Papers for Thursday, Jul 24 2025

The Mars Life Explorer (MLE) mission concept offers a critical opportunity to investigate whether extant life exists within the mid-latitude ice deposits of Mars. However, MLE's current science traceability matrix emphasizes habitability assessment and organic chemistry over direct life detection. As crewed missions to Mars may occur as early as 2040, the window for uncontaminated robotic exploration is rapidly closing. A high-confidence determination of Martian life must be achieved before irreversible anthropogenic contamination compromises scientific integrity. This paper evaluates the scientific, technical, and policy limitations of the current MLE architecture and recommends specific instrumentation upgrades and governance measures necessary to enable definitive and agnostic life detection while safeguarding planetary protection.

Enabled by planarized phase engineering, metalenses based on metasurfaces offer compact and scalable solutions for applications such as sensing, imaging, and virtual reality. They are particularly attractive for multi-pixel, large-scale heterodyne focal plane arrays in space observatories, where a flat metalens array on a silicon wafer can replace individual lenses, greatly simplifying system integration and beam alignment. In this work, we demonstrate, for the first time, a superconducting niobium nitride (NbN) hot electron bolometer (HEB) mixer coupled with a silicon-based metalens operating at terahertz frequencies. The metalens phase profile was derived from a finite-size Gaussian beam source using the Rayleigh-Sommerfeld diffraction integral, and its focusing behavior was validated through 2D simulation. Experimentally, the metalens-coupled NbN HEB receiver exhibited a noise temperature of 1800 K at 1.63 THz. The power coupling efficiency from free space to the mixer via the metalens was measured to be 25 %. Measured far-field beam profiles are Gaussian-like with sidelobes below -14 dB. These results demonstrate the feasibility of integrating metalenses with HEB mixers for THz detection, offering a scalable path for compact focal plane arrays in space-based THz instrumentation.

We present cosmological dark matter (DM)--only zoom-in simulations of a Milky Way (MW) analog originating from enhanced linear matter power spectra $P(k)$ relative to the standard cold, collisionless DM (CDM) cosmology. We consider a Gaussian power excess in $P(k)$ followed by a cutoff in select cases; this behavior could arise from early-universe physics that alters the primordial matter power spectrum or DM physics in the radiation-dominated epoch. We find that enhanced initial conditions (ICs) lead to qualitative differences in substructure relative to CDM. In particular, the subhalo mass function (SHMF) resulting from ICs with both an enhancement and cutoff is amplified at high masses and suppressed at low masses, indicating that DM substructure is sensitive to features in $P(k)$. Critically, the amplitude and shape of the SHMF enhancement depend on the wave number of the $P(k)$ excess and the presence or absence of a cutoff on smaller scales. These alterations to the SHMF are mainly imprinted at infall rather than during tidal evolution. Additionally, subhalos are found systematically closer to the host center and their concentrations are increased in scenarios with $P(k)$ enhancement. Thus, nonlinear mode coupling must be captured to enable $P(k)$ reconstruction using DM substructure.

Recent surveys show that $z>2$ quasars are surrounded by Hydrogen Lyman-$\alpha$ (Ly$\alpha$) glows with diverse emission levels and extents. These seem to depend on the activity of embedded quasars, the number of active galactic nucleus (AGN) photons able to reach the halo gas or circumgalactic medium (CGM) and the physical properties of the CGM. In this framework, we present VLT/MUSE snapshot observations (45 min/source) of 59 $z\sim3$ quasars extending the long-term QSO MUSEUM campaign to fainter SDSS sources. The whole survey now targets 120 quasars with a median redshift of $z$=3.13, and bolometric luminosities, black hole masses and Eddington ratios of $45.1<\log(L_{\rm bol}/[{\rm erg\,s^{-1}]})<48.7$, $7.9<\log(M_{\rm BH}/[{\rm M_{\odot}]})<10.3 $ and $0.01<\lambda_{\rm Edd}<1.8$, respectively. We detect extended Ly$\alpha$ emission in 110/120 systems, with all non-detections in the new fainter sample. Stacking non-detections unveils emission below our individual detection limit. The Ly$\alpha$ surface brightness (SB$_{\rm Ly\alpha}$) of the CGM increases with quasar luminosity. Moreover, the Ly$\alpha$ linewidth increases in the central regions (projected radius $R<40$ kpc or $\sim$40% $R_{\rm vir}$) of the CGM around brighter quasars. These trends indicate that we are witnessing the instantaneous AGN feedback in action on CGM scales. Assuming that all targeted quasars sit in halos of $M_{\rm DM}\sim10^{12.5}\,M_\odot$, as found in clustering studies, the trend in SB$_{\rm Ly\alpha}$ can be explained by larger fractions of cool gas mass illuminated, implying that brighter quasars have larger ionization cone opening angles. Similarly, brighter AGNs seem to perturb the cool ($T\sim10^4$ K) gas more strongly. We show that QSO MUSEUM now has enough statistics to study the instantaneous AGN feedback while controlling for black hole properties, which are key to constraining AGN models.

The X-SHYNE library is a homogeneous sample of 43 medium-resolution (R=8000) infrared (0.3-2.5um) spectra of young (<500Myr), low-mass (<20Mjup), and cold (Teff=600-2000K) isolated brown dwarfs and wide-separation companions observed with the VLT/X-Shooter instrument. To characterize our targets, we performed a global comparative analysis. We first applied a semi-empirical approach. By refining their age and bolometric luminosity, we derived key atmospheric and physical properties, such as Teff, mass, surface gravity (g), and radius, using the evolutionary model COND03. These results were then compared with the results from a synthetic analysis based on three self-consistent atmospheric models. To compare our spectra with these grids we used the Bayesian inference code ForMoSA. We found similar Lbol estimates between both approaches, but an underestimated Teff from the cloudy models, likely due to a lack of absorbers that could dominate the J and H bands of early L. We also observed a discrepancy in the log(g) estimates, which are dispersed between 3.5 and 5.5 dex for mid-L objects. We interpreted this as a bias caused by a range of rotational velocities leading to cloud migration toward equatorial latitudes, combined with a variety of viewing angles that result in different observed atmospheric properties (cloud column densities, atmospheric pressures, etc.). Finally, while providing robust estimates of [M/H] and C/O for individual objects remains challenging, the X-SHYNE library globally suggests solar values, which are consistent with a formation via stellar formation mechanisms. This study highlights the strength of homogeneous datasets in performing comparative analyses, reducing the impact of systematics, and ensuring robust conclusions while avoiding over-interpretation.

Existing expressions in the literature appear to indicate that Doppler boosting, due to our proper motion with respect to the isotropic frame of the universe, can amplify stochastic gravitational wave backgrounds whose energy spectra exhibit strong scale dependence, for example, those generated by large scalar perturbations in models of primordial black holes or by astrophysical populations with broken power-law behaviour. It has been suggested that this enhancement could increase the signal-to-noise ratio of such backgrounds in pulsar timing measurements, as well as in ground- and space-based observatories. We show that the reported enhancement is an artefact of a Taylor expansion of the boosted signal, typically performed in the literature under the assumption of a small boosting parameter. This approximation fails to reproduce the correct result for signals with strong scale dependence. When Doppler boosting is treated exactly, the apparent amplification disappears. Using representative spectra, we demonstrate that Doppler motion induces only blue- and red-shifting by the expected amount; it does not lead to additional amplification or introduce new spectral features. The exact expression for the kinematic boost can and should be easily applied in analysing such backgrounds.

X-ray reverberation, which exploits the time delays between variability in different energy bands as a function of Fourier frequency, probes the structure of the inner accretion disks and X-ray coronae of active galactic nuclei. We present a systematic X-ray spectroscopic and reverberation study of the high-Eddington-ratio narrow-line Seyfert 1 galaxy Ark 564, using over 900 ks of \textit{XMM-Newton} and \textit{NuSTAR} observations spanning 13 years. The time-averaged spectra can be well described by the a model consisting of a coronal continuum, relativistic disk reflection, warm Comptonization, and three warm absorbers. Leveraging the high X-ray brightness of Ark 564, we are able to resolve the time evolution of the spectra and contemporaneous reverberation lags. The soft-band lag relative to the continuum increases with the X-ray flux, while Fe K$\alpha$ lags are detected in only a subset of epochs and do not correlate with soft lags. Models based on a lamppost corona and reflection from a standard thin disk can broadly reproduce the observed lag-energy spectra of low-flux epochs; however, additional reverberation from the warm Comptonized atmosphere is required to explain the soft lags observed in high-flux epochs. A vertically puffed-up inner disk and a variable, vertically extended corona can better explain the observed evolution of the lags and covariance spectra. Our study underscores the importance of multi-epoch, multi-band analyses for a comprehensive understanding the inner accretion disk and corona.

Gravitational waves emitted from core-collapse supernova explosions are critical observables for extracting information about the dynamics and properties of both the progenitor and the post-bounce~evolution of the system. They are prime targets for current interferometric searches and represent a key milestone for the capabilities of next-generation interferometers. This study aims to characterize how the gravitational waveform associated with prompt stellar convection depends on the rotational rate and magnetic field topology of the progenitor star. We carry out a series of axisymmetric simulations of a $16.5\,\mathrm{M}_\odot$ red supergiant with five configurations of initial magnetic fields and varying degrees of initial rotation. We then analyze the contribution of early-time convection and the proto-neutron star core to the waveform using ensemble empirical mode decomposition, alongside spectral and Fourier analyses, to facilitate comparison and interpretation of the results. Our simulations reveal that early post-bounce gravitational waves signals are dominated by the first six intrinsic mode functions, with variations due to rotation and magnetic fields influencing the signal strength. Strong magnetic fields decelerate core rotation, affecting mode excitation. Regardless of the initial rotation, convection consistently drives a low-frequency mode that lasts throughout the evolution. Additionally, our results show that the bounce signal is not consistently the strongest component of the waveform. Instead, we find that prompt convection generates a post-bounce signal of comparable or even greater amplitude.

We present a unified spin-weighted harmonic framework that delivers analytic, diagonal expressions for the overlap (correlation) functions of three low frequency gravitational wave observables-pulsar timing redshifts, astrometric deflections, and time-dependent image distortions (``shimmering''). Writing each response in spin-$s$ spherical harmonics and rotating to a basis in which the wave tensor has definite helicity, we obtain compact closed-form series for every auto- and cross-correlation, recovering the Hellings-Downs curve as the $s=0$ limit and deriving its astrometric ($s=\pm 1$) and shimmering ($s=\pm 2$) analogues. The formalism naturally extends to non-standard scalar-breathing, longitudinal, and vector polarisation modes, clarifying when higher-spin observables are (and are not) sourced and providing a complete set of harmonic spectra $C_\ell$ ready for parameter estimation pipelines. These results supply the common theoretical language needed to combine upcoming pulsar timing, Gaia-class astrometric, and high resolution imaging data sets, enabling coherent, multi probe searches for stochastic gravitational wave backgrounds, tests of general relativity and its alternatives across the nano- to micro-hertz gravitational wave band.

Type Ia supernovae (SNe Ia) are pivotal for the origins of the elements, the understanding of galactic chemical evolution, and serve as crucial cosmological distance indicators, yet their progenitor systems remain a central enigma in astrophysics. While both the growth of white dwarfs to near-Chandrasekhar mass and their explosion (the single-degenerate; SD) and mergers of two WDs leading to explosions (double-degenerate; DD) scenarios have been proposed, neither explains the observed diversity of thermonuclear transients and their properties, including the fainter Type Iax supernovae (SNe Iax). Here we show, through comprehensive three-dimensional hydrodynamic simulations, that as accreting WDs grow towards the Chandrasekhar mass (the SD channel), premature carbon ignition at sub-Chandrasekhar densities can trigger partial deflagrations that eject substantial mass in low-energy Iax outbursts. Such a process effectively serves as a self-limiting feedback loop, which stalls further mass growth. It naturally explains why the SD channel is precluded from producing standard, normal SNe Ia, and instead predominantly yields SNe Iax. Our findings significantly reframe the SD versus DD debate, with important implications for supernova rates, galactic chemical enrichment, and cosmological measurements.

