Abstract The search for an atmosphere on the closest rocky M dwarf planet, LTT 1445 A b, has been the subject of intense investigation from both the ground and space. Here, we present the first JWST transmission spectrum of LTT 1445 A b using a single visit spanning 3–5 μ m using NIRSpec/G395H. We conduct two independent reductions of the data using both the Eureka! and ExoTiC-JEDI pipelines. Overall, we measure the NRS1 transit depths to a median precision of ∼23 ppm in 42 spectroscopic channels with uniform widths of 30 pixels (∼0.02 μ m), and the NRS2 transit depths to ∼36 ppm precision in 64 spectroscopic channels, also with uniform widths of 30 pixels. We rule out any statistically significant spectral features at this precision and place limits on atmospheric metallicity using a grid of chemical equilibrium models with grey opaque clouds. Using NIRSpec/G395H alone, we can place limits on the atmospheric metallicity of ≳350 × solar when the opaque pressure level is greater than 0.01 bar. We also conduct a combined analysis of JWST/NIRSpec and Hubble Space Telescope WFC3 transmission data and find our atmospheric limits can be extended ≳500 × solar when considering both datasets. Future analyses both in transit and emission will uncover whether there are detectable atmospheric features.

New Measurements of Distances to Galaxies in the NGC 1052 Field with the Hubble and James Webb Space Telescopes: Testing the Bullet-dwarf Origin of the Trail

Abstract High-redshift Lyman continuum emitters (LCEs) are crucial for understanding how galaxies ionize the neutral hydrogen in the epoch of reionization. However, detected LCEs at z > 4 are quite rare. Here, we report an LCE candidate at z = 4.444, dubbed LCEz4-M1, which is one of the highest-redshift LCE candidates currently known. The redshift is determined from the Ly α emission line detected in the Very Large Telescope (VLT)/MUSE spectrum. The Lyman continuum (LyC) signal is detected independently in the Hubble Space Telescope F435W image and the VLT/MUSE spectrum at significances of ≃3.7 σ and ≃2.8 σ –3.0 σ , respectively. The LyC centroid is spatially consistent with the James Webb Space Telescope (JWST)/NIRCam continuum within the astrometric uncertainty. Adopting the maximum intergalactic medium transmission, we infer conservative lower-limit escape fractions of f esc ( F435W ) = 0.8 2 − 0.17 + 0.13 and f esc ( MUSE ) = 0.7 5 − 0.28 + 0.18 . Using the combined JWST and MUSE dataset, we characterize the physical properties and morphology of LCEz4-M1. In our fiducial JWST-only spectral energy distribution fit, the galaxy is compact but has a moderate current galaxy-integrated star formation surface density, Σ SFR = 0.38 M ⊙ yr −1 kpc −2 , suggesting that it is not an extreme compact starburst under this fiducial interpretation. While we find no clear evidence for an ongoing major merger for LCEz4-M1, the presence of a faint companion ( ∼ 0 . ″ 5 ) detected in the F277W band suggests a potential minor interaction. We also find that LCEz4-M1 may lie in a locally overdense region, although the environmental interpretation remains tentative. Finally, the low star formation ratio, SFR 10 Myr /SFR 100 Myr , low Ly α equivalent width, and relatively weak rest-frame optical emission lines of LCEz4-M1 may indicate a postburst LyC leaking phase.

