Papers for Wednesday, Jul 23 2025

The VASCO project has discovered groups of short-lived transients on historical photographic plates that lack conventional explanation. Hambly & Blair (2024) examined nine such transients reported by Villarroel (2021) and found that they exhibit narrower, rounder profiles, attributing this to emulsion flaws. However, well-established optical principles and atmospheric physics imply that unresolved flashes lasting less than a second naturally appear sharper and more circular than stellar images, particularly on long-exposure plates where stars are significantly blurred by seeing and tracking errors. Such profiles are an expected consequence of sub-second optical flashes, making their findings consistent with the transient interpretation.

Ongoing and future photometric surveys will produce unprecedented volumes of galaxy images, necessitating robust, efficient methods for deriving galaxy morphological parameters at scale. Traditional approaches, such as parametric light-profile fitting, offer valuable insights but become computationally prohibitive when applied to billions of sources. In this work, we propose a Conditional AutoEncoder (CAE) framework to simultaneously model and characterize galaxy morphology. Our CAE is trained on a suite of realistic mock galaxy images generated via GalSim, encompassing a broad range of galaxy types, photometric parameters (e.g., flux, half-light radius, Sersic index, ellipticity), and observational conditions. By encoding each galaxy image into a low-dimensional latent representation conditioned on key parameters, our model effectively recovers these morphological features in a disentangled manner, while also reconstructing the original image. The results demonstrate that the CAE approach can accurately and efficiently infer complex structural properties, offering a powerful alternative to existing methods.

The extended main-sequence turn-off (eMSTO) is a well-known feature observed in young and intermediate-age star clusters, characterized by a significant broadening of the main-sequence turn-off region. Although prolonged star formation and stellar rotation have been proposed as possible explanations, no consensus has yet been reached. Most previous studies have focused on high-mass clusters. In this work, we extend the analysis to the less-explored low-mass regime by investigating star clusters in the Magellanic Clouds using data from the VISCACHA survey. We employed a widely used method to quantify the MSTO width in terms of age spread. Additionally, to validate our approach, we used a cluster also observed with HST. Our analysis confirms that the eMSTO phenomenon is also present in low-mass clusters, following the known age/mass-MSTO width relations. In particular, the less massive cluster in our sample does not show an eMSTO, supporting the proposed link between the eMSTO and the escape velocity of the cluster, providing a new lower limit to the age spread of $88\pm40$ Myr for the presence of the eMSTO. The consistent MSTO width measurements between the VISCACHA and HST photometries confirm the robustness of our method and demonstrate that the age spread determination is independent of the photometric system, showing also the power of ground-based observations to investigate the eMSTO phenomenon.

Line-intensity mapping (LIM) is emerging as a powerful probe of the high-redshift Universe, with a growing number of LIM experiments targeting various spectral lines deep into the epochs of reionization and cosmic dawn. A key remaining challenge is the consistent and efficient modeling of the diverse emission lines and of the observables of different surveys. Here, we present oLIMpus, a fully analytical effective model to study LIM auto- and cross- power spectra. Our work builds on the 21-cm effective model presented in Zeus21, applying it to star-forming lines and improving it in different aspects. Our code accounts for shot noise and linear redshift-space distortions and it includes by default prescriptions for OII, OIII, H$\alpha$, H$\beta$, CII, CO line luminosities, together with the 21-cm model inherited from Zeus21. Beyond auto- and cross-power spectra, oLIMpus can produce mock coeval boxes and lightcones, and with a computational time of $\sim s$ it is ideal for parameter-space exploration and inference. Its modular implementation makes it easy to customize and extend, enabling various applications, such as MCMC analyses and consistent multi-line cross-correlations.

A significant fraction of, and possibly all, stars form in binary or multiple systems. For Solar-mass stars in the Galactic field, the distribution of orbital separations is log-normal over seven orders of magnitude, from $10^{-2} - 10^5$ au. In contrast, the separation distributions of systems in nearby star-forming regions paints a much more confusing picture. There appears to be an excess of systems in the separation range 10 - 1000 au, and recent high-resolution spectroscopic observations of close (<10 au) systems suggest a field-like distribution in some star-forming regions, but a possible excess with respect to the field in other regions. Furthermore, the resolution limit of numerical simulations of binary star formation is $\sim$1\,au, and consequently comparisons with the binary distributions in star-forming regions and in the field are restricted. In this paper, we demonstrate that these observational uncertainties, and limitations in the simulations, are potentially a much bigger problem than previously realised. We show that the log-normal separation distribution in the field can be reproduced by combining constituent binary populations whose initial separation distributions have a very different form to a log-normal. We also argue that the observed excess of binaries in the range 10 - 62 au in the ONC compared to the Galactic field is not necessarily inconsistent with the field population, because the ONC is only one of many star-forming regions that populate the field. We propose that further observations of spectroscopic binaries in star-forming regions to probe and complete the <10 au parameter space are urgently needed.

Hydrogen/Helium-poor stripped-envelope core-collapse supernovae with broad lines (SNe Ic-bl) almost always accompany the nearby ($z < 0.3$) jetted relativistic explosions known as long duration gamma-ray bursts (GRBs). However, the majority of SNe Ic-bl have no detected GRB counterpart. At least some of these SNe should harbor off-axis jets, whose afterglow may become detectable at late times, particularly at radio wavelengths. Here, we present Karl G. Jansky Very Large Array radio observations (rest frame times of $\sim 3$-$4\times10^{3}$ days post SN discovery) of a sample of 14 SNe Ic-bl discovered by the Palomar Transient Factory (PTF) that have been demonstrated to originate from the same host environments as the SNe Ic-bl associated with nearby GRBs. Of the 14 SNe, we identify three that are radio detected, one of which (PTF10tqv, $z = 0.0795$) is consistent with an off-axis jet with energy similar to classical GRBs ($\gtrsim 10^{50.5}~$erg). Using recently developed synchrotron radiation code, we find that for our 11 non-detections, which are among the deepest limits obtained for Ic-bl, we rule out an off-axis jet with an energy of $\gtrsim 10^{51}~{\rm erg}$ in circumburst densities of $\gtrsim 10^{-1}~{\rm cm}^{-3}$. We predict that well-spaced monitoring of newly discovered SNe Ic-bl from $\sim 10~$days to $\sim 10~$years (rest frame) to luminosities of $\sim 10^{27}~{\rm erg~s}^{-1}~{\rm Hz}^{-1}$ will constrain the existence of highly off-axis jets ($\gtrsim60^\circ$) with classical GRB energies. The VLA Sky Survey will probe jets that are $\lesssim 60^\circ$ off-axis, whereas the Deep Synpotic Array 2000 will probe jets out to $\sim 90^\circ$ off-axis, demonstrating the importance of utilizing radio surveys to supplement targeted observations.

We report new spectroscopic and interferometric observations of the Pleiades binary star Atlas, which played an important role nearly three decades ago in settling the debate over the distance to the cluster from ground-based and space-based determinations. We use the new measurements, together with other published and archival astrometric observations, to improve the determination of the 291-day orbit and the distance to Atlas ($136.2 \pm 1.4$ pc). We also derive the main properties of the components, including their absolute masses ($5.04 \pm 0.17 M_{\odot}$ and $3.64 \pm 0.12 M_{\odot}$), sizes, effective temperatures, projected rotational velocities, and chemical composition. We find that the more evolved primary star is rotationally distorted, and are able to estimate its oblateness and the approximate orientation of its spin axis from the interferometric observations. The spin axis may well be aligned with the orbital axis. Models of stellar evolution from MESA that account for rotation provide a good match to all of the primary's global properties, and point to an initial angular rotation rate on the zero-age main sequence of about 55% of the breakup velocity. The current location of the star in the H-R diagram is near the very end of the hydrogen-burning main sequence, at an age of about 105 Myr, according to these models. Our spectroscopic analysis of the more slowly-rotating secondary indicates that it is a helium-weak star, with other chemical anomalies.

By comparing Cepheid brightnesses with geometric distance measures including Gaia EDR3 parallaxes, most recent analyses conclude metal-rich Cepheids are brighter, quantified as $\gamma \sim -0.2$ mag/dex. While the value of $\gamma$ has little impact on the determination of the Hubble constant in contemporary distance ladders (due to the similarity of metallicity across these ladders), $\gamma$ plays a role in gauging the distances to metal-poor dwarf galaxies like the Magellanic Clouds and is of considerable interest in testing stellar models. Recently, Madore & Freedman (2025, hereafter MF25) recalibrated Gaia EDR3 parallaxes by adding to them a magnitude offset to match certain historic Cepheid parallaxes which otherwise differ by $\sim1.6\sigma$. A calibration which adjusts Gaia parallaxes by applying a magnitude offset (i.e., a multiplicative correction in parallax) differs significantly from the Gaia Team's calibration (Lindegren et al. 2021), which is additive in parallax space - especially at distances much closer than 1 kpc or beyond 10 kpc, outside the $\sim$2-3 kpc range on which the MF25 calibration was based. The MF25 approach reduces $\gamma$ to zero. If extrapolated, it places nearby cluster distances like the Pleiades too close compared to independent measurements, while leaving distant quasars with negative parallaxes. Further, by shortening the Milky Way distance scale, the MF25 calibration raises the local Hubble constant by $\sim$1 km/s/Mpc, increasing the Hubble tension significantly. We conclude that the MF25 proposal for Gaia calibration and $\gamma \sim 0$ produces farther-reaching consequences, many of which are strongly disfavored by the data.

Gamma-ray bursts (GRBs) offer a powerful window to probe the progenitor systems responsible for the formation of heavy elements through the rapid neutron capture (r-) process, thanks to their exceptional luminosity, which allows them to be observed across vast cosmic distances. GRB 241105A, observed at a redshift of z = 2.681, features a short initial spike (1.5 s) and a prolonged weak emission lasting about 64 s, positioning it as a candidate for a compact binary merger and potentially marking it as the most distant merger-driven GRB observed to date. However, the emerging ambiguity in GRB classification necessitates further investigation into the burst's true nature. Prompt emission analyses, such as hardness ratio, spectral lag, and minimum variability timescales, yield mixed classifications, while machine learning-based clustering places GRB 241105A near both long-duration mergers and collapsar GRBs. We conducted observations using the James Webb Space Telescope (JWST) to search for a potential supernova counterpart. Although no conclusive evidence was found for a supernova, the host galaxy's properties derived from the JWST observations suggest active star formation with low metallicity, and a sub-kpc offset of the afterglow from the host, which appears broadly consistent with a collapsar origin. Nevertheless, a compact binary merger origin cannot be ruled out, as the burst may plausibly arise from a fast progenitor channel. This would have important implications for heavy element enrichment in the early Universe.

We explore the neutral hydrogen (H I) gas around 1.9 < z < 3.5 Lyman Alpha Emitters (LAEs) from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) using faint Ly$\alpha$ absorption. This absorption is the result of H I in the halo of the LAE scattering Ly$\alpha$ photons from the integrated light of background galaxies along the line of sight. We stack millions of spectra from regions around ~88,000 LAEs to focus on the physics of the gas at large radii. The extensive number of fiber spectra contributing to the stacks ensures significant signal-to-noise ratio (S/N) to detect the faint Ly$\alpha$ absorption which would otherwise be buried within the noise. We detect absorption out to a projected ~350 kpc around an average LAE at z~2.5. We use these results to create an empirical radial $W_\lambda$(Ly$\alpha$) profile around LAEs. Comparison with numerical simulations reveals a profile similar to the empirical one within this region. Compared to previous studies, the profile is similar but modestly higher. We also outline a simple physical picture motivated by the observed trends in the data. We plan to quantify this radial profile as a function of redshift, local density, and Ly$\alpha$ luminosity to explore the relationship between LAE environments and H I distribution.

Using combined data from SDSS-IV/APOGEE and Gaia, we study the chemo-dynamical properties of the Splash population in comparison with those of the high-alpha disc. We investigate a wide range of abundance ratios, finding that the Splash differs from the high-alpha disc overall. However, these differences result from a smooth variation of chemical compositions as a function of orbital properties. The Splash occupies the high-alpha, high-[Al,K/Fe], and low-[Mn/Fe] end of the high-alpha disk population. In agreement with previous studies, we find that Splash stars are distributed over large heights from the Galactic mid-plane. To further elucidate the relation between the Splash and the high-alpha disk, we turn to simulations. Using a sample of Milky Way-like galaxies with and without major accretion events from the ARTEMIS simulations, we find that Splash-like populations are ubiquitous, though not always resulting from major mergers. Lower mass progenitors can also generate Splash-like features, as long as they are on retrograde orbits. Moreover, we find a strong correlation between the mass fraction of Splash stars and the fraction of retrograde accreted stars in the disk. Some galaxies with minor (retrograde) mergers contain more pronounced Splash populations than others with major, but prograde, mergers. For stars in the high-alpha disks, we also find a decrease in the [alpha/Fe] with increasing orbital angular momentum. This trend is found in hosts with both major or minor mergers. Our results suggest that a number of relatively low-mass mergers on retrograde orbits could result in populations that are qualitatively similar to the Splash.

The dominant formation channel of Type Ia supernovae (SNe Ia) has been extensively studied for many years. Several hypervelocity white dwarfs (HVWDs) with space velocities of $\gtrsim 1000\,\mathrm{kms}^{-1}$ have recently been discovered. One possible origin of these stars is the dynamically-driven double-degenerate double-detonation (D6) scenario, in which an accreting sub-Chandrasekhar mass carbon-oxygen (CO) WD detonates as a SN Ia. In this scenario, the less massive WD may survive its companion's detonation and be ejected as a HVWD. Most of the observed HVWDs are hotter and puffier than normal WDs, perhaps due to their recent proximity to a SN. In this work, we test whether these properties can be explained by long-lived stable carbon (C) burning in the interiors of CO WD donors triggered by a SN shock. We model the long-term evolution of CO WDs following rapid energy injection using 1D models. We find that stable C burning can be ignited in CO WDs with masses of $0.95 - 1.10\,M_{\odot}$ if SN energy penetrates sufficiently deeply. The resulting born-again stars settle on the C-burning main sequence while they convert their interiors from C and O to Ne and Mg, where they have temperatures and radii similar to some of the observed HVWDs. However, the timescale over which C-burning WDs remain inflated is $\lesssim 10^5\,$yr, which is at least an order of magnitude shorter than the kinematic ages of observed hot HVWDs. We conclude that observed HVWDs are unlikely to be inflated by C burning. The stellar evolution of observed HVWDs remains an open problem.

