The high-redshift progenitors of present-day galaxy clusters are believed to substantially contribute to the global star-formation rate density and drive the large-scale reionization of the Universe. Here we present a blind and unbiased search for and characterization of galaxy overdensities during the reionization epoch at redshifts $z\sim 5.5-7$, based on rest-frame optical JWST/NIRCam grism spectroscopy of the Abell\,2744 lensing field as part of the JWST-ALT survey. Using a physically-motivated, cosmological inference Friends-of-Friends (FoF) algorithm, we identify six galaxy overdensities, including five robust systems at $z=5.66$ to $6.77$. They are all characterized by total halo masses $M_{\rm halo} \gtrsim 10^{11}\,M_{\odot}$ inferred from a range of proxies. We find that the galaxy members in these overdense environments are on average less massive though equally metal-rich, and generally comprised of younger stellar populations as indicated from their bluer spectral slopes less prominent Balmer breaks, than field galaxies at similar redshifts. Further, we use this novel rest-frame optical selection of galaxy proto-clusters to infer the fraction and 3D distribution of strong Lyman-$α$ emitters (LAEs) and damped Lyman-$α$ absorbers (DLAs) in the overdensity environments. We find that two out of six galaxy overdensities have excess \hi\ absorption compared to the field-average, while the other four are consistent within their large scatter in density. These results present the first direct observational constraints on the tomography of the dense, neutral gas reservoirs in large-scale galaxy overdensities at $z>5$ and highlight the limitations of pre-JWST searches for reionization-era galaxy overdensities relying on the detection of strong LAEs alone.[Abridged]

Low-mass or dwarf galaxies (M$_{\ast}<10^{9}$ M${\odot}$) are abundant in the Universe, yet their formation and evolution remain poorly understood. Their enhanced sensitivity to feedback from star formation and active galactic nuclei (AGN) make them excellent laboratories to test whether feedback prescriptions in cosmological simulations accurately reproduce their interstellar medium (ISM) properties. We present JWST/NIRCam and MIRI imaging of nine dwarf galaxies from COSMOS-Web survey at redshift $z<0.08$, with star formation rates ranging from 0.003-0.3 M${\odot}$ yr$^{-1}$ and stellar masses of log M$_{\ast}\sim8-9$ M$_{\odot}$. The detection rate with both NIRCam and MIRI is 100\%, indicating that these dwarfs possess substantial ISM content. The detected sample includes a roughly equal mix of early-type and late-type dwarfs, suggesting that it is representative of the broader dwarf galaxy population in low-density environments. We find that the observed MIRI flux distributions are comparable to forward-modelled flux distributions of mass-matched simulated galaxies in TNG50. We further conduct a multi-wavelength morphological analysis complementing the JWST NIRCam and MIRI imaging with archival HST/ACS data, employing the CAS (concentration, asymmetry, smoothness) framework. Among the multi-wavelength images, MIRI exhibits the largest variation in CAS parameters, likely due to dust lanes and clumps in several galaxies, also suggested by Spectral Energy Distribution (SED) fitting. This suggests that the dust content in these systems may be higher than those implied by rest-frame optical or near-infrared observations alone. Upcoming UV/optical and mid-infrared spectroscopic follow-up will be critical for constraining the gas kinematics and dust grain properties of dwarf galaxies in low-density environments such as COSMOS.

We explore how the fraction of red (quenched) galaxies varies in the dwarf galaxy regime (10^7 MSun < Mstar < 10^9.5 MSun), using a mass-complete sample of ~5900 dwarfs at z<0.15, constructed using deep multi-wavelength data in the COSMOS field. The red fraction decreases steadily until Mstar ~ 10^8.5 MSun and then increases again towards lower stellar masses. This 'U' shape demonstrates that the traditional notion of 'downsizing' (i.e. that progressively lower mass galaxies maintain star formation until later epochs) is incorrect -- downsizing does not continue uninterrupted into the dwarf regime. The U shape persists regardless of environment, indicating that it is driven by internal processes rather than external environment-driven mechanisms. Our results suggest that, at Mstar < 10^8 MSun, the quenching of star formation is dominated by supernova (SN) feedback and becomes more effective with decreasing stellar mass, as the potential well becomes shallower. At Mstar > 10^9 MSun, the quenching is driven by a mix of SN feedback and AGN feedback (which becomes more effective with increasing stellar mass, as central black holes become more massive). The processes that quench star formation are least effective in the range 10^8 MSun < Mstar < 10^9 MSun, likely because the potential well is deep enough to weaken the impact of SN feedback, while the effect of AGN feedback is still insignificant. The cosmological simulations tested here do not match the details of how the red fraction varies as a function of stellar mass -- we propose that the red fraction vs stellar mass relation (particularly in the dwarf regime) is a powerful calibrator for the processes that regulate star formation in galaxy formation models.

Type Ia Supernovae (SNe Ia) are well known for their role as standardizable cosmological candles. Their uniformity is credited to their single origin as thermonuclear explosions of White dwarf (WD) stars. Nevertheless, some SNe Ia break this regularity. Prominently, the Iax subclass are less energetic and remarkably diverse, raising questions about their progenitor systems. While no progenitor system of a normal SN Ia has ever been detected, a luminous blue star was identified in pre-explosion images of the site of the bright SN Iax SN 2012Z, suggested to be a helium giant companion star acting as a mass donor to a WD SN progenitor. This is in line with models of weak mass accretion of a WD from a binary companion, producing an explosion that does not fully disrupt the star. However, these models fail to explain the properties of the faintest Type Iax explosions, suggesting either they originate from other WD binary systems, or even from massive progenitor stars. Here, we present the faint SN Iax SN 2024vjm - possibly the faintest supernova observed to date. Using a deep pre-explosion image taken by the recently launched Euclid space mission, we show that its progenitor system must be fainter than the helium giant SN Iax progenitor candidate of SN 2012Z, as well as that of the luminous red companion or remnant of the faint SN 2008ha, and may require a subdwarf helium star as a mass donor. The deep image also provides strong arguments against a massive star origin for this faint supernova. Our observations argue that SN 2024vjm is a WD explosion, but we find that remarkably faint SNe Iax fade more slowly than bright ones, i.e., they evolve in an opposite manner from the famous Phillips relation that makes regular SNe Ia cosmological candles.

Polarimetric interferometry is a powerful tool for probing both black hole accretion physics and the background spacetime. Current models aimed at explaining the observed multiwavelength flares in Sgr A* often assume hotspots moving on geodesic, Keplerian orbits. In many scenarios, though, a hotspot may instead follow an inspiraling trajectory, potentially transitioning into a plunge toward the black hole. In this work, we present a general framework to simulate the polarized emission from generic equatorial inspiraling hotspots in Kerr spacetime using a parametric four-velocity profile. This parametrization defines a continuous family of flows, ranging from Cunningham's disk model (fixed radius orbits outside the innermost stable circular orbit and plunging motion within the innermost stable circular orbit) to purely radial motion, thereby extending the standard assumptions. Within this framework, we show that inspiral motion produces a distinctive observational signature: a precessing, unwinding evolution of the polarimetric Stokes Q-U looping pattern, in sharp contrast with the closed Q-U loops associated with stable orbits at a fixed radius. We then explore how the morphology of these signatures depends on black hole spin, observer inclination, and magnetic-field configuration. The presented model can be applied to current and near-future interferometric observations of linear polarization, offering a new avenue to probe the physics of matter spiraling inward and the relativistic velocities of plunging plasma.

Here we analyse the growth and feedback effects of massive black holes (MBHs) in the SEEDZ simulations. The most massive black holes grow to masses of $\sim10^{6}$ M$_\odot$ by $z=12.5$ during short bursts of super-Eddington accretion, sustained over a period of 5-30 Myr. We find that the determining factor that cuts off this initial growth is feedback from the MBH itself, rather than nearby supernovae or exhausting the available gas reservoir. Our simulations show that for the most actively accreting MBHs, feedback completely evacuates the gas from the host halo and ejects it into the inter-galactic medium. Despite implementing a relatively weak feedback model, the energy injected into the gas surrounding the MBH exceeds the binding energy of the halo. These results either indicate that MBH feedback in the early ($Λ$CDM) Universe is much weaker than previously assumed, or that at least some of the high redshift galaxies we currently observe with JWST formed via a two-step process, whereby a MBH initially quenches its host galaxy and later reconstitutes its baryonic reservoir, either through mergers with gas rich galaxies or from accretion from the cosmic web. Moreover, the maximum black hole masses that emerge in SEEDZ are effectively set by a combination of MBH feedback modelling and the binding potential of the host halo. Unless feedback is extremely ineffective at early times (for example if growth is merger dominated rather than accretion dominated or feedback is contained close to the MBH) then the maximum mass of black holes at redshift before 12.5 should not significantly exceed $10^6$ M$_\odot$.

Supersoft X-ray sources (SSSs) host white dwarfs (WDs) accreting at rates that sustain steady nuclear burning, driving rapid mass growth, radial contraction, and magnetic field amplification. Angular-momentum transfer from the accretion disk naturally spins up the WD, while the amplified internal magnetic field induces a non-axisymmetric deformation in presence of a misaligned rotation. Such WDs emits continuous gravitational waves (CGWs). We model the coupled evolutions of stellar mass, spin, and magnetic structure in accreting WDs in SSSs with \texttt{MESA}, and compute the resulting quadrupolar deformation with the Einstein-Maxwell solver \texttt{XNS}. We show that WDs in SSSs, particularly near the end ofthermal timescale mass transfer and close to the Chandrasekhar mass limit, produce CGWs predominantly in the deci-Hz band accessible to planned detectors such as DECIGO, BBO, Deci-Hz, ALIA, and LGWA, and are distinguishable from other Galactic CGW sources such as AM\,CVn systems, detached double WDs, and isolated WDs. Well-studied SSSs such as CAL~83 and RX~J0019+2156 can be detectable, enabling targeted CGW measurements that directly probe WD's internal magnetic fields and rotation, while blind searches can reveal hundreds of obscured SSSs otherwise missed in soft X-rays and map the hidden population of accreting, rapidly rotating, magnetized WDs in nearby galaxies. A CGW detection from WDs in SSSs could also identify potential pre-explosion Type~Ia progenitors.

Since 2004, the Keck Observatory Archive (KOA) has operated as a NASA-funded collaboration between the NASA Exoplanet Science Institute ( NExScI) and the W.M. Keck Observatory. It ingests and serves all data acquired by the twin 10-meter Keck telescopes on Mauna Kea, Hawaii. In the past three years, KOA has begun a modernization program to replace the architecture and systems used since the archive's creation with a new modern Python-based infrastructure. This infrastructure will position KOA to respond to the rapid growth of new and complex data sets that will be acquired by new instruments now in development, and enable follow-up to identify the deluge of alerts of transient sources expected by new survey telescopes such as the Vera C. Rubin Observatory. Since 2022, KOA has ingested new data in near-real time, generally within one minute of creation, and has made them immediately accessible to observers through a dedicated web interface. The archive is now deploying a new, scalable, Python-based, VO-compliant query infrastructure built with the Plotly-Dash framework and R-tree indices to speed-up queries by a factor of 20. The project described here exploits the new query infrastructure to develop a dashboard that will return live metrics on the performance and growth of the archive. These metrics assess the current health of the archive and guide planning future hardware and software upgrades. This single dashboard will enable, for example, monitoring of real-time ingestion, as well as studying the long-term growth of the archive. Current methods of gathering metrics that have been in place since the archive opened will not support the archive as it continues to scale. These methods suffer from high latency, are not optimized for on-demand metrics, are scattered among various tools, and are cumbersome to use.

