Papers for Thursday, Jan 29 2026

We present observations of HCN and HCO$^+$ J = $3 - 2$ in the central $424'' \times 424''$ region of the W40 massive star forming region. The observations were taken as part of a pilot project for the MAJORS large program at the JCMT telescope. By incorporating prior knowledge of N(H$_2$) and $T_K$, assuming a constant density, and using the RADEX radiative transfer code we found that the HCN and HCO$^+$ abundances range from $X$(HCN) = $0.4-7.0 \times 10^{-8}$ and $X$(HCO$^+$) = $0.4-7.3 \times 10^{-9}$. Additional modelling using the NAUTILUS chemical evolution code, that takes H$_2$ density variations into account, however, suggests the HCN and HCO$^+$ abundances may be fairly constant. Careful modelling of three different positions finds $X$(HCN) = $1.3-1.7 \times 10^{-8}$, $X$(HCO$^+$) = $1.3-3.1 \times 10^{-9}$. Cross-comparison of the two models also provides a crude estimate of the gas density producing the HCN and HCO$^+$ emission, with H$_2$ densities in the range $5 \times 10^4 - 5 \times 10^5$ cm$^{-3}$, suggesting that the HCN and HCO$^+$ emission does indeed arise from dense gas. High UV intensity (e.g. $G_o >$ a few thousand) has no effect on the abundances in regions where the visual extinction is large enough to effectively shield the gas from the UV field. In regions where $A_V < 6$, however, the abundance of both species is lowered due to destructive reactions with species that are directly affected by the radiation field.

Inferring stellar parameters and chemical abundances by forward modeling stellar spectra usually requires a spectral synthesis code, or an emulator constructed from a curated training set. In these situations continuum normalization is often implemented as a pre-processing step that is independent of stellar parameters. This leads to results that are biased, or inconsistent across signal-to-noise ratios. A more justified approach is to forward model spectra with all nuisances simultaneously, but in practice this can be an expensive or non-convex optimization procedure. Here we describe a constrained linear model that can fit stellar absorption, telluric transmission, the joint continuum-instrument response. Stellar absorption and telluric transmission are each modeled by factorizing a grid of rectified theoretical spectra into two non-negative matrices with a chosen number of basis components. This model characterizes all possible spectra in many fewer parameters than comparable data-driven models. The non-negativity constraint ensures basis vectors are strictly additive, which limits rectified flux to less than or equal to unity, such that we can distinguish normalized spectra from the joint instrument-continuum response. The model requires no initial guess, and the linearity ensures that inference is convex, stable, and fast. This model allows us to reliably fit nuisances (e.g., tellurics, continuum), and is readily extensible to radial velocity and rotational broadening, without any prior knowledge about the fundamental stellar properties. We demonstrate our method by fitting ESO/HARPS high-resolution echelle spectra of BAFGKM-type stars. With repeat observations of $\alpha$-Centauri A we present results that are best in class: consistent across time to 0.2% at S/N ~ 100, and to better than 0.5% at S/N ~ 30.

Galaxy clusters are the most massive gravitationally bound structures in the universe and serve as tracers of the assembly of large-scale structure. Studying their progenitors, proto-clusters, sheds light on the earliest stages of cluster formation. Yet, detecting proto-clusters is demanding: their member galaxies are loosely bound and the emerging hot intracluster medium (ICM) may only be in the initial stages of virialization. Recent JWST observations located several proto-cluster candidates by identifying overdensities of $z\gtrsim5$ galaxies. However, none of these candidates was detected by X-ray observations, which offer a powerful way to unveil the hot ICM. Here, we report the combined Chandra and JWST detection of a proto-cluster, JADES-ID1, at $z\approx5.68$, merely one billion years after the Big Bang. We measure a bolometric X-ray luminosity of $L_{\rm bol} = (1.5^{+0.5}_{-0.6}) \times10^{44} \ \rm{erg \ s^{-1}}$ and infer a total gravitating mass of $M_{500}= (1.8^{+0.6}_{-0.7}) \times 10^{13} \ \rm{M_{\odot}}$, making this system a progenitor of today's most massive galaxy clusters. The detection of extended, shock-heated gas indicates that substantial ICM heating can occur in massive halos as early as $z\approx5.7$. In addition, given the limited survey volume, the discovery of such a massive cluster is statistically unlikely, implying that the formation of the large-scale structure must have occurred more rapidly in some regions of the early universe than standard cosmological models predict.

Long-period variables (LPVs) are evolved red giant and supergiant stars whose pulsations provide unique insights into late stages of stellar evolution and serve as essential tools in modern astrophysics. Their period-luminosity and period-age relations make them valuable distance and age indicators, while their light curve morphology, amplitudes, and multiperiodicity reveal the underlying physics of stellar interiors and mass-loss. In this review, we provide an overview of the current status of LPV studies, focusing on their observational properties and applications, including: - Modern classification of LPVs into Miras, semiregular variables (SRVs), and OGLE small-amplitude red giants (OSARGs), which occupy multiple period-luminosity sequences associated with different pulsation modes, chemical compositions, and evolutionary stages - Mira variables as reliable distance indicators across diverse stellar environments and their increasing role as standard candles - The increasing role of SRVs and OSARGs - Long secondary period (LSP) variables as potential tracers of exoplanets Together with advances in theoretical modeling, these developments establish LPVs as valuable tracers of Galactic structure, stellar populations, and the extragalactic distance scale.

Context: The radial drift and fragmentation of small dust grains in protoplanetary discs impedes their growth past centimetre sizes. Several mechanisms have been proposed to overcome these planet formation barriers, such as dust porosity or the streaming instability (SI), which is today regarded as the most promising mechanism to form planetesimals. Aims: Here, we examine whether the conditions for the SI to lead to strong clumping, the first step in planetesimal formation, are realised in protoplanetary discs containing porous grains. Methods: We used results from previous simulations of the evolution of porous grains subjected to growth, fragmentation, compaction and bouncing in protoplanetary discs. In the ensuing disc structures, we determined the regions where the dust-to-gas ratio exceeds the critical value for strong clumping found in simulations of the SI including external turbulence. Results: We find that the conditions for strong clumping are met within the first hundred thousand years in large regions of protoplanetary discs containing porous grains, provided that the CO snow line is taken into account. If the CO snow line is neglected, the conditions are met only very close to the inner disc edge early on, or over large areas well after 200,000 yr.

We report the measurement of the R3=[O III]5008/Hb ratios for 54 galaxies in the GLIMPSE-D survey. Thanks to gravitational lensing, our sample includes galaxies with -20 < Muv < -14 at z=6-9. We derive oxygen abundances using calibrated relationships. We observe a significant decline in R3 values below Muv > -18, which we interpret as evidence of decreasing metallicities in fainter regimes. We explore four prescription models of the evolution of R3 with UV emission based on the new measurements and results from previous surveys. Applying these models to the GLIMPSE [O III]+Hb luminosity functions, we measure and extrapolate the ionising photon production rate $\dot{N}_{ion}$ of galaxies down to very faint limits SFR(Ha) > 5e-3 Msun/yr. Our results support the dominant contribution of star-forming galaxies to reionisation, and are consistent with the recent discovery of ultra-faint metal-poor galaxies. Our measurements of the relative contribution of each luminosity bin show that galaxies with L(Ha)~1e41 to 1e42 erg/s dominate at 8<z<9, but the relative contributions become more uniform at $7<z<8$. Extreme models either under- or over-estimate the ionising photon budget, while intermediate models align with recent observational constraints.

As observations have yet to constrain the ionizing properties of the faintest (M$_{\rm UV}$ > -16) galaxies, their contribution to cosmic reionization remains unclear. The rest-frame ultraviolet (UV) continuum slope ($\beta$) is a powerful diagnostic of stellar populations and one of the few feasible indicators of the escape fraction of ionizing photons (f$_{\rm esc}$) for such faint galaxies at high-redshift. Leveraging ultra-deep JWST/NIRCam GLIMPSE imaging of strong lensing field Abell S1063, we estimate UV continuum slopes of 555 galaxies at z $>$ 6 with absolute magnitudes down to M$_{\rm UV}$ $\simeq -$12.5. We find a modest evolution of $\beta$ with redshift and a flattening in the $\beta$-M$_{\rm UV}$ relation such that galaxies fainter than M$_{\rm UV}$ $\sim -$16.5 no longer exhibit the bluest UV slopes. The 138 ultra-faint galaxies with M$_{\rm UV}$ $> -$16 are a diverse population encompassing dusty (30\%), old (15\%), and low-mass (50\%) galaxies. We apply the empirical $\beta$-f$_{\rm esc}$ relation from local Lyman continuum leakers, finding the mean f$_{\rm esc}$ peaks at $\sim 20\%$ at M$_{\rm UV}=-$16.5 and declines towards fainter galaxies, while remaining consistent with f$_{\rm esc}$ = 14\% within uncertainties, in agreement with recent radiative transfer simulations. Incorporating GLIMPSE constraints on the UV luminosity function, ionizing photon production efficiency, and escape fractions produces a reionization history consistent with independent observational constraints. Our results indicate galaxies with M$_{\rm UV}$ between $-18$ and $-14$ supplied $\sim 60\%$ of the ionizing photons to cosmic reionization, while the lower f$_{\rm esc}$ of fainter galaxies produces a natural cutoff in the ionizing photon production rate density.

