Papers for Friday, Mar 28 2025

Runaway stars are characterized by higher space velocities than typical field stars. They are presumed to have been ejected from their birth places by one or more energetic mechanisms, including supernova explosions. Accurate radial velocities are essential for investigating their origin, by tracing back their Galactic orbits to look for close encounters in space and in time with neutron stars and young associations. While most studies of runaways have focused on OB stars, later-type stars have also been considered on occasion. Here we report the results of a long-term high-resolution spectroscopic monitoring program with the goal of providing accurate radial velocities for 188 runaway candidates of spectral type A and later, proposed by Tetzlaff et al. (2011). We obtained multiple measurements over a period of about 13 yr to guard against the possibility that some may be members of binary or multiple systems, adding archival observations going back another 25 yr in some cases. We report new spectroscopic orbital solutions for more than three dozen systems. Many more are also found to be binaries based on available astrometric information. A small-scale study carried out here to trace back the paths of our targets together with those of four well-studied, optically-visible neutron stars among the so-called Magnificent Seven, resulted in no credible encounters.

As the most massive nodes of the cosmic web, galaxy clusters represent the best probes of structure formation. Over time, they grow by accreting and disrupting satellite galaxies, adding those stars to the brightest cluster galaxy (BCG) and the intra-cluster light (ICL). However, the formation pathways of different galaxy clusters can vary significantly. To inform upcoming large surveys, we aim to identify observables that can distinguish galaxy cluster formation pathways. Using four different hydrodynamical simulations, Magneticum, TNG100 of IllustrisTNG, Horizon-AGN, and Hydrangea, we study how the fraction of stellar mass in the BCG and ICL ($f_{ICL+BCG}$) relates to the galaxy cluster mass assembly history. For all simulations, $f_{ICL+BCG}$ is the best tracer for the time at which the cluster has accumulated 50% of its mass ($z_{f}$), performing better than other typical dynamical tracers, such as the subhalo mass fraction, the halo mass, and the center shift. More relaxed clusters have higher $f_{ICL+BCG}$, in rare cases up to 90%, while dynamically active clusters have lower fractions, down to 20%, which we find to be independent of the exact implemented baryonic physics. We determine the average increase in $f_{ICL+BCG}$ from stripping and mergers to be between 3-4% per Gyr. $f_{ICL+BCG}$ is tightly traced by the stellar mass ratio between the BCG and both the second (M12) and fourth (M14) most massive cluster galaxy. The average galaxy cluster has assembled half of its halo mass by $z_{f}=0.67$ (about 6 Gyr ago), though individual histories vary significantly from $z_{f}=0.06$ to $z_{f}=1.77$ (0.8 to 10 Gyr ago). As all four cosmological simulations consistently find that $f_{ICL+BCG}$ is an excellent tracer of the cluster dynamical state, upcoming surveys can leverage measurements of $f_{ICL+BCG}$ to statistically quantify the assembly of the most massive structures.

Our picture of galaxy evolution currently assumes that galaxies spend their life on the star formation main sequence until they may eventually be quenched. However, recent observations show indications that the full picture might be more complicated. We reveal how the star formation rates of galaxies evolve, possible causes and imprints of different evolution scenarios on galactic features. We follow the evolution of central galaxies in the highest-resolution box of the Magneticum Pathfinder cosmological hydrodynamical simulations and classify their evolution scenarios with respect to the star formation main sequence. We find that a major fraction of the galaxies undergoes long-term cycles of quenching and rejuvenation on Gyr timescales. This expands the framework of galaxy evolution from a secular evolution to a sequence of multiple active and passive phases. Only 14% of field galaxies on the star formation main sequence at z~0 actually evolved along the scaling relation, while the bulk of star forming galaxies in the local universe have undergone cycles of quenching and rejuvenation. In this work we describe the statistics of these galaxy evolution modes and how this impacts their stellar masses, ages and metallicities today. Galaxies with rejuvenation cycles can be distinguished well from main-sequence-evolved galaxies in their features at z~0. We further explore possible explanations and find that the geometry of gas accretion at the halo outskirts shows a strong correlation with the star formation rate evolution, while the density parameter as a tracer of environment shows no significant correlation. A derivation of star formation rates from gas accretion with simple assumptions only works reasonably well in the high-redshift universe where accreted gas gets quickly converted into stars.

Blue supergiants (BSGs) mediate between the main sequence and the late stages of massive stars, which makes them valuable for assessing the physics that drives the stars across the diverse evolutionary channels. By exploring correlations between the parameters of BSGs and their variability properties, we aim to improve the constraints on the models of the evolved star structure and on the physics of the post-main-sequence evolution. We conducted a variability study of 41 BSGs with known spectroscopic parameters in the Galaxy using photometry from the Transiting Exoplanet Survey Satellite. We described the time domain of the stars by means of three statistical measures and extracted frequencies via iterative pre-whitening. Alongside, we investigated the stochastic low-frequency (SLF) variability, which manifests itself in all amplitude spectra. We report a positive correlation between the amplitude of variability and the stellar luminosity. For log(L/L$_{\odot}\lesssim 5$), stars display frequencies that match the rotational one, suggesting that variability is driven by surface spots and/or features embedded in the wind. For log(L/L$_{\odot}\gtrsim 5$), variables of the $\alpha$ Cyg class manifest themselves with their diverse and/or time-variant properties. Moreover, we report a positive correlation between the SLF variability amplitude and $T_{\rm eff}$, indicating an influential role that the stellar age plays on the emergence of the background signal beyond the main sequence. Positive, though weak, correlation is observed between the intrinsic brightness and the SLF variability amplitude, similar to the findings in the Large Magellanic Cloud, which suggests an in common excitation mechanism that depends only mildly on metallicity. Exceptionally, the $\alpha$ Cyg variables display a suppressed SLF variability that prompts to the interior changes that the evolving stars undergo.

We report on the detection of optical/near-infrared (O-IR) quasi-periodic oscillations (QPOs) from the black hole X-ray transient Swift J1727.8-1613. We obtained three X-ray and O-IR high-time-resolution observations of the source during its intermediate state (2023 September 9, 15 and 17) using NICER, HAWK-I@VLT, HIPERCAM@GTC and ULTRACAM@NTT. We clearly detected a QPO in the X-ray and O-IR bands during all three epochs. The QPO evolved, drifting from 1.4 Hz in the first epoch, up to 2.2 Hz in the second and finally reaching 4.2 Hz at the third epoch. These are among the highest O-IR QPO frequencies detected for a black hole X-ray transient. During the first two epochs, the X-ray and O-IR emission are correlated, with an optical lag (compared to the X-rays) varying from +70 ms to 0 ms. Finally, during the third epoch, we measured for the first time, a lag of the $z_s$-band respect to the $g_s$-band at the QPO frequency ($\approx$+10 ms). By estimating the variable O-IR SED we find that the emission is most likely non-thermal. Current state-of-the-art models can explain some of these properties, but neither the jet nor the hot flow model can easily explain the observed evolution of the QPOs. While this allowed us to put tight constraints on these components, more frequent coverage of the state transition with fast multi-wavelength observations is still needed to fully understand the evolution of the disc/jet properties in BH LMXBs.

Gaia recently revealed a two-armed spiral pattern in the vertical phase-space distribution of the inner Galactic disk (guiding radius $R_\textrm{g} \sim 6.2$ kpc), indicating that some non-adiabatic perturbation symmetric about the mid-plane is driving the inner disk out of equilibrium. The non-axisymmetric structures in the disk (e.g., the bar or spiral arms) have been suspected to be the major source for such a perturbation. However, both the lifetime and the period of these internal perturbations are typically longer than the period at which stars oscillate vertically, implying that the perturbation is generally adiabatic. This issue is particularly pronounced in the inner Galaxy, where the vertical oscillation period is shorter and therefore adiabatically shielded more than the outer disk. We show that two-armed phase spirals can naturally form in the inner disk if there is a vertical resonance that breaks the adiabaticity; otherwise, their formation requires a perturber with an unrealistically short lifetime. We predict analytically and confirm with simulations that a steadily rotating (non-winding) two-armed phase spiral forms near the resonance when stars are subject to both periodic perturbations (e.g., by spiral arms) and stochastic perturbations (e.g., by giant molecular clouds). Due to the presence of multiple resonances, the vertical phase-space exhibits several local phase spirals that rotate steadily at distinct frequencies, together forming a global phase spiral that evolves over time. Our results demonstrate that, contrary to earlier predictions, the formation of the two-armed phase spiral does not require transient perturbations with lifetimes shorter than the vertical oscillation period.

We present the Cambridge Exoplanet Transit Recovery Algorithm (CETRA), a fast and sensitive transit detection algorithm, optimised for GPUs. CETRA separates the task into a search for transit signals across linear time space, followed by a phase-folding of the former to enable a periodic signal search, using a physically motivated transit model to improve detection sensitivity. It outperforms traditional methods like Box Least Squares and Transit Least Squares in both sensitivity and speed. Tests on synthetic light curves demonstrate that CETRA can identify at least 20 per cent more low-SNR transits than Transit Least Squares in the same data, particularly those of long period planets. It is also shown to be up to a few orders of magnitude faster for high cadence light curves, enabling rapid large-scale searches. Through application of CETRA to Transiting Exoplanet Survey Satellite short cadence data, we recover the three planets in the HD 101581 system with improved significance. In particular, the transit signal of the previously unvalidated planet TOI-6276.03 is enhanced from ${\rm SNR}=7.9$ to ${\rm SNR}=16.0$, which means it may now meet the criteria for statistical validation. CETRA's speed and sensitivity make it well-suited for current and future exoplanet surveys, particularly in the search for Earth analogues. Our implementation of this algorithm uses NVIDIA's CUDA platform and requires an NVIDIA GPU, it is open-source and available from GitHub and PyPI.

Recent campaigns of observations have provided new measurements of the carbon isotopes in the most metal-poor stars of the Galaxy. These stars are so metal-poor that they could only have been enriched by one or few generations of massive progenitors. However, explaining the primary production of $^{13}$C and the low $^{12}$C/$^{13}$C ratio measured in these stars is challenging. Making use of the most up-to-date models for zero-metal and low-metallicity stars, we investigate the possible sources of $^{13}$C at low metallicity and verify whether massive stars could be the sole responsible for the $^{12}$C/$^{13}$C ratio observed in halo stars. We employ the stochastic model for Galactic chemical evolution GEMS to reproduce the evolution of CNO elements and $^{12}$C/$^{13}$C ratio, including the enrichment from rotating massive stars, some of which show the occurrence of H-He shell mergers. We find that stars without H-He shell mergers do not produce enough $^{13}$C to be compatible with the observations. Instead, the primary production by shell mergers and later ejection during the supernova explosion can explain 30 < $^{12}$C/$^{13}$C < 100. The observations are best reproduced assuming a large frequency of shell mergers. The $^{12}$C/$^{13}$C < 30 can only be reproduced assuming an outer layer ejection and no explosion, but requiring a larger production of $^{12}$C and $^{13}$C. Zero-metal and low-metallicity spinstars with H-He shell mergers appear as the most plausible scenario to explain the low $^{12}$C/$^{13}$C ratio in CEMP-no stars. The entire range of $^{12}$C/$^{13}$C values can be explained by assuming that some stars fully explode while others only eject their outer layers. Shell mergers should be also more frequent and productive, which is allowed by the current uncertainties in the treatment of convection in stellar modelling.

The stochastic gravitational-wave background (SGWB) generated by the inspiral and merger of binary neutron stars is traditionally modelled assuming that the inspiral is promptly followed by the collapse of the merger remnant to a rotating black hole. While this is reasonable for the most massive binaries, it is not what is expected in general, where a remnant is produced and may survive for up to hundreds of milliseconds and radiate an amount of energy that is significantly larger than that lost during the whole inspiral. To account for this additional contribution to the SGWB, we consider a waveform model that includes both the inspiral and the postmerger emission. We show for the first time that for a large set of parameterized equations of state compatible with observational constraints, there is typically five times more power spectral density in the SGWB from the postmerger emission than from the inspiral one, leading to a normalized GW energy density $\Omega_{\rm GW} \simeq 10^{-10}-10^{-9}$. This power is predominantly located in the $1-2\,{\rm kHz}$ frequency range, hence distinct from that associated with the inspiral only. We discuss the significantly enhanced detectability of the SGWB with special attention to third-generation detectors, such as the Einstein Telescope and Cosmic Explorer, and show how it depends on the signal-to-noise ratio of foreground binaries and on the metastable remnant survival time. Interestingly, even a non-detection of the high-frequency part of the SGWB could provide valuable constraints on the remnant lifetime, offering novel insights into the postmerger dynamics and into the equation of state of nuclear matter.