We present Keck/NIRSPEC $K$-band observations of HD 80606 b, one of the most eccentric known exoplanets. HD 80606 b was observed after secondary eclipse, close to periastron, when the planet passes within 0.03 AU of HD 80606 and the rapid heating of the atmosphere may lead to extreme chemical changes and a temporary thermal inversion. The rapid change in the planetary radial velocity near periastron is sufficient to enable high-resolution cross-correlation spectroscopy (HRCCS) analysis, which produces a tentative detection ($\rm SNR\sim4$) of HD 80606 b. Injection-recovery tests appear to reject strong thermal inversions near periastron, consistent with recent results from JWST. We also perform atmospheric retrievals with free parameters for the Pressure-Temperature ($P-T$) profile and with a profile matched to the JWST results, which suggest the presence of absorption features from CH$_4$ and CO. While HD 80606 b is not definitively detected in these data, these results are consistent with JWST observations, which found the post-eclipse atmosphere of HD 80606 b shows weak absorption features from these species. Future observations with higher spectral resolution and/or wider wavelength coverage are needed for a confident atmospheric detection of HD 80606 b via high-resolution spectroscopy alone, but such observations are a challenge to schedule due to the 111-day orbital period.

The Spectro Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) is conducting the first all-sky near infrared spectral survey spanning 0.75 to 5.0um with resolving power R~35 to 130. Linear variable filters mounted in front of six H2RG detectors produce a position dependent spectral response across the focal plane. This paper presents the ground-based spectral calibration of SPHEREx, including the cryogenic apparatus, optical configuration, measurement strategy, analysis pipeline, and resulting calibration products. Monochromatic wavelength scans are used to derive the spectral response function, band center, and resolving power for every pixel. Band centers are measured to better than 1nm for Bands 1 through 4 (0.75 to 3.82um) and better than 10nm for Bands 5 and 6 (3.82 to 5.0um). Out-of-band leakage is negligible for detectors above 1.64um and is present at the percent level below this wavelength. The resolving power is measured to within 5% and agrees with design expectations to within 10%. An on-sky spectrum of the Cat's Eye Nebula (NGC 6543) constructed from repeated observations provides in-flight verification and shows agreement between ground calibrated response and astrophysical emission features. Calibration products, including per-pixel band center and resolving power maps, are released through IPAC to support community use of SPHEREx data. The absolute spectral calibration will continue to improve through in-flight measurements, with further reductions in uncertainty expected for the longest-wavelength bands.

We investigate the feasibility and scientific potential of the Cosmic Positioning System (CPS), a space mission concept enabling purely geometric distance measurements to sources at hundreds of megaparsecs by directly detecting electromagnetic wavefront curvature. CPS consists of a constellation of radio antennas distributed across the outer Solar System, operating on baselines of tens of astronomical units. By precisely timing the arrival of repeating fast radio bursts (FRBs), CPS infers source distances via trilateration -- analogous to global navigation satellite systems such as GPS but on cosmological scales. We show that CPS distance measurements could result in sub-percent constraints on the Hubble constant with even a handful of detections, whereas we predict that 10-100 FRB sources are likely visible. We evaluate dominant sources of uncertainty -- wavefront timing precision, interstellar refractive delays, spacecraft positional knowledge, and onboard clock stability -- finding these controllable at required levels using near-term technologies. Our nominal design employs five spacecraft with 8 m deployable antennas, 3-6 GHz receivers with sub-30 K system temperatures, and space-qualified atomic clocks similar to those on GPS satellites, supported by a ground network for ranging calibration and FRB alerts. Beyond cosmic expansion, CPS may enable frontier measurements in astrophysics and fundamental physics, including constraints on small-scale dark matter structure, microhertz gravitational waves (bridging pulsar timing arrays and LISA), and the outer Solar System mass distribution. The most significant viability issue concerns FRB properties at several-GHz frequencies; we recommend observational campaigns to characterize repeating FRBs in this band.

Y dwarfs represent the coldest class of brown dwarfs, with effective temperatures below 500K, and provide unique analogues to cold giant exoplanets. We present a large compilation of uniform near-infrared photometry from the Hubble Space Telescope for 21 Y dwarfs across multiple WFC3/IR filters, including the F105W, F125W and F160W bands. We employed refined PSF-fitting and calibration procedures to reach photometric uncertainties at the 0.02-0.05 mag level for most targets. Combined with precise parallax measurements, our data reveal well-defined Y-dwarf sequences in near-infrared colour-magnitude diagrams, observed with a markedly improved tightness. Known photometric trends emerge with minimal scatter, including the continuous redward progression in F125W-F160W with decreasing temperature, and the blueward trend in F105W-F125W with possible hints of a reversal around 350K. Comparisons to the ATMO, Sonora Elf Owl, and Lacy & Burrows atmospheric models highlight systematic discrepancies, in particular F105W-F125W and F105W-F160W colours predicted to be too red. Low-metallicity grids provide the best fits to the global Y-dwarf population, although closer inspection across wavelengths shows that these preferences likely reflect compensating effects in missing or incomplete physics rather than true population-level abundances. While some atmospheric diversity is expected among Y dwarfs, their tight observational sequences and systematic offsets from model predictions reveal that key physical and chemical processes remain inadequately captured in current grids. Our results underscore the importance of high-precision, internally consistent datasets in robustly tracing the Y-dwarf cooling sequence and providing the empirical constraints needed to advance theoretical models at the lowest temperatures.

Radio-quiet narrow-line Seyfert 1 galaxies (RQ-NLSy1s) are generally considered to be dominated by thermal emission from the accretion disk. However, recurring 37 GHz radio flares detected from seven RQ-NLSy1s by the Metsahovi Radio Observatory suggest that non-thermal processes may also contribute to their emission. We present a systematic optical and mid-infrared (MIR) variability study combined with broadband SED modeling to investigate the origin of their flux variations and assess the relative contributions of accretion disk and possible jet-related components. High-cadence optical light curves in the g, r, and i bands were obtained from ZTF, while long-term MIR light curves in the W1 and W2 bands were taken from WISE. Optical variability was quantified using the FAGN-test, peak-to-peak variability amplitude, and fractional variability, while MIR variability was characterized using redshift-corrected intrinsic variability amplitudes. Optical variability was examined from intra-night to long-term timescales, and MIR variability on long-term timescales. All RQ-NLSy1s show statistically significant long-term optical variability, with amplitudes increasing toward shorter wavelengths. Three sources exhibit bluer-when-brighter trends and increasing variability amplitudes across the optical bands, indicating a non-thermal contribution. Intrinsic MIR variability is detected in three of the four sources. Significant optical-MIR and MIR intra-band lags are observed, while optical intra-band lags are insignificant. Optical variability amplitudes are anti-correlated with the Eddington ratio and positively correlated with black hole mass. These results suggest that a subset of RQ-NLSy1s hosts weak or intermittent jets contributing to their optical and MIR emission, supported by SED modeling. Coordinated multi-wavelength monitoring is required to better constrain the origin of these variations.

We present a comparative analysis of supernova remnant Cassiopeia A based on two deep, narrow-band images covering the [Fe II] 1.644um + [Si I] 1.645um lines obtained in 2013 and 2020 with the same instruments on the UKIRT 3.8m telescope. The identical setup and observing procedure allow for direct, accurate measurements of morphological and kinematic changes over a seven-year baseline. We identified 263 compact knots in the 2020 image and, through comparison with the 2013 catalog of Koo et al. 2018 (arXiv:1809.07935), classified them into quasi-stationary circumstellar knots and fast-moving knots (FMKs) of supernova ejecta. The FMKs show significant flux fluctuations, and many of those detected in 2013 are absent in the 2020 image. Proper-motion measurements derived from cross-correlation analysis indicate that most FMKs follow nearly ballistic expansion, whereas some, particularly those just beyond the eastern Fe-rich, X-ray emitting ejecta region, exhibit noticeable deceleration. The proper motions of the main ejecta shell were also measured and modeled as a uniformly expanding shell with a systemic motion, which reproduces the observed geometric and kinematic asymmetries of the remnant.

Interstellar dust plays a crucial role in gas cooling and molecule formation, influencing galaxy evolution. However, the composition and structure of dust in distant galaxies are still poorly understood. We have started a JWST MIRI MRS program investigating the dust features in gas-rich and dusty galaxies at redshifts $z<$1.2, with strong 2175~Å bumps detected in absorption along the lines of sight to distant background quasars. Here we describe our program strategy, and present MIRI MRS observations of IR dust features at $z=0.5-1.2$ in five quasar spectra that form the first part of our full sample. We identify artifacts in MIRI MRS data that affect the background in IFU cubes, and propose methods to reduce their effects. We pay special attention to modeling the quasar mid-IR continuum, which shows significant variation depending on AGN morphology, redshift, and black hole mass. Dust in foreground galaxies produces significant absorption from the 10~$μ$m silicate feature in all five quasar spectra. Compared with the average 10~$μ$m silicate feature in the diffuse ISM of the Milky Way, we find differences in the absorption peak position, width of the features, and asymmetry of the profiles. A detailed study of these silicate features is presented in our next paper (Klimenko et al. 2026b). In two quasar spectra, we tentatively detect weak IR features near 3.0 and 3.4~$μ$m. Their strengths are comparable to those seen in the Milky Way ISM, but follow-up observations are required to confirm these detections.

A study of the unbalanced magnetic polarity distribution of 70 coronal holes was performed. Data from the Helioseismic and Magnetic Imager (HMI) were used to examine the photospheric line-of-sight magnetic field ($B_{\mathrm{LOS}}$) beneath these coronal holes. The skewness ($S$) values of the $B_{\mathrm{LOS}}$ distributions revealed significant asymmetry, characterized by the dominance of one magnetic polarity, with $\sim88\%$ of the coronal holes exhibiting a skewness value ranging from $\pm(0.20~\text{to}~0.40)$. The corresponding magnetic flux imbalance ($Φ_{\mathrm{imb}}$) ranges from $20\%$ to $45\%$. In contrast, quiet-Sun regions show symmetric magnetic field distributions with skewness values less than$~0.11$ and flux imbalance less than $11.0\%$. A study of a coronal hole as it traverses across the disk shows that the magnetic field distribution does not evolve significantly over this time, remaining stable across half a solar rotation. A moderate correlation ($r = 0.60$) between the magnetic flux imbalance and the speed of associated high speed solar wind streams ($v_{\mathrm{HSS}}$) suggests that flux imbalance may contribute to the generation of these faster solar wind streams. These results imply that regions with higher flux imbalance ($Φ_{\mathrm{imb}}$), indicative of more open magnetic field structures, present more favorable conditions for plasma acceleration as compared to closed bi-polar field, but the moderate correlation indicates that other factors may also play important roles.

