A key processing step in ground-based astronomy involves combining multiple noisy and blurry exposures to produce an image of the night sky with an improved signal-to-noise ratio. Typically, this is achieved via image coaddition, and can be undertaken such that the resulting night sky image has enhanced spatial resolution. Yet, this task remains a formidable challenge despite decades of advancements. In this paper, we introduce ImageMM: a new framework based on the majorization–minimization (MM) algorithm for joint multi-frame astronomical image restoration and super-resolution. ImageMM uses multiple registered astronomical exposures to produce a nonparametric latent image of the night sky, prior to the atmosphere’s impact on the observed exposures. Our framework also features a novel variational approach to compute refined point-spread functions of arbitrary resolution for the restoration and super-resolution procedure. Our algorithms, implemented in TensorFlow, leverage graphics processing unit acceleration to produce latent images in near real time, even when processing high-resolution exposures. We tested ImageMM on Hyper Suprime-Cam (HSC) exposures, which are a precursor of the upcoming imaging data from the Rubin Observatory. The results are encouraging: ImageMM produces sharp latent images, in which spatial features of bright sources are revealed in unprecedented detail (e.g., showing the structure of spiral galaxies), and where faint sources that are usually indistinguishable from the noisy sky background also become discernible, thus pushing the detection limits. Moreover, aperture photometry performed on the HSC pipeline coadd and ImageMM’s latent images yielded consistent source detection and flux measurements, thereby demonstrating ImageMM’s suitability for cutting-edge photometric studies with state-of-the-art astronomical imaging data.

We analyze high angular and velocity resolution H i line data of two LITTLE THINGS blue compact dwarfs (BCDs): Haro 29 and Haro 36. Both of these BCDs are disturbed morphologically and kinematically. Haro 29's H i data reveal a kinematic major axis that is offset from the optical major axis, and a disturbed outer H i component, indicating that Haro 29 may have had a past interaction. Position–velocity diagrams of Haro 36 indicate that it has two kinematically separate components at its center and a likely tidal tail in front of the galaxy. We find that Haro 36 most likely had an interaction in the past, is currently interacting with an unknown companion, or is a merger remnant.

This paper presents VARnet, a capable signal-processing model for rapid astronomical time series analysis. VARnet leverages wavelet decomposition, a novel method of Fourier feature extraction via the finite-embedding Fourier transform, and deep learning to detect faint signals in light curves, utilizing the strengths of modern GPUs to achieve submillisecond single-source run time. We apply VARnet to the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) single-exposure database, which holds nearly 200 billion apparitions over 10.5 yr of infrared sources on the entire sky. This paper devises a pipeline in order to extract variable candidates from the NEOWISE data, serving as a proof of concept for both the efficacy of VARnet and methods for an upcoming variability survey over the entirety of the NEOWISE data set. We implement models and simulations to synthesize unique light curves to train VARnet. In this case, the model achieves an F1 score of 0.91 over a four-class classification scheme on a validation set of real variable sources present in the infrared. With ∼2000 points per light curve on a GPU with 22 GB of VRAM, VARnet produces a per-source processing time of <53 μs. We confirm that our VARnet is sensitive and precise to both known and previously undiscovered variable sources. These methods prove promising for a complete future survey of variability with the Wide-field Infrared Survey Explorer, and effectively showcase the power of the VARnet model architecture.

Megaconstellations of thousands to tens of thousands of artificial satellites (satcons) are rapidly being developed and launched. These satcons will have negative consequences for observational astronomy research, and are poised to drastically interfere with naked-eye stargazing worldwide should mitigation efforts be unsuccessful. Here we provide predictions for the optical brightnesses and on-sky distributions of several satcons, including Starlink, OneWeb, Kuiper, and StarNet/GW, for a total of 65,000 satellites on their filed or predicted orbits. We develop a simple model of satellite reflectivity, which is calibrated using published Starlink observations. We use this model to estimate the visible magnitudes and on-sky distributions for these satellites as seen from different places on Earth, in different seasons, and different times of night. For latitudes near 50° north and south, satcon satellites make up a few percent of all visible point sources all night long near the summer solstice, as well as near sunrise and sunset on the equinoxes. Altering the satellites’ altitudes only changes the specific impacts of the problem. Without drastic reduction of the reflectivities, or significantly fewer total satellites in orbit, satcons will greatly change the night sky worldwide.