We present the survey design and initial results from the Parallel Ionizing Emissivity (PIE) survey. PIE is a large HST survey designed to detect Lyman continuum (LyC) emitting galaxies at 3.1$<$z$<$3.5 and stack the images of galaxies at these redshifts in order to measure average LyC escape fractions as a function of galaxy properties. PIE has imaged 37 independent fields in three filters (F336W, F625W and F814W), of which 18 are observed with a fourth band (F475W) from the accompanying PIE+ program. We use photometric colors to select candidate Lyman Break Galaxies (LBGs) at 3.1$<$z$<$3.5, which can be followed-up using ground-based spectrographs to confirm their redshifts. Unlike previous surveys, our use of many independent fields allows us to remove any biases caused by correlated absorption in the IGM. In this paper, we describe the survey design, photometric measurements, and the use of mock galaxy samples to optimize our color selection. We find that a 3-filter selection allows us to select a galaxy sample of which $\approx90\%$ are LBGs and over $30\%$ lie in the 3.1$<$z$<$3.5 range for which we can detect uncontaminated LyC emission in F336W. We also use mock IGM sightlines to measure the expected transmission of the IGM, which will allow us to determine escape fractions from our stacked galaxies. We find $\approx$1000 galaxies within our selection window, and predict that this includes $\approx$80 LyC-emitting galaxies and $\approx$350 that we can use in stacking. Finally, we present our first ground-based spectra, including a plausible LyC emitter at z=3.067.

We investigate the evolution of density perturbations in dark matter with finite number density and velocity dispersion. Using a truncated BBGKY hierarchy, we derive analytical expressions for the dark matter power spectrum during radiation and matter domination. A component of {\it warm white noise} emerges in our analysis, which arises due to the finite number density and undergoes scale-dependent evolution because of the velocity dispersion. Although free streaming erases adiabatic initial perturbations on small scales, warm white noise persists below the free-streaming length and grows during matter domination, with growth suppressed below the dark matter Jeans length. Our calculated power spectra agree with $N$-body simulations in the linear regime and accurately predict halo mass functions in the nonlinear regime. Effects of warm white noise can emerge on observable quasi-linear scales for ultralight dark matter produced after inflation with a subhorizon correlation length. Our formalism is applicable to these scenarios (with de Broglie-scale quasi-particles), to cases in which dark matter includes macroscopic structures (such as primordial black holes), and to traditional warm and cold dark matter scenarios.

Polluted white dwarfs (WDs) with small surface convection zones deposit significant concentrations of heavy elements to the underlying radiative interior, presumably driving thermohaline convection. Current models of polluted WDs frequently fail to account for this effect, although its inclusion can increase the inferred accretion rate by orders of magnitude. It has been argued that this instability cannot be treated as a continuous mixing process and thus should not be considered in these models. In this work, we study three-dimensional simulations of a thermohaline-unstable layer propagating into an underlying stable region, approximating the polluted WD scenario. We find that although thermohaline convection works to reduce driving gradients somewhat, the front continues to propagate and the system remains unstable. Importantly, the turbulent flux of metals broadly dominates over the diffusive flux in quantitative agreement with with existing mixing prescriptions implemented in some stellar evolution models (except slightly below the boundary of the propagating front, where recent prescriptions neglect overshoot-like effects). Thus, our results broadly support polluted WD models that include thermohaline mixing in their estimates of the settling rate.

Spatially resolved spectral studies of radio-AGN host galaxies have shown that these systems can impact the ionised gas on galactic scales. However, whether jet and radiation-driven feedback occurs simultaneously is still unclear. We select a large and representative sample of 806 radio-AGN from the MaNGA survey, from $L_\mathrm{1.4GHz}\approx10^{21}-10^{25}$W/Hz, and trace the warm ionised gas kinematics using the [OIII] emission line from the IFU spectra. We measure the [OIII] line width and compare it to the stellar velocity dispersion to determine the presence and location of the disturbed gas. We find most disturbed [OIII] kinematics and proportion of disturbed sources up to a radial distance of 0.25$R_{eff}$, when both radio and optical AGN are present in a source, and the radio luminosity is larger than $10^{23}$W/Hz. When either radio or optical-AGN are present, the impact on [OIII] is milder. Irrespective of the presence of an optical-AGN, we find significant differences in the feedback from high and low luminosity radio-AGN only up to a radial distance of 0.25$R_{eff}$. The presence of more kinematically disturbed warm ionised gas in the central region of radio-AGN host galaxies is related to both jets and radiation in these sources. We propose that in moderate radio luminosity AGN ($L_\mathrm{1.4GHz}\approx10^{23}-10^{25}$W/Hz) gas clouds pushed to high velocities by the jets (radiation) are driven to even higher velocities by the impact of radiation (jets) when both radio and optical-AGN are present. At lower luminosities ($L_\mathrm{1.4GHz}\approx10^{21}-10^{23}$W/Hz), the correlation between the disturbed ionised gas and enhanced radio emission could either be due to wind-driven shocks powering the radio emission, or low-power jets disturbing the gas.

1998~KY$_{26}$ is a tiny near-Earth asteroid ($H=26.1$) discovered in 1998. It has been selected as the target of the Hayabusa2 extended mission, which will rendezvous with 1998 KY$_{26}$ in 2031. However, one of the most basic physical properties, size, remains poorly constrained, posing potential challenges for spacecraft operations. We aimed at constraining the size of 1998 KY$_{26}$ by means of thermal infrared observations. We performed thermal infrared observations of 1998 KY$_{26}$ using the ESO Very Large Telescope/VISIR on three consecutive nights in May 2024. After stacking all frames, we find no apparent detection of 1998 KY$_{26}$ on the resulting images. The upper-limit flux density of 1998 KY$_{26}$ is derived as 2 mJy at 10.64 $\mu$m. From this upper-limit flux density obtained via non-detection, we conclude that the diameter of 1998 KY$_{26}$ is smaller than 17 m with thermophysical modeling. This upper limit size is smaller than the radar-derived 30 ($\pm$ 10)\,m. Our size constraint on 1998 KY$_{26}$ is essential for the operation of the Hayabusa2 spacecraft during proximity operations using remote sensing instruments as well as a possible impact experiment using the remaining projectile.

X-ray polarimetric observations from the Imaging X-ray Polarimeter Explorer (IXPE) is an excellent tool for probing the geometry and dynamics of X-ray emitting corona in active galactic nuclei (AGN). This work aims to investigate the geometry of the X-ray corona in the Seyfert 2 AGN, NGC 2110, using its first polarimetric observation with IXPE, conducted over a net exposure of 554 ks beginning on October 16, 2024. We performed a model-independent analysis of the 2-8 keV IXPE polarimetric observation to estimate the polarization properties of NGC 2110. Furthermore, we performed spectral and spectro-polarimetric analyses combining IXPE data with archival observations from NuSTAR, XMM-Newton, and Swift-XRT to derive detailed spectral and polarization properties. From the spectro-polarimetric analyses, an upper limit on the polarization degree (PD) of 7.6% (at the 99% confidence) was estimated in the 2-8 keV band. The spectro-polarimetric analysis in the 5.66-8 keV band yielded a looser upper limit of 27% at the 99 % confidence. Comparing the measured polarization properties, coronal parameters, and inclination angle of NGC 2110 with the Monte Carlo radiative transfer (MONK) simulations suggest that the current polarization measurements lack the sensitivity to place definitive constraints on the coronal geometry. The upper limits on PD, as derived from our analysis at the 99% confidence level, indicate that polarization remains undetected at a statistically significant level. Consequently, we are unable to determine whether the corona is elongated along the disk or more compact and spherical. Future observations with improved sensitivity will be crucial to breaking these degeneracies and providing deeper insight into the coronal structure of NGC 2110.

Observations and models of transiting hot Jupiter exoplanets indicate that atmospheric circulation features may cause large spatial flux contrasts across their daysides. Previous studies have mapped these spatial flux variations through inversion of secondary eclipse data. Though eclipse mapping requires high signal-to-noise data, the first successful eclipse map--made for HD 189733b using $8\mu m$ Spitzer IRAC data--showed the promise of the method. JWST eclipse observations provide the requisite data quality to access the unique advantages of eclipse mapping. Using two JWST MIRI LRS eclipse observations centered on $8\mu m$ to mimic the Spitzer bandpass used in previous studies, combined with the Spitzer IRAC $8\mu m$ eclipses and partial phase curve (necessitated to disentangle map and systematic signals), we present a 2-dimensional dayside temperature map. Our best-fit model is a 2-component 5th-degree harmonic model with an unprecedentedly constrained eastward hotspot offset of $33.0^{+0.7}_{-0.9}$ degrees. We rule out a strong hemispheric latitudinal hotspot offset, as 3+ component maps providing latitudinal degrees of freedom are strongly disfavored. As in previous studies we find some model dependence in longitudinal hotspot offset; when we explore and combine a range of proximal models to avoid an overly constrained confidence region, we find an eastward hotspot offset of $32.5^{+3.0}_{-10.6}$ degrees, indicating the presence of a strong eastward zonal jet. Our map is consistent with some previous eclipse maps of HD 189733b, though it indicates a higher longitudinal offset from others. It is largely consistent with predictions from general circulation models (GCMs) at the 115 mbar level near the $8\mu m$ photosphere.

In this study, we modify the $\Lambda$CDM model by introducing a deformed algebra within the framework of the Generalized Uncertainty Principle (GUP). We formulate the modified Raychaudhuri equation, where new terms are introduced which describe dynamical pressure components. For the quadratic GUP model, we derive the Hubble function, which leads to a time-dependent dark energy model. The free parameters are determined using late-time observational data, the Pantheon+ SNIa sample, the cosmic chronometers, and the DESI 2025 BAO data. We find that the modified model introduce only one new additional degree of freedom compared to the $\Lambda$CDM model. The GUP-Modified $\Lambda$CDM model provides a better fit to the data than the undeformed theory. Furthermore, we compare the same model with the DESI 2024 BAO data and find that the Bayesian evidence becomes stronger with the inclusion of the DESI 2025 release.

Circumbinary planets and brown dwarfs form in complex gravitational environments, offering insights into formation, orbital stability, and habitability prospects. However, they remain underrepresented, with only 60 confirmed or candidate systems known. In this work, we leverage TESS photometry to search for circumbinary companions through eclipse timing variations (ETVs), analyzing 152 detached eclipsing binaries. By modeling eclipse timings, we identify 26 systems with significant periodic signals, 14 of which have false alarm probabilities below 0.01. While no detections are confirmed, TIC 350297040 emerges as a candidate for a circumbinary brown dwarf ($0.06~M_{\odot}$) under the assumption of a $1~M_{\odot}$ binary system, though further investigation is required. Simulations using synthetic ETVs indicate a 5\% recovery rate for circumbinary brown dwarfs and 0.1\% for Jupiter-like planets, with median masses of $56.6^{+16.5}{-23.4}~M_{\rm J}$ and periods of $1404^{+1361}_{-953}$ d. Our simulations show that the smallest detectable mass is $1.6~M_{\rm J}$ at a period of 1860 d and confirm that ETV methods are effective in detecting misaligned systems. In the absence of a detection, we set an upper limit of 40\% on the occurrence rate of circumbinary brown dwarfs at the 2$\sigma$ confidence level, while a confirmed single detection would imply an occurrence rate of 13.08\%. These constraints are consistent with previous abundance estimates for circumbinary brown dwarfs ($\lesssim6.5\%$) but motivate a larger sample size. Furthermore, the very low recovery rates provide insights into the debate on first- and second-generation planet formation around post-common envelope binaries.

Understanding the formation and properties of relativistic jets from accreting compact objects has far-reaching implications in astrophysics. Transitional millisecond pulsars (tMSPs) - a class of neutron stars transitioning between radio pulsar and accretion states - offer a unique opportunity to study jet behavior within a low-level accretion regime around fast-spinning, magnetized neutron stars. We analyzed archival spectral energy distributions (SEDs) for both confirmed and candidate tMSPs from literature and various databases, aiming to identify jet spectra and determine physical conditions within these jets. For the tMSP candidate 4FGL J0427.8-6704, a high-inclination system that displays eclipses in optical, X-ray, and $\gamma$-ray wavelengths, we derived a jet break frequency at $\nu_{\rm br} \approx 10^{11}$ Hz and determined properties of the jet base using a conical jet model (opening angle of $\phi < 32^\circ$, magnetic field strength of $B_{0}\sim100$ G, and radius of $R_{0}\sim10^{10}$ cm). Observations from the Atacama Large Millimeter/submillimeter Array reveal an average flux density of 0.4 mJy, with flares reaching up to 2 mJy on short (seconds) timescales. No eclipses were detected in the millimeter light curves, suggesting the jet base is farther from the central source than in other X-ray binaries ($z_{0}>7\times10^{10}$ cm). We also investigated SEDs of other confirmed and candidate tMSPs but did not find well-defined jet spectral breaks. However, a mid-infrared flux excess in tMSP XSS J12270-4859 suggests that the compact jet emission may extend into near-infrared or optical wavelengths. These results provide new insights into jet formation in tMSPs, highlighting the need for further multi-wavelength observations to fully characterize jet behavior in similar low-accretion systems.

