Papers for Thursday, Aug 21 2025

Aqueous metabolites in terrestrial subsurface environments provide critical analog frameworks for assessing the habitability of Martian subsurface ice. On Earth, they play critical roles in sustaining microbial life within soils, permafrost, and groundwater environments and their availability shape microbial community compositions, activity, and adaptability to changes in environmental conditions, enabling communities to persist over millennial timescales. The counterpart to aqueous-soluble organics is the insoluble organic matter pool that makes up the largest portion of organic matter in natural samples and includes most types of organic signatures indicative of biological processes. Employing a range of sample preparation, molecular separation, detection, and imaging techniques enables the characterization of both labile (i.e., soluble and reactive) and recalcitrant (i.e., insoluble, non-reactive; include macromolecules) organic pools. Multiple orthogonal analytical modalities strengthen interpretations of signatures that we associate with biology as we know it and don't know it, by constraining possible abiotic sources, validating measurements across distinct techniques, and ensuring flexibility to interrogate diverse organic chemistries encountered in Martian subsurface environments. This holistic triage approach aligns with the priorities articulated in the Mars Exploration Program Analysis Group's Search for Life -Science Analysis Group (SFL-SAG) Charter for a medium-class Mars mission focused on extant life detection.

This paper introduces a high resolution, machine learning-ready heliophysics dataset derived from NASA's Solar Dynamics Observatory (SDO), specifically designed to advance machine learning (ML) applications in solar physics and space weather forecasting. The dataset includes processed imagery from the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI), spanning a solar cycle from May 2010 to July 2024. To ensure suitability for ML tasks, the data has been preprocessed, including correction of spacecraft roll angles, orbital adjustments, exposure normalization, and degradation compensation. We also provide auxiliary application benchmark datasets complementing the core SDO dataset. These provide benchmark applications for central heliophysics and space weather tasks such as active region segmentation, active region emergence forecasting, coronal field extrapolation, solar flare prediction, solar EUV spectra prediction, and solar wind speed estimation. By establishing a unified, standardized data collection, this dataset aims to facilitate benchmarking, enhance reproducibility, and accelerate the development of AI-driven models for critical space weather prediction tasks, bridging gaps between solar physics, machine learning, and operational forecasting.

Heliophysics is central to understanding and forecasting space weather events and solar activity. Despite decades of high-resolution observations from the Solar Dynamics Observatory (SDO), most models remain task-specific and constrained by scarce labeled data, limiting their capacity to generalize across solar phenomena. We introduce Surya, a 366M parameter foundation model for heliophysics designed to learn general-purpose solar representations from multi-instrument SDO observations, including eight Atmospheric Imaging Assembly (AIA) channels and five Helioseismic and Magnetic Imager (HMI) products. Surya employs a spatiotemporal transformer architecture with spectral gating and long--short range attention, pretrained on high-resolution solar image forecasting tasks and further optimized through autoregressive rollout tuning. Zero-shot evaluations demonstrate its ability to forecast solar dynamics and flare events, while downstream fine-tuning with parameter-efficient Low-Rank Adaptation (LoRA) shows strong performance on solar wind forecasting, active region segmentation, solar flare forecasting, and EUV spectra. Surya is the first foundation model in heliophysics that uses time advancement as a pretext task on full-resolution SDO data. Its novel architecture and performance suggest that the model is able to learn the underlying physics behind solar evolution.

Energy awareness and efficiency policies are gaining more attention, over pure performance (time-to-solution) Key Performance Indicators (KPIs) when comparing the possibilities offered by accelerated systems. But in a field such as numerical astrophysics, which is struggling with code refactorings for GPUs, viable porting paths have to be shown before first. After summarizing the status and recurring problems of astrophysical code accelerations, we highlight how the field would benefit from portable, vendor-agnostic GPU portings. We then employ the DPEcho SYCL benchmark to compare raw performance and energy efficiency for heterogeneous hardware on a realistic application, with the goal of helping computational astrophysicists and HPC providers make informed decisions on the most suitable hardware. Aside from GPUs showing higher efficiency, we argue on the more informative nature of energy-aware KPIs, in that they convey the specific device performance in a data-driven way. We also present a convenient, flexible and cross-platform energy-measuring pipeline. Finally, we contextualize our results through measures with different compilers, presenting device (at the cores) versus node (at the plug) energy and comparing DPEcho with the High- Performance Linpack (HPL) benchmark.

We report the physical origin of transient off-centre convective zones (oCZs) that arise in mass accreting stellar models. Using detailed MESA simulations of binary evolution, we find that these oCZs are not numerical artefacts but emerge due to a local increase in density near the retreating edge of the convective core. The density enhancement raises the local opacity, which amplifies the radiative temperature gradient $\nabla_{\rm rad}$. If this gradient surpasses the Ledoux threshold $\nabla_{\rm L}$, defined by both thermal and compositional stratification, the region becomes convectively unstable. The resulting oCZs are detached from the convective core and transient: mixing within the oCZ erases the local gradient in mean molecular weight, leaving a sharp $\nabla_{\mu}$ discontinuity at the boundary, stabilizing the adjacent layers. This mechanism naturally explains the presence and evolution of oCZs, as previously reported in massive interacting stars.

The search for habitable conditions beyond Earth is a top priority in astrophysics. The discovery of habitable exoplanets beyond our solar system will require a suite of instruments providing long-term monitoring for detection (e.g. with space and ground-based radial velocity observations), spectroscopic characterization of atmospheric and surface properties, and eventually deep chronograph-aided observations from e.g. JWST, Roman Space Telescope, and the Habitable Worlds Observatory (HWO). Detection of exoplanet magnetospheres is necessary to identify the most promising targets for follow-up characterization of biosignatures with these assets, and to provide an ensemble of objects for studies of magnetospheric conditions and atmospheric composition. Only observations of low-frequency radio emission will distinguish exoplanet magnetospheres (Hallinan et al. 2021). In this white paper, we present the two lunar radio array concepts under development that would be suitable to detect these exoplanet radio emissions. In addition, we also discuss the human exploration needed prior to construction of such lunar radio arrays while highlighting preferred candidate sites (Krolikowski & Elvis 2024) for the radio telescope.

Context. Many critical physical processes, such as Roche lobe overflow, strain modern simulation methods due to their durations and multidimensionality. Aims. We employ a novel method of time-domain multidimensional simulations to provide the first grid-based time domain 3D model of Roche lobe overflow using VH-1. Methods. Using a piecewise approach which alternates between high-resolution 3D dynamic modeling and computationally fast evolutionary modeling, we present and test a method capable of self-scaling variable time resolution at greatly reduced computational cost. Results. We find mass transfer in the test high mass x-ray binary M33 X-7 to be unstable and fully conservative in both mass and angular momentum transport onto the accretion disk beyond f >~ 1.01. This phase begins on thermal timescales and accelerates to span < 100 yrs beyond f >= 1.1, while the non-conservative stable phase of f <~ 1.01 occurs on roughly nuclear timescales. Conclusions. We identify a critical point f ~ 1.01 which terminates stable overflow, which may correspond to the point Mdot_L1 ~ Mdot_wind or Mdot_L1 ~ 10^-6 M_solar/yr in the general case.

The solar disk is a continuous source of GeV--TeV gamma rays. The emission is thought to originate from hadronic Galactic cosmic rays (GCRs) interacting with the gas in the photosphere and uppermost convection zone after being reflected by solar magnetic fields. Despite this general understanding, existing theoretical models have yet to match observational data. At the photosphere and the uppermost convection zone, granular convection drives a multi-scale magnetic field, forming a larger-scale filamentary structure while also generating turbulence-scale Alfvén wave turbulence. Here, we demonstrate that the larger-scale filamentary field shapes the overall gamma-ray emission spectrum, and the Alfvén wave turbulence is critical for further suppressing the gamma-ray emission spectrum below $\sim 100$~GeV. For a standard Alfvén wave turbulence level, our model's predicted spectrum slope from 1~GeV to 1~TeV is in excellent agreement with observations from Fermi-LAT and HAWC, an important achievement. The predicted absolute flux is a factor of 2--5 lower than the observed data; we outline future directions to resolve this discrepancy. The key contribution of our work is providing a new theoretical framework for using solar disk gamma-ray observations to probe hadronic GCR transport in the lower solar atmosphere.

The James Webb Space Telescope (JWST) has discovered a new population of objects, the Little Red Dots (LRDs), characterized by V-shaped spectra indicative of strong breaks around the Balmer limit and compact morphology that gave them their name. A popular explanation is that they are a sub-population of active galactic nuclei/supermassive black holes (AGN/SMBHs) predominantly found in the high-redshift Universe ($z\gtrsim3$). Similarly, direct collapse black holes (DCBHs), theorized to form from collapsing massive, extremely metal-poor gas clouds, have been invoked to explain high-redshift quasars, the most massive AGN sub-population. Here, we employ the semi-analytical code A-SLOTH to produce a population of DCBHs and compare them against observed LRD demographics and properties. Specifically, we compare the DCBH-seeded SMBH population against the standard stellar-remnant seeds and find that DCBH models agree better with observed LRD population statistics and host halo properties. Furthermore, for the most extreme and earliest LRD detections, interpreted to be systems with an AGN but little stellar component, DCBHs are able to reproduce the observed spectral shape and properties under multiple scenarios - high dust attenuation or AGN surrounded by dense gas - that have been proposed to explain the unique shape of LRD spectra. Even when super-Eddington accretion, invoked previously to explain the nature of LRDs, is enforced on stellar remnant seeds, the spectral characteristics of extreme LRDs cannot be reproduced. We emphasize the importance of gas-metallicity observations as an additional dimension besides the widely used SMBH-stellar mass ratios to further constrain the progenitors of LRDs.

AXIS, a Probe mission concept now in a Phase A study, will provide transformative studies of high-energy astrophysical phenomena thanks to its high-resolution X-ray spectral imaging. These capabilities are enabled by improvements to the mirror design that greatly increase the X-ray throughput per unit mass; and to the detector system, which operates more than an order of magnitude faster than heritage instruments while maintaining excellent spectral performance. We present updates to the design of the AXIS High-Speed Camera, a collaborative effort by MIT, Stanford University, the Pennsylvania State University, and the Southwest Research Institute. The camera employs large-format MIT Lincoln Laboratory CCDs that feature multiple high-speed, low-noise output amplifiers and an advanced single-layer polysilicon gate structure for fast, low-power clock transfers. A first lot of prototype CCID100 CCDs has completed fabrication and will soon begin X-ray performance testing. The CCDs are paired with high-speed, low-noise ASIC readout chips designed by Stanford to provide better performance than conventional discrete solutions at a fraction of the power consumption and footprint. Complementary Front-End Electronics employ state-of-the-art digital video waveform capture and advanced signal processing to further deliver low noise at high speed. The Back-End Electronics provide high-speed identification of candidate X-ray events and transient monitoring that relays fast alerts of changing sources to the community. We highlight updates to our parallel X-ray performance test facilities at MIT and Stanford, and review the current performance of the CCD and ASIC technology from testing of prototype devices. These measurements achieve excellent spectral response at the required readout rate, demonstrating that we will meet mission requirements and enable AXIS to achieve world-class science.

Gravitational-wave measurements of the binary black hole population provide insights into the evolution of merging binaries. We explore potential correlation between mass and mass ratio with phenomenological population models where the minimum mass of the smaller (secondary) black hole can change with the mass of the bigger (primary) black hole. We use binary black hole signals from the third Gravitational-Wave Transient Catalog with and without the relatively extreme mass-ratio GW190814. When excluding GW190814, models with a variable minimum mass are disfavoured compared to one with a constant minimum mass, with log Bayes factors of -2.49 to -0.98, indicating that the biggest black holes can merge with the smallest. When including GW190814, a parabola model that allows the minimum mass to decrease with increasing primary mass is favoured over a constant minimum-mass model with a log Bayes factor of 4.44. When allowing the minimum mass to decrease, the overall population distributions remain similar whether or not GW190814 is included. This shows that with added model flexibility, we can reconcile potential outlier observations within our population. These investigations motivate further explorations of correlations between mass ratio and component masses in order to understand how evolutionary processes may leave an imprint on these distributions.