The optical impact of Starlink is of great concern and the Gen1 network is well studied. However, understanding of the planned second-generation (Gen2) constellation containing almost 30,000 satellites with two thirds in very low Earth orbit (VLEO) below 450 km is developing. This work models Gen2 orbital parameters and considers line-of-sight visibility and spacecraft illumination in relation to terrestrial latitude and investigates changes through the day/night transition period. At peak latitudes there will be over 1200 satellites illuminated above the naked-eye horizon that persist long into the local winter night. At higher latitudes in summer spacecraft may then remain illuminated during darkness hours without interruption. For optical astronomy around 90% will be below the observational horizon, still leaving up to 120 in the field of view. Of those illuminated at nightfall, traditional LEO satellites dominate and persist for longer. This is demonstrated at latitudes representing major observatories where VLEO satellites are fully eclipsed 30 minutes after astronomical dusk, but higher layers continue to restrict observations. Broader literature suggests that at nightfall the lower spacecraft may be brighter if larger, but will be out of focus and rapidly transit detectors before quickly eclipsing and so the impact may be further reduced. This work develops understanding of the Starlink Gen2 network and suggests that operators deploying satellites further below the recommend 600 km altitude limit will continue to reduce the impacts on terrestrial optical astronomy; however, that benefit must be considered against the wider environmental impacts throughout the lifecycle to make informed decisions on sustainability metrics.

The planetary and lunar ephemerides called DE440 and DE441 have been generated by fitting numerically integrated orbits to ground-based and space-based observations. Compared to the previous general-purpose ephemerides DE430, seven years of new data have been added to compute DE440 and DE441, with improved dynamical models and data calibration. The orbit of Jupiter has improved substantially by fitting to the Juno radio range and Very Long Baseline Array (VLBA) data of the Juno spacecraft. The orbit of Saturn has been improved by radio range and VLBA data of the Cassini spacecraft, with improved estimation of the spacecraft orbit. The orbit of Pluto has been improved from use of stellar occultation data reduced against the Gaia star catalog. The ephemerides DE440 and DE441 are fit to the same data set, but DE441 assumes no damping between the lunar liquid core and the solid mantle, which avoids a divergence when integrated backward in time. Therefore, DE441 is less accurate than DE440 for the current century, but covers a much longer duration of years −13,200 to +17,191, compared to DE440 covering years 1550–2650.

Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion. While several hypotheses have been put forward to explain this alignment, to date, a theoretical model that can successfully account for the observations remains elusive. In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space. We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance, thus requiring a dynamical origin. We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass ≳10 m_⊕ whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.

Spot-crossing transits offer a unique opportunity to probe spot properties such as temperature, size, and surface distribution. TOI-3884 is a rare system in which spot-crossing features are persistently observed during every transit. This is due to its unusual configuration: a nearly polar-orbit super-Neptune transits a pole-on mid-M dwarf, repeatedly crossing a polar spot. However, previous studies have reported discrepant values in key system parameters, such as stellar inclination and obliquity. To address this, we conducted multiband, multiepoch transit observations of TOI-3884 b using the MuSCAT instrument series, along with photometric monitoring with the Las Cumbres Observatory 1 m telescopes/Sinistro. We detected time-dependent variations in the spot-crossing signals, indicating that the spot is not exactly on the pole. From the monitoring data, we measured a stellar rotation period of $11.04{3}_{-0.053}^{+0.054}$ days with a modulation amplitude of ∼5% in the r band, consistent with the time variability in the spot-crossing features. Our analysis reconciles previous discrepancies and improves the constraints on the parameters of the system geometry (${i}_{\star }=139.{9}_{-2.0}^{+1.2}$ deg and $\lambda =41.{0}_{-9.0}^{+3.7}$ deg) and those of the spot properties (spot radius of $0.42{5}_{-0.011}^{+0.018}\,{R}_{\star }$ and a spot–photosphere temperature difference of $20{0}_{-9}^{+11}$ K). These results provide a critical context for interpreting upcoming transmission spectroscopy of TOI-3884 b, as well as yielding new insights into the magnetic activity and spin–orbit geometry of M dwarfs.

In this brief communication we provide the rationale for and the outcome of the International Astronomical Union (IAU) resolution vote at the XXIXth General Assembly in Honolulu, Hawaii, in 2015, on recommended nominal conversion constants for selected solar and planetary properties. The problem addressed by the resolution is a lack of established conversion constants between solar and planetary values and SI units: a missing standard has caused a proliferation of solar values (e.g., solar radius, solar irradiance, solar luminosity, solar effective temperature, and solar mass parameter) in the literature, with cited solar values typically based on best estimates at the time of paper writing. As precision of observations increases, a set of consistent values becomes increasingly important. To address this, an IAU Working Group on Nominal Units for Stellar and Planetary Astronomy formed in 2011, uniting experts from the solar, stellar, planetary, exoplanetary, and fundamental astronomy, as well as from general standards fields to converge on optimal values for nominal conversion constants. The effort resulted in the IAU 2015 Resolution B3, passed at the IAU General Assembly by a large majority. The resolution recommends the use of nominal solar and planetary values, which are by definition exact and are expressed in SI units. These nominal values should be understood as conversion factors only, not as the true solar/planetary properties or current best estimates. Authors and journal editors are urged to join in using the standard values set forth by this resolution in future work and publications to help minimize further confusion.