Recent observations from the Dark Energy Spectroscopic Instrument (DESI 2025) indicate a weakening of cosmic acceleration at low redshifts $z < 1$, with effective dark energy equation of state parameters $w_0 > -1$ and $w_a < 0$. We demonstrate that this evolution in dark energy can be explained by cosmic inhomogeneities and the Cosmic Web without modifying fundamental physics. Our model shows how the differential expansion between underdense voids and overdense walls creates an effective backreaction term that simulates evolving dark energy when interpreted within homogeneous cosmological frameworks. The inhomogeneous cosmic structure formation becomes significant $z\sim 1-2$, the increasing gravitational influence of wall regions counteracting the cosmic acceleration, producing both a weakening acceleration signal and a direction-dependent Hubble parameter consistent with local measurements. This mechanism reconciles the higher locally measured Hubble constant $H_0\approx 73~ km/s/Mpc$ with the lower value inferred from CMB observations $H_0\approx 67-69~ km/s/Mpc$ without introducing new energy components or modifying general relativity. Our model makes testable predictions regarding directional and scale-dependent variations in cosmological parameters that can be verified with next-generation surveys. This work suggests that properly accounting for cosmic structure may be essential for resolving apparent tensions in cosmological parameters.

Almost all the physics of star formation critically depends on the number density of the molecular gas. However, the methods to estimate this key property often rely on uncertain assumptions about geometry, depend on overly simplistic uniform models, or require time-expensive observations to constrain the gas temperature as well. An easy-to-use method to derive n(H2) that is valid under realistic conditions is absent, causing an asymmetry in how accurately this parameter is estimated, and how often dedicated tracers are used, compared to the gas temperature. We propose and calibrate a versatile tool based on CH3OH lines that greatly simplifies the inference of the number density. CH3OH is abundant in both cold and hot gas, and thus it can be applied to a wide variety of scales. Moreover, this tool does not need to be tailored to the specific source properties (e.g. distance, temperature, and mass). We perform RT calculations to investigate the robustness of the line ratios as density probes, also in the presence of density and temperature gradients. We find that the ratios of the (2_K-1_K) band transitions constrain the average n(H2) along the LOS within a factor of 2-3 in the range 5 x 10^4 - 3 x 10^7 cm^-3. The range can be extended down to a few times 10^3 cm^-3, when also using line ratios from the (5_K-4_K) and/or (7_K-6_K) bands. We provide practical analytic formulas and a numerical method for deriving n(H2) and its uncertainty from the line ratios. Thanks to our calibration and analytical recipes, we make the estimate of n(H2) much simpler, with an effort comparable or inferior to deriving Tex, contributing to offsetting the disparity between these two fundamental parameters of the molecular gas. Applying our method to a sub-sample of sources from the ATLASGAL TOP100 we show that the material in the clumps is being compressed, accelerating in the latest stages.

The International Pulsar Timing Array (IPTA)'s second data release (IPTA DR2) combines observations of 65 millisecond pulsars from 7 radio telescopes spanning decades, aiming to detect nanohertz gravitational waves (GWs). IPTA datasets are complex and take years to assemble, often excluding recent data crucial for low-frequency GW searches. To address this, we introduce the ``Lite'' analysis, a framework that informs the full data combination process. Using a Figure of Merit, we first select individual PTA datasets per pulsar, enabling immediate access to new data and providing an early estimate of fully combined dataset results. Applying this method to IPTA DR2, we create an uncombined dataset (DR2 Lite) and an early-combined subset (EDR2) before constructing the final Full DR2 dataset (IPTA DR2). We find that DR2 Lite can detect the common red noise process seen in Full DR2 but overestimates the amplitude as $A = 5.2^{+1.8}_{-1.7} \times 10^{-15}$ at $\gamma = 13/3$, likely due to unmodeled noise. In contrast, the combined datasets improve spectral characterization, with Full DR2 yielding an amplitude of $A = 4.0^{+1.0}_{-0.9} \times 10^{-15}$ at $\gamma = 13/3$. Furthermore, combined datasets yield higher, albeit small, detection statistics for Hellings-Downs correlations. Looking ahead, the Lite method will enable rapid synthesis of the latest PTA data, offering preliminary GW constraints before full dataset combinations are available while also motivating their construction.

To mitigate the severe information loss arising from widely adopted linear scale cuts in constraints on modified gravity parameterisations with Weak Lensing (WL) and Large-Scale Structure (LSS) data, we introduce a novel alternative method for data reduction. This Principal Component Analysis (PCA)-based framework extracts key features in the matter power spectrum arising from nonlinear effects in a set of representative gravity theories. By performing the analysis in the space of principal components, we can replace sweeping `linear-only' scale cuts with targeted cuts on the transformed data vector, ultimately reducing parameter bias and significantly tightening constraints. We forecast constraints on a minimal parameterised extension to $\Lambda$CDM which includes modifications to the growth of structure and lensing of light ($\Lambda$CDM$+\mu_0+\Sigma_0$) using mock Stage-IV data for two simulated cosmologies: the $\Lambda$CDM model and Extended Shift Symmetric (ESS) gravity. Under the assumption of a Universe defined by $\Lambda$CDM and General Relativity, our method offers constraints on $\mu_0$ a factor of 1.65 tighter than traditional linear-only scale cuts. Crucially, our approach also provides the necessary constraining power to break key degeneracies in modified gravity without relying on $f\sigma_8$ measurements, introducing a promising new tool for the analysis of present and future WL and LSS photometric surveys.

Accreting white dwarf binaries (AWDs) comprise cataclysmic variables (CVs), symbiotics, AM CVns, and other related systems that host a primary white dwarf (WD) accreting from a main sequence or evolved companion star. AWDs are a product of close binary evolution; thus, they are important for understanding the evolution and population of X-ray binaries in the Milky Way and other galaxies. AWDs are essential for studying astrophysical plasmas under different conditions along with accretion physics and processes, transient events, matter ejection and outflows, compact binary evolution, mergers, angular momentum loss mechanisms, and nuclear processes leading to explosions. AWDs are also closely related to other objects in the late stages of stellar evolution, with other accreting objects in compact binaries, and even share common phenomena with young stellar objects, active galactic nuclei, quasars, and supernova remnants. As X-ray astronomy came to a climax with the start of the Chandra and XMM-Newton missions owing to their unprecedented instrumentation, new excellent imaging capabilities, good time resolution, and X-ray grating technologies allowed immense advancement in many aspects of astronomy and astrophysics. In this review, we lay out a panorama of developments on the study of AWDs that have been accomplished and have been made possible by these two observatories; we summarize the key observational achievements and the challenges ahead.

We report the discovery of emission lines in the optical spectra of ultra-compact massive galaxies (UCMGs) from INSPIRE, including relics, which are the oldest galaxies in the Universe. Emission-lines diagnostic diagrams suggest that all these UCMGs, independently of their star formation histories, are `retired galaxies'. They are inconsistent with being star-forming but lie in the same region of shock-driven emissions or photoionisation models, incorporating the contribution from post-asymptotic giant branch (pAGB) stars. Furthermore, all but one INSPIRE objects have a high [OII]/H{\alpha} ratio, resembling what has been reported for normal-size red and dead galaxies. The remaining object (J1142+0012) is the only one to show clear evidence for strong active galactic nucleus activity from its spectrum. We also provide near-UV (far-UV) fluxes for 20 (5) INSPIRE objects that match in GALEX. Their NUV-r colours are consistent with those of galaxies lying in the UV green valley, but also with the presence of recently (<0.5 Gyr) formed stars at the sub-percent fraction level. This central recent star formation could have been ignited by gas that was originally ejected during the pAGB phases and then re-compressed and brought to the core by the ram-pressure stripping of Planetary Nebula envelopes. Once in the centre, it can be shocked and re-emit spectral lines.

It has been argued that the so-called memory-burden effect could cause black holes to become stabilized by the information that they carry, thereby suppressing the rate at which they undergo Hawking evaporation. It has furthermore been suggested that this opens a new mass window, between $10^{4}\,{\rm g} \lesssim M \lesssim 10^{10}\,{\rm g}$, over which primordial black holes could constitute the dark matter of our Universe. We show in this \textit{letter} that this is true only if the transition from the semi-classical phase of a black hole to its memory-burdened phase is practically instantaneous. If this transition is instead more continuous, Hawking evaporation will persist at relevant levels throughout the eras of Big Bang Nucleosynthesis and recombination, leading to stringent constraints which rule out the possibility that black holes lighter than $\sim 4 \times 10^{16}\,{\rm g}$ could make up all or most of the dark matter.

We discuss what we call halo or galaxy root systems, collections of particle pathlines that show the infall of matter from the initial uniform distribution into a collapsed structure. The matter clumps as it falls in, producing filamentary density enhancements analogous to tree roots and branches, blood vessels, or even human transportation infrastructure in cities and regions. This relates to the larger-scale cosmic web, but is defined locally about one of its nodes; a physical, geometric version of a merger tree. We find dark-matter-halo root systems on average to exhibit more roots and root branches for the largest cluster haloes than in small haloes. This may relate to the `cosmic-web detachment' mechanism that likely contributes to star-formation quenching in galaxy groups and clusters. We also find that high spin manifests in these root systems as curvier roots.

Four samples of open star clusters (OSCs) with average ages of 5.2, 18.6, 40, and 61 Myr have been analyzed. The selection of these OSCs was carried out from a narrow region inclined to the galactic axis y at an angle of 25$^\circ$. The spectral analysis of the vertical positions and velocities of the selected clusters showed that the Radcliffe wave is associated with OSCs no older than 30 Myr. The following estimates of the Radcliffe wave characteristics were obtained for the OSCs with an average age of 5.2 Myr: $z_{max}=117\pm12$ pc with the wavelength $\lambda=4.55\pm0.14$ kpc, the vertical velocity disturbance amplitude $W_{max}=4.86\pm0.19$ km s$^{-1}$ with the wavelength $\lambda=1.74\pm0.08$ kpc. For the OSCs with an average age of 18.6 Myr, the estimates are as follows: $z_{max} = 54\pm5$ pc and $\lambda=6.30\pm0.12$ kpc, the vertical velocity disturbance amplitude $W_{max}=7.90\pm0.16$ km s$^{-1}$ and $\lambda=0.83\pm0.11$ kpc. The radial motion of the Radcliffe wave away from the galactic center has been confirmed. The velocity of such movement is 10 pc Myr$^{-1}$. In our opinion, the spatial distribution of OSCs younger than 30 Myr does not contradict the hypothesis of the association of the Radcliffe wave with the impact of shock waves from supernova explosions that arose on an extended front comparable in scale to the entire wave, that is, about 2 kpc in size.

Local-type primordial non-gaussianity generates a distinctive term in the clustering of tracers of large-scale structure, behaving as $k^{-2}$ at small wavenumbers $k$. In order to use this signal in a sample of galaxies to measure the amplitude of primordial non-gaussianity, $f_{NL}$, we need to independently determine the degenerate bias coefficient, $b_\Phi$, which quantifies the logarithmic response of the galaxy number density to a change in amplitude of the matter clustering. We study whether $b_\Phi$ may be estimated from the observed evolution of the number density of galaxies as a function of redshift. Using cosmological N-body simulations, we find that $b_\Phi$ may be estimated reasonably well for dark matter halos across the range of redshifts and halo masses used by large-scale structure surveys aimed at measuring $f_{NL}$. This includes non-gaussian secondary bias (or assembly bias) in halo concentration, which has previously been found to be quite large in amplitude. For an observed survey of galaxies, we additionally need to consider the selection function of the sample, which can introduce redshift dependence via cuts on apparent magnitude and colour. These effects of the selection function can be mitigated by further cutting the sample using k-corrected magnitudes and colours, to retain only those galaxies that would pass the targeting criteria for all redshifts within the interval considered.

A key question in cosmology is whether massive neutrinos exist on cosmic scales. Current cosmological observations have severely compressed the viable range for neutrino masses and even prefer phenomenologically an effective negative mass. This poses a great challenge to the cosmological search for neutrinos. Based on current background and large scale structure data, taking a full redshift and/or scale tomography method, we find one beyond $5\,\sigma$, two $3\,\sigma$ and two $2\,\sigma$ evidences of massive neutrinos, spanning both high and low redshifts, as well as both small and intermediate scales. Interestingly, these five neutrino masses are well consistent within $1\,\sigma$ confidence level, indicating a possible suppression of neutrino mass during the evolution of the universe. Using cosmic microwave background observations to constrain a redshift and scale dependent neutrino mass, we make the first neutrino mass map through the cosmic history and full scales for future high precision search.

A key open question in astrophysics is how plasma is transported within strongly magnetized, rapidly rotating systems. Magnetic reconnection and flux tube interchange are possible mechanisms, with Jupiter serving as the best local analog for distant systems. However, magnetic reconnection at Jupiter remains poorly understood. A key indicator of active magnetic reconnection is the ion diffusion region, but its detection at Jupiter has remained unconfirmed. Here, we report a unique magnetic reconnection event in Jupiter's inner magnetosphere that presents the first detection of an ion diffusion region. We provide evidence that this event involves localized flux tube interchange motion driven by centrifugal forces, which occurs inside a thin current sheet formed by the collision and twisting of two distinct flux tubes. This study provides new insights into Io-genic plasma transport at Jupiter and the unique role of magnetic reconnection in rapidly rotating systems, two key unresolved questions.