Late-time Hubble Space Telescope Ultraviolet Spectra of SN 2023ixf and SN 2024ggi Show Ongoing Interaction with Circumstellar Material

Abstract We present a multiwavelength analysis of the nearby millisecond pulsar PSR J0437–4715, combining Hubble Space Telescope (HST) far-ultraviolet, ROSAT soft X-ray, and XMM-Newton X-ray data, to model its broadband emission and energy-resolved pulse profiles and infer key stellar parameters via Bayesian inference. The broadband emission includes cold thermal, hot thermal, and nonthermal components: cold bulk surface emission is modeled with a nonmagnetized partially ionized hydrogen atmosphere; hot-spot emission adopts the pulse profile modeling technique with a nonmagnetized fully ionized hydrogen atmosphere model; and nonthermal emission is included as a phase-invariant power-law component. By adopting an informative prior on the hot-spot geometry informed by radio polarization position angle measurements, the joint multi-instrument analysis yields a statistically viable and radio-consistent solution with a gravitational mass of 1.38 ± 0.03 M ⊙ and an equatorial circumferential radius of 13.25 − 0.35 + 0.34 km (68% confidence intervals). The hot-spot geometry consists of two spherical caps with uniform temperature distributions: the primary hot spot is situated at a colatitude of ≈130°, and the secondary hot spot lies at a colatitude of ≈9°, close to the north pole. It yields tighter radius constraints than HST+ROSAT fits and shifts the radius posterior distribution to larger values relative to NICER-only fits. This work demonstrates the importance of multiwavelength data in refining neutron star mass–radius measurements and resolving geometric degeneracies.

Abstract Galaxies evolve in tandem with their environments—mergers and gas inflows drive galaxy growth while galactic outflows launched by supernovae may seed the galactic environment with gas, metals, and energy, fueling star formation far from the main bodies of galaxies. The formation histories of young stars in the stellar halos of nearby galaxies can help understand this interplay. We thus present the most detailed map to date of young stars in the stellar halo of M82, a starburst galaxy in the M81 Group that hosts a prototypical outflow, using Hubble Space Telescope and Subaru Hyper-Suprime Cam observations. We find widespread extraplanar populations of stars with ages ≲630 Myr, with clear detections of stars up to ∼5 kpc to the south in unique arc-like stellar features (Southern Arcs) and in a new stellar trail up to ∼20 kpc to the east (M82’s tail), originating from the Southern Arcs. We estimate a total halo star formation of ∼4 × 10 6 M ⊙ in the last 630 Myr. Overall, the star formation history of the M82 tail is correlated with periods of heightened star cluster formation in the M82 disk, which suggests the influence of the starburst outflow. Further, the fraction of young stars decreases as we move away from M82 to the east. We forward a picture where the M82 tail formed from ram-pressure-stripped gas arising from M82’s westward motion, triggered by shocks from the outflow.

Abstract We present a new set of 35 transit light curves of the hot Jupiter WASP-43 b, obtained through the SPEARNET network. These datasets were analyzed together with previously published ground-based observations, as well as space-based data from TESS, Hubble Space Telescope (HST), and JWST, to refine the planetary parameters of WASP-43 b. A total of 188 midtransit times, measured with TransitFit , were analyzed for potential timing variations. The transit timing variations do not show any significant evidence of orbital decay. Atmospheric retrievals using HST/WFC3 G141 transmission spectra suggest that higher-temperature solutions are associated with higher water abundances. However, when these data are combined with observations from ground-based telescopes, TESS, and JWST, the increased modeling complexity across the broad wavelength baseline presents significant challenges for atmospheric characterization. These results highlight that high-precision, multi-instrument datasets will be necessary to break existing degeneracies in the atmospheric modeling of this target in the future.

The Hubble Space Telescope Is Still Awesome: Hubble is going strong despite its decades in space and next-generation successors.