Intermediate mass black holes (IMBHs) formed in active galactic nucleus (AGN) disks are expected to inspiral into their central supermassive black holes (SMBHs), generating a stochastic gravitational-wave (GW) background in the mHz--decihertz band. Using the population-agnostic energetic formalism, we treat the AGN-disk channel as a mass-flow pipeline connecting the stellar-mass black hole population observed by LIGO/Virgo/KAGRA (LVK) to the SMBH mass reservoir via IMBHs. By anchoring this estimate to the LVK merger rate densities and the cosmic SMBH mass density derived from scaling relations, we derive a limit on the background amplitude. We show that the total energy density of the background is bounded by the global mass budget of SMBH growth. For fiducial parameters consistent with the fourth Gravitational-Wave Transient Catalog (GWTC-4), this yields a characteristic strain $A_{\rm IMR} \simeq (1.2_{-0.2}^{+0.2})\times 10^{-21}$ at $3\,{\rm mHz}$. While this fiducial amplitude is subdominant to the Galactic white dwarf foreground and the stellar-mass Extreme Mass Ratio Inspiral (EMRI) background, we show it can be distinguished by its non-Gaussian statistics and higher frequency cutoff. This new background may be detectable in the decihertz band where proposed detectors such as the Big Bang Observer or long-baseline lunar interferometers can measure it cleanly. A detection would provide a direct, model-independent constraint on the efficiency with which AGN disks process stellar remnants into SMBH mass growth, linking the LVK and LISA bands.

Modern telescopes generate increasingly large and diverse datasets, often consisting of complex and morphologically rich structures. To efficiently explore such data requires automated methods that can extract and organize physically meaningful information, ideally without the need for extensive manual interaction. We aim to provide a user-friendly implementation of a self-supervised machine learning framework to explore morphological properties of large datasets, based on the BYOL (Bootstrap Your Own Latents) method. By enabling the generation of meaningful image embeddings without manually labelled data, the framework will enable key tasks such as clustering, anomaly detection, and similarity based exploration. In contrast to existing BYOL implementations, astromorph accommodates data of varying dimensions and resolutions, including both single-channel FITS images and multi-channel spectral cubes. The package is built with usability in mind, offering streamlined pipeline scripts for ease of use as well as deeper customization options via PyTorch-based classes. To demonstrate the utility of astromorph, we apply it in two contrasting science cases representing different astronomical domains: images of protoplanetary disks observed with ALMA, and infrared dark clouds observed with Spitzer and Herschel. In both cases, we demonstrate how astromorph produces scientifically meaningful embeddings that capture morphological differences and similarities across large samples. astromorph enables users to apply a robust, label-free approach for uncovering morphological patterns in astronomical datasets. The successful application to two markedly different datasets suggest that the pipeline is broadly applicable across a wide range of imaging-rich astronomical context, providing a user friendly tool for advancing discovery in observational astronomy.

Starspots and their movements on stellar surfaces enable investigating the mechanisms of stellar magnetic activity. Information on the spot distribution and differential rotation provide important constraints for the behaviour of stellar magnetic dynamos. We analyse the Kepler photometry of Kepler-411, a known exoplanet host, to determine the distribution and properties of star spots on the stellar surface with two independent and complementary methods: modelling the photometric effect of rotation of spots on the stellar surface and mapping of spots by transiting planets. By constructing a spot model accounting for geometry, differential rotation and spot evolution, we model the spots of the stellar surface giving rise to the observed brightness variations. We also search for evidence for occultations of starspots in high-cadence photometry. Our spot models reproduce the observed photometric variations well and we are able to obtain information on the distribution and movement of spots on the stellar surface. We do not obtain evidence for differential rotation -- the rotational profile is consistent with rigid-body rotation with a period of 10.52$\pm$0.34 days. We detect three occultations of spots by planet c. The positions of these spots coincide well with the positions of larger spot structures identified by our modelling of the rotational modulation of the light curve.

Cosmological constraints using weak gravitational lensing measurements from the Roman Space Telescope will require a powerful method for modelling uncertainties in the galaxy redshift distribution. In this work, we use an optimized version of the principal component analysis (PCA) to model uncertainties in the full shape of the redshift distributions, a method proposed by \cite{pca_method} and recently used in the Dark Energy Survey Y6 analysis. Here, we implement this new approach within the Roman High Latitude Imaging Survey (HLIS) Cosmology Project Infrastructure Team (PIT) pipeline, namely Cobaya-Cosmolike Joint Architecture (\texttt{CoCoA}). To validate the PCA in mitigating biases on cosmological parameters, $S_8$ and $Ω_m$, we use a set of redshift distributions from \texttt{Cardinal} generated for a variety of Roman configurations. Overall, when the simulated cosmic shear data vector is not strongly miscalibrated relative to the fiducial one, both the mean-shift and the PCA-based approaches produce consistent cosmological constraints when marginalizing over nuisance parameters. For mild to strong miscalibration, including additional PCs progressively mitigates biases in $S_8$ and $Ω_m$, and can achieve comparable performance with fewer parameters than the nine tomographic-bin mean-shift model.

We report the discovery of the first transient relativistic iron Kα line in an Active Galactic Nucleus (AGN) J1047+5907. The line was detected 21.5 days (rest-frame) after an X-ray coronal flare observed in 2008 and it exhibits significant broadening consistent with relativistic reflection from the accretion disk in the vicinity of the central supermassive black hole (SMBH). The line has a width of ~300 eV, corresponding to a Keplerian velocity of 14,000 km s-1, at a distance of 5-41 light-days from the SMBH, strongly implying that the observed coronal flare triggered the emergence of the line. This event provides rare direct evidence of the response of the accretion disk to impulsive coronal illumination and offers a new method to probe the SMBH and disk physics. The relativistic modeling favors a broadened line produced by distant reflection from an accretion disk around a rapidly spinning black hole viewed at an intermediate inclination, consistent with other observations. Systematic monitoring of type 1 AGN following strong X-ray flares may open a new observational window into the innermost regions of AGN, enabling constraints on the physics of SMBH and its accretion disk at different radii that are otherwise challenging to access.

The MONDian theory of AQUAL (AQUAdratic Lagrangian) and the theory of GRAS (GRavitational Anti-Screening) are alternatives to the theory of dark matter. When these theories are applied to galaxy dynamics they are in excellent agreement with observations including the galactic RAR (Radial Acceleration Relationship). However, when applied to galaxy clusters they do not explain the bulk of the missing mass. This manuscript develops a modified version of the GRAS/AQUAL field equation that can be extended to galaxy clusters. It involves just a single free parameter. The new field equation is then applied to a sample of galaxy clusters and checked against modeled galaxies and solar system constraints. Further to this, the modified field equation leads to an understanding of the difference between the galactic RAR and the RAR recently found for clusters.

We present ALMA [\ion{C}{1}]~$^3P_1$--$^3P_0$ imaging of the central $6.6\times4.2~\mathrm{pc}^2$ region of the Galaxy encompassing the circumnuclear disk (CND). The data reveal low-density ($n_\mathrm{H_2}\sim10^3~$cm$^{-3}$) molecular gas with inward motion, widespread both inside and outside the CND. The normalized [\ion{C}{1}] to CS~7--6 intensity difference decreases inwardly from $R=4$~pc to 1.7~pc and azimuthally along the CND's rotation, likely tracing paths of low-density gas inflow. By projecting spaxels into orbital coordinates assuming a velocity field model, we identify four kinematic features: a pair of spiral outer streamers toward the CND, inner streamers extending to 0.5~pc from Sgr~A$^*$, an outer disk at $ R\sim3$--6~pc, and the rotating ring at $R=2$~pc. $P$--$P$--$V$ correlation between the inner streamers and H42$α$ indicates gas supply to the mini-spiral through the western arc (WA) and northern arm (NA). The total inflowing mass is $1.5\times10^4~M_\odot$, 1.7 times the mass of the rotating ring. The identified flows can be organized into two main pathways connecting the CND exterior and interior: ''WA flow'' feeding the mini-spiral WA via the CND, and ''NA flow'' bypassing the purely rotating orbit. The inflow rate along the former is approximately constant (0.1--0.16~$M_\odot~\mathrm{yr}^{-1}$), implying a CND dwelling time comparable to its orbital period and supporting the CND's transient nature. We also identify two [\ion{C}{1}]-bright clumps (CBCs) lacking dense-gas counterparts near the contact point between the northern outer streamer and the CND. Apparently intact against tidal disruption despite subcritical densities, the CBCs may represent a chemically young phase shortly after formation in colliding flows.

Collisions between stellar remnants and dark matter in the Galactic bulge are frequent, and the kinetic energy of a primordial black hole incident on a white dwarf, if it is all thermalized, will raise the degenerate core's temperature, by at least a degree in the case of a lunar mass black hole. This is an underestimate in two ways: the specific heat is less than 3k/2 per particle, and the incoming object is accelerated by gravitational focusing. Detailed physical models have recently been made of this triggering event. Present observational data are equivocal as to whether the radial distribution of type Ia supernovae in galaxies follows the starlight in the galaxies, or is more concentrated towards the center, as collisional triggering would suggest. But future samples of millions of supernovae from the Rubin telescope will change that.

The age of the rings and some of the moons of Saturn is an open question, and multiple lines of evidence point to a recent (few hundred Myr ago) cataclysm involving disruption of past moons. The main driver of the evolution of the Saturnian system is the relatively rapid tidal expansion of its largest moon, Titan, which is likely driven by resonant tides within Saturn. The obliquity of Saturn and the orbit of the small moon Hyperion both serve as a record of the past orbital evolution of Titan. Saturn's obliquity was likely generated by a secular spin-orbit resonance with the planets, while Hyperion is caught in a mean-motion resonance with Titan, with both phenomena driven by Titan's orbital expansion. We propose that the breaking of Saturn's spin resonance was also the event in which Hyperion formed, when an outer mid-sized satellite (''Proto-Hyperion'') was destabilized and collided with Titan, with some of the debris accreting into Hyperion. During the instability Proto-Hyperion's perturbations produced the observed orbital inclination of Iapetus. The same event also excited the eccentricity of Titan, which then, through Titan's resonant interaction with the inner moons, led to destabilization, collisional disruption and re-accretion of the inner moon system, including the rings. We present numerical integrations that show that this chain of events has a relatively high probability, and discuss how it fits within our knowledge of the Saturnian system.

Post-StarBurst (PSB) galaxies are galaxies that have undergone a large burst of star formation followed by rapid quenching. Understanding their properties as a population can help us better understand how galaxies evolve to quiescence. This project aims to use Star Formation History (SFH) measurements from the Integral Field Spectroscopy (IFS) surveys MaNGA, CALIFA, and AMUSING++ processed with the Pipe3D analysis pipeline in order to select PSB galaxies as well as PSB regions in galaxies. Most PSB selection methods use cutoffs determined by spectral features, but in this work we introduce a new PSB selection method based directly on the property we are most interested in; inferred SFHs. IFS data allows us to probe a galaxy's star formation on a spatially resolved scale, enabling us to examine the size, shape, and location of PSB regions within a galaxy. We select 107 PSB galaxies, only 7 of which are among known PSBs selected by other methods. Unlike traditional PSB selection methods, our approach is not biased against Active Galactic Nuclei (AGN). Despite this, we still find no evidence for a significant Seyfert 2 PSB population, suggesting that strong AGN activity is uncommon throughout the PSB phase. Our spatially-resolved SFH selection identifies a wide range of galaxies, including globally quiescent elliptical galaxies with centrally-concentrated PSB spaxels, galaxies with ring-like PSB spaxels and a preference for inside-out age gradients (contrary to what has previously been observed in the literature), and galaxies with widespread PSB regions that have significant star formation elsewhere in the galaxy.