The extreme-ultraviolet (EUV; 100 -- 911 Å) spectra of F, G, K, and M stars provide diagnostics of the stellar chromosphere through the corona, with line and continuum formation temperatures spanning roughly 10$^{4}$ - 10$^{7}$ K. The EUV stellar spectrum in turn drives atmospheric photochemistry and numerous escape processes on orbiting planets. We present a new study of the EUV history of solar-type stars, using new and archival {\it Hubble Space Telescope} observations of solar analogs (T$_{\odot}$ $\pm$ 150 K for stars older than 100 Myr) and ``Young Suns" (age $<$ 100 Myr) that will evolve into main sequence early G-type stars to predict the 90 -- 360 Å EUV flux from a sample of 23 stars. We find that the EUV activity evolution for solar-type stars follows a two-component behavior: a saturated L(EUV)/L$_{bol}$ plateau (at a level of about 10$^{-4}$) followed by a power law decay ($\alpha$ $\approx$ $-$1.1) after ages of $\approx$ 50 -- 100 Myr. Consequently, the EUV flux incident at 1 AU around solar analogs varies over the lifetime of the Sun, ranging from 100 $\times$ the present day UV irradiance at 10 Myr to 0.3 $\times$ the present-day level at 10 Gyr. We find that the EUV luminosity is approximately the same as the soft X-ray luminosity up to approximately 1 Gyr, after which the EUV luminosity of the stars dominate. In comparison to Sun-like stars, the EUV saturation level of early/mid M dwarfs is several times higher and lasts $\sim$10 -- 20 times longer.

Massive stars less massive than ~30 Msol evolve into a red supergiant after the main sequence. Given a standard IMF, this means about 80% of all single massive stars will experience this phase. RSGs are dominated by convection, with a radius that may extend up to thousands of solar radii. Their low temperature and gravity make them prone to lose large amounts of masses, either through a pulsationally-driven wind or through mass-loss outburst. RSGs are the progenitors of the most common core-collapse supernovae, the type II. In the present review, we give an overview of our theoretical understanding about this spectacular phase of massive stars evolution.

The red and yellow hypergiants are a rare and important phase in the evolution of the most massive stars that can reach the cool part of the HR Diagram. The hypergiant phase is commonly characterized by high, often episodic mass-loss rates and significant changes in spectral type, probably due to the formation of a pseudo photopsphere during a high mass-loss episode. Many of the yellow hypergiants are the immediate successors to the most luminous red supergiants, and often show evidence in their dusty, circumstellar envelopes from past red supergiant activity. In this paper we review the yellow and red hypergiants with an emphasis on how they differ from more normal red supergiants.

We present a catalogue of optical and near-infrared counterparts to radio sources detected in the Euclid Deep Field North (EDF-N) using observations from the LOw-Frequency ARray (LOFAR) High Band Antenna (HBA) at 144 MHz with 6 arcsec angular resolution. The catalogue covers a circular region of $10deg^2$ and includes 23309 radio sources with a peak signal-to-noise ratio greater than 5. After masking regions close to stars and with unreliable photometry in the optical or near-infrared, the catalogue includes 19550 sources. To carry out a robust identification strategy, we combined the statistical power of the Likelihood Ratio (LR) method, including both colour and magnitude information, with targeted visual inspection. The resulting catalogue boasts a remarkable identification rate of 99.2%, successfully matching 19401 out of 19550 radio sources with reliable optical and/or near-infrared counterparts. For 19391 of the matched sources, we successfully derived photometric redshift for the host galaxy by performing an SED fit using the available data in the optical, near-infrared, far-infrared, and radio. LOFAR sources within the catalogue exhibit a median redshift of 1.1, with some extending up to z=6. Around 7% of the sample is detected only in infrared using IRAC and tends towards higher redshifts, with a median of z=3.0. This comprehensive catalogue serves as a valuable resource for future research, enabling detailed investigations into the properties and evolution of LOFAR-detected sources and their host galaxies.

Identifications of red supergiants (RSGs) in the Milky Way and nearby galaxies have experienced an exponential increase in recent years, driven by advancements in selection techniques, the continued expansion of archival datasets, and a steady increase in spectroscopic data. This review describes the advances in methodologies and selection criteria for identifying RSGs and presents the current census of these stars in our own Galaxy and nearby galaxies. It also describes the insights gained from resolving nearby RSGs and their complex circumstellar material in the Milky Way and from the growing samples of RSGs being discovered in the Local Group and beyond. These advances impact the Humphreys--Davidson limit in the cool part of the Hertzsprung--Russell diagram. Furthermore, they provide insight into extreme RSGs and the role of photometric variability and, in particular, of the newly discovered phenomenon of dimming events. Recent observations have enabled the determination of the binarity fraction among RSGs, offering new constraints to stellar evolution. Looking ahead, the synergy between large-scale surveys, high-resolution observations, and emerging machine-learning tools promises to further transform our understanding of the final evolutionary stages of massive stars in the coming decade.

Red supergiants are the largest stars known with some of the highest mass loss rates observed. They are the final stage in the evolution of the majority of massive stars. The unexpected discovery of high mass loss episodes in many red supergiants have posed questions about the role of mass loss on their final stages. The papers in this volume are timely reviews of our current understanding of this often surprising population of massive stars. This introductory paper is a brief summary of their observed properties and a historical perspective on some of the current problems on mass loss, their circumstellar environments, and their evolutionary state.

The behavior of the bright red supergiant, Betelgeuse, is described with results principally from the past 6 years. The review includes imaging, photometry, and spectroscopy to record the Great Dimming of 2019--2020. This event was followed by a slow ongoing recovery from the massive surface mass ejection after which the stellar characteristics changed. Theoretical simulations address the cause of this episodic mass ejection and the optical Dimming. Recent publications evaluating the perplexing 2100 day periodicity in the star's brightness and radial velocity provide evidence that Betelgeuse may harbor a companion object. Current attempts at direct detection of this companion are discussed. Betelgeuse provides a well-studied and meaningful example for supergiant stars in our Galaxy and others.

The latest detection of GW231123, a binary black hole (BH) merger with exceptionally large masses and high spins for the incoming components, has been suggested as a smoking gun for hierarchical formation. In this scenario, a first generation of BHs resulting from collapsing stars form in a dense environment. Here they can assemble dynamically and undergo subsequent mergers. We discuss three challenges for the formation of a GW231123-like event inside a star cluster: 1) The high masses of the incoming BHs appear to be in the predicted pair-instability mass gap and thus suggest that second-generation or higher-order generation BHs are involved. 2) Very high spins ($\chi_f \gtrsim 0.8$) are very unlikely for dynamically assembled BHs because of the isotropic distribution of spin vectors. 3) Hierarchically formed BHs are susceptible to receive large recoils, which could kick them out of their cluster. We simulate this scenario and show that only a few percent of mergers recover remnants within GW231123's primary spin estimate $\chi_1=0.9^{+0.10}_{-0.19}$ and are retained inside typical star clusters. A large fraction of very rapidly spinning second-generation BHs (including $\chi_f>0.9$) can only form if the first-generation BHs merges with aligned spins. This is a natural outcome of massive binary star evolution scenarios, such as a chemically homogeneous evolution. This scenario also predicts equal masses for the components, implying that the resulting BHs tend to receive very low recoil kicks and would therefore likely be retained inside a cluster. We conclude that GW231123-like events, if formed in a star cluster, could require first-generation BHs with large aligned spins that evolved through stellar binary interaction, followed by the dynamical assembly for a subsequent merger. We discuss the implications for the uncertain lower edge of the putative mass gap 60-130 $\rm M_\odot$.

The envelopes of Red Supergiants (RSGs) have a unique chemical environment not seen in other types of stars. They foster an oxygen-rich synthesis but are tempered by sporadic and chaotic mass loss, which distorts the envelope and creates complex outflow sub-structures consisting of knots, clumps, and arcs. Near the stellar photosphere, molecules and grains form under approximate LTE conditions, as predicted by chemical models. However, the complicated outflows appear to have distinct chemistries generated by shocks and dust destruction. Various RSG envelopes have been probed for their molecular content, mostly by radio and millimeter observations; however, VY Canis Majoris (VY CMa) and NML Cygni (NML Cyg) display the highest chemical complexity, and also the most complicated envelope structure. Thus far, over 29 different molecules have been identified in the envelopes of RSGs. Some molecules are common for circumstellar gas, including CO, SiO, HCN and H$_2$O, which have abundances of $\sim$$10^{-6}$--$10^{-4}$, relative to H$_2$. More exotic oxides have additionally been discovered, such as AlO, AlOH, PO, TiO$_2$, and VO, with abundances of $\sim$$10^{-9}$--$10^{-7}$. RSG shells support intricate maser emission in OH, H$_2$O and SiO, as well. Studies of isotope ratios in molecules suggest dredge-up at least into the H-burning shell, but further exploration is needed.

This review discusses the causes, nature, importance and observational evidence of mass loss by red supergiants. It arrives at the perception that mass loss finds its origin in the gravity which makes the star a star in the first place, and is a mechanism for the star to equilibrate. This is corroborated by a careful examination of various popular historical and recent empirical mass-loss rate prescriptions and theoretical works, and which provides no evidence for an explicit dependence of red supergiant mass loss on metallicity though dust-associated mass loss becomes less prevalent at lower metallicity. It also identifies a common problem in methods that use tracers of mass loss, which do not correct for varying scaling factors (often because there is no information available on which to base such correction) and as a result tend to underestimate mass-loss rates at the lower end. Conversely, dense, extended chromospheres in themselves do not translate into high mass-loss rates, and the significance of stochastic mass loss can be overstated. On a population scale, on the other hand, binary interaction acts as a stochastic agent of mass loss of great import. In all, evidence is overwhelming that points at red supergiants at the lower mass end losing mass at insufficient rates to shed their mantles before core collapse, but massive (at birth) red supergiants to be prone to intense, dusty mass loss which sees them become hotter stars before meeting their fate. This is consistent with the identified progenitors of hydrogen-rich supernovae. Supernova evolution holds great promise to probe the mass loss but we caution against confusing atmospheres with winds. Finally, promising avenues are looked into, which could forge step-change progress in what has been a long and arduous search for the holy grail of red supergiant mass loss. We may yet find it!

The inevitable fate of massive stars in the initial mass range of ~8--30 M_{Sun} in the red supergiant (RSG) phase is a core-collapse supernova (SN) explosion, although some stars may collapse directly to a black hole. We know that this is the case, since RSGs have been directly identified and characterized for a number of supernovae (SNe) in pre-explosion archival optical and infrared images. RSGs likely all have some amount of circumstellar matter (CSM), through nominal mass loss, although evidence exists that some RSGs must experience enhanced mass loss during their lifetimes. The SNe from RSGs are hydrogen-rich Type II-Plateau (II-P), and SNe II-P at the low end of the luminosity range tend to arise from low-luminosity RSGs. The typical spectral energy distribution (SED) for such RSGs can generally be fit with a cool photospheric model, whereas the more luminous RSG progenitors of more luminous SNe II-P tend to require a greater quantity of dust in their CSM to account for their SEDs. The SN II-P progenitor luminosity range is log(L_{bol}/L_{Sun}) ~ 4.0--5.2. The fact RSGs are known up to log(L_{bol}/L_{Sun}) ~ 5.7 leads to the so-called ``RSG problem'', which may, in the end, be a result of small number of available statistics to date.

We present the results obtained from the spectral and temporal study of thermonuclear bursts from the millisecond X-ray pulsar SRGA J144459.2-604207 detected with NICER. The dynamic evolution of the spectral parameters in a broad energy range is also investigated during a simultaneously detected burst with XMM-Newton and NuSTAR. The burst profiles exhibit a strong energy dependence, as observed with XMM-Newton, NICER, and NuSTAR. We investigated the reflection feature during these bursts using the disk reflection model. As observed during the peak of the NICER bursts, the reflection model can contribute 30 per cent of the overall emission. During the NICER bursts, a correlation is observed between the flux of the blackbody and the reflection components. The measurements of the mass accretion rate indicate that the bursts may be powered by a mixed H/He fuel. Moreover, the broadband NICER and NuSTAR spectra are also used to probe the reflection signature in the burst-free persistent region using the relativistic reflection model. Based on the variability of the count rate during the NuSTAR observation, we also investigate the evolution of spectral parameters during two different flux levels of the NuSTAR observation. The inner disk radius (Rin) and the angle of inclination are found to be nearly 11 Rg and 50 degrees, respectively. The magnetic field strength at the poles of the neutron star is estimated to be 6 x 10^8 G, assuming that the inner disk is truncated at the magnetospheric boundary.

Our understanding of cosmology is shaped by Type Ia supernovae (SNe Ia), the runaway thermonuclear detonations of white dwarfs via accretion from a companion star. The nature of this companion star is highly debated, with disparate models explaining currently available SNe Ia data. Critical ultraviolet (UV) signatures of SNe Ia progenitors are only observable within the first few days post-detonation. We present the instrument design of UVIa, a proposed SmallSat to make early UV observations of SNe Ia. UVIa conducts simultaneous observations in three photometric channels: far-UV (1500 - 1800 Å), near-UV (1800 - 2400 Å), and Sloan $u$-band (3000 - 4200 Å). UVIa employs two 80 mm double-offset Cassegrain UV telescopes and a similar 50 mm $u$-band telescope, imaging onto three Teledyne e2v CIS120-10-LN CMOS detectors. The UV detectors are delta-doped for enhanced sensitivity, with custom metal-dielectric filters providing further in-band efficiency and red light rejection. The UV optics utilize multi-layer coatings, defining the UV bandpasses and providing additional red light rejection. The instrument design achieves high UV sensitivity (21.5 mag AB) and superior red light rejection ($<$ 10$^{-5}$ throughput), allowing UVIa to make early observations of SNe Ia while serving as a pathfinder for future UV transient telescopes.