We present initial simulations of the solar convection zone using a fully compressible hydrodynamic CHORUS++ code and discuss preliminary analysis. Fluid dynamics simulation of the global solar convection is a critically important tool to access the dynamics of solar cycle variations. The CHORUS++ code robustly and efficiently solves the fully compressible hydrodynamic equations using a compact local spectral method and semi-unstructured grid system. Using CHORUS++, we simulate, for the first time, the solar convection shell from 0.7 to 0.99 of the solar radius, using the actual values of the total luminosity and the sidereal rotation rate. The simulation results include the longitudinally averaged rotation rate, reasonably agreeing with the observed solar-type differential rotation. The divergence of simulated mass flux infers that the anelastic-type models are appropriate for modeling the global solar convection, except for the outermost part of the Sun, for which the temporal scale of density variation is estimated at an order of days. The spherical harmonics analysis yields that the horizontal flows are dominant in the large-scale structure, and the degree of the anisotropy of the plasma flow is rather small and constant for the small-scale structures and for a wide range of the radius.

Comets and asteroids have long captured human curiosity, and until recently, all documented examples belonged to our Solar System. That changed with the discovery of the first known interstellar object, 1I/2017 U1 ('Oumuamua), in 2017. Two years later, Gennady Borisov discovered a second interstellar object: 2I/Borisov. From its initial images, the object's diffuse appearance hinted at its cometary nature. To better understand the photometric evolution of comet 2I as it traveled through the inner Solar System, we compiled observations using medium-sized telescopes. This data is crucial for gaining insights into its size and composition, as well as how such objects, after millions of years in interstellar space, behave when exposed to the Sun's radiation. Given that 2I is the first interstellar comet ever observed, constraining its behavior is of great scientific interest. In this paper, we present photometric data gathered from observatories in Crimea and Catalonia, highlighting the importance of systematic photometric studies of interstellar objects using meter-class telescopes. Our observations showed a steady increase in the comet's brightness as it approached perihelion, likely due to the slow sublimation of ices. Over the pre-perihelion observation period, we did not detect any significant changes in magnitude. The analysis of observations reveals a steady increase in comet brightness as it approached perihelion, likely due to the sublimation of ices, with no observable outbursts during the five-month pre-perihelion period. Additionally, we discuss the challenges in ground-based observation of comets posed by light pollution today, particularly in urban areas, where visual observations are severely limited. Using sample surface brightness measurements, we demonstrate the impact of light pollution and outline the importance of systematic photometric studies for interstellar objects.

Context. The study of blue straggler stars (BSS) provides insight into the mechanisms of stellar mass exchange during binary stellar evolution and the complex gravitational interactions within dense stellar systems. In combination, they enhance our understanding of the possible life cycles of stars and the evolutionary pathways of star clusters. Aim. We study the populations of BSSs in 41 globular clusters (GCs) and 42 open clusters (OCs) adopting photometry, proper motion, and parallax from the Gaia Data Release 3 (DR3), confirming their cluster membership. We find a total of 4399 BSSs: all GCs show the presence of BSSs (3965 or ~90% of the sample), whereas only 42 out of 129 studied OCs show the presence of BSSs (434 or ~10% of the sample). Clusters younger than ~500 Myr do not host any BSSs. Methods. We derive their astrophysical parameters such as effective temperature, surface gravity, and mass based on color-temperature relations, isochrone models and Gaia DR3 spectroscopy (if available). We find values for $T_{\rm eff}=(6800 \pm 585) \ {\rm K}$ and $(7570 \pm 1400) \ {\rm K}$; and an average mass of $\langle M_{\rm BSS} \rangle = (1.02 \pm 0.1) \ {M_\odot}$ and $\langle M_{\rm BSS} \rangle = (1.75 \pm 0.45) \ {M_\odot}$ for GCs and OCs, respectively. We finally compute the difference of the BSS mass and the main sequence turn-off (MSTO) mass of its respective cluster, normalized by the MSTO mass, for every identified BSS. Results. Based on this parameter and BSSs ages derived from isochrone models, we find: i) GC BSSs that are most likely to be formed through collisions show a "boost" for ages ~ 1-2 Gyr, in agreement with ages for core-collapse events in GCs reported in previous studies; ii) a double sequence for GC BSSs that could indicate the hint of a pre/post-merger or close-binary scenario.

This study focuses on Class I, Flat Spectrum (FS), and Class II disks in the Ophiuchus molecular cloud, a nearby active star-forming region with numerous young stellar objects (YSOs), to unveil signs of substructure formation in these disks. We employ two-dimensional super-resolution imaging based on Sparse Modeling (SpM) for ALMA archival Band 6 continuum data, achieving images with spatial resolutions comparable to a few au (0".02-0".2) for 78 dust disks, all of which are spatially resolved. In our sample, we confirm that approximately 30-40% of the disks exhibit substructures, and we identify new substructures in 15 disks (4 Class I, 7 Class FS, and 4 Class II objects). Compared to the eDisk sample in terms of bolometric temperature, Tbol, our targets are in a relatively later accretion phase. By combining our targets with the eDisk sample, we confirm that substructure detection in available data is restricted to objects where Tbol exceeds 200-300 K and the dust disk radius, Rdust, is larger than ~30 au. Moreover, we find that the distribution of inclination angles for Class II disks has a deficit of high values and is not consistent with being random. Analyzing molecular line emission data around these objects will be crucial to constrain disk evolutionary stages further and understand when and how substructures form.

The Spectrum Roentgen Gamma/eROSITA first public release contains 12,247 clusters and groups. We use the offset between the Brightest Cluster Galaxy (BCG) and the X--ray peak (D$_{\rm BCG-X}$) to classify the cluster dynamical state of 3,946 galaxy clusters and groups. The X--ray peaks come from the eROSITA survey while the BCG positions come from the DECaLS DR10 optical data, which includes the DECam eROSITA Survey optical data. We aim to investigate the evolution of the merger and relaxed cluster distributions with redshift and mass, and their impact on the BCG. We model the distribution of D$_{\rm BCG-X}$ as the sum of two Rayleigh distributions representing the cluster's relaxed and disturbed populations, and explore their evolution with redshift and mass. To explore the impact of the cluster's dynamical state on the BCG luminosity, we separate the main sample according to the dynamical state. We define clusters as relaxed if D$_{\rm BCG-X}$ < 0.25$r_{500}$, disturbed if D$_{\rm BCG-X}$>0.5$r_{500}$, and as `diverse' otherwise. We find no evolution of the merging fraction in redshift and mass. We observe that the width of the relaxed distribution to increase with redshift, while the width of the two Rayleigh distributions decreases with mass. The analysis reveals that BCGs in relaxed clusters are brighter than BCGs in both the disturbed and diverse cluster population. The most significant differences are found for high mass clusters at higher redshift. The results suggest that BCGs in low-mass clusters are less centrally bound than those in high-mass systems, irrespective of dynamical state. Over time, BCGs in relaxed clusters progressively align with the potential center. This alignment correlates with their luminosity growth relative to BCGs in dynamically disturbed clusters, underscoring the critical role of the clusters dynamical state in regulating BCG evolution. [Abridged]

We report on the optical spectroscopic monitoring of the X-ray transient MAXI J0709$-$159 (identified as the Be star LY CMa) performed for about 1.5 months after the X-ray detection with MAXI. The observed spectrum showed a double-peaked H$\alpha$ line with a peak-to-peak separation of $\sim 230$ km s$^{-1}$, suggestive of the Be disk origin. We also detected a broad wing of the H$\alpha$ line with a line-of-sight velocity of $\gtrsim 900$ km s$^{-1}$, which could be explained by the accretion disk of the compact object or a stellar wind from the Be star. Initially the H$\alpha$ line showed an asymmetric profile with an enhanced blue peak, and then the blue peak decreased in $\sim$ 3 weeks to a similar strength to the red peak. We suggest that the evolution of the blue peak is associated with the X-ray activity and generated by the turbulence of the Be disk due to the passage of the compact object. We also investigated flux variation using the archival TESS data and found quasi-periodic variations with frequencies of $\sim 1$ and $\sim 2$ day$^{-1}$, which were likely caused by the pulsation of the B star. The overall variability properties on timescales of $\sim$ day were similar to those in Be X-ray binaries, rather than supergiant X-ray binaries.

Understanding the formation mechanisms of stellar-mass black holes in X-ray binaries (BHXBs) remains a fundamental challenge in astrophysics. The natal kick velocities imparted during black hole formation provide crucial constraints on these formation channels. In this work, we present a new-epoch very long baseline interferometry (VLBI) observation of the Galactic BHXB AT2019wey carried out in 2023. Combining with archival VLBI data from 2020, we successfully measure the proper motion of AT2019wey over a 3-year timescale, namely $0.78\pm0.12$~\masyr\ in right ascension and $-0.42\pm0.07$~\masyr\ in declination. Employing the measured proper motion, we estimate its peculiar velocity and the potential kick velocity (PKV), through Monte Carlo simulations incorporating uncertainties of its distance and radial velocity. The estimated PKV distributions and height above the Galactic plane suggest that AT2019wey's black hole likely formed through a supernova explosion rather than direct collapse.

This research paper aims to compare different methods for calculating the distance to the Large Magellanic Cloud (\textit{LMC}). The distance, $d_{LMC}$, is determined using stellar parallax, variable stars (RR Lyrae and Classical Cepheids), redshift, and celestial mechanics, from which the systematic and standard errors are calculated. After analyzing each method, the final distance is obtained as $d_{LMC} = 50.4802 \pm 0.0638_{\text{std}}$ Kpc, differing by $+0.5102$ Kpc from the currently most accepted value of $d_{LMC} = 49.97$ Kpc (Pietrzyński, 2014). In this paper, the value of $d_{LMC}$ was derived by combining the distances determined from RR Lyrae and Classical Cepheid variable stars, celestial mechanics and parallax.

The central $2\times0.8$ deg$^2$ region of our Galaxy contains $\sim10,000$ X-ray point sources that were detected by a series of Chandra observations over the last two decades. However, the limited bandpass of Chandra below 8 keV hampered their spectroscopic classification. In 2016, the initial NuSTAR Galactic center (GC) survey detected 77 X-ray sources above 10 keV (Hong et al. 2016). The hard X-ray detections indicate magnetic cataclysmic variables (CVs), low-mass X-ray binaries (LMXBs), high-mass X-ray binaries (HMXBs), or even pulsars. The possibility of HMXB detections is particularly interesting given the dearth of identified HMXBs in the GC. We conducted a search for bright ($K_s\lt16$ mag) near-infrared (NIR) counterparts to the hard X-ray sources $-$ utilizing their Chandra positions $-$ in order to identify HMXB candidates. We identified seven NuSTAR sources with NIR counterpart candidates whose magnitudes are consistent with HMXBs at the GC. We assessed the likelihood of random association for these seven sources and determined that two have a non-random association with a probability exceeding $99.98\%$, making them strong HMXB candidates. We analyzed broadband NuSTAR, Chandra and XMM-Newton spectral data for these two candidates, one of which was previously identified as a red supergiant. We find that the X-ray spectra are consistent with HMXBs. If confirmed through follow-up NIR spectroscopic studies, our findings will open a new window into our understanding of the intrinsic luminosity distribution of HMXBs in our Galaxy in general and the GC HMXB population in particular.

Context: Astronomy and astrophysics demand rigorous handling of uncertainties to ensure the credibility of outcomes. The growing integration of artificial intelligence offers a novel avenue to address this necessity. This convergence presents an opportunity to create advanced models capable of quantifying diverse sources of uncertainty and automating complex data relationship exploration. What: We introduce a hierarchical Bayesian architecture whose probabilistic relationships are modeled by neural networks, designed to forecast stellar attributes such as mass, radius, and age (our main target). This architecture handles both observational uncertainties stemming from measurements and epistemic uncertainties inherent in the predictive model itself. As a result, our system generates distributions that encapsulate the potential range of values for our predictions, providing a comprehensive understanding of their variability and robustness. Methods: Our focus is on dating main sequence stars using a technique known as Chemical Clocks, which serves as both our primary astronomical challenge and a model prototype. In this work, we use hierarchical architectures to account for correlations between stellar parameters and optimize information extraction from our dataset. We also employ Bayesian neural networks for their versatility and flexibility in capturing complex data relationships. Results: By integrating our machine learning algorithm into a Bayesian framework, we have successfully propagated errors consistently and managed uncertainty treatment effectively, resulting in predictions characterized by broader uncertainty margins. This approach facilitates more conservative estimates in stellar dating. Our architecture achieves age predictions with a mean absolute error of less than 1 Ga for the stars in the test dataset.

