Papers for Tuesday, Jun 17 2025

The spin of a black hole (BH) encodes information about its formation and evolution history. Yet the understanding of the distribution of BH spins in X-ray binaries (XBs), of the models used to measure spin, and of their impact on systematic uncertainties remains incomplete. In this work, we expand on previous analyses of the entire NuSTAR archive of accreting BH XBs. Prior work compiled a sample of 245 spectral fits using the relativistic reflection method for NuSTAR observations of 36 BH systems. Here, we aim to probe two aspects: the connection between BH spin and binary system properties, and the relationship between parameters in spectral fits. We identify moderate negative correlations between spin uncertainty and both BH mass and system inclination, and a moderate positive correlation with distance. We also point out tentative multi-dimensional degeneracies between inclination, disk density, Fe abundance, ionization, and the presence or absence of absorption features from ionized outflows linked to disk winds. Lastly, we provide a comprehensive view of the observed distribution of BH spins in XBs, in comparison to spins inferred from gravitational waves. We find that the distribution of BH spins in XBs can be described by a Beta distribution with $\alpha=5.66$ and $\beta=1.09$. This data set is highly complex, and the analysis presented here does not fully explore all potential parameter correlations. We make the full data set available to the community to encourage further exploration.

We present an extension of the pop-cosmos model for the evolving galaxy population up to redshift $z\sim6$. The model is trained on distributions of observed colors and magnitudes, from 26-band photometry of $\sim420,000$ galaxies in the COSMOS2020 catalog with Spitzer IRAC $\textit{Ch. 1}<26$. The generative model includes a flexible distribution over 16 stellar population synthesis (SPS) parameters, and a depth-dependent photometric uncertainty model, both represented using score-based diffusion models. We use the trained model to predict scaling relationships for the galaxy population, such as the stellar mass function, star-forming main sequence, and gas-phase and stellar metallicity vs. mass relations, demonstrating reasonable-to-excellent agreement with previously published results. We explore the connection between mid-infrared emission from active galactic nuclei (AGN) and star-formation rate, finding high AGN activity for galaxies above the star-forming main sequence at $1\lesssim z\lesssim 2$. Using the trained population model as a prior distribution, we perform inference of the redshifts and SPS parameters for 429,669 COSMOS2020 galaxies, including 39,588 with publicly available spectroscopic redshifts. The resulting redshift estimates exhibit minimal bias ($\text{median}[\Delta_z]=-8\times10^{-4}$), scatter ($\sigma_\text{MAD}=0.0132$), and outlier fraction ($6.19\%$) for the full $0<z<6$ spectroscopic compilation. These results establish that pop-cosmos can achieve the accuracy and realism needed to forward-model modern wide--deep surveys for Stage IV cosmology. We publicly release pop-cosmos software, mock galaxy catalogs, and COSMOS2020 redshift and SPS parameter posteriors.

Uncovering bright quasars' host galaxies at cosmic noon is challenging because of the high contrast between the quasar and its host and redshifted light, making them primarily visible in the infrared. We present JWST NIRSpec integral field unit (IFU) observations of six extremely red quasars (ERQs) at $z=2.4-2.9$ and two dust-obscured quasars at lower redshifts. Using image decomposition across the spectral range, we successfully separate quasar and host galaxy continuum emission, model host morphologies, and extract spectra. The ERQs and obscured quasars have compact host galaxies with half-light radii of 1.4$-$2.9 kpc and stellar masses of 10$^{10.6-10.9}$ $M_{\odot}$. Their stellar masses are consistent with the average stellar mass of quasar hosts as expected from abundance matching and clustering analysis. Most of the quasars in our sample exhibit significant spatial offsets (0.4$-$1.3 kpc) between the quasar and host galaxy, potentially caused by post-merger dynamics or non-uniform dust obscuration. The ERQs reside 0.5$-$2 dex above the local black hole-stellar mass relation, similar to other heavily obscured populations such as HotDOGs, optically selected quasars at cosmic noon, and high-redshift SMBH candidates identified with JWST. However, this "over-massive" feature might be attributed to selection bias. Compared to HST-based studies, our JWST measurements reveal more compact host galaxies, smaller Sersic indices, and lower stellar masses, likely because of improved resolution, more accurate modeling, and minimal line contamination. These findings highlight the unique capabilities of JWST IFU in revealing quasar host galaxy properties and potential evolutionary stages of obscured quasars at cosmic noon.