Abstract We present a study of the multiphase gas structure and kinematics of the circumnuclear disk (CND) of NGC 5506, a nearby edge-on Seyfert galaxy, at a spatial resolution of ∼20 pc. Observations of [C i ](1–0), CO(3–2), and HCO + (4–3) obtained with the Atacama Large Millimeter/submillimeter Array reveal the CND dominated by rotational motion on scales of several hundred parsecs. No significant differences in geometrical thickness or velocity structure are found between [C i ](1–0) and CO(3–2) across the CND, whereas HCO + (4–3) emission is more concentrated toward the disk plane. The ratio of velocity dispersion to rotational velocity, a proxy for disk scale height-to-radius ratio, is high (≳0.9) in the central region (≲30 pc) for both [C i ](1–0) and CO(3–2), indicating geometrically thick structures in both tracers. Regions where the [C i ](1–0)/CO(3–2) ratio exceeds the CND average are spatially correlated with the [O iii ] λ 5007 bicone observed with the Hubble Space Telescope, suggesting that CO is preferentially dissociated by the AGN-driven biconical ionized outflow. The observed CND scale height and velocity dispersions traced by [C i ](1–0) and CO(3–2) are consistent with a model in which supernova-driven turbulence provides the vertical support for the CND.

Abstract The ultra-faint Milky Way satellite Willman 1 (W1; M V = −2.6; r half ∼ 27 pc) was the first stellar overdensity found via resolved stars in the Sloan Digital Sky Survey, yet its classification as a dwarf galaxy or star cluster remains ambiguous. Using new Keck/DEIMOS spectroscopy, Hubble Space Telescope photometry, and orbital modeling, we re-examine the nature of W1. From our updated member sample of 56 stars, we find that past analyses included four binaries and seven nonmembers, identified using Gaia proper motions and updated velocities. We continue to find a velocity dispersion consistent with previous analyses, measuring σ v = 4 . 7 − 1.3 + 1.5 km s −1 from 49 stars out to 3 r half . If W1 is in equilibrium, this suggests a dynamical mass of 5 . 9 − 3.4 + 3.7 × 1 0 5 M ⊙ and mass-to-light ratio of (M/L) V = 660 ± 590. Based on Ca II triplet measurements, we estimate an iron abundance of [Fe/H] = − 2.4 5 − 0.13 + 0.12 and metallicity dispersion of σ [ Fe / H ] = 0.3 0 − 0.11 + 0.15 dex. We confirm that W1 does not exhibit mass segregation inside ∼1 r half . Our best-fit orbital model predicts that W1 is at apocenter, implying that W1 has been closer to the Milky Way in the recent past with a pericentric passage ≲25 kpc from the Galactic center ∼0.3 Gyr ago. Given its internal kinematics, metallicity spread, and lack of mass segregation, we conclude that W1 is a galaxy. However, given its orbit and structural properties, which suggest that W1 might be tidally disrupted, as well as the difficulty in identifying a pure member sample, we caution that the measured internal velocity dispersion may not accurately reflect the dynamical mass of this system.

Abstract We present a JWST analysis of intracluster light (ICL) in XLSSC 122 at z = 1.98, currently the most distant known strong-lensing galaxy cluster with an evolved member population. Using deep JWST imaging complemented by Hubble Space Telescope data and careful control of systematics, we robustly detect diffuse emission extending to several hundred kiloparsecs from the brightest cluster galaxy (BCG) down to ∼ 29 mag arcsec − 2 . Multicomponent point-spread-function-convolved Sérsic modeling separates the surface brightness profiles into three components: a BCG core, a BCG envelope, and an ICL component, with stable Sérsic indices across wavelengths. Nearly flat color profiles indicate minimal radial variation in the stellar populations of the BCG envelope and the ICL. The median ICL fraction measured across seven bands is ∼17%, demonstrating that the buildup of intracluster stars in massive halos was already well underway by z ∼ 2. The ICL fraction peaks near 5000 Å in the rest frame, which provides the first confirmation at z > 1 that this characteristic rise is a feature of dynamically active clusters. We also detect a southern excess of ICL relative to the best-fit Sérsic model and quantify it using wavelet-based modeling, providing additional support that this system is dynamically active. The BCG + ICL light distribution and strong-lensing mass map show strong morphological agreement within ∼100 kpc. These findings establish the ICL as an early forming and dynamically informative component of massive halos.