ADITYA L1, India's first dedicated mission to study Sun and its atmosphere from the Sun-Earth Lagrangian L1 location was successfully launched on September 2, 2023 with seven payloads. Visible Emission Line Coronagraph (VELC) is a major payload on ADITYA-L1. VELC has provision to carry out imaging and spectroscopic observations (the latter in three emission lines of the corona), simultaneously. Images of the solar corona in continuum at 5000Å, with the field of view (FoV) from 1.05$R_\odot$ to 3$R_\odot$ can be obtained at variable intervals depending on the data volume that can be downloaded. Spectroscopic observations of solar corona in three emission lines, namely 5303Å [Fe XIV], 7892Å [Fe XI], and 10747Å [Fe XIII] are possible simultaneously, with different exposure times and cadence. Four slits, each of width 50${\mu}$m, separated by 3.75mm helps to simultaneously obtain spectra at four positions in the solar corona at all the aforementioned lines. A Linear Scan Mechanism (LSM) makes it possible to scan the solar corona up to ${\pm}$1.5$R_\odot$ with variable step size. The instrument has the facility to carry out spectropolarimetric observations at 10747Å also in the FoV range 1.05-1.5$R_\odot$. Various components of the instrument were tested interferometrically on the optical bench before installation. The individual components were aligned and performance of the payload was checked in the laboratory using laser source and tungsten lamp. Wavelength calibration of the instrument was verified using Sun as a light source. All the detectors were calibrated for different parameters such as dark current and its variation with exposure this http URL, we discuss the various features of the VELC, alignment, calibration, performance, possible observations, initial data analysis and results of initial tests conducted in-orbit.

We present the first assessment of the perspectives to study the reheating epoch after cosmic inflation with the Ali Cosmic Microwave Background Polarization Telescope (AliCPT). AliCPT's sensitivity to the reheating temperature $T_{\text{re}}$ is primarily driven by its ability to detect primordial gravitational waves. Working in $\alpha$-attractor T-models of inflation and assuming a fiducial value of $r=0.01$, we find that AliCPT-1, in its fully loaded focal plane detector configuration and combined with Planck, can provide measurements of ${\rm log}_{10}(T_{\text{re}}[\text{GeV}]) = 12.04\pm2.55$. This translates into a bound on the inflaton coupling to other particles, requiring the related coupling constant to exceed the magnitude of the electron Yukawa coupling in the Standard Model if reheating is driven by an axion-like or Yukawa coupling. Our results are the first demonstration of AliCPT's ability to increase our knowledge about the initial temperature of the hot big bang and the microphysical parameter connecting cosmic inflation and particle physics.

We investigate a minor merger event in M31 that simultaneously forms the Andromeda Giant Southern Stream (AGSS), Eastern Extent (EE), North-Eastern Shelf (NES), and Western Shel (WS), offering a unified model for these substructures. By varying the scale radius and mass of the progenitor's dark matter halo (DMH), around the range predicted by the $\Lambda$CDM model, we successfully reproduce the spatial features of these substructures. Across the limited range of parameters considered in this study, our analysis shows that the spatial evolution of NES and WS is independent of the gravitational potential of the DMH associated with the progenitor, while a shallower potential shifts EE further north. The simulations clearly demonstrate that the progenitor with a DMH mass of $9\times10^9M_\odot$ colliding with M31 850 Myr ago could simultaneously form al thes esubstructures. The simulation results indicate that EE lies several 10kpc closer to us than the aligned Stream Cp, which is actually a metal-poor component of Stream C, whose farther distance suggests overlapping debris from distinct collision events, while both remain closely aligned in celestial coordinates. Furthermore, we predict the existence of a positive stream along the AGSS, characterized by positive line-of-sight velocities relative to M31, which complements an already observed negative stream exhibiting negative line-of-sight velocities. Finally, we propose that three objects, namely Stream B, a metal-rich component of Stream C known as Stream Cr, and EE, are components of the Andromeda Giant Southern Arc (AGSA) connected to the AGSS. Although the existence of the positive stream and a complete picture of AGSA have yet to be confirmed observationally, we anticipate that future spectroscopic observations and further advances in theoretical studies will verify their existence.

Solar flares are frequently accompanied by coronal mass ejections (CMEs) that release significant amount of energetic plasma into interplanetary space, potentially causing geomagnetic disturbances on Earth. However, many solar flares have no association with CMEs. The relationship between solar flare and CME occurrences remains unclear. Therefore, it is valuable to distinguish between active regions that potentially produce flares and CMEs and those that do not. It is believed that the eruptivity of a flare can be characterized by the properties of the active region from which it originates. In this study, we analyzed selected active regions that produced solar flares with and without CMEs during solar cycle 24. We carefully calculated the electric current neutralization of each active region by selecting relevant magnetic fluxes based on their connectivities using nonlinear force-free field models. Additionally, we analyzed their stabilities against the torus instability by estimating the proxies of critical heights of the active regions. We found that several non-eruptive active regions, which lacked clear signatures of neutral electric currents, exhibited a more apparent relationship with high critical heights of torus instability. Furthermore, we introduced a new non-dimensional parameter that incorporates current neutralization and critical height. We found that analysing ARs based on this new parameter can better discriminate eruptive and non-eruptive flare events compared to analysis that relied solely on current neutralization or torus instability. This indicates that torus instability analysis is necessary to complement electric current neutralization in characterizing the eruptivity of solar flares.

We present CO(1-0) observations of 50 star-forming galaxies at 0.01<z<0.35, for which 3.3$\,\mu$m PAH emission flux or its upper limit is available. A scaling relation between 3.3$\,\mu$m PAH luminosity and CO(1-0) luminosity is established covering ~2 orders of magnitude in total IR luminosity and CO luminosity, with a scatter of ~0.23 dex: $\mathrm{log}\,L_\mathrm{3.3}/\mathrm{L}_\odot=(1.00\pm0.07)\times\mathrm{log}\,L_\mathrm{CO(1-0)}^\prime/(\mathrm{K\,km\,s^{-1}\,pc^2})+(-1.10\pm0.70)$. The slope is near unity, allowing the use of a single value of $\langle\mathrm{log}\,(L_\mathrm{3.3}/L_\mathrm{CO(1-0)}^\prime)\rangle=-1.09\pm0.36~[\mathrm{L}_\odot/(\mathrm{K\,km\,s^{-1}\,pc^2})]$ in the conversion between 3.3$\,\mu$m PAH and CO luminosities. The variation in the $L_\mathrm{3.3}/L_\mathrm{CO}^\prime$ ratio is not dependent on the galaxy properties, including total IR luminosity, stellar mass, and SFR excess. The total gas mass, estimated using dust-to-gas ratio and dust mass, is correlated with 3.3$\,\mu$m PAH luminosity, in line with the prescription using $\alpha_\mathrm{CO}=0.8-4.5$ covering both normal star-forming galaxies and starburst galaxies. AGN-dominated galaxies tend to have a lower $L_\mathrm{3.3}/L_\mathrm{CO}^\prime$ than non-AGN galaxies, which needs to be investigated further with an increased sample size. The established $L_\mathrm{3.3}$-$L_\mathrm{CO}^\prime$ correlation is expected to be applicable to wide-field near-infrared spectrophotometric surveys that allow the detection of 3.3$\,\mu$m emission from numerous low-redshift galaxies.

Brown dwarfs at the L-T transition likely experience an inhomogeneous clearing of the clouds in their atmospheres. The resulting surface of thin and thick cloudy patches has been put forward to explain the observed variability, J-band brightening, and re-emergence of FeH absorption. We study the closest brown dwarf binary, Luhman 16A and B, in an effort to constrain their chemical and cloud compositions. As this binary consists of an L7.5 and T0.5 component, we gain insight into the atmospheric properties at the L-T transition. As part of the ESO SupJup Survey, we observed Luhman 16AB at high spectral resolution in the J-band ($1.1-1.4\ \mathrm{\mu m}$) using CRIRES$^+$. To analyse the spectra, we employ an atmospheric retrieval framework, coupling the radiative transfer code petitRADTRANS with the MultiNest sampling algorithm. For both objects, we report detections of H$_2$O, K, Na, FeH, and, for the first time in the J-band, hydrogen-fluoride (HF). The K doublet at $1250\ \mathrm{nm}$ shows asymmetric absorption in the blue line wings, which are reproduced via pressure- and temperature-dependent shifts of the line cores. We find evidence for clouds in both spectra and we place constraints on an FeH-depletion in the Luhman 16A photosphere. The inferred over-abundance of FeH for Luhman 16B opposes its predicted rainout into iron clouds. A two-column model, which emulates the patchy surface expected at the L-T transition, is weakly preferred ($\sim 1.8\sigma$) for component B but disfavoured for A ($\sim 5.5\sigma$). The results suggest a uniform surface on Luhman 16A, which is in good agreement with the reduced variability observed for this L-type component. While the presented evidence is not sufficient to draw conclusions about any inhomogeneity on Luhman 16B, future observations covering a broader wavelength range could help to test the cloud-clearing hypothesis.

One proposed black hole formation channel involves hierarchical mergers, where black holes form through repeated binary mergers. Previous studies have shown that such black holes follow a near-universal spin distribution centered around 0.7. However, gravitational-wave kicks can eject remnants from their host environments, meaning only retained black holes can participate in subsequent mergers. We calculate the spin distribution of retained black holes in typical globular clusters, accounting for remnant kick velocities. Since the kick magnitude depends on the binary's mass ratio and spin orientations, certain configurations are more likely to be retained than others. This preferentially selects certain remnant spin magnitudes, skewing the spin distribution of second-generation black holes away from the universal distribution. In low escape velocity environments, the distribution can become bimodal, as remnants with spins of 0.7 typically receive larger kicks than other configurations. Regarding higher-generation black holes, their spin distribution does not converge to a unique form, and can span a broad range of spins, $a_f \in (0.4,1)$, depending on their merger history, birth spins and the escape velocity. Additionally, we find that the presence of a small fraction of binaries with near-aligned spins can produce a second, more dominant peak, whose position depends on the birth spin magnitude. Our findings identify observable features of hierarchical merger black holes, which is essential for understanding their contribution to the gravitational-wave population. Moreover, the dependence of the spin distribution on astrophysical parameters means that precise spin measurements could provide insights into their formation environments.

We present an analysis of the emitters (\ha, \hb, and \oii) from the OTELO survey, in order to characterize the star formation properties of low-mass galaxies ($<10^9$ M$_{\odot}$ stellar masses). We calculated the specific star formation rate function, the stellar mass function, and, by integrating them, the associated densities for both quantities: the specific star formation rate density and the stellar mass density. We obtained the star formation history of our low-mass sample galaxies by fitting the spectral energy distribution of the galaxies. We also compared our results with those from the literature at different mass regimes and redshifts. The specific star formation rate density and the stellar mass density for low-mass galaxies do not depend on the redshift, contrary to the behaviour presented by the high-mass galaxies. We found that the star formation histories of low-mass galaxies are characterized by a constant star formation rate, in contrast to high-mass galaxies. We interpret these results, in the context of the downsizing effect, as representative of the faster evolution of massive galaxies compared with low-mass ones.

Void galaxies are located in the most underdense environments of the Universe, where the number density of galaxies is extremely low. They are, hence, good targets for studying the secular evolution of galaxies and the slow buildup of stellar mass through star formation. To date, very little is known about their cold gas content, both molecular (H$_2$) gas and atomic hydrogen (HI) gas. We present CO (1--0) observations of the H$_2$ gas disk in CG 910, which lies in the Boötes void, one of the largest nearby voids at relatively low redshifts (z$\sim$0.04-0.05). We used the Combined Array for Research in Research in Millimeter Astronomy (CARMA) to study the CO(1-0) distribution and gas kinematics in CG 910. We also carried out atomic hydrogen observations of the galaxy using the Robert C. Byrd Green Bank Telescope (GBT). The CARMA CO(1-0) observations reveal a molecular gas disk of mass, M(H$_{2}$) $\sim$12.0$\pm$1.1$\times$10$^{9}$M$_{\odot}$ and diameter 7 kpc. The CO velocity field shows a regularly rotating disk with a flat rotation velocity of 256 kms$^{-1}$ with no clear signatures of interaction or gas accretion. This is possibly the first CO (1-0) map of a void galaxy, and hence, important for understanding the molecular gas distribution and kinematics in void galaxies. The GBT observations reveal a HI disk of mass, M(HI) $\sim$3.1$\pm$0.8$\times$10$^{9}$M$_{\odot}$, which is relatively small compared to its stellar mass of M$_{\star}\sim$21.5$\times$10$^{9}M_{\odot}$. The total gas mass fraction, (M(H$_2$)+M(HI))/$M_{\star}$ and the atomic gas mass fraction, M(HI)/M$_{\star}$ for CG 910 are 0.70 and 0.14, respectively. We conclude that CG 910 has a regularly rotating but massive molecular gas disk. The lower atomic gas mass fraction and star formation rate indicate a longer gas depletion timescale, confirming that CG 910 is slowly evolving compared to normal disk galaxies.