The recent detection of TeV neutrino sources by the IceCube Neutrino Observatory demonstrates the detector's advanced capabilities in detecting high-energy astrophysical neutrinos. At lower energies, down to the GeV range, a variety of transient phenomena, such as novae, supernovae, and gamma-ray bursts, are expected to emit neutrinos. Observations of these neutrinos can provide unique insights into processes below the photosphere and offer clues to identifying their emission mechanisms. We have searched for these neutrinos intensively with IceCube's existing infill array, DeepCore. Although no significant detections have been made, strong constraints on astrophysical environments in these transients, such as the baryon loading factor in gamma-ray bursts, have been obtained. A denser infill array, called the IceCube Upgrade, will enhance sub-TeV neutrino searches with its unprecedented sensitivity to GeV neutrinos. The Upgrade, set to be deployed in the 2025-2026 South Pole season, will consist of seven new strings, adding approximately 700 novel optical modules with multiple photomultiplier tubes in the DeepCore volume. The denser arrangement of high-efficiency modules will significantly improve IceCube's sensitivity between 1 GeV and 1 TeV. We present an initial assessment of the astrophysical capabilities of the IceCube Upgrade, using preliminary simulated data and an event selection similar to that used for DeepCore. We explore the detectability of GeV neutrino transients compared to DeepCore and discuss potential sensitivity enhancements through advanced detector simulations and optimized analysis techniques, including refined triggering conditions and event selection criteria.

Fluctuations and structure across a wide range of spatial and temporal scales are frequently studied in the solar wind. The properties of the low-frequency fluctuations are of relevance to turbulent energy injection into the plasma and the transport of high-energy cosmic rays. Correlation analysis of decade-long intervals of interplanetary data permits study of fluctuations at time scales much longer than suitably defined correlation times, and therefore at frequencies well below those associated with the Kolmogorov inertial range of in situ turbulence. At the frequencies of interest, we study the familiar occurrence of the 1/f spectral signature. We also study point spectral features due to solar rotation and their relation with the 1/f signal. We report novel properties at timescales ranging from minutes up to years, using data selected by wind speed, phase of solar cycle, and cartesian components of the magnetic field. A surprising finding is that the power in solar rotation harmonics is consistent with an extension of the 1/f spectrum, down to frequencies as low as around 5e-7 Hz. The presence of a broadband 1/f spectrum across different wind types supports the interpretation that 1/f signals may be related to or even originate from the solar dynamo.

Pebble accretion provides new insights into Earth's building blocks and early protoplanetary disk conditions. Here, we show that mixtures of chondritic components: metal grains, chondrules, calcium-aluminum-rich inclusions (CAIs), and amoeboid olivine aggregates (AOAs) match Earth's major element composition (Fe, Ni, Si, Mg, Ca, Al, O) within uncertainties, whereas no combination of chondrites and iron meteorites does. Our best fits also match the $\epsilon^{54}$Cr and $\epsilon^{50}$Ti values of Earth precisely, whereas the best fits for chondrites, or components with a high proportion of E chondrules, fail to match Earth. In contrast to some previous studies, our best-fitting component mixture is predominantly carbonaceous, rather than enstatite chondrules. It also includes 15 wt% of early-formed refractory inclusions (CAIs + AOAs), which is similar to that found in some C chondrites (CO, CV, CK), but notably higher than NC chondrites. High abundances of refractory materials are lacking in NC chondrites, because they formed after the majority of refractory grains were either drawn into the Sun or incorporated into terrestrial protoplanets via pebble accretion. We show that combinations of Stokes numbers of chondritic components build 0.35-0.7 Earth masses in 2 My in the Hill regime accretion, for a typical pebble column density of 1.2 kg/m2 at 1 au. However, a larger or smaller column density leads to super-Earth or moon-mass bodies, respectively. Our calculations also demonstrate that a few My of pebble accretion with these components yields a total protoplanet mass inside 1 au exceeding the combined masses of Earth, Moon, Venus, and Mercury. Accordingly, we conclude that pebble accretion is a viable mechanism to build Earth and its major element composition from primitive chondritic components within the solar nebula lifetime.

Modern time-domain surveys like the Zwicky Transient Facility (ZTF) and the Legacy Survey of Space and Time (LSST) generate hundreds of thousands to millions of alerts, demanding automatic, unified classification of transients and variable stars for efficient follow-up. We present AppleCiDEr (Applying Multimodal Learning to Classify Transient Detections Early), a novel framework that integrates four key data modalities (photometry, image cutouts, metadata, and spectra) to overcome limitations of single-modality classification approaches. Our architecture introduces (i) two transformer encoders for photometry, (ii) a multimodal convolutional neural network (CNN) with domain-specialized metadata towers and Mixture-of-Experts fusion for combining metadata and images, and (iii) a CNN for spectra classification. Training on ~ 30,000 real ZTF alerts, AppleCiDEr achieves high accuracy, allowing early identification and suggesting follow-up for rare transient spectra. The system provides the first unified framework for both transient and variable star classification using real observational data, with seamless integration into brokering pipelines, demonstrating readiness for the LSST era.

This report presents a draft of a new detector designed to determine the chemical composition of primary cosmic rays based on the characteristics of the angular distribution of Cherenkov light from EAS. The installation, consisting of several such detectors, will be able to register individual EAS events in the energy range from 1 to 1000 PeV with high angular resolution of up to 0.2$^\circ$. The proposed detector's distinctive feature is its simple design and wide viewing angle of above $\pm30^\circ$.

The action of gravitational physics across space-time creates observable signatures in the behaviour of light and matter. We perform combined-probe studies using data from the Baryon Oscillation Spectroscopic Survey (BOSS) and Dark Energy Spectroscopic Instrument survey Data Release 1 (DESI-DR1), in combination with three existing weak lensing surveys, to test and constrain General Relativity (GR) in the context of the standard model of cosmology (LCDM). We focus on measuring the gravitational estimator statistic, E_G, which describes the relative amplitudes of weak gravitational lensing and galaxy velocities induced by a common set of overdensities. By comparing our amplitude measurements with their predicted scale- and redshift-dependence within the GR+LCDM model, we demonstrate that our results are consistent with the predictions of the Planck cosmology. The redshift span of the DESI dataset allows us to perform these E_G measurements at the highest redshifts achieved to date, z ~ 1.

The progress in the development of the SPHERE-3 project is reported. The capabilities of the reflected Cherenkov light telescope and the direct light detector are stated. The procedures for separate EAS primary parameter assessment are mentioned. The advantage of dual atmospheric detection is underlined. An idea of the self consistent overall procedure is revealed.

The SPHERE-3 setup is destined to register the EAS Cherenkov light, both the direct and the reflected from the snow surface. A set of methods and new approaches in the measurement technique enable substantial progress in the study of the primary cosmic ray composition in the energy range 1--1000 PeV. The present work reveals the current status of the project development and detector performance modelling.

The combination of the $z=0-13.5$ cosmic star formation history and active galactic nuclei (AGN) luminosity history as inferred by the James Webb Space Telescope is connected to the cosmic spectral energy distribution (CSED) to explore the sources of reionisation. We compute the redshift evolution of the corresponding cosmic ionising photon emissivity, the neutral fraction and the cosmic microwave background optical depth. We use the generative SED modelling code ProSpect to bracket the ionising emissivity between escape fractions of $f_{\mathrm{esc}} = 1 - 100\%$ for both the stars and AGN. Stars alone could have achieved reionisation by $z\approx 6$ with $f_{\mathrm{esc}} \gtrsim 10-30\%$, depending on the metallicity. On the other hand, AGN by themselves would have struggled to produce sufficiently many ionising photons even with $f_{\mathrm{esc}} = 100\%$. A hybrid model containing both stars and AGN is explored where we find best fit (median$\pm 1\sigma$) $f_{\mathrm{esc}}= 12\%$ ($12^{+10}_{-11}\%$) for the stars and $f_{\mathrm{esc}}= 63\%$ ($79^{+21}_{-44}\%$) for the AGN, maintained at all redshifts. In essence, the joint growth of stellar mass and super massive black holes produces neither more or less ionising photons than needed to reionise $\gtrsim 99\%$ of the intergalactic medium by $z\approx 6$.

The discrepancy between the early-time estimation and late-time observation on the cosmic baryon content - the 'missing baryon problem' - is a longstanding problem in cosmology. Although recent studies with fast radio bursts (FRBs) have largely addressed this discrepancy, the precise spatial distribution of these baryons remains uncertain due to the effect of galaxy feedback. Cosmological hydrodynamical simulations such as Simba have shown that the partitioning of baryons between the intergalactic medium (IGM) and haloes is sensitive to feedback models, motivating the connection of baryon distribution with feedback physics. With the Simba simulation suite, this study investigates how feedback affects the distribution of matter within large-scale cosmic structures, with implications for FRB foreground modeling. We apply the T-web method to classify the cosmic web into different structures: knots, filaments, sheets, and voids. We then analyze how the different feedback variants of Simba affect the distribution of matter within each structure. Our results show that in Simba, the fractions of IGM gas in different cosmic web structures vary only a few percent under different feedback models. However, jet feedback produces noticeable changes in the gas distribution within structures, enhancing the diffuse IGM on the outskirts of filaments and knots. This research provides a new perspective on the impact of feedback on the IGM and motivates a refined data model for the FRB foreground mapping.

Supra-arcade downflows (SADs) are dark, sunward-moving structures above the arcade of flare loops. Naturally they are considered to be associated with outflows resulting from magnetic reconnection at the vertical current sheet beneath the eruptive structure. Despite the extensive investigations on the SAD properties, the timing information, particularly the waiting time between consecutive SADs, has not been systematically examined. Here, using the 131~Å passband of the Atmospheric Imaging Assembly on-board the Solar Dynamics Observatory, we studied the waiting time distribution (WTD) of SADs in 7 eruptive flares. In six of the 7 flares, the SADs are identified and tracked in previous studies, by two different methods; and in the 7th flare, by our optimized manual method. Based on statistical evaluations, we found that most of the WTDs are best fitted by a power-law function with the slope ranging from 1.7 to 2.4, in accordance with the prediction of non-stationary Poisson processes or self-organized criticality; but often they can also be fitted almost equally well by a log-normal function. These results rule out linear random or quasi-periodic processes to be responsible for the generation of SADs, but suggest that several nonlinear mechanisms be coupled together in the reconnection outflow region to shape the heavy-tailed WTD of SADs.

We present an analysis of CO rovibrational emission lines in the 183 infrared spectra of nearby Class II objects obtained with the NIRSPEC instrument on the Keck II telescope over the past two decades. The sample includes a broad range of stellar mass (both T Tauri and Herbig Ae/Be) and disk evolutionary states (from full to debris disks). We find that 53% of the sample has CO rovibrational emission lines present in their spectrum with disk/stellar subtype detection rates of 82% for transition disks, 61% for Herbigs, and 77% for CTTSs. Although there is no discernible difference between T Tauri and Herbig Ae/Be star CO detection rates, the detection of accretion and of CO are statistically correlated in T Tauri stars but not in Herbig Ae/Be objects. Within the sample of T Tauri stars, we find that no weak-line T Tauri stars have CO rovibrational emission lines. We use slab modeling to analyze the density, temperature, and emitting area of the sample. The retrieval results imply that Herbig Ae/Be objects tend to have cooler and larger CO emitting regions than T Tauri stars. We find that the CO emitting area is not a thin ring as defined by temperature, but a ring of varying size likely dependent on the structure of the disk. We also present guidelines on how to approach CO rovibrational emission lines in JWST spectra and present methods for linking ground-based observations with JWST spectra. This includes line-to-continuum ratio estimates based on stellar mass and accretion rate.

Compact, low-mass galaxies with strong nebular emission are considered promising candidates for efficient ionizing photon production and escape. We present a spatially resolved analysis of 189 galaxies at redshifts $z \sim 6.7-7.6$ in JADES GOODS-N and GOODS-S fields and selected via JWST/NIRCam F410M filter. By employing annular photometry and spectral energy distribution fitting across rest-frame UV to optical wavelengths, we investigate the internal structure of star formation, ionizing photon production and escape, as well as the resolved star formation histories within these galaxies. We find that these galaxies exhibit compact, centrally concentrated, and bursty star formation, especially in lower-mass systems ($\log(M_*/{\rm M_{\odot}}) <9.0$). The central regions of them display extreme [OIII]+H$\beta$ equivalent widths ($>$1000 Å), high ionizing photon production efficiencies ($\xi_{\text{ion}} \sim 10^{25.6}$ Hz erg$^{-1}$), steep UV slopes ($\sim -2.3$), and elevated escape fractions ($f_{\text{esc}} > 0.08$), with all these properties peaking in the inner regions. These findings reveal outside-in growth and rising star formation histories at $z\sim 7$, with the central regions of them playing a pivotal role in driving cosmic reionization.