Variability monitoring provides unparalleled insights into the atmospheric processes of brown dwarfs and directly imaged exoplanets. Inhomogeneous clouds, aurora e , and magnetic spots have all been postulated as potential drivers of variability. While objects at the L/T transition have had their variability studied extensively, the variability of early L dwarfs remain s an understudied region of the parameter space. We used observations from the Hubble Space Telescope in the near-infrared, using WFC3/G141 to disentangle the drivers of variability in three known variable early L dwarfs: 2MASS J1721039+334415, 2MASS J00361617+1821104, and 2MASS J19064801+4011089. We find that all three objects exhibit significant variability at all wavelengths, with white-light amplitudes of 0.53--1.41 $%$. We find that their colour variations are brighter and bluer compared to later spectral types, except for 2MASS J19064801+4011089, which exhibits largely grey variations. We report a new period for 2MASS J1721039+334415 of 4.9^ +0.4 _ -0.2 hours. We find evidence of long-term light curve stability in each object, which may indicate the presence of long-lived features on their surfaces. We created a flexible modelling framework to model three potential drivers of variability: clouds, aurorae, and magnetic spots. We fit our models to the spectral variability amplitude from 1.1-1.67 ̆pmum of each object. We find that changing cloud properties or magnetic spots are the most likely drivers of variability in each object. Auroral models do not reproduce the variability within the HST wavelengths; however, future observations at longer wavelengths that probe higher in the atmosphere may be more sensitive to auroral effects. This work provides a foundation for future variability studies of early L dwarfs and directly imaged exoplanets to disentangle auroral, cloud, and magnetic spot driven variability.

Abstract Blue straggler stars (BSSs) are believed to form through mass transfer in binary systems or stellar collisions. The reported presence of double BSS sequences in some globular clusters (GCs) has been interpreted as evidence that these two formation channels produce distinct sequences in color–magnitude diagrams. We reassess this claim using Hubble Space Telescope (HST) UV Globular Cluster Survey photometry of 56 Galactic GCs. We used the Hartigan dip test to test bimodality, and Akaike model comparison to test whether BSS distance distributions are better described by a mixture of two unskewed Gaussians or a skewed unimodal Gaussian model. We find no strong statistical evidence for bimodality: no cluster yields a dip test p -value below 0.15, and the Akaike model comparison favors the skewed unimodal model in 94 out of 112 cases. We reexamine NGC 7099 (M30), the prototypical case of a double BSS sequence, using three reductions of HST data. We find bimodality is detected at p = 4 × 10 −3 , versus the originally reported p ∼ 10 −5 , in the original photometry. The observed uncertainties derived from the subgiant branch widths are comparable to the suggested separation between the proposed BSS sequences, making the detection of statistically significant bimodality challenging. Our results suggest that the dip between two BSS sequences in the M30 photometry is a coincidence, and that later bifurcation claims can be explained as skew in the BSS color distribution, rather than two separate distributions.

Abstract We present a multiwavelength catalog of mid-infrared-selected compact sources in 19 nearby galaxies, combining JWST NIRCam/MIRI, Hubble Space Telescope UV–optical broadband, H α narrowband, and Atacama Large Millimeter/submillimeter Array CO observations. We detect 24,945 compact sources at 21 μ m and 55,581 at 10 μ m. Artificial star tests show 50% completeness limits of ∼5 μ Jy for the 10 μ m catalog, and ∼24 μ Jy for the 21 μ m catalog. We find that 21 μ m compact sources contribute ∼20% of the total galaxy emission in that band, but only contribute 5% at 10 μ m. We classify sources using stellar evolution and population synthesis models combined with empirical classifications derived from the literature. Our classifications include H α -bright and dust-embedded optically faint clusters, red supergiants, oxygen-rich and carbon-rich asymptotic giant branch stars, and a range of rarer stellar types. In sampling a broad range of star-forming environments with a uniform, well-characterized selection, this catalog enables analyses of infrared-bright stellar populations. We find that H α -faint sources account for only 10% of dusty (likely young) clusters, implying that the infrared-bright, optically faint phase of cluster evolution is short compared to the H α -bright stage. The luminosity functions of 10 and 21 μ m sources follow power-law distributions, with the 21 μ m slope (−1.7 ± 0.1) similar to that of giant molecular cloud mass functions and ultraviolet bright star-forming complexes, while the 10 μ m slope (−2.0 ± 0.1) is closer to that of young stellar clusters.

