The rapid expansion of low Earth orbit satellites such as Starlink is increasingly contaminating astronomical surveys. In practice, contaminated images are often identified through inspection. However, modern surveys generate terabytes of data each night, making manual screening infeasible and necessitating reliable automated methods for satellite trail removal. Unfortunately, existing general-domain line detection methods fail to generalize to astronomical images due to domain mismatch, which are mostly grayscale with sparse bright stars and have a low signal-to-noise ratio. Moreover, training new models from scratch is impractical due to the lack of large-scale annotated astronomical datasets. To address these challenges, we introduce STARLINC, the first ML-based framework for satellite trail removal without requiring tedious pixel-level annotation of astronomical images. STARLINC combines synthetic satellite trail generation for training, inter-frame differential maps from temporally adjacent exposures to highlight transient trails, and heatmaps to provide additional localization cues for pixel-level segmentation. Extensive experiments on real-world data demonstrate substantial improvements over baselines, establishing STARLINC as a scalable solution for next-generation astronomical surveys. Code is available at https://github.com/starioKim/STARLINC.

Recent observations of protostars with the James Webb Space Telescope have revealed unprecedented chemical complexity from their ice absorption features. However, these spectra are likely influenced by radiative transfer effects, and there is little understanding of how this impacts our ability to identify, quantify, and interpret the observed ice features. We have developed a new modeling framework to investigate the radiative transfer through icy protostellar envelopes, and we apply this to the IRAS 15398-3359 protostar observed by the JWST CORINOS program. The modeled H2O and CO column densities are similar to previous empirical studies, but we require a high CO2/H2O ratio of 76% to match the optical depth of the 15 mu m band. We use our modeled continuum to calculate a 6-10 mu m optical depth spectrum, and see considerable differences compared to a simple polynomial continuum model, underscoring the challenges in quantifying trace ice species in this range. For this source, we find that the observed absorption predominantly originates along the viewing line of sight between 1000 and 2000 au, peaking at the transition from the outflow cavity to the envelope; the spectra are largely insensitive to absorption from ices in the outer envelope, which extends out to 20,000 au. Last, we show that depending on how the line of sight intersects the cavity, the apparent CO2/H2O and CO/H2O column density ratios can be underestimated compared to the underlying ice abundance ratios. Together, this provides important context for interpreting the ice constraints derived from JWST observations of protostars.

We present the 1.6-28 mu m spectra of the young protostar EC 53, obtained with the James Webb Space Telescope (JWST) Near Infrared Spectograph Integral Field Unit and MIRI Medium Resolution Spectroscopy during the quiescent and burst phases of its periodic brightness variations. To isolate ice absorption features, we modeled and removed the mid-infrared silicate dust absorption using a dedicated continuum-fitting procedure. In the optical depth spectrum, we first fit the broad H2O ice features and then decomposed the major ice components, including NH3, CO2, CH3OH, CO, and CH4, by matching laboratory profiles for both pure and H2O-mixed ices. The 4.62 mu m and 6.85 mu m bands are attributed to OCN- and NH4+ ions, respectively. Minor or tentative contributions from complex species (HCOOH, H2CO, CH3COOH, CH3CHO, CH3CH2OH, and NH2CHO) are also considered for our global ice analysis. The silicate-corrected spectra reveal no measurable change in any ice absorption band between the two phases, indicating that moderate and short-period accretion bursts in EC 53 do not significantly alter the physical or chemical state of the ices within its envelope. The derived abundances of these major species relative to H2O significantly exceed the values typically observed toward other embedded protostars. Finally, we place the ice inventory of EC 53 in the context of other protostellar systems observed with JWST, highlighting that its chemically rich, thermally quiescent ice reservoir provides a benchmark for studying ice evolution under episodic accretion.