A review of the current status of the field of Ultra-High-Energy Cosmic Ray (UHECR) including a summary of remaining open questions was presented in the white paper "Ultra-High Energy Cosmic Rays: at the Intersection of the Cosmic and Energy Frontiers" (Astropart. Phys. 147 (2023) 102794; arXiv:2205.05845). The authors concluded that two types of next-generation detectors are needed to answer these questions: high-accuracy instruments and detectors that maximize exposure at the highest energies. The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA), a proposed dual-satellite observatory, exemplifies the latter class and is designed to increase statistics of the highest-energy cosmic rays and to detect very-high-energy neutrinos following multi-messenger alerts. POEMMA-Balloon with Radio (PBR) implements a compact, balloon-borne version of the POEMMA concept, adapted for a Super-Pressure Balloon flight from Wanaka, New Zealand, with an expected campaign exceeding 20 days. PBR couples a wide field-of-view Schmidt telescope and a hybrid optical focal surface with a dedicated radio instrument to deliver simultaneous, complementary measurements of extensive air showers. The mission will validate the fluorescence detection strategy from space and raise technology readiness for a POEMMA-like space mission by observing UHECR-induced fluorescence light from suborbital altitudes, obtaining the first simultaneous optical Cherenkov and radio observations of high-altitude horizontal air showers above the cosmic-ray knee (E>3PeV), enabling energy-spectrum and composition studies at the PeV scale, and performing follow-ups of multi-messenger alerts to search for very-high-energy neutrinos via upward-going air showers. This paper summarizes the PBR payload and its expected performance.

Giant planets in the habitable zone may host exomoons with conditions conducive to life. In this paper we describe a method by which the Habitable Worlds Observatory (HWO) could detect such moons: broadband reflected-light lunar eclipses (e.g., the moon passing into the shadow of the planet). We find that an Earth-like moon orbiting a Jovian-size planet at 1au can outshine its host planet near 1 micron, producing frequent (days time-scale) lunar eclipses with depths of order 50%. We determine that single eclipse events out to $\sim$12pc may be detectable for Earth-like moons around giant planets, down to $0.9R_\oplus$. Detection of smaller moons, $\sim$0.5$R_\oplus$ (corresponding to about the size of Mars or Ganymede), may be possible, but would generally require multiple events for most systems. These several-hour events provide a clear pathway to detecting habitable moons with HWO, given sufficient stare-time on each system to detect lunar eclipses. The occurrence rate of habitable exomoons remains unconstrained, however, making the ultimate yield uncertain. HWO will be capable of placing the first meaningful constraints on the frequency of habitable exomoons around giant planets; if it is non-negligible, HWO could also search for life on these worlds, possibly with lunar eclipse spectroscopy.

We used more than $10^5$ Gaia DR3 line broadening vbroad measurements to examine stellar rotation as a function of stellar temperature, mass and age. The large sample clearly displays the Kraft break at $\sim 6{,}500$\,K, or mass of $\sim1.3\,M_{\odot}$-while vbroad are small, on the order of $10$-$20$ km/s, for stars cooler than the Kraft break, they sharply rise above the break, reaching up $\sim100$ km/s with temperature of $7{,}000$ K. To follow the stellar rotation as a function of age, we consider vbroad as a function of scaled age-stellar age divided by the relevant Terminal Age Main Sequence (MS), for four narrow mass bins. We find that stellar rotation deceleration is slow during the MS phase and fast afterwards for stars hotter than the break, whereas deceleration rate is relatively high and does not vary much for the cool stars. Our findings are consistent with the theory that stellar rotation slowing is due to magnetic breaking, emanating from magnetic fields that are anchored to the stellar convective envelopes. Therefore, deceleration is high in cool stars, but in hot stars only after they leave the MS and develop convective outer layers

Transient noise artifacts, or glitches, fundamentally limit the sensitivity of gravitational-wave (GW) interferometers and can mimic true astrophysical signals, particularly the short-duration intermediate-mass black hole (IMBH) mergers. Current glitch classification methods, such as Gravity Spy, rely on supervised models trained from scratch using labeled datasets. These approaches suffer from a significant ``label bottleneck," requiring massive, expertly annotated datasets to achieve high accuracy and often struggling to generalize to new glitch morphologies or exotic GW signals encountered in observing runs. In this work, we present a novel cross-domain framework that treats GW strain data through the lens of audio processing. We utilize the Audio Spectrogram Transformer (AST), a model pre-trained on large-scale audio datasets, and adapt it to the GW domain. Instead of learning time-frequency features from scratch, our method exploits the strong inductive bias inherent in pre-trained audio models, transferring learned representations of natural sound to the characterization of detector noise and GW signals, including IMBHs. We validate this approach by analyzing strain data from the third (O3) and fourth (O4) observing runs of the LIGO detectors. We used t-Distributed Stochastic Neighbor Embedding (t-SNE), an unsupervised clustering technique, to visualize the AST-derived embeddings of signals and glitches, revealing well-separated groups that align closely with independently validated Gravity Spy glitch classes. Our results indicate that the inductive bias from audio pre-training allows superior feature extraction compared to traditional supervised techniques, offering a robust, data-efficient pathway for discovering new, anomalous transients, and classifying complex noise artifacts in the era of next-generation detectors.

Ultra-faint galaxies at high-$z$ are fundamental elements of the early galaxy assembly, and spectroscopic characterization of this population is essential to understand the earliest galaxy evolution. Leveraging the ultra-deep JWST/NIRCam and NIRSpec observations of a gravitational lensing field of Abell S1063, taken as part of the GLIMPSE survey, we present spectroscopic properties of 16 galaxies fainter than $M_{\rm UV}=-17$ mag, including the metallicity, dust attenuation, and the ionizing photon production efficiency. The emission lines are generally quite strong, roughly half of which cannot be replicated with standard stellar populations and require an extreme ionizing source. We also identify relatively strong [OIII] emission lines from all sample galaxies, which indicates that the low-mass end of the mass-metallicity relation is extended down to $M_\star\sim10^6\ M_\odot$ at $z\sim6$. The strong [OIII] line detection from the lowest-mass galaxy among the sample ($M_\star\sim10^{5.6}\ M_\odot$) stands in contrast to recent reports of extremely metal-poor galaxy candidates at similar mass and redshift, suggesting that there could be two distinct pathways of the earliest metal enrichment as simulations have predicted. Interestingly, we detect both dust attenuation and galactic outflow in one of the sample galaxies with $M_\star=10^{6.6}\ M_\odot$ at $z=5.5$. All the dust, metal, and outflow contents in this galaxy can be consistently explained by supernovae (SNe), indicative of the key roles of SNe in the earliest galaxy assembly such as dust production, metal enrichment, stellar feedback, and baryon cycle.

This work describes the formalism for estimating thermonuclear reaction rates for astrophysical applications, emphasizing modern statistical approaches such as Monte-Carlo sampling and Bayesian models. We discuss related topics including the calculation of resonance energies from nuclear Q values, indirect estimates of particle partial widths, and matching of reaction rates at elevated temperatures to statistical-model results. We have evaluated available experimental data on cross sections, resonance energies and strengths, partial widths, life-times, spin-parities, and spectroscopic factors. Based on these results, we have estimated numerical values of 78 experimental charged-particle thermonuclear reaction rates for target nuclei in the A = 2 to 40 mass region, for temperatures ranging from 1 MK to 10 GK. For each reaction, three rate values are provided: low, median, and high, corresponding to the 16th, 50th, and 84th percentiles, respectively, of the cumulative reaction rate probability density distribution. Additionally, we present the factor uncertainty of each rate at each temperature grid point. These results enable users to sample the reaction rate probability density in nucleosynthesis calculations, facilitating uncertainty estimates of nuclidic abundances. The rates presented here refer to their laboratory values. For use in stellar model simulations, these values need to be corrected for the effects of thermal excitations of the interacting nuclei. For each reaction, we include graphs that illustrate the fractional contributions to the overall reaction rate along with the associated uncertainty. These visuals are designed to assist both stellar modelers and nuclear experimentalists by identifying the primary sources of rate uncertainty at specific stellar temperatures. A graphical comparison with earlier Monte-Carlo rates is also provided.

A leading theory of sunquake generation involves flare-accelerated particles depositing energy into the photosphere. Simulations of sunquake excitation suggest co-excitation with wavefronts propagating in the corona and chromosphere, similar to Moreton-Ramsey waves, and large-scale coronal propagating fronts (LCPFs). To investigate observational evidence for the particle-driven mechanism in LCPFs, we compare populations of events associated with and without coronal mass ejections (CMEs). CMEs are known to generate similar EUV shock waves. We employ a visual inspection of flare events that generate LCPFs using Atmospheric Imaging Assembly (AIA) and Large Angle and Spectrometric Coronagraph (LASCO) coronagraph images to find that coronal waves associated with CMEs propagate noticeably faster. Then we examine GOES soft X-ray (SXR) data of standalone flare events (those that generate coronal waves without CMEs), focusing on soft X-ray (SXR) characteristics related to magnetic energy release rate. This reveals that such standalone or confined flares differ from sunquake flares: they are less impulsive and energetic than sunquake flares. However, they are more impulsive but less energetic than LCPF-associated flares with a CME. In particular, coronal waves accompanied by CMEs exhibit significantly higher volume emission measures, suggesting a different generation mechanism.

Isotopologues play an important role in solar system cosmochemistry studies, revealing details of early planet formation physics and chemistry. Oxygen isotopes, as measured in solar system materials, reveal evidence for both mass-dependent fractionation processes and a mass-independent process commonly attributed to isotope-selective photodissociation of CO in the solar nebula. The sensitivity of JWST's MIRI-MRS enables studies of isotopologues in the terrestrial planet-forming regions around nearby young stars. We report here on a search for H$_2^{18}$O in 22 disks from the JDISC Survey with evidence for substantial water vapor reservoirs, with the goal of measuring H$_2^{16}$O/H$_2^{18}$O ratios, and potentially revealing the predicted enhancement of H$_2^{18}$O caused by isotope-selective photodissociation. We find marginal detections of H$_2^{18}$O in six disks, and a more significant detection of H$_2^{18}$O in the disk around WSB 52. Modeling of the detected H$_2^{18}$O lines assuming an ISM ratio of H$_2^{16}$O/H$_2^{18}$O predicts H$_2^{18}$O features consistent with observations for four of the modeled disks, but stronger H$_2^{18}$O features than are observed in three of the modeled disks, which includes WSB 52. Therefore, these latter three disks require a higher H$_2^{16}$O/H$_2^{18}$O ratio than the ISM in the water-emitting region, in contrast to long-standing theoretical expectations. We suggest that either the H$_2^{18}$O-rich water has been removed from the emitting region and replaced by H$_2^{18}$O-poor water formed by reactions with $^{18}$O-poor CO, or that the gas-phase water is depleted in $^{18}$O via mass-dependent fractionation processes at the water snowline.