The chemical evolution history of the Small Magellanic Cloud (SMC) is complex and is best understood through a comprehensive analysis of star clusters across its various regions. The VISCACHA survey aims to fully explain the chemical evolution of SMC star clusters by analyzing different sub-regions adopted from an existing framework. The west halo (WH) region, which contains the oldest and most metal-poor stellar populations, exhibits a clear age-metallicity relation (AMR) with minimal dispersion. This region shows a significant dip of ~0.5 dex in metallicity approximately 6 Gyr ago. This was likely caused by a major merger event that subsequently accelerated the star formation rate. Clusters in the Southern Bridge (SB) and Northern Bridge regions of the SMC may have experienced distinct chemical enrichment histories, as suggested by our previous works but with limited data coverage. Furthermore, the AMR of wing/bridge (W/B) shows no sign of enrichment caused by the aforementioned merger event, but exhibits signatures of the recent collisions between the clouds contemporaneous with the epochs of the Magellanic Stream and Bridge formations. In this study, we present an updated AMR for the SB region based on a sample that includes approximately 67% of its known clusters. Contrary to the expectation of a very unique chemical evolution history, these SB clusters show a trend similar to the one of the WH clusters. The chemical evolution models that best fit the AMR trend of the SB clusters show excellent agreement with the major merger model proposed for the WH clusters. Building on this, we suggest a new unified chemical evolution model for both the WH and SB clusters, which can be explained by a major merger at ~6 Gyr followed by episodic chemical enrichment over time.

NGC 4258 is a prime target for studying feedback in Low-Luminosity Active Galactic Nuclei (LLAGNs) due to its proximity and comprehensive multi-wavelength coverage. Using new Integral Field Spectroscopy (IFS) data from SITELLE at the Canada-France-Hawaii Telescope, we analysed the galaxy's nebular emission lines. Our study focused on spatially resolved line ratios and Baldwin-Phillips-Terlevich diagrams, revealing that the ''anomalous spiral arms'' exhibit intense interactions between the jet and interstellar medium (ISM) extending up to 6 kpc with velocity dispersions peak at 200-250 km/s in these regions, contrasting with star-forming areas showing lower values around of 30-50 km/s. Analysis of covering fractions indicates heightened AGN ionization cones aligned with the radio jet, alongside evidence of shock quenching observed in the lower "anomalous arc". Conversely, jet-induced compression may stimulate star formation in other areas. We derived a galaxy-wide star formation rate of $\sim3 M_{\odot}\mathrm{yr}^{-1}$ decreasing to $0.3 M_{\odot}\mathrm{yr}^{-1}$ within the central $3.4 \mathrm{kpc}^2$. SITELLE's broad field coverage elucidates the galaxy's structural details, confirming that low-power jets significantly influence the host galaxy across parsec and kpc scales. The velocity dispersion map reveals asymmetric or double-peaked emission lines, tracing jet-disk interactions likely responsible for the formation of anomalous arm features. Small-scale ionizing clusters were detected in regions with disrupted gas flows, possibly formed through tidal interactions or shock compression. NGC~4258 thus presents a compelling case for studying LLAGN-driven feedback, illustrating how optical IFS combined with multi-wavelength data clarifies the impact of outflows and shocks on nearby spiral galaxies, providing insights into how these processes shape star formation and ISM conditions.

We extend our super-resolution and emulation framework for cosmological dark matter simulations to include hydrodynamics. We present a two-stage deep learning model to emulate high-resolution (HR-HydroSim) baryonic fields from low-resolution (LR-HydroSim) simulations at redshift $z = 3$. The method takes as inputs an LR-HydroSim and the high-resolution initial conditions (HR-HydroICs). First, the model stochastically generates high-resolution baryonic fields from the LR-HydroSim. Second, a deterministic emulator refines these fields using HR-HydroICs to reconstruct small-scale structures including displacement, velocity, internal energy, and gas/star classification. Trained on paired low- and high-resolution simulations produced with \texttt{MP-Gadget}, the model captures small-scale structures of the intergalactic medium and %Lyman-$\alpha$ forest observables down to the 100 kpc pressure smoothing scale relevant to the Lyman-$\alpha$ forest. The model achieves subpercent error for overdensity, temperature, velocity, and optical depth fields, a mean relative error of 1.07\% in the large-scale flux power spectrum (\(k < 3 \times 10^{-2}\ \mathrm{s/km}\)), and less than 10\% error in the flux probability distribution function. Notably, the two-stage model reduces the compute time by a factor of $\sim$450 compared to full smoothed particle hydrodynamics at the same resolution. This work demonstrates the potential of this framework as a powerful and efficient tool for generating high-resolution fields offering fast and accurate alternatives to traditional cosmological hydrodynamic simulations and enabling large-volume mock datasets for next-generation cosmological surveys.

Only a small fraction of Gamma-ray bursts (GRBs) have independent redshift measurements, which are essential for understanding their intrinsic properties. For this reason, empirical correlations of GRBs have often been touted as useful distance indicators, for both individual GRBs as well as population studies. Building upon our previous work, we test the ability of the Yonetoku, 3D Dainotti, and the L-T-E correlation to adequately constrain the GRB rate, $\Psi_{GRB}$. Our analysis demonstrates that, even under idealized conditions that neglect substantial uncertainties, the derived redshift solutions cannot accurately constrain $\Psi_{GRB}$, regardless of the intrinsic distribution's characteristic width. We thus demonstrate unequivocally that -- notwithstanding the questionable assumption of no selection biases -- empirical GRB correlations alone cannot serve as reliable distance indicators at either the individual or population level.

In this study, we use the luminous volume-limited samples obtained from the twelfth release of Sloan Digital Sky Survey data and mergers from Galaxy Zoo Project to investigate the influence of group richness in shaping galaxy properties' distributions and their relationships in the local Universe by comparison of mergers and non-mergers. The galaxies were restricted into mass-limited subsamples of low-mass, intermediate-mass and high-mass, assigned into groups from poor to rich group systems, where the distributions of star formation rate (SFR), specific SFR (SSFR), spectral index D$_n$ (4000) and $u-r$ colour properties between mergers and non-mergers for all subsamples and their relations with stellar mass of galaxies are compared. The study revealed a significant difference in the distributions between mergers' and non-mergers' properties for low-mass galaxies, while for high-mass galaxies the difference is very weak. For the low-mass sample, mergers possess higher SFR, SSFR than non-mergers when the group richness is kept constant, while for high-mass poor group galaxies have higher SFR, SSFR than rich group galaxies when merging status is kept constant. Mergers resemble young stellar populations and are bluer than non-mergers for low-mass, while for high-mass, mergers and non-mergers have comparable SFR, SSFR, D$_n$ (4000), and $u-r$ colour. The study concludes that group richness and stellar mass influence the mergers' and non-mergers' properties' distributions, and their relationships.

Star-forming galaxies on the main sequence (MS) are often regarded as a uniform population characterized by similar global star formation properties. However, there exists a diversity in galaxy morphologies at fixed stellar mass and SFR. In this study, using spatially-resolved properties from the MaNGA final data release, we classify MS galaxies into late-type (MS-late) and early-type (MS-early). In addition, we further divide the MS-early galaxies into two distinct subgroups based on their internal star formation and stellar mass distributions within the galaxies. The first group -- ``MS-early\_SF'' -- shows centrally concentrated star formation without prominent stellar bulges and resides preferentially in dense environments, suggesting environmentally-driven evolution. The second group -- ``MS-early\_stellar'' -- exhibits significant stellar bulges with suppressed central star formation, maintains disk-like star formation patterns, and inhabits environments similar to those of late-type galaxies, indicating evolution through internal secular processes. Our findings demonstrate that spatially-resolved observations play critical roles in revealing the diverse evolutionary pathways hidden within galaxies that share similar global properties.

Sub-Neptunes are small planets between the size of the Earth and Neptune. The orbital and bulk properties of transiting sub-Neptunes can provide clues for their formation and evolution of small planets. In this paper, we report on follow-up observations of a planetary system around the mid-M dwarf TOI-654, whose transiting sub-Neptune TOI-654 b ($P=1.53$ day) is validated as a suitable target for the atmospheric observation. We measure the planetary mass and stellar properties with the InfraRed Doppler instrument (IRD) mounted on the Subaru telescope and obtain the stellar and planetary properties from additional transit observations by the Transit Exoplanetary Survey Satellite (TESS) and a series of the Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets (MuSCAT). As a result, the planetary mass of TOI-654 b is determined to be $M_{\rm p} = 8.71 \pm 1.25 M_{\oplus}$, and the radius is updated to be $R_{\rm p} = 2.378 \pm 0.089 R_{\oplus}$. The bulk density suggests that the planet is composed of a rocky and volatile-rich core or a rocky core surrounded by a small amount of H/He this http URL-654 b is one of unique planets located around the radius valley and and also on the outer edge of the Neptune desert. The precise mass determination enables us to constrain the atmospheric properties with future spectroscopic observations especially for the emission by the James Webb Space Telescope and Ariel.

Using galaxy Ly$\alpha$ emission to probe reionization relies on establishing baseline expectations for its detectability in the absence of attenuation by neutral gas in the IGM. Towards this end, the growing numbers of $z \sim 5$--6 star-forming galaxies spectroscopically selected by JWST provide an ideal sample for determining how Ly$\alpha$ emission depends on galaxy properties and environment after reionization has largely completed. In this study, we use Keck LRIS to measure the Ly$\alpha$ emission of 46 JWST-selected [OIII]-emitting galaxies over $5.3 \lesssim z \lesssim 6.2$ in the foreground of the ultra-luminous quasar J0100+2802. Overall, we find that the fraction of galaxies detected in Ly$\alpha$ emission is consistent with previous works; however, the fraction also varies with environment. Most notably, we find an apparent deficit of Ly$\alpha$ in the largest group in our sample, at $z \simeq 6.19$, which falls within the redshift range of the quasar's highly ionized proximity zone. We speculate that the Ly$\alpha$ emission from this group may be partly scattered by a foreground neutral island. In contrast, we detect a high rate of Ly$\alpha$ emission in two groups at $z \simeq 5.73$ and $z \simeq 5.78$. These groups may be part of a structure that is extended along the line of sight, enhancing the transmission of Ly$\alpha$ emission. While our sample size is limited, our results suggest that environment may play a significant role in the detectability of galaxy Ly$\alpha$ emission even as late as $z \sim 6$.

We computed the thermal microwave emission from a 3D magnetohydrodynamic (MHD) simulation and compared it with observations of solar jets. The simulation treats the emergence of magnetic flux into the solar atmosphere and its interaction with a low, pre-existing ambient magnetic field. This interaction leads to the formation and development of a jet, driven by an eruption. The computed 17 GHz radio emission is compared with a number of observed jets, with respect to their morphology, their flux, and the rise time of the radio flux. We find that the MHD model reproduces the characteristics of lower-intensity jets reasonably well, whereas there are differences with stronger jets. We suggest possible ways to obtain more realistic jets from MHD simulations, so that they match better the real jets.

The timing of cosmic reionization across Local Group (LG) analogues provides insights into their early histories and surrounding large-scale structure. Using the radiation-hydrodynamic simulation THESAN-1 and its dark matter-only counterpart THESAN-DARK-1, we track the reionization histories of all haloes, including 224 LG analogues within the proximity of any of the 20 Virgo-like clusters with halo masses above 10^14 Msun at z=0 and their environments. The statistically controlled samples quantify how the reionization redshift (z_reion) correlates with halo mass, local overdensity, and present-day pair properties. Even at fixed mass, haloes in denser regions ionize earlier, and increasing the overdensity smoothing scale systematically suppresses small-scale structure, including local variations and environmental gradients in z_reion. Virgo-like clusters accelerate reionization in their surroundings out to ~5-10 cMpc, beyond which local overdensity again becomes the dominant factor. Within LG pairs, reionization timing offsets reach up to ~150 Myr and correlate with present-day halo separation, reflecting sensitivity to large-scale structure rather than mass ratio in driving asynchronous reionization. The results support an extreme inside-out picture where clustered sources rapidly ionize their immediate neighborhoods, while lower-density regions self-ionize later and voids wait for external homogenization. These links between environment and reionization timing explain the influence of protoclusters and help interpret fossil records in LG dwarfs around the Milky Way. For Milky Way analogues, we find a reionization redshift as early (late) as z_reion = 12.7^{+2.0}_{-1.7} (8.88^{+0.66}_{-0.70}) when considered on 125 ckpc (500 ckpc) scales, with LG analogues following an inside-out reionization picture.

The plasma-$\beta$ is an important fundamental physical quantity in solar plasma physics, which determines the dominating process in the solar atmosphere, i.e., magnetic or thermodynamic processes. Here, for the first time, we provide variations of magnetic field and plasma-$\beta$ along magnetically structured loops from the photosphere to the corona. We have selected several fan loops rooted in sunspot umbra observed simultaneously by the Interface Region Imaging Spectrograph and Solar Dynamics Observatory. The 3-min slow waves enabled us to trace and analyze several fan loops with cross-sectional areas in the lower atmosphere and locate their footpoints at the photosphere. We find the RMS magnetic field strengths in the range 1596-2269 G at the photospheric footpoints of the fan loops, which decrease rapidly to 158-236 G at the coronal footpoints. We estimated the plasma-$\beta$ at the photospheric and coronal footpoints in the range 0.2-0.5 and 0.0001-0.001, respectively. We found plasma-$\beta$$<$$1$ along the whole loop, whereas the plasma-$\beta$$\approx$$1$ layer is found to be at sub-photospheric heights. We compared our findings for isolated individual fan loops with a previously established model for active regions and found an almost similar pattern in variations with height, but with different plasma-$\beta$ values. Our results demonstrate the seismological potential of 3-min slow waves omnipresent in the umbral sunspot atmosphere to probe and map isolated loops and determine magnetic field and plasma-$\beta$ along these loops. The obtained parameters provide crucial ingredients for the theoretical modeling of the umbral atmosphere and wave dynamics along loops.

The Challan instrument is a solar full-disk imaging spectroscopic telescope planned to be installed at three sites with a 120-degree longitudinal difference, enabling continuous 24-hour observations of the Sun. It will take data every 2.5 min with a spatial resolution of $2-3^{\prime\prime}$ and a spectral resolving power (R) of >43,000 in H$\alpha$ and Ca II 854.2 nm bands simultaneously. Challan is composed of two modules, each dedicated to a specific waveband. This modular design is beneficial in minimizing the scattered light and simplifying the structure and engineering. The primary scientific goal of Challan is to investigate solar flares and filament eruptions. It is also expected to detect small-scale events in the solar chromosphere. In 2025, Challan will be installed at the Big Bear Solar Observatory for test observational runs, followed by scientific runs in 2026.