Coronal plumes are narrow, collimated structures that are primarily viewed above the solar poles and in coronal holes in the extreme ultraviolet, but also in sunspots. Open questions remain about plume formation, including the role of small-scale transients and whether plumes embedded in different magnetic field configurations have similar formation mechanisms. We report on coordinated Solar Orbiter/Extreme Ultraviolet Imager (EUI), Interface Region Imaging Spectrograph, and Solar Dynamics Observatory observations of the formation of a plume in sunspot penumbra in 2022 March. During this observation, Solar Orbiter was positioned near the Earth-Sun line and EUI observed at a 5 s cadence with a spatial scale of 185 km pixel$^{-1}$ in the solar corona. We observe fine-scale dots at various locations in the sunspot, but the brightest and highest density of dots is at the plume base. Space-time maps along the plume axis show parabolic and V-shaped patterns, and we conclude that some of these dots are possible signatures of magneto-acoustic shocks. Compared to other radial cuts around the sunspot, along the plume shows the longest periods (~7 minutes) and the most distinct tracks. Bright dots at the plume base are mostly circular and do not show elongations from a fixed origin, in contrast to jetlets and previously reported penumbral dots. We do not find high-speed, repeated downflows along the plume, and the plume appears to brighten coherently along its length. Our analysis suggests that jetlets and downflows are not a necessary component of this plume's formation, and that mechanisms for plume formation could be dependent on magnetic topology and the chromospheric wave field.

A star destroyed by the tidal field of a supermassive black hole (SMBH) in a tidal disruption event (TDE) gives rise to a luminous flare. TDEs are being detected at an ever-increasing rate, motivating the need for accurate models of their lightcurves. The ``maximum gravity'' (MG) model posits that a star is completely destroyed when the tidal field of the SMBH exceeds the maximum self-gravitational field within the star, $g_{\rm max}$, and predicts the peak fallback rate $\dot{M}_{\rm peak}$ and the time to peak $t_{\rm peak}$. Here we perform hydrodynamical simulations of the complete disruption of 24 stars with masses ranging from $0.2-5.0 M_\odot$, at different stages of their main sequence evolution, to test the predictions of this model. We find excellent agreement between the MG model predictions and our simulations for stars near the zero-age main sequence, while the predictions are less accurate (but still within $\sim 35-50\%$ of the simulation results) for highly evolved stars. We also generalize the MG model to incorporate the Paczy{ń}ski-Wiita potential to assess the impact of strong-gravity effects -- which are especially important for deep encounters that are required to completely destroy evolved and centrally concentrated stars -- and find good agreement with recent works that include relativistic gravity. Our results demonstrate that this model provides accurate constraints on the peak timescale of TDE lightcurves and their correlation with black hole mass.

Context. Based on Local Universe observations, quiescent galaxies (QGs) host lower to no HI compared to star-forming galaxies (SFGs), but no constraints have been derived so far at higher redshift (z>0.1). Understanding whether QGs can retain significant HI reservoirs at higher z is crucial to refine quenching and gas accretion models and to constrain overall star formation efficiency at different epochs. Aims. We aim to probe HI in candidate QGs at intermediate redshifts (z=0.36) and to understand whether there exists a class of QGs retaining consistent HI reservoirs and which parameters (dust content, stellar mass, Dn4000, morphology, environment) effectively capture HI-rich QGs. Methods. We perform 21-cm spectral line stacking on MIGHTEE-HI data at z=0.36, targeting two different samples of QGs, defined by means of a color-selection criterion and a spectroscopic criterion based on Dn4000, respectively. We also perform stacking on subsamples of the spectroscopically-selected quiescent sample to investigate the correlation between the HI content and other galaxy properties. Results. We find that QGs with an IR counterpart (i.e., dusty galaxies) are found to host a substantial HI content, on average just 40% lower than SFGs. In contrast, color-selected QGs still hold HI, but lower than SFGs by a factor 3. Among dusty objects, we find morphology to have a mild impact on the atomic gas content, with spirals hosting approximately 15-30% more HI than spheroids. Environmental effects are also present, with low-density regions hosting galaxies that are HI-richer than in high-density ones, by approximately 30% for spirals and 60% for spheroids. We suggest that, in general, HI content is driven by several factors, including quenching mechanisms and ISM enrichment processes. Also, quiescent galaxies - and especially dusty systems - seem to yield HI more consistently than in the Local Universe.

Advancing our understanding of the formation and evolution of early massive galaxies and black holes requires detailed studies of dense structures in the high-redshift Universe. In this work, we present high-angular resolution ($\simeq0.3''$) ALMA observations targeting the CO(4--3) line and the underlying 3-mm dust continuum toward the Cosmic Web node MQN01, a region identified through deep multiwavelength surveys as one of the densest concentrations of galaxies and AGN at cosmic noon. At the center of this structure, we identify a massive, rotationally supported disk galaxy located approximately at $\sim10\,{\rm kpc}$ projected-distance and $\sim-300\,{\rm km\,s^{-1}}$ from a hyperluminous quasar at $z=3.2510$. By accurately modeling the cold gas kinematics, we determine a galaxy dynamical mass of $2.5\times10^{11}\,{M_{\odot}}$ within the inner $\simeq 4\,{\rm kpc}$, and a high degree of rotational support of $V_{\rm rot}/\sigma \approx 11$. This makes it the first quasar companion galaxy confirmed as a massive, dynamically cold rotating disk at such an early cosmic epoch. Despite the small projected separation from the quasar host, we find no clear evidence of strong tidal interactions affecting the galaxy disk. This might suggest that the quasar is a satellite galaxy in the early stages of a merger. Furthermore, our spectroscopic analysis reveals a broad, blueshifted component in the CO(4--3) line profile of the quasar host, which may trace a powerful molecular outflow or kinematic disturbances induced by its interaction with the massive companion galaxy. Our findings show that rotationally supported cold disks are able to survive even in high-density environments of the early Universe.

Observations over the past decade have shown that galaxy clusters undergo the most transformative changes during the $z = 1.5 - 2$ epoch. However, challenges such as low lensing efficiency, high shape measurement uncertainty, and a scarcity of background galaxies have prevented us from characterizing their masses with weak gravitational lensing (WL) beyond the redshift $z\sim1.75$. In this paper, we report the successful WL detection of JKCS 041 and XLSSC 122 at $z=1.80$ and $z=1.98$, respectively, utilizing deep infrared imaging data from the Hubble Space Telescope with careful removal of instrumental effects. These are the most distant clusters ever measured through WL. The mass peaks of JKCS 041 and XLSSC 122, which coincide with the X-ray peak positions of the respective clusters, are detected at the $\sim3.7\sigma$ and $\sim3.2\sigma$ levels, respectively. Assuming a single spherical Navarro-Frenk-White profile, we estimate that JKCS 041 has a virial mass of $M_{200c} = (5.4\pm1.6) \times 10^{14} M_{\odot}$ while the mass of XLSSC 122 is determined to be $M_{200c} = (3.3\pm1.8) \times 10^{14} M_{\odot}$. These WL masses are consistent with the estimates inferred from their X-ray observations. We conclude that although the probability of finding such massive clusters at their redshifts is certainly low, their masses can still be accommodated within the current $\Lambda$CDM paradigm.

The source of extragalactic neutrinos in the TeV-PeV range is a matter of very active research, with blazar jets having been postulated to be the origin of at least some of the detections. The blazar PKS 0735+178 is a prominent example; during its multi-band flare in late 2021 a neutrino event was reported by four observatories, with its origin consistent with the direction of that source. While no new jet component was observed to be ejected during that narrow time-frame, our analysis shows that a propagating shock front originating from the core region was the likely source of the multi-band flare, using very-long-baseline interferometry images of PKS 0735+178 in polarised light. Taken together, our findings are suggestive of a coherent scenario in which the shock may contribute to the acceleration of protons, with the target photons potentially originating either from the ambient medium surrounding the jet or from proton synchrotron radiation. The necessary conditions for neutrino emission via proton-photon interactions are, hence, present in this jet.

Traditional N-body methods introduce localised perturbations in the gravitational forces governing their evolution. These perturbations lead to an artificial fragmentation in the filamentary network of the Large Scale Structure, often referred to as "beads-on-a-string." This issue is particularly apparent in cosmologies with a suppression of the matter power spectrum at small spatial scales, such as warm dark matter models, where the perturbations induced by the N-body discretisation dominate the cosmological power at the suppressed scales. Initial conditions based on third-order Lagrangian perturbation theory, which allow for a late-starting redshift, have been shown to minimise numerical errors contributing to such artefacts. In this work, we investigate whether the additional use of a spatially adaptive softening for dark matter particles, based on the gravitational tidal field, can reduce the severity of artificial fragmentation. Tidal adaptive softening significantly improves force accuracy in idealised filamentary collapse simulations over a fixed softening approach. However, it does not substantially reduce spurious haloes in cosmological simulations when paired with such optimised initial conditions. Nevertheless, tidal adaptive softening induces a shift in halo formation times in warm dark matter simulations compared to a fixed softening counterpart, an effect not seen in cold dark matter simulations. Furthermore, initialising the initial conditions at an earlier redshift generally results in z=0 haloes forming from Lagrangian volumes with lower average sphericity. This sphericity difference could impact post-processing algorithms identifying spurious objects based on Lagrangian volume morphology. We propose potential strategies for reducing spurious haloes without abandoning current N-body methods.

Context. Astrochemical modeling requires, as input, the effective column density of gas (or extinction) that attenuates an external, isotropic, far-ultraviolet radiation field. In three-dimensional simulations, this can be calculated through ray-tracing schemes, while in 0D chemical models it is often treated as a free parameter. Aims. We aim to produce an analytic, physically motivated formalism to predict the average relationship between the effective hydrogen-nuclei column density, $N_{\rm eff}({\rm H})$, and the local hydrogen-nuclei number density, $n_{\rm H}$. Methods. We construct an analytic model utilizing characteristic length scales that connects the turbulence-dominated regime and the gravitational-dominated regime at high-density. Results. The model well-reproduces a previous analytic fit to simulation results and is consistent with the high-density power-law indices, e.g., $N_{\rm eff}(H) \propto n^{\gamma}$, of $\gamma \approx 0.4 - 0.5$ found in previous numerical simulations utilizing ray-tracing. Conclusions. We present an analytic model relating the average effective column density, $N_{\rm eff}$, to the local number density, $n_{\rm H}$, which reproduces the behaviors found in three-dimensional simulations. The analytic model can be utilized as a sub-grid prescription for shielded molecular gas or in astrochemical models for a physically motivated estimation of the attenuating column density.