Abstract Observing the dayside thermal emissions of rocky exoplanets provides essential insights into their compositions and the presence of atmospheres. Even though no conclusive evidence has been found for atmospheres on small rocky exoplanets orbiting M dwarfs, recent JWST observations identified puzzling thermal emission excesses. Some rocky exoplanets orbiting M dwarfs have dayside emission temperatures higher than the theoretical maximum temperatures, which are calculated assuming stellar irradiation as the sole energy source. Therefore, the observed thermal emission excesses imply that these planets may have internal heat sources. In this work, we simulate three possible internal planetary processes that may generate excess heat in addition to stellar irradiation: residual heating from formation, tidal heating, and induction heating due to interactions with the stellar magnetic field. We found that these mechanisms, even when combined, cannot explain the observed thermal emission excesses, nor can they account for a tentative positive trend in the brightness temperature scaling factor with irradiation temperature. Our results imply that planetary internal processes are unlikely to generate remotely detectable heat, so the observed thermal excesses, if astrophysical, are likely caused by stellar contamination, surface processes, geometric effect, or other internal processes not considered in this study. The ongoing JWST–Hubble Space Telescope Rocky Worlds Director’s Discretionary Time Program and the upcoming Nancy Grace Roman Space Telescope will provide more insights into the thermal emission of rocky exoplanets.

Abstract We report on the observation and measurement of astrometry, photometry, morphology, and activity of the interstellar object 3I/ATLAS, also designated C/2025 N1 (ATLAS) with the NSF-DOE Vera C. Rubin Observatory. Comet 3I/ATLAS, the third known interstellar object, was discovered on UT 2025 July 1. Rubin Observatory had coincidentally collected images of the object’s region of the sky during routine commissioning. Facilitated by Rubin’s high resolution and large aperture, we successfully recovered object detections from Rubin observations spanning UT 2025 June 21 (10 days before discovery, when 3I/ATLAS was 4.5 au from the Sun) through the date of discovery, and we acquired additional images through UT 2025 July 20 as part of commissioning. We measure on-sky locations of 3I/ATLAS in Rubin ugrizy bands, with a typical precision of ∼70 mas, and briefly describe the reason this is coarser than our measured static source astrometric precision of ∼3 mas in Rubin images. We measure grizy magnitudes of 3I/ATLAS photometry at ∼0.01 mag precision, detecting no short-term photometric variability above 0.01 mag. We derive an estimated near-nucleus dust-to-nucleus scattering cross-sectional ratio of η ≳ 13 on UT 2025 July 2 based on Rubin photometry and an upper limit nucleus size computed from Hubble Space Telescope observations. We find Rubin colors of g − r = (0.657 ± 0.013) mag, r − i = (0.235 ± 0.018) mag, i − z = (0.147 ± 0.042) mag, and z − y = (0.047 ± 0.052) mag. These data represent the earliest observations of this object by a large (≳8 m class) telescope and illustrate the type of measurements (and discoveries) Rubin’s Legacy Survey of Space and Time will provide after it begins in early 2026.