Recurrent nova (RN) T Pyxidis (T Pyx) has a complex history of mass accreting-onto and ejection-from the white dwarf, with a classical nova eruption around 1866 kick-starting a RN-phase with six RN eruptions from 1890--2011. T Pyx is a primary progenitor candidate for Type Ia supernovae (SNIa). This is chiefly a question of whether the mass accreted by the white dwarf ($M_{\rm accreted}$) is more-or-less than the mass ejected by the nova eruptions ($M_{\rm ejecta}$) over the entire eruption cycle. Prior attempts to measure $M_{\rm ejecta}$ from the traditional methods have a scatter of $>$130$\times$, so only a new technique can provide a measure of adequate accuracy and reliability. This new technique is the timing experiment of measuring the orbital period from 1986 to 2025, where the period increased by $+$50.3$\pm$7.9 parts-per-million across the 2011 eruption. With simple and sure physics, the best estimate for the mass ejected by one RN event is $>$2400$\times$10$^{-7}$ M$_{\odot}$, with an extreme inviolate limit of $\gg$354$\times$10$^{-7}$ M$_{\odot}$. Over all eruptions in a cycle, $M_{ejecta}$$>$17120$\times$10$^{-7}$ M$_{\odot}$, with an inviolate limit of $M_{ejecta}$$\gg$2144$\times$10$^{-7}$ M$_{\odot}$. Over the full eruption cycle, the white dwarf accreted 220$\times$10$^{-7}$ M$_{\odot}$. So M$_{\rm ejecta}$$\gg$11.3$\times$M$_{\rm accreted}$, and T Pyx can never become a SNIa. This paper is the seventh in a series proving that each of various popular candidate SNIa progenitors cannot possibly evolve to a supernova; including V445 Pup, U Sco, T CrB, all symbiotic stars, FQ Cir, V1405 Cas, and now T Pyx.

Coronal mass ejections (CMEs) are a major driver of space weather as they propagate through the heliosphere. Many CMEs have associated prominence material entangled in their magnetic structure which contains cooler plasma. This cooler CME component contains significant amounts of neutral elements, which emit brightly in permitted atomic lines. It has been hypothesized that permitted transitions of neutral elements in eruptions could be used for inferring the magnetic field in CMEs, which is crucial for space weather forecasting. We present observations made with the Upgraded Coronal Multi-channel Polarimeter (UCoMP) in He I 1083 nm that clearly show the presence of neutral helium in eruptive prominences associated with CMEs as they propagate through the lower and middle corona. We find that solar prominence eruptions can be detected in He I 1083 nm observations up to the edge of the instrument field of view at about 2 solar radii, providing valuable spectral information that complements existing extreme ultraviolet and white-light coronal imaging observatories. These results illustrate the capability of UCoMP to probe the dynamic behavior of prominence eruptions, allowing for their line-of-sight velocity estimation, and potentially improving space weather forecasting by enabling earlier and more accurate identification of Earth-directed eruptions.

Thermonuclear (Type I ) X-ray bursts from accreting neutron stars offer a means to determine neutron-star (NS) mass ($M$) and radius ($R$) and thereby probe the properties of matter at supranuclear density. A subset of these events, photospheric radius-expansion (PRE) bursts, provide a particularly powerful tool to constrain the neutron-star $M$ and $R$. Here, we apply the direct cooling-tail method to 2S~0918$-$549, using a rare superexpansion burst observed by \emph{RXTE}. We fit only the post-touchdown data within \(F/F_{\rm td}\in[0.6,0.95]\), employing modern atmosphere models (pure He and metal-enriched). The pure-He atmosphere yields a good description of the cooling tail (\(χ^{2}/ν=18.12/14\)), whereas metal-rich models fail; information-criterion tests (AIC/BIC) disfavor adding a free absorption edge in every time bin, indicating that heavy-element ashes are unnecessary. The joint fit gives a distance \(d=4.1-5.3\) kpc and mass-radius constraints \(M=1-2\,M_\odot\) and \(R=9.7-11.9\) km (99\% confidence). These results suggest that representative families of both gravity-bound and self-bound equations of state remain viable at the $1σ$ confidence level.

A fundamental challenge in star formation is understanding how a protostar accretes mass from its circumstellar disk while removing excess angular momentum. Protostellar jets are widely invoked as the primary channels for angular momentum removal, yet the mechanism by which they are launched and extract angular momentum remains poorly constrained. Here we report high-resolution ALMA Band 7 (345 GHz) and Band 6 (230 GHz) observations of CO (3-2), CO (2-1), and SiO (5-4) emission from the protostar HOPS 10 (G209.55-19.68S2). The combined data trace both the entrained outflow and the collimated jet with excellent spatial and velocity resolution, revealing a uniquely monopolar protostellar jet, the clearest example reported to date. The system exhibits a distinctly unipolar high-velocity jet with velocity offsets of +44 to +66 km s-1, unlike the predominantly bipolar morphology characteristic of most protostellar jets. While the low-velocity outflow, with velocity offsets of -20 to +30 km s-1, is detected in both directions, the high-velocity jet appears only on one side, and this monopolarity is consistent across all tracers. Given the nearly edge-on geometry and low submillimeter extinction, comparable emission would normally be expected from both lobes. The shock tracer SiO emission confirms a genuine, highly collimated jet rather than cloud contamination, and no ambient structure is capable of obscuring a counterjet. We argue that intrinsically asymmetric mass loading along the disk magnetic field lines provides the most plausible explanation for the observed monopolarity.

With four giant planets ($m\sim5-10~M_{\rm Jup}$, $T_\rm{eff}\sim900-1200$ K) orbiting between 15-70 au, HR 8799 provides an unparalleled testbed for studying giant planet formation and probing compositional trends across the protoplanetary disk. We present new JWST/NIRSpec IFU observations ($2.85-5.3~μ$m, $R\approx2700$) that now include the spectrum of HR 8799 b, and higher S/N spectra for HR 8799 c, d, and e compared to that in Ruffio & Xuan et al. 2026. We detect CO, CH$_4$, H$_2$O, H$_2$S, CO$_2$, and for planet b, NH$_3$. We combine the NIRSpec spectra with $1-5 μ$m photometry to perform atmospheric retrievals that account for disequilibrium chemistry and clouds, and allow C/H, O/H, N/H, and S/H to scale independently. While the four planets are similarly enriched in carbon and oxygen, with C/H and O/H between $3-5\times$ stellar, we observe a tentative trend of increasing S/H - a tracer of refractory solids - from $2-5 \times$ stellar with increasing orbital distance. From HR 8799 b's NH$_3$ abundance, we estimate $\rm N/H=21.2^{+16.2}_{-8.8}\times$ stellar, suggesting the outer planet accreted significant amounts of N-rich gas. Overall, the elemental abundance patterns we observe are consistent with a picture where planet b formed between the CO snowline and the more-distant N$_2$ snowline, while the inner planets accreted $3 \times$ stellar CO-enriched disk gas within the CO snowline. The excess volatile mass from pebble drift and evaporation implies an integrated pebble flux of $750 \pm 200~M_{\oplus}$. The increase in the planets' S/H with orbital distance implies more solid accretion further out, which is quantitatively compatible with expectations from both pebble and planetesimal accretion ($2 \times$ Minimum Mass Solar Nebula) paradigms.

We present MeerKAT observations searching for HI absorption in a sample of 17 powerful ($L_{\rm 1.4GHz}> 10^{27}$ W Hz$^{-1}$) radio sources at intermediate redshifts ($0.25<z<0.7$). The sample is well characterised at radio and optical wavelengths, allowing us to connect the presence (or absence) of HI to the properties of the AGN and its host galaxy. The sample consists mostly of core-dominated sources and quasars. Half of the targets have a UV luminosity $L_{\rm UV} = 10^{23}$ W Hz$^{-1}$, above this limit, the gas would be expected to be ionised by this radiation. We obtained 15 spectra free (or almost free) of radio frequency interference, reaching extremely low optical depths ($τ_{\rm peak} < 0.005$) resulting in three new HI absorption detections. Two are associated HI absorptions, giving a detection rate of such systems of $13\%\pm 7\%$. Both are found in young radio sources (PKS 1151-34 and PKS 1306-09), confirming the trend that this type of sources are more often detected in HI compared to more evolved ones. The UV luminosity of both these sources is below $10^{23}$ W Hz$^{-1}$. Surprisingly, one of the detections (PKS 1151-34) is hosted by a quasar, suggesting that the radio lobes are still embedded in the circumnuclear disc. In the second source (PKS 1306-09), the HI is highly blueshifted and likely part of a jet-driven outflow. A third detection is a 'local intervening' system, caused by a galaxy in the local environment of PKS 0405-12 and located in front of the southern radio lobe of this source, about 100 kpc in projection from this quasar. Overall, the results indicate a variety of plausible situations, which resemble what is seen at low redshifts. For the associated absorption, a combination of evolutionary status of the radio sources, physical conditions, and geometry of the gas structure determine the detection rate of HI absorption.

This paper presents a three-stage continuous adiabatic demagnetization refrigerator (CADR) simultaneously providing cooling platforms at two different temperatures. Unlike conventional CADR with two continuous stages, this system does not require an extra continuous stage. It is achieved with carefully designed heat switch operations and stage sequences. This new strategy significantly reduces system complexity and mass. The detailed implementation of the two cooling platforms is described, and factors limiting system performance are analyzed. This CADR system has achieved a cooling power of 20 μW@1 K and 4 μW@300 mK simultaneously, offering a new design strategy for the development of CADR with multiple continuous stages.

GECAM is a constellation of all-sky monitors in hard X-ray and gamma-ray band primarily aimed at high energy transients such as gamma-ray bursts, soft gamma-ray repeaters, solar flares and terrestrial gamma-ray flashes. As GECAM has the highest temporal resolution (0.1~$μ$s) among instruments of its kind, it can identify the so-called simultaneous events (STE) that deposit signals in multiple detectors nearly at the same time (with a 0.3~$μ$s window). However, the properties and origin of STE have not yet been explored. In this work, we implemented, for the first time, a comprehensive analysis of the STE detected by GECAM, including their morphology, energy deposition, and the dependence on the geomagnetic coordinates. We find that these STE probably result from direct interactions between high-energy charged cosmic rays and satellite. These results demonstrate that GECAM can detect, identify, and characterize high-energy cosmic rays, making it a Micro Cosmic-Ray Observatory (MICRO) in low Earth orbit.

K2-18b, a sub-Neptune exoplanet located in the habitable zone of its host star, has emerged as an important target for atmospheric characterization and assessments of potential habitability. Motivated by recent interpretations of JWST observations suggesting a hydrogen-rich atmosphere consistent with Hycean-world scenarios, we conducted a coordinated, multi-epoch search for narrowband radio technosignatures using the Karl G. Jansky Very Large Array equipped with the COSMIC backend and the MeerKAT telescope with the BLUSE backend. Our observations span frequencies from 544MHz to 9.8GHz and include multiple epochs that cover at least one full orbital period of the planet. In this work, we outline, create, and apply a comprehensive post-processing framework that incorporates observatory-informed RFI masking, drift-rate filtering based on the expected dynamics of the K2-18 system, multibeam spatial discrimination, primary and secondary transit filtering (when applicable), and SNR-based excision of weak and strong spurious signals. Across all bands and epochs, no signals consistent with an astrophysical or artificial origin were identified at a limit of 10^12 to 10^13W. These non-detections allow us to place upper limits on the presence of persistent, isotropic narrowband transmitters within the K2-18 system, providing the first interferometric technosignature constraints for a Hycean-planet candidate. Our results demonstrate the efficacy of coordinated multiepoch interferometric searches and establish a methodological framework for future technosignature studies of nearby potentially habitable exoplanets.

