Vol. 704
10. Planets, planetary systems, and small bodies

JWST-TST High Contrast: Medium-resolution spectroscopy reveals a carbon-rich circumplanetary disk around the young accreting exoplanet Delorme 1AB b

Delorme 1 is a binary system composed of two M5.5 stars separated by 12 au, hosting a ~13 Jupiter-mass companion, Delorme 1 AB b, in a circumbinary orbit at 84 au projected separation. The UV/NIR spectrum of Delorme 1 AB b shows numerous hydrogen-recombination lines that typically trace accretion from circumplanetary material, indicative of a gas-rich disk despite the object's relatively old (30-45 Myr) age. The object is thus doubly interesting, challenging formation scenarios of low-mass circumbinary companions at large separations, as well as conventional assumptions about disk dispersal timescales. Based on JWST/MIRI data, Mâlin et al. characterize the object in terms of its effective temperature and radius, and, using a cross-correlation technique that detects CO and H2O, infer constraints on its metallicity and C/O ratio. Furthermore, they report the direct detection of a circumplanetary disk (CPD) around Delorme 1 AB b, from excess emission longward of 10 μm. Most remarkably, the CPD spectrum shows clear signatures of gaseous H2 (tracing outflows), HCN, C2H2, and tentatively 12C13CH2, yielding the first detection of molecular line emission from a CPD. In contrast, no evidence is found for O-bearing molecules, suggesting an elevated C/O gas ratio in the disk. This breakthrough study offers a new perspective on CPD chemical composition and physical conditions, and on how accretion persists in such long-lived (nicknamed "Peter Pan") disks.

Vol. 703
5. Galactic structure, stellar clusters and populations

The large-scale kinematics of young stars in the Milky Way disc: First results from SDSS-V

Zari et al. present maps of the 3D motions of about 50 000 hot, young stars, using SDSS-V spectroscopy together with Gaia astrometry. The map reaches roughly to about 5 kpc from the Sun. The key result is the detection of strong radial motions, coherent flows of stars with amplitudes up to +/-30 km/s that alternate between inward and outward over kiloparsec scales. These flows are much stronger than those measured for older red-giant samples. Inside the solar circle the average motion is mostly inward, while outside it tends to be outward, although the pattern varies by location.

The youngest stars, with ages ~< 30 Myr, sit within stellar density enhancements that trace known star-forming regions, yet the global streaming pattern only weakly follows spiral-arm overdensities. This points to multiple drivers rather than a single tidy link to the arms. A simple picture is that both the Galactic bar and spiral structure shape these flows. The present analysis uses roughly one third of the planned SDSS-V sample, so future maps should tighten constraints on these mechanisms.

Vol. 702
3. Cosmology (including clusters of galaxies)

Stretch to stretch, dust to dust: Lower-value local H_0 measurements from the two-population modelling of type Ia supernovae

Thanks to improvements in the precision and accuracy of measurements, there now exists a discrepancy between the two values of the Hubble constant (H0): the local one, measured empirically from standard candles, and that derived from the standard model at early epochs and cosmic microwave background measurements. The authors revisit the local Hubble constant measurement from type Ia supernovae calibrated with Cepheids by modeling the differences between the two stellar populations, both intrinsic and due to dust. The calibration of supernovae includes the stretch of their light curves and possible obscuration by dust.

After careful modeling and taking the broadening and reddening of the different populations of supernovae into account, the mean extinction is found to be consistent with the Milky Way-like interstellar dust model, and is substantially higher than the value used in previous supernova calibrations. This leads to a new H0 of 70.59 +- 1.15 km/s/Mpc, or a more conservative choice of 71.45+-1.03 km/s/Mpc. This study thus reduces the Ho tension by at least 30 per cent and up to 50 per cent.

Vol. 699
1. Letters

Experimental confirmation of barrierless reactions between HeH^+ and deuterium atoms suggests a lower abundance of the first molecules at very high redshifts

As a channel to the formation of H2 in the early Universe, (HeH^+) +D -> HD^+) + H is an essential reaction in primordial chemistry. Although less important than the analogous reaction involving H, it is more easily studied in the laboratory. Cross-section measurements at the temperatures relevant to the cosmologically important chemistry of this molecule are a major contribution to early Universe chemistry. These measurements are matched to theoretical calculations, which show an excellent agreement, and reveal a reaction rate that is up to a factor of 10 greater at low temperatures (10 K) than previously assumed.