We present HST-COS FUV and -STIS optical observations towards the young accreting brown dwarf 2MASS-J08440915-7833457 (J0844) from the ULLYSES DDT Program. We analyse hot FUV lines such C IV, Si IV, and N V, as well as fluorescent emission from H2. Despite evidence for accretion, the C IV line profiles are narrower than in typical classical T Tauri stars (CTTSs), resembling weak-lined T Tauri stars more closely. Additionally, the C IV integrated line flux does not follow the level expected of an accreting object in the magnetically saturated regime. However, comparing J0844 to appropriate low mass analogs, J0844 does show excess C IV emission characteristic of accretion, suggesting the magnetic saturation level may need to be redefined for the lowest mass objects. The C IV/Si IV emission line ratio is found to be 20, which is higher than most CTTSs, with a few exceptions (e.g., TW Hya). We fit the STIS optical spectrum to calculate an accretion rate, which we find to be 4.2 x 10-11 Msol/yr. The accretion rate found based on the empirical LCIV-Macc relationship is twoorders of magnitude higher, suggesting this relationship may not hold at the lowest masses. We find the H2 emission appears to originate within the co-rotation radius, pointing to either disc truncation well inside the co-rotation radius or additional sources of H2 emission that we do not consider (e.g., from the accretion flow itself). These data provide an extension of our current understanding of accretion and inner disc conditions to the relatively unexplored lowest mass regime.

We present a physically-grounded population model for optical tidal disruption events (TDEs) that combines first-principles hydrodynamic simulations of stellar disruption with statistical inference of the underlying stellar and black hole populations. The model's prediction of peak luminosity is based directly on recent global simulations that follow the disruption self-consistently and contains no tunable parameters related to the emission physics. We construct the predicted joint distribution of peak luminosity and black hole mass, including both full and partial disruptions, and compare it to a sample of observed TDEs using Bayesian inference and Markov chain Monte Carlo sampling. We find that the model reproduces the distribution in the ($M_{BH},L_{peak}$) plane for the bulk of the observed TDE population with good statistical consistency. The data strongly favor an old stellar population, with a sharp suppression of stars above $M_* \simeq 1.5 - 2 M_\odot$. They also indicate that, at fixed stellar mass, the volumetric TDE rate is nearly independent of black hole mass. Partial disruptions contribute a substantial fraction ($\sim 30\%$) of detected events in flux-limited samples and are essential for reproducing the observed distribution. The inferred population properties are robust to different approximations to the stellar mass-radius relation, although the event rate at high luminosity is sensitive to the form of this relation for massive stars. We predict a large population of difficult to detect low luminosity TDEs, implying that the true volumetric TDE rate may exceed that inferred from present samples by up to an order of magnitude.

In a dense star cluster core, a tidal disruption event (TDE) of a white dwarf (WD) can occur if the WD passes within the tidal radius of an intermediate-mass black hole (IMBH). Very close encounters cause extreme tidal compression in the WD, raising temperatures enough to induce runaway fusion and produce a thermonuclear supernova (SN). Using the hydrodynamics code AREPO augmented with a 55-isotope nuclear reaction network, we performed high-resolution simulations of the TDE of a $0.6$ Msun C/O WD by a $500$ Msun IMBH for different values of the scaled impact parameter $b$ (i.e., the ratio of periapsis distance to tidal radius). Closer encounters produce combined TDE+SN events, with a partial burning of $^{12}$C and $^{16}$O into heavier isotopes -- the $^{56}$Ni fractions of the disrupted WD material vary from 1% at $b = 0.19$ to 82% at $b = 0.10$, while wider ones ($b \gtrsim 0.20$) lead to standard TDEs. In all cases, the material away from the denser regions remains unburnt, spanning a wide range of radial velocities. Such WD TDEs also exhibit a central cavity, wherein little material is found below a radial velocity of several $1000 \,\mathrm{km s}^{-1}$. We also performed 1D and 2D radiative-transfer calculations for these WD-TDEs using the codes CMFGEN and LONGPOL, respectively, covering epochs from a few days to one hundred days. We recover the typical rise times and peak luminosities of SNe Ia, but with an extremely strong viewing-angle dependence of both light curves and spectra. At nebular times, isolated strong emission lines like [Ca ii] {\lambda}{\lambda} 7291, 7323 may appear both displaced and skewed by many $1000 \,\mathrm{km s}^{-1}$ -- such extreme offsets are harder to identify at earlier times due to optical depth effects and line overlap. WD TDEs may produce a diverse set of transients with extreme asymmetry and peculiar composition.

In addition to fast radio burst (FRB) searches carried out using dedicated surveys, a number of radio observatories take advantage of commensal opportunities with large facilities in which observations for other projects can be searched for FRBs and other transient sources. We present the results from one such effort, the first 24,186 hours of the GREENBURST search for dispersed radio pulses with the Green Bank Telescope (GBT). To date, GREENBURST has detected a total of 50 pulsars and three FRBs. One of the pulsars, PSR J0039+5407, has a period of 2.2 s and was previously unknown. Using follow-up observations with the Canadian Hydrogen Intensity Mapping Experiment, we found a timing solution for this pulsar which shows it to have a characteristic age of 2 Myr. Additional GBT observations show the pulsar has a very high nulling fraction ($\sim70-80\%$). All three of the FRBs are repeating sources that were previously known and were being monitored by the GBT as part of other projects. A major challenge for GREENBURST in the discovery of new FRBs is its single beam. This makes it hard to distinguish some of the pulses from sources of radio frequency interference. We highlight this problem with a case study of an FRB-like pulse that initially passed our interference filters. Upon closer inspection, the event appears to be part of a longer-duration narrow-band source of unknown origin. Further observations and monitoring are required to determine whether it is terrestrial or celestial.

(Abridged) Complex organic molecules (COMs) are considered essential precursors to prebiotic species. While COMs were once expected to be efficiently destroyed under UV-irradiated conditions, detections in photodissociation regions (PDRs) have challenged this view. However, the mechanisms by which UV radiation contributes to their formation are still uncertain. Here, we present moderately resolved maps of simple and complex organic molecules at the UV-illuminated edge of the Horsehead nebula, obtained by combining ALMA and IRAM 30m single-dish observations at $\sim 15^{\prime\prime}$ resolution. We analyze the spatial distribution of species such as C$^{17}$O, CH$_2$CO, CH$_3$CHO, HNCO, CH$_3$CN, and HC$_3$N. By incorporating previous C$^{17}$O and C$^{18}$O single-dish data as well as PdBI maps of H$_2$CO and CH$_3$OH, we derive profiles of gas density, temperature, thermal pressure, and column densities of the organic species as a function of distance from the UV source. Our results show that most organic species$-$particularly H$_2$CO, CH$_2$CO, CH$_3$CHO, HNCO, and CH$_3$CN$-$exhibit enhanced column densities at the UV-illuminated edge compared to cloud interiors, possibly indicating efficient dust-grain surface chemistry driven by the diffusion of atomic C and radicals produced via photodissociation of CO and CH$_3$OH, as supported by recent laboratory experiments. The exceptions, HC$_3$N and CH$_3$OH, can be attributed to inefficient formation on dust grains and ineffective non-thermal desorption into the gas phase, respectively. Additionally, contributions from gas-phase hydrocarbon photochemistry$-$possibly seeded by grain-surface products$-$cannot be ruled out. Further chemical modeling is needed to confirm the efficiency of these pathways for the studied species, which could have important implications for other cold, UV-irradiated environments such as protoplanetary disks.

We study a string-inspired dilaton cosmology in the Damour--Polyakov (DP) regime using dynamical-systems methods, aiming to make explicit how cosmological relaxation controls deviations from the equivalence principle. Working in the Einstein frame, we consider a spatially flat FLRW universe filled with pressureless matter and a universally coupled dilaton. Expanding the conformal coupling function and the scalar potential around the least-coupling point, we obtain a closed and self-consistent autonomous system governing the late-time evolution of the scalar-matter sector. The resulting phase space contains a stable fixed point associated with least coupling, approached only asymptotically along cosmological trajectories. Therefore, at any finite epoch the solution typically retains a small displacement from the fixed point. In the DP regime this finite-epoch displacement sets the ambient coupling, and thus determines the magnitude of fifth-force effects and deviations from the equivalence principle in the nonrelativistic limit. By linearising the system around a finite-epoch reference state, we show that the damping of the displacement is controlled by the Jacobian eigenvalues of the DP fixed point. This yields a direct dynamical estimate of how rapidly deviations from the equivalence principle are reduced during cosmological evolution. The mechanism is global and cosmological in origin, and is conceptually distinct from local environmental screening as in chameleon or symmetron scenarios. Overall, our results illustrate how phase-space techniques provide a clear bridge between cosmological dynamics and weak-field departures from General Relativity.