The Astropy Project supports and fosters the development of open-source and openly developed Python packages that provide commonly needed functionality to the astronomical community. A key element of the Astropy Project is the core package astropy, which serves as the foundation for more specialized projects and packages. In this article, we provide an overview of the organization of the Astropy project and summarize key features in the core package, as of the recent major release, version 2.0. We then describe the project infrastructure designed to facilitate and support development for a broader ecosystem of interoperable packages. We conclude with a future outlook of planned new features and directions for the broader Astropy Project.

The Nancy Grace Roman Space Telescope (Roman) will conduct a Galactic Exoplanet Survey to discover bound and free-floating exoplanets using gravitational microlensing. Roman should be sensitive to lenses with mass down to ∼0.02 M_⊕, or roughly the mass of Ganymede. Thus, the detection of moons with masses similar to the giant moons in our solar system is possible with Roman. Measuring the demographics of exomoons will provide constraints on both moon and planet formation. We conduct simulations of Roman microlensing events to determine the effects of exomoons on microlensing light curves, and whether these effects are detectable with Roman. We focus on giant planets from 30 M_⊕ to 10 M_Jup on orbits from 0.3 to 30 au, and assume that each planet is orbited by a moon with moon–planet mass ratio from 10⁻⁴ to 10⁻² and separation from 0.1 to 0.5 planet Hill radii. We find that Roman is sensitive to exomoons, although the number of expected detections is only on the order of one over the duration of the survey, unless exomoons are more common or massive than we assumed. We argue that changes in the survey strategy, in particular focusing on a few fields with higher cadence, may allow for the detection of more exomoons with Roman. Regardless, the ability to detect exomoons reinforces the need to develop robust methods for modeling triple lens microlensing events to fully utilize the capabilities of Roman.

K2-18b, a temperate sub-Neptune, has garnered significant attention due to claims of possible biosignatures in its atmosphere. Low-confidence detections of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) have sparked considerable debate, primarily around arguments that their absorption features are not uniquely identifiable. Here, we consider all five questions from the astrobiology standards of evidence framework, starting with the following: Have we detected an authentic signal? To answer this, we analyzed publicly available JWST observations of K2-18b using independent data reduction and spectral retrieval methodologies. Our comprehensive set of reductions demonstrates that the MIRI transit spectrum is highly susceptible to unresolved instrumental systematics. Applying different wavelength binning schemes yields a potpourri of planet spectra that then lead to a wide assortment of atmospheric interpretations. Consequently, we offer recommendations to help minimize this previously underappreciated instrument systematic in future MIRI reductions of any exoplanet. While the MIRI binning scheme adopted by N. Madhusudhan et al. (2025) favors the presence of DMS/DMDS in K2-18b, we find that 87.5% of retrievals using our preferred MIRI binning scheme do not. When considering the full 0.7–12 μm transit spectrum, we confirm the detection of CH₄ and favor CO₂ and find the presence of DMS and C₂H₄ to be interchangeable. Moreover, we find that the tentative presence of large features in the MIRI transit spectrum is in tension with the more robust, yet smaller, features observed in the near-IR. We conclude that red noise—rather than an astrophysical signal—plagues the mid-IR data, and there is, as yet, no statistically significant evidence for biosignatures in the atmosphere of K2-18b.

Addressing the spatial uncertainty and spectral blending challenges in China Space Station Telescope slitless spectroscopy, we present a deep learning-driven, end-to-end framework based on the You Only Look Once (YOLO) models. This approach directly detects, classifies, and analyzes spectral traces from raw 2D images, bypassing traditional, error-accumulating pipelines. YOLOv5 effectively detects both compact zero-order and extended first-order traces, even in highly crowded fields. Building on this, YOLO11 integrates source classification (star/galaxy) and discrete astrophysical parameter estimation (e.g., redshift bins), showcasing complete spectral trace analysis without other manual preprocessing. Our framework processes large images rapidly, learning spectral–spatial features holistically to minimize errors. We achieve high trace detection precision (YOLOv5) and demonstrate successful quasar identification and binned redshift estimation (YOLO11). This study establishes machine learning as a paradigm shift in slitless spectroscopy, unifying detection, classification, and preliminary parameter estimation in a scalable system. Future research will concentrate on direct, continuous prediction of astrophysical parameters from raw spectral traces.