SPHEREx is a NASA mission designed to perform an all-sky spectroscopic survey in the 0.75-5 mu m wavelength range. Its primary science objectives are to investigate: (1) inflationary cosmology; (2) the history of galaxy formation; and (3) the abundance of molecular ices-critical for prebiotic chemistry-found on the surfaces of interstellar dust grains within planet-forming regions. This paper focuses on the third theme, the SPHEREx Ices Investigation, for which SPHEREx is conducting a spectroscopic survey of nearly 10 million preselected sources throughout the Milky Way and Magellanic Clouds, to characterize their ice absorption features. By selecting targets based on infrared color, spatial isolation, and brightness, the Ices Investigation secures high-signal-to-noise-ratio spectra across a broad range of astrophysical environments that are relatively free of spectral contamination. Rather than attempting to decompose each spectrum into its individual ice components, the Ices Investigation prioritizes accurate measurements of the integrated optical depths of key molecular ice absorption features. This approach enables statistically powerful correlation studies between ice abundances and environmental parameters-including extinction, temperature, gas composition, radiation field strength, cosmic-ray flux, and star formation activity. The data pipeline developed for this purpose incorporates machine learning for continuum estimation, drawing on both SPHEREx and ancillary data sets. Ultimately, the expansive spectral archive produced by SPHEREx, combined with targeted follow-up from facilities like JWST, will transform our understanding of Galactic ice formation, evolution, abundance, and their inheritance into planetary systems and prebiotic inventories.

We present two-epoch JWST NIRSpec and MIRI observations of the young protostar EC 53 (V371 Ser), a periodically variable source with well-characterized quiescent and burst phases. The spectra in both epochs show absorption in the CO overtone (similar to 2.3 mu m) and fundamental (similar to 4.6 mu m) bands and the H2O stretching (similar to 2.7 mu m) and bending (similar to 6.0 mu m) modes. We also obtained high-resolution (R approximate to 45,000) IGRINS spectra during the burst to constrain the CO overtone line profiles. Local thermodynamic equilibrium (LTE) slab modeling yields gas temperatures of similar to 1800 K (CO overtone) and similar to 1200 K (CO fundamental), consistent with the overtone tracing hotter gas at smaller radii. The H2O stretching-mode absorption shows no compelling evidence for variability, and the current JWST CO overtone data do not provide a robust constraint on overtone variability. In contrast, the CO fundamental and H2O bending-mode features weaken by a factor of similar to 2 during the burst, which is most naturally explained by continuum changes rather than large variations in absorbing gas. To quantify continuum dilution, we introduce a "relative veiling" that treats the quiescent spectrum as an internal reference and measures the change in the continuum excess between the two epochs. This formalism yields burst-to-quiescent hot-continuum ratios of 2.9 +/- 0.2 for the CO overtone and 1.71 +/- 0.11 for the CO fundamental. Using a viscous-disk prescription, these imply representative accretion-rate ratios of similar to 3.6 and similar to 2.0, respectively. The differing ratios suggest that inner-disk regions traced at different temperatures, and thus radii, respond differently across the burst cycle, consistent with episodic mass buildup in the inner disk during quiescence followed by more efficient transport through the innermost disk onto the protostar during the burst.

Crystalline silicates form at high temperatures (>900 K) (refs. 1,2). Their presence in comets3-6 suggests that high-temperature dust processing occurred in the early Solar System and was subsequently transported outwards to comet-forming regions. However, direct evidence for this crystallization and redistribution in Sun-like protostars has remained unknown. By comparing James Webb Space Telescope mid-infrared spectra of the periodically bursting protostar EC 53 (ref. 7), we detect crystalline silicate (forsterite and enstatite) emission features that appear only during the burst. The emergence of these features indicates active crystal formation by thermal annealing in the hot inner disk during the accretion burst. We also detect a nested outflow-a collimated atomic jet enclosed by slower molecular outflows, consistent with magnetohydrodynamic wind models8. This configuration provides a mechanism for the outward transport of freshly crystallized silicates9. To our knowledge, our results provide the first direct observational evidence of in situ silicate crystallization during episodic accretion bursts in a very young star still embedded in its dense envelope. Although we do not directly detect grains transported to the outer disk, the observed trends are consistent with outward redistribution, indicating that both dust processing and transport occur during the earliest and most dynamic stages of star formation.