Observations of binary black hole (BBH) mergers provide a unique window into the lives of massive stars across cosmic time. Connecting redshift-dependent merger properties to massive star progenitors requires accurate models of cosmic star formation and chemical enrichment histories. Analytical fits for the metallicity-specific cosmic star formation rate density S(Z, z) are commonly used as proxies for the complex underlying star formation history, yet they remain unconstrained. Using the IllustrisTNG cosmological simulations, we evaluate the accuracy of these analytical S(Z, z) prescriptions and assess how simulation resolution and volume affect the inferred S(Z, z). By coupling the simulated and analytical S(Z, z) to the population synthesis code COMPAS, we investigate the resulting BBH merger rates and mass distributions. We find that analytical S(Z, z) prescriptions can overestimate BBH merger rates at high redshift ($z \gtrsim 6$) by up to a factor of $10$-$10^4$, depending on cosmological simulation resolution, and can introduce spurious features in the BBH mass distribution. For example, they can produce an artificial feature near $8\,M_\odot$ in the primary mass distribution at $z \lesssim 2$, which is absent when using the full simulation-based S(Z, z), while simultaneously suppressing high-mass features. These discrepancies arise because simple analytical models fail to capture a high-metallicity bump and a more flattened low-metallicity tail in the simulated S(Z, z) metallicity distribution. Our results highlight the importance of accurate star formation histories for modeling BBH populations, demonstrate the limitation of widely used analytical S(Z, z) fits, and underscore the need for careful integration of cosmological simulations, analytical fits, and population synthesis when interpreting gravitational-wave observations.

We present a detailed analysis of $\gamma$-ray emission from the middle-aged supernova remnant (SNR) S147 (G180.0$-$1.7) using approximately 16.5 years of Fermi-LAT data. Spatially, a new extended $\gamma$-ray component distinct from the emission associated with the H$\alpha$ filaments of the SNR shell is identified. This new component exhibits a strong spatial correlation with dense molecular clouds (MCs) identified in CO emission at Local Standard of Rest velocities of $0$-$5\,\mathrm{km\,s^{-1}}$. Spectrally, the cloud-associated emission implies an underlying cosmic-ray (CR) proton population described by a hard power law with an index of $\Gamma \approx 2.1$, compatible with the standard diffusive shock acceleration prediction. We interpret the $\gamma$-ray emission in this region with a hadronic scenario involving two distinct CR populations: trapped CRs reaccelerated within the radiative SNR shell as proposed in previous work, and escaping CRs illuminating the nearby MCs. The derived CR proton intensity in the MC region significantly exceeds the local Galactic background measured by AMS-02, strongly suggesting that the cloud is illuminated by particles accelerated by S147. These findings provide observational evidence for CR escape during the earlier evolutionary phases of this middle-aged SNR and highlight S147 as a promising candidate for detection at TeV energies by LHAASO.

Observational surveys show that at least ~ 30% of short-period multiplanetary systems host tightly packed planets, some of which are locked in stable chains of mean-motion resonances. Despite recent progress, the dynamical stability of these systems remains only partially understood. Numerical simulations have established a general exponential increase in system lifetime with orbital separation, with mean-motion resonances playing a key role in regulating stability. Tightly packed three-planet systems exhibit a distinctive behavior not seen in higher-multiplicity systems: a small yet significant region of phase space is anomalously stable. This study investigates the dynamics of extremely compact three-planet systems, focusing on anomalously long-lived configurations and their connection to resonant chains observed in exoplanetary systems. We perform numerical integrations of coplanar, initially circular, equal-mass three-planet systems over stellar-lifetime timescales and at high resolution in orbital separation, and interpret the results in the context of recent analytical work. We identify regions of phase space hosting anomalously stable orbits, including systems surviving multiple orders of magnitude longer than predicted by the exponential trend. We demonstrate a clear link between stability and isolated three-body mean-motion resonances, showing that extremely compact systems can remain stable when captured into a small subset of isolated zeroth-order resonances. Stability further depends on the initial orbital longitudes and on the interplay between the three-body and two-body resonance networks.

We investigate longitude-velocity ($\ell$-$v$) diagrams as a diagnostic tool to study the metallicity structure of the Milky Way (MW) disk. The present-day metallicity structure encodes the imprint of the Galaxy's formation, assembly, and secular evolution. Using oxygen abundances from HII regions across the MW disk, together with MW-mass galaxies from the Feedback in Realistic Environments (FIRE-2) cosmological simulations, we show that $\ell$-$v$ diagrams trace radial metallicity gradients and non-axisymmetric azimuthal metallicity variations. Because they do not rely on distance measurements, $\ell$-$v$ diagrams complement face-on maps for studying metallicity structure. In the MW, we detect the radial metallicity gradient in $\ell$-$v$ space, but current HII region oxygen abundance errors are too high to reveal azimuthal variations. In the FIRE-2 MW-mass galaxies, the radial gradient is evident in $\ell$-$v$ diagrams regardless of observer location, but anomalous gas kinematics can mimic azimuthal metallicity variations. We term these "anomalous motions", which have an excess local standard of rest (LSR) velocity tail 3 times larger in the FIRE-2 simulations compared to the MW. Our results highlight $\ell$-$v$ diagrams as a largely unexplored tool for probing metallicity structure without requiring distances, and underscore discrepancies between the gas kinematics in the FIRE-2 simulations and those in the MW.

We perform a data-driven test of the FLRW metric and the flatness of the Universe, independently of any Dark Energy model, and in light of the latest DESI DR2 results. We use Pantheon+ and DESY5 SNIa data to reconstruct the distance modulus, dimensionless comoving distance and Hubble parameter, using an iterative smoothing algorithm. Then, combining the various reconstructions with the recent BAO measurements from DESI DR2, we perform the $\mathcal{O}_k$ diagnostic, a litmus test of the FLRW metric and the flatness of the Universe. We obtain robust results that do not depend on Dark Energy models and test some of the underlying hypotheses of the concordance model. We find that when the reconstructed $\mathcal{O}_k$ diagnostic is consistent with the FLRW metric, then the median value of $\Oko$ over all reconstructions that provide an improved fit relative to the flat $\Lambda$CDM model are: ${\Omega}_{k,0}^\text{med} = 0.035 ^{+0.046}_{-0.079}\pm 0.037$ for the Pantheon+ \& DESI DR2 data combination, ${\Omega}_{k,0}^\text{med} = 0.092 ^{+0.055}_{-0.132} \pm 0.064$ for the same data but with the Pantheon+ SNIa cut at redshift $z=1.13$, which is the maximum redshift of the DES~Y5 data, and ${\Omega}_{k,0}^\text{med} = -0.119^{+0.113}_{-0.047}\pm 0.043$ for DES~Y5 \& DESI DR2. The first uncertainties correspond to the spread in $\Oko$ over all reconstructions, followed by the median 1$\sigma$ error.

We present a comprehensive study of perturbation theory for neutrino decoherence in power-law correlated turbulent matter, establishing rigorous convergence criteria and providing detailed numerical validation. Starting from the exact Laplace-space solution derived from the generalized master equation with memory kernel $K(t) \propto t^{-\nu}e^{-t/\tau_c}$, we develop a systematic perturbation expansion in the turbulence strength parameter $\xi$. The expansion is performed around the high-density matter basis where $\cos 2\theta_m \approx 1$, rather than the vacuum basis, reflecting the physical conditions in supernova cores. We obtain explicit expressions for the first few perturbation terms and derive the general structure of higher-order terms, which involve Mittag-Leffler functions that emerge from the fractional dynamics. Using high-precision numerical methods (multiple-precision arithmetic and asymptotic expansions), we analyze the convergence radius and rate of the perturbation series. We find that for $\xi < \xi_c \approx 0.8$, the series converges with error decreasing geometrically. For $\xi = 0.16$ (typical supernova conditions), third-order perturbation theory achieves $\sim 1\%$ accuracy. We provide practical guidelines for applying perturbation theory to realistic astrophysical scenarios and validate all analytical results with extensive numerical computations. Our work clarifies several subtle aspects of the perturbative approach that were not addressed in the original literature, offering a complete toolkit for researchers studying neutrino-turbulence interactions. In particular, we systematically address the ultraviolet divergence of the correlation function at short time scales for spectral indices $\nu \geq 1$, introducing a physical small-scale cutoff regularization that ensures mathematical rigor for the fractional master equation and perturbative expansion.

According to the canonical planet formation theory, planets form "in-situ" within a planetesimal disk via runaway and oligarchic growth. This theory, however, cannot naturally account for the formation timescale of ice giants or the existence of diverse exoplanetary systems. Planetary migration is a key to resolving these problems. One well-known mechanism of planetary migration is planetesimal-driven migration (PDM), which can let planets undergo significant migration through gravitational scattering of planetesimals. In our previous paper (Jinno et al. 2024, PASJ, 76, 1309), we investigated the migration of a single planet through PDM, addressing previously unexplored aspects of both the gravitational interactions among planetesimals and the interactions with disk gas. Here we perform the first high-resolution simulations of planet formation from a large-scale planetesimal disk, incorporating planet-gas disk interactions, planet-planetesimal interactions, gravitational interactions among all planetesimals, and physical collisions between planetesimals to investigate the role of PDM in the planet formation process. Our results show that protoplanets undergo dynamic inward/outward migrations during the runaway growth stage via PDM. Moreover, orbital repulsion combined with PDM tends to make two groups of protoplanets, outer ones going outward and inner ones going inward. Such dynamic migration significantly influences the early stages of planetary formation. These findings provide a viable pathway for the formation of Earth-like planets and ice giants' cores. Furthermore, they suggest that a standard protoplanetary disk model can account for the planetary migration necessary to explain diverse exoplanetary systems without the need for additional hypotheses.