Observational astronomy has undergone a significant transformation driven by large-scale surveys such as the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey, the Sloan Digital Sky Survey, and the Gaia Mission. These programs yield large, complex data sets that pose significant challenges for conventional analysis methods, and as a result many different machine learning techniques are being tested and deployed. We introduce a new approach to analyzing multiband photometry by using a long short-term memory autoencoder. This model provides input-dependent reweighting of the passbands on a star-by-star basis, enabling it to encode patterns present in the stars’ spectral energy distributions (SEDs) into a two-dimensional latent space. We showcase this by using Pan-STARRS grizy mean magnitudes, and we use globular clusters, labels from SIMBAD, Gaia Data Release 3 parallaxes, and PanSTARRS images to aid our analysis and understanding of the latent space. For 3,112,259 stars in an annulus around the North Galactic Cap, 99.51% have their full SED shape reconstructed—that is, the absolute difference between the observed and the model-predicted magnitude in every band—within five-hundredths of a magnitude. We show that the model likely denoises photometric data, potentially improving the quality of measurements. Lastly, we show that the detection of rare stellar types can be performed by analyzing poorly reconstructed photometry.

We present and analyze follow-up, higher resolution (R ∼ 70) H and K band integral field spectroscopy of the superjovian exoplanet HIP 99770 b with SCExAO/CHARIS. Our new data recover the companion at a high SNR in both bandpasses and more than double the astrometric baseline for its orbital motion. Jointly modeling HIP 99770 b’s position and the star’s astrometry from Hipparcos and Gaia yields orbital parameters consistent with those from the discovery paper, albeit with smaller errors, and a slight preference for a smaller semimajor axis (∼15.7–15.8 au) and a larger eccentricity (∼0.28–0.29), disfavoring a circular orbit. We revise its dynamical mass slightly downwards to 15.0${}_{-4.4}^{+4.5}$M_Jup for a flat prior and 13.1${}_{-5.2}^{+4.8}$M_Jup for a more standard log-uniform mass prior, where the inclusion of its relative radial-velocity measurement is primarily responsible for these changes. We find consistent results for HIP 99770 b’s dynamical mass, including recent VLTI/GRAVITY astrometry, albeit with a slightly smaller, better constrained eccentricity of e ∼ 0.22${}_{-0.13}^{+0.10}$. HIP 99770 b is a ∼1300 K object at the L/T transition with a gravity intermediate between that of the HR 8799 planets and older, more massive field brown dwarfs with similar temperatures but with hints of equilibrium chemistry. HIP 99770 b is particularly well suited for spectroscopic follow-up with Roman Coronagraph Instrument during the technology demonstration phase at 730 nm to further constrain its metallicity and chemistry; JWST thermal infrared observations could likewise explore the planet’s carbon chemistry, metallicity, and clouds.

The Nancy Grace Roman Space Telescope (Roman) will conduct a Galactic Exoplanet Survey to discover bound and free-floating exoplanets using gravitational microlensing. Roman should be sensitive to lenses with mass down to ∼0.02 M_⊕, or roughly the mass of Ganymede. Thus, the detection of moons with masses similar to the giant moons in our solar system is possible with Roman. Measuring the demographics of exomoons will provide constraints on both moon and planet formation. We conduct simulations of Roman microlensing events to determine the effects of exomoons on microlensing light curves, and whether these effects are detectable with Roman. We focus on giant planets from 30 M_⊕ to 10 M_Jup on orbits from 0.3 to 30 au, and assume that each planet is orbited by a moon with moon–planet mass ratio from 10⁻⁴ to 10⁻² and separation from 0.1 to 0.5 planet Hill radii. We find that Roman is sensitive to exomoons, although the number of expected detections is only on the order of one over the duration of the survey, unless exomoons are more common or massive than we assumed. We argue that changes in the survey strategy, in particular focusing on a few fields with higher cadence, may allow for the detection of more exomoons with Roman. Regardless, the ability to detect exomoons reinforces the need to develop robust methods for modeling triple lens microlensing events to fully utilize the capabilities of Roman.

K2-18b, a temperate sub-Neptune, has garnered significant attention due to claims of possible biosignatures in its atmosphere. Low-confidence detections of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) have sparked considerable debate, primarily around arguments that their absorption features are not uniquely identifiable. Here, we consider all five questions from the astrobiology standards of evidence framework, starting with the following: Have we detected an authentic signal? To answer this, we analyzed publicly available JWST observations of K2-18b using independent data reduction and spectral retrieval methodologies. Our comprehensive set of reductions demonstrates that the MIRI transit spectrum is highly susceptible to unresolved instrumental systematics. Applying different wavelength binning schemes yields a potpourri of planet spectra that then lead to a wide assortment of atmospheric interpretations. Consequently, we offer recommendations to help minimize this previously underappreciated instrument systematic in future MIRI reductions of any exoplanet. While the MIRI binning scheme adopted by N. Madhusudhan et al. (2025) favors the presence of DMS/DMDS in K2-18b, we find that 87.5% of retrievals using our preferred MIRI binning scheme do not. When considering the full 0.7–12 μm transit spectrum, we confirm the detection of CH₄ and favor CO₂ and find the presence of DMS and C₂H₄ to be interchangeable. Moreover, we find that the tentative presence of large features in the MIRI transit spectrum is in tension with the more robust, yet smaller, features observed in the near-IR. We conclude that red noise—rather than an astrophysical signal—plagues the mid-IR data, and there is, as yet, no statistically significant evidence for biosignatures in the atmosphere of K2-18b.

