with tests and a tutorial notebook, are available at https://github.com/t-brandt/fitramp. A companion paper describes a jump detection algorithm based on hypothesis testing of ramp fits and demonstrates all algorithms on data from JWST.

Keywords: Astronomical detectors, Astronomical instrumentation
Likelihood-based Jump Detection and Cosmic Ray Rejection for Detectors Read Out Up-the-ramp. This paper implements likelihood-based jump detection for detectors read out up-the-ramp, using the entire set of reads to compute likelihoods. The approach compares the χ 2 value of a fit with and without a jump for every possible jump location. I show that this approach can be substantially more sensitive than one that only uses the difference between sequential groups of reads, especially for long ramps and for jumps that occur in the middle of a group of reads. It can also be implemented for a computational cost that is linear in the number of resultants. I provide and describe a pure Python implementation that can process a 10-resultant ramp on a 4096 × 4096 detector in ≈20 s, including iterative cosmic ray detection and removal, on a single core of a 2020 Macbook Air. This Python implementation, together with tests and a tutorial notebook, are available at https://github.com/t-brandt/fitramp. I also provide tests and demonstrations of the full ramp fitting and cosmic ray rejection approach on data from the JWST.

Keywords: Astronomical detectors, Astronomical instrumentation
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: Exoplanet atmospheric composition , Transit instruments, Spectrometers, Infrared telescopes, Astronomical simulations
From Active Stars to Black Holes: A Discovery Tool for Galactic X-Ray Sources. Galactic X-ray sources are diverse, ranging from active M dwarfs to compact object binaries, and everything in between. The X-ray landscape of today is rich, with point source catalogs such as those from XMM-Newton, Chandra, and Swift, each with ≳105 sources and growing. Furthermore, X-ray astronomy is on the verge of being transformed through data releases from the all-sky SRG/eROSITA survey. Many X-ray sources can be associated with an optical counterpart, which in the era of Gaia, can be determined to be Galactic or extragalactic through parallax and proper motion information. Here, I present a simple diagram—the "X-ray Main Sequence," which distinguishes between compact objects and active stars based on their optical color and X-ray-to-optical flux ratio (F X/F opt). As a proof of concept, I present optical spectroscopy of six exotic accreting WDs discovered using the X-ray Main Sequence as applied to the XMM-Newton catalog. Looking ahead to surveys of the near future, I additionally present SDSS-V optical spectroscopy of new systems discovered using the X-ray Main Sequence as applied to the SRG/eROSITA eFEDS catalog.

Keywords: X-ray astronomy, Binary stars, Variable stars, RS Canum Venaticorum variable stars, Cataclysmic variable stars, Astronomy data visualization, X-ray stars
Atmospheric Parameters and Abundances of Cool Red Giant Stars. Understanding the atmospheric parameters of stars on the top of the RGB is essential to reveal the chemical composition of the Milky Way, as they can be used to probe the farthest parts of our Galaxy. Our goal is to determine the chemical composition of 21 RGB stars with T eff &lt; 4200 K selected from the APOGEE-2 DR17 database using new observations carried out with the spectrograph mounted on the 1 m telescope of the Hungarian Piszkéstető Observatory and the SONG spectrograph (R = 77,000) on the Hertzsprung SONG telescope in the 4500–5800 Å wavelength range. This is the first time the spectrograph (R = 18,000) on the 1 m telescope at Piszkéstető Observatory was used to measure the abundances of stars. We created a new LTE spectral library using MARCS model atmospheres and SYNSPEC by including the line list of 23 molecules to determine atmospheric parameters (T eff,   $\mathrm{log}g$  , [Fe/H], [α/Fe]) and abundances of Si, Ca, Ti, V, Cr, Mn, and Ni with FERRE. The resulting parameters were compared to that of APOGEE. We found a good agreement in general, the average difference is ‑11.2 K in T eff, 0.11 dex in   $\mathrm{log}g$  , 0.10 dex in [Fe/H], and ‑0.01 dex in [α/Fe]. Our analysis successfully demonstrates the ability of the spectrograph at Piszkéstető Observatory to reliably measure the abundance of bright stars.