Envelope stripping, whether through single-star wind mass loss or binary mass transfer, is a key evolutionary pathway for the formation of classical Wolf-Rayet stars and lower-mass stripped helium (He) stars. However, to study the evolution of these objects into black holes, neutron stars, and stripped-envelope supernovae, we need appropriate input models for the core-He burning phase without relying on the uncertain evolution into this evolved phase. Reliable mass-luminosity relations (MLRs) for He stars are needed for stellar wind and evolution studies, but the MLRs currently in literature are either for fully-stripped or chemically homogeneous stars, neither of which reflect the important and recently also observationally confirmed stage of partial stripping. We alleviate this drawback by computing sets of MESA synthetic structure models with partially-stripped chemical profiles, consisting of a pure-He core and a hydrogen (H)-depleted envelope with an H/He chemical gradient left behind from the receding convective core during the main sequence. As the H slope increases from 0 (full chemical homogeneity) to $\infty$ (pure-He stars) in our synthetic models, we find the luminosity to initially increase before eventually decreasing. The maximum luminosity for a given mass is reached for an intermediate H-profile slope corresponding to a partially-stripped structure, exceeding even the values documented for pure-He stars, primarily due to the H shell disproportionately dominating the total luminosity budget. We also provide convenient mass-luminosity fit relations to predict the minimum, maximum, and pure-He luminosities for a given mass -- and vice versa -- while accounting for structures achievable through partial stripping. We also explore the impact of the higher luminosity on the wind properties of partially-stripped configurations using hydrodynamically consistent atmosphere models.

There are millions of undetected black holes wandering through our galaxy. Observatories like {\it Chandra}, LIGO, and more recently, {\it Gaia}, have provided valuable insights into the configurations of these elusive objects when residing in binary systems. Motivated by these advances, we study, for the first time, the enhanced accretion of metals from the interstellar medium (ISM) onto low-mass companions in binary systems with highly unequal mass ratios, utilizing a series of hydrodynamical simulations. Our study demonstrates that a stellar companion's metal accretion history from the ISM alone, from its formation to the present, can significantly influence its surface abundances, especially when enhanced by a massive black hole companion. However, this effect is likely only measurable in stars that are still in the main sequence. Once a stellar companion evolves off the main sequence, similar to what has been observed with the {\it Gaia} BH3 companion, the initial dredge-up process are likely to erase any excess surface abundance resulting from the metals that were accreted. As we discover more unequal mass ratio binary systems, it is crucial to understand how the observed metallicity of sun-like companions may differ from their birth metallicity, especially if they are not yet evolved.

Recent JWST surveys of high-redshift galaxies have found surprisingly large black holes, with many being measured to be $\sim100$ times more massive than local galaxies with the same stellar mass. Here, we find that a population of these black holes would have dramatic implications for our understanding of their growth across cosmic time. We first show that the global black hole mass density at $z \sim 5$ would be comparable to local values. This would not occur if these black holes occupy a small fraction of galaxies, though it would be expected if these black holes radiate at high efficiencies (requiring that the central engines of AGN spin rapidly). We then show that the individual detected $z \sim 5$ black holes would remain overmassive compared to the local relation if they grow according to the average rates of state-of-the-art models. These systems must instead grow at least an order of magnitude more slowly than expected if they are to fall within the observed scatter of the local black hole mass-stellar mass relation. Such slow growth is surprising in comparison to other estimates of the radiative efficiency of AGN, especially because growth must be rapid at $z > 5$ in order to build up such massive black holes quickly. Finally, we highlight the challenges that overmassive black holes have on our understanding of the impact of quasar feedback on galaxies.

Advanced wavefront sensors (WFS) are essential for enabling new science cases for telescopes that utilize adaptive optics (AO) systems. While complex field WFS -- those that estimate the electric field phase and amplitude through interference or diffraction effects -- can achieve extraordinary sensitivity compared to existing devices, they typically reconstruct the wrapped phase of the measured wavefront, which must then be unwrapped for correction by continuous-surface deformable mirrors (DM). Another requirement is that the phase function must be unwrapped within 1 millisecond or faster for real-time AO operations. Using simulations of atmospheric turbulence that follow a Kolmogorov spectrum, we study four prevalent and mature phase unwrapping methods: Fast2D, Zernike Gradient (Zernike), Discrete Fourier Transform (DFT), and Least Squares Principle Value (LSPV). In this paper, we examine the strengths and limitations of each method. In particular, we consider performance with and without a binary circular aperture boundary that defines the edge of monolithic telescopes.

Polarimetric properties of blazars allow us to put constraints on the acceleration mechanisms that fuel their powerful jets. By studying the multiwavelength polarimetric behaviour of high synchrotron peaked (HSP) and low synchrotron peaked (LSP) blazars, we aim to explore differences in their emission mechanisms and magnetic field structure in the acceleration region. In this study, we take advantage of several X-ray polarisation observations of HSP by the IXPE, including four new observations of Mrk 501, and optical polarisation observations of LSP from RoboPol and many others. We find that the polarisation degree (PD) distribution of HSP in X-rays is systematically higher than in optical and mm-radio wavelengths, as reported in previous IXPE publications. The distribution of the X-ray electric vector position angles (PA) is centered around the jet axis with most of the observations consistent with zero difference within uncertainties. In fact, the distribution of the offset of the PA from the jet axis is consistent between the LSP and HSP populations (with PA measured in optical for the first, X-ray for the latter), suggesting a common magnetic field structure close to the acceleration region, in strong support of the emerging energy stratified picture of particle acceleration followed by energy loss in blazar jets.

The resonant scattering nature of Ly$\alpha$ photons interacting with neutral hydrogen makes Ly$\alpha$-emitting galaxies (LAEs) robust tracers of the intergalactic neutral hydrogen fraction, and thus sensitive probes of cosmic reionization. We present an extensive study of the Ly$\alpha$ evolution from galaxies at 4.5 $\leq$ z $\leq$ 11 in the UDS field, observed as part of the CAPERS survey, and complemented with spectra from the DAWN JWST Archive. The combined sample includes 651 spectroscopically confirmed Ly$\alpha$-break galaxies, among which we find 73 S/N>3 LAEs in JWST-NIRSpec PRISM spectra. We trace the redshift evolution of the Ly$\alpha$ emitter fraction with EW$_0$ >25 A (X$_{\mathrm{Ly\alpha}}$) between z = 5 and z = 9, presenting the first such analysis in the UDS field. At z = 5 and 6, the UDS results agree with the average JWST X$_{\mathrm{Ly\alpha}}$ values from multiple fields. However, JWST measurements are consistently lower than ground-based results. To investigate this, we compare JWST observations to a population of star-forming galaxies at z$\sim$6 observed with VLT-FORS2. We find that a Ly$\alpha$ slit-loss of 35 $\pm$ 10% in JWST spectra accounts for the offset, as the resonant Ly$\alpha$ emission is more spatially extended than the stellar continuum. From z = 6 to 7, the UDS field shows a significant drop in Ly$\alpha$ visibility, from which we infer a neutral hydrogen fraction of X$_{\mathrm{HI}}$ = 0.7--0.9. Finally, we identify two robust ionized bubbles at z = 7.29 and 7.77, with radii of $R_{\mathrm{ion}}$ = 0.6 and 0.5 physical Mpc and photometric overdensities of N/$\langle$N$\rangle$ = 3 and 4, based on candidate counts down to the photometric completeness limit. Compared to the large ionized region at z$\sim$7 in the EGS field, these results indicate significant field-to-field variation, supporting a patchy, inhomogeneous reionization process.

The first generation of Single electron Sensitive Read Out (SiSeRO) amplifiers, employed as on-chip charge detectors for charge-coupled devices (CCDs) have demonstrated excellent noise and spectral performance: a responsivity of around 800 pA per electron, an equivalent noise charge (ENC) of 3.2 electrons root mean square (RMS), and a full width half maximum (FWHM) energy resolution of 130 eV at 5.9 keV for a readout speed of 625 Kpixel/s. Repetitive Non Destructive Readout (RNDR) has also been demonstrated with these devices, achieving an improved ENC performance of 0.36 electrons RMS after 200 RNDR cycles. In order to mature this technology further, Stanford University, in collaboration with MIT Kavli Institute and MIT Lincoln Laboratory, are developing new SiSeRO detectors with improved geometries that should enable greater responsivity and improved noise performance. These include CCD devices employing arrays of SiSeRO amplifiers to optimize high speed, low noise RNDR readout and a proof-of-concept SiSeRO active pixel sensor (APS). To read out these devices, our team has developed a compact, 8-channel, fast, low noise, low power application specific integrated circuit (ASIC) denoted the Multi-Channel Readout Chip (MCRC) that includes an experimental drain current readout mode intended for SiSeRO devices. In this paper, we present results from the first tests of SiSeRO CCD devices operating with MCRC readout, and our designs for next generation SiSeRO devices.

Future strategic X-ray missions, such as the Advanced X-ray Imaging Satellite (AXIS) and those targeted by the Great Observatories Maturation Program (GOMaP), require fast, low-noise X-ray imaging spectrometers. To achieve the speed and noise capabilities required by such programs, the X-ray Astronomy and Observational Cosmology (XOC) Group at Stanford, in collaboration with the MIT Kavli Institute (MKI) and MIT Lincoln Laboratory (MIT-LL), is developing readout systems that leverage the high speed, low noise, and low power consumption of application-specific integrated circuit (ASIC) devices. Here, we report the energy resolution and noise performance achieved using MIT-LL AXIS prototype charge-coupled device (CCD) detectors in conjunction with Stanford-developed Multi-Channel Readout Chip (MCRC) ASICs. Additionally, we present a new sampling method for simultaneous optimization of the output gate (OG), reset gate (RG), and reset drain (RD) biases which, in combination with new integrated fast summing well (SW) and RG clock operation modes, enables the data rates required of future X-ray telescopes.

The Advanced X-ray Imaging Satellite (AXIS), an astrophysics NASA probe mission currently in phase A, will provide high-throughput, high-spatial resolution X-ray imaging in the 0.3 to 10 keV band. We report on the notional ground calibration plan for the High Speed Camera on AXIS, which is being developed at the MIT Kavli Institute for Astrophysics and Space Research using state-of-the-art CCDs provided by MIT Lincoln Laboratory in combination with an integrated, high-speed ASIC readout chip from Stanford University. AXIS camera ground calibration draws on previous experience with X-ray CCD focal plans, in particular Chandra/ACIS and Suzaku/XIS, utilizing mono-energetic X-ray line sources to measure spectral resolution and quantum efficiency. Relative quantum efficiency of the CCDs will be measured against an sCMOS device, with known absolute calibration from synchrotron measurements. We walk through the envisioned CCD calibration pipeline and we discuss the observatory-level science and calibration requirements and how they inform the camera calibration.

We report two warm Earth-sized exoplanets orbiting the close binary TOI-2267 (M5+M6, separation ~8 au). Data from TESS and ground-based facilities confirm the planets, but we cannot determine which star they orbit. The planets have radii of 1.00+/-0.11 R_Earth (TOI-2267 b, P=2.28 d) and 1.14+/-0.13 R_Earth (TOI-2267 c, P=3.49 d) if around TOI-2267A, or 1.22+/-0.29 R_Earth and 1.36+/-0.33 R_Earth if around TOI-2267B. TESS also shows a candidate signal (TOI-2267.02, P=2.03 d, 0.95+/-0.12 or 1.13+/-0.30 R_Earth). Dynamical analysis shows all three cannot orbit one star; the most stable configuration has planets b and c (near a 3:2 resonance) orbiting one star and the candidate the other. This scenario would make TOI-2267 the most compact binary system known to host planets, with both components harbouring transiting worlds, offering a unique benchmark for studying planet formation and evolution in compact binary.