X-ray scattering is a powerful probe of the optical constants and grain size distribution of interstellar dust. Bright, transient sources are excellent tools for this, since they fade rapidly, leaving only the expanding scattered x-ray halo. Here, we analyse the dust-scattered x-ray halo data of the unprecedentedly bright $\gamma$-ray burst, GRB 221009A, using anomalous diffraction theory to measure the grain size distribution of dust in the Galaxy as well as the complex refractive index, $m$, and use these results to infer the likely composition. We find a complex refractive index, $m=n+ik$ at several x-ray energies, finding $k_{1\,\mathrm{keV}}= (2.7 \pm 0.7)\times10^{-4}$ and $1-n_{1\,\mathrm{keV}}= (9 \pm 2)\times 10^{-4}$, strongly inconsistent with the commonly employed assumptions of the Rayleigh-Gans approximation. These results lie in the expected range for interstellar dust compositions dominated by carbon, magnesium silicates, and iron. The absorption results suggest a substantial mass fraction of iron at $35\pm7\%$. The MRN distribution fit returns a maximum grain radius, $a_{\rm max}=0.24\pm 0.01\,\mu$m; all fits strongly rule out models with $\sim0.4\,\mu$m grains for this sightline. The soft x-ray spectrum of the prompt GRB can also be inferred from the fitting, with the best-fit providing a spectral slope that is consistent with the slope of the low energy side of the best-fit Band model of the directly measured prompt emission. Forcing a different grain size or composition than the best fit results in an inferred prompt spectrum different to the observed prompt emission. The refractive index is consistent with standard average dust compositions, showing that x-ray scattering is an effective tool to measure interstellar dust optical properties. [abridged]

The gas-phase metallicity gradients of galaxies have been extensively studied over the past four decades both in the local and high-redshift universe, as they trace the baryon cycle and growth of galaxies. With the unprecedented spatial resolution and sensitivity of the James Webb Space Telescope (JWST), it is now possible to measure metallicity and its radial gradients out to redshifts as high as $z = 9$. Here, we present a sample of 456 spectroscopically confirmed galaxies from redshifts $1.5 \lesssim z \lesssim 9$ that are spatially resolved on sub-kiloparsec (kpc) scales by deep JWST NIRCam or NIRISS Wide Field Slitless Spectroscopy (WFSS). Synthesizing these new JWST observations with legacy observations from the literature, we observe that at redshift $z > 5$, galaxy centers are more metal-rich, exhibiting negative metallicity gradients of $\sim-0.4$ dex kpc$^{-1}$. These gradients flatten over time, reaching near-zero around $z \approx 2$, coinciding with the peak of the cosmic star formation rate. Beyond this point, the gradients become negative again at lower redshifts approaching $z=0$. This evolution likely reflects transitions in galaxy formation modes: an inside-out growth phase dominated by intense central star formation with inefficient feedback and limited gas mixing during ``cosmic dawn", enhanced gas mixing due to feedback-driven wind and gas accretion at ``cosmic noon", and a later phase of slow evolution and reduced feedback toward the present day. These physical processes including gas accretion and feedback not only regulate star and galaxy formation on cosmic scale, but also shape the evolutionary pathways of individual galaxies over cosmic time.

JWST has enabled a new era of understanding high-z galaxy and black hole evolution with more than 30 high-z quasar host galaxy detections. Many of these observations imply galaxies with black holes that are overmassive compared to their low-z counterparts. However, the bright quasar point source removal may cause significant biases in these stellar mass measurements. We develop a simulation-based inference method to disentangle the quasar host galaxy stellar mass measurements from observational biases during the point source removal. We use the BlueTides simulation to generate mock images and perform point source removal on thousands of simulated high-z quasar host galaxies, constructing corrected host magnitude posteriors. We find that JWST photometry tends to either correctly recover or modestly misestimate host magnitudes, with a maximum magnitude underestimate of 0.21 mag. With our corrected magnitude posteriors, we perform SED fitting on each quasar host galaxy and compare the stellar mass measurement before and after the correction. We find that stellar mass estimates are generally robust, or overestimated by $\leq0.3$ dex. We also find that the stellar masses of a subset of hosts (J1120+0641, J0844-0132, J0911+0152, and J1146-0005) remain unconstrained, as key photometric bands provide only flux upper limits. Understanding these biases is essential to uncovering the evolutionary pathways of high-z quasars with their hosts.

We explore the growth of structure in wave-like dark matter models, where the field and density spectra are peaked at sub-horizon wavenumbers. Starting with the Schrödinger-Poisson system, we derive the scale-dependent evolution of the matter power spectrum during radiation and matter domination. We find a suppression of adiabatic perturbations during radiation domination, controlled by a free-streaming length, and scale-dependent growth of the initially white-noise isocurvature power, controlled by a Jeans scale during matter domination. The results are in qualitative, and in some regimes quantitative, agreement with the quasi-particle picture. We verify the analytic results of the power spectrum with 3+1-dimensional cosmological Schrödinger-Poisson simulations. We propose an analytic formula for the halo mass function, which is in rough agreement with the simulation results at early times after matter-radiation equality. Our simulations show that early halos typically host a soliton.