Vol. 699
6. Interstellar and circumstellar matter

The Crab Nebula at sub-arcsecond resolution with the International LOFAR Telescope

The Crab Nebula, number one in the Messier catalog of fuzzies, is the paradigmatic supernova remnant. It has everything: a central neutron star powering a pulsar wind, a highly structured thermal remnant with the nucleosynthetic signatures of the explosion, and a known birthdate. And it remains a treasure trove of phenomena for radio interferometric studies. The authors present the highest-resolution LOFAR maps to date (with resolutions better than an arcsecond), which, combined with higher-frequency maps, provide a clean separation of the thermal and synchrotron components. A remarkable feature of these new maps is the identification of an ensemble of thermal filaments for which electron densities are derived from bremsstrahlung absorption. These should form ideal targets for infrared and far-infrared high-resolution spectroscopic studies. The resulting maps and analyses are essential benchmarks for any theoretical modeling of the early evolution of plerion supernova remnants and their interaction with the circumstellar and interstellar environments.

Vol. 699
6. Interstellar and circumstellar matter

Tracing the ejecta structure of supernova 1987A: Insights and diagnostics from 3D magnetohydrodynamic simulations

This paper presents an ingenious radiation magnetohydrodynamic simulation of the development of the SN 1987A ejecta and their interaction with the complex circumstellar environment. Three-dimensional reconstructions, based on historic and contemporary multiwavelength spectroscopy and imaging, are used to verify the simulations. The authors reproduce the available element, dynamical, and polarization maps of the structure. These are then simulated for a few decades into the future. The authors then make a qualitative leap and project the supernova remnant for five millennia, as would be the case for a typically observed field supernova remnant; in this simulation we see the survival of fine structure and the persistence of signatures of the binary merger that is thought to be the origin of the progenitor. The paper is an exemplar of what can be done to connect the (few) well-observed real-time transient events with their far later observational manifestations.

Vol. 698
3. Cosmology (including clusters of galaxies)

Detection of pure warm-hot intergalactic medium emission from a 7.2 Mpc long filament in the Shapley supercluster using X-ray spectroscopy

A significant fraction of the local Universe’s baryonic content remains undetected. Cosmological simulations indicate that most of the missing baryons are located in cosmic filaments in the form of the warm-hot intergalactic medium (WHIM). This paper reports the first X-ray spectroscopic detection of pure WHIM emission from an individual, pristine filament without significant contamination from unresolved point sources or gas clumps.

Vol. 698
9. The Sun and the Heliosphere

Interstellar dust measured in situ by Ulysses: New aspects of the particle size distribution and its modulation by the heliosheath

Pre-solar grains are found in meteorites, even in situ asteroid samples, and are records of the interstellar medium at the origin of the Solar System. This study presents an analysis of a few remarkable secure recoveries of the contemporary interstellar dust in the solar neighborhood, including a few massive particles that can be separated from heliospheric residents. The ULYSSES probe, tasked with surveying the pole of the Sun, exited the ecliptic and attained altitudes of more than 2 au for a decade. The result presented here is for the gold standard detections, distinguished by their distributions in space and momentum. The authors provide a comprehensive survey of the possible effects of propagation through the heliosphere that serves as a tutorial for understanding the basis of the analysis. The derived gas-to-dust mass ratio for the very local interstellar medium is around 500, but constrained to between about 60 and 1000. They conclude with a discussion of how future missions that include directionally sensitive dust detectors will improve and extend this work.

Vol. 697
8. Stellar atmospheres

New empirical mass-loss recipe for UV radiation line-driven winds of hot stars across various metallicities

Stellar winds from massive stars play a critical role in shaping their evolution and feedback, as they remove a substantial fraction of a star’s mass over its lifetime. In this study the authors present a homogeneous sample of nearly 200 hot stars (T> 12kK) across a broad metallicity range, each with well-constrained stellar and wind parameters. This sample is used to derive a physically motivated, empirically calibrated mass-loss prescription that is applicable to all hot stars. The newly derived mass-loss recipe depends only on the classical Eddington parameter and metallicity. Contrary to theoretical predictions, no clear evidence of a steep upturn in mass loss near the Eddington limit, nor a noticeable temperature dependence, can be found. The reported mass-loss relation yields mass-loss rates substantially lower than those from commonly used theoretical recipes. A first implementation of this new prescription in stellar evolution models highlights the importance of using accurate mass-loss rates by showing their impact on stellar evolution, feedback processes, and the final fates of massive stars.