Abstract We present a sample of large double radio sources hosted by spiral galaxies (spiral double radio active galactic nuclei, SDRAGNs). Candidates were initially selected through the Radio Galaxy Zoo project and subsequently refined using Sloan Digital Sky Survey images. The most promising were targeted in the Zoo Gems Hubble Space Telescope (HST) program, yielding images for 36 candidates. We assess the likelihood that each spiral galaxy is the genuine host of the radio emission, finding 15 new high-probability SDRAGNs. The hosts are seen preferentially close to edge-on. SDRAGNs predominantly show type II Fanaroff–Riley (FR II) radio structures and optical pseudobulges. After accounting for sample selection effects, the radio-jet axes lie preferentially near the poles of the galactic disks; we find a constant probability distribution for intrinsic pole–jet angles ϕ < 30°, declining to zero at ϕ = 60°. We have obtained optical spectra for all these newly identified SDRAGNs. Among both previously known and new SDRAGN samples, 8/25 show Seyfert 2 signatures, 6/25 show central star formation, and 5/25 show low-ionization nuclear emission-line region emission strong enough to indicate active galactic nuclei (AGN) activity or shock ionization, broadly similar to radio galaxies in elliptical hosts but with the addition of star formation (diluting or masking weak AGN signatures). SDRAGNs include FR II sources seen at unusually low radio powers, and preferentially occur in significant galaxy overdensities on 1 Mpc scales. Our “false alarms”—systems where HST data show the spiral is not the actual host galaxy—include radio sources seen through large portions of foreground spiral disks, potentially providing useful probes for Faraday rotation studies of disk magnetic fields.

Abstract We present spectroscopic data of strong lenses and their source galaxies using the Keck Near-Infrared Echellette Spectrometer (NIRES) and the Dark Energy Spectroscopic Instrument (DESI), providing redshifts necessary for nearly all strong-lensing applications with these systems, especially the extraction of physical parameters from lensing modeling. These strong lenses were found in the DESI Legacy Imaging Surveys using residual neural networks and followed up by our Hubble Space Telescope program, with all systems displaying unambiguous lensed arcs. With NIRES, we target eight lensed sources at redshifts difficult to measure in the optical range and determine the source redshifts for six, between z s = 1.675 and 3.332. DESI observed one of the remaining source redshifts, as well as an additional source redshift within the six systems. The two systems with nondetections by NIRES were observed for a considerably shorter 600 s at high airmass. Combining NIRES infrared spectroscopy with optical spectroscopy from our DESI Strong Lensing Secondary Target Program, these results provide the complete lens and source redshifts for six systems, a resource for refining automated strong lens searches in future deep- and wide-field imaging surveys and addressing a range of questions in astrophysics and cosmology.

Abstract We present astrometric measurements for 13 cold brown dwarfs in the solar neighborhood ( d < 20 pc). By combining archival Spitzer data with our own Hubble Space Telescope (HST) observations, we achieve parallax uncertainties typically around 10%. Using Spitzer and HST photometry we compare our targets with other known late T and Y dwarfs in the Solar neighborhood, confirming that there is large intrinsic scatter in the near- and mid-infrared absolute magnitudes and colors of this population, further highlighting the diversity observed spectroscopically by several James Webb Space Telescope programs. This scatter makes photometric distance estimates highly unreliable and, therefore, makes astrometric parallax measurements fundamental for a meaningful characterization of even the nearest cold brown dwarfs.

Abstract For decades, astronomers have been searching for bright radio sources deep into the epoch of reionization. The most distant, powerful radio sources are expected to reside in heavily dust-obscured galaxies, exceedingly faint at optical and infrared wavelengths. Motivated by this, I systematically cross-match radio and JWST source catalogs in the COSMOS field and identify a uniquely JWST-dark radio source: the only object undetected in every JWST band, yet clearly detected in radio data from LOFAR 144 MHz to the Very Large Array 3 GHz. The source is only marginally resolved and shows a steep, unbroken radio spectrum, while remaining undetected in all available Hubble Space Telescope, JWST, Chandra, Herschel, and Atacama Large Millimeter/submillimeter Array imaging. It may represent an extremely dust-obscured radio-loud source at cosmic dawn, or alternatively a detached radio lobe whose host galaxy lies elsewhere. In either case, it highlights the new discovery space at the intersection of deep radio surveys and JWST imaging.