Addressing the spatial uncertainty and spectral blending challenges in China Space Station Telescope slitless spectroscopy, we present a deep learning-driven, end-to-end framework based on the You Only Look Once (YOLO) models. This approach directly detects, classifies, and analyzes spectral traces from raw 2D images, bypassing traditional, error-accumulating pipelines. YOLOv5 effectively detects both compact zero-order and extended first-order traces, even in highly crowded fields. Building on this, YOLO11 integrates source classification (star/galaxy) and discrete astrophysical parameter estimation (e.g., redshift bins), showcasing complete spectral trace analysis without other manual preprocessing. Our framework processes large images rapidly, learning spectral–spatial features holistically to minimize errors. We achieve high trace detection precision (YOLOv5) and demonstrate successful quasar identification and binned redshift estimation (YOLO11). This study establishes machine learning as a paradigm shift in slitless spectroscopy, unifying detection, classification, and preliminary parameter estimation in a scalable system. Future research will concentrate on direct, continuous prediction of astrophysical parameters from raw spectral traces.

Observational astronomy has undergone a significant transformation driven by large-scale surveys such as the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey, the Sloan Digital Sky Survey, and the Gaia Mission. These programs yield large, complex data sets that pose significant challenges for conventional analysis methods, and as a result many different machine learning techniques are being tested and deployed. We introduce a new approach to analyzing multiband photometry by using a long short-term memory autoencoder. This model provides input-dependent reweighting of the passbands on a star-by-star basis, enabling it to encode patterns present in the stars’ spectral energy distributions (SEDs) into a two-dimensional latent space. We showcase this by using Pan-STARRS grizy mean magnitudes, and we use globular clusters, labels from SIMBAD, Gaia Data Release 3 parallaxes, and PanSTARRS images to aid our analysis and understanding of the latent space. For 3,112,259 stars in an annulus around the North Galactic Cap, 99.51% have their full SED shape reconstructed—that is, the absolute difference between the observed and the model-predicted magnitude in every band—within five-hundredths of a magnitude. We show that the model likely denoises photometric data, potentially improving the quality of measurements. Lastly, we show that the detection of rare stellar types can be performed by analyzing poorly reconstructed photometry.

We present and analyze follow-up, higher resolution (R ∼ 70) H and K band integral field spectroscopy of the superjovian exoplanet HIP 99770 b with SCExAO/CHARIS. Our new data recover the companion at a high SNR in both bandpasses and more than double the astrometric baseline for its orbital motion. Jointly modeling HIP 99770 b’s position and the star’s astrometry from Hipparcos and Gaia yields orbital parameters consistent with those from the discovery paper, albeit with smaller errors, and a slight preference for a smaller semimajor axis (∼15.7–15.8 au) and a larger eccentricity (∼0.28–0.29), disfavoring a circular orbit. We revise its dynamical mass slightly downwards to 15.0${}_{-4.4}^{+4.5}$M_Jup for a flat prior and 13.1${}_{-5.2}^{+4.8}$M_Jup for a more standard log-uniform mass prior, where the inclusion of its relative radial-velocity measurement is primarily responsible for these changes. We find consistent results for HIP 99770 b’s dynamical mass, including recent VLTI/GRAVITY astrometry, albeit with a slightly smaller, better constrained eccentricity of e ∼ 0.22${}_{-0.13}^{+0.10}$. HIP 99770 b is a ∼1300 K object at the L/T transition with a gravity intermediate between that of the HR 8799 planets and older, more massive field brown dwarfs with similar temperatures but with hints of equilibrium chemistry. HIP 99770 b is particularly well suited for spectroscopic follow-up with Roman Coronagraph Instrument during the technology demonstration phase at 730 nm to further constrain its metallicity and chemistry; JWST thermal infrared observations could likewise explore the planet’s carbon chemistry, metallicity, and clouds.