Using pulsar accelerations, we identify and constrain the properties of a dark matter sub-halo in the Galaxy for the first time from analyzing the excess, correlated power in the acceleration field of binary pulsars. We find that this sub-halo has a mass of $1.02^{+3.47}_{-0.90} \times 10^{7}~M_{\odot}$ and is located at Galactic coordinates $d = 0.93^{+0.32}_{-0.38}$ kpc, $b=36.78^{+17.59}_{-23.55}$, $l=30.16^{+19.36}_{-23.82}$, or equivalently at Galactocentric coordinates $X = 7.52^{+0.34}_{-0.38}~\rm$ kpc, $Y = 0.36^{+0.39}_{-0.43} ~\rm kpc$, $Z = 0.53^{+0.41}_{-0.45} ~\rm kpc$. We examine \textit{Gaia} data and the atomic and molecular hydrogen data of our Galaxy and show that this excess power cannot arise from the gas or the stars in our Galaxy. Additionally, by analyzing the full sample of binary pulsars with available acceleration measurements that span 3.4 kpc in Galactocentric radius from the Sun and 3.6 kpc in vertical height, we find that massive (with mass $>10^{8}~M_{\odot}~$) sub-halos are disfavored for the Milky Way within several kiloparsec of the Sun. The detection of a $10^{7}~M_{\odot}$ sub-halo within a few kpc of the Sun is potentially consistent with the expected number counts of sub-halos in the prevailing $\Lambda$CDM paradigm, for a substantial sub-halo mass fraction. The pulsar accelerations are however better fit by a compact object, such as arising from a primordial black hole or a sub-halo having a steep density profile, as in self-interacting dark matter. As the number and precision of direct acceleration measurements continues to grow, we will obtain tighter constraints on dark matter sub-structure in our Galaxy. These measurements now open a new avenue for studying dark matter and have implications across many fields of astrophysics - from understanding the nature of dark matter to galaxy formation.

Measuring properties of young stellar objects (YSOs) is necessary for probing the pre-main-sequence evolution of stars. As YSOs exhibit complex geometry, measurement generally entails comparing observed radiation to template populations of radiative-transfer model YSO spectral energy distributions (SEDs). Due to uncertainty on the precise mechanics of star formation, the properties inferred for YSOs using these models often depend strongly on the assumed accretion history. We develop a framework for predicting observable properties of YSOs that is agnostic to the underlying accretion history, enabling comparison between theories. This framework links a set of radiative-transfer SEDs with protostellar evolutionary tracks to create models of evolving YSOs. Unlike previous works, we directly relate evolution models to observables through theoretical physical parameters rather than through intermediate, observationally derived analogues. We make flux predictions for YSOs corresponding to stars with birth masses from 0.2 to 50 $M_\odot$ during their accretion phase following isothermal-sphere, turbulent-core, and competitive accretion histories, showing that these histories may be observationally distinguished by examining the 100-$\mu$m and 3-mm fluxes of a YSO. We discuss the impact of dust models and parameter ranges on the output of radiative transfer simulations through a comparison to another SED model grid. We quantify the degree of confusion between YSO Stages and Classes across a wide range of physical scenarios; for each, we calculate confusion matrices that enable inference of the number of objects of a given Stage from an observed population. Finally, we critically examine the physical significance of various literature Stage and Class definitions.

At any given scale, 3$\times$2-point statistics extract only three numbers from the joint distribution of the cosmic matter density and galaxy density fluctuations: their variances and their covariance. It is well known that the full shape of the PDF of those fluctuations contains significantly more information than can be accessed through these three numbers. But the study of the PDF of cosmic density fluctuations in real observational data is still in its infancy. Here we present \verb|CosMomentum|, a public software toolkit for calculating theoretical predictions for the full shape of the joint distribution of a line-of-sight projected tracer density and the gravitational lensing convergence. We demonstrate that an analysis of this full shape of the PDF can indeed disentangle complicated tracer bias and stochasticity relations from signatures of cosmic structure growth. Our paper also provides back-drop for an upcoming follow-up study, which prepares PDF analyses for application to observational data by incorporating the impact of realistic weak lensing systematics.

O-C shell mergers in massive stars are a site for producing the p nuclei by the $\gamma$ process, but 1D stellar models rely on mixing length theory, which does not match the radial velocity profiles of 3D hydrodynamic simulations. We investigate how 3D macro physics informed mixing impacts the nucleosynthesis of p nuclei. We post-process the O-shell of the $M_\mathrm{ZAMS} = 15~\mathrm{M}_\odot$, $Z = 0.02$ model from the NuGrid stellar data set. Applying a downturn to velocities at the boundary and increasing velocities across the shell as obtained in previous results, we find non-linear, non-monotonic increase in p-nuclei production with a spread of 0.96 dex, and find that isotopic ratios can change. Reducing C-shell ingestion rates as found in 3D simulations suppresses production, with spreads of 1.22-1.84 dex across MLT and downturn scenarios. Applying dips to the diffusion profile to mimic quenching events also suppresses production, with a 0.51 dex spread. We analyze the impact of varying all photo-disintegration rates of unstable n-deficient isotopes from Se-Po by a factor of 10 up and down. The nuclear physics variations for the MLT and downturn cases have a spread of 0.56-0.78 dex. We also provide which reaction rates are correlated with the p nuclei, and find few correlations shared between mixing scenarios. Our results demonstrate that uncertainties in mixing arising from uncertain 3D macro physics are as significant as nuclear physics and are crucial for understanding p-nuclei production during O-C shell mergers quantitatively.

Recent baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) collaboration have renewed interest in dynamical dark energy models, particularly those that cross the "phantom divide" ($w_{\rm DE} = -1$). We present the first observational constraints on monodromic k-essence, a physically motivated scalar field dark energy scenario capable of realizing rapid oscillations about the phantom divide. Using cosmic microwave background (CMB) information, DESI DR2 BAO measurements, and Type Ia supernovae observations, we constrain the amplitude, frequency, phase, and power-law index describing the monodromic k-essence scenario at the background level. We find that the monodromic dark energy scenario can fit these datasets with a $\chi^2$ that is comparable to the phenomenological $w_0$-$w_a$ parametrization. While the CMB and BAO data alone are consistent with the standard $\Lambda$CDM model, the inclusion of DESY5 supernovae shows a preference for a non-zero amplitude, $A=0.44^{+0.16}_{-0.12}$ (fully marginalized 68% C.L.). Conversely, inclusion of the Pantheon-Plus supernovae provides no evidence for monodromic k-essence, with $A<0.43$ (95% C.L.). We show that constraints on both monodromic dark energy and $w_0$-$w_a$ models are sensitive to the DESI DR2 LRG2 BAO distance, especially in the absence of supernovae data.

The evolution of the magnetism, winds and rotation of low-mass stars are all linked. One of the most common ways to probe the magnetic properties of low-mass stars is with the Zeeman-Doppler imaging (ZDI) technique. The magnetic properties of partially convective stars has been relatively well explored with the ZDI technique, but the same is not true of fully convective stars. In this work, we analyse a sample of stars that have been mapped with ZDI. Notably, this sample contains a number of slowly rotating fully convective M dwarfs whose magnetic fields were recently reconstructed with ZDI. We find that the dipolar, quadrupolar and octupolar field strengths of the slowly rotating fully convective stars do not follow the same Rossby number scaling in the unsaturated regime as partially convective stars. Based on these field strengths, we demonstrate that previous estimates of spin-down torques for slowly rotating fully convective stars could have been underestimated by an order of magnitude or more. Additionally, we also find that fully convective and partially convective stars fall into distinct sequences when comparing their poloidal and toroidal magnetic energies.

Solar Energetic Particle (SEP) events are critical for understanding particle acceleration and transport in the heliosphere. While most SEP events involve outward streaming particles along open magnetic field lines, bidirectional events characterized by simultaneous sunward and anti-sunward particle flows offer unique insights into magnetic field topology and the interplay of multiple acceleration sources. We aim to investigate the origin and transport of energetic particles in two rare bidirectional anisotropic SEP events observed by Solar Orbiter. Both events showed two clear velocity dispersion signatures with opposite particle anisotropies during their onset phase. The sunward streaming protons, characterized by delayed release time, harder spectral index, and higher intensities, may be attributed to coronal mass ejection-driven shock acceleration, while the promptly released anti-sunward streaming protons are likely linked to flare acceleration. Notably, in both cases, small-scale flux ropes were identified in situ during the time intervals corresponding to the bidirectional particle streaming. Path lengths derived for sunward and anti-sunward injections were substantially greater than nominal values of the Parker field lines, further supporting the role of the flux rope in shaping particle trajectories. These observations demonstrate that magnetic flux rope could significantly affect magnetic connectivity to the source region and SEP propagation in the inner heliosphere, while simultaneous velocity dispersion from two distinct particle sources allows for direct constraints on the topology of the flux rope. Our results highlight the value of combining particle anisotropy, release time, source spectra, and magnetic structure diagnostics to unravel SEP transport in complex transient magnetic structures, and also present new challenges for the current SEP transport model.

The CM Draconis system is a well-studied, double-lined spectroscopic binary that is totally eclipsing and exhibits strong magnetic activity. Nearly one million photometric measurements have been collected across multiple wavelengths over more than half a century. In addition to showing frequent flare activity and apsidal motion, CM Dra also hosts a distant white dwarf and has been proposed to harbor a Jupiter-sized circumbinary companion. At only 47 light-years from Earth, it remains one of the most observationally rich and dynamically intriguing low-mass binary systems. We present a comprehensive photometric and spectroscopic analysis of the system using new ground-based observations and data from 19 sectors of the \textit{TESS} mission. We derive precise fundamental parameters for both components: $M_1 = 0.2307 \pm 0.0008\,M_\odot$, $M_2 = 0.2136 \pm 0.0008\,M_\odot$, $R_1 = 0.2638 \pm 0.0011\,R_\odot$, $R_2 = 0.2458 \pm 0.0010\,R_\odot$, $L_1 = 0.0060 \pm 0.0005\,L_\odot$, and $L_2 = 0.0050 \pm 0.0004\,L_\odot$. The derived distance ($14.4 \pm 0.6$ pc) is consistent with \textit{Gaia} DR3 measurements. Eclipse timing variations (ETVs) spanning over five decades were analyzed in detail. A long-period ($\sim$56 yr) modulation was identified, which may be attributed either to the light-time effect of a possible circumbinary companion or to magnetic activity cycles. While the Bayesian Information Criterion statistically favors the model involving a light-time effect from a planetary companion, stellar activity remains a viable alternative that cannot yet be ruled out. Our results demonstrate that CM Dra is a valuable test case for studying both stellar activity and the potential presence of circumbinary companions in multiple-star systems. Continued long-term monitoring will be essential to distinguish between these competing scenarios.

Massive stars lose a significant fraction of their mass through stellar winds at various stages of their lives, including on the main sequence, during the red supergiant phase, and as evolved helium-rich Wolf--Rayet stars. In stellar population synthesis, uncertainty in the mass-loss rates in these evolutionary stages limits our understanding of the formation of black holes and merging compact binaries. In the last decade, the theoretical predictions, simulation, and direct observation of wind mass-loss rates in massive stars have improved significantly, typically leading to a reduction in the predicted mass-loss rates of massive stars. In this paper we explore the astrophysical implications of an updated treatment of winds in the COMPAS population synthesis code. There is a large amount of variation in predicted mass-loss rates for massive red supergiants; some of the prescriptions we implement predict that massive red supergiants are able to lose their hydrogen envelopes through winds alone (providing a possible solution to the so-called missing red supergiant problem), while others predict much lower mass-loss rates that would not strip the hydrogen envelope. We discuss the formation of the most massive stellar-mass black holes in the Galaxy, including the high-mass X-ray binary Cygnus X-1 and the newly discovered Gaia BH3. We find that formation rates of merging binary black holes are sensitive to the mass-loss rate prescriptions, while the formation rates of merging binary neutron stars and neutron-star black hole binaries are more robust to this uncertainty.

