The Astronomical Journal - latest papers

Spatial Profiles of 3I/ATLAS CN and Ni Outgassing from Keck/KCWI Integral Field Spectroscopy

2026-11-05T00:00:00Z

Cometary activity from interstellar objects provides a unique window into the environs of other stellar systems. We report blue-sensitive integral field unit (IFU) spectroscopy of the interstellar object 3I/ATLAS from the Keck II–mounted Keck Cosmic Web Imager on 2025 August 24 UT. We confirm the previously reported CN and Ni outgassing and, for the first time, present the radial profiles of Ni and CN emission in 3I/ATLAS. We find characteristic e-folding radii of 593.7 ± 14.8 km for Ni and 841.0 ± 15.4 km for CN; this suggests that the Ni emission is more centrally concentrated in the comet’s nucleus and favors hypotheses involving easily dissociated species, such as metal carbonyls or metal–polycyclic aromatic hydrocarbon (PAH) molecules. Additional integral field spectroscopy after perihelion will provide an ongoing opportunity to determine the evolution of the radial distributions of species in the interstellar comet 3I/ATLAS.

CausticFlow: An Efficient Machine Learning Framework Combining Neural Differential Equations and Normalizing Flows for Binary Microlensing Parameter Inference

Haibin Ren, 海滨任, Wei Zhu and 伟祝 — 2026-11-05T00:00:00Z

We introduce CausticFlow, a machine learning framework that combines neural controlled differential equations with normalizing flows to infer binary microlensing parameters. This architecture naturally handles irregularly sampled time series and data gaps while flexibly capturing strongly correlated and multimodal posterior distributions. Trained on simulated KMTNet-like light curves, CausticFlow generates posterior samples in a fraction of a second, with maximum-a-posteriori estimates achieving typical precisions of ∼17% for the mass ratio q and ∼3% for the projected separation s. When used as a proposal distribution for downstream local optimization, the framework improves these precisions to <5% and <1%, respectively, and recovers model χ2 for ∼80% of simulated events. We test the generalizability of the framework on 10 real binary lensing events characterized by higher-order effects, varied cadences, and real-world noise. Despite these mismatches between simulation and reality, CausticFlow successfully recovers the model parameters, light-curve morphology, and lensing geometry for 7 of the 10 events after simple local refinement, achieving precision levels comparable to those found for simulated data in 10 CPU minutes per event. These results demonstrate that CausticFlow acts as a fast and robust proposal engine that provides informative starting points for downstream local optimization, bridging the gap between the rapid influx of data and the need for systematic modeling in large-scale microlensing surveys such as Roman, CSST, and Earth 2.0.

A Search for Exoplanets around Northern Circumpolar Stars. XI. A Planetary Companion around HD 112987 and a Planetary Companion Candidate around HD 58545

2026-11-05T00:00:00Z

We present precise radial velocity (RV) measurements of the northern circumpolar giant stars HD 58545 and HD 112987 obtained over 8 yr with the Bohyunsan Observatory Echelle Spectrograph and supplemented during the final 3 yr by the Network of Robotic Echelle Spectrographs. RV variations in giant stars may arise from orbiting companions or intrinsic phenomena, including pulsations, chromospheric activity, and rotational modulation. To distinguish these possibilities, we analyzed line-profile variations, line bisectors, chromospheric activity indicators, and photometric data, and modeled the RV time series with Keplerian orbits using Markov Chain Monte Carlo sampling. For HD 58545, the best-fitting Keplerian model yields an orbital period of 450.44 days and a minimum companion mass of 3.65 . For HD 112987, we derive an orbital period of 554.96 days and a minimum companion mass of 8.48 . None of the activity diagnostics for HD 112987 exhibits significant variability at the RV period, consistent with a Keplerian interpretation. In contrast, several activity diagnostics of HD 58545 exhibit periodicities comparable to the RV period, which is also consistent within the uncertainties with the projected rotational timescale, . Thus, rotationally modulated stellar variability may contribute to the RV signal. Although the signal can be described by a Keplerian model, the current data cannot distinguish unambiguously between a planetary companion and intrinsic stellar variability. We therefore conclude that HD 112987 hosts a planetary companion, whereas further monitoring is required to determine the origin of the RV signal in HD 58545.