The Advanced X-ray Imaging Satellite (AXIS) is one of two candidate mission concepts selected for Phase-A study for the new NASA Astrophysics Probe Explorer (APEX) mission class, with a planned launch in 2032. The X-ray camera for AXIS is under joint development by the X-ray Astronomy and Observational Cosmology (XOC) Group at Stanford, the MIT Kavli Institute (MKI), and MIT Lincoln Laboratory (MIT-LL). To accelerate development efforts and meet the AXIS mission requirements, XOC has developed a twin beamline testing system, capable of providing the necessary performance, flexibility, and robustness. We present design details, simulations, and performance results for the newer of the two beamlines, constructed and optimized to test and characterize the first full-size MIT-LL AXIS prototype detectors, operating with the Stanford-developed Multi-Channel Readout Chip (MCRC) integrated readout electronics system. The XOC X-ray beamline design is forward-looking and flexible, with a modular structure adaptable to a wide range of detector technologies identified by the Great Observatories Maturation Program (GOMAP) that span the X-ray to near-infrared wavelengths.

The blazar AO 0235+164 is a key source for studying the interplay between multi-wavelength variability in its light curves and changes in the position angles and apparent velocities of its parsec-scale jet components. In this work, we analyse public interferometric radio maps of AO 0235+164 at 15 and 43 GHz, using the Cross Entropy global optimisation technique to determine the structural parameters of its jet components. We identified 36 kinematically distinct jet components across all sky quadrants, indicating a highly relativistic parsec-scale jet with a minimum Lorentz factor of 34 +/- 7 and a maximum viewing angle of 37 +/- 8 degree. The temporal evolution of these jet components was modelled as a relativistic jet under a constant precession rate. The optimal clockwise precession model has a precession period of 8.4 +\- 0.2 years, consistent with the 8.13-year periodicity previously detected in optical light curves, besides providing a time-variable Doppler boosting factor correlated with the most intense flares at gamma-ray energies. For the counter-clockwise precession, a period of 6.0 +\- 0.1 years is found, compatible with the 5-6 year periodicities detected at radio and optical wavelengths. It is plausible that a supermassive black hole binary system in the nucleus of AO 0235+164 drives the parsec-scale jet precession and induces nodding motions consistent with short-term continuum periodicities. Nonetheless, alternative scenarios (e.g., intrinsic curved jet, warped accretion disc instabilities, Lense-Thirring/Bardeen-Petterson effects, dual jets) cannot be ruled out as causes or optional explanations for the precession.

We review participatory science programs that have contributed to the understanding of star formation. The Milky Way Project (MWP), one of the earliest participatory science projects launched on the Zooniverse platform, produced the largest catalog of ``bubbles'' associated with feedback from hot young stars to date, and enabled the identification of a new class of compact star-forming regions (SFRs) known as ``yellowballs'' (YBs). The analysis of YBs through their infrared colors and catalog cross-matching led to discovering that YBs are compact photodissociation regions generated by intermediate- and high-mass young stellar objects embedded in clumps that range in mass from 10 - 10,000 solar masses and luminosity from 10 - 1,000,000 solar luminosities. The MIRION catalog, assembled from 6176 YBs identified by citizen scientists, increases the number of candidate intermediate-mass SFRs by nearly two orders of magnitude. Ongoing work utilizing data from the Spitzer, Herschel and WISE missions involves analyzing infrared color trends to predict physical properties and ages of YB environments. Methods include applying summary statistics to histograms and color-color plots as well as SED fitting. Students in introductory astronomy classes contribute toward continued efforts refining photometric measurements of YBs while learning fundamental concepts in astronomy through a classroom-based participatory science experience, the PERYSCOPE project. We also describe an initiative that engaged seminaries, family groups, and interfaith communities in a wide variety of science projects on the Zooniverse platform. This initiative produced important guidance on attracting audiences that are underserved, underrepresented, or apprehensive about science.

The measured rates of period change, $\dot{P}$, in the signals of pulsating white dwarf stars are often interpreted as direct detections of structural changes from secular cooling. Due to the intrinsic nature of this quantity, $\dot{P}$ analysis has been used to probe fundamental physics, such as constraining the mass of hypothetical axion particles. However, most white dwarfs are expected to host planets that could induce an external source of period change, caused by the light travel time variations from reflex motion about the system barycenter. Assuming a plausible distribution of planets that could orbit white dwarf stars, we quantify the amount of reflex motion expected from undiscovered planets as an important source of extrinsic error in $\dot{P}$ analyses. While the median error from reflex motion is $\sim10^{-15}$ ss$^{-1}$ (similar to the secular $\dot{P}$ rates expected for cool DAV pulsators), individual close-in planets could cause $\dot{P}$ errors as large as $10^{-11}$ ss$^{-1}$

Identifying the nucleosynthesis processes behind heavy-element enrichment in stellar atmospheres is challenging. It typically relies on comparing observed abundance-to-iron ratios with theoretical predictions relative to the Sun, but this method is prone to uncertainty due to limitations of classical 1D hydrostatic models. One promising but still underexplored approach is to measure the isotopic composition of stellar atmospheres by focusing on elements that have both slow (s)-process and rapid (r)-process contributions. While the study of total elemental abundances offers a simplified view, isotopic ratios are directly linked to the underlying nucleosynthesis processes. Our aim is to provide a reliable method for quantifying the contributions of the s- and r-processes to barium in stellar atmospheres. This is achieved by determining barium isotopic ratios using 1D atmospheric models in combination with a carefully calibrated microturbulence, based on the comparison between subordinate and resonance Ba lines. In this initial study, we use member stars of the globular cluster NGC 6752 to calibrate the microturbulence ($v_{mic}$) value for both subordinate and resonance barium lines across different stellar evolutionary stages. This allows us to provide a reliable estimate of $v_{mic}$ that can be applied to accurately determine barium abundances and isotopic ratios in stars ranging from the main sequence to the upper red giant branch. The $v_{mic}$ scale adapted for barium subordinate lines is consistent with that derived from 3D model atmospheres, and thus the $T_{\mathrm{eff}}$-log $g$ dependent relations of the later can be used safely. The $v_{mic}$ for the resonance line at $\lambda$4934 Angstrom -- for the determination of the isotopic ratio -- is higher, and depends on the equivalent width (EW). We provide calibrated relations between $v_{mic}$ and EW for measuring isotopic ratios.

It is an open question whether small planets around M dwarfs are able to maintain atmospheres. The Hot Rocks Survey aims to address this question by observing 9 rocky exoplanets orbiting M dwarfs with MIRI emission photometry to constrain the onset of atmospheres. In this paper, we present two MIRI F1500W (15$\mu$m) eclipses of LTT 3780 b, an ultra-short period super-Earth ($P=0.768$ d, $R=1.325 \,R_\oplus$, $M = 2.46\,M_\oplus$) that receives 111x Earth's instellation, the highest in the survey. We find a combined eclipse depth of $312\pm38$ ppm, which is consistent between different data reduction and analysis assumptions, bolstering our confidence in the eclipse detection. This eclipse depth is consistent with the thermal emission from a bare rock surface, with a dayside temperature of $T_d=1143^{+104}_{-99}$ K, $98\pm9$ % of the maximum temperature predicted for a zero albedo, zero heat redistribution blackbody. We are able to confidently rule out CO$_2$-based atmospheres down to 0.01 bar surface pressure to greater than 3$\sigma$ (ruling out an approximately Mars-like atmosphere). We are unable to rule out a pure H$_2$O 1 bar atmosphere, though we argue that this composition is unlikely on such a highly irradiated planet, nor O$_2$ atmospheres due to the lack of features in the bandpass, though we can put constraints on CO$_2$-mixture atmospheres. As a potential bare rock, we consider a variety of surface composition models, but are unable to distinguish between them. However, LTT 3780 b is an excellent target for follow-up JWST observations to determine its surface composition and rule out additional atmospheric compositions.

Context. Carbon monoxide (CO) is arguably the most important molecule for interstellar organic chemistry. Its binding to amorphous solid water (ASW) ice regulates both diffusion and desorption processes. Accurately characterizing the CO binding energy (BE) is essential for realistic astrochemical modeling. Aims. We aim to derive a statistically robust and physically accurate distribution of CO BEs on ASW surfaces, and to evaluate its implications for laboratory temperature-programmed desorption experiments and interstellar chemistry, with a focus on protoplanetary disks. Methods. We trained a machine-learned potential (MLP) on 8321 density functional theory (DFT) energies and gradients of CO interacting with differently-sized water clusters (22-60 water molecules). The DFT method was selected after extensive benchmark. With this potential we built realistic non-porous and porous ASW surfaces, and computed a BE distribution. We used symmetry-adapted perturbation theory to rationalize the interaction of CO on the different binding sites. Results. We find that both ASW morphologies yield similar Gaussian-like BE distributions with mean values near 900 K. However, the nature of the binding interactions is rather different and critically depends on surface roughness and dangling-OH bonds. Simulated TPD curves reproduce experimental trends across several coverage regimes. From an astrochemical point of view, the application of the full BE distribution has a dramatic influence on the CO distribution in protoplanetary disks, leading to a broader CO snowline region, improving predictions of CO gas-ice partitioning, and suggesting an equally broader distribution of organics in these objects.

We present the analysis of one of the most extreme quasar outflows found to date in our survey of extremely high velocity outflows (EHVO). J164653.72+243942.2 (z ~ 3.04) shows variable CIV1548,1551 absorption at speeds larger than 0.1c, accompanied by SiIV, NV and Lya, and disappearing absorption at lower speeds. We perform absorption measurements using the Apparent Optical Depth method and SimBAL. We find the absorption to be very broad ({\Delta}v ~35,100 km/s in the first epoch and ~13,000 km/s in the second one) and fast (vmax ~ -50,200 km/s and -49,000 km/s, respectively). We measure large column densities ($\rm \log N_{H} >$ 21.6 $\rm\ [cm^{-2}]$) and are able to place distance estimates for the EHVO ($5\lesssim R\lesssim28$ pc) and the lower-velocity outflow ($7\lesssim R\lesssim540$ pc). We estimate a mass outflow rate for the EHVO to be $\dot M_{out}\sim50-290\rm \ M_\odot\ yr^{-1}$ and a kinetic luminosity of $\log\ L_{KE}\sim46.5-47.2\ \rm [erg\ s^{-1}$] in both epochs. The lower-velocity component has a mass outflow rate $\dot M_{out}\sim10-790\rm \ M_\odot\ yr^{-1}$ and a kinetic luminosity of $\log\ L_{KE}\sim45.3-47.2\ \rm [erg\ s^{-1]}$. We find that J164653.72+243942.2 is not an outlier among EHVO quasars in regard to its physical properties. While its column density is lower than typical BAL values, its higher outflow velocities drive most of the mass outflow rate and kinetic luminosity. These results emphasize the crucial role of EHVOs in powering quasar feedback, and failing to account for these outflows likely leads to underestimating the feedback impact on galaxies.

Over the past 15 years, the evidence has clearly demonstrated that massive black hole (MBH) binary merger timescales depend strongly on the structural and kinematic properties of their host galaxy. Stellar density, gas content, shape and kinematics all play a role, combining in non-linear ways to effect the evolution of the binary. The binary properties themselves, such as eccentricity, mass ratio, and orbital plane, all matter as well. This makes it nontrivial to estimate accurate cosmological MBH binary merger rates, or to generate merger rate ranges that reflect the distribution of galaxy hosts and orbits. Using an extensive set of high-resolution direct N-body simulations in which the shape, structure, and kinematics of each galaxy host are directly informed by observations, we map out MBH binary merger timescales over a range of galaxy hosts and MBH binary orbits. This yields a convenient set of scaling relations to determine MBH binary merger timescales -- and the range of merger timescales -- as functions of basic observables. Such scaling relations can be readily employed as a subgrid model in cosmological or semi-analytic studies, for example, to model event rates for LISA or pulsar timing.