We search for galaxy protoclusters at redshifts $z > 1.5$ in the first data release (Q1) of the $\textit{Euclid}$ survey. We make use of the catalogues delivered by the $\textit{Euclid}$ Science Ground Segment (SGS). After a galaxy selection on the $H_\textrm{E}$ magnitude and on the photometric redshift quality, we undertake the search using the $\texttt{DETECTIFz}$ algorithm, an overdensity finder based on Delaunay tessellation that uses photometric redshift probability distributions through Monte Carlo simulations. In this pilot study, we conduct a search in the 11 $\textit{Euclid}$ tiles that contain previously known $\textit{Planck}$ high star-forming galaxy protocluster candidates and focus on the two detections that coincide with these regions. These counterparts lie at photometric redshifts $z_\textrm{ph}=1.63^{+0.19}_{-0.23}$ and $z_\textrm{ph}=1.56^{+0.18}_{-0.21}$ and have both been confirmed by two other independent protocluster detection algorithms. We study their colours, their derived stellar masses and star-formation rates, and we estimate their halo mass lower limits. We investigate whether we are intercepting these galaxy overdensities in their `dying' phase, such that the high star-formation rates would be due to their last unsustainable starburst before transitioning to groups or clusters of galaxies. Indeed, some galaxy members are found to lie above the main sequence of galaxies (star-formation rate versus stellar mass). These overdense regions occupy a specific position in the dark matter halo mass / redshift plane where forming galaxy clusters are expected to have experienced a transition between cold flows to shock heating in the halo. Finally, we empirically update the potential for galaxy protocluster discoveries at redshift up to $z \simeq3$ (wide survey) and $z \simeq5.5$ (deep survey) with $\textit{Euclid}$ for the next data release (DR1).

We report the azimuthal distribution of the X-ray energy spectrum of non-thermal dominant supernova remnant RX J0852.0$-$4622. The X-rays from the shock region observed by the X-ray astronomy satellite Suzaku/XIS in the energy range of 2-8 keV are well described by the absorbed power-law model and can be parameterized with flux and photon index. The X-ray flux and photon index are bimodally distributed in relation to the azimuthal angle. To understand its origin, we examined three possible causes: azimuthal variation by (1) the galactic magnetic field, (2) cloud density, and (3) shock velocity. From the polarization observations of stars near the SNR, we find that the Galactic magnetic field around the SNR is not aligned. This result leads us to conclude that the azimuthal variation of the X-ray spectrum is most likely not caused by the Galactic magnetic field. The X-ray fluxes are positively correlated with the cloud density with a significance of $\sim 5\sigma$, and the azimuthal distributions of these physical quantities are particularly pronounced in the northern part of the SNR. In addition, the X-ray fluxes on the southern part of the SNR are positively correlated with the shock velocity. This phenomenon can be qualitatively explained by the increase in roll-off energy due to the amplification of the magnetic field by (A) the interaction between the shock and dense clouds in the north and (B) the fast shock velocity in the south of the SNR. Since the shock velocity is likely related to the cloud density interacting with the shock, we conclude that the azimuthal variation of cloud density most likely causes the azimuthal variations of the X-ray flux and photon index.

We report the Imaging X-ray Polarimetry Explorer (IXPE) polarimetric and simultaneous multiwavelength observations of the high-energy-peaked BL Lacertae (HBL) object 1ES 1959+650, performed in 2022 October and 2023 August. In 2022 October IXPE measured an average polarization degree $\Pi_{\rm X}=9.4\;\!\%\pm 1.6\;\!\%$ and an electric-vector position angle $\psi_{\rm X}=53^{\circ}\pm 5^{\circ}$. The polarized X-ray emission can be decomposed into a constant component, plus a rotating component, with rotation velocity $\omega_{\rm EVPA}=(-117\;\!\pm\;\!12)$ ${\rm deg}\;\!{\rm d}^{-1}$. In 2023 August, during a period of pronounced activity of the source, IXPE measured an average $\Pi_{\rm X}=12.4\;\!\%\pm0.7\;\!\%$ and $\psi_X=20^{\circ}\pm2^{\circ}$, with evidence ($\sim$0.4$\;\!\%$ chance probability) for a rapidly rotating component with $\omega_{\rm EVPA}=(1864\;\!\pm\;\!34)$ ${\rm deg}\;\!{\rm d}^{-1}$. These findings suggest the presence of a helical magnetic field in the jet of 1ES 1959+650 or stochastic processes governing the field in turbulent plasma. Our multiwavelength campaigns from radio to X-ray reveal variability in both polarization and flux from optical to X-rays. We interpret the results in terms of a relatively slowly varying component dominating the radio and optical emission, while rapidly variable polarized components dominate the X-ray and provide minor contribution at optical wavelengths. The radio and optical data indicate that on parsec scales the magnetic field is primarily orthogonal to the jet direction. On the contrary, X-ray measurements show a magnetic field almost aligned with the parsec jet direction. Confronting with other IXPE observations, we guess that the magnetic field of HBLs on sub-pc scale should be rather unstable, often changing its direction with respect to the VLBA jet.

Solar flares result from the rapid conversion of stored magnetic energy within the Sun's corona. These energy releases are associated with coronal magnetic loops, which are rooted in dense photospheric plasma and are passively transported by surface advection. Their emissions cover a wide range of wavelengths, with soft X-rays being the primary diagnostic for the past fifty years. Despite the efforts of multiple authors, we are still far from a complete theory, capable of explaining the observed statistical and individual properties of flares. Here, we exploit the availability of stable and long-term soft x-ray measurements from NASA's GOES mission to build a new solar flare catalogue, with a novel approach to linking sympathetic events. Furthermore, for the most energetic events since 2010, we have also provided a method to identify the origin of the observed flare and eventual link to the photospheric active region by exploiting the array of instruments onboard NASA's Solar Dynamic Observatory. Our catalogue provides a robust resource for studying space weather events and training machine learning models to develop a reliable early warning system for the onset of eruptive events in the solar atmosphere.

From a carefully selected sample of $52\,089$ galaxies and $10\,429$ groups, we investigate the variation of the low-redshift galaxy stellar mass function (GSMF) in the equatorial Galaxy And Mass Assembly (GAMA) dataset as a function of four different environmental properties. We find that: (i) The GSMF is not strongly affected by distance to the nearest filament but rather by group membership. (ii) More massive halos tend to host more massive galaxies and exhibit a steeper decline with stellar mass in the number of intermediate-mass galaxies. This result is robust against the choice of dynamical and luminosity-based group halo mass estimates. (iii) The GSMF of group galaxies does not depend on the position within a filament, but for groups outside of filaments, the characteristic mass of the GSMF is lower. Finally, our global GSMF is well described by a double Schechter function with the following parameters: $\log [M^{\star} / (M_{\odot} \, h_{70}^{-2})] = 10.76 \pm 0.01$, $\Phi_1^{\star} = (3.75 \pm 0.09) \times 10^{-3}$ Mpc$^{-3}$ $h_{70}^3$, $\alpha_{1} = -0.86 \pm 0.03$, $\Phi_2^{\star} = (0.13 \pm 0.05) \times 10^{-3}$ Mpc$^{-3}$ $h_{70}^3$, and $\alpha_{2} = -1.71 \pm 0.06$. This result is consistent with previous GAMA studies in terms of $M^{\star}$, although we find lower values for both $\alpha_{1}$ and $\alpha_{2}$.

We provide an overview of the Jiutian simulations, a hybrid simulation suite for the China Space Survey Telescope (CSST) extragalactic surveys. It consists of four complementary modules: the primary runs with high resolutions under the fiducial concordance cosmology, the emulator runs exploring the parameter uncertainties around the fiducial cosmology, the reconstruction runs intended for recovering the observed Universe site by site, and the extension runs employing extended cosmologies beyond the standard model. For the primary runs, two independent pipelines are adopted to construct subhaloes and merger trees. On top of them, four sets of mock galaxy light-cone catalogs are produced from semi-analytical models and subhalo abundance matching, providing a variety of observational properties including galaxy SED, emission lines, lensing distortions, and mock images. The 129 emulator runs are used to train the CSST emulator, achieving one percent accuracy in predicting a variety of cosmological statistics over $k\leq 10 h{\rm Mpc}^{-1}$ and $z\leq 2$. The reconstruction runs employ a number of subgrid baryonic models to predict the evolution and galaxy population of certain regions in the real Universe with constrained initial conditions, enabling controlled investigation of galaxy formation on top of structure formation. The extension runs cover models with warm dark matter, $f(R)$ gravity, interacting dark energy, and nonzero neutrino masses, revealing differences in the cosmic structure under alternative cosmological models. We introduce the specifications for each run, the data products derived from them, the corresponding pipeline developments, and present some main tests. Using the primary runs, we also show that the subhalo peak mass functions of different levels are approximately universal. These simulations form a comprehensive and open library for the CSST surveys.

We constrain AvERA cosmologies in comparison with the flat $\Lambda$CDM model using cosmic chronometer (CC) data and the Pantheon+ sample of type Ia supernovae (SNe Ia). The analysis includes CC fits performed with the \texttt{emcee} sampler and supernova fits based on a custom Markov Chain Monte Carlo implementation. For model comparison, we apply Anderson-Darling tests on normalized residuals to assess consistency with a standard normal distribution. Best-fit parameters are derived within the redshift ranges $z \leq 2$ for CCs and $z \leq 2.3$ for SNe. The best-fit values of the Hubble constant are ${H_0=68.28_{-3.24}^{+3.23}~\mathrm{km~s^{-1}~Mpc^{-1}}}$ from the CC analysis and ${H_0=71.99_{-1.03}^{+1.05}~\mathrm{km~s^{-1}~Mpc^{-1}}}$ from the SN analysis, for the AvERA cosmology. These results are consistent within $1\sigma$ with the corresponding AvERA simulation value of $H(z=0)$. Both the CC and SN datasets substantially favor AvERA cosmologies over the flat $\Lambda$CDM model. We have identified signs of overfitting in both models, which suggests the possibility of overestimating the uncertainties in the Pantheon+ covariance matrix.

CONTEXT: Dense cores are thought to be isolated from the surrounding cloud. However, observations of streamers and subsonic material outside core boundaries challenges this idea. AIMS: In this study, we aim to probe the extended subsonic region observed around the pre-stellar core H-MM1 in L1688 using multi-component kinematical analysis of very high-sensitivity NH3 data. METHODS: We used observations of NH3 (1,1) and (2,2) using GBT. We then fitted up to two components towards the core and its surrounding molecular cloud. RESULTS: We detect an extended region of subsonic turbulence in addition to the ambient cloud, which show supersonic turbulence. This extended subsonic region is approximately 12 times the size of and more than two times as massive as the previously detected subsonic material. The subsonic region is further split into two well-separated, velocity-coherent components, one of which is kinematically and spatially connected to the dense core. The two subsonic components are red- and blue-shifted with respected to the cloud component. We also detect a flow of material onto the dense core from the extended subsonic region via a streamer of length ~0.15 pc (~30000 au). CONCLUSIONS: We find that the extended subsonic component kinematically associated with the dense core contains 27% more mass than the core. This material could be further accreted by the core. The other subsonic component contains a mass similar to that of the core mass, and could be tracing material in the early stage of core formation. The H-MM1 streamer is kinematically similar to the ones observed towards protostellar systems, but is the first instance of such an accretion feature onto a core in its pre-stellar phase. This accretion of chemically fresh material by the pre-stellar core challenges our current understanding of a core evolving with a mass unchanged since the time of its formation.

Pulsars are one of the possible final stages in the evolution of massive stars. If a supernova explosion is anisotropic, it can give the pulsar a powerful kick, propelling it to supersonic speeds. The resulting pulsar wind nebula is significantly reshaped by its interaction with the surrounding medium as the pulsar moves through it. First, the pulsar crosses the supernova remnant, followed by the different layers of circumstellar medium formed during different stages of the progenitor star s evolution. We aim to investigate how the evolutionary history of massive stars shapes the bow shock nebulae of runaway kicked pulsars, and how these influences in turn affect the dynamics and non-thermal radio emission of the entire pulsar remnant. We perform three-dimensional magnetohydrodynamic simulations using the PLUTO code to model the pulsar wind nebula generated by a runaway pulsar in the supernova remnant of a red supergiant progenitor, and derive its non-thermal radio emission. The supernova remnant and the pre-supernova circumstellar medium of the progenitor strongly confine and reshape the pulsar wind nebula of the runaway pulsar, bending its two side jets inwards and giving the nebula an arched shape for an observer perpendicular to the jets and the propagation direction, as observed around PSR J1509 5850 and Gemina. We perform the first classical 3D model of a pulsar moving inward through its supernova ejecta and circumstellar medium, inducing a bending of its polar jet that turns into characteristic radio synchrotron signature. The circumstellar medium of young runaway pulsars has a significant influence on the morphology and emission of pulsar wind nebulae, whose comprehension requires a detailed understanding of the evolutionary history of the progenitor star.