We present the first robust helium (He) abundance measurements in star-forming galaxies at redshifts $1.6\lesssim z\lesssim 3.3$ using deep, moderate-resolution JWST/NIRSpec spectroscopy from the AURORA survey. We establish a High$-z$ HeI Sample consisting of 20 galaxies with multiple high-S/N ($>5\sigma$) HeI emission-line detections, including the critical near-infrared $\lambda$10833 line. This is the first study at high redshift leveraging $\lambda$10833 to break degeneracies between temperature, electron density, optical depth, and He$^+$/H$^+$, enabling reliable He abundance determinations in the early universe. We use a custom MCMC framework incorporating direct-method electron temperature priors, extended optical depth ($\tau_{\lambda3890}$) model grids up to densities of $10^6$~cm$^{-3}$, and simultaneous fits of the physical conditions and HeI/HI line ratios to derive ionic He$^+$/H$^+$ abundances. Most of the AURORA galaxies follow the extrapolated $z\sim0$ He/H-O/H trend, indicating modest He enrichment by $z\sim2-3$. However, we identify a subpopulation of four galaxies that exhibit elevated He mass fractions ($\Delta Y>0.03$) without corresponding enhancements in N/O or $\alpha$-elements ($\sim20$% of the sample). This abundance pattern is inconsistent with enrichment from asymptotic giant branch stars, but favors early He enrichment from very massive stars (VMSs; $M\gtrsim100\ M_\odot$), which can eject He-rich, N-poor material via stellar winds and binary stripping in young stellar populations. We speculate that these elevated-He systems may represent an early phase of globular cluster (GC) formation where N enrichment is still lagging behind He production. This work demonstrates the power of JWST multi-line HeI spectroscopy for tracing early stellar feedback, enrichment pathways, and GC progenitor signatures in the high-z universe.

Motivated by the diversity of circumstellar planets in binary stars and the strong effects of the secular resonances of Jupiter and Saturn on the formation and architecture of the inner solar system, we have launched an expansive project on studying the effects of secular resonances on the formation of terrestrial planets around a star of a moderately close binary. As the first phase of our project, we present here the general theory of secular resonances in dual-star systems where the primary hosts two giant planets. Using the concept of generalized disturbing function, we derive the formula for the locations of secular resonances and show that in systems where the perturbation of the secondary star is stronger, the locations of secular resonances are farther way from the primary and closer to the giant planets. The latter implies that in such systems, terrestrial planet formation has a larger area to proceed with more of the protoplanetary disk being available to it. To demonstrate the validity of our theoretical results, we simulated the evolution of a protoplanetary disk interior to the inner giant planet. Results, in addition to confirming our theoretical predictions, pointed to an important finding: In binary stars, the perturbation of the secondary suppresses the secular resonances of giant planets. Simulations also show that as the disk loses material, secular resonances move inward, scattering objects out of the disk and/or facilitating their collisional growth. We present results of our study and discuss their implications for the simulations of terrestrial planet formation.

Continuing our study of the effects of secular resonances on the formation of terrestrial planets in moderately close binary stars, we present here the results of an extensive numerical simulations of the formation of these objects. Considering a binary with two giant planets and a protoplanetary disk around its primary star, we have simulated the late stage of terrestrial planet formation for different types of the secondary, and different orbital elements of the binary and giant planets. Results demonstrate that terrestrial planet formation can indeed proceed constructively in such systems; however, as predicted by the general theory, secular resonances are suppressed and do not contribute to the formation process. Simulations show that it is in fact the mean-motion resonances of the inner giant planet that drive the dynamics of the protoplanetary disk and the mass and orbital architecture of the final bodies. Simulations also show that in the majority of the cases, the final systems contain only one terrestrial planet with a mass of 0.6-1.7 Earth masses. Multiple planets appear on rare occasions in the form of Earth-Mars analogs with the smaller planet in an exterior orbit. When giant planets are in larger orbits, the number of these double-planet systems increases and their planets become more massive. Results also show that when the orbits of the giant planets carry inclinations, while secular resonances are still suppressed, mean-motion resonances are strongly enhanced, drastically reducing the efficacy of the formation process. We present the results of our simulations and discuss their implications.

Many extreme velocity candidate stars have been found based on \textit{Gaia} astrometry, but need spectroscopic confirmation. We select late-type hypervelocity star (HVS) candidates from the \textit{Gaia} DR3 catalog with a $1\sigma$ lower limit of the tangential velocity of 800 km\,s$^{-1}$. J1903-0023, one of the brightest targets, stands out as high priority candidate for follow-up spectroscopy using the X-shooter instrument at ESO-VLT. We determine its atmospheric parameters and abundances utilizing synthetic spectral grids and a global $\chi^2-$minimization procedure, and its stellar parameters with the help of evolutionary tracks and the spectral energy distribution. The star shows variability in its light curve and follow-up spectroscopy confirms that the star is radial-velocity variable. The spectroscopic distance of J1903-0023 is lower than that based on the parallax, indicating that the star is not a hypervelocity binary star but bound to the Galaxy. The star turned out to be of spectral type F, very similar to the extreme-velocity star J0725-2351, which we analyse in the same way as the target. Apparently, both stars are very metal poor and old halo main-sequence (sdF) stars with masses slightly below the halo turn-off mass, and share the low metallicity ([Fe/H]=-2.3,-2.6) and strong alpha enhancement ([$\alpha$/Fe]$\sim0.44$). While J0725-2351 is non-rotating ($v\sin\,i<3$\,km\,s$^{-1}$), J1903-0023 is a fast rotator ($v\sin i=42.3\pm2.0$ km\,s$^{-1}$). The Gaia, and ZTF light curves show an eclipse at a 1.179 day period, similar to the rotation period of J1903-0023. We therefore conclude that J1903-0023 is a high-velocity tidally-synchronised binary most likely with a metal-poor M dwarf companion.

The cosmic distance duality relation (CDDR) is a fundamental and practical condition in observational cosmology that connects the luminosity distance and angular diameter distance. Testing its validity offers a powerful tool to probe new physics beyond the standard cosmological model. In this work, for the first time, we present a novel consistency test of CDDR by combining HII galaxy data with a comprehensive set of Baryon Acoustic Oscillations (BAO) measurements. The BAO measurements include two-dimensional (2D) BAO and three-dimensional (3D) BAO, as well as the latest 3D BAO data from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2). We adopt four different parameterizations of the CDDR parameter, $\eta(z)$, to investigate possible deviations and their evolution with cosmic time. To ensure accurate redshift matching across datasets, we reconstruct the distance measures through a model-independent Artificial Neural Network (ANN) approach. Our analysis uniquely examines two distinct approaches: $i)$ marginalization over the BAO sound horizon $r_d$, and $ii)$ fixing $r_d$ to specific values. We find no significant deviation from the CDDR (less than 68% confidence level) in either the marginalized $r_d$ or the $r_d=147.05$ Mpc scenario. However, a slight deviation at the 68% confidence level is found when applying 2D-BAO data with $r_d=139.5$ Mpc. Furthermore, our analysis shows that all BAO data considered in this work support the validity of the CDDR, where 3D-DESI BAO provides the tightest constraints. We find no tension between 2D and 3D BAO measurements, which confirms their mutual consistency. In addition, the treatment of the sound horizon $r_d$ significantly impacts $\eta(z)$ constraints, which proves its importance in CDDR tests. Finally, the consistency of our results supports the standard CDDR and demonstrates the robustness of our analytical approach.

The photometric solutions of NW Aps reveal that it is a low mass ratio ($q = 0.086$) contact binary system. Investigation of orbital period shows that its orbital period is increasing continuously at a rate of $dP/dt=+1.117(\pm0.005)\times{10^{-6}}day\cdot year^{-1}$, which may be caused by mass transfer from the less massive component to the more massive one at a rate of $\frac{dM_{2}}{dt}=-3.36(\pm0.02)\times{10^{-8}}M_\odot/year$. A cyclic variation of $P_3 = 22.9(\pm0.1)$ is also found in the O - C curve. There may be a potential compact object orbiting around NW Aps, with its minimum mass to be $M_3 = 0.436(\pm0.007)M_\odot$. However, the magnetic activity of the primary star may also account for the cyclic change. NW Aps is a stellar merger candidate with the longest orbital period among all stellar merge candidates with mass ratio $q < 0.1$. It is still in a stable state since the ratio of orbital angular momentum ($J_{orb}$) to spin angular momentum ($J_{spin}$) is $\frac{J_{orb}}{J_{spin}}$ = 3.257. Both of its primary and secondary star are oversized to main sequence stars, and the surface gravity of the primary and secondary stars are significant lower than main sequence stars. The P - log g relationship is fitted with parabola for low mass ratio contact binary systems. More targets laid in the gap are needed to confirm the P - log g relationship and reveal the final evolutionary state of low mass ratio contact binary system.

Observations of the lunar exosphere provide valuable insights into dynamic processes affecting the Moon, such as meteoroid bombardment. The Chamberlain model was employed to estimate the zenith column density and temperature of Na atoms on August 13/14, 2009, after the peak of the Perseid meteor shower. Additionally, the column density and temperature of Na atoms delivered to the lunar exosphere by gradual processes during the peak on August 12/13, 2009, were estimated. Expected ratios of line-of-sight column densities of Na atoms at three observed altitudes on August 12/13, 2009, were obtained using the Chamberlain model and Monte Carlo simulations. The heightened intensities of Na emission lines on August 12/13, 2009, are attributed to the onset of the third short-term peak in Perseid activity predicted by celestial mechanics. The best agreement between observations and theoretical models was achieved with a theoretical temperature of 3000 K for impact-produced Na atoms. This third peak of Perseids began between 23:29 and 23:41 UT on August 12, 2009, lasting approximately 83 minutes, with a mass flux attributed to the Perseids ranging between 1.6 x 10^-16 and 5 x 10^-16 g cm^-2 s^-1. Additionally, depletion of Li content compared to Na content in the lunar exosphere was detected. A model predicting Perseid meteoroid stream activity on the Moon was developed and compared with spectral observations of the lunar exosphere. By modeling 25,000 years of comet 109P/Swift-Tuttle's orbits, 175 cometary trails likely to have generated meteoroids near Earth and the Moon during the Perseid 2009 meteor shower were identified. Our results reveal annual maxima inducing filament trail structures, one of which closely aligned with the observed peak of increased Na content in the lunar exosphere.

Galaxies evolve within a web-like cosmic structure, and their properties are strongly shaped by their surrounding environments. We apply a nonparametric Bayesian two-sample test based on Pólya tree priors to galaxy data from SDSS DR7 and DESI DR1 BGS to quantify the differences between galaxies in dense and sparse cosmic environments. Compared to the Kolmogorov-Smirnov test and parametric Bayesian test, our approach does not require strong assumptions about the underlying distributional form and provides a more sensitive and robust comparison of galaxy evolution across different environments. In particular, galaxies in VoidFinder voids tend to be fainter, less massive, and more star-forming compared to wall galaxies, while such contrasts are diminished under the V^2 REVOLVER pruning. These findings underscore the importance of both the statistical framework and the void classification algorithm in interpreting environmental effects on galaxy evolution.

The radio detection of very inclined air showers offers a promising avenue for studying ultra-high-energy cosmic rays (UHECRs) and neutrinos. Accurate reconstruction methods are essential for investigating the properties of primary particles. Recently, we developed an analytical least-squares method to reconstruct the electric field using three polarization components. The reconstruction yields no bias, with a 68\% confidence interval of [-0.02, 0.02], and a standard deviation of 0.04. Using this reconstructed electric field, we perform a realistic reconstruction of the the properties of primary particles. We employ a spherical wave model combined with an angular distribution function (ADF) for arrival direction reconstruction, achieving an angular resolution of 0.04$^\circ$. This paper also presents an energy reconstruction in which we account for the effects of geosynchrotron radiation in inclined air showers, we implement an air density correction in the energy reconstruction, resulting in a 10\% resolution in energy estimation. These findings demonstrate the reliability and effectiveness of our reconstruction methodology, paving the way for future detection experiments using sparse antenna arrays.