Star formation is a hierarchical process ranging from molecular clouds down to individual protostars. In particular how infalling asymmetric structures, called streamers, delivering new material onto protostellar systems, are connected to the surrounding envelope is not understood. We investigate the connection between the cloud material at 10000 au scales down to 300 au scales towards L1448N in the Perseus star-forming region hosting three young Class 0/I protostellar systems. Sensitive molecular line observations taken with the IRAM 30m telescope and NOEMA at 1.4 mm are used to study the kinematic properties in the region traced by the molecular lines. Several infalling streamers are associated with the protostellar systems, some of them traced by C18O and DCN, while one of them is bright in SO and SO2. The kinematic properties of the former streamers are consistent with the velocities observed at large envelope scales of 10000 au, while the latter case show different kinematics. The masses and infall rates of the streamers are 0.01 Msun and 0.01-0.1 Msun and 10^-6 Msun/yr and 5-18x10^-6 Msun/yr for IRS3A and IRS3C, respectively. The envelope mass in the L1448N region is ~16Msun, thus the mass of a single streamer is low compared to the envelope mass (<1%). However, compared to the estimated mass of the protostellar systems a single streamer could deliver up to 1% and 8-17% of mass towards IRS3A (M*~1.2 Msun) and IRS3C (M*~1 Msun), respectively. The rotational signatures of structures in L1448N are all connected - from the large-scale envelope, infalling streamers, down to the rotation of all three disks. Two of the three Class 0/I protostellar systems are still fed by this surrounding material, which can be associated to the remnant envelope. However, we also find a streamer that is bright in SO and SO2 towards IRS3C that could be connected to a nearby sulfur reservoir.

OGLE-2011-BLG-0462 is an isolated black hole of ~7 solar masses at a distance of 1.5 kpc identified thanks to the astrometric microlensing technique. It is the first specimen discovered of the large population of ~10^8 stellar-mass black holes that are believd to wander in the Galaxy. Electromagnetic radiation powered by accretion from the interstellar medium is expected from OGLE-2011-BLG-0462, but has not been detected at any wavelength. We present the results of a deep pointed observation with the Chandra satellite that provides an upper limit of 3x10^29 erg/s on the luminosity of OGLE-2011-BLG-0462 in the 0.5-7 keV energy range. This is about one order of magnitude below the previous limit obtained from shallower observations that serendipitously covered the sky position of this black hole. Our results are briefly compared with models of the source and with the X-ray upper limits for candidate isolated black holes and black holes in wide binary systems.

Fast radio bursts (FRBs) are millisecond radio pulses with extremely high bright temperature. Their physical origin is still a mystery. The discovery of FRB 20020428 supports the idea that at least a portion of FRBs is generated by magnetars. However, FRB 20200428 and other radio bursts of SGR 1935+2154 are much less energetic than that of extragalactic FRBs. Thus, whether the progenitors of extragalactic FRBs are magnetars is still in controversy. Here, we investigate the volumetric rates of radio bursts from SGR 1935+2154, non-repeating FRBs and FRB 20180916B using the uniform samples detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME). We find that they share a similar relation between the volumetric rate $R$ and the burst energy $E$, i.e., $R\propto E^{-\gamma}$ with $\gamma=1.31\pm 0.13$ from $10^{29}$ erg to $10^{42}$ erg. Our results support the hypothesis that both repeating and non-repeating FRBs originate from magnetars.

The Pierre Auger Observatory has published properties of the 100 highest-energy cosmic ray events (to energies above 100 EeV) which it recorded over a 17 year period. We have examined the directional properties of these events and have taken particular note of the most energetically extreme events. We find that the most energetic events have directions which are grouped in a non-random way at the 1\% level. There is an apparent clustering in a limited region of the sky. Close to that direction is found Centaurus A, which has long been considered as a source of such particles, but we also note that a close-by dwarf galaxy, the Large Magellanic Cloud (LMC) is closer in angular terms. We examine the possibility that the LMC might be a source of observed cosmic rays at the highest energies.

We review recent advances in multimessenger astrophysics, with particular emphasis on Centaurus A and on two pivotal events: the gravitational-wave detection GW 170817 and the ultra-high-energy neutrino KM3-230213A. Centaurus A is the prototype multimessenger source. The GW 170817 event, arising from a binary neutron star merger, marked a transformative moment in astronomy through the joint observation of gravitational waves and a broad spectrum of electromagnetic signals. The KM3-230213A neutrino, detected by the KM3NeT Collaboration, is the most energetic neutrino observed to date and poses significant challenges for current models, given its tension with null results from IceCube and the Pierre Auger Observatory. We assess astrophysical interpretations, including galactic, cosmogenic, and transient extragalactic sources, as well as implications for cosmic-ray acceleration. These cases underscore the scientific potential of high-energy multimessenger events in probing both the extreme universe and new physics.

The Single-Mirror Small Size Telescope (SST-1M) is a small Cherenkov telescope designed to detect gamma rays with energies more than about 1 TeV. The optical design of the SST-1M follows the Davies-Cotton concept to ensure good off-axis performance. In 2022, two SST-1M telescope prototypes were installed in Ondrejov, Czech Republic, and stereoscopic observations of astrophysical gamma-ray sources have been performed since then. VER J2019+368 is an unidentified very-high-energy (VHE) gamma-ray source, surrounded by several gamma-ray point-like and diffuse sources, together with their multi-wavelength counterparts. VHE emission was discovered by MILAGRO in 2012, followed by VERITAS observation, which revealed the complex morphology of the source. Recently, the LHAASO observatory detected photons with multi-TeV energies, opening up the possibility of particle acceleration up to PeV energies. In this contribution, we present preliminary results of the first observing campaign of the VER J2019+368 region, performed with SST-1M from April to November 2024. We present the data analysis, focusing on the morphological and spectroscopic study of the region. We also present the off-axis performance of SST-1M in the context of the prospects for detecting extended galactic gamma-ray sources. As one of the brightest and hardest sources in the LHAASO catalog, VER J2019+368 is an ideal candidate for testing the capabilities of the SST-1M, with its large field of view, to detect extended gamma-ray sources.

We report on NICER X-ray observations of the Be X-ray binary A 0538-66 located in the Large Magellanic Cloud. Fast pulsations (69 ms) in this source were discovered in 1980 during a bright outburst in which it reached a luminosity of ~8E38 erg/s, but were never reobserved since then. We clearly detected the pulsations at P=69.3055 +/- 0.0005 ms with a pulsed fraction of ~20% during a short time interval (~11 minutes) on 2023 January 9, when A 0538-66 had a luminosity of ~8E36 erg/s (0.3-10 keV). The pulsations were not detected in other NICER observations (total exposure ~162.7 ks), during which A 0538-66 had a similar or lower luminosity. On 2023 February 8-9 the source exhibited a strong variability, with short flares reaching ~1E38 erg/s, but no periodic pulsations were detected. Assuming the magnetospheric radius lies within the corotation radius during pulsations, we estimate the neutron star magnetic field is below ~2.7E10 G. This would make A 0538-66 the high-mass X-ray binary with the weakest known magnetic field. We discuss implications for magnetic field evolution in accreting pulsars and propose that, alternatively, A 0538-66 has a stronger magnetic field and during the NICER detection, a centrifugal barrier may have been active while part of the plasma accumulated at the magnetosphere sporadically leaked through it via an instability mechanism, allowing accretion onto the polar caps.

Solar flares and coronal mass ejections (CMEs) can accelerate electrons, causing bursts such as type IV emissions in the solar radio continuum. Although radio spectroscopy is a powerful diagnostic tool for the corona, the origin and mechanisms of type IV bursts remain uncertain. In situ measurements can occasionally shed some light on these mechanisms, but they are limited in space and time. Sophisticated numerical modelling offers the best approach to improve our understanding of the physical processes involved. This research examines type IV radio bursts, exploring the effects of various electron distribution properties and CMEs on their generation and characteristics. To transcend idealised assumptions, we employ realistic, anisotropic electron distributions - obtained from particle transport simulations within complex magnetohydrodynamic (MHD) environments - as input for radio emission models. We use the 3D MHD model COCONUT to generate coronal background configurations, including a CME modelled as a modified Titov-Démoulin magnetic flux rope (MFR). These MHD simulations are used by the PARADISE particle transport code, which injects energetic electrons into the MFR and tracks their evolution. Finally, we feed the electron distributions and solar wind parameters into the Ultimate Fast Gyrosynchrotron (GS) Codes to compute radio emission along lines of sight. Electrons injected close to the MFR's central axis remain largely confined, producing a GS emission spectrum resembling observed type IV characteristics. Varying observer positions, CME properties, and spectral indices of the electron energy distributions modify the intensities and durations of the observed bursts. The strongest GS emission is observed to originate from the CME flanks. Our results indicate that GS emission is the major component in type IV spectra, although additional contributors cannot be ruled out.

Differences in the ingress and egress shapes of transit light curves can indicate morning-evening temperature contrasts on transiting planets. Here, we pinpoint an alternative mechanism that can introduce asymmetries in transit light curves, potentially affecting the accurate determination of morning-evening differences. Small-scale magnetic field concentrations on the surfaces of the host star affect the visibility of stellar limb regions, making them brighter relative to the non-magnetic case. A difference in magnetization between the star's western and eastern limbs can thus create an asymmetry in limb brightness and, consequently, an asymmetry between transit ingress and egress. We model the limb darkening and stellar limb asymmetry in solar-like stars using the 3D radiative MHD code MURaM to simulate magnetized stellar atmospheres and the MPS-ATLAS code to synthesize spectra using ray-by-ray approach. Our results show that ingress-egress depth differences can reach up to 600 ppm for a 10000 ppm transit at 600 nm, depending on the magnetization of the stellar limbs--significantly interfering with planetary signals. Observations of the Sun show that such concentrations are often not accompanied by spots and do not manifest in photometric variability, indicating that even photometrically quiet stars can produce such asymmetries. However, planetary and stellar asymmetries exhibit distinct wavelength dependencies, which we propose to leverage for disentangling them.

Context: The mechanism behind the heating of the solar chromosphere remains unclear. Friction between neutrals and charges is expected to contribute to plasma heating in a partially ionised plasma (PIP). Aims: We aim to study the efficiency of the frictional heating mechanism in partially ionised plasmas by comparing a single-fluid model (1F) using ambipolar diffusion and a two-fluid model (2F) that incorporates elastic collision terms. Methods: We use the code MANCHA-2F to solve the equations for both models numerically. The simulations involve the vertical propagation of fast magneto-acoustic waves from the top of the photosphere through the chromosphere. The model atmosphere is vertically stratified, including a horizontal, homogeneous magnetic field. We also apply the linear theory to supplement the numerical results. Finally, we look at the assumptions of the 1F model to find out what causes the model discrepancies. Results: The results show that the temperature increase for the 1F model is slightly higher than for the 2F model, especially with long-period waves. The wave energy flux indicates that in the 2F model, the wave is transporting less energy upwards. From the linear theory, we find that the wave in the 2F model loses more energy than in the 1F model in the deep layers, but the opposite occurs in the high layers. Conclusions: The efficient dissipation in the 2F model in deep layers reduces the energy flux at the high layers, reducing heating and explaining the temperature differences between models. We attribute those discrepancies to the contribution of pressure forces to the drift velocity and the omission of a term related to the centre of mass frame reference in the 1F energy equation.}

Narrow-line Seyfert 1 galaxies (NLS1s) are generally known to be radio-quiet Active Galactic Nuclei (AGN), but a tiny subset of them are found to be extremely radio-loud with radio loudness parameter ($R_{\rm 1.4~GHz}$) $>$ 100. Given their rarity we investigated intra-night optical variability (INOV) and radio characteristics of a sample of 16 extremely radio-loud NLS1s. For all but four sample sources we report intra-night photometric monitoring for the first time with at least one monitoring session per source lasting for a minimum of 3.0 hours duration. In our sample, we detect INOV with a high duty cycle (up to 25 per cent) and large average amplitude ($\overline{\psi}$ $\sim$ 0.16) similar to that found in blazars. Using 3.0 GHz Very Large Array Sky Survey (VLASS) and auxiliary multi-frequency radio data we find that our RL-NLS1s are luminous ($L_{\rm 3.0~GHz}$ $\geq$ 10$^{24}$ W~Hz$^{-1}$), compact (less than a few kpc), variable, flat spectrum (${\alpha}_{\rm radio}$ $>$ -0.5) radio sources. The INOV, radio characteristics, and radio luminosity ($L_{\rm 1.4~GHz}$) versus super-massive black hole mass ($M_{\rm SMBH}$) plot infer that extremely radio-loud NLS1s are low-$z$ and low-luminosity analogs of flat spectrum radio quasars wherein the former are powered by, on average, one order-of-magnitude less massive SMBHs.

The Single-Mirror Small-Size Telescope (SST-1M) is an Imaging Atmospheric Cherenkov Telescope designed for detecting very high-energy gamma rays. With a compact design achieved through the adoption of silicon-photomultiplier pixels and a lightweight structure, SST-1M offers a large field of view of about 9° and features a mirror system of 4 m diameter with an optical PSF (at 80% of photon inclusion) of 0.08° on axis and 0.21° at 4° off-axis, and a fully digitizing readout almost deadtime free up to few kHz. The SST-1M achieved a high-performance and cost-effective solution for implementing an array of small-sized telescopes. The stereoscopic system of two SST-1Ms is temporarily installed at the Ondřejov Observatory in the Czech Republic. From an altitude of only about 510 m and in harsh meteorological conditions, the system is detecting galactic sources and flares of AGNs. The accurate calibration of the detector and the simulation benchmark are ongoing. The results of its performance are shown. A future final location is being considered and a future performance outlook is discussed.