Recently, Subaru Hyper Suprime-Cam (HSC) observations found 12 candidates for microlensing events. These events can be explained by primordial black holes (PBHs) with masses of $10^{-7}$-$10^{-6} M_\odot$ and a fraction of all dark matter of $f_\mathrm{PBH} = \mathcal{O}(10^{-1})$. In this paper, we consider the PBH production in two types of the axionlike curvaton models, which predict an enhancement of the curvature perturbations on small scales. We show that the microlensing events can be explained in the axionlike curvaton model and discuss the cosmological implications such as gravitational waves.

We present a spectral line analysis of the hot molecular core G10.47+0.03 (hereafter, G10). Our aim is to determine molecular abundances and excitation conditions across a wide spectral range inaccessible to ground-based observatories. We utilize archival data from the Herschel Space Observatory, obtained with the Heterodyne Instrument for the Far-Infrared (HIFI). We report here the detection of high-excitation CO, 13CO, and C18O, H2O isotopologues, HCO+, HCN, HNC, CS, C34S, SO, SO2, H2CS, and CH3OH. CO, p-H2O, CS, and HCN show similar velocity profiles with a narrow, blueshifted component, which may be linked to the outer outflow layer. Redshifted wings may indicate inner outflow activity. A Markov Chain Monte Carlo framework is employed to infer column densities and temperatures accurately. We also performed spectral energy distribution fitting to constrain the global physical parameters of G10, providing essential context for interpreting the molecular emission. The MCMC analysis revealed two excitation temperature components: a warm component (30-65 K) and a hot component (90-250 K). The higher temperatures indicate dense, hot gas typical of massive hot cores. The lower temperatures correspond to the warm, less dense envelope around the core. Transitions of H2O, high-excitation CO, and HCN indicate outflowing gas and high-density shocked regions. These findings highlight G10's complex dynamical environment.

The origin of the soft X-ray excess below 2 keV in active galactic nuclei (AGNs) remains debated, with relativistic reflection from the inner accretion disk and warm Comptonization in an optically thick corona being the leading explanations. We investigate the timing and spectral properties of the Seyfert galaxy Mrk 110 using six XMM-Newton observations. A frequency-dependent lag analysis in the 7-9 $\times 10^{-5}$ Hz range reveals a soft X-ray lag of 889-3000s in the combined 2019 data, detected with a significance of 80%. The cross-correlation function analysis, supported by simulations, also detects lags of similar nature. Spectral modeling performed by adopting both proposed black hole masses in the literature for Mrk 110 confirms the presence of a warm corona in all observations, along with a weak relativistic reflection component and the reflection fraction remains low (Rf < 1). Interpreting the measured soft lag in terms of light travel time implies an emission radius 4.5 Rg for a supermassive black hole mass of $M = 1.4 \times 10^8$ solar mass , favoring a reflection scenario. However, if a lower mass of $M = 2 \times 10^7$ solar mass is adopted, the inferred radius increases, and both relativistic reflection and warm Comptonization can plausibly contribute to the observed soft lag. The warm corona radius appears larger in the high accretion state and smaller in a lower accretion state, although no trend can be established. The persistently low reflection fraction suggests an outflowing inner corona in Mrk 110, consistent with the recent detection of jet activity in this source.

The increasingly stringent observational bounds on primordial gravitational waves strongly constrain inflationary model building, favoring scenarios that predict highly suppressed tensor perturbations. While many viable constructions rely on non-canonical kinetic terms, non-minimal couplings, or modifications of gravity, it remains an open question whether comparably small tensor amplitudes can emerge within a minimal, single-field framework driven solely by potential dynamics. In this work we propose a novel inflationary scenario based on a modified Lennard-Jones potential. Inspired by a well-known interaction potential in molecular physics, the proposed form naturally combines a smooth minimum with an extended flat plateau at large field values. This intrinsic structure supports slow-roll inflation and ensures a graceful exit without introducing additional degrees of freedom. We perform a detailed analysis of the inflationary dynamics and confront the model with current observational constraints. We find that the scalar spectral index is fully consistent with CMB data, while the tensor-to-scalar ratio is predicted to be extremely small, reaching values as low as $r\sim10^{-7}$. Finally, the running of the scalar spectral index is also found to be small, well withing the 1$σ$ recent observational bounds from Atacama Cosmology Telescope.

73P/Schwassmann-Wachmann 3 is a short-period comet that has undergone multiple fragmentation events in the last few decades. During May-June 2006, while passing near Earth, multiple fragments of comet 73P passed sunward of Sun-Earth Lagrange Point 1, while cometary pickup ions were detected concurrently by instruments on both the ACE and Wind spacecraft, implying the crossing of one or more ion tail. Additionally, during August 2011, a fragment of 73P passed directly sunward of spacecraft STEREO-B. A detection of cometary ions is shown to originate at fragment 73P-AM. Solar wind velocity measurements are used to extrapolate the flow of the solar wind in 3 dimensions and, when compared with the positions of known comets and cometary fragments, estimate the separation between the cometary ion tail and the spacecraft. Using this technique, it is shown that the alignment of the major cometary fragments with the spacecraft was poor for the transport of cometary ions via the solar wind, but the encounter was near enough for immersion in the diffuse ion tail surrounding an extended dust trail within which the nucleus fragments reside. This implies that, at this distance, the extended trail of cometary debris was a significant source of cometary ions in the case of comet 73P.

In the interstellar medium, formic acid (HCOOH) plays a significant role in the synthesis of the simplest amino acid, glycine (NH$_{2}$CH$_{2}$COOH). The presence of HCOOH suggests that oxygen-bearing molecules may be directly involved in the chemical and physical evolution of star formation regions, particularly in hot molecular cores. This paper presents the first detection of the rotational emission lines of the $trans$-conformer of HCOOH toward the hot molecular core G358.93$-$0.03 MM1, located in the massive star formation region G358.93$-$0.03. This study employed high-resolution observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 7. The column density and excitation temperature of $t$-HCOOH are determined as $(8.13\pm0.72)\times10^{15}$ cm$^{-2}$ and $120\pm15$ K, respectively. The fractional abundance of $t$-HCOOH relative to H$_{2}$ is $(2.62\pm 0.29)\times 10^{-9}$. The column density ratios of $t$-HCOOH/CH$_{3}$OH and $t$-HCOOH/H$_{2}$CO are $(1.56 \pm 0.12)\times 10^{-2}$ and $(1.16 \pm 0.12)$, respectively. We computed a three-phase warm-up chemical model of HCOOH using the gas-grain chemical code UCLCHEM. We found that the observed and modelled abundances of HCOOH are almost identical, within a factor of 0.89. Based on chemical modelling, we showed that HCOOH may be formed through the reaction between HCO and OH on the grain surface, which is further released in the gas-phase.

We present multi-wavelength observations of the nearby spiral galaxy NGC 5938 (Araish) to investigate the origin of its radio emission, specifically the contribution from active galactic nucleus (AGN) activity and star formation. Using Evolutionary Map of the Universe (EMU) data, we detect extended radio emission extending outwards to the galactic axis, with a steep non-thermal spectral index ($α= -1.2 \pm 0.2$) indicative of synchrotron radiation from an AGN jet. The jet has a physical extent of $\approx 8.2\,kpc$ (angular length of $64^{\prime\prime}$). Multi-wavelength data from The Dark Energy Camera Plane Survey 2 (DECaPS2), Wide-field Infrared Survey Explorer (WISE), and extended Roentgen Survey with an Imaging Telescope Array (eROSITA) provide further support for this interpretation. The colour-colour diagram presenting WISE infrared observations suggests the presence of dust and young stars that trace the galaxy's disk structure. Our analysis reveals a radio jet, alongside star formation traced by infrared emission, demonstrating the complex interplay of AGN activity and star formation in this well-resolved galaxy. Intriguingly, the spatial relationship reveals the brighter X-ray emission to be largely adjacent to and enveloping the extended radio emission. This suggests that the radio jet, while extending at a significant angle to the galactic disk, is confined by the larger X-ray gas halo, similar to other systems (i.e., ESO 295-IG022, Centaurus A) and may indicate jet collimation and channelling effects.

In a dissipative system such as star or a galaxy, the emitted photons are decoupled from matter particles and may therefore be considered as part of a closed system to which the Second Law of Thermodynamics applies. In the present paper, we define a global entropy using a statistical approach that accounts for the contributions of both matter particles and photons. The statistical contribution of radiation is described as a photon gas in the definition of this global entropy. The increase in global entropy can foster structure formation -- rather than disorder -- because structures such as stars and galaxies are efficient at dissipating energy in the form of photons, and thus at producing entropy. We show that stars generate a nearly equal amount of specific entropy, and therefore a comparable number of photons per unit mass, over their lifetime on the main sequence of the Hertzsprung-Russell (HR) diagram. This suggests that the main sequence of the HR diagram constitutes a locus of convergence toward a universal specific entropy production by stars. We then examine the implications of this approach for the star-formation main sequence in galaxies, and find a similar result. The emergence of organized structures in cosmic history reflects the second law, as organized matter is efficient at generating entropy through the slicing of energy into lower-frequency photons. This is also reflected in the dominant contribution of low-frequency photons to the extragalactic background light. Finally, we briefly discuss how this perspective may inform us on the possibility of the existence of life elsewhere in the universe.

Recent advances in Large Language Models (LLMs) offer unique opportunities for scientific tasks, yet their ability to reason over complex numerical data remains largely unexplored. We propose a simple mechanism to introduce domain-specific physical knowledge into LLMs by fusing pre-trained latent physical features with a pre-trained language model. Our method employs a teacher-student knowledge distillation framework where a large LLM (teacher) generates synthetic question-answer supervision to transfer physical reasoning to a smaller LLM (student). The student is conditioned on latent physical features and trained via a lightweight adapter and Low-Rank Adaptation (LoRA). We demonstrate that this approach, applied to models with 1B, 8B, and 32B parameters, enables effective reasoning over real scientific data. Our models substantially outperform strong baselines, such as Gemini 3 Pro, across multiple downstream tasks without task-specific fine-tuning. We show that the model combines latent information with general physical understanding to predict complex properties and can be "steered" by identifying physically meaningful directions in the latent space. This allows for explicit physical manipulation and natural language interpretation of latent structures. While our experiments focus on astrophysics, the framework is domain-agnostic and applicable to various scientific fields. Our main contribution is a general framework for using LLMs as interpretable interfaces to scientific latent spaces, enabling a single model to perform diverse tasks through natural language guidance. This work marks a step toward developing scientifically capable and useful LLMs.

We present here two H II region catalogues with azimuthal resolution for the two grand design galaxies NGC 628 and NGC 6946. With the help of these catalogues, we study several properties of the star-forming processes occurring in spiral galaxies. We obtained direct imaging in the narrow-band filters centred at Hα, H\b{eta}, [O II]λ3727, and [O III]λλ4959, 5007 and their respective continua. After the calibration and correction of the data, we obtained for each H II region the de-reddened fluxes in the aforementioned lines, the size, the Hα equivalent width, and, using two different empirical calibrations, the metallicity. Employing a method based on the Delaunay triangulation, a two-dimensional (2D) representation of the metallicity was obtained. Data for 209 H II regions of NGC 628 and 226 H II regions of NGC 6946 are obtained. The radial behaviours of the Hα equivalent width, the excitation, and the oxygen abundance are derived. Two-dimensional representations of the metallicity and the excitation are calculated for the galaxies in the study. The two empirical calibrations of the metallicity are compared. The oxygen abundance gradients obtained in this study agree with previously published values. However, more regions were examined than in previous studies. We find a difference of about 0.6 dex between the two empirical calibrations employed. Finally, the 2D representations of the metallicity reveal high metallicity knots in NGC 628, and for NGC 6946 a high metallicity azimuthal structure is discovered. These high metallicity regions seem to be linked to the arms of the galaxies and are probably produced by an increase in the temperature of the ionizing clusters in the H II regions, which may be linked to variations in the initial mass functions of the galaxies between the arm and interarm regions.