Saturn's Great Storm of 2010-2011 has produced two stratospheric hot spots, the "beacons," that eventually merged to produce a gigantic one in April and May 2011. This beacon perturbed stratospheric temperatures, hydrocarbon, and water abundances for several years. We aim to assess whether the beacon induced any perturbation in another oxygen species, namely CO. A second goal is to measure how the vortex perturbed the stratospheric wind regime. We conducted interferometric observations of Saturn in the submillimeter range with SMA and ALMA to spatially resolve the CO (J=3-2) and (J=2-1) emissions, respectively. We used a previously determined CO vertical profile as a template, to search for (i) the meridional distribution of CO and (ii) variations of the CO abundance associated with the storm. The high spatial and spectral resolutions of the ALMA observations enabled us to retrieve the winds from the Doppler shifts induced by the winds on the lines. Despite limitations resulting from the removal of baseline ripples, we find a relatively constant meridional distribution of CO. The average CO mole fraction implied by the adopted and rescaled 220-year-old-comet-impact vertical profile is (1.7$\pm$0.7)$\times10^{-7}$ at 0.3\,mbar, i.e., where the contribution functions peak. We also find that the CO abundance has not been noticeably altered in the beacon. The winds measured at 1\,mbar show striking differences with those measured in 2018, after the demise of the beacon. We find the signature of the vortex as an anticyclonic feature. The equatorial prograde jet is 100 to 200 m.s$^{-1}$ slower, and broader in latitude, than in quiescent conditions. We also detect several prograde jets in the southern hemisphere. Finally, we detect a retrograde jet at 74$^\circ$N which could be a polar jet caused by the interaction of the Saturn magnetosphere with its atmosphere.

The 6.7 GHz methanol maser in a high-mass star-forming region G33.641$-$0.228 is known to exhibit burst-like flux variability due to an unknown mechanism. To investigate the burst mechanism, we conducted high-cadence flux and circular polarization monitoring observations, simultaneously using left- and right-hand circular polarizations. We found that the flux density increased and decreased on a short timescale of 0.3 d during a burst. We also found strong circular polarization, reaching up to 20\% in the component exhibiting the bursts. Circular polarization of 0--20\% was continuously observed from 2009 to 2016, even in the quiescent period. The polarization also varied on timescales of less than one day. When a burst occurred and the flux density increased, the circular polarization decreased to zero. To explain the observational properties of the flux variability and circular polarization, we propose a model in which an explosive event similar to a solar radio burst occurs on the line of sight behind the maser cloud, producing circularly polarized continuum emission due to gyro-synchrotron or gyro-resonance radiation, which is then amplified by the maser.

Type Ia supernovae (SNe), thermonuclear explosions of white dwarfs in binary systems, are widely used as standard candles owing to the empirical width-luminosity relation of their light curves. Recent theoretical and observational studies indicate a diversity of progenitor systems and explosion mechanisms. In the supernova remnant (SNR) phase, the diversity in Fe-K$\alpha$ centroid energies and line luminosities suggests variations in the underlying explosion mechanisms. X-ray spectra of SNRs, which trace shocked ejecta and the surrounding medium, are crucial diagnostics of progenitor systems and explosion physics. Thanks to recent advances in spectroscopy with XRISM, high-resolution X-ray spectroscopy enables 3-D diagnostics, including line-of-sight velocities. In this study, we perform 3-D hydrodynamic simulations of SNRs from six Type Ia explosion models: two each of pure deflagration, delayed detonation, and double detonation. Each model is evolved for 1000 years in a uniform medium, consistently accounting for non-equilibrium ionization. Our efficient numerical scheme enables systematic parameter surveys in full 3-D. From these models, we synthesize X-ray spectra with $\sim$1 eV resolution, exceeding XRISM/Resolve's spectral resolution. This work presents the first calculation of X-ray spectra for Type Ia SNRs derived from 3-D hydrodynamic simulations that follow the evolution self-consistently from the SN phase into the SNR phase. Our results show inter-model diversity in the X-ray spectra. Asymmetric, red- and blueshifted line profiles arise from the 3-D ejecta distributions. These findings demonstrate that 3-D SNR modeling can reproduce the observed diversity of Type Ia SNRs and provide qualitative constraints on progenitor systems and explosion mechanisms.

We investigate year-scale quasi-periodic oscillations in the $\gamma$-ray emission of the high-redshift flat-spectrum radio quasar PKS~2052$-$47 using monthly binned \emph{Fermi}-LAT data spanning MJD~54727.99--58507.99. To assess the statistical significance of periodic features embedded in red-noise-dominated variability, we apply several complementary timing techniques, including the Lomb--Scargle periodogram, weighted wavelet $Z$-transform, date-compensated discrete Fourier transform, REDFIT assuming an AR(1) process, and damped random walk modelling. The analyses reveal a dominant quasi-periodic modulation on a timescale of $\sim600$--630~d, together with a secondary longer-timescale feature near $\sim1050$--1110~d. Monte Carlo simulations show that the shorter-period signal exceeds the highest local confidence levels, while the longer modulation reaches $\gtrsim99$ per cent local significance in several tests; independent DRW-based simulations place both peaks above the $4\sigma$ envelope in the Lomb--Scargle analysis. Spectral-window diagnostics indicate that the detected periodicities are not artefacts of uneven sampling, and a sliding-window analysis shows that the QPO power is episodic across the $\sim11$~yr baseline. We discuss possible physical interpretations in terms of geometric Doppler modulation associated with jet precession or helical motion, accretion-driven instabilities, and SMBBH-induced dynamics.

Magnetic fields play a central role in black hole astrophysics, powering relativistic jets and other energetic phenomena. While near-horizon magnetic field is usually assumed to originate from the accretion flow, additional large-scale magnetic fields - such as those supplied by a companion neutron star in stellar-mass binaries or by galactic fields around supermassive black holes - may also affect the horizon-threading flux. In this work, we study the superposition of a weak arbitrarily inclined external uniform magnetic field with the internal Blandford-Znajek split-monopole field around a Schwarzschild black hole. This setup generically gives rise to magnetic null points, where the total field vanishes. We compute the magnetic flux through an arbitrarily tilted hemisphere of the event horizon and show that the flux can be substantially suppressed by the external field. In the axisymmetric case, the flux can even vanish completely. However, with nonzero inclination, complete cancellation becomes impossible, despite significant reduction. We further explore the ionization and subsequent particle acceleration from a Keplerian accretion disk, finding that efficient collimated outflows persist even under significant field inclination. We show that the acceleration is critically dependent on the external field orientation, with the escape fraction maximized at non-zero inclinations due to the destabilization of trapping zones and minimized in the anti-aligned configuration, where closed magnetic loops effectively suppress the outflow. We discuss the astrophysical implications of these findings, proposing that geometric flux cancellation can serve as a mechanism for jet quenching in compact binaries and offering an explanation for the lack of a prominent large-scale jet in Sgr A*.

We use ALMA CO(1-0) observations and VLT/MUSE rest-frame optical data of the ultraluminous infrared galaxy (ULIRG) IRAS20100-4156 at $z=0.1297$ to characterize its powerful outflow in multiple phases using tracers of cold molecular, ionized, and neutral atomic gas and dust as well. Our analysis uses the correspondence with the stellar velocity field to split the complex emission line profiles of the CO(1-0) line into components in gravitational and non-gravitational motion. We find a massive ($8\times10^{9}\,M_\odot$) molecular outflow containing about 40% of the total molecular gas mass in the system. The outflow shows a bi-conical morphology centered on the brightest galaxy in the merger, oriented along its minor axis and extending to $\sim5\,\mathrm{kpc}$. This outflow has a characteristic velocity of $170\,\mathrm{km/s}$, an outflow mass rate of $700\,M_\odot/\mathrm{yr}$, a depletion time of $16\,\mathrm{Myr}$, and energetics consistent with star formation as a driver. The neutral atomic and ionized gas phases traced by NaI absorption and H$\alpha$ emission show counterparts to the blueshifted cold molecular outflow but are only 15% and 3% as massive. None of the three gas phases show any signs of slowing down over the extent at which we detected the outflow, suggesting an acceleration mechanism acting on the outflowing gas at kiloparsec scales. We also detect $3.5\times 10^7\,M_\odot$ of dust, traced by optical extinction in the MUSE data, in the blueshifted outflowing cold molecular gas. The ionization state of the non-outflowing gas is consistent with star formation, while the outflowing component shows shock-like ionization. We conclude that the multiphase outflow in IRAS20100-4156 originates in the southeast nucleus of the merger and is driven by the starburst activity there, with radiation pressure likely playing a significant role in its acceleration.

We investigate the signature of the jet-ejecta interaction in early kilonova (t < 1day) using detailed atomic opacities developed in Banerjee et al. (2020, 2024), appropriate for early times (t~1hour after merger). We explore jets with different powers and opening angles. We find that the presence of the jet shifts the spectral peak to longer wavelengths, with the strongest effect near the polar viewing angle. This occurs because the jet creates a thin, low-density outer layer ahead of the bulk ejecta. The opacity of this layer can be as high as kappa ~200 cm2/g, causing photons to escape from cooler, faster-moving outer layer rather than from the hot inner ejecta. The bolometric light curves likewise exhibit a clear imprint of the jet-ejecta interaction, showing suppressed early-time luminosity near polar viewing angles compared to the equatorial one, as the photosphere resides in this thin layer where radioactive heating is lower than in the bulk ejecta. These signatures are also evident in multi-color light curves, particularly in the ultraviolet and u-bands. In the Swift-UVW2 band at t~= 0.15 days for a source at 100 Mpc, the ultraviolet luminosities can reach ~ 19.5 mag if no jet is present, while the presence of the jet can make it fainter by ~ 2.5 mag. The strongest observational signature occurs in the UVEX-NUV, Swift-UVW2, and UVM2 bands, which remains detectable out to viewing angles of ~ 60 deg for t <=1 days. Rapid follow-up with future ultraviolet facilities, such as ULTRASAT and UVEX, will provide powerful probes of jet-ejecta interaction through early-time kilonova observations.