Seyfert galaxies are emerging as a promising source class of high-energy neutrinos. The Seyfert galaxies NGC 4151 and NGC 1068 have come up respectively as the most promising counterparts of a 3$\sigma$ and of a 4.2$\sigma$ neutrino excesses detected by IceCube in the TeV energy range. Constraining the very-high-energy (VHE) emission associated with the neutrino signal is crucial to unveil the mechanism and site of neutrino production. In this work, we present the first results of the VHE observations ($\sim$29 hours) of NGC 4151 with the MAGIC telescopes. We detect no gamma-ray excess in the direction of NGC 4151, and we derive constraining upper limits on the VHE gamma-ray flux. The integral flux upper limit (at the 95% confidence level) above 200 GeV is $f = 2.3 \times 10^{-12}$ cm$^{-2}$ s$^{-1}$. The comparison of the MAGIC and IceCube measurements suggests the presence of a gamma-ray obscured accelerator, and it allows us to constrain the gamma-ray optical depth and the size of the neutrino production site.

Using data from Swift-BAT and Fermi-GBM, we report the first detection of a high-confidence quasi-periodic oscillation (QPO) in the thermal emission of gamma-ray burst GRB~240825A. The spectral analysis of the burst reveals two radiation components, including a thermal emission dominant in $100 \text{--} 300\,\mathrm{keV}$ and a non-thermal emission spanning a wide energy range. During the interval $2.07 \text{--} 3.25\,\mathrm{s}$ post-trigger, a strong QPO signal at $6.37\,\mathrm{Hz}$ ($\gtrsim 5\sigma$ confidence) is identified in the $100 \text{--} 300\,\mathrm{keV}$ thermal-dominated band. The variability analysis of the non-thermal component ($15 \text{--} 30\,\mathrm{keV}$) uncovered a $0.67\,\mathrm{Hz}$ QPO, consistent with light-curve modeling using periodic fast-rise exponential decay pulses. The strong QPO in the photospheric emission directly indicates a quasi-periodic oscillating jet. Together with the non-thermal emission variability, we show that this QPO can be explained in terms of a helical structure in the jet, where the viewing angle to the dominant emission region in the jet undergoes periodic changes.

Newborn pulsars resulting from core-collapse supernovae (CCSNe) are promising sources of high-energy (HE) cosmic rays and neutrinos. In this work, we focus on HE neutrinos generated by interactions between protons accelerated in relativistic pulsar winds and SN ejecta. Using a binned likelihood analysis, we evaluate the detection prospects of these neutrinos with IceCube and explore their potential for probing the initial spin period ($P$) and magnetic field strength ($B$) of newborn pulsars. Noticing a degeneracy in neutrino signal with $B/P^2$ across a broad parameter space, we find that HE neutrinos from a galactic newborn pulsar ($d=10$ kpc) with $(B/10^{12}~{\rm G})(P/{\rm ms})^{-2} \gtrsim 0.003$ can be detected at $\gtrsim 3\sigma$ significance. Even in the absence of a nearby pulsar, the diffuse flux from the cosmologic population of pulsars could be probed by next-generation detectors like IceCube-Gen2 and GRAND200k. For galactic pulsars with $(B/10^{12}~{\rm G})(P/{\rm ms})^{-2} \gtrsim 0.08$, the combination $B/P^2$ can be measured with an accuracy of better than 20\% at the $3\sigma$ confidence level. Additionally, we show that for pulsars with detectable HE neutrino signals, the emission can be clearly distinguished from neutrinos produced by interactions between SN ejecta and the circumstellar medium, due to their distinct temporal and spectral features.

Radioastronomical observations have recently discovered PAHs of moderate size (up to 24 carbon atoms) in cold dark clouds, although it is currently unknown whether they are formed in situ through a bottom-up mechanism or from larger PAHs (20-100 carbon atoms) inherited from a previous diffuse stage in a top-down scenario. Infrared observations have recently shown that large PAHs present in UV-illuminated regions are strongly enriched in deuterium. In order to shed light on the origin of PAHs in cold clouds, we have searched for deuterated benzonitrile in the cold dark cloud TMC-1. To that purpose we have synthesized the three isomers (ortho, meta, and para) of monodeuterated benzonitrile, measured their rotational spectra across the 2-18 GHz and 75-110 GHz frequency ranges in the laboratory, and searched for them in TMC-1 using data from the QUIJOTE line survey. We did not detect any of the three species and have derived a 3sigma upper limit on the column density of each of them of 3.0e10 cm-2, meaning a fractional abundance relative to H2 of <3e-12. We derived a D/H ratio (which we define as the total number of D atoms with respect to the total number of H atoms present in benzonitrile) of <1.2 %. This value is in line with the range of D/H ratios observed for other molecules in TMC-1 (0.06-3.3 %), where deuterium enrichment is explained in terms of isotopic fractionation at low temperature. It is however below the range of D/H ratios derived for large unspecific PAHs from JWST observations of the galactic PDRs Orion Bar and M17 and the galaxies M51 and NGC3256-S (between 1% and <17%). Although it is not straightforward to compare the deuteration of PAHs in dark and UV-irradiated clouds, our results suggest that the population of PAHs detected in cold dark clouds does not result from the fragmentation of larger PAHs inherited from the previous diffuse stage in a top-down scenario.

Neutrinos and dark energy (DE) have entered a new era of investigation, as the latest DESI baryon acoustic oscillation measurements tighten the constraints on the neutrino mass and suggest that DE may be dynamical rather than a cosmological constant. In this work, we investigate the cosmological implications of simultaneously incorporating $\sum m_\nu$ and $N_{\rm eff}$ within the framework of dynamical DE. A joint analysis of DESI DR2, cosmic microwave background, DESY5 supernova, and DESY1 weak lensing data yields a total neutrino mass of $\sum m_\nu = 0.098^{+0.016}_{-0.037}\,\mathrm{eV}$, indicating a preference for a positive neutrino mass at the $2.7\sigma$ level within the $w_0w_a$CDM framework. This work highlights the important influence of the strength of evidence for dynamically evolving DE on the measurement of neutrino mass, with stronger evidence for DE dynamics leading to a larger neutrino mass. These results underscore the importance of measuring the neutrino mass within the framework of dynamical DE, particularly in light of the forthcoming, more complete DESI data releases.

Measurements of galaxy distributions at large cosmic distances capture clustering from the past. In this study, we use a cosmological model to translate these observations into the present-day galaxy distribution. Specifically, we reconstruct the 3D matter power spectrum at redshift $ z = 0 $ using Dark Energy Spectroscopic Instrument (DESI) Year 1 (DR1) galaxy clustering data and Cosmic Microwave Background (CMB) observations, assuming the $ \Lambda \text{CDM} $ model, and compare it to the result assuming the $ w_0w_a \text{CDM} $ model. Building on previous state-of-the-art methods, we apply Effective Field Theory (EFT) modelling of the galaxy power spectrum to account for small-scale effects in the 2-point statistics of galaxy data. The EFT approach offers a more robust methodology than traditional methods for modelling the galaxy power spectrum from galaxy clustering data, which can be used to test the consistency of the assumed cosmological model. By incorporating both CMB and galaxy clustering data across a range of redshifts, we can identify discrepancies between the datasets, which would indicate potential inaccuracies in the assumed expansion history. While previous studies have shown consistency with $ \Lambda \text{CDM} $, this work extends the analysis with higher-quality data to further test the expansion histories of both $ \Lambda \text{CDM} $ and $ w_0w_a \text{CDM} $. Our findings show that both $ \Lambda \text{CDM} $ and $ w_0w_a \text{CDM} $ provide consistent fits to the matter power spectrum recovered from DESI DR1 data.

Luminosity function and event rate of Gamma-Ray Bursts (GRBs) are easily biased by the instrument and selection effects. We select 115 Fermi/GBM GRBs with good spectra fitted by a smoothly broken power-law function. The $\tau$-statistic method is used to describe how the luminosity evolves with redshift. The non-parametric Lynden-Bell's c$^{-}$ method has been applied to get the cumulative luminosity function and event rate which is compared with the star formation history. How the selection and instrument effects bias the deduced event rate has been carefully studied. We find that the event rate always exceeds the star formation rate (SFR) at lower redshift and matches with each other at higher redshift, which is independent of energy bands and consistent with previous findings of other satellites. Furthermore, it is found that sample completeness does not affect the deduced event rate too much as mentioned for the Swift lGRBs in Dong et al.. A triple power-law function has been used to fit the cumulative flux distribution and categorize the total sample into three subsamples of bright, medium and faint GRBs. We find that the event rates of bright GRBs, unlike medium and faint ones, comply with the SFR ideally, which indicates that these bright GRBs with higher luminosity are possibly produced from the core-collapse of massive stars.

In this work we quantify the ability of the upcoming SPHEREx survey to constrain cosmological observables and test the internal consistency of the cosmological constant and cold dark matter ($\Lambda$CDM) model. Using Fisher matrix forecasting, we assess the expected precision on Baryon Acoustic Oscillations (BAO) observables, such as the angular diameter distance $D_\mathrm{A}(z)$ and the Hubble parameter $H(z)$. We further explore SPHEREx's potential to probe some of the fundamental assumptions of large-scale spatial homogeneity and isotropy, through model-independent reconstructions of several consistency tests of the $\Lambda$CDM model. In addition, we also examine the effect of the model dependence of the resulting Fisher and covariance matrices, using a neural network (NN) classification approach. We find that, while it is commonly assumed the covariance matrix depends weakly on the model, in fact the NN can very accurately ($\sim 98\%$) detect the underlying fiducial cosmological model based solely on the covariance matrix of the data, thus challenging this assumption.

I develop an efficient numerical method to obtain the gravitational potential of razor-thin spiral perturbations and use it to assess the standard tight-winding (or WKB) approximation, which is found reasonably accurate for pitch angles $\alpha\lesssim 20°$. I extend Kalnajs' (1971)' potential-density pairs to logarithmic spirals with arbitrary power-law amplitude. Approximating a spiral locally by one of these models provides a second-order tight-winding approximation that predicts the phase offset between spiral potential and density, the resulting radially increasing pitch of the potential, and the non-local outward angular-momentum transport by gravitational torques. Beyond the inner and outer edge of a spiral with m arms, its potential is not winding ($\alpha=90°$), decays like $R^m$ and $R^{-1-m}$, respectively, and cannot be predicted by a local approximation.

The SST-1M telescopes are a pair of Imaging Atmospheric Cherenkov Telescopes (IACTs) that have been operating at the Ondřejov Observatory (510 m a.s.l.) in the Czech Republic since 2022. Optimized for detecting gamma rays in the energy range 1-300 TeV, they are capable of performing both mono and stereo observations. Despite challenging atmospheric conditions, SST-1M has successfully detected several galactic and extragalactic gamma-ray sources with energies reaching up to 200 TeV during its ongoing commissioning. In this study, we analyze the performance of the SST-1M telescopes at different locations to assess the impact of altitude and relative telescope spacing on their physics performance. The low-altitude site at 510 m a.s.l. has already been investigated using both Monte Carlo simulations and real data. For comparison, we selected an intermediate-altitude site at 1420 m a.s.l. corresponding to Pampa Amarilla in Argentina and a high-altitude site at 4270 m a.s.l. corresponding to Hanle in India - both of which offer favorable astronomical conditions.

High-resolution spectroscopy (HRS) of exoplanet atmospheres has successfully detected many chemical species and is quickly moving toward detailed characterization of the chemical abundances and dynamics. HRS is highly sensitive to the line shape and position, thus, it can detect three-dimensional (3D) effects such as winds, rotation, and spatial variation of atmospheric conditions. At the same time, retrieval frameworks are increasingly deployed to constrain chemical abundances, pressure-temperature (P-T) structures, orbital parameters, and rotational broadening. To explore the multidimensional parameter space, they need computationally fast models that are consequently mostly one-dimensional (1D). However, this approach risks introducing interpretation bias since the planet's true nature is 3D. We investigate the robustness of this methodology at high spectral resolution by running 1D retrievals on simulated observations in emission within an observational framework using 3D Global Circulation Models of the quintessential HJ WASP-76 b. We find that the retrieval broadly recovers conditions present in the atmosphere, but that the retrieved P-T and chemical profiles are not a homogeneous average of all spatial and phase-dependent information. Instead, they are most sensitive to spatial regions with large thermal gradients, which do not necessarily coincide with the strongest emitting regions. Our results further suggest that the choice of parameterization for the P-T and chemical profiles, as well as Doppler offsets among opacity sources, impact retrieval results. These factors should be carefully considered in future retrieval analyses.

Observations in the Galaxy and nearby spirals have established that the HI-to-H$_2$ transition at solar metallicity occurs at gas weight of $P_{\rm DE}/k_B\approx 10^4 \ \rm K \ cm ^{-3}$, similar to solar neighbourhood conditions. Even so, state-of-the-art models of a self-regulated interstellar medium underproduce the molecular fraction ($R_{\rm mol}\equiv M_{\rm H_2}/M_{\rm HI}$) at solar neighbourhood conditions by a factor of $\approx2-4$. We use the GHOSDT suite of simulations at a mass resolution range of $100-0.25\ M_{\odot}$ (effective spatial resolution range of $\sim 20-0.05\ \rm pc$) run for 500 Myr to show how this problem is affected by modeling choices such as the inclusion of photoionizing radiation, assumed supernova energy, numerical resolution, inclusion of magnetic fields, and including a model for sub-grid clumping. We find that $R_{\rm mol}$ is not converged even at a resolution of 1 $M_{\odot}$, with $R_{\rm mol}$ increasing by a factor of 2 when resolution is improved from 10 to $1\ M_{\odot}$. Models excluding either photoionization or magnetic fields result in a factor 2 reduction in $R_{\rm mol}$. The only model that agrees with the observed value of $R_{\rm mol}$ includes our sub-grid clumping model, which enhances $R_{\rm mol}$ by a factor of $\sim3$ compared with our fiducial model. This increases the time-averaged $R_{\rm mol}$ to $0.25$, in agreement with the Solar circle value, and closer to the observed median value of $0.42$ in regions comparable to the solar neighbourhood in nearby spirals. Our findings show that small-scale clumping in the ISM plays a significant role in H$_2$ formation even in high-resolution numerical simulations.