The Silk Nebula: A Newly Discovered Giant [O iii] Emission Filament

2026-11-04T00:00:00Z

We report [O iii] narrowband imaging of an extremely large-scale nebula, the Silk Nebula, discovered by the Super Wide-Field [O iii] Narrow-band Survey (SWONS), together with multifiber medium-resolution spectroscopic data covering the Hα, [N ii], [S ii], and [O iii] emission lines, acquired with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) as part of the Medium-Resolution Spectroscopic Survey of Nebulae (MRS-N). Based on 2684 high-quality spectra, we measured its physical parameters, including relative line intensities, radial velocities, and full widths at half-maximum. The [S ii]/Hα ratio of the nebula significantly exceeds the shock-excitation threshold of 0.4. Its location in BPT diagnostic diagrams and spatial morphology of [O iii] both support the optical emission is dominated by shock-heated gas. The oxygen abundance is near solar and spatially uniform, consistent with a shock propagating into the ambient interstellar medium. Because [O iii] is the only emission line that clearly traces the nebular morphology, we base our distance estimate exclusively on the [O iii] kinematics, obtaining a fiducial distance of ∼160 pc. At this distance, the nebula has a physical extent of ∼28 pc along the north–south direction. We suggest that the Silk Nebula is a large [O iii] filament possibly associated with a supernova remnant, although a diffuse-ionized-gas (DIG) or ionized-bubble origin cannot be ruled out with the present data, and one of the largest angular-scale [O iii] emission structures documented to date. Future deep X-ray observations and shock-modeling efforts are required to firmly establish its nature.

Image-constrained Modeling with Hubble and Keck Images Reveals that OGLE-2012-BLG-0563Lb is a Jupiter-mass Planet Orbiting a K Dwarf

2026-11-03T00:00:00Z

We present high-angular-resolution imaging from the Hubble Space Telescope combined with adaptive optics imaging results from the Keck-II telescope to determine the mass of the OGLE-2012-BLG-0563L host star and planet to be Mhost = 0.801 ± 0.033M⊙ and Mplanet = 1.116 ± 0.087MJupiter, respectively, located at a distance of DL = 5.46 ± 0.56 kpc. There is a close–wide degeneracy in the light-curve models that indicates a star–planet projected separation of 1.50 ± 0.16 au for the close model and 8.41 ± 0.87 au for the wide model. We used the image-constrained modeling method to analyze the light-curve data with constraints from the high-angular-resolution image analysis. This revealed systematic errors in some of the ground-based light-curve photometry, which led to an estimate of the angular Einstein Radius, θE, that was too large by a factor of ∼2. The host star mass is a factor of 2.4 larger than the value presented in the A. Fukui et al. discovery paper. Although most systematic photometry errors seen in ground-based microlensing light-curve photometry will not be repeated in data from the Roman Space Telescope’s Galactic Bulge Time Domain Survey, we argue that image-constrained modeling will be a valuable method for identifying possible systematic errors in Roman photometry.

A Large-scale Technosignature Survey of the Antisolar Point with the Allen Telescope Array: Survey Design and Pilot Results

2026-11-03T00:00:00Z

In the search for technosignatures, it can be useful to narrow down the cosmic haystack by prioritizing time-coordinate “Schelling points” at which a beacon may be more likely to be transmitted. One such Schelling point is the antisolar point (ASP), the place and moment at which Earth would lie directly between a hypothetical transmitter in the Earth's transit zone (i.e., ecliptic) and the Sun. In this work, we describe a campaign to survey the ASP for radio technosignatures using the Allen Telescope Array, report the results of 3 initial nights of data from a pilot study in summer 2023, and discuss the future of the campaign. In the pilot study, we find no sky-localized narrowband 1–2.4 GHz technosignatures within an R.A. range of approximately 20.266–21.312 hr during the ASP, setting an upper limit flux density threshold of 115–936 Jy.

OGLE-2012-BLG-0563: Relative Proper Motion Constraint from Keck Follow-up Finds the Correct Lens

2026-11-03T00:00:00Z

We present Keck/NIRC2 adaptive optics imaging results of planetary microlensing event OGLE-2012-BLG-0563. We find that the OGLE-2012-BLG-0563L planetary system consists of a 1.12 ± 0.09MJup planet orbiting a 0.81 ± 0.04M⊙ host star at a distance of 5.49 ± 0.56 kpc from the Sun. This event has a lens-source separation of 23.28 ± 0.48 mas, which is the smallest lens-source separation measured to date with Keck AO data. We find that the incorrect solution—which identifies the northeast (NE) star as the source star—is favored if one only considers the discovery paper, the A. Fukui et al. (2015) solution, or an unconstrained model. However, by performing an image-constrained light-curve model fit using the relative proper-motion direction constraint from the Keck follow-up data, we demonstrate that the correct solution identifies the NE star as the lens star. The discrepancy in the unconstrained models is driven by systematics in the Faulkes Telescope South (FTS) and Microlensing Observations in Astrophysics (MOA) B and C data, alongside the impact of the relative proper-motion direction constraints. This outcome offers two important lessons for future Roman data analysis: (1) thoroughly verify systematics across all passbands and identify the precise origin of χ2 differences, and (2) utilize image-constrained light-curve modeling incorporating relative proper-motion direction constraints to identify the correct lens.