The oscillation in primordial power spectrum (PPS), a fingerprint of not only a wide class of models of inflation but new physics, is of significant theoretical interest, and can be imprinted on the cosmic microwave background (CMB). In this work, we present constraints on periodic oscillations in the PPS using the latest ACT DR6 and SPT-3G D1 CMB data with the precise measurements at high multipoles beyond the Planck angular resolution and sensitivity. It is found that the combination of SPT and ACT with Planck CMB dataset significantly tightens the upper bound to $A_\mathrm{log,lin}\lesssim 0.029$ at 95\% C.L., showing no hint for primordial oscillations, where $A_\mathrm{log,lin}$ are the amplitudes of logarithmic and linear oscillation in the PPS, respectively. Our work presents state-of-the-art CMB constraints on primordial oscillations, highlighting the power of the ground-based CMB experiments in constraining physics beyond the simplest slow-roll models.

The solar wind, accelerated within the solar corona, sculpts the heliosphere and continuously interacts with planetary atmospheres. On Earth, high-speed solar-wind streams may lead to severe disruption of satellite operations and power grids. Accurate and reliable forecasting of the ambient solar-wind speed is therefore highly desirable. This work presents an encoder-decoder neural-network framework for simultaneously forecasting the daily averaged solar-wind speed for the subsequent four days. The encoder-decoder framework is trained with the two different modes of solar observations. The history of solar-wind observations from prior solar-rotations and EUV coronal observations up to four days prior to the current time form the input to two different encoders. The decoder is designed to output the daily averaged solar-wind speed from four days prior to the current time to four days into the future. Our model outputs the solar-wind speed with Root-Mean-Square Errors (RMSEs) of 55 km/s, 58 km/s, 58 km/s, and 58 km/s and Pearson correlations of 0.78, 0.66, 0.64 and 0.63 for one to four days in advance respectively. While the model is trained and validated on observations between 2010 - 2018, we demonstrate its robustness via application on unseen test data between 2019 - 2023, yielding RMSEs of 53 km/s and Pearson correlations 0.55 for a four-day advance prediction. Our encoder-decoder model thus produces much improved RMSE values compared to the previous works and paves the way for developing comprehensive multimodal deep learning models for operational solar wind forecasting.

In the era of third-generation (3G) gravitational-wave (GW) detectors, GW standard siren observations from binary neutron star mergers provide a powerful tool for probing the expansion history of the universe. Since sterile neutrinos can influence cosmic evolution by modifying the radiation content and suppressing structure formation, GW standard sirens offer promising prospects for constraining sterile neutrino properties within a cosmological framework. Building on this, we investigate the prospects for detecting sterile neutrinos in dynamical dark energy (DE) models using joint observations from 3G GW detectors and a future short gamma-ray burst detector, such as a THESEUS-like telescope. We consider three DE models: the $w$CDM, holographic DE (HDE), and Chevallier-Polarski-Linder (CPL) models. Our results show that the properties of DE can influence the constraints on sterile neutrino parameters. Moreover, the inclusion of GW data significantly improves constraints on both sterile neutrino parameters and other cosmological parameters across all three models, compared to the current limits derived from CMB+BAO+SN (CBS) observations. When GW data are included into the CBS dataset, a preference for $\Delta N_{\rm eff} > 0$ emerges at approximately the $1\sigma$ level in the $w$CDM and CPL models, and reaches about $3\sigma$ in the HDE model. Moreover, the upper limits on $m_{\nu,{\rm sterile}}^{\rm eff}$ are reduced by approximately 13%, 75%, and 3% in the $w$CDM, HDE, and CPL models, respectively.

Neutrons are the only neutral hadrons that remain stable over the timescale of an air-shower development. Their energy is lost only through hadronic interactions and quasi-elastic scattering, which results in their high abundance at the ground. The signals from the electromagnetic and muonic components in scintillation detectors typically span only a few microseconds. In contrast, the neutrons can cause delayed pulses in scintillation detectors up to and beyond several milliseconds after the passage of the shower front. Selection of an appropriate time window allows us to isolate and characterize the neutron component of air showers, which may provide a new, direct method to probe hadronic interactions during the shower development. We report the measurement of a neutron component at ultra-high energies using the Surface-Scintillator Detectors (SSD) from the AugerPrime upgrade of the Pierre Auger Observatory. We provide a first look at the pulse-amplitude spectrum together with our measured rate and lateral distribution of the neutron component.

Recent observations of the Small Magellanic Cloud (SMC) with Einstein Probe (EP) revealed a new transient X-ray source, most likely identified as Be/X-ray binary. To characterise the X-ray properties of EP J005146.9-730930 and in particular to look for pulsations in the X-ray flux, we triggered an XMM-Newton anticipated target of opportunity observation. To follow the flux evolution during the outburst we monitored the source for about three months with the Follow-up X-ray Telescope of EP. The XMM-Newton observation was performed on 2024 September 15 and we used the data from the European Photon Imaging Camera (EPIC) for detailed spectral and timing analyses. The EPIC X-ray spectrum is well described by an absorbed power law with photon index of 1.25 +/- 0.04 and the timing analysis revealed pulsations with 146.79 +\- 0.03 s. The source flux had decreased by a factor of about 10 since the observed maximum about one month before the XMM-Newton observation. EP J005146.9-730930 was never detected significantly during serendipitous observations before September 2024. The characteristics of the X-ray brightening suggest the source was discovered during a type II outburst reaching an X-ray peak luminosity of ~2 x 10^37 erg/s. The trend of spectral hardening towards higher luminosities observed by EP suggests that the source is accreting below the critical luminosity, yielding an estimated lower limit for the pulsar magnetic field strength of 3.3 x 10^12 G. The improved X-ray position confirms the candidate Be star OGLE J005147.58-730924.7 as optical counterpart. We conclude that EP J005146.9-730930 = SXP 146.8 is a new Be/X-ray binary pulsar in the SMC.

In the context of the ASTRI MiniArray project (9 dual-mirror air Cherenkov telescopes being installed at the Observatorio del Teide in the Canary Islands), the ASTRI- Horn prototype was previously implemented in Italy (Sicily). It was a crucial test bench for establishing observation strategies, hardware upgrades, and software solutions. Specifically, during the winter 2022/2023 observing campaign, we implemented significant enhancements in using the so-called Variance mode, an auxiliary output of the ASTRI Cherenkov camera able to take images of the night sky background in the near UV/visible band. Variance data are now processed online and on site using a dedicated pipeline and stored in tech files. This data can infer possible telescope mis-pointing, background level, number of identified stars, and point spread function. In this contribution, we briefly present these quantities and their importance together with the algorithms adopted for their calculation. They provide valuable monitoring of telescope health and sky conditions during scientific data collection, enabling the selection of optimal time sequences for Cherenkov data reduction.

Context: The post-quenching evolution process of early-type galaxies (ETGs) is still not fully understood. The amount of growth in stellar mass and size incurred after quenching is still under debate. Aims: In this work we aim to investigate the late evolution of ETGs, both observationally and theoretically, by focusing on the stellar mass density profile inside a fixed aperture, within $10$~kpc from the galaxy center. Methods: We first studied the stellar mass and mass-weighted density slope within $10 ~\rm{kpc}$, respectively $M_{*,10}$ and $\mathit{\Gamma_{*,10}}$, of a sample of early-type galaxies from the GAMA survey. We measured the \gmr~and its evolution over the redshift range $0.17\leq z \leq 0.37$. We then built a toy model for the merger evolution of galaxies, based on N-body simulations, to explore to what extent the observed growth in \gmr~is consistent with a dry-merger evolution scenario. Results: From the observations, we do not detect evidence for an evolution of the \gmr relation. We put an upper limit on $~(\mu)$ and $~(\beta)$ of the \gmr: $|\partial \mu/\partial \log (1+z)| \leq 0.13$ and $\left|\partial \beta/\partial \log (1+z)\right| \leq 1.10$, respectively. Simulations show that most mergers induce a decrease in $\mathit{\Gamma_{*,10}}$ and an increase in $M_{*,10}$, although some show a decrease in $M_{*,10}$, particularly for the most extended galaxies and smaller merger mass ratios. By combining the observations with our merger toy model, we placed an upper limit on $f_M = 11.2 \%$ in the redshift range $0.17 \leq z \leq 0.37$. Conclusions: While our measurement is limited by systematics, the application of our approach to samples with a larger redshift baseline, particularly with a time interval $\Delta t \geq 3.2~\mathrm{Gyr}$, should enable us to detect a signal and help us better understand the late growth of ETGs.

This study presents a general alternative scheme of the procedure and necessary conditions for solving the $n$-body problem. The presented solution is not a solution of the classical problem, where the initial conditions of positions and initial velocities/momenta of the bodies are known. Starting from the standard initial condition the procedure treats contributions to momentum from particular pair-wise interactions as independent variables from which the total momentum and velocity of a given mass is then reproduced. Initial values of those contributions are arbitrary as long as the resulting velocities match the initial condition. The obtained solutions take into account the gravitational interactions between each pair of bodies, as a result of which they are characterized by higher stability than the solutions of the classical problem. The presented procedure was used to calculate the positions and mutual velocities of three bodies: the Sun, the Earth and the Moon. It has also been tested for our entire planetary system (8 planets) with the Sun and the Moon. For these types of systems, the method allows obtaining solutions that are stable. The procedure was also tested on the example of the Pythagorean system of bodies.

In this work, we propose a model of warm inflation driven by axion-like particles interacting with $U(1)$ gauge fields, with implications for the early universe's thermal evolution. By extending traditional warm inflation models, we introduce a dissipation mechanism through the thermal fluctuations of electromagnetic fields, leading to a non-trivial backreaction on the inflaton's dynamics. Our results are consistent with CMB observations, even for a natural sub-Plankian axion decay constant $f<M_{\rm Pl}$. We present precise constraints on the model's free parameters, using CAMB and CosmoMC codes. These findings offer new insights into the thermal history of the universe and the nature of inflationary dynamics.

The thermodynamics of interplanetary coronal mass ejections (ICMEs) is often described using a polytropic process. Estimating the polytopic index ($\gamma$) allows us to quantify the expansion or compression of the ICME plasma arising from changes in the plasma temperature. In this study, we estimate $\gamma$ for protons inside the magnetic clouds (MCs), their associated sheaths, and ambient solar wind for a large sample of well-observed events observed by the Wind spacecraft at 1 AU. We find that $\gamma$ shows a high ($\approx 1.6$) - low ($\approx 1.05$) - high ($\approx 1.2$) behavior inside the ambient solar wind, sheath, and MCs, respectively. We also find that the proton polytropic index is independent of small-scale density fluctuations. Furthermore, our results show that the stored energy inside MC plasma is not expended in expanding its cross-section at 1 AU. The sub-adiabatic nature of MC plasma implies external heating - possibly due to thermal conduction from the corona. We find that the heating gradient per unit mass from the corona to the protons of MC at 1 AU is $\approx 0.21$ erg cm$^{-1}$ g$^{-1}$ which is in agreement with the required proton heating budget.

The Single-Mirror Small Size Cherenkov Telescope (SST-1M) was developed by a consortium of institutes in Switzerland, Poland, and the Czech Republic. The SST-1M design is based on the Davies-Cotton concept, featuring a 4-meter mirror and an innovative SiPM-based camera. It is most sensitive to gamma rays in the TeV and multi-TeV energy bands. Since 2022, two SST-1M prototypes have been commissioned at the Ondrejov Observatory in the Czech Republic, where their performance in both mono and stereo observation modes is being tested. During the commissioning phase, several galactic and extragalactic gamma-ray sources have been observed, resulting in multiple detections. In this contribution, we present preliminary results from this observation campaign.

Recent observations of cosmic rays increasingly point to the existence of nearby sources - so-called "local tevatrons", capable of accelerating particles to TeV energies. In this study, we examine the potential of a typical main-sequence star, represented by the Sun, to act as a source of TeV cosmic rays (CRs). We focus on identifying plausible mechanisms through which a quiescent star can accelerate charged particles to relativistic energies. We show that shock-drift acceleration processes operating within the chromospheres of the Sun and similar stars can accelerate particles to energies reaching the TeV scale. Additionally, we provide quantitative estimates of both the maximum achievable particle energies, spectral index of energy spectrum and the resulting cosmic-ray fluxes that such stellar environments could realistically produce. Our results indicate that ordinary stars could potentially contribute to the fine structure observed in the cosmic-ray spectrum at TeV energies and may help explain the local excess of TeV-scale electrons and positrons detected by H.E.S.S. and other observatories.