REDWOODS on ShaneAO at Lick Observatory implements a second-stage, 3-sided reflective pyramid wavefront sensor (PWFS), which, under low-light conditions, offers an improved signal-to-noise ratio for deformable mirror commands to correct dynamic atmospheric aberrations. We modeled the REDWOODS limiting natural guide star magnitude. We also investigated performance tradeoffs between two PWFS modes that are available to REDWOODS, one with higher bandwidth error and another with higher aliasing error. We also implemented an experimental setup to image one of the REDWOODS PWFS masks.

Recent observations with the James Webb Space Telescope (JWST) reveal young massive clusters (YMCs) as key building blocks of early galaxies. They are not only important constituents of galaxies, but also potential birthplaces of very massive stars (VMSs) and black hole (BH) seeds. We explore stellar dynamics in extremely dense clusters with initial half-mass densities of $\rho_h \gtrsim 10^8M_\odot{\rm pc}^{-3}$ at very low metallicity, comparable to some of the densest clusters seen by JWST. Using direct N-body and Monte Carlo simulations with stellar evolution, we show that VMS formation through collisions is unavoidable, with final masses reaching $5\times10^3$ to $4\times10^4M_\odot$. These results support the existence of a critical mass scale above which collisions become highly efficient, enabling the formation of VMSs and intermediate-mass BHs (IMBHs). Our models, using nbody6++gpu and MOCCA with updated SSE/BSE routines, show that dense clusters rapidly form VMSs via stellar bombardment. The VMSs then collapse into BH seeds of a few $10^3$ to $10^4M_\odot$ in less than 4 Myr. We identify a critical mass-density threshold beyond which clusters undergo runaway collisions that yield massive BH seeds. For typical YMCs detected by JWST, efficiencies up to 10% are expected, implying BH masses up to $10^5M_\odot$ if formed via collisions. We predict a scaling relation for BH mass, $\log(M_{\rm BH}/M_\odot)=-0.76+0.76\log(M/M_\odot)$. Frequent VMS formation may also explain the high nitrogen abundance observed in galaxies at high redshift.

We present optical integral-field spectroscopic data of ten nearby ($0.02\leq z \leq 0.05$) Seyfert 1 galaxies taken with the Keck Cosmic Web Imager (KCWI). We map the spatially resolved kinematics of the [O III] gas and stars, and investigate the alignments between their global kinematic position angles (PA). Large-scale gas motions are primarily dominated by rotation, and are kinematically aligned with the stars ($\Delta\text{PA}\leq 30$ deg). However, eight galaxies exhibit non-rotational kinematic signatures (e.g., kinematic twists, possible outflows) in their ionized gas velocity fields near the nucleus. We compare aperture-wide measurements of the gas and stellar velocity dispersions ($\sigma_{\text{gas}}$ and $\sigma_\star$) to test the use of the width of the [O III] line core as a surrogate for $\sigma_\star$. Direct comparisons between $\sigma_{\text{gas}}$ and $\sigma_\star$ show that $\sigma_{\text{gas}}$ tends to underestimate $\sigma_\star$, and thus is not a reliable tracer of $\sigma_\star$ for our selected galaxies. We measure the extent of the narrow-line region (NLR) using several definitions, resulting in sizes of $\sim0.1$-$10$ kpc. For a given [O III] luminosity, our NLR sizes derived from the [O III]/H$\beta$ flux ratio or an [O III] isophotal radius are an order of magnitude larger than those measured from past imaging data.

It is now widely established that globular clusters host robust populations of white dwarfs, neutron stars, and black holes throughout their lifetimes. Within clusters, dynamical processes enabled by stellar densities thousands to millions of times larger than typical galactic environments facilitate interactions involving these stellar remnants that give rise to an array of astrophysical phenomena. In particular, stellar clusters have emerged as an important formation site for X-ray sources, radio pulsars, and merging black hole binaries similar to those recently detected as gravitational wave sources by the LIGO/Virgo/KAGRA detectors. This article reviews our current understanding of compact objects in globular clusters, discussing current observational evidence, ways these objects influence the dynamical evolution of their hosts, and future prospects.

We present the mass--spin diagram for classifying black holes and studying their formation pathways, providing an analogue to the Hertzsprung-Russell diagram. This allows for black hole evolutionary tracks as a function of redshift, combining formation, accretion, and merger histories for the variety of black hole populations. A realistic black hole continuum constructed from initial mass and spin functions and approximate redshift evolution reveals possible black hole main sequences, such as sustained coherent accretion through cosmic time (i.e., Cosmic Accretion) or hierarchical merger trees. In the stellar-mass regime, we use a binary population synthesis software to compare three spin prescriptions for tidal evolution of Wolf-Rayet progenitors, showing how the mass--spin diagram exposes interesting modeling differences. We then classify black hole populations by applying supervised and unsupervised machine learning clustering methods to mass--spin datasets. While bare unsupervised clustering can nearly recover canonical population boundaries (stellar-mass, intermediate-mass, and supermassive), a more sophisticated approach utilizing deep learning via variational autoencoders for latent space representation learning aids in clustering of realistic datasets with subclasses that highly overlap in mass--spin space. We find that a supervised random forest can accurately recover the correct clusters from the learned latent space representation depending on the complexity of the underlying dataset, semi-supervised methods show potential for further development, and the performance of unsupervised classifiers is a great challenge. Our findings motivate future machine learning applications and demonstrate that the mass--spin diagram can be used to connect gravitational-wave and electromagnetic observations with theoretical models.

The Chromospheric LAyer SpectroPolarimeter missions, CLASP2 and CLASP2.1, demonstrated that the near-UV spectral region between 279.30 and 280.68 nm is suitable for studying the magnetism of the solar chromosphere. In particular, the spectropolarimetric observations in the Mg II h and k resonant doublet, Mn I 279.91 and 280.19 nm resonant lines, and Fe II 279.79 and 280.66 nm lines acquired by these suborbital space experiments have been proven useful for inferring the magnetic field stratification in the solar chromosphere. However, several lines of the CLASP2/2.1 spectral region with significant circular polarization signals had remained unexplored. After identifying two Ni I (279.95 and 280.59 nm), one Mn II (280.62 nm), and one Fe I (280.53 nm) lines, here we apply the Weak Field Approximation (WFA) to the spectropolarimetric observations of active region plages by CLASP2 and CLASP2.1. By comparing the results with previous studies, we are able to estimate the formation heights of these CLASP2/2.1 additional spectral lines and to demonstrate their suitability to determine the magnetic field stratification from the photosphere to the upper chromosphere.

Variability detected in galaxies is usually attributed to their active galactic nuclei (AGNs). While all AGNs are intrinsically variable, the classic AGN unification model predicts that type~2 AGNs rarely vary because their engines are obstructed by dust tori. Previous UV-to-near-IR variability studies largely support this expectation. Here, we present a variability study by James Webb Space Telescope (JWST) that reveals a more subtle picture. Using NIRCam imaging data from three surveys over $\sim$140~arcmin$^2$ in the COSMOS field, we found 117 galaxies with $\geq 4$$\sigma$ variability in the F356W band across a $\sim$2-year baseline. Cross-matching with existing JWST spectroscopic data in this area, we identified five of them at $z=0.19$--3.69, which were all coincidentally observed by a NIRSpec program almost contemporaneously with the last imaging epoch. One additional variable was identified at $z=0.90$ using the archival Keck telescope data. These six objects form our spectroscopic subsample. Interestingly, two reside in close-pair environments, while two others form a close pair themselves. Most of their light curves can hardly be explained by nuclear transients, and AGN variability is a more plausible cause. However, among these six objects, (1) only one shows broad permitted lines ($\Delta v > 1000$~km~s$^{-1}$) indicative of a type~1 AGN; (2) two show narrow permitted lines consistent with type~2 AGNs, with another one likely type~2 based on the host galaxy properties; and (3) two others, which form a pair, show no emission lines. Our results add more challenges to the unification model.

Young eruptive stars such as EXors undergo dramatic accretion outbursts characterized by sudden optical brightenings, yet the underlying physical mechanism remains uncertain. We present high-resolution ALMA Band 3 and 4 continuum observations of EX Lupi, the prototypical EXor-type variable, reconstructed using super-resolution imaging with sparse modeling. Our images reveal, for the first time, two distinct substructures: a compact, crescent-shaped inner arc within 10 au of the star, and a narrow outer ring at 30 au. The inner arc is strongly elongated and casts a shadow observed in the VLT/SPHERE near-infrared scattered light. The outer ring exhibits a radial width comparable to the local pressure scale height, consistent with moderately efficient dust trapping. Geometric and thermal analysis of the disk surface, based on combined ALMA and SPHERE data, indicates that the disk is moderately flared with an average disk temperature consistent with that of classical T Tauri disks. The observed substructures suggest dynamical perturbations-plausibly induced by a massive companion-that may modulate accretion rates through gravitational interaction with the inner arc. These findings provide morphological evidence linking disk substructure to episodic accretion in the structurally mature disk.

We explore the cosmic expansion history within the framework of Galileon gravity by employing a redshift-based expression for the Hubble rate, $H(z)$, derived from the CPL parametrization $\omega_{DE}(z)=\omega_{0}+\omega_{a}\frac{z}{1+z}$. This parametrization allows for a time-dependent expansion history consistent with the non-linear Galileon field equations. To constrain the model parameters, we perform a MCMC analysis using $46$ Hubble parameter measurements, DESI DR2 BAO data and $1701$ Pantheon+ datasets. The best fit values obtained are $H_0 = 67.7043^{+1.4354}_{-1.4102}$ km/s/Mpc, $\Omega_{m0} = 0.2668^{+0.0212}_{-0.0217}$, $\omega_0 = -0.8827^{+0.1076}_{-0.0967}$ and $\omega_a = 0.0011^{+0.0660}_{-0.0622}$. Model comparison using information criteria yields $\Delta AIC=1.46$ and $\Delta BIC = 11.5$ indicating that the Galileon model is a strong contender to the $\Lambda$CDM model. The deceleration parameter shows a transition at $z_{tr} = 0.7873$, with $q_0 = -0.598$. Energy density and pressure remain physically viable with $\rho_{de}(z)>0$ and $p_{de}(z)<0$ with the present day equation of state $\omega(z)$ value of $-0.2915$, which suggests mild dynamical dark energy. NEC and DECare satisfied, while SEC is violated. The model yields $r_{0}=0.657$, $s_{0}=0.1173$ and Om diagnostic shows a peak value of $-0.45$ at $z = 0.377$, converging to $-1$ at late this http URL results demonstrate that Galileon gravity remains a viable and flexible alternative to $\Lambda$CDM in describing late-time cosmic acceleration.

Binary neutron stars (BNSs) are among the most interesting sources for multimessenger studies. A number of recently discovered BNSs in the Milky Way by radio telescopes have added new information to the parameter distribution of the Galactic BNSs. The scarce of BNS mergers during the O4 run of the LIGO-Virgo-Kagra (LVK) suggests a BNS local merger rate six times lower than the previous constraint obtained by O1-O3 runs. With these new multimessenger observations, in this letter, we adopt the compact binary population synthesis model and Bayesian analysis to constrain the formation and evolution of BNSs, especially the common envelope (CE) evolution. We find that it is required: (1) a fraction ($f_{\rm HG}\sim0.8$) but not all of the Hertzsprung gap donors merged with their companions in the CE stage, in order to simultaneously explain the low BNS merger rate density and the existence of the short-orbital-period ($\lesssim 1$ day) Galactic BNSs, different from either all ($f_{\rm HG}=1$) or none ($f_{\rm HG}=0$) adopted in previous studies; (2) a large CE ejection efficiency $\alpha$ ($\sim 5$), in order to explain the existence of the long-orbital-period ($\gtrsim 10$ day) Galactic BNSs.