Seasonal Variations over the Zhurong Plume-disturbed Zone Indicate Modern Dust Transport in Utopia Planitia, Mars

2026-11-03T00:00:00Z

Dust activity is critical to the modern Martian climate system and drives episodic material exchange between the surface and atmosphere. Characterizing this exchange requires numerical modeling and coordinated in situ and orbital observations, which improve constraints on atmospheric processes and support robotic mission safety. We performed reflectance cross calibration between the Tianwen-1 HiRIC and Mars Reconnaissance Orbiter (MRO) HiRISE datasets to track surface changes disturbed by landing plume effects across 2 Martian yr after the Zhurong rover’s arrival. Observations show surface reflectance rapidly recovered to prelanding conditions within the first Martian year, followed by a moderate dust-cleaning event in the subsequent spring. We conclude that the site undergoes significant dust accumulation starting in late northern summer, paired with springtime dust removal driven by convective vortices. This combined pattern of dust exchange differs from records at earlier landing sites, demonstrating substantial spatial variability in modern local dust activity across Mars.

Kinematic and Dynamical Properties of Solar-neighborhood White Dwarfs from SDSS Data Release 19 and Gaia Data Release 3

Ozcan Caliskan, Selçuk Bilir and Mukremin Kilic — 2026-11-02T00:00:00Z

We present a comprehensive kinematic and dynamical analysis of 5837 white dwarfs with hydrogen-rich atmospheres, SDSS DR19 spectroscopy, and Gaia Data Release 3 astrometry. Using complementary spatial distributions, kinematic properties, and orbital parameters, we show that the sample is overwhelmingly dominated by the thin disk, with only minor contributions from the thick disk and the halo. Velocity dispersions and orbital eccentricities increase systematically from the thin disk to the halo, reflecting progressively hotter Galactic populations. Total stellar ages available for 4829 white dwarfs reveal a clear age–velocity dispersion relation with power-law indices of 0.06–0.17, confirming that white dwarfs preserve the secular dynamical heating history of the Galactic disk. We derive a thin-disk scale height of 123–229 pc and radial scale length of 3.2–3.5 kpc, while the thick disk has a scale height of 865 pc and contributes approximately 6%–7% of the local stellar density. Reconstructed birth radii indicate that changes in the guiding radii represent an important component of the present-day radial redistribution of nearby white dwarfs, although the relative contributions of radial migration and orbital blurring cannot be uniquely separated from these displacement measures. These results establish white dwarfs as powerful tracers of the kinematic, dynamical, and structural evolution of the Milky Way.

Exploring the Long-term Temporal Variability in Polarization through Multiepoch Optical Spectropolarimetry. II. A Sample of Symbiotic and Red Giant Stars

Arijit Maiti, Ruchi Pandey, Sube Singh Gurjar and Mudit K. Srivastava — 2026-10-30T00:00:00Z

Measuring polarization and its temporal variability in the continuum and across emission features provides a powerful probe of the small-scale circumstellar environments of astrophysical sources, on spatial scales otherwise inaccessible to direct imaging techniques. However, the photon-hungry nature of spectropolarimetry has significantly limited the availability of such datasets in the literature. Here we present the results of a multiepoch spectropolarimetric survey of a sample of symbiotic and red giant stars. These observations were first conducted during the performance verification phase of a recently developed medium-resolution echelle spectropolarimeter, named ProtoPol, mounted on the Physical Research Laboratory (PRL) 2.5 m telescope, Mt. Abu, India. Considering the scarcity of such observing samples in the literature, the targets were reobserved over a period exceeding 26 months, from 2024 March to 2026 May, in order to explore the time variability of their polarimetric measurements. Our sample comprises 6 symbiotic stars and 18 red giant stars. Our observations found that, unlike the Raman-scattered λλ 6830, 7088 Å features, the Hα emission in most of the symbiotics did not exhibit any notable polarization signature. However, the continuum polarization of most symbiotics and red giants in the sample showed significant variation between observation epochs. The observations presented here constitute one of the rare multiepoch spectropolarimetric datasets spanning more than 2 yr and should be of considerable interest to the broader astronomical community. This is Paper II of a two-part series of sample studies; corresponding results for Herbig Ae/Be and classical Be stars are presented in Paper I.