Strottner–Drechsler–Sainty Object 1 (SDSO1) is a faint [O iii] emission nebula spanning 1$\mathop{.}\limits^{^\circ }5$, discovered southeast of M31. In previous surveys, no counterpart has been observed across radio, infrared, UV, and X-ray wavelengths, thus complicating distance determination. Utilizing the M31 H I survey with the Five-hundred-meter Aperture Spherical radio Telescope, we identified an atomic gas structure associated with SDSO1. This potential neutral gas counterpart includes three strips spatially aligned with the [O iii] emission arcs. The H I structure has a velocity between −79 and −45 km s⁻¹ with respect to the local standard of rest. It angularly extends to $2\mathop{.}\limits^{^\circ }9$, surpassing SDSO1 in size. Several structures around the H I counterpart share similar velocities, hinting at a link between the H I counterpart and the Galactic disk’s large-scale structure. The combined analysis of the three-dimensional dust map and the reddening–distance relations for these H I strips and their nearby H I structures suggests a distance of 2.0 ± 0.2 kpc. The mass of the H I counterpart is calculated to be 614M_⊙. All of these results collectively demonstrate that SDSO1 is most likely a structure in the Milky Way rather than one associated with M31.

The radius inflation is predominantly observed in short-period, low-mass stellar systems, while being rarely detected in long-period binaries. Using Transiting Exoplanet Survey Satellite photometric and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic survey data, we conducted a detailed photometric and spectroscopic analysis of six long-period (P > 7 days) detached eclipsing binaries: TIC 17303250, TIC 196817076, TIC 219488423, TIC 252991035, TIC 344753509, and TIC 72696540. Our results indicate that the first five systems are composed of low-mass stars (M ≤ 0.8M_⊙), while TIC 72696540 is likely composed of subgiant stars with M₁ = 1.267 ± 0.011M_⊙, R₁ = 2.365 ± 0.043R_⊙, and M₂ = 1.281 ± 0.011M_⊙, R₂ = 2.517 ± 0.035R_⊙. Their large radii are solely due to their evolutionary stage. Apart from TIC 72696540, none of the components of these systems displays a clear Li Iλ6708 line. Under the assumption of binary rotational synchronization, the rotational velocities of these low-mass stars are found to be less than 8 km s⁻¹, which is the upper limit related to the LAMOST-MRS resolution. Notably, however, significant radius inflation is evident in the systems TIC 17303250, TIC 344753509, and TIC 252991035. Their radii exceed the predictions of the 12 Gyr isochrones. A positive correlation between radius inflation and metallicity is evident in four of the five low-mass stars, with TIC 196817076 being the sole exception. These results suggest that metallicity may play a significant role in causing radius inflation.

The Gaia BP/RP spectra provide an excellent opportunity to search for extremely metal-poor (EMP; [M/H] ≤ –3.0) stars. In this study, we assess the potential of our Gaia BP/RP-based candidate catalog, vetting newly identified EMP candidates with higher-resolution follow-up observations. The candidates are selected based on the metallicity derived from BP/RP spectra and the goodness of fit. Fifteen candidates were observed with the Intermediate Dispersion Spectrograph (IDS) on the Isaac Newton Telescope to validate the sample. We analyzed the data with 1D local thermodynamic equilibrium models and assessed the reliability of the [C/Fe] estimates. Three well-studied metal-poor stars are included as a sanity check. For most targets, the metallicities estimated from IDS data agree well with those derived from BP/RP spectra. Five of these stars are EMP stars (four of them are newly identified), including two with [M/H] ≤ –3.5, one of which is a carbon-enhanced metal-poor star. Reliable [C/Fe] estimates are obtained for eight stars. The efficiency in detecting EMP candidates (as eight candidates with [M/H] ≤ –3.0 yielding five EMP stars) is estimated to be $6{3}_{-24}^{+19} \%$ at a 68% confidence level, which is comparable to or higher than that of the Pristine-Gaia synthetic metallicity catalogue (38%), highlighting the potential of our method.

We have developed a software pipeline, AutoWISP, for extracting high-precision photometry from citizen scientists’ observations made with consumer-grade color digital cameras (digital single-lens reflex, or DSLR, cameras), based on our previously developed tool, AstroWISP. The new pipeline is designed to convert these observations, including color images, into high-precision light curves of stars. We outline the individual steps of the pipeline and present a case study using a Sony-α 7R II DSLR camera, demonstrating subpercent photometric precision, and highlighting the benefits of three-color photometry of stars. Project PANOPTES will adopt this photometric pipeline and, we hope, be used by citizen scientists worldwide. Our aim is for AutoWISP to pave the way for potentially transformative contributions from citizen scientists with access to observing equipment.