We have re-processed single pulse candidates from the first four years (1997-2001) of the Parkes Multibeam receiver system observations, creating a new Parkes transient database (PTD II) that contains 165,592 single pulses from 363 known pulsars. Unlike previous databases, PTD II preserves the critical raw data segments of each detected pulse, enabling detailed analyses of emission physics while maintaining a compact size of only 1.5 GB. The database employs a sqlite3 structure organising pulsar metadata, observation files, and pulse events with their raw data stored in binary format. We provide processing tools for extracting and analysing single-pulse data, enabling fluence fitting and statistical analysis. Our pulsars exhibit diverse fluence distributions, such as log-normal, Gaussian, and unimodal. Temporal analyses reveal significant evolution in emission characteristics of several pulsars, including event rate variations spanning two orders of magnitude in PSR J1602-5100 and PSR J0942-5552. Beyond supporting fundamental pulsar emission studies, the database serves as a valuable training resource for developing new single-pulse detection algorithms in the presence of radio frequency interference.

NASA's Nancy Grace Roman Space Telescope, slated to launch in October 2026, will serve a critical role in the characterization and threat assessment of near-Earth Objects (NEOs), thus contributing to national and international planetary defense objectives. Operating from the Earth-Sun L2 point and observing in the near-infrared, Roman has the high sensitivity and high spatial resolution needed to measure the physical properties, compositions, and orbital trajectories of NEOs in order to understand their physical nature and potential hazards to Earth. Roman's planetary defense capabilities complement those of two wide-field survey missions: the now operational ground-based Vera C. Rubin Observatory's Legacy Survey of Space and Time and the upcoming space-based NEO Surveyor. Rubin, observing in visible light, will discover over 100,000 NEOs. NEO Surveyor, observing in the mid-infrared where NEO thermal emission peaks, will detect 200,000-300,000 NEOs, some as small as ~20 meters in diameter. With investment in developing the pipeline infrastructure required to extract information from moving target streaks, Roman will be able to observe NEOs down to the smallest sizes in order to improve our measurements of NEO orbits by 2-3 orders of magnitude, enable accurate diameter and albedo estimates in conjunction with NEO Surveyor, and reveal the spectral types and bulk compositions of the smallest NEOs. Together, these three US-led facilities will operate across the electromagnetic spectrum to form a comprehensive planetary defense network.

Fast Radio Bursts (FRBs) are a unique probe of the cosmos, owing to dispersion caused by free electrons in the intergalactic medium (IGM). Two of the main quantities of interest are degenerate: the density of matter $\Omega_\mathrm{b}f_\mathrm{d}$ outside of galaxies and the Hubble constant $H_0$. Here, we present a new possibility of breaking the degeneracy without invoking early Universe priors on $\Omega_\mathrm{b}$. Assuming some FRBs originate in compact object mergers, the combination of dispersion and luminosity distance from the gravitational wave (GW) can be used to measure $\Omega_\mathrm{b}h^2f_\mathrm{d}$ (where $h$ is the dimensionless Hubble constant). We show that this measurement can be combined with the abundant FRBs that have a redshift measurement. This combination breaks the degeneracy with the Hubble constant. We develop a Bayesian framework and forecast that third-generation GW detectors are required to obtain meaningful constraints. We forecast that one year of Einstein Telescope operations can constrain $H_0$ to $\pm 6\,\mathrm{km}\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$ and $\Omega_\mathrm{b}h^2f_\mathrm{d}$ to $^{+0.0015}_{-0.0016}$ (68$\,\%$ credible interval). The method can also be used with luminosity distances obtained through other means than GWs.

Coronal mass ejections (CMEs) typically exhibit a three-component structure in white-light (WL) coronagraphs. Utilizing the seamless observations of the inner corona ($\le$ 3 R$_\odot$), we have revealed the early evolution of the cavity and core of a CME starting at $\sim$18:20 UT on 2014 October 14. The CME originates from a hot channel (HC), which appears as the bright core and compresses the cavity in WL images. Specifically, most of the dark cavity in WL is filled by bright loop-like structures in 174 Å. The differential emission measure (DEM) analysis indicates that the electron temperature decreases from the core ($\sim$13.4 MK) to the cavity ($\sim$1.35 MK), and the CME cavity is significantly cooler than that enshrouding a prominence ($\ge$ 2 MK). The effective temperature of the cavity increases over time in general, probably due to the compression by the HC expansion. The evolution of the CME bright core includes slow-rise, fast-rise (up to $\sim$330 km s$^{-1}$), and residual-acceleration phases. The cavity exhibits an evolution similar to the core but lags by $\sim$4 minutes, with a lower speed peaking at $\sim$220 km s$^{-1}$. Moreover, the 2D radial speed distribution exhibits the highest speeds at the core apex. The kinematical results further confirm the compression of the cavity. The present event supports the new explanation of the CME structures, i.e., the magnetic flux rope (MFR), which is proxied by the HC, is only responsible for the core, while the cavity is likely a low-density region between the CME front and the MFR.

The coronal heating problem is one of the most critical challenges in solar physics. Recent observations have revealed that small-scale swirls are ubiquitous in the photosphere and chromosphere, suggesting that they may play a significant role in transferring magnetic energy into the corona. However, the overall contribution of swirls to the total magnetic energy supply and subsequent coronal heating remains uncertain. To address this, we perform statistical analyses of simulated swirls using a three-dimensional radiative magnetohydrodynamic simulation extending from the convection zone to the corona in the quiet Sun. Our results reveal that swirls account for approximately half of the total magnetic energy. Furthermore, they strongly suggest that swirls can trigger coronal heating events through magnetic reconnection. The occurrence frequency of these events follows a power-law-like distribution, consistent with observations of coronal heating signatures known as "nanoflares", indicating that swirls are promising candidates as their drivers.

Pulsating detached eclipsing binary systems are crucial for studying the internal structure of oscillating stars. These systems are advantageous because binary effects on pulsations are minimal, allowing for more accurate determinations of fundamental stellar parameters such as mass and radius. They serve as unique laboratories for detailed investigations of pulsating stars. In this study, we focused on four detached eclipsing binaries exhibiting $\delta$ Scuti-type oscillations: HD 117476, 205 Dra, HY Vir, and V1031 Ori. Our preliminary investigation showed that all binary components of these targets lie within the $\delta$ Scuti instability strip. Therefore, we aimed to determine which components are pulsating and which are not, and to explore the differences between them. To achieve this, we analyzed TESS photometric data and high-resolution spectra of the targets. Radial velocity variations were measured, and atmospheric parameters for each component were derived using spectral disentangling or synthetic composite spectra. We also modeled the binary light and radial velocity curves to determine the fundamental physical parameters of the components. Furthermore, we examined pulsation properties using three different approaches to identify the pulsating components. The evolutionary status of the targets was also assessed. Our analysis revealed that, in each system, only one component exhibits $\delta$ Scuti-type pulsations, while the others are non-pulsating. Interestingly, we found that the key difference between pulsating and non-pulsating components within the same binary is metallicity: the metal-rich components were found to be non-pulsators, supporting theoretical studies on the effect of metallicity on $\delta$ Scuti-type pulsations.

We present the description of the instruments and the first results of the PRime-focus Infrared Microlensing Experiment (PRIME). PRIME is the first dedicated near-infrared (NIR) microlensing survey telescope located at the South African Astronomical Observatory (SAAO) in Sutherland, South Africa. Among its class, it offers one of the widest fields of view in the NIR regime. PRIME's main goals are (1) To study planetary formation by measuring the frequency and mass function of planets. In particular, we compare results from the central Galactic bulge (GB), accessible only in the NIR by PRIME, with those from the outer GB by optical surveys. (2) To conduct concurrent observations with NASA's Nancy Grace Roman Space telescope. Due to the different lines of sight between the ground and space, we detect slight variations in light curves, known as ``Space-based parallax." This effect allows us to measure the mass of lens systems and their distance from the Earth. It is the only method to measure the mass of the free-floating planets down to Earth-mass. We begin the GB survey in February 2024 and analyzed images through June 1, 2025, identifying 486 microlensing candidates and over a thousand variable stars, including Mira variables, which are useful to study the Galactic structure. We issue real-time alerts for follow-up observations, supporting exoplanet searches, and the chemical evolution studies in the GB. During the off-bulge season, we conduct an all-sky grid survey and Target of Opportunity (ToO) observations of transients, including gravitational wave events, gamma-ray bursts, and other science.

We present high-resolution radio observations of the pulsar wind nebula (PWN) MSH15-52, which is renowned for its distinctive hand-like shape, and its associated supernova remnant RCW 89. Using the Australia Telescope Compact Array (ATCA), we obtained 3 and 6,cm radio maps with a resolution of 2 arcsec. These unveil small-scale radio features in the system and allow a direct comparison with the arcsecond-resolution X-ray images. We find that the radio emission is composed of a complex filamentary structure. In particular, there is a bar-like feature across the central pulsar B1509-58 in the inner PWN, and the radio sheath wrapping around the pulsar also appears to be made up of filaments. Some prominent X-ray features are not detected in radio, including the one-sided jet in the south and the finger-like structures in the north. These indicates turn over of the particle distribution at low energies in these regions. For RCW 89, the radio emission well coincides with both the X-ray knots and the H{\alpha} filaments. The high polarization fraction shows that the emission is synchrotron in nature, but it extends well beyond the sharp boundary of the non-thermal X-ray emission, which is difficult to explain.

The questions of the rarity of the 4.8 GHz formaldehyde masers and the non-detection of 14.5 GHz formaldehyde masers are addressed from a theoretical point of view. The pumping free-free radiation fields were obtained using the photo-ionization code Cloudy to simulate hyper-compact HII regions. Implementation of these free-free radiation fields in solving the rate equations shows that the free-free radiation fields of some hyper-compact HII regions are ineffective to invert the 4.8 GHz transition. Investigation of the variation of the inversion of the 4.8 GHz and 14.5 GHz transitions with radial distance revealed that there are regions where only the 4.8 GHz transition is inverted. It is also shown that the projection of the masing region toward the edge of a hyper-compact may explain the non-detection of 14.5 GHz masers. The attenuation of the 4.8 GHz and 14.5 GHz masers in the molecular envelope is investigated. It is found that attenuation can be significant. Comparison of the velocities of the 4.8 GHz masers with the centre velocities of associated 4.8 GHz absorption features shows that the maser emission lies at the edge of the absorption features. This suggests that the masers may be associated with kinematic structures such as rotating toroids.

Directly imaging exoplanets is a formidable challenge due to extreme contrast ratios and quasi-static speckle noise, motivating the exploration of advanced post-processing methods. While Convolutional Neural Networks (CNNs) have shown promise, their inherent limitations in capturing long-range dependencies in image sequences hinder their effectiveness. This study introduces a novel hybrid deep learning architecture that combines a CNN feature extractor with a Transformer encoder to leverage temporal information, modeling the signature of a planet's coherent motion across an observation sequence. We first validated the model on a purely synthetic dataset, where it demonstrated excellent performance. While the final metrics varied slightly between training runs, our reported trial achieved 100.0% accuracy, a 100.0% F1-score, and a position accuracy of 0.72 pixels, showing strong results on this specific test case in comparison to traditional methods like median subtraction and PCA-KLIP. To assess its viability on realistic data, we retrained the model on a semi-synthetic dataset created by injecting planet signals into actual high-contrast imaging observations of the TW Hya protoplanetary disk from JWST. The model successfully identified the injected signals with high confidence, confirming its ability to function amidst complex, correlated noise and bright disk features. This work serves as a successful proof-of-concept, demonstrating that a CNN-Transformer architecture holds significant promise as a fast, accurate, and automated method for exoplanet detection in the large datasets expected from current and future high-contrast imaging instruments.