Interior to the orbits of Jupiter's iconic Galilean moons are four small satellites with individual mean radii, $R\lesssim 84$ km. Multiple lines of evidence suggest that these bodies formed at a more distant location in Jupiter's circumplanetary disk before coming to reside at their current short-period orbits. Nonetheless, how these moons dynamically evolved to such a location has yet to be explained in the emerging paradigm of Jovian satellite formation. Here, we present a quantitative model for the origin of the largest of these inner moons, Amalthea, that can be extended to its neighbor, Thebe, and to other small bodies in astrophysical disks. We propose that Amalthea's anomalous features are due to it having formed alongside the Galileans in a reservoir of satellitesimals located at a large jovian-centric distance. As the innermost Galilean, Io, migrated inward from this reservoir, it captured the satellitesimal, Amalthea, into resonance and shepherded the small body to its modern neighborhood. During migration through the disk, dissipative forcing from aerodynamic drag induces overstable librations in the Io-Amalthea resonance, such that only a narrow range of nebular parameters can accommodate the requisite long-range transport. In particular, the disk-aspect ratio, $h/r$, emerges as the key variable. Our calculations indicate that the circumjovian disk had a scale height of at least $h/r\gtrsim0.08$, implying a relatively hot, actively accreting disk during the epoch of satellite formation. These results thus shed light on the evolution of the Jovian system, along with the more general phenomenon of satellite-disk interactions.

The detection of tidal disruption events (TDEs) is one of the key science goals of large optical time-domain surveys such as the Zwicky Transient Facility (ZTF) and the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time. However, identifying TDEs in the vast alert streams produced by these surveys requires automated and reliable classification pipelines that can select promising candidates in real time. We developed a module within the Fink alert broker to identify TDEs during their rising phase. It was built to autonomously operate within the ZTF alert stream, producing a list of candidates every night and enabling spectral and multi-wavelength follow-up near peak brightness. All rising alerts are submitted to selection cuts and feature extraction using the Rainbow multi-band lightcurve fit. Best-fit values were used as input to train an XGBoost classifier with the goal of identifying TDEs. The training set was constructed using ZTF observations for objects with available classification in the Transient Name Server. Finally, candidates with high enough probability were visually inspected. The classifier achieves 76% recall, indicating strong performance in early-phase identification, despite the limited available information before peak. We show that, out of the known TDEs that pass the selection cuts, half of them are flagged as TDE before halfway in their rise, proving the feasibility of early classification. Additionally, new candidates were identified by applying the classifier on archival data, including a likely repeated TDE and some potential TDEs occurring in active galaxies. The module is implemented into the Fink alert processing framework, reporting each night a small number of candidates to dedicated communication channels through a user-friendly interface, for manual vetting and potential follow-up.

Understanding galaxy classification depends on our interpretation of their spectra. To date, the hydrogen Balmer lines remain the most consistent way to classify galaxies, but at 'intermediate' redshifts ($1.5 < z < 2.5$), galaxies are hard to parse in the BPT diagram (and its siblings) because the crucial H$\alpha$ emission line is out of range of ground-based optical spectographs. In this work, we re-explore a known diagram, which we call the OB-I diagram, that compares the equivalent width of H$\beta$ with the emission line ratio of [OIII]$\lambda$5007/H$\beta$, and breathe new life into it, as it has the potential to 'illuminate the fog' that permeates galaxy classification in the restframe optical spectra. Using data from SDSS, LEGA-C, VANDELS, JADES, 3D-HST and MOSDEF, we explore galaxy classification in the OB-I diagram at a wide range of redshifts ($0 < z < 2.7$). We find that, at $z < 0.4$, the OB-I diagram clearly separates galaxies between two distinct types, which we divide with an empirical fit: one dominated by AGN and a second made up of a mixed population of SF galaxies and AGN activity. This mixed population can be partially separated from a pure SF population, with a simple semi-empirical fit derived from a comparison with theoretical models and the BPT diagrams. At higher redshifts, we find that the majority of AGNs identified by other classification schemes are correctly recovered by the OB-I diagram, potentially making this diagram resistant to the 'cosmic shift' that plagues most optical classification schemes. Overall, the OB-I diagram, which only requires two emission lines to be implemented, is a useful tool at separating galaxies that possess a dominating AGN component in their emission from others, from the Local Universe ($z < 0.1$) to the Cosmic Noon ($z \sim 2$), without any need for significant adjustments in our empirical fit.

We introduce a new photometric mapping method for the James Webb Space Telescope (JWST) to measure the spatial distribution of carbonaceous dust, siliceous dust and water ice by using absorption features arising from the grains in the dense interstellar medium (ISM). Employing NIRCam and MIRI imaging filters, low-resolution spectroscopic data can be obtained to measure the optical depths of the 3.0-$\mu$m water ice -OH feature, the 3.4-$\mu$m aliphatic hydrocarbon -CH feature, and the 10-$\mu$m silicate -SiO feature for large fields of view. This method provides extensive statistical data of the grains across wide fields in the ISM at minimal observing cost. In this study, we present its application on observational data from the literature to validate the measured optical depths and simulations to assess the accuracy of the method under various conditions. We showed that the photometric method can be employed to obtain reasonably accurate measurements of optical depth. We demonstrate that JWST optical depth maps enable the independent exploration of abundance distributions of major grain components across a wide spatial coverage in the ISM.

GW231123 is an exceptionally massive binary black hole (BBH) merger with unusually high component spins. Such extreme properties challenge conventional stellar evolution models predicting a black hole mass gap due to pair-instability supernovae. We analyze GW231123 using population-informed priors on BH mass and spin distributions to test possible formation scenarios: first-generation stellar collapse, hierarchical (multi-generation) mergers, and primordial origin. Our analysis strongly prefers scenarios where at least one component is a higher-generation BH. Both components are favored to have high spins, which rules out scenarios in which they are both first-generation (low spin) or primordial (nearly non-spin). We conclude that GW231123 is a hierarchical merger, with components plausibly originate from the successive mergers of $\sim 6$ and $\sim 4$ first-generation BHs, respectively. This suggests that repeated mergers can be frequent and even more massive intermediate-mass black holes may be produced. Thus mechanisms that can efficiently harden the BBHs' orbits are required, e.g., gas dynamical fraction in the disks of active galactic nucleus.

In this work we study CO isotopologue emission in the largest cluster galaxy sample to date: 48 VERTICO spiral galaxies in Virgo. We show for the first time in a significant sample that the physical conditions within the molecular gas appear to change as a galaxy's ISM is affected by environmental processes. 13CO is detected across the sample, both directly and via stacking, while C18O is detected in a smaller number of systems. We use these data to study trends with global and radial galaxy properties. We show that the CO/13CO line ratio changes systematically with a variety of galaxy properties, including mean gas surface density, HI-deficiency and galaxy morphology. 13CO/C18O line ratios vary significantly, both radially and between galaxies, suggesting real variations in abundances are present. Such abundance changes may be due to star formation history differences, or speculatively even stellar initial mass function variations. We present a model where the optical depth of the molecular gas appears to change as a galaxy's ISM is affected by environmental processes. The molecular gas appears to become more transparent as the molecular medium is stripped, and then more opaque as the tightly bound remnant gas settles deep in the galaxy core. This explains the variations we see, and also helps explain similar observations in cluster early-type galaxies. Next generation simulations and dedicated observations of additional isotopologues could thus provide a powerful tool to help us understand the impact of environment on the ISM, and thus the quenching of galaxies.

We investigated three fan-shaped jets observed above sunspot light bridges or nearby sunspot regions. The study aimed to explore the dynamics and physical properties of jets' features that appear as blob-like structures at the tips of the jets, which we call `dark blobs'. A transparent region is observed beneath the dark blobs, creating a visible gap between the dark blobs and the trailing body of the jets. These phenomena were studied in chromospheric and transition region imaging and spectral high-resolution co-observations from the Visible Imaging Spectrometer of the Goode Solar Telescope at the Big Bear Solar Observatory and the Interface Region Imaging Spectrograph (IRIS), together with data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. We analyzed the jets' morphology and fine structure. We obtained the spatial scale and the dynamics of the dark blobs that are seen mostly in the wings of the H$\alpha$ line and have a cross-section of about $0.2^{\prime\prime}-0.3^{\prime\prime}$. The dark blobs and the transparent regions are seen bright (in emission) in the IRIS slit-jaw 1330 $\unicode{0x212B}$, 1400 $\unicode{0x212B}$, and AIA 304 $\unicode{0x212B}$ images. The IRIS Si IV 1394 $\unicode{0x212B}$ spectrum of the brightenings showed blue-shifted emission of about $16$ km s$^{-1}$ with non-thermal velocities of up to $40$ km s$^{-1}$. We also estimated the electron density of the blue-shifted brightenings to be $10^{12.1\pm0.2}$ cm$^{-3}$. Our findings likely suggest that we detect the observational signatures of shock waves that generate and/or contribute to the evolution of fan-shaped jets.

This work presents numerical results of a computer simulation performed with six centroiding algorithms targeting a star tracker in development at INPE, including readout noise and considering a Gaussian point spread function. Five of the tested algorithms are light-weight centroiding algorithms with low computational costs. These were compared to a shape fitting algorithm based on the lsqnonlin function available in Matlab and GNU Octave. The algorithms studied here are also applicable for astrometry and adaptive optics.

In this work we provide the missing link between two approaches aimed at characterizing the effect of long perturbation modes in Inflation. We consider the Inflationary Fossils' approach (arXiv:1203.0302 and related works) that characterizes the power-spectrum of the inflaton field in presence of other long and non dynamical fossil fields, and a technique, appeared in arXiv:2103.09244, that computes, beyond perturbation theory, the power-spectrum of a scalar field in presence of a large fluctuation of a second field. We clarify a few points on the applicability of the non-perturbative technique. We prove in five distinct cases that the non-perturbative approach, once expanded to first order in the coupling, matches the perturbative result following the Fossils' approach. We believe that this non-perturbative technique extends to all orders the Fossils' approach, resumming infinitely many diagrams of standard in-in perturbation theory.

Grain-surface chemistry plays a crucial role in the formation of molecules of astrobiological interest, including H$_{2}$S and complex organic molecules (COMs). They are commonly observed in the gas phase toward star-forming regions, but their detection in ices remains limited. Combining gas-phase observations with chemical modeling is therefore essential for advancing our understanding of their chemistry. In this paper we investigate the factors that promote or hinder molecular complexity combining gas-phase observations of CH$_{3}$OH, H$_{2}$S, OCS, N$_{2}$H$^{+}$, and C$^{18}$O with chemical modeling in two dense cores: Barnard-1b and IC348. We observed millimeter emission lines of CH$_{3}$OH, H$_{2}$S, OCS, N$_{2}$H$^{+}$, and C$^{18}$O along strips using the IRAM 30m and Yebes 40m telescopes. We used the gas-grain chemical model \texttt{Nautilus} to reproduce the observed abundance profiles adjusting parameters such as initial sulfur abundances and binding energies. H$_{2}$S, N$_{2}$H$^{+}$ and C$^{18}$O gas-phase abundances vary up to one order of magnitude towards the extinction peak. CH$_{3}$OH abundance remains quite uniform. These abundances can only be reproduced assuming a decreasing sulfur budget, which lowers H$_{2}$S and enhances CH$_{3}$OH abundances. Decreasing binding energies, which are expected in CO-rich apolar ices, are also required. The sulfur depletion required by H$_2$S is generally higher than that required by CH$_3$OH, suggesting unknown sulfur sinks. These findings highlight the intricate relationship between sulfur chemistry and COM formation, driven by the competition between sulfur and CO for hydrogen atoms. Our study emphasizes that the growth of CO ice and the progressive sequestration of hydrogen atoms by sulfur are critical in determining whether chemical complexity can develop, providing key insights into the early stages of star and planet formation.