The rapid evolution of the cosmological neutral hydrogen (HI) distribution during the EoR is imprinted along the line of sight (LoS) in the redshifted 21-cm signal due to the light cone (LC) effect. The LC EoR 21-cm signal ceases to be ergodic along the LoS, and the Fourier transform-based three-dimensional power spectrum (PS) fails to capture the full two-point statistics. Several earlier studies have used the multi-frequency angular power spectrum (MAPS) $\mathcal{C}_\ell(\nu_1,\nu_2)$ to overcome this limitation. However, we do not have a simple interpretation of $\mathcal{C}_\ell(\nu_1,\nu_2)$ in terms of comoving length scale, and the data volume is large. Here we introduce the evolving power spectrum (ePS) to quantify the two-point statistics of the LC EoR 21-cm signal. This has a simple interpretation in terms of redshift evolution and comoving length scales, and the binned ePS reduces the data volume by several orders of magnitude compared to MAPS. Considering simulations, we study the first three even angular multipoles of ePS to quantify the LoS anisotropy of the signal. We find that as reionization progresses, at large $k$ ($\ge 0.6 \, {\rm Mpc}^{-1}$), $P_{e\,0}(k,z)$ the monopole moment decreases as $\propto \bar{x}_{\rm H I}$ the mean neutral HI fraction, which, in principle, can be used to observationally determine the reionization history. Furthermore, $P_{e\,2}(k,z)$ the quadrupole moment is negative at small $k$ and positive at large $k$. We propose the binned ePS, which captures the entire information contained in MAPS, to quantify the full two-point statistics of the LC EoR 21-cm signal.

Gravitational wave (GW) observations probe both a diffuse, stochastic gravitational wave background (SGWB) as well as individual cataclysmic events such as the merger of two compact objects. The detection and description of the gravitational-wave background requires somewhat different techniques than required for individual events. In this paper, we probe the sensitivity of present and future GW telescopes to different background sources, including both those expected from unresolved compact binaries in both their quasi-Newtonian quiescent and their eventual mergers, as well as more speculative cosmological sources such as inflation, cosmic strings, and phase transitions, over regions in which those sources can be described by a single power aw. We develop a Fisher matrix formalism to forecast coming sensitivities of single and multiple experiments, and novel visualizations taking into account the increase in sensitivity to a background over time.

Filaments are ubiquitous in astronomical data sets. Be it in particle simulations or observations, filaments are always tracers of a perturbation in the equilibrium of the studied system and hold essential information on its history and future evolution. However, the recovery of such structures is often complicated by the presence of a large amount of background and transverse noise in the observation space. While the former is generally detrimental to the analysis, the latter can be attributed to measurement errors and it can hold essential information about the structure. To further complicate the scenario, 1D manifolds (filaments) are generally non-linear and their geometry difficult to extract and model. In order to study hidden manifolds within the dataset, particular care has to be devoted to background noise removal and transverse noise modelling, while still maintaining accuracy in the recovery of their geometrical structure. We propose 1-DREAM: a toolbox composed of five main Machine Learning methodologies whose aim is to facilitate manifold extraction in such cases. Each methodology has been designed to address issues when dealing with complicated low-dimensional structures convoluted with noise and it has been extensively tested in previously published works. In this work all methodologies are presented in detail, joint within a cohesive framework and demonstrated for three interesting astronomical cases: a simulated jellyfish galaxy, a filament extracted from a simulated cosmic web and the stellar stream of Omega-Centauri as observed with the GAIA DR2. Two newly developed visualization techniques are also proposed, that take full advantage of the results obtained with 1-DREAM. The code is made publicly available to benefit the community. The controlled experiments on a purposefully built data set prove the accuracy of the pipeline in recovering the hidden structures.

Recent findings from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) favor a dynamical dark energy characterized by a phantom crossing feature. This result also implies a lower value of the Hubble constant, thereby intensifying the so-called Hubble tension. To alleviate the Hubble tension, we consider the early dark energy and explore its impact on the evidence for dynamical dark energy including the Hubble constant calibrated by the SH0ES collaboration. We find that incorporating SH0ES prior with CMB, DESI DR2 BAO and Pantheon Plus/Union3/DESY5 data reduces the preference to dynamical dark energy to $1.8\sigma/1.8\sigma/2.9\sigma$ level, respectively. Our results suggest a potential tension between the Hubble constant $H_0$ of the SH0ES measurement and the phantom-to-quintessence transition in dark energy favored by DESI DR2 BAO data.

Using public data collected by the Fermi Large Area Telescope (LAT) over 16 years, and the 1523 days of survey data (3HWC) from the High Altitude Water Cherenkov (HAWC) observatory, we searched for possible GeV-TeV connections in globular clusters (GCs). In addition to the confirmed $\gamma-$ray GCs in the 4FGL catalog, we report a GeV detection at the position of UKS 1 with a post-trial probability of $\sim8\times10^{-5}$ of it being a fluctuation. Its spectrum within this energy range is well described by a power-law model with $\Gamma\simeq2.3\pm0.5$. Furthermore, this GeV feature appears to extend southeast in a direction towards the Galactic plane. From the 3HWC survey data, we have also identified a TeV feature in the direction of UKS 1. It is well-resolved from any known Very High Energy (VHE) source. The post-trial probability that this feature is a fluctuation is $\sim3\times10^{-4}$. If confirmed, this would be the second detection of a TeV feature in the proximity of a GC. While the GeV emission mostly coincides with the center of UKS 1, the TeV peak is displaced from the cluster center by several tidal radii in the trailing direction of the GC's proper motion. Given the supersonic speed of UKS 1 at $\sim270$ km s$^{-1}$, our findings are consistent with a scenario where the VHE $\gamma-$rays are produced by inverse Compton scattering between relativistic particles and ambient soft photon fields during the course of their propagation away from the head of the bow shock.

Possible interaction between dark energy and dark matter has previously shown promise in alleviating the clustering tension, without exacerbating the Hubble tension, when BAO data from SDSS DR16 is combined with CMB and SNIa datasets. With the recent DESI BAO DR2, there is now a compelling need to re-evaluate this scenario. We combine DESI DR2 with Planck 2018 and Pantheon+ SNIa datasets to constrain interacting dark matter dark energy models, accounting for interaction effects in both the background and perturbation sectors. Our results exhibit similar trends to those observed with SDSS, albeit with improved precision, reinforcing the consistency between the two BAO datasets. In addition to offering a resolution to the $S_8$ tension, in the phantom-limit, the dark energy equation of state exhibits an early-phantom behaviour, aligning with DESI DR2 findings, before transitioning to $w\sim-1$ at lower redshifts, regardless of the DE parametrization. However, the statistical significance of excluding $w=-1$ is reduced compared to their non-interacting counterparts.

In the current era of JWST, we continue to uncover a wealth of information about the Universe deep into the Epoch of Reionization. In this work, we run a suite of simulations using the code 21cmSPACE, to explore the astrophysical properties of galaxies in the early Universe, and their impact on high-redshift observables. We use multi-wavelength observational data including the global 21-cm signal and power spectrum limits from SARAS~3 and HERA respectively, present-day diffuse X-ray and radio backgrounds, and UV luminosity functions (UVLFs) from HST and JWST in the range $z=6-14.5$ to derive our constraints. We constrain a flexible model of halo-mass and redshift dependent star-formation efficiency (SFE), defined as the gas fraction converted into stars, and find that it is best described by little to no redshift evolution at $z\approx6-10$ and rapid evolution at $z\approx10-15$. We derive Bayesian functional posterior distributions for the SFE across this redshift range, inferring that a halo of mass $M_h=10^{10}\text{M}_\odot$ has an efficiency of $2-3\%$ at $z\lesssim10$, $12\%$ at $z=12$ and $26\%$ at $z=15$. We also find, through synergy between SARAS~3 and UVLFs, that the minimum circular velocity for star-formation in halos is $V_c = 16.9^{+25.7}_{-9.5}\text{km s}^{-1}$ or equivalently $\log_{10}(M_\text{crit}/\text{M}_\odot) = 8.29^{+1.21}_{-1.08}$ at $z=6$. Alongside these star-formation constraints, we find the X-ray and radio efficiencies of early galaxies to be $f_X = 0.5^{+6.3}_{-0.3}$ and $f_r \lesssim 11.7$ respectively, improving upon existing works that do not use UVLF data. Our results demonstrate the critical role of UVLFs in constraining the early Universe, and its synergies with 21-cm observations, alongside other multi-wavelength observational datasets.

Atmospheric retrievals are essential tools for interpreting exoplanet transmission and eclipse spectra, enabling quantitative constraints on the chemical composition, aerosol properties, and thermal structure of planetary atmospheres. The James Webb Space Telescope (JWST) offers unprecedented spectral precision, resolution, and wavelength coverage, unlocking transformative insights into the formation, evolution, climate, and potential habitability of planetary systems. However, this opportunity is accompanied by challenges: modeling assumptions and unaccounted-for noise or signal sources can bias retrieval outcomes and their interpretation. To address these limitations, we introduce a Gaussian Process (GP)-aided atmospheric retrieval framework that flexibly accounts for unmodeled features in exoplanet spectra, whether global or localized. We validate this method on synthetic JWST observations and show that GP-aided retrievals reduce bias in inferred abundances and better capture model-data mismatches than traditional approaches. We also introduce the concept of mean squared error to quantify the trade-off between bias and variance, arguing that this metric more accurately reflects retrieval performance than bias alone. We then reanalyze the NIRISS/SOSS JWST transmission spectrum of WASP-96 b, finding that GP-aided retrievals yield broader constraints on CO$_2$ and H$_2$O, alleviating tension between previous retrieval results and equilibrium predictions. Our GP framework provides precise and accurate constraints while highlighting regions where models fail to explain the data. As JWST matures and future facilities come online, a deeper understanding of the limitations of both data and models will be essential, and GP-enabled retrievals like the one presented here offer a principled path forward.

The Flashlights program with the Hubble Space Telescope imaged the six Hubble Frontier Fields galaxy clusters in two epochs and detected twenty transients. These are primarily expected to be caustic-crossing events (CCEs) where bright stars in distant lensed galaxies, typically at redshift $z\approx1$--3, get temporarily magnified close to cluster caustics. Since CCEs are generally biased toward more massive and luminous stars, they offer a unique route for probing the high end of the stellar mass function. We take advantage of the Flashlights event statistics to place preliminary constraints on the stellar initial mass function (IMF) around cosmic noon. The photometry (along with spectral information) of lensed arcs is used to infer their various stellar properties, and stellar synthesis models are used to evolve a recent stellar population in them. We estimate the microlens surface density near each arc and, together with existing lens models and simple formalism for CCEs, calculate the expected rate for a given IMF. We find that, on average, a Salpeter-like IMF ($\alpha=2.35$) underpredicts the number of observed CCEs by a factor of ${\sim}0.7$, and a top-heavy IMF ($\alpha=1.00$) overpredicts by a factor of ${\sim}1.7$, suggesting that the average IMF slope may lie somewhere in between. However, given the large uncertainties associated with estimating the stellar populations, these results are strongly model-dependent. Nevertheless, we introduce a useful framework for constraining the IMF using CCEs. Observations with JWST are already yielding many more CCEs and will soon enable more stringent constraints on the IMF at a range of redshifts.

We perform a high resolution zoom-in simulation of star cluster assembly including the merger of two sub-clusters with initial conditions taken from previous large scale giant molecular cloud (GMC) simulations. We couple hydrodynamics to N-body dynamics to simulate the individual stars themselves, and the gas-rich environment in which they evolve. We include prescriptions for star formation and stellar feedback and compare directly to previous simulations of the same region without these prescriptions to determine their role in shaping the dynamics inherited from the cluster assembly process. The stellar mass of the cluster grows through star formation within the cluster and accretion of new stars and star forming gas from a nearby filament. This growth results in an enhancement in the cluster's rotation and anisotropic expansion compared to simulations without star formation. We also analyze the internal kinematics of the cluster once it has lost most of its gas and find that the rotational velocity and the velocity anisotropy profiles are qualitatively similar to those expected of clusters that have undergone violent relaxation. As well, rotation and anisotropic expansion are still present by the time of gas removal. This implies that evolution within the GMC was unable to completely erase the kinematics inherited by the merger.

Galaxy clusters in the local Universe are dominated by massive quiescent galaxies with old ages, formed at high redshifts. It is debated whether their quenching is driven by internal processes or environmental effects, which has been challenging due to the lack of observations during their peak formation epoch. Here we report clear evidence from ALMA of extended and elongated gas tails in nine galaxies in a forming cluster at z = 2.51. The distinct gas distribution compared to the stellar emission probed by JWST, which is rather isolated without signatures of mergers or interactions, provides evidence of ram-pressure stripping (RPS). This represents the most distant confirmed case of RPS, highlighting the critical role of environmental effects in gas removal at high redshifts, an often overlooked quenching pathway.