We present preliminary SPHEREx maps of diffuse Galactic emission tracing polycyclic aromatic hydrocarbons (PAHs) and ionized hydrogen gas, and we study their relationship across the Galactic plane. Since its launch in early 2025, the SPHEREx space telescope has been conducting an all-sky near-infrared spectral survey from 0.75 to 5.0 mu m. We produce a large-scale map of the 3.3 mu m PAH emission feature, which is bright and detectable throughout the Galactic plane, and find a strong correlation with the thermal dust radiance measured by Planck. We also trace ionized hydrogen gas by producing a map of Brackett-alpha emission at 4.05 mu m. By combining the two maps, we identify extended shells of PAH emission associated with photodissociation regions surrounding ionized gas. We construct a PAH abundance map and find a significant anticorrelation between PAH abundance and ionized hydrogen, indicating systematic PAH depletion within ionized gas regions across the Galactic plane and demonstrating that ionizing radiation is a dominant driver of PAH abundance variations. These early SPHEREx results provide a large-scale view of PAHs and ionized hydrogen and a preview of the capability of the mission to map diffuse emission in the interstellar medium.

We report the discovery of a nearby FU Ori-type outburst (FUor), PR Ori B, in the L1641 cluster of the Orion star-forming region. The high-amplitude variability was first identified in the NEOWISE (3-5 μm) photometry of the unresolved PR Ori binary system. Long-term, resolved optical photometric monitoring demonstrates that PR Ori B is the driver of a ΔG=5mag outburst, while PR Ori A has remained constant over the last 20 years. The near-IR spectrum of PR Ori B changes from a late K-type spectral type during quiescence to a viscously heated disk during outburst, including deep absorption in ^12CO and H_2O bands. The optical spectrum also exhibits features that are commonly associated with FUors, including P Cygni profiles in Na I D lines and absorption in the Ca II infrared triplet. The luminosity of the outburst (L_acc∼30–40 L_⊙) is similar to that commonly observed in FUors. The comparison of Spitzer/IRS and VLT/VISIR spectroscopy shows some evidence of silicate crystallisation during the outburst. PR Ori B is one of the closest and brightest FUors discovered over the last few years, only one magnitude fainter than the archetype of the class FU Ori. The proximity and brightness will allow for future high angular resolution observations to probe the physics of the inner disk and to evaluate changes in the disk due to the increased luminosity.

From 2025 August 1 to August 15 UT, the SPHEREx spacecraft observed interstellar object 3I/ATLAS. Using R = 40-130 spectrophotometry at lambda = 0.7-5 mu m, lightcurves, spectra, and imaging of 3I were obtained. From these, robust detections of water gas emission at 2.7-2.8 mu m and CO2 gas at 4.23-4.27 mu m plus tentative detections of (CO2)-C-13 and CO gas were found. A slightly extended H2O coma was detected, and a huge CO2 atmosphere extending out to at least 4.2 & times; 10(5) km was discovered. Gas production rates and 1 sigma errors for H2O, (CO2)-C-12, (CO2)-C-13, and CO were Q(gas) = 3.2 & times; 10(26) +/- 20%, 1.6 & times; 10(27) +/- 10%, 1.3 & times; 10(25) +/- 25%, and 1.0 & times; 10(26) +/- 25%, respectively. Coaddition of all lambda = 1.0-1.5 mu m scattered light continuum images from 3I produced an image with high signal-to-noise ratio consistent with an unresolved source. The lightcurve of scattered light showed less than or similar to 15% variability over the observation period. The absolute brightness of 3I at 1.0-1.5 mu m is consistent with a nucleus of <2.5 km radius surrounded by a 100 times brighter coma. The 1.5-4.0 mu m continuum structure shows a strong spectral feature commensurate with water ice absorption seen in Kuiper Belt objects and distant comets. The observed cometary behavior of 3I, including its preponderance of CO2 emission, lack of CO output, small size, and predominance of large icy chunks of material in a flux-dominant coma, is similar to the behavior of short-period comet 103P/Hartley 2, the "hyperactive, strongly thermally processed comet" flyby target of the NASA Deep Impact Extended mission in 2010. This correspondence suggests that interstellar objects can be significantly thermally processed before ejection into the interstellar medium, and by comparison to 1I and 2I, this processing can be widely variable in its physical outcome.