We present an empirical yet physically motivated simulation of realistic Lyman-$\alpha$ emitters (LAEs) at $z\sim2-3$, crucial for ongoing and forthcoming cosmological LAE surveys. We combine an empirical $\mathtt{UniverseMachine}$ galaxy-halo model with a simple spherical expanding shell model for the Lyman-$\alpha$ radiative transfer, calibrating only three free parameters to simultaneously reproduce the observed Lyman-$\alpha$ luminosity function and the angular clustering. Our LAE model is further supported by its consistency with other observables such as the Lyman-$\alpha$ equivalent width distribution, the Lyman-$\alpha$ escape fraction as a function of stellar mass and dust reddening, and the systemic velocity offsets. Our LAE model provides predictions for the halo occupation distributions for LAEs and relationship between Ly$\alpha$ luminosity and halo mass, including the distribution of satellite LAEs. Our work provides a crucial first step towards creating a high-fidelity LAE synthetic catalog for the LAE cosmology surveys. We make our LAE catalog and spectra publicly available upon publication.

The rotation of the linear polarisation plane of photons during propagation, also known as cosmic birefringence, is a powerful probe of parity-violating extensions of standard electromagnetism. Using Planck legacy data, we confirm previous estimates of the isotropic birefringence angle, finding $\beta \simeq 0.30 \pm 0.05$ [deg] at 68% CL, not including the systematic error from the instrumental polarisation angle. If this is a genuine signal, it could be explained by theories of Chern--Simons-type coupled to electromagnetism, which could lead to a harmonic scale-dependent birefringence signal, if the hypothesis of an ultra-light (pseudo) scalar field does not hold. To investigate these models, we pursue two complementary approaches: first, we fit the birefringence angle estimated at different multipoles, $\beta_{\ell}$, with a power-law model and second, we perform a non-parametric Bayesian reconstruction of it. Both methods yield results consistent with a non-vanishing constant birefringence angle. The first method shows no significant dependence on the harmonic scale (up to $1.8\sigma$ CL), while the second method demonstrates that a constant model is favored by Bayesian evidence. This conclusion is robust across all four published Planck CMB solutions. Finally, we forecast that upcoming CMB observations by Simons Observatory, LiteBIRD and a wishful CMB-Stage 4 experiment could reduce current uncertainties by a factor of approximately 7.

The hybrid detection approach in astroparticle physics has been successfully employed in cosmic-ray experiments and is currently being explored by gamma-ray observatories like LHAASO. We present a study on the hybrid detection concept for the future Southern Wide-field Gamma-ray Observatory (SWGO), integrating multiple Cherenkov telescopes represented in the analysis by Single-Mirror Small-Size imaging atmospheric Cherenkov Telescopes (SST-1M) located next to the surface array of water Cherenkov detectors (WCDs). We discuss the mutual benefits of this hybrid approach and present simulation-based results on key performances. Our findings points to the fact that the combination of wide field-of-view and continuous operation of WCDs with the high angular and energy resolution of Cherenkov telescopes could significantly improve the overall detection capabilities of the SWGO experiment.

We consider models where the dilaton, seen as the pseudo-Goldstone boson of broken scale invariance, plays the role of dark energy. We revisit Weinberg's theorem and show that quantum corrections induced by the graviton lead to the screening of the dilaton locally. We also discuss the time evolution of the equation of state and find that phantom crossing is a natural feature of these models. The time variation of the equation of state and its deviation from $-1$ is limited by screening locally and can only be relaxed when the dilaton is allowed to have a mass of the order of the Hubble rate cosmologically, thus going beyond single-field screened dark-energy models. This obstruction extends to all single-field screened models of the chameleon-type where the large mass of the scalar on cosmological scales leads to a negligible variation of the equation of state at low redshift.

In this work, we apply a soft-sphere discrete element method (SSDEM) within the PKDGRAV N-body integrator to investigate the formation of planetesimal systems through the gravitational collapse of clouds of super-particles. Previously published numerical models have demonstrated that the gravitational collapse of pebble clouds is an efficient pathway to produce binary planetesimal systems. However, such investigations were limited by their use of a perfect-merger and inflated-radii super-particle approach, which inhibits any analysis of planetesimal shapes and spin states, precludes the formation of the tightest binary orbits, and produces significantly under-dense planetesimals. The SSDEM enables super-particles to rest upon each other through mutual surface penetration and by simulating contact physics. Super-particles do not need to be inflated and collisions are not treated as perfect mergers; we can thus track the evolution of planetesimal shapes, spins, and tight binary orbits. We demonstrate that the SSDEM is an excellent method to model the collapse process, and is capable of producing many binary planetesimal systems from a single cloud. Our results confirm the findings of previously published perfect-merging models while also producing novel results about planetesimal spin and shape properties. Newly-formed planetesimals exhibit 10-hr rotation periods on average and can be characterized by a wide variety of shapes (spherical, oblate, top-shaped, flattened, egg-shaped, or prolate), with the most-massive planetesimals primarily forming as spheres and oblate-spheroids.

Grid type pre-initial conditions are commonly used to initialize particle positions in cosmological simulations. While these conditions are known to produce noticeable numerical artifacts in void regions, their impact on halo properties has generally been assumed to be negligible. In this work, we employ multiple simulations to demonstrate that grid initialization induces statistically significant artifacts in halo shapes, despite the modest absolute amplitude ($\sim 1\%$) making them unimportant for most cosmological studies. We identify a redshift-dependent artificial alignment pattern: at low redshifts ($z<2$), halo shapes preferentially orient away from the simulation box's Cartesian axes, whereas their constituent particles initially exhibit alignment with these axes. We propose a mathematical hypothesis to explain this flipping behavior.

I suggest the double-degenerate (DD) scenario with a merger-to-explosion delay (MED) time (the DD-MED scenario) of about 1-2 years to explain the rare properties of the recently analyzed type Ia supernova (SN Ia) SN 2020aeuh. The rare properties are the SN Ia ejecta interacting with a carbon-oxygen (CO)-rich circumstellar material (CSM) at approximately 50 days post-explosion. In this DD-MED scenario, two massive CO white dwarfs (WDs), masses of M1=1.1Mo and M2=1, merge to leave a rapidly rotating lonely WD of about the Chandrasekhar mass. The merger process ejects 0.7Mo to form a nonspherical CO-rich CSM. At the explosion, there is a lonely WD and a detached hydrogen- and helium-deficient CSM. Studies proposed the other lonely WD scenario, the core-degenerate (CD) scenario, to explain several specific SNe Ia and SN Ia remnants. SN 2020aeuh is the first particular SN Ia that is attributed to the DD-MED scenario. Besides being slightly brighter than typical SNe Ia and the CSM interaction, SN 2020aeuh is a normal SN Ia. Therefore, this study strengthens the claim that the lonely WD scenarios, i.e., the DD-MED and CD scenarios, account for most, if not all, normal SNe Ia; all SN Ia scenarios, whether lonely WD or not, might contribute to peculiar SNe Ia.

Low-resolution infrared spectroscopy from JWST confirms the presence of SiC and likely metallic iron dust around asymptotic giant branch (AGB) stars in the Sextans A dwarf galaxy, which has a metallicity ~1%-7% Z_sun. While metal-poor carbon-rich AGB stars are known to produce copious amounts of amorphous carbon dust owing to the dredge up of newly synthesized carbon, this is the first time that Si- and Fe-bearing dust has been detected at this extreme metallicity. Of the six AGB stars observed, one is an intermediate-mass (~1.2-4 M_sun) carbon star showing SiC dust, and another is an oxygen-rich M-type star with mass ~4-5 M_sun that is likely undergoing hot bottom burning. The infrared excess of the M-type star is strong, but featureless. We tested multiple dust species, and find that it is best fit with metallic iron dust. Assuming its dust-production rate stays constant over the final 2-3x10^4 yr of its evolution, this star will produce ~0.9-3.7 times the iron dust mass predicted by models, with the range depending on the adopted stellar mass. The implications for dust production in high-redshift galaxies are potentially significant, especially regarding the assumed dust species used in dust evolution models and the timescale of AGB dust formation. Stars on the upper end of the AGB mass range can begin producing dust as early as 30-50 Myr after they form, and they may therefore rival dust production by supernovae at high redshift.

We present centimeter continuum observations of seven high luminosity massive protostars and their surroundings as part of the SOFIA Massive (SOMA) Star Formation Survey. With data from the Very Large Array and the Australia Telescope Compact Array, we analyze the spectral index, morphology and multiplicity of the detected radio sources. The high sensitivity and high resolution observations allow us to resolve many sources. We report thirteen new detections and two previously known detections that we observed for the first time in radio frequencies. We use the observations to build radio spectral energy distributions (SEDs) to calculate spectral indices. With radio morphologies and the spectral indices, we give assessments on the nature of the sources, highlighting five sources that display a radio jet-like morphology and a spectral index consistent with ionized jets. Combining with the SOMA Radio I sample, we present the radio - bolometric luminosity relation, especially probing the regime from $L_{\rm bol}\sim 10^4$ to $10^6\:L_\odot$. Here we find a steep rise in radio luminosity, which is expected by models that transition from shock ionization to photoionization.

White dwarf planetary systems uniquely link the bulk elemental composition of exoplanetary material to the mineralogy as photospheric abundances can be compared to circumstellar dust mineralogy. This study re-examines Spitzer/IRS spectra of eight white dwarfs with both circumstellar dust and photospheric metals. All systems show 10$\mu$m silicate emission features consistent with a mixture of olivine and pyroxene silicates, with varying dominance. New Hubble Space Telescope ultraviolet spectroscopic observations of two of these systems, GD56 and WD1150-153, reveal that both are accreting dry, rocky material. WD1150-153 is accreting material consistent with Bulk Earth, while GD56 is accreting core-rich material with an inferred core mass fraction of 0.59$^{+0.08}_{-0.09}$ (0.37$^{+0.08}_{-0.08}$ by mole). A comparison between the bulk elemental composition of the accreted planetary material and the dust mineralogy of the eight systems reveals a tentative correlation between the dominant silicate mineralogy and the Mg/Si ratio, indicating that the circumstellar and photospheric material are compositionally similar. This suggests that rapid and well-mixed accretion is occurring with minimal compositional alteration. Furthermore, new GGCHEM equilibrium chemistry models confirm that Mg-rich planetary material preferentially forms olivine-rich dust, highlighting the importance of equilibrium in planetary chemistry and that a host star or rock's Mg/Si can be used to predict whether its silicate mineralogy is olivine- or pyroxene-dominated, influencing its capacity to structurally store water, recycle key nutrients, and possibly habitability.

A mechanism for generating anisotropic enhancements of the curvature perturbation through a vector field is proposed. We find that when the mixing between the inflaton perturbation and the vector-field perturbation is sufficiently strong in the anisotropic inflation, the power spectrum becomes dominated by anisotropic constant modes. This suggests that statistical anisotropy in primordial black hole (PBH) formation may be inevitable if inflation undergoes an anisotropic inflationary phase. Our findings offer a novel approach to probe vector fields during inflation and to test the cosmic no-hair conjecture.

Low redshift fast radio bursts (FRBs) provide robust measurements of the host-galaxy contribution to the dispersion measure (DM), which can constrain the circumgalactic medium (CGM) of the hosts. We curate a sample of 20 nearby FRBs with low scattering timescales and face-on host galaxies with stellar masses ranging from $10^9 < M^* / M_\odot < 10^{11}$. We fit the distribution of the host galaxy DM to a quadratic model as a function of stellar mass with a mass-independent scatter and find that the more massive the host, the lower its host DM. We report that this relation has a negative slope of $m = -97 \pm 44$ pc/cm$^{-3}$ per dex in stellar mass. We compare this measurement to similar fits to three sub-grid models implemented in the CAMELS suite of simulations from Astrid, IllustrisTNG, and SIMBA and find that fine-tuning of the host ISM contribution as a function of stellar mass is required in order to reconcile the observational data with the predictions of the fiducial CAMELS-Astrid model. More generally, models which attribute a positive correlation between stellar mass and host dispersion measure ($m > 0$) to the CGM are in tension with our measurement. We show that this conclusion is robust to a wide range of assumptions, such as the offset distribution of FRBs from their hosts and the statistics of the cosmic contribution to the DM budget along each sightline. Our results indirectly imply a lower limit on the strength of baryonic feedback in the Local Universe $(z < 0.2)$ in isolated $\sim L^*$ halos, complementing results from weak lensing surveys and kSZ observations which target higher halo mass and redshift ranges.

Time-domain astrophysics relies on heterogeneous and multi-modal data. Specialized models are often constructed to extract information from a single modality, but this approach ignores the wealth of cross-modality information that may be relevant for the tasks to which the model is applied. In this work, we propose a multi-modal, mixture-of-expert variational autoencoder to learn a joint embedding for supernova light curves and spectra. Our method, which is inspired by the Perceiver architecture, natively accommodates variable-length inputs and the irregular temporal sampling inherent to supernova light curves. We train our model on radiative transfer simulations and validate its performance on cross-modality reconstruction of supernova spectra and physical parameters from the simulation. Our model achieves superior performance in cross-modality generation to nearest-neighbor searches in a contrastively-trained latent space, showing its promise for constructing informative latent representations of multi-modal astronomical datasets.

We initiate the analysis of the inflationary dynamics in Weyl-invariant Einstein-Cartan gravity nonminimally coupled to the Standard Model of particle physics. We take the axion-like particle of gravitational origin to be heavy and show that inflation with the Higgs field can be accommodated in this framework.