We present 120s cadence TESS observations of three superoutbursts of the SU UMa-type dwarf nova VW Hydri. Two events (SO2 in Sectors 87+88 and SO3 in Sector 93) exhibit a pronounced, temporally pronounced precursor-dip followed by a rapid rise into the main superoutburst plateau. This morphology, previously seen in Kepler light curves of V1504 Cyg and V344 Lyr, is a key prediction of the thermal-tidal instability (TTI) model when a normal (precursor) outburst expands the disk only marginally beyond the 3:1 resonance radius, allowing the tidal instability to grow slowly and produce a deep dip approaching quiescence before rapid amplification drives the main superoutburst. A sliding-window time-frequency analysis reveals superhump power already during the decline and near minimum light, with a smooth period evolution across the dip and stabilization after the system returns to the hot state, consistent with the growth and saturation of disk eccentricity at the 3:1 resonance. From the stabilized Stage A superhump periods, we infer a representative mass ratio $q = 0.131 \pm 0.002$. Combined with either a typical SU UMa white-dwarf mass prior or the semi-empirical donor sequence at an orbital period of 107~min, the implied component masses are $M_1 \simeq 0.6$--$1.0\,M_\odot$ and $M_2 \simeq 0.08$--$0.14\,M_\odot$, ruling out a brown-dwarf donor and establishing VW~Hyi as a benchmark system for testing tidal-instability models in low-$q$ dwarf novae.

Gravitational-wave (GW) detections by the LIGO-Virgo-KAGRA (LVK) observatories suggest multiple formation channels for GW compact binary mergers. Here I assess the role of young massive clusters (YMC) evolving into old open clusters (OC) -- the YMC/OC channel -- to the GW merger population. A homogeneous grid of 90 N-body evolutionary model star clusters, spanning initial masses of $10^4M_\odot\leq M_{cl}(0)\leq10^5M_\odot$, half-mass radii of 1-3 pc, and metallicities between 0.0002-0.02 is computed with the direct, post-Newtonian N-body code NBODY7. The N-body simulations include primordial binaries, delayed stellar-remnant model forming black holes (BH) and neutron stars (NS), BH spin prescriptions, and GW recoil kicks, and they are evolved until BH depletion. Most GW mergers from the cluster models are dynamically assembled binary black holes (BBH) that merge within their host clusters. Merger mass ratios reach down to 0.1-0.2 despite an overall bias toward nearly symmetric pairs. The GW merger efficiency varies non-monotonically with cluster mass, peaking around $M_{cl}(0)=7.5\times10^4M_\odot$ and also for $M_{cl}(0)\leq3.0\times10^4M_\odot$. The computed mergers reproduce some of the key features of the latest observed GW event catalogue, including asymmetric low-mass mergers, misaligned events among highly spinning, massive BHs, and an excess of $30M_\odot$ primaries, though they under-produce $10M_\odot$ primaries, hinting at contributions from other channels. The model merger rate density accounts for 25%-33% of the observed rate; it increases with redshift somewhat faster than the cosmic star formation, consistently with LVK's inferences. The model effective spin distribution is positively asymmetric at zero redshift and broadens with redshift. The models yield field BH- and NS-main sequence star binaries with parameters consistent with the Gaia-discovered candidates. [Abgd.]

Recent observations from the Dark Energy Spectroscopic Instrument (DESI) 2024, combined with CMB and SNIa data, indicate a preference for a dynamical dark energy equation of state that crosses the phantom divide ($w < -1$). This finding challenges the standard $Λ$CDM model and minimally coupled scalar field scenarios, including the original Running Curvaton model, which is typically constrained to the quintessence regime. In this work, we propose a unified cosmological framework by extending the Running Curvaton model via a non-minimal gravitational coupling of the form $ξχ^2 R$. We demonstrate that this geometric modification allows the effective equation of state to naturally evolve from a quintessence-like to a phantom-like regime in the Jordan frame, thereby providing a superior fit to the DESI observational contours ($w_0 > -1, w_a < 0$). Crucially, we show that the introduction of non-minimal coupling does not compromise the model's success in describing the early universe. Through a parameter re-tuning mechanism involving the coupling constant ($g_0^{obs} = g_0 + 2ξ$), the predictions for the primordial power spectrum (spectral index $n_s$) and local-type non-Gaussianity ($f_{NL}$) remain strictly preserved and consistent with Planck data. Furthermore, we perform a comprehensive stability analysis within the Horndeski framework, verifying that the model remains free from ghost and gradient instabilities ($c_s^2 = 1$). Our results suggest that the non-minimally coupled Running Curvaton offers a robust, stable, and unified description of inflation and late-time accelerated expansion compatible with the latest precision cosmology data.

We study massive disk galaxies (total stellar mass$>=10^{11}$ $\mathrm{M_{\odot}}$) from IllustrisTNG50 simulation, and perform 2-D structural decomposition of the galaxies using their idealised, synthetic SDSS images for z=0. We find an interesting sample of galaxies having a central high surface brightness (HSB) stellar disk, surrounded by an extended low surface brightness (LSB) stellar disk, similar to giant LSB galaxies. These massive, double-exponential disk galaxies are found to be hosted by dark matter haloes of $\sim 10^{12} \mathrm{M_{\odot}}$ in agreement to observations of such galaxies. Their maximum rotation velocity, an approximate measure of their dynamical mass, lies within $\sim$ (300-500) km/s. The stellar-to-dark matter mass ratio and the baryon-to-dark matter mass ratio of the sample lies in the range of $\sim$ (0.04 - 0.46) and $\sim$ (0.07 - 0.47) respectively. Our results show that cosmological simulations are able to form disc galaxies with HSB plus LSB disks, as in observations.

Stellar outbursts from variable or periodic accretion are thought to be ubiquitous across young stellar populations. However, relatively few outbursting objects have been discovered to date. Here, we present the characterisation of a new EXor-type episodic accretor. We aim to characterise the nature of the 2023 outburst of SPICY 97589/Gaia23bab and characterise the stellar source for the first time, while exploring how an accretion outburst contributes to disk evolution. We employ multi-waveband medium-resolution spectroscopy with UVB-VIS-NIR coverage during the peak of the 2023 outburst and the post-outburst quiescent object. The broad wavelength coverage of the dataset allows for robust measurements of the accretion rate using known line tracers. The addition of quiescent spectra provides a good estimation of stellar parameters of the central star while also informing us on the evolution of the disk during outburst phases. We find the stellar source to be a 3410\,K, M3.0 type star with a luminosity of 0.41 $L_\odot$ and an estimated stellar mass of 0.29 $M_\odot$. We measure the accretion rate of SPICY 97589 to be $\dot M = 2.38\pm0.58\times10^{-7}\,\mathrm{M_\odot yr^{-1}}$. This value is at two orders of magnitude greater than the quiescent accretion rate. Thus, we confirm that the 2023 outburst was driven by an influx of material from the surrounding environment to the central star, an accretion outburst. The spectral fingerprint of emission lines is also characteristic of an outbursting EXor-type source, including variable disk winds.

The existence of Galactic optical cirrus poses a challenge for observing faint objects within our Galaxy and dim extragalactic structures. To investigate individual cirrus filaments in the Hyper Suprime-Cam Subaru Strategic Program public data release 3 (HSC-SSP DR3) we use a technique based on convolutional neural networks and ensemble learning. This approach allows us to distinguish cirrus filaments from foreground and background objects across the entire HSC-SSP, using optical images in the $g$, $r$, and $i$ wavebands. A comparison with previous work using deep Sloan Digital Sky Survey Stripe~82 (SDSS Stripe~82) data reveals that the cirrus clouds identified in this study are highly consistent in location within the overlapping survey region. However, in the deeper HSC-SSP dataset, we were able to detect $4.5$ times more cirrus clouds. Our study indicates that the sky background in HSC-SSP coadd images is over-subtracted, as evidenced by the surface brightness distribution in cirrus filaments and surrounding regions. Objects with surface brightness of $m = 29~\mbox{mag~arcsec}^{-2}$ near large filaments can be dimmed by over-subtraction of $0.5$ magnitude in the $r$ band. This suggests that cirrus clouds should be taken into account in algorithms for estimating the sky background. For practical use, we provide a catalog of filaments and a framework that allows one to train neural network models for segmenting cirri in HSC-SSP coadd images.

The electron density of the solar corona is a fundamental parameter in many areas of solar physics. Traditionally, routine estimates of coronal density have relied exclusively on white-light observations. However, these density estimates, obtained by inverting the white-light data, require simplifying assumptions, which may affect the robustness of the measurements. Hence, to improve the reliability of coronal density measurements, it is highly desirable to explore other complementary methods. In this study, we estimate the coronal electron densities in the middle corona, between approximately $1.7-3.5R_\odot$, using low-frequency radio observations from the recently commissioned Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA). The results demonstrate consistency with those derived from white-light coronagraph data and predictions from theoretical models. We also derive a density model valid between 1.7--3.5 $r_\odot$ and is given by $ρ(r')=1.27r'^{-2}+29.02r'^{-4}+71.18r'^{-6}$, where $r'=r/R_\odot$, and $r$ is the heliocentric distance. OVRO-LWA is a solar-dedicated radio interferometer that provides science-ready images with low latency, making it well-suited for generating regular and independent estimates of coronal densities to complement existing white-light techniques.

Pollux is a high-resolution spectrograph and spectropolarimeter working from 100 nm to 1.8 microns proposed for HWO by a European consortium. Pollux will allow us to study stellar and (exo)planetary systems, as well as cosmic ecosystems. For example, Pollux will provide new insights on exoplanet formation and evolution, characterization of the atmospheres and magnetospheres of stars and planets, and star-planet interactions. It will also allow us to resolve narrow UV emission and absorption lines, enabling us to follow the baryon cycle over cosmic time -- from galaxies forming stars out of interstellar gas and grains, and planets forming in circumstellar disks, to the various forms of feedback into the interstellar and intergalactic medium -- and from active galactic nuclei. The most innovative characteristic of Pollux is its unique spectropolarimetric capability in the UV, which will open a new parameter space. Its very high spectral resolution (~70000 to ~100000) and stability over a very large wavelength range will also be a major asset. In this paper, we summarize the main scientific drivers of Pollux and present its current design, technological challenges, and the Pollux consortium organization.

TIC 277539431, a fast rotating M7 dwarf, was detected to host the highest latitude flare to date at $81^\circ$. Magnetic activity like stellar flares occurring at high latitude indicate occurrence of coronal loops at these latitudes on fully-convective M dwarfs. In contrast, sunspots usually occur below $30^\circ$. In our study we look for modulation on the X-ray signal occurring due to occultation of coronal loops by the star due to stellar rotation. We report an updated rotation period for this star as $P_{\text{rot}}=273.593$ min based on TESS sectors 12, 37, 39, 64 and 65. We conducted $χ^2_{\textrm{red}}$ fits by varying the amplitude and the phase of a sinusoidally modulated signal derived from the new rotation period. We find no evidence of rotational modulation in the X-ray signal. This could be due to multiple scenarios, such as lack of a stable coronal loop during observation or the modulated signal being too weak, however given the dataset, individual scenarios cannot be distinguished.