The angular and spectral features of neutrinos emitted from primordial black holes (PBHs) carry key imprints of the black hole's fundamental properties. This work investigates the directional emission of neutrinos from Kerr-Newman PBHs undergoing Hawking evaporation, accounting for the combined effects of spin, motion, and electric charge. Rotation induces anisotropic fluxes through axisymmetric geometry and spin-dependent greybody factors, while relativistic motion leads to pronounced Doppler beaming along the direction of travel. Electric charge modifies the thermodynamic evolution and suppresses the emission of like-charged particles, altering the overall spectrum and burst duration. The resulting neutrino flux exhibits rich angular structure, energy dependence, and time profiles that vary with PBH parameters. These directional signatures enhance the prospects for detection at current and future neutrino observatories, and offer new multi-messenger probes of PBH populations in the early universe.

The polarized emission of astrophysical masers, especially OH and methanol lines, is an effective tool to study the magnetic field in high-mass star-forming regions. The magnetic field strength measurement via the Zeeman effect of OH maser emission is well established, but that of the methanol maser emission is still under debate because of its complex hyperfine structure. We aim to identify the dominating hyperfine transition of the Class II methanol maser emission by comparing the magnetic field strength measured with the excited OH maser emission and the Zeeman splitting of the methanol maser emission. We used quasi-simultaneous EVN observations of the two maser emissions at 6.035 GHz ex-OH and 6.668 GHz methanol toward two well-known high-mass young stellar objects: ON 1 and W75N. The observations were performed in full polarimetric mode and in phase-referencing mode to couple the maser features of the two maser emissions in each source. We detected linearly and circularly polarized emission in both maser transitions and HMYSOs. Specifically, we measured the magnetic field strength in twelve and five ex-OH maser features toward ON1 and W75N, respectively, and the Zeeman splitting of the methanol maser spectra in one and three maser features toward ON 1 and W75N, respectively. We determined that the two maser emissions likely probe the same magnetic field but at different densities. Indeed, a direct comparison of the magnetic field strength and the Zeeman splitting as measured with the ex-OH and methanol maser spots, respectively, provided values of the Zeeman splitting coefficient for the 6.7 GHz maser that do not match any of the table values present in the literature. We are not able to uniquely identify the dominating hyperfine transition; however, through density considerations, we can narrow the choice down to three hyperfine transitions: 3->4, 6->7A, and 7->8.

New JWST observations have revealed the presence of a significant number of high-redshift barred galaxies. The origin of these bars remains unclear, and their properties appear difficult to reconcile with the results of cosmological simulations of galaxy formation. I present an example of a tidally induced bar-like galaxy formed at z = 2.9 in the TNG100 suite of the IllustrisTNG simulations. The galaxy was identified among the sample of bar-like galaxies studied before and has the earliest bar formation time among the tidally induced subsample of those objects. Its disk transformed into a bar as a result of a close interaction with a massive progenitor of a brightest cluster galaxy (BCG). It remained on a tight orbit around the host and survived until the present, losing most of its initial mass and becoming red but preserving its prolate shape. Even before the interaction, at z = 3.5, the galaxy experienced a few mergers, which elongated its shape. This temporary distortion also made it look like a bar with spiral extensions of up to 6 kpc. The long-lived bar formed later was about 3 kpc long and grew over the next few gigayears. This example demonstrates that high-z bars should not be sought among the progenitors of present-day simulated barred galaxies but rather among the tidally interacting early population of galaxies in forming groups and clusters. Some of these galaxies may have survived as ellipticals, and some may have merged with their BCGs.

We investigate the optical shock emission from the Large Magellanic Cloud supernova remnant 0540-69.3 (SNR 0540) using MUSE integral-field-unit data from the VLT. The observations cover the spectral range 4650-9300 $Å$ and provide a $1\times1$ arcmin$^{2}$ field of view, encompassing nearly the entire remnant. We analyse the spatial and spectral properties of shock-related emission lines, and identify clumpy optical shock emission e.g. from [S II] $\lambda\lambda$6716,6731 doublet and the coronal [Fe XIV] $\lambda$5303 line (typically at radial velocities $\lesssim|100|$ km s$^{-1}$ and $\lesssim|170|$ km s$^{-1}$, respectively). These features trace the blast-wave shell seen in previous X-ray studies. Post-shock electron density estimates, based on the [S II]-line ratio, reveal spatial variation, with the highest densities ($\sim10^4$ cm$^{-3}$) in the bright knots in the west, and lower densities ($\sim3\times10^3$ cm$^{-3}$) in the east. The density in the north (southwest) appears significantly lower (higher) but remains unconstrained due to limited signal. We also estimate blast-wave shock velocities using the [Fe XIV] $\lambda$5303/[Fe XI] $\lambda$7892 ratio, finding low velocities ($\sim400$ km s$^{-1}$), consistent with previous studies. All these results support the scenario that the blast wave is interacting with the surrounding interstellar medium, particularly in the western regions. Additionally, we detect four unidentified emission lines, $\sim$2000-3000 km s$^{-1}$ south from the pulsar in transverse velocity, but their origin remains unclear. Possible explanations, including Fe lines from a high-velocity ejecta clump, all present challenges. Our findings highlight the complex nature of the circum- and interstellar medium surrounding SNR 0540.

Supernovae (SNe) IIn are terminal explosions of massive stars that are surrounded by a dense circumstellar medium (CSM). Among SNe IIn, a notable subset is the SNe 2009ip-like, which exhibit an initial, fainter peak attributed to stellar variability in the late evolutionary stages, followed by a brighter peak, interpreted as the SN explosion itself. We analyse the spectrophotometric evolution of SN 2024hpj, a SN IIn with signs of precursor activity. Comparing it with similar objects in the literature, we identify star-forming regions as their preferred environments, while a statistical analysis on the observed rate of SNe 2009ip-like indicates progenitor masses around 25 - 31 solar masses and lower. The diversity of spectrophotometric features within the sample suggests that variations in CSM mass and distribution influence the observed characteristics, indicating a shared progenitor scenario.

The role of novae as producers of galactic lithium has been suggested since the 1970s, and it has been reconsidered recently with the detection of $^7$Be in their outbursts. At the same time, stellar models are moving forward to comprehend the discrepancy between the primordial lithium abundance predicted by the standard Big Bang Nucleosynthesis theory and the measured value of old dwarf stars. In this work, we follow the evolution of $^7$Li in the galactic thin disc starting from a primordial value of A(Li)=2.69 dex and applying $^7$Li depletion corrections of the stellar model with overshooting to our chemical evolution models. We use the upper envelope of the observational data to constrain the models. In addition to the dwarf main sequence (MS) stars, our analysis includes, for the first time, the early red-giant-branch (RGB) stars. Besides the renowned Spite plateau of the MS stars at low metallicities, we also confirm the existence of a second A(Li) plateau of the early RGB stars, which can be explained by our model with the corrections from stellar models. Our best-fit model is obtained with an effective averaged $^7$Li yield $^{Li}Y_\mathrm{Nova}=2.34\times 10^{-5} M_\odot$ during the whole lifetime of a nova. This reinforces the possibility that novae are the main galactic $^7$Li source, together with the stellar models' ability to comprehend the "cosmological lithium problem" in this context.

The Vanilla Power Law Inflation is plagued with two severe drawbacks, the one being the issue of graceful exit, and the other being its compatibility with the existing data. There's yet another daunting problem generic to any inflationary model, and not particular to the Power Law Inflation, is the issue of classicalization of the primordial quantum perturbation. This issue is often treated as an isolated problem primarily because decoherence is often invoked to tackle such problems and decoherence, in principle, doesn't leaves any observational imprints. However, that's not the case if one invokes the collapse models of quantum mechanics to resolve such a problem, because the collapse models do modify the Schrödinger evolution of the quantum system and the modified dynamics is bound to leave imprints. We show that collapsed modified Power Law Inflation can indeed circumvent the issue with observations and can be made compatible with all the current data coming from {\it Planck}, {\it ACT}, DESI and BAO while resolving the classicalization issue associated with the quantum primordial fluctuations. Such an inflationary model also produces a more red-tilted tensor spectrum and no running for both the scalar and tensor spectral indices, which can be a litmus test for this model.

Strong gravitational lensing offers a powerful and direct probe of dark matter, galaxy evolution and cosmology, yet strong lenses are rare: only 1 in roughly 10,000 massive galaxies can lens a background source into multiple images. The European Space Agency's Euclid telescope, with its unique combination of high-resolution imaging and wide-area sky coverage, is set to transform this field. In its first quick data release, covering just 0.45% of the full survey area, around 500 high-quality strong lens candidates have been identified using a synergy of machine learning, citizen science and expert visual inspection. This dataset includes exotic systems such as compound lenses and edge-on disk lenses, demonstrating Euclid's capacity to probe the lens parameter space. The machine learning models developed to discover strong lenses in Euclid data are able to find lenses with high purity rates, confirming that the mission's forecast of discovering over 100,000 strong lenses is achievable during its 6-year mission. This will increase the number of known strong lenses by two orders of magnitude, transforming the science that can be done with strong lensing.

We investigate the formation of stellar bars in 307 Milky Way-mass disc galaxies in the TNG50 cosmological simulation. Most bars form rapidly in dynamically cold discs shortly after the central stellar mass exceeds that of dark matter. In these cases, bar formation is consistent with secular instabilities driven by the disc's self-gravity, which organises stellar orbits into a coherent bar structure. However, around 25 per cent of barred galaxies are dark matter dominated at the time of bar formation, $t_{bar}$, and remain so thereafter. We trace the origin of these bars to tidal perturbations induced by passing satellites or mergers using a new metric, $S_{bar}$, quantifying the tidal field acting on the galaxy. At the time of bar formation, we find a negative correlation between $S_{bar}$ and the central stellar-to-dark matter mass fraction, indicating that more dark matter-dominated discs require stronger tides to trigger bar formation. These tidally induced bars are more likely to be transient than those that form secularly, although bar properties are otherwise similar. However, the host galaxies differ: secular bars arise in relatively compact discs, while tidal bars appear in extended discs whose properties resemble those of unbarred galaxies. Tidal perturbations can therefore induce bars in galaxies otherwise stable to secular formation, highlighting the dual role of the internal galactic structure and the external environment in bar formation.

We present the early radio detection and multi-wavelength modeling of the short gamma-ray burst (GRB) 231117A at redshift $z=0.257$. The Australia Telescope Compact Array automatically triggered a 9-hour observation of GRB 231117A at 5.5 and 9 GHz following its detection by the Neil Gehrels Swift Observatory just 1.3 hours post-burst. Splitting this observation into 1-hour time bins, the early radio afterglow exhibited flaring, scintillating and plateau phases. The scintillation allowed us to place the earliest upper limit ($<10$ hours) on the size of a GRB blast wave to date, constraining it to $<1\times10^{16}$ cm. Multi-wavelength modeling of the full afterglow required a period of significant energy injection between $\sim 0.02$ and $1$ day. The energy injection was modeled as a violent collision of two shells: a reverse shock passing through the injection shell explains the early radio plateau, while an X-ray flare is consistent with a shock passing through the leading impulsive shell. Beyond 1 day, the blast wave evolves as a classic decelerating forward shock with an electron distribution index of $p=1.66\pm0.01$. Our model also indicates a jet-break at $\sim2$ days, and a half-opening angle of $\theta_j=16\mathring{.}6 \pm 1\mathring{.}1$. Following the period of injection, the total energy is $\zeta\sim18$ times the initial impulsive energy, with a final collimation-corrected energy of $E_{\mathrm{Kf}}\sim5.7\times10^{49}$ erg. The minimum Lorentz factors this model requires are consistent with constraints from the early radio measurements of $\Gamma>35$ to $\Gamma>5$ between $\sim0.1$ and $1$ day. These results demonstrate the importance of rapid and sensitive radio follow-up of GRBs for exploring their central engines and outflow behaviour.