On 2017 September 20, we observed GJ 4334, an M5V dwarf rotating with a period of 23.5 days, simultaneously with both the Space Telescope Imaging Spectrograph aboard Hubble (1160–1710 Å) and the Dual Imaging Spectrograph mounted on the 3.5 m telescope at Apache Point Observatory (3750–5050; 5800–6950 Å) as part of a larger survey of intermediately active M dwarfs. GJ 4334 flared during the observation, starting with a rise in the flux of optical chromospheric emission lines, followed by the rapid rise and decay of multiple far-ultraviolet emission lines formed in the transition region, followed by the slow decay of the optical lines. We find significant broadening and asymmetries in the optical emission lines that are potentially from bulk plasma motion, a postflare elevated flux in both the optical and far-ultraviolet, and trends in the rise and decay timescales of the Balmer series such that higher-order lines rise earlier and decay faster than lower-order lines. The equivalent durations of the flare in individual lines range from 800 to 3 × 10⁴ s, mapping to flare energies of 1 × 10²⁸–3 × 10²⁹ erg for each line. To contextualize GJ 4334’s flare behavior, we measure and compare its optical flare frequency distribution with TESS to EV Lacertae, a similar mass but faster rotating M dwarf, and find that GJ 4334 has an excess of large flares relative to the power law established by the majority of its smaller flares. This data set is a rare opportunity to characterize flares near a critical transition in stellar magnetic activity.

Multi-epoch radial velocity measurements of stars can be used to identify stellar, substellar, and planetary-mass companions. Even a small number of observation epochs can be informative about companions, though there can be multiple qualitatively different orbital solutions that fit the data. We have custom-built a Monte Carlo sampler (The Joker) that delivers reliable (and often highly multimodal) posterior samplings for companion orbital parameters given sparse radial velocity data. Here we use The Joker to perform a search for companions to 96,231 red giant stars observed in the APOGEE survey (DR14) with ≥3 spectroscopic epochs. We select stars with probable companions by making a cut on our posterior belief about the amplitude of the variation in stellar radial velocity induced by the orbit. We provide (1) a catalog of 320 companions for which the stellar companion’s properties can be confidently determined, (2) a catalog of 4898 stars that likely have companions, but would require more observations to uniquely determine the orbital properties, and (3) posterior samplings for the full orbital parameters for all stars in the parent sample. We show the characteristics of systems with confidently determined companion properties and highlight interesting systems with candidate compact object companions.

We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 ≤ z ≤ 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-z Supernova Search Team and recent results by Riess et al., this expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmological parameters: the Hubble constant (H₀), the mass density (Ω_M), the cosmological constant (i.e., the vacuum energy density, Ω_Λ), the deceleration parameter (q₀), and the dynamical age of the universe (t₀). The distances of the high-redshift SNe Ia are, on average, 10%–15% farther than expected in a low mass density (Ω_M = 0.2) universe without a cosmological constant. Different light curve fitting methods, SN Ia subsamples, and prior constraints unanimously favor eternally expanding models with positive cosmological constant (i.e., Ω_Λ > 0) and a current acceleration of the expansion (i.e., q₀ < 0). With no prior constraint on mass density other than Ω_M ≥ 0, the spectroscopically confirmed SNe Ia are statistically consistent with q₀ < 0 at the 2.8 σ and 3.9 σ confidence levels, and with Ω_Λ > 0 at the 3.0 σ and 4.0 σ confidence levels, for two different fitting methods, respectively. Fixing a "minimal" mass density, Ω_M = 0.2, results in the weakest detection, Ω_Λ > 0 at the 3.0 σ confidence level from one of the two methods. For a flat universe prior (Ω_M + Ω_Λ = 1), the spectroscopically confirmed SNe Ia require Ω_Λ > 0 at 7 σ and 9 σ formal statistical significance for the two different fitting methods. A universe closed by ordinary matter (i.e., Ω_M = 1) is formally ruled out at the 7 σ to 8 σ confidence level for the two different fitting methods. We estimate the dynamical age of the universe to be 14.2 ± 1.7 Gyr including systematic uncertainties in the current Cepheid distance scale. We estimate the likely effect of several sources of systematic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these effects appear to reconcile the data with Ω_Λ = 0 and q₀ ≥ 0.

The all sky surveys done by the Palomar Observatory Schmidt, the European Southern Observatory Schmidt, and the United Kingdom Schmidt, the InfraRed Astronomical Satellite, and the Two Micron All Sky Survey have proven to be extremely useful tools for astronomy with value that lasts for decades. The Wide-field Infrared Survey Explorer (WISE) is mapping the whole sky following its launch on 2009 December 14. WISE began surveying the sky on 2010 January 14 and completed its first full coverage of the sky on July 17. The survey will continue to cover the sky a second time until the cryogen is exhausted (anticipated in 2010 November). WISE is achieving 5σ point source sensitivities better than 0.08, 0.11, 1, and 6 mJy in unconfused regions on the ecliptic in bands centered at wavelengths of 3.4, 4.6, 12, and 22 μm. Sensitivity improves toward the ecliptic poles due to denser coverage and lower zodiacal background. The angular resolution is 61, 64, 65, and 120 at 3.4, 4.6, 12, and 22 μm, and the astrometric precision for high signal-to-noise sources is better than 015.