Restricted by event horizon suppression, tidal disruption events (TDEs) provide a unique window into otherwise hidden supermassive black holes (SMBHs) at the lower end of the mass spectrum, allowing the connection between star formation and SMBH mass to be explored across a broad stellar mass range. We derive stellar masses and specific star formation rates using Prospector fits to UV-MIR broadband spectral energy distributions (SEDs) for 42 TDE hosts, together with a high-mass comparison sample, and combine these with SMBH mass estimates from the literature. We first verify our approach by reproducing the established result that quenched galaxies host more massive SMBHs than star-forming systems at fixed stellar mass, a result widely interpreted as evidence for SMBH growth driving the blue-to-red sequence transition. However, examining the TDE sample in isolation reveals a trend reversal at lower masses, uncovering a surprising population of low-mass ($10^{9.6} \lesssim M_{\rm gal} \lesssim 10^{10.5}$ M$_\odot$), quenched galaxies hosting SMBHs systematically less massive ($M_{\rm BH} \lesssim 10^{6.5}$ M$_\odot$) than those in star-forming galaxies of comparable stellar mass. After ruling out degeneracies in our SED fits, we conclude that this reflects a physical difference in the quenching mechanism between these TDE hosts and the more massive galaxies. This is unlikely to be driven by AGN feedback, and could instead result from environmental processes, which can end star formation and hinder SMBH growth. We also show that the quenched and post-starburst population within the TDE sample is likely under-represented due to selection biases, suggesting the true fraction could be even higher than observed.

The physical mechanism producing Anomalous Microwave Emission (AME) has been an unresolved puzzle for close to 30 years. One candidate mechanism is rotational emission from polycyclic aromatic hydrocarbons (PAHs) which can have the necessary electric dipole moment and size distribution to account for the AME in representative interstellar environments. However, previous investigations have found that AME is better correlated with the far-infrared dust emission rather than the PAH emission. In this work we analyze the correlations between the AME and the PAH and far-infrared dust emission using the 3.3 $\mu$m PAH emission feature as observed by band 3 of the Diffuse Infrared Background Experiment (DIRBE). This analysis builds on previous work conducted in individual molecular clouds and extends it into fainter, more diffuse structures. In addition, we utilize the COSMOGLOBE DIRBE reduction for this work, building on previous studies that used the original DIRBE data set. We find that the AME is better correlated with far-infrared dust emission ($\rho\sim$0.9) than the PAH emission ($\rho\sim$0.7) in the central $|b|\leq$ 10\degree\ region of the sky. This could indicate either that non-PAH dust grains or an alternative physical emission mechanism is primarily responsible for the AME in the Galactic Plane, or that the excitation conditions for mid-infrared emission and for AME from PAHs differ substantially.

Earth-like planets orbiting in the habitable zone of K- to G-type stars create an RV effect in amplitude of less than 1 \si{\meter\per\second} and have orbital periods of hundreds of days. Only long-term RV surveys with sub-meter per second precision instruments can explore the outer regions of Sun-like stars and look for Earth-like planets and super-Earths. We present the analysis of the K-type star HD 176986. It has a brightness of V=8.45 mag and a distance from the Sun of d = 27.88 pc. This star hosts a known planetary system of two super-Earths. We joined historical datasets with new data collected in an ongoing blind search program. We took advantage of recently developed tools for RV extraction and stellar activity filtering. The analysis of activity indicators permits us to determine the period of the magnetic cycle of the star alongside its rotation period. We performed a joint analysis of RVs and activity indicators through multidimensional GPs to better constrain the activity model in RVs and avoid overfitting. We detected a new planet orbiting the star and retrieved the two known planets. HD 176986 b has an orbital period of 6.49164$^{+0.00030}_{-0.00029}$ d and a minimum mass of 5.36 $\pm$ 0.44 M$\oplus$. HD 176986 c has an orbital period of P$_c$ = 16.8124 $\pm$ 0.0015 d and a minimum mass of 9.75$_{-0.64}^{+0.65}$ M$\oplus$. HD 176986 d has an orbital period of 61.376$^{+0.051}_{-0.049}$ d and a minimum mass of 6.76$_{-0.92}^{+0.91}$ M$\oplus$. From the analysis of activity indicators, we find evidence of a magnetic cycle with a period of 2432$_{-59}^{+64}$ d, along with a rotation period of 36.05 $_{-0.71}^{+0.67}$ d. We discover a new planet in the multi-planet system orbiting the K-type star HD 176986. All the planets have minimum masses compatible with super-Earths or mini-Neptunes.

There is a fundamental lack of understanding as to why quasars that are otherwise very similar can have such a wide range of radio jet powers, and the large-scale environment is thought to play an important role. We investigate the spatial clustering properties of 225,382 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) within the LOFAR Two-metre Sky Survey (LoTSS) Data Release 2 footprint, split by the statistically-calculated fraction of their radio flux densities contributed by jets (relative to the contribution from star formation). We find a positive correlation between the clustering strengths of quasars and their jet fraction, where quasars with a higher jet fraction have a higher clustering amplitude measured by their two-point correlation functions. We show that this correlation is unlikely related to differences in BH masses or bolometric luminosities. Quasars dominated by powerful jet activities generally reside in dark matter haloes $10-100$ times more massive than those without strong jets, with typical halo masses of $10^{13-14}\ h^{-1}M_\odot$, establishing a robust link between powerful AGN jets and rich cluster environments. Our results demonstrate that halo mass is important for determining the power of radio jets, but suggest that there is no minimum dark matter halo mass or BH mass required for the triggering of jets. The observed correlation suggests that BH spin is likely to play a minor role in jet production; instead, the key driver could be the presence of a strong magnetic flux.

Understanding the climates of terrestrial exoplanets and the detectability of biosignatures is an inherently interdisciplinary challenge, requiring the integration of insights from Solar System exploration, exoplanet observations and climate science. Building from Earth as the only known inhabited planet, NCCR PlanetS has developed models, tools and observational strategies to assess planetary environments far beyond direct reach. Between 2018 and 2025, PlanetS made major contributions across theory, modelling, instrumentation and mission preparation. On the modelling side, the Generic Planetary Climate Model enabled climate studies across a wide range of planetary regimes, from early Venus to temperate terrestrial exoplanets including Proxima b, incorporating advanced developments such as a dynamical slab ocean. In parallel, the THOR global climate model was developed to avoid Earth-centric assumptions and to stably simulate diverse atmospheric regimes. PlanetS has also advanced atmospheric retrieval techniques combining forward modelling, Bayesian inference and machine learning, applied to targets ranging from Solar System bodies to exoplanet phase curves and directly imaged spectra. These efforts have helped assess the scientific return of future missions, notably the Large Interferometer for Exoplanets (LIFE) and to define instrumental requirements for detecting Earth-like atmospheres and biosignatures. Within the Solar System, PlanetS contributed key technologies for biosignature detection, including ORIGIN and SenseLife, enabling in-situ and remote detection of organics, isotopic ratios and microstructures. Finally, PlanetS has played a major role in preparing the next generation of observatories, from JWST, VLT and ELT instruments to LIFE and the Habitable Worlds Observatory. Together, these contributions form an integrated framework advancing the search for life beyond Earth.

A mildly inhomogeneous universe with a cosmological constant may look like it contains evolving dark energy. We show that could be the case by modelling the inhomogeneities and their effects in three different ways: as clumped matter surrounded by voids, as back-reaction of small-scale structure on the overall expansion of the Universe, and, finally, as a large-scale curvature inhomogeneity. In all of these cases, the propagation of light is affected, and differs from that in a homogeneous and isotropic universe. The net result is that cosmological observables, such as angular diameter and luminosity distances, become distorted. We find, in all three models, that the inclusion of these effects pushes the distance-redshift relation towards closer agreement with recent data from both supernovae Ia from the Dark Energy Survey, and from baryon acoustic oscillations from the Dark Energy Spectroscopic Instrument. The amount of inhomogeneity in these models might not be enough to explain the entirety of the deviation from a cosmological constant, but is found to be of a similar order of magnitude, hinting that these data may be consistent with a universe dominated by a cosmological constant.

Rotational dynamics of asteroids carry important information about their internal structure, collisional history and material composition. This work investigates whether metallic (M-type) asteroids exhibit systematically higher rotation rates than the broader asteroid population. Using recent Mahlke's taxonomy and a multi-method statistical approach that combines classical hypothesis testing, regression modeling, and resampling techniques, we consistently find evidence that metallic asteroids rotate, on average, faster. The results remain robust across different ways of controlling for asteroid size and sampling biases. While limitations remain due to sample size, heterogeneous data sources, and possible selection effects, the convergence of independent methods strengthens the conclusion that metallic composition is associated with higher rotation rates. This finding supports the hypothesis that metallic bodies possess greater internal cohesion, with implications for the formation and collisional evolution of small bodies in the Solar System.