Keywords: High resolution spectroscopy, Chemical abundances, Ground-based astronomy, Red giant stars
A Serendipitous Observation of the Recently Discovered Cataclysmic Variable TUVO-21acq. The recently discovered non-magnetic cataclysmic variable TUVO-21acq was serendipitously observed in a quiescent state during an XMM-Newton observing campaign for the starburst galaxy NGC 4945. Data from this campaign was combined with archival serendipitous XMM observations to examine its X-ray and UV/optical characteristics. TUVO-21acq was found to have X-ray flux F X(0.4─3.0 keV) ∼ 1.3 × 10−14 erg s−1 cm−2 and features similar to other quiescent dwarf novae, with X-ray luminosity L X(0.4─3.0 keV) ∼ 8 × 1030 erg s−1 and a white dwarf mass ${M}_{\mathrm{WD}}={0.78}_{-0.27}^{+0.37}\,{M}_{\odot }$ . Its UV/optical spectrum was variable between observations, possibly due to changes in the accretion disk or the visibility of the bright spot.

Keywords: Cataclysmic variable stars, Dwarf novae
MINDS: The JWST MIRI Mid-INfrared Disk Survey. The study of protoplanetary disks has become increasingly important with the Kepler satellite finding that exoplanets are ubiquitous around stars in our galaxy and the discovery of enormous diversity in planetary system architectures and planet properties. High-resolution near-IR and ALMA images show strong evidence for ongoing planet formation in young disks. The JWST MIRI mid-INfrared Disk Survey (MINDS) aims to (1) investigate the chemical inventory in the terrestrial planet-forming zone across stellar spectral type, (2) follow the gas evolution into the disk dispersal stage, and (3) study the structure of protoplanetary and debris disks in the thermal mid-IR. The MINDS survey will thus build a bridge between the chemical inventory of disks and the properties of exoplanets. The survey comprises 52 targets (Herbig Ae stars, T Tauri stars, very low-mass stars and young debris disks). We primarily obtain MIRI/MRS spectra with high signal-to-noise ratio (∼100–500) covering the complete wavelength range from 4.9 to 27.9 μm. For a handful of selected targets we also obtain NIRSpec IFU high resolution spectroscopy (2.87–5.27 μm). We will search for signposts of planet formation in thermal emission of micron-sized dust—information complementary to near-IR scattered light emission from small dust grains and emission from large dust in the submillimeter wavelength domain. We will also study the spatial structure of disks in three key systems that have shown signposts for planet formation, TW Hya and HD 169142 using the MIRI coronagraph at 15.5 μm and 10.65 μm respectively and PDS 70 using NIRCam imaging in the 1.87 μm narrow and the 4.8 μm medium band filter. We provide here an overview of the MINDS survey and showcase the power of the new JWST mid-IR molecular spectroscopy with the TW Hya disk spectrum where we report the detection of the molecular ion ${{\mathrm{CH}}_{3}}^{+}$ and the robust confirmation of HCO+ earlier detected with Spitzer.

Keywords: Herbig Ae/Be stars, T Tauri stars, Pre-main sequence stars, Low mass stars, Protoplanetary disks
Direct Detection and Characterization of Exoplanets Using Imaging Fourier Transform Spectroscopy. Space-based direct imaging provides prospects for detection and spectral characterization of exoplanets at optical and near-infrared wavelengths. Integral field spectrographs (IFS) have been historically baselined for these mission concepts. However, multiple studies have revealed that detector noise is a serious obstacle for such instruments when observing extremely faint targets such as Earth-like planets. Imaging Fourier transform spectrographs (iFTS) are generally less sensitive to detector noise, and have several other compelling features such as simultaneous imaging and spectroscopy, smaller-format detector requirements, and variable spectral resolving power. To date, they have not been studied as options for such missions. Here, we compare the capabilities of IFS and iFTS for directly obtaining spectra from an Earth-like planet using both analytic and numerical models. Specifically, we compare the required exposure times to achieve the same signal-to-noise ratio with the two architectures over a range of detector and optical system parameters. We find that for a 6 m telescope, an IFS outperforms an iFTS at optical wavelengths due to the effects of distributed photon noise. In the near-IR, the relative efficiency of an IFS and iFTS depends critically on the instrument design and detector noise. An iFTS will be more efficient than an IFS if the readout noise of the near-IR detector is above ∼2–3 e‑ pix‑1 frame‑1 (t frm = 1000 s), which correspond to half to one-third of the state-of-art detector noise. However, if the readout noise is reduced below this threshold, the performance of an IFS will experience a substantial improvement and become more efficient. These results motivate consideration of an iFTS as an alternative option for future direct imaging space missions in the near-IR.