Between 1997 June and 2001 February the Two Micron All Sky Survey (2MASS) collected 25.4 Tbytes of raw imaging data covering 99.998% of the celestial sphere in the near-infrared J (1.25 μm), H (1.65 μm), and K_s (2.16 μm) bandpasses. Observations were conducted from two dedicated 1.3 m diameter telescopes located at Mount Hopkins, Arizona, and Cerro Tololo, Chile. The 7.8 s of integration time accumulated for each point on the sky and strict quality control yielded a 10 σ point-source detection level of better than 15.8, 15.1, and 14.3 mag at the J, H, and K_s bands, respectively, for virtually the entire sky. Bright source extractions have 1 σ photometric uncertainty of <0.03 mag and astrometric accuracy of order 100 mas. Calibration offsets between any two points in the sky are <0.02 mag. The 2MASS All-Sky Data Release includes 4.1 million compressed FITS images covering the entire sky, 471 million source extractions in a Point Source Catalog, and 1.6 million objects identified as extended in an Extended Source Catalog.

The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and nonluminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g′ ∼ 23 mag, and a spectroscopic survey of the approximately 10⁶ brightest galaxies and 10⁵ brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS and serves as an introduction to extensive technical on-line documentation.

Stellar distances constitute a foundational pillar of astrophysics. The publication of 1.47 billion stellar parallaxes from Gaia is a major contribution to this. Despite Gaia’s precision, the majority of these stars are so distant or faint that their fractional parallax uncertainties are large, thereby precluding a simple inversion of parallax to provide a distance. Here we take a probabilistic approach to estimating stellar distances that uses a prior constructed from a three-dimensional model of our Galaxy. This model includes interstellar extinction and Gaia’s variable magnitude limit. We infer two types of distance. The first, geometric, uses the parallax with a direction-dependent prior on distance. The second, photogeometric, additionally uses the color and apparent magnitude of a star, by exploiting the fact that stars of a given color have a restricted range of probable absolute magnitudes (plus extinction). Tests on simulated data and external validations show that the photogeometric estimates generally have higher accuracy and precision for stars with poor parallaxes. We provide a catalog of 1.47 billion geometric and 1.35 billion photogeometric distances together with asymmetric uncertainty measures. Our estimates are quantiles of a posterior probability distribution, so they transform invariably and can therefore also be used directly in the distance modulus ($5{\mathrm{log}}_{10}r\,-\,5$). The catalog may be downloaded or queried using ADQL at various sites (see http://www.mpia.de/~calj/gedr3_distances.html), where it can also be cross-matched with the Gaia catalog.

The light scattered from dust grains in debris disks is typically modeled as compact spheres using the Lorenz–Mie theory or as porous spheres by incorporating an effective medium theory. In this work we examine the effect of incorporating a more realistic particle morphology on estimated radiation-pressure blowout sizes. To calculate the scattering and absorption cross-sections of irregularly shaped dust grains, we use the discrete dipole approximation. These cross-sections are necessary to calculate the β-ratio, which determines whether dust grains can remain gravitationally bound to their star. We calculate blowout sizes for a range of stellar spectral types corresponding with stars known to host debris disks. As with compact spheres, more luminous stars blow out larger irregularly shaped dust grains. We also find that dust grain composition influences blowout size such that absorptive grains are more readily removed from the disk. Moreover, the difference between blowout sizes calculated assuming spherical particles versus particle morphologies more representative of real dust particles is compositionally dependent as well, with blowout size estimates diverging further for transparent grains. We find that the blowout sizes calculated have a strong dependence on the particle model used, with differences in the blowout size calculated being as large as an order of magnitude for particles of similar porosities.

We have compiled a new and complete catalog of the main properties of the 1509 pulsars for which published information currently exists. The catalog includes all spin-powered pulsars, as well as anomalous X-ray pulsars and soft gamma-ray repeaters showing coherent pulsed emission, but excludes accretion-powered systems. References are given for all data listed. We have also developed a new World Wide Web interface for accessing and displaying either tabular or plotted data with the option of selecting pulsars to be displayed via logical conditions on parameter expressions. The Web interface has an "expert" mode giving access to a wider range of parameters and allowing the use of custom databases. For users with locally installed software and database on Unix or Linux systems, the catalog may be accessed from a command-line interface. C-language functions to access specified parameters are also available. The catalog is updated from time to time to include new information.

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R ∼ 22,500), high signal-to-noise ratio (>100), infrared (1.51–1.70 μm) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design—hardware, field placement, target selection, operations—and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available.

We describe the catalogs assembled and the algorithms used to populate the revised TESS Input Catalog (TIC), based on the incorporation of the Gaia second data release. We also describe a revised ranking system for prioritizing stars for 2 minute cadence observations, and we assemble a revised Candidate Target List (CTL) using that ranking. The TIC is available on the Mikulski Archive for Space Telescopes server, and an enhanced CTL is available through the Filtergraph data visualization portal system at http://filtergraph.vanderbilt.edu/tess_ctl.