We present a new comprehensive study of HD81809, a nearby binary system of two solar-like stars showing high-amplitude X-ray emission and a well-defined 8-year solar-like magnetic cycle. By analyzing high-resolution spectroscopy, alongside DR3 Gaia astrometry, and bolometric fluxes, we derive updated fundamental parameters for both components. In particular, we uncover a significant chemical difference: the primary is metal-poor ([Fe/H]$ \simeq - 0.57$), while the secondary shows solar-like metallicity ([Fe/H]$=0.00$). This suggests that the system originated in a mildly metal-poor environment, consistent with the Galactic thick disk population, and that the secondary's surface composition has been altered by a recent accretion event. Using multi-sector TESS photometry, we detected solar-like oscillations in both components, deriving global asteroseismic parameters $\Delta\nu = 43.32 \pm 3.91 \mu$Hz, $\nu_{\rm max} = 708.74^{+3.23}_{-3.74} \mu$Hz for HD81809 A, and $\Delta\nu = 97.75 \pm 4.49~\mu$Hz, $\nu_{\rm max} = 2098.07^{+3.07}_{-2.83} \mu$Hz for HD81809 B. By combining all the observational constraints with stellar evolutionary models computed using CLES and MESA codes, we reconstructed the evolutionary scenario of the system. Our results indicate that HD 81809 is an old system with an age of $\sim 10 \mathrm{Gyr}$, composed of a subgiant primary with mass $\sim 0.87M_{\odot}$ and radius $\sim1.96R_{\odot}$ - likely responsible for the reactivated dynamo cycle - and a main sequence secondary with mass $ M=0.85M_{\odot}$ and radius $R=1.10R_{\odot}$. This system represents a benchmark for studying stellar evolution, magnetic activity, and the physics of old, metal-poor stars in the Galactic thick disk.

We explore the ability of normalizing flow (NF) generative models to reproduce weak-lensing summary statistics when trained on a set of cosmological simulations. Our analysis focuses on how accurately NF models recover the mean, standard deviation, and covariance of key statistics derived from convergence ($\kappa$) maps: The angular power spectrum $C_{\ell}$, probability density function, and Minkowski functionals of weak lensing convergence $\kappa$-maps. We test two scenarios for training: (1) on the data vectors and (2) on the full $\kappa$-maps. In both cases, the NF models reproduce the mean and variance of the target statistics within percent-level accuracy. However, the accuracy of the off-diagonal elements of the covariance matrix is underestimated by up to $\sim25\%$. We study several mitigation strategies and find that data augmentation and training with noisy fields help improve covariance recovery to $\mathcal{O}(10\%)$. Our study demonstrates that while the means and variances of weak lensing statistics can be well modeled by NF, covariances can be significantly underestimated if mitigation strategies are not applied.

The presence of massive O-type stars with surfaces enriched by CNO-cycle products has been known since the early 1980s. For many years, internal rotational mixing was assumed to be the dominant mechanism responsible for this chemical contamination. However, accumulating evidence now suggests that binary interaction -- particularly mass-transfer episodes -- may play an equally important, if not dominant, role. We aim to carry out a large-scale investigation of surface helium (He) abundances in Galactic O-type stars, based on the results from the analysis of high-quality spectroscopic data from the IACOB project. We perform a homogeneous spectroscopic analysis of 318 Galactic O-type stars with the IACOB-BROAD and FASTWIND/IACOB-GBAT tools, deriving rotational velocities, atmospheric parameters, and He abundances. We also account for the influence of binarity, runaway status, and parameter degeneracies (e.g., microturbulence, wind properties, diagnostic lines, and companion contamination) on the abundance determinations. We present homogeneously determined surface He abundances (YHe=N(He)/N(H)) for the so far largest, statistically significant sample of Galactic O-type stars. About 78% of the stars show He abundances consistent with the previously proposed cosmic abundance standard of YHe=0.098$\pm$0.002. The remaining 22% display clear He enrichment (YHe>0.13). We also provide observational evidence indicating that most of these He-enriched stars are likely the products of binary interaction. Our study highlights how large spectroscopic surveys are gradually opening robust observational avenues to identify the products of massive binary interaction. It also emphasizes the need for caution when interpreting the spectroscopic properties of apparently single O-type stars. A significant fraction may in fact be the outcome of binary evolution rather than isolated stellar birth.

Knowledge of the actual density distribution of matter in the local universe is needed for a variety of purposes -- for instance, as a baseline model for ultrahigh energy cosmic ray sources in the continuum limit and for predicting the diffuse Dark Matter annihilation signal. Determining the local mass density and velocity distribution is the aim of the CosmicFlows project. An alternate approach is based on catalogs of galaxies, supplemented with some scheme for filling in for unseen galaxies. Here, we compare the density field proposed by Biteau (2021) with the quasi-linear density field of CosmicFlows2 (Hoffman et al. 2018) and the mean posterior field of CosmicFlows4 (Valade 2026). We find factor-two level differences in some regions and even greater in regions toward the Galactic center zone of avoidance (ZoA) (|l| < 30°, |b| < 20°) as filled by Biteau using "cloning". Within 11 Mpc the density field is well-determined by the Local Volume catalog (Karachentsev et al. 2018) which Biteau directly incorporates; at larger distances, Biteau (2021) should not be used in the ZoA where "galaxies" are entirely fictitious but otherwise is to be preferred over CosmicFlows emphasizing the direction and integrated mass of structures; the radial distribution of mass in Biteau (2021) is less robust due to line-of-sight peculiar velocities. The angular positions of structures in CosmicFlows are sometimes not congruent with evidence in the galaxy catalog.

This paper discusses the broad science case for obtaining milliarcsecond to microarcsecond astronomical imaging resolution in the soft to medium-energy X-ray band (~0.5 to ~8 keV). Astronomy across much of the electromagnetic spectrum has been fundamentally transformed with a rapid increase in ground-based and space-based capabilities to examine celestial objects on small scales that relate directly to their relevant physical processes. X-ray imaging capabilities, however, have fallen far behind observations at longer wavelengths. As such, without decisive advances in X-ray imaging, we will be unable to uncover key phenomena on the smallest astrophysical scales, leaving entire classes of high-energy discoveries beyond our reach. Here we describe several science goals for which high quality X-ray imaging is crucial and the status of some current technologies or mission concepts that would be required for these advances. In particular, we discuss the Accretion Explorer, a mission architecture under current study for a dispersed aperture X-ray interferometer.

This work investigates whether two known Andromeda (M31) satellites, Pisces (LGS 3) and Andromeda XVI, have interacted with M33, M31's most massive satellite. $\Lambda$CDM predictions imply a handful of satellite galaxies around M33, yet few M33 satellites have been found and confirmed despite its high mass. We use proper motions combined with backward orbit integration in a semi-analytic potential to constrain plausible interaction scenarios for Pisces and And XVI. Both dwarfs are currently M31 satellites, defined as being inside its virial radius. However, our results show that, in our fiducial mass models, 42% (And XVI) and 60% (Pisces) of dwarf orbits support that they were previously satellites of M33 (i.e., once inside its virial radius). Both dwarfs had fly-by encounters with M33 at relative velocities greater than M33's escape speed within the past 1-2 Gyr. In over 70% of orbits, Pisces and And XVI also had a close approach with each other post-M33 interaction and share an orbital plane, suggesting possible past group accretion. We explore a range of mass combinations for M31 and M33, finding that this primarily regulates the likelihood that the dwarfs were satellites of M33 in the past, while upholding conclusions of recent flybys about M33. These close interactions provide new evidence for past satellite exchange and/or group infall scenarios between M31 and M33. Such interactions also affect comparisons to observational surveys that define satellites primarily by their distance relative to host galaxies.

We present a NOEMA survey of CO(3-2), CO(4-3), and [C I]($^3$P$_1$-$^3$P$_0$) in eight faint (average $S_{\rm 850 \mu m} = 2.3$ mJy) dusty star-forming galaxies (DSFGs) at $z = 1.2-2.5$. We used a NIR flux-color cut to match faint SCUBA-2 sources to red stellar counterparts with existing spectroscopic redshifts, allowing us to target CO lines at known frequencies. We obtained seven new CO detections and a serendipitous [C I] detection in an off-axis source, and measured molecular gas masses of $M_{\rm mol} = (6-22)\times10^{10}~(\alpha_{\rm CO}/3.6)~{\rm M}_\odot$ from these lines. We performed UV-to-mm SED fits to measure the SFRs and stellar masses of our sample, and compared these with two other $z = 1-3$ CO samples from the literature. The CO detections have constant depletion times of $t_{\rm dep} \sim 500$ Myr, with no evidence for correlation between $t_{\rm dep}$ and redshift or main-sequence offset. We find that low-mass ($M_\star \lesssim 10^{11}~{\rm M}_\odot$), starbursting galaxies have gas fractions and depletion times twice as high as predicted by molecular gas scaling relations, which may indicate that $M_{\rm mol}$ is systematically over-estimated in this population, possibly due to decreased $\alpha_{\rm CO}$ or increased CO excitation compared to the well-studied massive and/or main-sequence DSFG population.

Understanding the variability of Sagittarius A* (Sgr A*) requires coordinated, multi-wavelength observations that span the electromagnetic spectrum. In this work, we focus on data from four key observatories: Chandra in the X-ray (2-8 keV), GRAVITY on the Very Large Telescope in the near-infrared (2.2 microns), Spitzer in the infrared (4.5 microns), and ALMA in the submillimeter (340 GHz). These multi-band observations are essential for probing the physics of accretion and emission near the black hole's event horizon, yet they suffer from irregular sampling, band-dependent noise, and substantial data gaps. These limitations complicate efforts to robustly identify flares and measure cross-band time lags, key diagnostics of the physical processes driving variability. To address this challenge, we introduce a diffusion-based generative model, for interpolating sparse, multivariate astrophysical time series. This represents the first application of score-based diffusion models to astronomical time series. We also present the first transformer-based model for light curve reconstruction that includes calibrated uncertainty estimates. The models are trained on simulated light curves constructed to match the statistical and observational characteristics of real Sgr A* data. These simulations capture correlated multi-band variability, realistic observation cadences, and wavelength-specific noise. We compare our models against a multi-output Gaussian Process. The diffusion model achieves superior accuracy and competitive calibration across both simulated and real datasets, demonstrating the promise of diffusion models for high-fidelity, uncertainty-aware reconstruction of multi-wavelength variability in Sgr A*.