Methanol (CH3OH) is a key complex organic molecule (COM) in the interstellar medium, widely used as a tracer of dense gas and hot molecular cores (HMCs). Using high-resolution Atacama Large Millimeter/submillimeter Array observations from the ATOMS survey, we investigate the excitation and abundance of methanol nuclear spin isomers and their relationship to chemical complexity in massive star-forming cores. We identify 20 methanol transitions, including A- and E-type lines in the v = 0 state and E-type lines in the vt = 1 state, and detect 94 HMC candidates. Rotational temperature analysis under the LTE assumption yields average values of 194 +/- 33 K for CH3OH-E vt = 1, 178 +/- 33 K for CH3OH-A v = 0, and 75 +/- 21 K for CH3OH-E v = 0. Emission from COMs other than methanol is detected in 87 of the 94 cores, with the CH3OH-E vt = 1 line intensity showing a strong correlation with the channel detection ratio (CDR). These results demonstrate that CH3OH-E vt = 1 lines are reliable tracers of HMCs and chemical complexity, and that the CDR provides a robust indicator of molecular richness. The temperature difference between A- and E-type methanol transitions is driven by anomalously strong J(2,J-2)-J(-1,J-1) lines, highlighting the importance of analyzing methanol symmetry types separately.

We present Very Large Array (VLA) C-band (5 cm) continuum, K-band (1.3 cm) continuum, and water maser (22.235 GHz) monitoring of the protostar HOPS 373. We additionally present the contemporaneous monitoring for 95 sources within the 5 cm field of view for over 2 yr during the peak of the HOPS 373 outburst and an additional epoch in 2026. HOPS 373 is a binary Class 0 protostar located in the Orion star-forming region, which has been found to have an similar to 4 & times; luminosity burst from the James Clerk Maxwell Telescope Transient Survey and NEOWISE monitoring. We do not find evidence for a change in the free-free emission traced by VLA 5 cm continuum during the peak of its outburst or during the decline. Moreover, the 1.3 cm continuum does not show significant variability between the northeast and southwest components of the HOPS 373 binary. The water maser emission is highly variable toward HOPS 373; multiple velocity components are detected at different (or the same) times, and the maser spots are located close to the 1.3 cm continuum source of HOPS 373SW. There is tentative evidence for the water maser spots to be propagating away from the source, but there is not a robust connection between the outburst and the observed maser activity. The lack of correlation between the outburst and free-free emission from HOPS 373 indicates that the free-free emission may not directly respond to increases in the accretion rate and subsequently the outflow rate. The lack of a link could be due to the outflow mostly being neutral, or there may be offsets in the timescale for the free-free response.

This document contains the supplementary materials (Appendix B, C, and D) of the paper 'Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS). V. Tracing cavity walls and shocked knots with non-thermally desorbed CH3OH in BHR71-IRS1'.

Photometric variability in young stellar objects (YSOs) provides critical insight into the mechanisms of mass accretion, disk evolution, and circumstellar extinction in early stellar evolution. We present an analysis of day-timescale optical variability in the Orion A central region using two-night 7-Dimensional Telescope (7DT) medium-band photometry obtained on 2024 March 23 and 24. The 7DT observations provide optical spectral sampling with 16 medium-band filters spanning 400-825 nm, enabling direct two-epoch comparisons. To remove satellite-trail contamination, we used an SSIM-based ResNet classifier (accuracy = 0.97, F1-score = 0.93) to exclude affected exposures. Subsequent photometry and two-epoch variability measurements yielded a working sample of 769 YSO candidates, among which we identified 110 variables (similar to 14%), including seven extreme cases with divided by Delta m(lambda)divided by > 0.5 mag. To describe the wavelength dependence of the variability, we compared five simple templates: extinction-like changes (R-V = 3.1 and 5.5), a gray (wavelength-independent) change, and two spot-like toy models (hot and cold) implemented as two-temperature surface mixtures. The best-fit results are dominated by spot-like templates (37 cold-spot and 22 hot-spot objects), with 37 sources best matched by extinction-like templates and 14 by the gray template. The m650 filter excess fraction is higher in the hot-spot and gray templates than in the others. This could be compatible with more frequent line-veiling-related contributions in those groups, although the m650 filter excess is not a direct accretion diagnostic.