Understanding the earliest stage of star and planet formation requires detailed observations to address the connection and interplay between the accretion, outflow, and disk evolution. We present results from observations of the low luminosity ($L_{\mathrm{bol}} \sim 0.2,L_{\odot}$) and low mass ($M_{*} \sim 0.15,M_{\odot}$) Class 0 protostar IRAS~16253$-$2429, conducted as part of the eDisk ALMA Large Program and the JWST Cycle~1 GO program IPA. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at $\leq 5,μ$m), with a brighter, extended northern side. We detect 15 pure rotational H$2$ transitions ($E{\mathrm{up}} = 1015$--21411~K), revealing a wide-angle molecular outflow. The outflow width traced by H$_2$~0-0~S(11) at the protostellar location measures $\leq 35$~au, slightly larger than the dust and Keplerian disk diameters ($\sim 30$~au) but wider than the 20--23~au jet width in [Fe~II]. The opening angle narrows from 40--35 degrees for the low-$J$ H$_2$ lines (up to S(5)) and the cold gas component traced by ALMA $^{12}$CO to $\sim 28$--19 degrees for the high-$J$ H$_2$ lines (S(7)--S(11)). Position--velocity diagrams of H$2$ reveal higher velocities for higher $E{\mathrm{up}}$, ranging from $\sim 12.5$~km~s$^{-1}$ for H$_2$~0-0~S(1) and S(2) to $\sim 28.5$~km~s$^{-1}$ for H$_2$~0-0~S(5) and S(7) with respect to the mean flow velocity. The nested excitation and velocity structure of the collimated jet and wide-angle wind suggests a magnetohydrodynamic wind as a likely launching mechanism, similar to findings in other protostars and Class~II sources. The lower-velocity millimeter CO emission may be gas from the infalling envelope accelerated outward by the wide-angle wind along the cavity walls.

We investigate the diagnostic potential of the G-band at 430.4 nm for probing small-scale magnetic fields in the solar photosphere. Combining three-dimensional MHD simulations from the MURaM code and spectral synthesis via the RH 1.5D code, we evaluate the intensity contrast in the G-band filtergrams by comparing the filter centered at 430.4 nm in comparison to the conventional 430.5 nm. Our results show that filtergrams centered at 430.4 nm provide higher contrast across varying magnetic environments, particularly at narrow filter widths. This enhancement arises from its slightly higher formation height and greater sensitivity to temperature variations in magnetized regions. These findings indicate that G-band filtergrams centered at 430.4 nm show enhanced diagnostic potential under the assumptions of the present modeling. The obtained results are also relevant and suggest potential applications in stellar contexts, where molecular bands are often used as proxies for magnetic activity.

Dust emission at submillimeter wavelengths can be used to reliably trace the basic properties of molecular clouds. Early results from a recent Submillimeter Array (SMA) survey of the Andromeda Galaxy (M31) include the first detections of resolved dust continuum emission from individual giant molecular clouds (GMCs) in an external spiral galaxy. This paper updates on the now-complete SMA survey of 80 Herschel-identified giant molecular associations (GMAs) in M31. The SMA survey simultaneously probes dust continuum emission at 230 GHz and the $J = 2 \rightarrow 1$ transitions of the CO isotopologues, $^{12}\rm CO$, $^{13}\rm CO$, and $\rm C^{18}O$ at a spatial resolution of $\lesssim 15~\mathrm{pc}$. Dust continuum emission was detected in 71 cloud cores, of which 26 were resolved. This more than doubles the size of the previous sample. By comparing dust and CO observations with identical astrometry, we directly measure the dust mass to-light ratios, $\rm α^{\prime}_{^{12}CO}$, and $\rm α^{\prime}_{^{13}CO}$. We derive $<α^{\prime}_{\rm ^{12}\rm CO}>~=~0.070~\pm~0.031~M_{\odot}\,(\rm K~km~s^{-1}~pc^{2})^{-1}$ and $<α^{\prime}_{\rm ^{13}\rm CO}>~=~0.37~\pm~0.20~M_{\odot}\,(\rm K~km~s^{-1}~pc^{2})^{-1}$ for the increased sample, which are in agreement with previously reported values. From virial analysis, we find that 80% of the GMC regions traced by resolved dust emission are bound and close to virial equilibrium. Finally, we update our analysis on the metallicity dependence of $\rm α^{\prime}_{\rm CO}$ by combining SMA observations with existing MMT/Hectospec optical spectroscopy toward H II regions. We find no trend in $\rm α^{\prime}_{\rm CO}$ with metallicity, supporting the previous findings.

The INTEGRAL satellite explored the gamma-ray sky since its launch on October 17, 2002, and until the end of its scientific operation on February 28, 2025. A large fraction of the available data is still largely untouched, due to the complexity of analysis. We describe the latest in-flight calibration of the Compton mode of the INTEGRAL/IBIS telescope, taking into account more than twenty years of data. The spectroscopy and polarization of the standard candle that is the Crab Nebula is analyzed in detail. We operate the IBIS telescope as a Coded mask Compton telescope, using the Crab Nebula to refine the calibration, as is usually done for high-energy instruments. We have determined the spectroscopic and polarimetric properties of the IBIS Compton mode and their evolution along the entire duration of the mission. In addition, the long-term evolution of the Crab Nebula's polarization has been successfully measured and compared with other high-energy experiments. We could estimate the energy dependence of the Crab Nebula polarization in four bands between 200 keV and 1 MeV. In particular, the detection of polarized emissions strictly above 400 keV makes it the highest energy measurement ever performed for the Crab Nebula. A Python library was also made publicly available to analyze processed data.

The calibration of Cosmic Origins Spectrograph (COS) data is performed by the data processing pipeline known as CalCOS. CalCOS utilizes several reference files that store information required for data processing (e.g., dispersion solutions), and these reference files can be updated for the purpose of improving calibrated data products. In 2024 a major effort to improve the far-ultraviolet (FUV) geometric distortion, delta-geometric, and walk corrections was completed. Those three corrections occur early in the CalCOS workflow and shift photon events into the corrected reference frame ((XCORR, YCORR) coordinate system) in which subsequent calibration steps-and their reference files-are defined. This change necessitated the re-derivation of all "downstream" reference files in use at the time. Here we summarize the effort to create new versions of 56 reference files applicable to lifetime positions 1 through 6 and intended for use with the new geometric distortion, delta geometric, and walk corrections. The primary outcome of this work is improved wavelength and flux calibrations for COS FUV spectra.

We present an in-depth analysis of the eclipsing binary DD CrB, composed of a B-type subdwarf primary and an M-type main-sequence secondary, with the main goal of investigating its eclipse timing variations (ETVs). Our new multi-color photometric observations, radial velocity measurements, and precise eclipse timings from TESS allow us to constrain the system parameters. The Romer delay between primary and secondary minima yields a mass ratio of $q = 0.299 \pm 0.009$, enabling robust simultaneous modeling of the light and radial velocity curves with {\sc phoebe} 2.17. By fixing the albedo of the secondary to its maximum physically plausible value (A$_2 = 1.0$), despite the degeneracy between albedo, surface temperature, and radius, we obtained a satisfactory fit, resulting in a significantly lower temperature ($T_2 \sim 2360$ K) and a radius ($R_2 \sim 0.16$ R$_\odot$) in agreement with literature values. Using the total mass of the components and the orbital size derived from this modeling, we interpret the ETVs and find them best explained by a Jupiter-mass tertiary companion on a $\sim13$-year orbit in all competing models, while the eccentric (e $\sim0.46$) models perform better in terms of fit statistics.

Solar pores are strongly magnetized regions lacking a photospheric penumbra and characterized by predominantly vertical magnetic fields. We present a multi-line study of flashes in a solar pore using high-resolution observations from the Swedish 1-m Solar Telescope in Fe~\textsc{i}~6302~Å, Ca~\textsc{ii}~8542~Å and K, and H-$β$, complemented by (E)UV data from \textit{IRIS} and \textit{SDO}/AIA. Bisector analysis and spectral inversions with \textsc{SIR} and \textsc{NICOLE} were used to infer stratifications of temperature, line-of-sight velocity, and magnetic field. Flashes, confined to one half of the pore, exhibit cooler photospheric temperatures ($ΔT \approx 400$~K), stronger magnetic fields ($ΔB \approx 250$~G), larger inclinations ($\sim25^{\circ}$ versus $\sim18^{\circ}$), and persistent upflows ($\sim0.5$~km~s$^{-1}$) compared to the quiescent pore. They are co-spatial with enhanced 3- and 5-minute power in the photosphere, while only 3-minute power persists in the chromosphere. Flashes are detected down to $\sim50\%$ line depth in Ca~\textsc{ii}~8542~Å intensity and show central chromospheric upflows ($\sim1$~km~s$^{-1}$) flanked by strong downflows ($\sim8$~km~s$^{-1}$). Temperature enhancements reach $\sim500$~K at $\logτ\approx -5$ and $\sim2500$~K at $\logτ\approx -6$, with a bimodal velocity distribution. Flashes correspond one-to-one with radially outward running waves near the pore boundary (5--15~km~s$^{-1}$). Strong Ca~\textsc{ii} core emission, occasional Stokes~$V$ reversals, and H-$β$ enhancements indicate that pore flashes are confined to the lower and mid-chromosphere, with little influence on higher atmospheric layers.

The circumnuclear star-forming ring of the barred spiral galaxy NGC 1097 provides a unique laboratory to study star formation under extreme conditions. This work aims to derive the physical properties of the circumnuclear star-forming regions (CNSFRs) using MUSE integral field spectroscopy observations. A total of 24 individual ionised HII are identified and analysed within its ring, which spans from $\sim$385 pc to $\sim$1.3 kpc. Despite the complex nuclear activity, all HII regions are found to be purely photoionised. Directly derived abundances reveal supersolar metallicities, with the highest one exceeding five times the solar value (12+log(S/H) = 7.875 $\pm$ 0.353, T$_e$([SIII]) = 3912 $\pm$ 567 K), and representing the highest abundance reported to date. In this high-metallicity regime, we find a break in the ionisation parameter-[SII]/[SIII] relation, which can be explained by changes in the ionisation structure and line emissivities, as confirmed by photoionisation models that successfully reproduce the observed emission-line ratios. Our results also indicate that the local gas supply regulates the star formation activity within the ring, with the young stars ionising 8 % of the total gas in the ring. Furthermore, our findings support a propagating starburst scenario, originating in the galaxy nucleus and extending towards the ends of the bar and into the circumnuclear ring through bar-driven shocks, this being consistent with the results of previous multi-wavelength studies. Finally, we likely detect optical signatures associated with one of the two known jets in this galaxy. This finding, together with the radio core emission previously found at sub-parsec scales, reflects the presence of feedback processes operating even on small galactic disc scales.