JWST observations have revealed that massive galaxies formed and evolved far faster than predicted by galaxy formation models, with many having already assembled a large mass in stars $\sim12$ billion years ago [1-7]. However, masses of distant galaxies are highly uncertain, as they assume a distribution of stellar birth masses (the initial mass function [IMF]) similar to that in the Milky Way (MW). Specifically, the contribution from low-mass stars, which make up the bulk of stellar mass, is not directly observed, but inferred based on an extrapolation of the MW IMF. Here, we provide the first robust measurements of the IMF beyond the local Universe. Using ultra-deep spectra of nine massive, quiescent galaxies at $z\sim0.7$ from the ambitious JWST-IMFERNO program, extended to bluer wavelengths with deep spectra from LEGA-C [8], we find that these distant galaxies have excess low-mass stars. In other words, they have more bottom-heavy IMFs than the MW. For the oldest two galaxies, which are direct descendants of JWST's "impossibly early" galaxies, the bottom-heavy IMFs increase their stellar masses by a factor of $3-4$. These galaxies thus amplify the tension with galaxy formation models.

The ACT data have severely constrained the single scalar field models. Known models of inflation, like the Starobinsky model, the Higgs model and the $a$-attractors are at least $2\sigma$ off the ACT data. In this work we aim to provide a top-to-bottom approach in single scalar field inflationary cosmology compatible with the ACT data. Specifically, inspired by the fact that the Starobinsky model, the Higgs model and the $a$-attractors, all being plateau potentials, result to the same attractor relation between the spectral index of scalar perturbations and the tensor-to-scalar ratio, which is of the form $n_s(r)=1-\alpha r^{1/2}$, in this work we seek for attractors of the form $n_s(r)=f(r)$ that may lead to ACT-compatible inflation. Specifically, we fix the function $f(r)$ to have a specific desirable form and then solve the differential equation $n_s(r)=f(r)$ to find the potential which results to the relation $n_s(r)=f(r)$. We discovered analytically three classes of potentials which are variants of the general form $n_s(r)=\gamma \pm \beta r \pm r^{1/2}$ and all these models are found to be compatible with the ACT data.

It is known that if the standard slow-roll inflation is followed by a power-law inflationary regime, then the trans-Planckian modes may be safely be contained in the Hubble horizon and never exit it during inflation. In this work we investigate how to realize a smooth transition between a slow-roll and a power-law inflationary regime in the context of single scalar field inflation. As we show it is possible to realize such a smooth transition by generalizing the kinetic energy of single scalar field in the form $\dot{\phi}^2=\beta(\phi)V(\phi)$, where $\beta(\phi)$ is some appropriate function of the scalar field. Using two distinct approaches we show that it is possible to realize a smooth transition from a slow-roll to a power-law inflationary regime, and the two approaches produce identical results regarding the slow-roll regime. Also we show that the slow-roll regime is quite short, about $N\sim 30$ $e$-foldings, with the flatness and horizon problems being solved with the synergistic effect of the two inflationary patches. The slow-roll era is found to be compatible with the Atacama Cosmology Telescope data.

In this work we use the recently introduced concept of self-interacting dark matter with scale-dependent equation of state, and we provide an analytic model of dark matter that can produce viable rotation curves even for low-surface-brightness galaxies, irregular galaxies, low-luminosity spirals and dwarf galaxies, all known to challenge the cold dark matter description. The radius dependent effective equation of state of the self-interacting dark matter model we shall introduce is assumed to be an isothermal equation of state of the form $P(r)=K(r)\left(\frac{\rho(r)}{\rho_{\star}}\right)$, where the energy density will have the form $\rho(r)=\frac{\rho_0}{\left( 1+\frac{r^2}{\alpha^2}\right)^{5/2}}$, while the entropy function $K(r)$ is $K(r)=\frac{K_0}{\left( 1+\frac{r^2}{\alpha^2}\right)^{1/2}}$. The resulting model is confronted in detail with the SPARC galaxy data and 175 galaxies are used and tested. It proves that the analytic model can successfully produce the rotation curves of 116 galaxies, most of which are small mass spirals, irregular galaxies, low-surface-brightness and low-luminosity spirals and dwarf galaxies. On the other hand, 59 galaxies cannot be successfully described by our analytic model. We tested statistically the correlation between the parameter $K_0$ of the entropy function corresponding to the viable galaxies, and the flat rotation velocity $V_{flat}$ and the maximum rotation velocity $V_{max}$ of the galaxies from the SPARC data. We also examined the baryon mass $M_b$-$K_0$ relation and the luminosity $L$-$K_0$ relation. We have been able to produce the baryonic Tully-Fisher relation for the viable galaxies, directly from the correlation $K_0$-$M_b$ and $K_0$-$V_{flat}$, with the resulting relation being $M_b\sim V_{flat}^{4.026 \pm 0.371}$, however we failed to produce the canonical Tully-Fisher relation.

Building upon our recently established correspondence between quantum cosmology and the hydrogen atom [1], we investigate the specific sector of a negative cosmological constant ($\Lambda < 0$) in a flat FLRW universe with dust. While the positive $\Lambda$ sector [1] yields a continuous spectrum and a single bounce, we show here that the negative $\Lambda$ sector leads to a discrete spectrum of energy eigenvalues, effectively quantizing the cosmological constant. Within this dual description, the operator-ordering ambiguity parameter appears as the azimuthal quantum number of the hydrogen atom. A skewed Bohr correspondence emerges for the bound states, matching classical evolution at large volumes but deviating near the bounce. By constructing wave packets from these bound states, we demonstrate that the classical Big Bang and Big Crunch singularities are resolved, and the universe oscillates between quantum bounces and classical turnaround points. The expectation values of the observables indicate a cyclic universe -- with vanishing Hubble parameter at turnarounds -- undergoing quantum bounces. This exactly solvable model offers a tractable setting to explore quantum gravitational effects in cosmology. We analyze the properties of this cyclic universe, contrasting its bound-state dynamics with the scattering states of the de Sitter case.

In this paper, we describe the procedure implemented in the Multi-Band Template Analysis (MBTA) search pipeline to produce online posterior distributions of compact binary coalescence (CBC) gravitational-wave parameters. This procedure relies on an SNR optimizer technique, which consists of filtering dense local template banks. We present how these banks are constructed using information from the initial detection and detail how the results of the filtering are used to estimate source parameters and provide posterior distributions. We demonstrate the performance of our procedure on simulations and compare our source parameter estimates with the results from the first part of the fourth observing run (O4a) recently released by the LIGO-Virgo-KAGRA (LVK) collaboration.

This paper presents a comprehensive stability analysis of the black hole solution within Modified General Relativity (MGR), a theory proposing a unified geometric description of dark matter (DM) and dark energy (DE). A rigorous gauge-invariant formalism is employed to analyze gravitational perturbations of the extended Schwarzschild metric. The central finding is a critical pathology within the polar perturbation sector, where metric fluctuations couple to the theory's fundamental line element field. This coupling is governed by a factor that, while well-behaved at the horizon, diverges powerfully in the far-field limit as a direct consequence of the theory's non-asymptotically flat nature. This indicates a strong infrared instability that overwhelms perturbations at large distances. In stark contrast, the axial perturbation sector is found to be completely stable. This dichotomy proves that the instability is not inherent to the background metric but is specifically generated by the novel coupling mechanism encoding MGR's unified dark sectors. The results reveal a fundamental strong-coupling problem within the MGR framework, challenging its physical viability as an alternative to Einstein's General Relativity (EGR).

We report on two 3He-rich solar energetic particle (SEP) events observed by Solar Orbiter (SO) and Parker Solar Probe (PSP) during the April 1 - 4, 2024 conjunction when both spacecraft are within 0.3 AU near their respective perihelion passage. The two 3He-rich SEP events, originating from active region (AR) 13615, exhibit two key anomalies: (1) sunward streaming SEPs and (2) SEP travel path lengths exceeding 2 - 8 times the nominal Parker spiral expectations. Remote observations suggest these SEPs have been redirected by a slow coronal mass ejection (CME) that also originated from AR 13615 two days prior on March 30, 2024 at 21:04 UT. Using the near-Sun CME speed and width measurements, we estimate its size and location at the onset time of the first 3He-rich SEP event. Based on our estimates, SEPs propagating around the ICME front have travelled between 0.76 - 0.95 AU when they arrive at SO, increasing to 0.94 - 1.1 AU at PSP, consistent with our observed SEP arrival times. These findings constitute the first multi-spacecraft observation of sunward streaming 3He-rich SEPs. We discuss the implications of this phenomenon on 3He-rich seed material and the rare widespread 3He-rich SEP events (see Section 5.4).

Axion, the goldstone boson arising from the spontaneous breaking of a global $U(1)$ Peccei-Quinn symmetry, provides a dynamical solution to the strong CP problem and is an excellent dark matter candidate. Various experiments are designed to search for the axion, however no confirmative signal has been observed. On the other hand, there are also hypothetical heavy particles in axion models, such as the heavy scalar $s$, which is the CP-even component of the complex scalar that carries $U(1)_{PQ}$ charge, and the vector-like heavy quark (VLQ) in the Kim-Shifman-Vainshtein-Zakharov~(KSVZ) axion model. Studying signals induced by them are helpful for axion searches. In this paper, we calculate the graviton bremsstrahlung energy spectrum arising from the decay of the heavy scalar or VLQ in the KSVZ model. The result shows that these heavy particles can emit ultrahigh-frequency gravitational waves (GWs), with the peak frequency depending on the model's parameter inputs. In addition, the graviton spectrum is distinguished from the thermal GW background at high frequencies if there is an early matter-dominated era induced by these heavy particles. Future measurements of ultrahigh-frequency GWs may provide indirect evidence for the KSVZ axion.