Phase transitions in the early Universe give rise to effective masses for massless fields in the symmetry-broken phase. We use the lattice simulations to investigate the impact of a spectator scalar field with mass generation on the dynamics of first-order phase transitions and the generation of gravitational waves. In addition to the well-known friction effects, we identify a novel effect that significantly enhances the strength of first-order phase transitions. The amplitude of the mass-acquiring field is highly suppressed in the true vacuum bubbles, resulting in additional release of vacuum energy that concentrate on the bubble walls. We also establish an analytical method to explain our numerical results.

We compare the excitation of the Narrow-Line Region (NLR) of type 1 and type 2 QSOs for redshifts $0.4 \le z \le 0.5$ via the analysis of their emission line properties in Sloan Digital Sky Survey (SDSS) near-UV/optical spectra. We fit the continuum and emission lines, using two kinematic components for \oiii$\lambda$5007 and \hb\ (narrow and broad) and a single component for the weaker lines. We find two main differences in the NLR excitation of type 1 and 2 QSOs: (i) QSOs 2 have higher \oiii/\hb\ than QSOs 1 in both narrow and broad components; (ii) QSOs 1 present higher \nev, \neiii\ and \oiii$\lambda4363$ luminosities, higher \nev/\neiii\ and \neiii/\oii\ ratios and higher temperatures than QSOs 2. These differences support more highly excited regions, higher temperature gas and prevalence of shocks in type 1 relative to type 2 QSOs. We suggest two possible scenarios: (i) type 1 QSOs are seen more pole-on, allowing the observation of more highly excited gas closer to the nucleus, supporting the Unified Model scenario; (ii) evolution from type 2 to type 1 QSOs, with highest excitation regions obscured in type 2's and cleared up in a ``blow-out phase". Support for the evolutionary scenario is given by the usually higher L\oiii\ in QSOs 2, in the sense that these sources host a more powerful AGN that, in its evolution, clears up the excess dust and gas to reveal a lower-luminosity but more highly excited type 1 AGN.

The Small Magellanic Cloud (SMC) has been tidally shaped by the interaction with the Large Magellanic Cloud (LMC). The scope of such an interaction has recently been studied from different astrophysical properties of its star cluster population, which point to star clusters placed remarkably outside the known extension of the galaxy. In this work we report results for three of the recently identified most external SMC star clusters, OGLE-CL-SMC0133, OGLE-CL-SMC0237, and Lindsay~116, using deep GEMINI GMOS imaging. Once we confidently cleaned their color-magnitude diagrams from field star contamination, we estimated their fundamental parameters applying likelihood techniques. We also derived their structural parameters from normalized star number density radial profiles. Based on {\it Gaia} astrometric data, complemented with kinematics information available in the literature, we computed the 3D components of their space velocities. With similar ages (~ 2.2 Gyr) and moderately metal-poor overall abundances ([Fe/H] = -1.0 - -0.7 dex), OGLE-CL-SMC0237 is placed at 2.6 kpc from the SMC center and shares its disk rotation; OGLE-CL-SMC0133 is located at 7.6 kpc from the galaxy center and exhibits a kinematics marginally similar to the SMC rotation disk, while Lindsay~116 placed at 15.7 kpc from the center of the SMC is facing strong perturbations of its orbital motion with respect to an ordered rotational trajectory. Furthermore, its internal dynamical evolution would seem to be accelerated -- it seems kinematically older -- in comparison with star clusters in the outskirts of relatively isolated galaxies. These outcomes lead to conclude that Lindsay~116 is subject to LMC tides.

Io is one of Jupiter's largest moons and the most volcanically active body in the Solar System. Its very active surface has hot spots produced by volcanic eruptions popping up at seemingly random locations and times. Characterizing the complex surface of Io requires the highest angular resolution available. This work presents the analysis of Aperture Masking Interferometric observations (at 4.3 um) of Io taken with the Near-Infrared Imager and Slitless Spectrograph instrument on the James Webb Space Telescope. These are the first space-based infrared interferometric observations of a Solar System body ever taken. For complex extended objects like Io, the traditional visibility extraction algorithms from interferograms suffer from limitations. Here, new deconvolution methods based on Neural Networks allowed us to obtain reliable images from which a detailed analysis of the volcanically active surface of this moon was performed. Our study characterizes the loci and brightness of several unresolved volcanoes on the surface of Io, as well as the extended emission observed. We identified the brightest eruption (I_4.3um = 33 +/- 4.3 GW/um), referred to as V1, within an area to the North-East of Seth Patera (129.4 +/- 0.8 deg. W. Longitude, 1.5 +/- 0.7 deg. S. Latitude). Its projected speed (V_T = 86 +/- 34 m/s) is consistent with the rotational speed of Io. Additionally, six fainter volcanoes were identified and characterized. Complementary ground-based images, taken with the Keck II telescope, allowed us to benchmark the deconvolved Aperture Masking Interferometric images, showing consistency. Finally, we highlight the importance of characterizing Io's surface with long-term monitoring at high-angular resolution.

While pulsar timing array (PTA) collaborations have reported evidence for a stochastic gravitational wave background (GWB), the detection of continuous gravitational waves (GWs) from a confirmed supermassive black hole binary (SMBHB) would provide strong support for the SMBHB origin of GWB. In this study, we analyze continuous GWs from the SMBHB candidate 3C 66B, modeling the GWB as a common uncorrelated red noise. Using Bayesian methods, we perform targeted searches across two PTA data sets: Nanohertz Observatory for Gravitational Waves 15 years data set and the European Pulsar Timing Array DR2 full data set. We find no evidence of such signal in both data sets and then place upper limits on the amplitude of the signal and the chirp mass of the source. Additionally, we evaluate the case of a GWB characterized by Hellings-Downs correlations using a likelihood reweighting method, which consistently reconfirms the conclusion of non-detection.

To better distinguish the nature of $H_0$ and $S_8$ tensions, it is necessary to separate the effects of expansion and the growth of structure. The growth index $\gamma$ was identified as the single parameter that characterizes the growth of density fluctuations independently of the effects of cosmic expansion. Analyses performed with various cosmological datasets indicate that the growth index has to be larger than its theoretically predicted value in the $\Lambda$CDM model. Cosmological models based on $f(R)$ gravity theories have scale-dependent growth indices, whose values are even more at odds with the growth rate data. In this work, we evaluate the growth index in the $\gamma\delta$CDM model both theoretically and numerically. Although based on $f(R)$ gravity theory, we show through several analyses with different combinations of datasets that the growth index and growth rate in the $\gamma\delta$CDM model behave similarly to the $\Lambda$CDM and the $\omega$CDM models. When faced with cosmological data, we also demonstrate that the $\gamma\delta$CDM model fits better than the $\Lambda$CDM and the $\omega$CDM models.

The rate of stellar evolution can rarely be measured in real time. The fastest evolution (excluding event-driven evolution), where stars may evolve measurably over decades, is during the post-AGB phase. In this paper we provide direct evidence for such a case. A secular, linear, factor of ~2.5 increase is found in the strength of the [O III] lines relative to H-beta over an 130 year period in the young, well-known, low excitation planetary nebula IC 418. The increase is caused by the rising temperature of the central star. We use photo-ionization models to derive a model dependent heating rate for the central star in the range 15-42 K\/yr. These derived heating rates are very sensitive to the stellar mass, and yield a central-star mass of 0.560-0.583 solar masses. Initial-final mass relations based on the Miller-Bertolami models give a progenitor main-sequence mass of 1.25-1.55 solar masses. IC 418 is a carbon rich planetary nebula and its central star, HD 35914, has evolved from an AGB carbon star. This result shows that carbon star formation at solar metallicity extends to these low masses. This is lower than commonly assumed and suggests that post-AGB evolution may be slower than recent post-AGB models predict.

Cooling flows are observed in X-ray studies of the centres of cool core clusters, galaxy groups and individual elliptical galaxies. They are partly hidden from direct view by embedded cold gas so have been called Hidden Cooling Flows. X-ray spectra from the XMM RGS reveal emission from hot gas modified by photoelectric absorption by cold gas intrinsic to the flow. Here we present the spectral analysis of 6 more low redshift galaxy groups ranging from the nearest fossil group to 2 groups hosting bright radio sources. All reveal absorbed cooling flows. AGN feedback is ineffective in heating the inner cooling gas in groups and elliptical galaxies. We have extended the analysis to include 3 nearby spiral galaxies (the Sombrero, Whirlpool and Sculptor galaxies). They have similar absorbed soft X-ray spectra to elliptical galaxies and may also host cooling flows of 0.3 to 1.1\Msun/yr in their CircumGalactic Medium.

Exoplanets that reside close to their host stars, and therefore receive substantial amounts of X-ray and ultraviolet radiation, are prone to suffer from strong atmospheric escape. This can lead to the creation of an envelope of escaping gas along the planet's orbital trajectory, often referred to as a tail. When transiting in front of their host star, these tails can not only produce larger depths in the transit light curves, but also introduce significant asymmetries between ingress and egress. Using the publicly available software Harmonica, we present a method to model the light curves of transiting planets surrounded by extended envelopes of escaping gas, and subsequently infer the shape and size of the latter. We apply this method to the JWST NIRISS/SOSS observations of HAT-P-18b, which show pronounced helium tail features in its spectroscopic light curve of the metastable helium triplet at 10830 Å. Our model reveals that, in order to fit the observed light curve of HAT-P-18b, the planet must possess a trailing helium tail of $15.79^{+1.14}_{-1.05}$ planetary radii. We carry out injection-recovery tests to validate the effectiveness of the proposed methodology. We demonstrate that, with sufficient precision, we would be able to fit a multi-layer envelope to the data, which would provide insight into the relative radial variations in the opacity profile.

Elemental abundance diagnostics in the solar corona are crucial for understanding energy transport, plasma heating, and magnetic activity. Most earlier imaging-spectroscopic studies have relied on slit-based spectrometers, which offer high spectral resolution but are limited in spatiotemporal coverage and temperature diagnostics. In contrast, slitless spectrographs like the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) produce overlapping spatial-spectral data (overlappograms) to enable wide-field imaging spectroscopy with broader temperature coverage. However, extracting elemental abundances from overlappogram data remains inherently challenging due to spatial and spectral confusion. In this work, we present a proof-of-concept technique for elemental abundance diagnostics from overlappograms, demonstrating its feasibility with simulated MaGIXS-2 observations.

We present the third installment of the Alma Luminous Star (ALS) catalogue, aimed at creating the most comprehensive and clean sample of Galactic massive stars. This update extends the sample by adding approximately 2000 OB stars, incorporating astrometric and photometric data from the Gaia Data Release 3 (DR3) alongside spectroscopic information from the Galactic O-Star Catalog based on recent ground-based spectroscopic surveys. Rigorous astrometric corrections are applied to Gaia DR3 parallaxes, proper motions, and photometry, ensuring accurate distance estimates through a Bayesian method suited to this stellar population's spatial distribution in the Milky Way. We perform some comparative analyses highlighting the improved distance accuracy over previous versions, underscore the importance of precise spectral classifications with competing catalogues, and identify areas for improvement in Gaia DR3 effective temperature and extinction estimates for massive stars. We also address the challenges of having robust definitions for these objects. In addition, we explore the catalogue's ability to trace Galactic features such as spiral arms, spurs and OB associations (with some insights on the nature of Gould's Belt). Finally, we discuss the potential for further expanding the sample with upcoming surveys. This effort marks a significant advancement in the creation of a reliable census of Galactic massive stars, contributing to our understanding of the Milky Way's structure and star formation history. This catalogue should serve as a valuable reference for the massive star community, supporting research on stellar interiors, winds, stellar feedback, and other processes that make OB stars key to the evolution of galaxies.