We introduce a binary classification model, the double filter model, utilizing various machine learning and deep learning methods to classify young stellar objects (YSOs) and asymptotic giant branch (AGB) stars. Since YSOs and AGB stars share similar infrared (IR) photometric characteristics due to comparable temperatures and the presence of circumstellar dust, distinguishing them is challenging and often leads to misclassification. While machine learning and deep learning techniques have helped reduce YSO–AGB misclassifications, achieving a reliable separation remains challenging. Given that YSOs and AGB stars exhibit distinct light curves resulting from different variability mechanisms, our double filter model leverages light-curve data to enhance classification accuracy. This approach uncovered YSOs and AGB stars that were misclassified in IR photometry, and was validated against Taurus YSOs and spectroscopically confirmed AGB stars. We applied the model to the Spitzer/IRAC Candidate YSO catalog for the inner Galactic midplane for catalog refinement and identified potential AGB star contaminants.

Angular momentum removal is a fundamental requirement for star and planet formation, yet the mechanisms driving this process remain debated. Magnetohydrodynamic disk winds, launched along magnetic field lines from extended disk regions, offer a promising solution, particularly in regions where magnetorotational turbulence is weak. Here we present high-resolution Atacama Large Millimeter/submillimeter Array observations of the Class 0 protostar HOPS 358, revealing a rotating, nested outflow structure traced by H2CO, SO, and CH3OH emission. The outflow preserves the disk's rotational sense and is aligned with the disk axis, providing direct observational evidence for a magnetically launched disk wind. From the measured kinematics, we derive a dimensionless magnetic lever arm of approximately 2.3 and constrain the wind-launching region to radii of 10-18 astronomical units within the planet-forming zone. These results demonstrate that magnetohydrodynamic disk winds operate during the deeply embedded phase, efficiently extracting angular momentum while shaping disk evolution and establishing initial conditions for planet formation.

Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), a NASA Explorer satellite launched on 2025 March 11, is carrying out the first all-sky near-infrared spectral survey. The satellite observes in 102 spectral bands from 0.75 to 5.0 mu m with a resolving power ranging from lambda/Delta lambda = 35-130 in 6 .'' 2 pixels. The observatory obtains a 5 sigma depth of 19.5-19.9 AB mag for 0.75 < lambda < 3.8 mu m with lambda/Delta lambda similar to 40 and 17.8-18.8 AB mag for 3.8 < lambda < 5.0 mu m with lambda/Delta lambda similar to 120 after mapping the full sky four times over two years. Scientifically, SPHEREx will produce a large galaxy redshift survey over the full sky to constrain the amplitude of inflationary non-Gaussianity. The observations will produce two deep spectral maps near the ecliptic poles that use intensity mapping to probe the evolution of galaxies over cosmic history. By mapping the depth of infrared absorption features over the Galactic plane, SPHEREx will comprehensively survey the abundance and composition of water and other biogenic ice species in the interstellar medium. The project will release initial data rapidly in the form of spectral images, and specialized data products over the life of the mission as the surveys proceed. The science team will also produce spectral catalogs of planet-bearing and low-mass stars, solar system objects, and galaxy clusters three years after launch. We describe the design of the instrument and spacecraft, which flow from the core science requirements. Finally, we present an initial evaluation of the satellite's in-flight performance and key characteristics.

As part of the ALMA Large Program “Early Planet Formation in Embedded Disks,” ^12 CO (2–1) was observed towards 19 nearby low-mass protostars. Of these objects, 15 sources are found to show molecular outflow emission. Based on their morphological and kinematical structures, the CO outflows are classified into three types: a wind-driven shell, where ambient material is swept up by a wide-angle wind from the star, a bow shock, and a slow disk wind, which is a conical or parabolic flow with onion-like velocity structure. We categorize 11 outflows as a slow disk wind, 7 as a wind-driven shell, and 1 as a bow shock. Four of these outflows were found to show signs of both slow disk wind and wind-driven shell characteristics. Five objects show misalignment between the red- and blueshifted outflows. Seven objects show significant misalignment between the outflow axis (either or both of the red- and blueshifted outflows) and the minor axis of the dust continuum emission around the protostar. For the objects showing wind-driven shell emission, we compare simple parametrized models with the observations to derive physical properties of the observed shells, such as their dynamical ages. This shows evidence of a time variability in the outflows, such as changes in their direction. In some objects, large differences are seen between the properties of the red- and blueshifted outflows, possibly indicating differences in the properties of the ambient medium with which the outflow interacts.