We extend the Standard Model (SM) by introducing a $U(1)'$ gauge boson and a real pseudo-scalar field, both odd under a $\mathbb{Z}_2$ symmetry. The resulting low-energy spectrum consists of a stable vector as the dark matter candidate, and a pseudo-scalar mediator, which interacts with the SM via a Higgs portal coupling and a dimension-five portal connecting it to both the dark and visible photons. We explore the freeze-in of both particles at low reheating temperature, finding a rich yield evolution dynamics in the early Universe. This setup brings a consistent dark matter scenario in which the dark photon relic abundance is generated through freeze-in at low reheating temperatures. In addition to its cosmological viability, the model can be tested at the LHC: Higgs bosons can decay into dark photons and displaced visible photons via the long-lived mediator. These signatures allow us to constrain the Higgs portal coupling using recent searches for non-pointing photons and limits on invisible or undetected Higgs decays. We derive meaningful constraints on the dark matter parameter space, in particular excluding a thermalized mediator in the region compatible with the observed relic abundance.

We show that minimal, fermionic dark matter (DM) models in the $n$-dimensional representation of the weak force with zero hypercharge that make up 100% of the DM under the standard cosmological history are strongly excluded for $n < 9$. This includes the thermal wino, which we show is ruled out even allowing for DM core sizes up to $\sim$6.7 kpc with the preferred local DM density or $\sim$3.7 kpc in addition to the local DM density being half the preferred value, at less than $0.2$ GeV/cm$^3$. We reach these conclusions through dedicated searches with 14 years of Fermi gamma-ray data in the inner Galaxy between 30 GeV and 2 TeV for the continuum gamma-rays produced in the decays of unstable particles produced in DM annihilation and bound-state formation processes. We consider a variety of Milky Way DM profiles in our analyses, including those motivated by modern hydrodynamic cosmological simulations, and show that all the $n < 9$ minimal DM models are disfavored even under the most conservative assumptions for these density profiles. While wino, quintuplet ($n=5$), and $n = 7$ DM models are strongly disfavored by our analyses under the standard cosmology, we discuss how non-standard cosmological histories or DM sub-fractions could still allow for these particles to be realized in nature, with discovery opportunities at next-generation particle colliders and gamma-ray telescopes.

We forecast the reach of the upcoming Cherenkov Telescope Array Observatory (CTAO) to the full set of real representations within the paradigm of minimal dark matter. We employ effective field theory techniques to compute the annihilation cross section and photon spectrum that results when fermionic dark matter is the neutral component of an arbitrary odd and real representation of SU(2), including the Sommerfeld enhancement, next-to-leading log resummation of the relevant electroweak effects, and the contribution from bound states. We also compute the corresponding signals for scalar dark matter, with the exception of the bound state contribution. Results are presented for all real representations from the $\sim$3 TeV triplet (or wino), a $\mathbf{3}$ of SU(2), to the $\sim$300 TeV tredecuplet, a $\mathbf{13}$ of SU(2) that is at the threshold of the unitarity bound. Using these results, we forecast that with 500 hrs of Galactic Center observations and assuming background systematics are controlled at the level of ${\cal O}(1\%)$, then should no signal emerge, CTAO could exclude all representations up to the $\mathbf{11}$ of SU(2) in even the most conservative models for the dark-matter density in the inner galaxy, in both the fermionic and scalar dark matter cases. Assuming the default CTAO configuration, the tredecuplet will marginally escape exclusion, although we outline steps that CTAO could take to test even this scenario. In summary, CTAO appears poised to make a definitive statement on whether real WIMPs constitute the dark matter of our universe.

The astrophysical origin of observed low-mass compact binary coalescences in the 1-2.5 $M_{\odot}$ range remains ambiguous. Both binary neutron star (BNS) and binary low-mass black hole (LMBH) mergers produce nearly identical inspiral waveforms, and electromagnetic follow-up is not always possible. Distinguishing between these scenarios therefore presents a key challenge. We demonstrate that waveform differences in the late-inspiral to postmerger epochs create significant mismatches that will be detectable by planned detectors, viz., NEMO, Cosmic Explorer, and Einstein Telescope, while the currently operational LIGO A+ will be effective only for nearby sources. These differences are enhanced for stiffer equations of state. We show how the redshift-dependent compact binary merger rate inferred from gravitational wave observations can be parsed into BNS and LMBH components, accounting for misclassification probability. We forecast model-independent 90% exclusion sensitivities for the LMBH fraction. Interpreting these LMBHs as dark matter capture-induced transmuted black holes, we convert exclusion sensitivities into projected exclusion bounds on heavy non-annihilating dark matter. Our results illustrate how gravitational wave measurements can disentangle compact object populations and provide new insights into particle dark matter interactions.

The DAMIC-M collaboration recently reported impressive bounds on sub-GeV dark matter, robustly testing both thermal and non-thermal models for the very first time. In this work we derive novel bounds from the recent PandaX-4T ionization S2-only search for Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS). We find that the PandaX-4T S2-only data is able to compete with the DAMIC-M results, providing the best constraints for scalar and asymmetric thermal dark matter models for masses between 20 to 200 MeV. We further discuss the implications of recent direct detection results for several other sub-GeV dark matter models, highlighting their complementarity with astrophysical, cosmological and laboratory probes.

When the solar wind encounters the Moon, a plasma void forms downstream of it, known as the lunar wake. In regions where the magnetic field is quasi-parallel to the plasma-vacuum boundary normal, plasma refills the wake primarily along magnetic field lines. As faster electrons outpace slower ions, an ambipolar electric field is generated, accelerating ions and decelerating electrons. Recent particle-in-cell simulations have shown that when accelerated supersonic ion beams from opposite sides of the wake meet near the wake center, electrostatic shocks may form, decelerating ions and heating electrons into flat-top velocity distributions. Using data from the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) spacecraft, we present the first observational evidence of the predicted electrostatic shocks. Near the wake center of one event, we observed an electrostatic solitary structure with an amplitude of ~2 mV/m and a spatial scale of ~50 local Debye lengths. This structure generated a potential increase of ~50 V from upstream to downstream, heating incoming electrons by ~50 eV in the parallel direction while decelerating ions by ~60 km/s leading to a density enhancement. At a second event representing a more evolved stage, we observed more dissipated structures dominated by strong electrostatic waves, with persistent potential increases driving continued field-aligned electron heating and ion deceleration. These observations confirm simulation predictions of electrostatic shock formation and the associated particle dynamics within the lunar wake, with potential applications to understanding plasma interactions around other airless celestial bodies.

Primordial black holes (PBHs), hypothesized to form in the early universe from gravitational collapse of density fluctuations, represent a well-motivated dark matter (DM) candidate. Their potential detection through gamma-ray signatures arising from Hawking radiation would provide definitive evidence for their existence and constrain their contribution to the DM abundance. Unlike conventional DM candidates, PBHs emit a unique, thermal-like spectrum of particles as they evaporate, including photons, neutrinos, and possible beyond-the-Standard Model particles. Future high-sensitivity gamma-ray observatories, such as e-ASTROGAM and other next-generation telescopes, will play a pivotal role in this search. With improved energy resolution and sensitivity, these missions can disentangle PBH-originating photons from astrophysical backgrounds, probe subtle spectral features such as multi-peak structures, and test exotic evaporation models. Such observations could either confirm PBHs as a viable DM component or place stringent limits on their abundance across critical mass windows. In this work, we explore the distinguishing features of a double-peaked gamma-ray spectrum produced by PBHs, focusing on the asteroid-mass window ($10^{15}$ g to $10^{17}$ g), where Hawking radiation peaks in the MeV to GeV range. Using a likelihood-based analysis, we demonstrate how future missions could discriminate between single- and double-peaked PBH scenarios, the latter arising in cosmological models predicting multi-modal PBH mass distributions. Our results highlight the diagnostic power of spectral shape analysis in identifying PBH populations and constrain the parameter space for which a double-peaked signal could be detectable above background.

Inspired by the recent measurement of the scalar spectral index, $n_s = 0.9743 \pm 0.0034$, by the Atacama Cosmology Telescope (ACT) DR6 data, we present an update on the split supersymmetry hybrid inflation model, also known as $\mu$-term hybrid inflation. The model employs a canonical Kähler potential but incorporates an additional renormalizable term in the superpotential $W$, which yields the MSSM $\mu$-term following supersymmetry breaking. This additional term in $W$ is responsible for a high reheat temperature, $T_r \gtrsim 10^{12}$ GeV, and consequently the necessity of split supersymmetry in this class of models. The predicted scalar spectral index is in excellent agreement with the ACT measurement and $r$, the tensor to scalar ratio, is estimated to be less than or of order $10^{-2} -10^{-3}$. For the running of the scalar spectral index we find $|dn_s/d \ln k| = O(10^{-4})$. With $T_r \gtrsim 10^{12}$ GeV, leptogenesis is readily implemented in this class of models. A wino-like LSP with mass of around 2 TeV is a plausible dark matter candidate.

The impact of the human activities can be evaluated by the Planetary Boundaries (PBs), however, so far it is not clear how to assess the influence of specific sociopolitical events (SPEs) on the Earth System (ES) and at the same measure, without a suitable framework, to gauge how these affect the PBs. In this work, we propose an interacting matrix model that couples SPEs with the PBs and consider the possible evolution scenarios and, in particular, those leading to crises and policrisis. We address specifically the situation where the PBs evolve according to the continuous logistic function, and then consider an exponentially-evolving SPE, which we show to cause a runaway effect on the PBs. We also propose a way to describe, classify, and compare sociopolitical syndromes, that is, a set composed of more than a single polycrisis.

Ultra-light scalar fields may explain the nature of the dark matter in our universe. If such scalars couple quadratically to particles of the Standard Model the scalar acquires an effective mass which depends on the local matter energy density. The changing mass causes the field to deviate from its cosmological value in experimental environments. In this work we show that the presence of a local over-density enclosing the experiment, for example a cavity, vacuum chamber, or satellite can strongly suppress the value of the scalar and its gradient in the interior. This makes detection of such scalar dark matter challenging, and significantly relaxes constraints on strongly coupled models. We also discuss the possibility that quadratically coupled ultra-light scalar dark matter could be detected by the differential measurement of the force on two cavities of the same mass but different internal structure.

We investigate the possibility that the high-energy neutrino flux observed from the Seyfert galaxy NGC 1068 originates from dark matter annihilations within the density spike surrounding the supermassive black hole at its center. The comparatively lower gamma-ray flux is attributed to a dark sector that couples predominantly to Standard Model neutrinos. To explain the absence of a corresponding neutrino signal from the center of the Milky Way, we propose two scenarios: (i) the disruption of the dark matter spike at the Milky Way center due to stellar heating, or (ii) the annihilation into a dark scalar that decays exclusively into neutrinos, with a decay length longer than the size of the Milky Way but shorter than the distance from Earth to NGC 1068.

We present a theoretical study of axion echoes in the context of multiple ALP models. We begin by reviewing the single ALP case, deriving the conditions for resonance and echo formation. Starting from a set of N ALPs coupling to the photon, we then derive the relevant echo equations for both coherent and incoherent configurations. In the former case, we show that the echo power scales with N leading to sharper amplification and potentially improving projected bounds discussed earlier in literature. Small mass splittings between the ALPs further increase this amplification, even for a N = 2 case. We also outline the potential experimental implications of our results and discuss prospects for detecting these echoes in a wide range of ALP masses. In the incoherent scenario, we show that the random phases lead to a suppression of the echo power, eventually resulting in observable signals akin to or even weaker than the single ALP case.

The conversion of gravitational to electromagnetic waves in the presence of background magnetic fields is known as the inverse Gertsenshtein effect, analogous to the Primakoff effect for axions. Rephrasing this conversion as a classical electrodynamics problem in the far-field regime of a magnetized region, we derive the angular distribution of the intensity and polarization of the emitted electromagnetic waves. We discuss the interplay of the internal structure of the magnetic field, the polarization of the gravitational wave and the scattering angle, demonstrating for example that a dipolar field can convert an unpolarized stochastic gravitational wave background into polarized electromagnetic emission, with peak emission intensity along the equator. We moreover outline how to incorporate medium effects in this framework, necessary for a realistic 3D description of gravitational wave to photon conversion in the magnetosphere of neutron stars.

Although light nuclear clusters are known to affect the properties of warm and dilute nuclear matter, their role in warm and dense nuclear matter remains unclear due to the lack of experimental evidence for their modifications by the Mott effect in such an environment. To address this issue, we resort to intermediate-energy heavy-ion collisions, where light clusters are mainly produced in the transiently formed warm and dense matter. A kinetic approach, which includes dynamically the formation and dissociation of light clusters, is employed to deduce the strength of the Mott effects and the $\alpha$-particle fraction in warm and dense nuclear matter from the light-nuclei yields measured by the FOPI Collaboration in central Au$+$Au collisions at energies of $0.25A$ to $0.6A~\rm GeV$. We find an unexpectedly abundant $\alpha$ clustering in this environment, which will have profound implications for modeling the nuclear equation of state and describing supernovae and neutron star mergers.

We explore a cosmological model in which dark matter is non-minimally coupled to gravity at the fluid level. While typically subdominant compared to Standard Model forces, such couplings may dominate dark matter dynamics. We show that this interaction modifies the early-time Friedmann equations, driving a phase of accelerated expansion that can resolve the horizon and flatness problems without introducing additional fields. At even earlier times, the coupling to spatial curvature may give rise to a cosmological bounce, replacing the initial singularity of standard cosmology. These results suggest that non-minimally coupled dark matter could offer a unified framework for addressing both the singularity and fine-tuning problems.

We study theories breaking diffeomorphism (Diff) invariance down to the subgroup of transverse diffeomorphisms (TDiff), consisting of multiple scalar fields in a cosmological background. In particular, we focus on models involving a field dominated by its kinetic term and a field dominated by its potential, coupled to gravity through power-law functions of the metric determinant. The Diff symmetry breaking results in the individual energy-momentum tensors not being conserved, although the total conservation-law is satisfied. Consequently, an energy exchange takes place between the fields, acting as an effective interaction between them. With this in mind, we consider the covariantized approach to describe the theory in a Diff invariant way but with an additional field, and discuss the phenomenological consequences of these models when it comes to the study of the dark sector.