An understanding of the energy dependence of gamma-ray sources can yield important information on the underlying emission mechanisms. However, despite the detection of energy-dependent morphologies in many TeV sources, we lack a proper quantification of such measurements. We introduce an estimation tool within the Gammapy landscape, an open-source Python package for the analysis of gamma-ray data, to quantify the energy-dependent morphology of a gamma-ray source. The proposed method for this estimation tool fits the spatial morphology in a global fit across all energy slices (null hypothesis) and compares this to separate fits for each energy slice (alternative hypothesis). These are modelled using forward-folding methods, and the significance of variability is quantified by comparing the test statistic between the two hypotheses. We present a general tool to probe changes in the spatial morphology with energy, employing a full forward folding approach with 3D likelihood. We present its usage on a real dataset from H.E.S.S., and also on a simulated dataset to quantify the significance of energy dependence for sources of different sizes. In the first example, which utilises a subset of data from HESSJ1825-137, we observe extended emission at lower energies that becomes more compact at higher energies. The tool indicates very significant variability (9.8{\sigma}) in the case of the largely extended emission. In the second example, a source with a smaller extent (~0.1°), simulated using the CTAO response, shows the tool can still provide a statistically significant variation (9.7{\sigma}), despite the small scale.

The evolution history of the Milky Way disk is imprinted in the ages, positions, and chemical compositions of individual stars. In this study, we derive the intrinsic density distribution of different stellar populations using the final data release of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. A total of 203,197 red giant branch stars are used to sort the stellar disk ($R \leq 20$ kpc) into sub-populations of metallicity ($\Delta$[M/H]$= 0.1$ dex), age ($\Delta \log(\frac{\textrm{age}}{\textrm{yr}})= 0.1$), and $\alpha$-element abundances ([$\alpha$/M]). We fit the present-day structural parameters and density distribution of each stellar sub-population after correcting for the survey selection function. The low-$\alpha$ disk is characterized by longer scale lengths and shorter scale heights, and is best fit by a broken exponential radial profile for each population. The high-$\alpha$ disk is characterized by shorter scale lengths and larger scale heights, and is generally well-approximated by a single exponential radial profile. These results are applied to produce new estimates of the integrated properties of the Milky Way from early times to the present day. We measure the total stellar mass of the disk to be $5.27^{+0.2}_{-1.5} \times 10^{10}$ M$_\odot$ and the average mass-weighted scale length is $R_{d} = 2.37 \pm 0.2$ kpc. The Milky Way's present-day color of $(g-r) = 0.72 \pm 0.02$ is consistent with the classification of a red spiral galaxy, although it has only been in the "green valley" region of the galaxy color-mass diagram for the last $\sim 3$ Gyr.

Using our rich observations within the Milky Way to better understand galaxy evolution requires understanding what the Milky Way looks like "as a galaxy" -- that is, its "true" shape and abundance profiles (unskewed by observational biases), signatures of past mergers and significant accretion events, and even its total stellar mass and integrated SED, which have historically been difficult to constrain. We present a new approach to determining the Milky Way's integrated mass and colors, using recent measurements of the intrinsic density profiles of stellar populations spanning nearly 13 Gyr in time and 1.5 dex in metallicity (representing nearly all of the Galaxy's stars). We trace the evolution of the Milky Way in various diagnostic spaces, explore the impact of specific events on the present-day Milky Way's integrated properties, and use TNG50 simulations to identify "young" Galactic analogs and their eventual fates, compared to the real Milky Way's path. From the simulation comparisons, we find strong evidence for an earlier-than-average stellar mass assembly of the MW, and that present-day MW analogs follow a similar growth history, albeit at slightly later times; we also find that analogs of the early MW are in no way guaranteed to follow the MW's subsequent path. This empirical study offers new constraints on our "Galaxy as a galaxy" -- today and across cosmic time -- and on its place in the general galactic population.

Double pulsar systems offer unrivaled advantages for the study of both astrophysics and fundamental physics. But only one has been visible: PSR J0737$-$3039; and its component pulsar B has now rotated out of sight due to the general-relativistic effect of geodetic precession. We know, though, that these precession cycles can also pivot pulsars into sight, and that this precession occurs at similar strength in PSR J1906+0746. That source is a young, unrecycled radio pulsar, orbiting a compact object with mass $\sim $1.32 M$_{\odot}$. This work presents a renewed campaign to detect radio pulsations from this companion, two decades after the previous search. Two key reasons driving this reattempt are the possibility that the companion radio beam has since precessed into our line of sight, and the improved sensitivity now offered by the FAST radio telescope. In 28 deep observations, we did not detect a credible companion pulsar signal. After comparing the possible scenarios, we conclude the companion is still most likely a pulsar that is not pointing at us. We next present estimates for the sky covered by such systems throughout their precession cycle. We find that for most system geometries, the all-time beaming fraction is unity, i.e., observers in any direction can see the system at some point. We conclude it is still likely that PSR J1906+0746 will be visible as a double pulsar in the future.

Current measurements of Baryon Acoustic Oscillations (BAO) from the Dark Energy Spectroscopic Survey (DESI DR2), when combined with data from Type Ia supernovae (SNe), challenge the observational viability of the $\Lambda$-Cold Dark Matter ($\Lambda$CDM) model, motivating combinations of independent datasets to estimate cosmological quantities. In a previous communication, we presented a cosmological independent method to constrain the baryon fraction in the IGM ($f_{\mathrm{IGM}}$), where we derived relevant expressions for the dispersion measure ($\mathrm{DM}$) in terms of luminosity distance, allowing us to estimate $f_{\mathrm{IGM}}$ combining directly measurements of 17 well-localized FRBs and 1048 SNe from the Pantheon catalog. Here we revisit this method to constrain $f_{\mathrm{IGM}}$, considering two parameterizations for the $f_{\mathrm{IGM}}$: constant and time-dependent. We expand our sample by combining 107 well-localized Fast Radio Bursts (FRBs) with BAO measurements from DESI DR2 and SNe observations from DESY5, and the Pantheon+ catalog. We find through a Bayesian model selection analysis that a conclusive answer about the evolution of $f_{\mathrm{IGM}}$ cannot be achieved from the current FRBs observational data. In particular, our results show weak evidence in favor of the constant case.

Fast Radio Bursts (FRBs) are short-duration radio transients with mysterious origins. Since its uncertainty, there are very few FRBs that are observed by different instruments, simultaneously. This study presents a detailed analysis of a burst from FRB 20190520B observed by FAST and Parkes at the same time. The spectrum of this individual burst ended at the upper limit of the FAST frequency band and was simultaneously detected by the Parkes telescope in the 1.5-1.8 GHz range. By employing spectral energy distribution (SED) and spectral sharpness methods, we confirmed the presence of narrowband radiation in FRB 20190520B, which is crucial for understanding its radiation mechanisms. Our findings support the narrowband characteristics that most repeaters exhibit. This work also highlights the necessity of continued multiband observations to explore its periodicity and frequency-dependent properties, contributing to an in-depth understanding of FRB phenomena.

We present updated results from our near-infrared long-baseline interferometry (LBI) survey to constrain the multiplicity properties of intermediate-mass A-type stars within 80 pc. Previous adaptive optics surveys of A-type stars are incomplete at separations $<$ 20au. Therefore, a LBI survey allows us to explore separations previously unexplored. Our sample consists of 54 A-type primaries with estimated masses between 1.44-2.93 M$_{\odot}$ and ages 10-790 Myr, which we observed with the MIRC-X and MYSTIC instruments at the CHARA Array. We use the open source software CANDID to detect two new companions, seven in total, and we performed a Bayesian demographic analysis to characterize the companion population. We find the separation distribution consistent with being flat, and we estimate a power-law fit to the mass ratio distribution with index -0.13$^{+0.92}_{-0.95}$ and a companion frequency of 0.25$^{+0.17}_{-0.11}$ over mass ratios 0.1-1.0 and projected separations 0.01-27.54au. We find a posterior probability of 0.53 and 0.04 that our results are consistent with extrapolations based on previous models of the solar-type and B-type companion population, respectively. Our results suggest that the close companion population to A-type stars is comparable to that of solar-types and that close companions to B-type stars are potentially more frequent which may be indicative of increased disk fragmentation for stars $\gtrsim$ 3M$_{\odot}$.

Fast Radio Bursts (FRBs) are millisecond-duration transient events that are typically observed at radio wavelengths and cosmological distances but their origin remains unclear. Furthermore, most FRB origin models are related to the processes at stellar scales, involving neutron stars, blackholes, supernovae, etc. In this paper, our purpose is to determine whether multi-structural one-off FRBs and repeaters share similarities. To achieve this, we focus on analyzing the relationship between the FRB event rate and the star formation rate, complemented by statistical testing methods. Based on the CHIME/FRB Catalog 1, we calculate the energy functions for four subsamples, including apparent non-repeating FRBs (one-offs), repeaters, multi-structural one-offs, and the joint repeaters and multi-structural events, respectively. We then derive the FRB event rates at different redshifts for all four subsamples, all of which were found to share a similar cosmological evolution trend. However, we find that the multi-structural one-offs and repeaters are distinguishable from the KS and MWW tests.

In 2029, the near-Earth asteroid (99942) Apophis approaches the Earth within six Earth radii. This opportunity is one of the rarest natural experiments that we can use to better characterize a small body through telescopic observations and space missions. Earlier geological investigations consistently suggested that major geological processes might not occur on Apophis during this closest encounter, including surface processing and interior deformation. However, minor resurfacing may occur, depending on local geological conditions. A critical finding is that the rotational evolution occurs due to the tidal effect from the Earth. The present study offers an additional perspective on the rotational evolution, which may vary due to variations in interior properties. Namely, possible deformation processes may change the spin state variation from the rigid body state, even if deformation is not measurable. The effort in this work is to explore this issue using a simplified model, motivated by earlier studies by Hirabayashi (2023) and Taylor et al. (2023). The results show that the deformation-driven spin state change may be possible, depending on Young's modulus. If this asteroid's Young's modulus is ~1 MPa or higher, the spin state only deviates a few degrees from the rigid body state over one year. However, if it is ~10 kPa or less, the spin state deviation may reach a few degrees, even a few days after the closest encounter. Both telescopic observations and space missions can provide strong insights into this phenomenon.

We investigate a standard minimally-coupled scalar-field inflationary scenario, which is based on a new potential, with suitably generalized plateau features, that leads to extra small tensor-to-scalar ratios. In particular, we consider a specific three-parameter potential, which has a flatter plateau and a steeper well compared to the Starobinsky potential in the Einstein frame. We study the inflationary realization and we show that it guarantees a prolonged period of slow-roll inflation and a successful exit. Additionally, the steeper minimum leads to significantly suppressed tensor perturbations, and thus to an extra-small tensor-to-scalar ratio $r$, and we show that we are able to obtain $r$ values less than $10^{-5}$. Moreover, we calculate the reheating temperature showing that in order to be in agreement with observations one of the potential parameters should remain within specific bounds. Finally, performing an inverse conformal transformation to the Jordan frame we show that the considered potential corresponds to higher-order corrections to Starobinsky potential in the Einstein frame, and these corrections are the reason for the improved behavior of the tensor-to-scalar ratio.