Radio-frequency interference (RFI) is a major systematic limitation in radio astronomy, particularly for science cases requiring high sensitivity, such as 21-cm cosmology. Traditionally, RFI is dealt with by identifying its signature in the dynamic spectra of visibility data and flagging strongly affected regions. However, for RFI sources that do not occupy narrow regions in the time-frequency space, such as persistent local RFI, modeling these sources could be essential to mitigating their impact. This paper introduces two methods for detecting and characterizing local RFI sources from radio interferometric visibilities: matched filtering and maximum a posteriori (MAP) imaging. These algorithms use the spherical wave equation to construct three-dimensional near-field image cubes of RFI intensity from the visibilities. The matched filter algorithm can generate normalized maps by cross-correlating the expected contributions from RFI sources with the observed visibilities, while the MAP method performs a regularized inversion of the visibility equation in the near field. We also develop a full polarization simulation framework for RFI and demonstrate the methods on simulated observations of local RFI sources. The stability, speed, and errors introduced by these algorithms are investigated, and, as a demonstration, the algorithms are applied to a subset of NenuFAR observations to perform spatial, spectral, and temporal characterization of two local RFI sources. We assess the impact of local RFI on images, the uv plane, and cylindrical power spectra through simulations and describe these effects qualitatively. We also quantify the level of errors and biases that these algorithms induce and assess their implications for the estimated 21-cm power spectrum with radio interferometers. The near-field imaging and simulation codes are made available publicly in the Python library nfis.

We present globally inverted pressure-temperature (P-T) phase diagrams up to 5,000 GPa for four fundamental planetary materials, Fe, MgO, SiO2, and MgSiO3, derived from logistic regression and supervised learning, together with an experimental phase equilibria database. These new P-T phase diagrams provide a solution to long-standing disputes about their melting curves. Their implications extend to the melting and freezing of rocky materials in the interior of giant planets and super-Earth exoplanets, contributing to the refinement of their internal structure models.

Primordial non-Gaussianity (PNG) is a signature of fundamental physics in the early universe that is probed by cosmological observations. It is well known that the local type of PNG generates a strong signal in the two-point function of large-scale structure tracers, such as galaxies. This signal, often termed ``scale-dependent bias'' is a generic feature of modulation of gravitational structure formation by a large-scale mode. It is less well-appreciated that the coefficient controlling this signal, $b_{\phi}$, is closely connected to the time evolution of the tracer number density. This correspondence between time evolution and local PNG can be simply explained for a universal tracer whose mass function only depends on peak height, and more generally for non-universal tracers in the separate universe picture, which we validate in simulations. We also describe how to recover the bias of tracers subject to a survey selection function, and perform a simple demonstration on simulated galaxies. Since the local PNG amplitude in $n-$point statistics ($f_{\rm NL}$) is largely degenerate with the coefficient $b_{\phi}$, this proof of concept study demonstrates that galaxy survey data can allow for more optimal and robust extraction of local PNG information from upcoming surveys.

How radial flows shape galaxy structure and evolution remains an open question. Internal drivers of such flows, such as bars and spiral arms, known to mediate gas flows in the local Universe, are now observable at high redshift thanks to JWST's unobscured view. We investigate the morphology of massive star-forming galaxies at 0.8 < z < 1.3 and 2.0 < z < 2.5, epochs marking the peak and decline of cosmic star formation, both well-covered by kinematic surveys. Using JWST/NIRCam imaging, we visually classify 1,451 galaxies, identify non-axisymmetric features, count the number of spiral arms, analyze non-parametric morphological indicators and study the dynamical support of the sample covered by kinematics (10% of the sample) as measured via v/{\sigma}. Disk galaxies dominate the sample (82%), with 48% exhibiting spiral structure and 11% hosting bars. Both fractions decline with redshift, consistent with previous studies. The proportion of two- and three-armed spirals remains largely unchanged across redshift, with roughly two-thirds showing two arms and one-third showing three arms in both bins. Notably, we find a higher incidence of three-armed spirals than reported in the local Universe, suggesting a mild evolution in spiral arm multiplicity. Non-parametric morphological metrics strongly correlate with stellar mass but show no significant redshift evolution. Finally, kinematic analysis reveals a strong correlation between disk morphology and rotational support, with most disks exhibiting v/{\sigma} > 3 and median values of v/{\sigma} > 7 for spirals and v/{\sigma} > 5 for barred galaxies. This study establishes a population-wide framework for linking galaxy morphology and dynamics at cosmic noon, providing a key reference for future studies on the role of detailed structural features in galaxy evolution.

Line-intensity mapping (LIM) is a growing technique that measures the integrated spectral-line emission from unresolved galaxies over a three-dimensional region of the Universe. Although LIM experiments ultimately aim to provide powerful cosmological constraints via auto-correlation, many LIM experiments are also designed to take advantage of overlapping galaxy surveys, enabling joint analyses of the two datasets. We introduce a flexible simulation pipeline that can generate mock galaxy surveys and mock LIM data simultaneously for the same population of simulated galaxies. Using this pipeline, we explore a simple joint analysis technique: three-dimensional co-addition (stacking) of LIM data on the positions of galaxies from a traditional galaxy catalogue. We test how the output of this technique reacts to changes in experimental design of both the LIM experiment and the galaxy survey, its sensitivity to various astrophysical parameters, and its susceptibility to common systematic errors. We find that an ideal catalogue for a stacking analysis targets as many high-mass dark matter halos as possible. We also find that the signal in a LIM stacking analysis originates almost entirely from the large-scale clustering of halos around the catalogue objects, rather than the catalogue objects themselves. While stacking is a sensitive and conceptually simple way to achieve a LIM detection, thus providing a valuable way to validate a LIM auto-correlation detection, it will likely require a full cross-correlation to achieve further characterization of the galaxy tracers involved, as the cosmological and astrophysical parameters we explore here have degenerate effects on the stack.

Pair-instability supernovae (PISNe) are predicted thermonuclear explosions of massive stars with helium core masses exceeding $\sim 65M_\odot$ and synthesize substantial amounts of radioactive $\mathrm{^{56}Ni}$ ($M(\mathrm{^{56}Ni})\sim60M_\odot$ in extreme cases). To investigate their observational signatures, we developed a 1D Monte Carlo radiation transport code and performed simulations of gamma-ray and hard X-ray emissions from the decay chain $\mathrm{^{56}Ni}\to\mathrm{^{56}Co}\to\mathrm{^{56}Fe}$. We find that key gamma-ray lines (847 and 1238 keV) from $\mathrm{^{56}Co}$ decay in the $130M_\odot$ helium core model can be detected up to 300-400 Mpc by next-generation MeV gamma-ray telescopes. In contrast, the signals from the $100M_\odot$ model remain below the detection limits. Our results provide the template for gamma-ray follow-up observations of PISNe. Considering theoretical predictions and observational constraints, we estimate PISN event rates within 300 Mpc to be approximately 0.1 events per year, highlighting their rarity but also emphasizing their feasibility as targets for future gamma-ray observations over the decade.

The formation and evolution of galaxies cannot be separated from large scale structure growth. Dark matter halos (and, therefore, galaxies) form and grow within the cosmic web - the classification of large-scale structure as distinct environments, namely voids, walls, filaments and nodes. Thanks to the rapid development of extragalactic spectroscopic redshift surveys and cosmological simulations over the last two decades, we are now able to measure the impact of the cosmic web on galaxies and halos in observations and in simulations. In this chapter we summarise the state of play in our understanding of the link between dark matter halos, galaxies, and the cosmic web.

We discuss generalized linear models for directional data where the conditional distribution of the response is a von Mises-Fisher distribution in arbitrary dimension or a Bingham distribution on the unit circle. To do this properly, we parametrize von Mises-Fisher distributions by Euclidean parameters and investigate computational aspects of this parametrization. Then we modify this approach for local polynomial regression as a means of nonparametric smoothing of distributional data. The methods are illustrated with simulated data and a data set from planetary sciences involving covariate vectors on a sphere with axial response.

In this paper we discuss possible consequences of a manifestly non-commutative and $T$-duality covariant formulation of string theory on dark energy, when the correspondence between short distance (UV) and long distance (IR) physics is taken into account. We demonstrate that the dark energy is dynamical, \textit{i.e.}, time-dependent, and we compute the allowed values of $w_0$ and $w_a$, given by $w(a) = w_0+w_a(1-a)$, which compare favorably to the most recent observations by DESI. From this point of view, the latest results from DESI might point to a fundamentally new understanding of quantum spacetime in the context of quantum gravity.

We show that the simplest generalization of the chaotic inflation model $\tfrac12 {m^{2}\phi^{2}}$ with nonminimal coupling to gravity $(1+\phi) R$ provides a good match to the results of the latest data release of the Atacama Cosmology Telescope, with $r \approx10^{-2}$.

The equation of state for dense nuclear matter in $\beta$-equilibrium is explored including the possibility of a doubly-strange H-particle. Consistent with experimental constraints, the mass of the H in free space is taken to be near the $\Lambda \, \Lambda$ threshold. Within the quark-meson coupling model, which we use, no new parameters are required to describe the interaction between the H-dibaryon and the other baryons. The maximum mass is only slightly reduced, and the tidal deformability is essentially unchanged with this addition. In heavy neutron stars the H is abundant and extends as far as 6 km from the center of the core.

The possible existence of an H-dibaryon near the $\Lambda-\Lambda$ threshold has still not been decided experimentally. This raises the question of the potential effects on neutron stars if it does exist. We explore the consequences within the quark-meson coupling model, using the excluded volume formalism. While the H is abundant in heavy stars the maximum mass is only lowered slightly by its presence.

The quasinormal mode spectrum of black holes is unstable against small modifications of the radial potential describing massless perturbations. We study how these small modifications affect the convergence of the quasinormal mode expansion and the mode excitation by computing the mode amplitudes from first principles, without relying on any fitting procedure. We show that the decomposition of the prompt ringdown waveform is not unique: small modifications in the radial potential produce new quasinormal mode ''basis sets'' that can improve the convergence of the quasinormal mode expansion, even capturing the late-time tail. We also study avoided crossings and exceptional points of the Kerr and Kerr-de Sitter spectrum. We show that while the mode amplitude can be resonantly excited, modes that exhibit avoided crossing destructively interfere with each other, so that the prompt ringdown waveform remains stable.

The Wheeler-DeWitt (WDW) equation is analyzed using two boundary proposals: the Hartle-Hawking no-boundary condition and tunneling condition. By compactifying the scale factor $a$ into $x = a/(1+a)$, we reformulate the WDW equation to find stable numerical solutions with clearer boundary conditions. The no-boundary wave function peaks at the horizon scale, indicating quantum nucleation of classical spacetime, while the tunneling solution shows exponential decay, reflecting vacuum decay from a classically forbidden state. These dynamics are explored under slow-roll and non-slow-roll regimes of a periodic potential, separately, with non-slow-roll scenarios amplifying quantum effects that delay the classical behavior. The results emphasize the role of boundary conditions in quantum cosmology, offering insights into the universe's origin and the interplay between quantum gravity and observable cosmology.

Long-baseline atom interferometry is a promising technique for probing various aspects of fundamental physics, astrophysics and cosmology, including searches for ultralight dark matter (ULDM) and for gravitational waves (GWs) in the frequency range around 1~Hz that is not covered by present and planned detectors using laser interferometry. The MAGIS detector is under construction at Fermilab, as is the MIGA detector in France. The PX46 access shaft to the LHC has been identified as a very suitable site for an atom interferometer of height $\sim 100$m, sites at the Boulby mine in the UK and the Canfranc Laboratory are also under investigation, and possible sites for km-class detectors have been suggested. The Terrestrial Very-Long-Baseline Atom Interferometry (TVLBAI) Proto-Collaboration proposes a coordinated programme of interferometers of increasing baselines.

We study the linear polarization of the accretion disk around black holes with a dark matter halo. The interaction of the black hole with the dark matter is modelled by considering an exact solution to the Einstein equations which describes a superposition of the Schwarzschild black hole with a Hernquist-type matter distribution. We simulate the observable polarization of a magnetized fluid ring orbiting around the black hole and evaluate the influence of the dark matter halo on its properties for physical parameters compatible with the dark matter distribution in galaxies. The polarization intensity and direction of the direct images deviate with less than $1\%$ from the isolated Schwarzschild black hole for a range of magnetic field configurations. For the indirect images the deviation increases with an order of magnitude but still remains under $10\%$ for small inclination angles corresponding to the galactic targets M87* and Sgr A*. This makes the detection of the dark matter impact on the polarized emission from the accretion disk extremely challenging in the near future.

Palatini $F(R,X)$ gravity, with X the inflaton kinetic term, proved to be a powerful framework for generating asymptotically flat inflaton potentials. Here we show that a quadratic Palatini $F(R,X)$ restores compatibility with data of the Peebles-Vilenkin quintessential model. Morever, the same can be achieved with an exponential version of the Peebles-Vilenkin potential if embedded in a Palatini $F(R,X)$ of order higher than two.

Mounting theoretical evidence suggests that black holes are subjected to the memory burden effect, implying that after certain time the information stored in them suppresses the decay rate. This effect opens up a new window for small primordial black holes (PBHs) below $10^{15}\,{\rm g}$ as dark matter. We show that the smooth transition from semi-classical evaporation to the memory-burdened phase strongly impacts observational bounds on the abundance of small PBHs. The most stringent constraints come from present-day fluxes of astrophysical particles. Remarkably, currently-transitioning small PBHs are detectable through high-energetic neutrino events.