Keywords: Space telescopes, Direct imaging, Spectroscopy
KMT-2023-BLG-1431Lb: A New q &lt; 10<SUP>‑4</SUP> Microlensing Planet from a Subtle Signature. The current studies of microlensing planets are limited by small number statistics. Follow-up observations of high-magnification microlensing events can efficiently form a statistical planetary sample. Since 2020, the Korea Microlensing Telescope Network (KMTNet) and the Las Cumbres Observatory (LCO) global network have been conducting a follow-up program for high-magnification KMTNet events. Here, we report the detection and analysis of a microlensing planetary event, KMT-2023-BLG-1431, for which the subtle (0.05 mag) and short-lived (5 hr) planetary signature was characterized by the follow-up from KMTNet and LCO. A binary-lens single-source (2L1S) analysis reveals a planet/host mass ratio of q = (0.72 ± 0.07) × 10‑4, and the single-lens binary-source (1L2S) model is excluded by Δχ 2 = 80. A Bayesian analysis using a Galactic model yields estimates of the host star mass of , the planetary mass of , and the lens distance of kpc. The projected planet-host separation of au or au, subject to the close/wide degeneracy. We also find that without the follow-up data, the survey-only data cannot break the degeneracy of central/resonant caustics and the degeneracy of 2L1S/1L2S models, showing the importance of follow-up observations for current microlensing surveys.

Keywords: Gravitational microlensing, Gravitational microlensing exoplanet detection
Star Image Centering with Deep Learning. II. HST/WFPC2 Full Field of View. We present an expanded and improved deep-learning (DL) methodology for determining centers of star images on Hubble Space Telescope/Wide-Field Planetary Camera 2 (WFPC2) exposures. Previously, we demonstrated that our DL model can eliminate the pixel-phase bias otherwise present in these undersampled images; however that analysis was limited to the central portion of each detector. In the current work we introduce the inclusion of global positions to account for the point-spread function (PSF) variation across the entire chip and instrumental magnitudes to account for nonlinear effects such as charge transfer efficiency. The DL model is trained using a unique series of WFPC2 observations of globular cluster 47 Tuc, data sets comprising over 600 dithered exposures taken in each of two filters—F555W and F814W. It is found that the PSF variations across each chip correspond to corrections of the order of ∼100 mpix, while magnitude effects are at a level of ∼10 mpix. Importantly, pixel-phase bias is eliminated with the DL model; whereas, with a classic centering algorithm, the amplitude of this bias can be up to ∼40 mpix. Our improved DL model yields star-image centers with uncertainties of 8–10 mpix across the full field of view of WFPC2.

Keywords: Convolutional neural networks, Space astrometry
Detecting Moving Objects in Photometric Images Using 3D Hough Transform. In response to the exponential growth of space debris, an increasing number of observation devices are being used for the observation of moving objects, such as space debris and asteroids, which require further improvements in data-processing capabilities for the detection of moving objects. In this study, we propose a rapid detection algorithm designed for detecting moving objects, leveraging the power of the 3D Hough transform. By the simulated image experiments, our results show that the detection rate increases with the number of continuous images when fully extracting objects. Based on this foundation, the object detection rate is at least 87% regardless of the object number in the image sequence when detecting objects from at least six continuous images. In the observed image experiments, we used source-extractor to extract sources. The results show the method can successfully detect objects with signal-to-noise ratio higher than three from sidereal tracking images and can identify asteroids from asteroid tracking images while maintaining a detection speed that meets the requirements for real-time processing.

Keywords: Space debris, Astronomical object identification, Astronomy data analysis