Little Red Dots (LRDs) are compact, red sources discovered by JWST at high redshift ($z \gtrsim 4$), marked by distinctive "V-shaped" spectral energy distributions (SEDs) and often interpreted as rapidly accreting AGNs. Their evolution remains unclear, as identifying counterparts at lower redshifts is challenging. We present WISEA J123635.56+621424.2 (here dubbed {\it the Saguaro}), a $z=2.0145$ galaxy in GOODS-North, as a possible analog of high-redshift LRDs and a potential missing link in their evolutionary path toward lower-redshift systems. It features a compact LRD-like nucleus surrounded by a face-on spiral host. Its connection to LRDs includes that: (1) its nuclear spectrum shows a clear "V-shaped" SED; and (2) when redshifted to $z=7$, surface brightness dimming makes the host undetectable, thus mimicking an LRD. This suggests that high-redshift LRDs may be embedded in extended hosts. To test this, we stack rest-frame UV images of 99 photometrically selected LRDs, revealing faint, diffuse emission. Stacking in redshift bins reveals mild radial growth, consistent with the expected galaxy size evolution. A simple analytic model confirms that surface brightness dimming alone can explain their compact appearance. Lastly, we show that {\it the Saguaro} is not unique by describing similar objects from the literature at $z\lesssim3.5$. Taken together, our results support a scenario in which LRDs may not be a distinct population, but could be the visible nuclei of galaxies undergoing a short-lived, AGN-dominated evolutionary phase, with their compact, red appearance driven largely by observational biases.

Baryonic feedback fundamentally alters the total matter distribution on small to intermediate cosmological scales, posing a significant challenge for contemporary cosmological analyses. Direct tracers of the baryon distribution are therefore key for unearthing cosmological information buried under astrophysical effects. Fast Radio Bursts (FRBs) have emerged as a novel and direct probe of baryons, tracing the integrated ionised electron density along the line-of-sight, quantified by the dispersion measure (DM). The scatter of the DM as a function of redshift provides insight into the lumpiness of the electron distribution and, consequently, baryonic feedback processes. Using a model calibrated to the \texttt{BAHAMAS} hydrodynamical simulation suite, we forward-model the statistical properties of the DM with redshift. Applying this model to approximately 100 localised FRBs, we constrain the governing feedback parameter, $\log T_\mathrm{AGN}$. Our findings represent the first measurement of baryonic feedback using FRBs, demonstrating a strong rejection of no-feedback scenarios at greater than $99.7\,\%$ confidence ($3\sigma$), depending on the FRB sample. We find that FRBs prefer fairly strong feedback, similar to other measurements of the baryon distribution, via the thermal and kinetic Sunyaev-Zel'dovich effect. The results are robust against sightline correlations and modelling assumptions. We emphasise the importance of accurate calibration of the host galaxy and Milky Way contributions to the DM. Furthermore, we discuss implications for future FRB surveys and necessary improvements to current models to ensure accurate fitting of upcoming data, particularly that from low-redshift FRBs.

Massive compact objects soften binaries. This process has been used for decades to constrain the population of such objects, particularly as a component of dark matter (DM). The effects of light compact objects, such as those in the unconstrained asteroid-mass range, have generally been neglected. In principle, low-energy perturbers can harden binaries instead of softening them, but the standard lore is that this effect vanishes when the perturber velocities are large compared to the binary's orbital velocity, as is typical for DM constituents. Here, we revisit the computation of the hardening rate induced by light perturbers. We show that although the perturbations average to zero over many encounters, many scenarios of interest for DM constraints are in the regime where the variance cannot be neglected. We show that a few fast-moving perturbers can leave stochastic perturbations in systems that are measured with great precision, and we use this framework to revisit the constraint potential of systems such as binary pulsars and the Solar System. This opens a new class of dynamical probes with potential applications to asteroid-mass DM candidates.

We investigate the dynamics of eccentric binary pulsars embedded in dark matter environments. While previous studies have primarily focused on circular orbits in collisionless dark matter halos, we extend this framework to eccentric systems and explore their interaction with ultralight scalar fields. Adopting a perturbative approach, we compute the modifications to the orbital period induced by dark matter-driven dynamical friction. Our results show that orbital eccentricity amplifies the imprints of non-vacuum environments on binary dynamics, underscoring the potential of such systems as sensitive probes for dark matter signatures.

Kinetic simulations excel at capturing microscale plasma physics phenomena with high accuracy, but their computational demands make them impractical for modeling large-scale space and astrophysical systems. In this context, we build a surrogate model, using Deep Operator Networks (DeepONets), based upon the Vlasov-Poisson simulation data to model the dynamical evolution of plasmas, focusing on the Landau damping process - a fundamental kinetic phenomenon in space and astrophysical plasmas. The trained DeepONets are able to capture the evolution of electric field energy in both linear and nonlinear regimes under various conditions. Extensive validation highlights DeepONets' robust performance in reproducing complex plasma behaviors with high accuracy, paving the way for large-scale modeling of space and astrophysical plasmas.

Understanding the role of multi-nucleon correlations in the structure of light nuclei is at the forefront of modern nuclear science. In this letter, we present a quantitative benchmark study of alpha-cluster correlations in the ground states of 16-O and 20-Ne. Experimental data provide direct evidence that the wave functions of the ground states of 16-O and 20-Ne are dominated by alpha-cluster correlations, in agreement with the predictions of sophisticated nuclear structure models. We also provide a new model-independent constraint for the alpha asymptotic normalization coefficient of the 16-O ground state and discuss the implications of these findings on the 12-C(alpha,gamma)16-O reaction, which is of critical importance for nuclear astrophysics.

In this work we study a scale invariant gravity theory containing two scalar fields, dust particles and a measure defined from degrees of freedom independent of the metric. The integration of the degrees of freedom that define the measure spontaneously break the scale symmetry, leaving us in the Einstein frame with an effective potential that is dependent on the density of the particles. The potential contains three flat regions, one for inflation, another for early dark energy and the third for late dark energy. At a certain point, as the matter dilutes, tunneling from the early dark energy to the late dark energy can start efficiently. This mechanism naturally alleviated the observed Hubble tension by modifying the sound horizon prior to recombination while preserving late-time cosmology. Moreover, the model predictions are consistent with observations from the reduced CMB, BAO, and local measurement of $H_0$, providing a coherent and unified description of the universe. In this context, the Bayesian analysis of these datasets confirms the viability of our scenario, with the best-fit parameters indicating an early dark energy fraction of approximately 30$\%$ at a redshift of $z'=5000$.

We present a "dictionary" to expedite the identification of potential deviations in gravitational waveforms from those predicted by General Relativity (GR) during the inspiral phase of black hole binaries. Assuming deviations from GR can be described by a local Effective Field Theory (EFT) formulated in terms of curvature operators (and possibly additional scalar fields), this dictionary characterizes how deviations scale with the masses of the binary components and identifies the leading order Post-Newtonian corrections in generic theories constructed within the EFT framework. By establishing a direct connection between observations and candidate theories beyond GR, this dictionary also aids in distinguishing genuine physical effects from systematic errors. These results can be readily incorporated into essentially all existing tests for the inspiral regime and, in particular, facilitate a more efficient combination of data from multiple events.

Accurately measuring the energy of shower particles reaching the ground remains a challenge due to the inherent limitations of typical cosmic ray experiments. In this work, we present two experimental strategies to determine the energy spectra of the electromagnetic and muonic components of extensive air showers, leveraging a single hybrid detector station within a regular cosmic ray array. This station consists of a scintillator surface detector (SSD), a water Cherenkov detector (WCD), and Resistive Plate Chambers (RPCs), with a prototype currently being tested at the Pierre Auger Observatory. The first approach exploits the different responses of each detector to the same particles traversing them, allowing, for the first time, the extraction of the high-energy tail of the electromagnetic spectrum and the low-energy tail of the muonic spectrum. The second strategy utilizes machine learning tools to reconstruct the direction of muons using the WCD+RPC system. By correlating this information with the reconstructed muon production depth, the muon kinematical delay can be analyzed, providing access to its energy spectrum.

This paper was prepared for Open-Access-only publication as a guide reporting on Education (all aspects of space science and technology), Teaching (remote sensing and GIS, satellite meteorology and global climate, satellite communication, space and atmospheric sciences, global navigation satellite systems), and Research (solar neutrino problem, formation of structure in the Universe) in astronomy (solar physics, cosmology), physics (nuclear physics, neutrino physics), and mathematics (fractional calculus, special functions of mathematical physics) exercised over 50 years (1974-2024). In this period, more than twenty workshops were held and seven regional centres for space science and technology education were established in all regions of the world: Asia and the Pacific, Latin America and the Caribbean, Africa, Western Asia, and Europe. This effort was undertaken in cooperation with ESA, NASA, JAXA, and 193 member states of the United Nations under the auspices of the UN, also supported by the Committee on Space Research (COSPAR) and the International Astronomical Union (IAU). The paper provides access to most of the documents in the six official languages of the United Nations (Arabic, Chinese, English, French, Russian, and Spanish), proceedings, and published papers and books focusing on education, teaching, and research (listed in Google Scholar and Research Gate).

Recent experimental observation suggests that neutron decay is always accompanied by emission of electron while in 1% of cases proton is not emitted. We develop a scenario kinematically compatible with experimental observation, where neutron decay results in production of two dark matter particles of about half the mass of neutron and test properties of neutron stars with admixture of such particles. Constraints on mass and coupling to vector dark boson are obtained. The structure of the compact object is modified to a dark star with a shell of nucleonic matter around the nuclear saturation density.

In the poltergeist mechanism the enhancement of induced gravitational waves (GWs) occurs due to a sudden transition from an early matter-dominated era to the radiation-dominated era. In this work, we calculate the bispectrum of induced GWs from the poltergeist mechanism by adopting the sudden transition approximation. We find that the tensor bispectrum peaks either in the equilateral or squeezed configurations, depending on scales. Such a characteristic behavior enables us to distinguish it from that from other GW generation mechanisms.

Minimal Dark Matter is among the simplest and most predictive Dark Matter frameworks, with the Majorana SU(2) 5-plet as its smallest accidentally stable real representation. We present a comprehensive reassessment of its indirect-detection signals. The $\gamma$-ray flux from both Sommerfeld-enhanced annihilations and bound-state formation is calculated, incorporating next-to-leading-order corrections and next-to-leading-log resummation of the relevant electroweak effects. In the Milky Way halo, bound-state formation dominates the flux near 100 GeV. The corresponding low-energy spectrum is used to place constraints based on Fermi-LAT observations of Galactic diffuse emission, while the high-energy part of the spectrum is employed to forecast the required observation time for several of the Milky Way's dwarf spheroidal galaxies using the Cherenkov Telescope Array Observatory (CTAO). Fermi-LAT data strongly disfavor the lower edge of the thermal mass window, even under conservative assumptions about the inner Galaxy density profile. Furthermore, several hundred hours of forthcoming CTAO observations of northern dwarfs should be sufficient to probe the central mass value.

We show that a well-studied pseudo-Hermitian field theory composed of two complex scalar fields can generate accelerated cosmological expansion through a novel mechanism. The dynamics is unique to the pseudo-Hermitian field theory, and it arises in the regime of broken antilinear symmetry, wherein a growth instability from the resulting complex eigenspectrum competes with the Hubble damping. The azimuthal components of the complex scalar fields asymptote to a constant rate of rolling at late times, reminiscent of motion around the infinite staircase of M.C. Escher's lithograph "Ascending and Descending". The resulting centripetal acceleration drives the radial components of the field away from the minimum of the potential, and the system generates a self-sustaining and constant Hubble rate at late times, even when tuning the minimum of the potential such that the classical vacuum energy is vanishing. This result evidences the potential to generate novel and physically relevant dynamics that are unique to pseudo-Hermitian field theories, and that their regimes of broken antilinear symmetry can be physically relevant in dynamical spacetimes.