Vol. 696
7. Stellar structure and evolution

The infrared counterpart and proper motion of magnetar SGR 0501+4516

Magnetars are highly magnetic neutron stars (with magnetic fields stronger than ~10^14 G). They are discovered thanks to their bursting activity and outbursts. SGR 0501+4516 was discovered by Swift in 2008 as a new source in the hard X-ray sky. At variance with most magnetars, a near-infrared counterpart was detected.

Thanks to Hubble Space Telescope observations across 10 years, SGR 0501+4516 was observed to move in the sky with a low transverse velocity (~50 km s-1). This makes it one of the slowest magnetars, and it contradicts some claims about a connection between a strong magnetic field and a high velocity. In addition, the low velocity rules out a possible association with a nearby supernova remnant from which the neutron star might have originated. This indicates that magnetars might originate from different paths than normal supernovae.

Vol. 694
7. Stellar structure and evolution

A multi-wavelength view of the isolated neutron star eRASSU J065715.3+260428

The Galactic sample of known isolated neutron stars is extremely small, so any new member of the class is important for understanding their evolution. However, most have similar high-energy properties, whether it is their gamma-ray luminosities or thermal X-rays. This study presents a multiwavelength campaign on one such source discovered in the eROSITA survey that breaks the mold. The source, J0657, is an X-ray pulsar with a roughly 0.25 sec period, but it is significantly not detected in every other energy interval from radio to gamma rays. The authors derived a spindown rate and they draw a comparison with other rotation-powered radio pulsars, highlighting the unusual properties of the source. The X-ray emission is best fit by a two-temperature thermal spectral energy distribution, but with an absorption feature that the authors investigated as a possible proton or electron cyclotron line.

Vol. 694
9. The Sun and the Heliosphere

Flaring together: A preferred angular separation between sympathetic flares on the Sun

Sympathetic solar flares are eruptions that occur nearby in space and time, driven by an apparent interaction between the active regions in which they are triggered. Their statistical existence on the Sun has yet to be firmly established. The work provides strong statistical evidence for the existence of sympathetic flares on the Sun, and we propose an interpretation of the observed angular scale of the phenomenon, based on the separation between magnetic field line footpoints derived from potential field source surface extrapolations.

Vol. 692
10. Planets, planetary systems, and small bodies

CRIRES^+ transmission spectroscopy of WASP-127b. Detection of the resolved signatures of a supersonic equatorial jet and cool poles in a hot planet

One of the most powerful methods for exploiting the high-resolution spectroscopy transit of exoplanets is the cross-correlation technique. With this method, model spectra of different atmospheric components, usually based on physically based abundance models (e.g., chemical equilibrium), are employed as templates and cross-correlated with in-transit ratioed spectra as a function of velocity. The method has not only permitted the detection of tens of atomic and molecular species in the atmosphere of hot and ultra-hot Jupiters, it has also yielded a wealth of information on atmospheric dynamics (day-to-night winds, super-rotation, vertical winds, etc.) and spatial variability (e.g., morning-to-evening asymmetries associated with condensation or cloud effects) based on the precise velocity and strength of the correlation peak. Nortmann et al. present a study of WASP-127b, a hot Jupiter orbiting a solar-type star on a 4.2-day orbit, conducted with CRIRES+/VLT in the near-IR. A strong detection of H2O and CO is achieved, with the cross-correlation signal exhibiting a remarkable two-peaked structure. This is interpreted as the combination of a supersonic equatorial jet with ~8 km/s speeds -- with the two peaks representing the signals from the planet’s morning and evening terminators, respectively -- and muted signals at the planetary poles -- due to either significantly lower temperatures or a high cloud deck -- and explains the lack of a correlation peak at the planet's orbital velocity. This study therefore features a detection of latitudinal inhomogeneity in WASP-127b, opening the field to a 3D characterization of exoplanets, as routinely achieved for Solar System planetary atmospheres.