By examining recently published images in different wavelengths, I identify a point-symmetric morphology in the Large Magellanic Cloud core-collapse supernova (CCSN) remnant (CCSNR) J0450.4-7050 (SNR 0450-70.9; nicknamed Veliki), which I attribute to at least three pairs of energetic jets that participated in the explosion of the progenitor in the framework of the jittering jets explosion mechanism (JJEM). Two pairs of ears, a pair of blowouts in the north and south along the long axis of this SNR, and a pair of dents compose the point symmetric morphology. The fact that the symmetry axes of two pairs include pairs of opposite structural features in the inner ejecta implies that the shaping is by jets and not due to an interaction with an ambient material. While the JJEM predicts such morphologies, the competing neutrino-driven mechanism cannot account for point-symmetric morphologies. This study provides strong support for the claim that the JJEM is the primary CCSN explosion mechanism.

This study evaluates a technique for determining the mass of a potentially hazardous asteroid from a high-speed flyby in the context of a rapid reconnaissance planetary defense scenario. We consider a host spacecraft that dispenses a small CubeSat, which acts as a test-mass. Both spacecraft perform approach maneuvers to target their flyby locations, with the host targeting a close proximity flyby and the CubeSat targeting a distant flyby. By incorporating short-range intersatellite measurements between the host and the CubeSat, the mass measurement sensitivity is substantially improved. We evaluate a set of proposed host and CubeSat hardware options against the 2023 and 2025 Planetary Defense Conference hypothetical threats, as well as a hypothetical flyby of 2024 YR4. These scenarios differ predominantly in their flyby speeds, which span from 1.7 to 22 km/s. Based on these scenarios, we demonstrate that a typical radio-frequency intersatellite measurement is ineffective for asteroids with diameters relevant to planetary defense (i.e., 50 - 500 m). However, we find that augmenting the system with a laser-based intersatellite ranging system or a high-precision Doppler system can enable mass measurements of asteroids as small as 100 m across all cases, and as small as 50 m for the slower (< 8 km/s) cases. The results are very sensitive to the timing of the final maneuver, which is used to target the low-altitude flyby point. This presents an operational challenge for the smallest objects, where optical detection times are comparatively late and the optical navigation targeting knowledge converges too slowly.

We present legacy cosmic shear measurements and cosmological constraints using six years of Dark Energy Survey imaging data. From these data, we study ~140 million galaxies (8.29 galaxies/arcmin$^2$) that are 50% complete at i=24.0 and extend beyond z=1.2. We divide the galaxies into four redshift bins, and obtain cosmic shear measurement with a signal-to-noise of 83, a factor of 2 higher than the Year 3 analysis. We model the uncertainties due to shear and redshift calibrations, and discard measurements on small angular scales to mitigate baryon feedback and other small-scale uncertainties. We consider two fiducial models to account for the intrinsic alignment (IA) of the galaxies. We conduct a blind analysis in the context of the $Λ$CDM model and find $S_8 \equiv σ_8(Ω_m/0.3)^{0.5}=0.798^{+0.014}_{-0.015}$ (marginalized mean with 68% CL) when using the non-linear alignment model (NLA) and $S_{8} = 0.783^{+0.019}_{-0.015}$ with the tidal alignment and tidal torque model (TATT), providing 1.8% and 2.5% uncertainty on $S_8$. Compared to constraints from the cosmic microwave background from Planck 2018, ACT DR6 and SPT-3G DR1, we find consistency in the full parameter space at 1.1$σ$ (1.7$σ$) and in $S_8$ at 2.0$σ$ (2.3$σ$) for NLA (TATT). The result using the NLA model is preferred according to the Bayesian evidence. We find that the model choice for IA and baryon feedback can impact the value of our $S_8$ constraint up to $1σ$. For our fiducial model choices, the resultant uncertainties in $S_8$ are primarily degraded by the removal of scales, as well as the marginalization over the IA parameters. We demonstrate that our result is internally consistent and robust to different choices in calibrating the data, owing to methodological improvements in shear and redshift measurement, laying the foundation for next-generation cosmic shear programs.

The presence of infrared excess flux observed in white dwarfs (WDs) is related to the existence of debris disks or substellar companions. These systems provide important clues in the study of extrasolar planetary material and binary evolution. However, fully characterising their properties requires a statistically significant, complete sample. This work aims to identify a complete sample of WDs with infrared excess emission within 100 pc of the Sun. We built the spectral energy distributions (SEDs) of the WDs using synthetic photometry in 56 optical filters of the J-PAS system, generated from Gaia Data Release 3 low-resolution spectra and complemented with the latest infrared photometry available at the Virtual Observatory (VO). VOSA was used to fit the SEDs with different atmospheric WD models depending on the source spectral type. We visually checked optical and infrared images to identify contaminated photometry. We built a catalogue of 456 infrared excess WDs, of which 292 are robust identifications, and 164 are candidates. 351 ($\sim$75%) are new identifications. This implies a fraction of infrared excess WDs between 5.9$\pm$0.3% and 9.2$\pm$0.4%, higher than previous works, but in agreement with some more recent estimates. Furthermore, for the sample of infrared excess WDs, the fraction of sources with non-hydrogen atmosphere increases with the Gaia GBP-GRP colour, contrary to the general WD population. However, this result should be interpreted with caution. Additionally, a thorough comparison of our catalogue with those of previous studies was performed. The sample of WDs with infrared excess emission within 100 pc presented in this work is the largest, most complete and reliable to date. Due to their proximity, they are ideal targets for follow-up studies aimed at characterising circumstellar disks, substellar companions, and the composition of accreted planetary material.

We present a spatially resolved spectroscopic analysis of the Helix Nebula (NGC 7293) using data from the SDSS-V Local Volume Mapper (LVM), by applying the recently developed LVM Data Analysis Pipeline (LVM-DAP). Covering the full optical range (3600-9800 Å) over a contiguous ~ 0.5 degree field, the LVM data provide the first hexagonally sampled, wide-field emission-line maps of all major ionic species in this archetypal planetary nebula. The resulting flux, kinematic, and line-ratio maps reveal the well-known ionization stratification of the nebula, from the compact He++ core to the bright [O III] ring and the extended low-ionization envelope, enabling a detailed comparison with classical aperture spectroscopy. Owing to the sensitivity and uniform spatial sampling of the LVM, numerous faint auroral and diagnostic lines are detected across the nebula, including [O III] 4363, [N II] 5755, and He I lines, allowing precise measurements of weak-line morphology. The derived radial trends confirm the remarkably low dust content and the overall homogeneity of electron temperature and density across the main ring. Ionized-gas kinematics traced by Hα further support the scenario of a slowly expanding, limb-brightened shell consistent with previous studies. This work demonstrates the diagnostic power of LVM spectroscopy for extended nebulae and highlights its capability to recover both global and spatially resolved physical conditions across complex ionized structures.

We use measurements of the intergalactic medium (IGM) temperature from the Lyman-$α$ forest to place new limits on models in which long-lived dark sector (DS) particles, with lifetimes longer than $10^{16}$ s, deposit energy into the IGM through their decays. Such DS decays into Standard Model (SM) states can modify the late-time thermal history of the IGM, making Lyman-$α$ data a sensitive probe of hidden sectors with cosmologically long lifetimes. Our analysis demonstrates that constraints from late-time IGM heating offer a complementary window to those from the Cosmic Microwave Background (CMB), in constraining dark sector parameter space. We further revisit limits on such decaying DS models from Planck's measurements of the optical depth to reionization and provide updates relevant for DS lifetimes longer than $10^{14}$ s. The model-independent constraints on the DS parameter space we derive in this work can be reinterpreted for a wide range of decaying hidden-sector scenarios, including evaporating primordial black holes and SM-coupled dark photons.

Mixing by hydrodynamical instabilities plays a key role in cloud-wind interactions, causing cloud destruction in the adiabatic limit and facilitating cloud survival with efficient radiative cooling. However, the rate of mixing in numerical simulations is sensitive to the smallest resolved scale, and the relationship between resolution and cloud evolution is under-explored. Using a set of cloud-crushing simulations, we investigate the effects of numerical resolution on cloud survival and acceleration. Modeling both adiabatic and radiative cases, in a subsonic and supersonic wind, we find that cloud survival and velocity does depend on the numerical resolution, however, no single resolution requirement can be applied to all scenarios. In the radiative subsonic case, we find that mass growth and acceleration appear converged at only 4 cells per cloud radius. Conversely, in the supersonic regime, we see a clear dependence of cloud destruction and velocity on resolution that is not converged even at 48 cells per cloud radius, implying that accurately capturing cloud destruction may require higher resolution than capturing growth. We also present a simple model illustrating how ram pressure accelerates cool clouds at early times before mixing kicks in as an acceleration mechanism.

Type Ia supernovae (SNe Ia) are thermonuclear runaways in certain white dwarfs in binary systems. They have been extensively studied, yet their progenitor and explosion mechanisms remain poorly understood. We study a large sample of SNe Ia comparing the narrow interstellar absorption features in their spectra with various photometric and spectroscopic supernova properties, as well as with environmental characteristics. We find that the sodium absorption is significantly stronger in younger, more star-forming and more centrally located SNe Ia, as expected. However, we also show that there is a strong dependence on intrinsic properties that is independent of the environment. In fact, we find strong evidence for two environmental SN Ia populations, an old and a young one, with the young population showing significantly different distributions of sodium strength when divided according to the Si II ejecta velocity, nebular velocity, extinction, E(B-V), and reddening curve, RV. Performing a clustering of the SNe Ia, we recover an old population of SNe with low extinction and normal ejecta velocity, while we confirm that the young population can be subdivided into a group of highly-extincted, high-velocity SNe Ia with much stronger blueshifted sodium absorption, and another of low-extincted, normal-velocity objects with little sodium absorption. We interpret this relation of intervening material with intrinsic properties as evidence for the young SN Ia population, occurring in young and star-forming environments, to have asymmetric radiation that interacts with nearby material, and whose observables depend thus on the viewing angle. Finally, we show that the cosmological mass-step is consistent with these populations.

We present a measurement of the full shape of the power spectrum of the thermal Sunyaev-Zeldovich (tSZ) effect down to arcminute scales using cosmic microwave background (CMB) data from the South Pole Telescope (SPT) over roughly 100 ${\rm deg}^{2}$ field. The analysis incorporates data from the 2019/20 seasons of the SPT-3G survey in bands centered at 95, 150, and 220 GHz; from the full SPTpol dataset at 150 GHz; and from {\it Herschel}-SPIRE survey in bands centered at 600 and 857 GHz. We combine data from all the above bands using linear combination (LC) techniques to produce a tSZ or Compton-$y$ map. We modify the LC weights to produce multiple versions of the Compton-$y$ map, including minimum-variance (MV) and foreground-minimized (-min) maps. We measure the auto- and cross-spectra of a subset of these maps in the range $\ell \in [500, 5000]$. While this power spectrum includes contributions from signals other than tSZ, we present numerous checks to show that the most challenging foreground signal, the cosmic infrared background (CIB) is much lower than the desired tSZ signal in the scales of interest in this work. The final tSZ power spectrum is measured at $9.3σ$ with both the MV and CIB-min maps. Our results are consistent with those reported in other CMB surveys across the literature. Using the difference in the tSZ power spectrum from MV and CIB-min maps, we reconstruct the scale-dependent tSZ-CIB cross-correlation $ρ_{\ell}^{\rm tSZ \times CIB}$, finding $3.1σ$ evidence for a nonzero correlation coefficient that is positive on large scales and approaches zero for $\ell > 2500$. This result represents the deepest tSZ maps ever produced and provides new constraints that can help refine astrophysical feedback mechanisms and models of the intracluster medium.