We identify a sample of 83 spatially resolved hot molecular cores (HMCs) in the Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures (QUARKS) survey, aiming at investigating thermal feedback from massive stars. Using CH3CN (12-11) line emission together with 1.3 mm continuum data, we derive the radial temperature, volume density, and CH3CN abundance profiles for the 83 HMCs. Based on the envelope temperature and density profiles, we compute the luminosities of the embedded massive protostars with the RADMC-3D radiation transfer model. The derived luminosities are comparable (within similar to 1 dex) to the bolometric luminosities of their natal clumps and show strong correlations with several core-scale properties, including the HMC mass (Log[Menv] = 1.01 Log[L star] - 4.80), the inner core radius (the flat radius of Plummer-like volume density profile) (Log[a] = 0.46 Log[L star] + 0.52), and the central density (Log[nc] = -0.55Log[L star] + 10.47). These empirical relations provide useful observational constraints for physical models of protostellar objects. Importantly, we find a strong positive correlation between the massive protostellar luminosity and the local thermal Jeans mass. The derived Jeans masses, MJeans, exceed the HMC masses Menv, with the average MJeans being two times larger than the average Menv. This provides observational evidence that thermal feedback from massive protostars can effectively suppress further fragmentation of HMCs, thereby promoting massive star formation. In addition, the positive correlation between massive protostellar luminosity and natal clump mass suggests that more massive clumps preferentially host more luminous protostars, leading to stronger thermal feedback.

FU Ori outbursts are thought to play a key role in stellar mass assembly and in the chemistry of protoplanetary discs during the early formation of stars. However, uncertainties remain regarding the universality of these events and the physical mechanism driving the high-amplitude variability. In this work, we present an analysis of optical, near-and mid-IR photometry (ZTF, UKIDSS GPS, NEOWISE) and near-IR spectra (IRTF, Gemini) of the eruptive variable Class I YSO GPSV16. The YSO, associated with the Hii region G71.52-00.38 ( d = 3 . 61 kpc), showed two outbursts, one with Delta K-s = 2 2 mag (2005-2012) and a second starting in 2016 with Delta K-s = 5 . 6 mag and accretion luminosity of similar to 130 L-circle dot. The outbursts displayed distinct spectroscopic characteristics: the first showed emission lines associated with a hot inner disc surface, whereas the second showed absorption lines arising from the cooler upper layers of a viscously heated disc. These features likely arose due to the different accretion rates reached during each outburst. The second outburst showed a two-stage mid-IR rise, requiring approximate to 8.4yr to reach peak brightness. The mid-IR rise also started 8 yr before the onset of the optical outburst. The wavelength-dependent light curve points to an instability that is triggered at larger distances within the accretion disc and propagates inward. Assuming a propagation time of 8 yr for the accretion wave, we estimate that the second outburst started at a distance of r similar to 0.4 au. These results show how long-term, multiwavelength photometric monitoring can help identify the disc instabilities that trigger eruptions in YSOs.

We present some of the first infrared spectral maps acquired by SPHEREx. These maps, which to our knowledge are the largest of their type ever compiled in the near-infrared, reveal multiple strong lines due to interstellar ices and polycyclic aromatic hydrocarbons (PAHs) throughout the Cygnus X and North American Nebula regions. The maps emphasize the strongest features arising from the 3 mu m H2O, 4.27 mu m CO2, and 4.67 mu m CO lines and the 3.28 mu m PAH feature, all of which are detected over large areas with complex and filamentary spatial distributions. The ice absorption maps of H2O and CO2 in particular broadly trace dense, cold, and well-shielded regions across Cygnus X, consistent with the established picture of efficient ice formation in dense molecular clouds. The interstellar ice features are also detected abundantly in diffuse absorption over wide areas. The relative strengths of the H2O and CO2 features vary among different lines of sight, indicating possible differences in local physical conditions or chemical variations. The 3.28 mu m PAH emission correlates with the emission from the 7.7 and 11.2 mu m features but shows small differences that may trace the grain-size distribution and variations in the ambient UV field. SPHEREx all-sky spectral imaging-only a small fraction of which is showcased in this work-will support numerous science investigations, including the structure of the Galaxy, the physics of the interstellar medium, and the chemistry of stars.