Relativistic magnetic reconnection has been proposed as an important nonthermal particle acceleration (NTPA) mechanism that generates power-law spectra and high-energy emissions. Power-law particle spectra are in general characterized by three parameters: the power-law index, the high-energy cutoff, and the low-energy cutoff (i.e., the injection energy). Particle injection into the nonthermal power law, despite also being a critical step in the NTPA chain, has received considerably less attention than the subsequent acceleration to high energies. Open questions on particle injection that are important for both physical understanding and astronomical observations include how the upstream magnetization~$\sigma$ influences the injection energy and the contributions of the known injection mechanisms (i.e., direct acceleration by the reconnection electric field, Fermi kicks, and pickup acceleration) to the injected particle population. Using fully kinetic particle-in-cell simulations, we uncover these relationships by systematically measuring the injection energy and calculating the contributions of each acceleration mechanism to the total injected particle population. We also present a theoretical model to explain these results. Additionally, we compare 2D and 3D simulations to assess the impact of the flux-rope kink and drift-kink instability on particle injection. We conclude with comparisons to previous work and outlook for future work.

This work investigates the initial mass and chemical evolution history of the Gaia-Enceladus dwarf galaxy. We combine spectroscopic data from APOGEE with astrometric data from Gaia DR3 to identify Gaia-Enceladus candidate stars via a machine-learning pipeline using t-SNE and HDBSCAN. By focusing on kinematic and chemical parameters, especially $\mathrm{[Fe/H]}$, $\mathrm{[Mg/Fe]}$, $\mathrm{[Al/Fe]}$, and $\mathrm{[Mn/Fe]}$, we uncover a population of metal-poor, high-eccentricity stars that align with literature criteria for Gaia-Enceladus debris. We then apply the \textit{OMEGA+} chemical evolution model, incorporating MCMC fitting of the observed abundance trends in the $\mathrm{[Mg/Fe]\times[Fe/H]}$ plane. Our best-fitting model indicates a gas mass of $4.93_{-0.72}^{+0.32}\times10^9\,{M_{\odot}}$ for Gaia-Enceladus, placing it at the higher end of previously suggested mass ranges. The model scenario suggests a short star formation timescale, substantial outflows, and a rapid build-up of metals mainly driven by core-collapse supernovae, with a lesser contribution from Type~Ia supernovae. Comparison with observational data in other chemical planes (e.g., $\mathrm{[Mg/Mn]\times[Al/Fe]}$) supports this scenario, emphasizing a distinct evolution path relative to the Milky Way. Additionally, our results provide indirect evidence that star formation in Gaia-Enceladus likely ceased within the first 4 Gyr, consistent with earlier inferences of an early merger event. These findings highlight the power of chemical evolution modeling in reconstructing the origin and mass of ancient accreted systems. Overall, we show that Gaia-Enceladus, through a rapid star formation and strong outflows, contributed a significant fraction of the metal-poor stellar halo of the Milky Way.

The James Webb Space Telescope recently uncovered a population of massive black holes (BHs) in the first billion years after the Big Bang. Among these high-redshift BH candidates, observations have identified a class of active galactic nuclei candidates, dubbed Little Red Dots (LRDs), with extraordinarily compact gas reservoirs and peculiar spectral features. LRDs clearly emerge at redshift z<8 and their abundance declines by z<5. Recent theoretical studies have explored the link between LRDs and the formation of heavy BH seeds in the early Universe, such as direct-collapse BHs (DCBHs). Here we present results from preliminary runs for the MELIORA cosmological hydrodynamical simulations, where we implement an accurate model for DCBH formation, accounting for the Lyman-Werner radiation field and mass-inflow rates in the target host haloes. We aim to test whether or not DCBH formation could lead to systems resembling those hypothesized for LRDs. We find that the population of newly formed DCBHs in the simulations exhibits a steep decline at z<6, akin to the emergence of LRDs, primarily driven by reduced inflows. The birth of DCBHs is associated with a significant gas compaction event, followed by a phase of intense luminosity in the 200 Myr after their birth, and subsequently by the formation of the first PopIII stars in these very haloes. If these DCBHs nurseries are associated with LRDs, then it could explain their weak emission from X-rays and hot dust.

Low-latency gravitational-wave alerts provide the greater multi-messenger community with information about the candidate events detected by the International Gravitational-Wave Network (IGWN). Prompt release of data products such as the sky localization, false alarm rate (FAR), and $p_\mathrm{astro}$ values allow astronomers to make informed decisions on which candidate gravitational-wave events merit target of opportunity (ToO) follow-up. However, false alarms, often referred to as "glitches", where a gravitational-wave candidate, or trigger, is the result of terrestrial noise, are an inherent part of gravitational-wave searches. In addition, with the presence of multiple gravitational-wave searches, different searches may have varying assessments of the significance of a given trigger. As a complement to quantities such as $p_\mathrm{astro}$, we provide a Machine Learning (ML) based approach to determining whether candidate events are astrophysical or terrestrial in nature, specifically a classifier that utilizes information provided by multiple low-latency search pipelines in its feature space. This classifier has a performance an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.96 and accuracy of 0.90 on the Mock Data Challenge training set and an AUC of 0.93 and accuracy of 0.86 on events from the Advanced LIGO (aLIGO)'s and Advanced Virgo (AdVirgo)'s third observing run (O3).

$F(R)$ inflationary models are analyzed without the Weyl transformation to the Einstein frame. Sufficient conditions for existence of global inflationary attractors in $F(R)$ models are provided. Following that, the procedure for calculating inflationary observables completely in the original, Jordan, frame is given. The described procedure is used to analyze a new $F(R)$ inflationary model (a one-parameter deformation of the Starobinsky model), which is shown to provide predictions in good agreement with the recent ACT data.

We extended the once-in-a-lifetime encounter (OILE) model to stochastic interactions among neutrinos. As in the original OILE model, the new model reproduces the mean-field behavior of a dense neutrino gas for time $t\lesssim (\mu\gamma)^{-1}$, where $\mu$ measures the strength of the mean-field neutrino self-interaction potential and is proportional to the neutrino density, and the dimensionless "impact parameter" $\gamma$ is a measure of the change in the flavor quantum state of a neutrino during interaction with another neutrino when the wave packets of the two neutrinos overlap. As in the mean-field case, the OILE model with random neutrino velocities experiences kinetic flavor decoherence as the flavor quantum states of the neutrinos diverge from each other. Unlike the mean-field case, however, the OILE model has a "collision term" due to the quantum entanglement among neutrinos. For $\gamma\ll1$, this incoherent effect can drive the neutrinos into a quasi-steady state that is similar to the collective precession mode in a homogeneous and isotropic neutrino gas in the mean-field approximation. Subsequently, the collision term drives the neutrino gas adiabatically through different quasi-steady states and eventually to flavor equilibration. This process is an example of miscidynamic flavor evolution, with the mixing equilibria being the quasi-steady precession states.

Axionic dark matter can form structures known as miniclusters that host an axion star at their center. The axion star feeds on the host, and the axion star mass may grow beyond its stability limit, leading to a potential bosenova. Since a dilute axion star has a stable mass limit only when self-interaction is considered, we include axion self-interaction effects in this paper, and specify the condition for bosenova in the QCD axion and temperature-independent axion-like particle parameter spaces. We find that self-interaction may dominate the mass growth of the axion star. For a minicluster with a large initial overdensity, bosenova occurs in a large fraction of axion parameter space. For the QCD axion, bosenova occurs within the age of the Universe for miniclusters with an initial overdensity $\delta\gtrsim 100$.

The detection of gravitational waves (GWs) has opened a new window to explore the dark Universe. Ultralight dark matter (ULDM), an attractive candidate for dark matter, might induce monochromatic signals in gravitational-wave (GW) laser interferometers. However it is not clear how such signals are disentangled from the GWs emitted by galactic compact binaries. Here we initiate the investigation on the spectral split of monochromatic signals caused by detector's heliocentric motion in space and show the annual modulation can induce distinct structures in the spectral harmonics for GWs and ULDM, which would enable to clearly identify the nature of the signal. We show the physical parameters can be inferred with high precision using the Fisher matrix formalism. Our results provide a practical algorithm for probing ULDM and broaden the scientific objectives of future GW detectors in space, such as LISA and Taiji.

Radio pulses generated by cosmic-ray air showers can be used to reconstruct key properties like the energy and depth of the electromagnetic component of cosmic-ray air showers. Radio detection threshold, influenced by natural and anthropogenic radio background, can be reduced through various techniques. In this work, we demonstrate that convolutional neural networks (CNNs) are an effective way to lower the threshold. We developed two CNNs: a classifier to distinguish radio signal waveforms from background noise and a denoiser to clean contaminated radio signals. Following the training and testing phases, we applied the networks to air-shower data triggered by scintillation detectors of the prototype station for the enhancement of IceTop, IceCube's surface array at the South Pole. Over a four-month period, we identified 554 cosmic-ray events in coincidence with IceTop, approximately five times more compared to a reference method based on a cut on the signal-to-noise ratio. Comparisons with IceTop measurements of the same air showers confirmed that the CNNs reliably identified cosmic-ray radio pulses and outperformed the reference method. Additionally, we find that CNNs reduce the false-positive rate of air-shower candidates and effectively denoise radio waveforms, thereby improving the accuracy of the power and arrival time reconstruction of radio pulses.

The scotogenic model provides a minimal and elegant framework that simultaneously explains neutrino masses and accommodates a viable dark matter (DM) candidate. In this work, we investigate the phenomenology of fermionic DM in the scotogenic model, with a particular emphasis on the effects of a non-standard cosmological history characterized by a low reheating temperature. We demonstrate that entropy injection from inflaton decay can significantly dilute the DM abundance, thereby relaxing the annihilation cross section required to reproduce the observed relic density and opening new regions of viable parameter space. We further analyze the complementarity between current and future direct detection experiments and charged lepton flavour violation (cLFV) searches in probing this scenario. Our results show that next-generation direct detection experiments such as DARWIN and XLZD, together with upcoming cLFV searches (in particular the future sensitivity of $\mu \rightarrow 3e$ experiments), will be capable of testing substantial regions of the parameter space, including those associated with low reheating temperatures.

We extend the modified Nambu-Jona-Lasinio (NJL) model -- incorporating exchange interactions via the Fierz transformation -- to finite temperatures in both two- and three-flavor scenarios, and investigate the properties of protoquark stars in $\beta$-equilibrium. Our results show that increasing the strength of exchange interactions, characterized by the parameter $\alpha$, changes the chiral phase transition from first-order to crossover. We examine the effects of finite temperature, lepton fraction, and exchange interactions on the equation of state (EOS), finding that the EOS in the crossover regime is significantly stiffer than in the first-order case. In certain regions of parameter space within the crossover scenario, strange quark matter can support the existence of twin star configurations.

Eccentric compact binary coalescences (CBCs) are expected to be observed in current and future gravitational-wave (GW) detector networks. However, it has been recently pointed out that a number of other physical and beyond-GR effects, could imitate, or be mimicked by, eccentric CBCs. In this work, we propose a conceptually simple but powerful method to directly confirm or reject the eccentric hypothesis, without needing to compare the hypothesis with the plethora of other possible hypotheses. The key idea is that while spurious non-zero values of eccentricity, at some reference frequency, could be acquired when a non-eccentric CBC with additional physical/beyond-GR effects is recovered with an eccentric CBC waveform model, the {\it evolution} of eccentricity with frequency will in general not be mimicked. We accordingly formulate an eccentricity evolution consistency test (EECT). The method compares the eccentricity recovered at some low frequency value (e.g, $10$ Hz), evolved to higher frequencies assuming GR, with eccentricities recovered at those same higher frequencies. Discrepancy between the two eccentricities at any reference frequency would violate EECT and indicate the presence of a mimicker. As a proof of concept, assuming a few eccentric CBC systems, quasi-circular CBCs with additional physics mimicking eccentricity, and an O4-like three-detector-network configuration, we demonstrate that our proposed method is indeed able to reject mimickers at $\geq 68\%$ confidence, while ensuring that truly eccentric CBCs satisfy EECT.