The objective of this study is to analytically explore mass loss and gain induced by stellar collisions on a gas-accreting extremely massive star (aEMS, 10^3 <= M/M_sun <= 10^4). We also consider its contribution to the mass budget in the context of forming multiple stellar populations in a typical protoglobular cluster. We used MESA to build a series of aEMS models up to 2e4 M_sun for three [Fe/H] values, covering the metallicity range of Galactic GCs, with different treatments of super-adiabatic convection. We set analytical prescriptions to quantify collision-induced mass loss when a star spirals in and deposits energy into the envelope of the aEMS. We used a Monte Carlo approach to simulate the effects of multiple collisions on an aEMS of initial mass 10^3 M_sun in a static proto-GC, accounting for mass loss and gain from collisions, gas accretion, and stellar winds. We show that assumptions on super-adiabaticity in radiation-dominated layers significantly impact aEMS properties and their collision responses: extended stars tend to lose mass, while compact ones are more likely to gain it. Our MC simulations predict total mass lost and gained, along with timescales and contributions from winds and collisions. The results depend on both the aEMS structure and the gas accretion rate during the collision phase. Under certain conditions, the EMS shows a "conveyor belt" behavior, processing up to 10^5.5 M_sun of material in 5 Myr. This study provides theoretical predictions supporting aEMSs as contributors to the abundance anomalies observed in GCs. It emphasizes the need to include collision dynamics and mass transfer in aEMS formation and evolution models in dense stellar environments. We provide a grid of predictions for stellar M-R-[Fe/H]-structure relations and collision-induced mass loss and gain, suitable for hydro and N-body simulations.

We present an analysis of the optical and near-infrared properties of SN 2022lxg, a bright ($\rm M_{g\, \mathrm{peak}}=-19.41$ mag) and rapidly evolving SN. It was discovered within a day of explosion, and rose to peak brightness in 10 d. Two distinct phases of circumstellar interaction are evident in the data. The first is marked by a steep blue continuum (T $>15,000$ K) with flash-ionisation features due to hydrogen and He II. The second, weaker phase is marked by a change in the colour evolution accompanied by changes in the shapes and velocities of the spectral line profiles. Narrow P-Cygni profiles (~ $150$ km s$^{-1}$) of He I further indicate the presence of slow-moving unshocked material and suggesting partial stripping of the progenitor. The fast decline of the light curve from peak (3.48$\pm$ 0.26 mag $\rm (50\,d)^{-1}$ in $g$-band) implies that the ejecta mass must be low. Spectroscopically, until $+35$ d there are similarities to some Type IIb SNe but then there is a transition to spectra that are more reminiscent of an interacting SN II. However, metal lines are largely absent in the spectra, even at epochs of 80 d. Its remote location from the presumed host galaxy, a dwarf with $\rm M_B$ ~ $-14.4$ mag, is consistent with our metallicity estimate - close to the SMC value - obtained from scaling relations. Furthermore, several lines of evidence (including intrinsic polarisation of $p$ ~ (0.5-1.0) %) point to deviations from spherical symmetry. We suggest that a plausible way of uniting the observational clues is to consider a binary system that underwent case C mass transfer. This failed to remove the entire H-envelope of the progenitor before it underwent core-collapse. In this scenario, the progenitor itself would be more compact and perhaps straddle the boundary between blue and yellow supergiants, tying in with the early spectroscopic similarity to Type IIb SNe.

We present 90 GHz continuum imaging of 119 star-forming regions in 30 nearby galaxies observed with MUSTANG-2 on the Robert C. Byrd Green Bank Telescope as part of the Star Formation in Radio Survey. The 90 GHz data were combined with 3, 15, and 33 GHz data taken previously by the Karl G. Jansky Very Large Array to decompose radio spectra on $\approx$0.8 kpc scales into their synchrotron, free-free, and thermal dust emission components. This was done using three scenarios: (i) a power law fit from 3 to 33 GHz, (ii) Markov Chain Monte Carlo (MCMC) fitting from 3 to 90 GHz with a thermal dust component, and (iii) MCMC fitting from 3 to 33 GHz without a thermal dust component. For these cases, we find a median thermal (free-free) emission fraction at 33 GHz of (i) $88 \pm 2$% with a scatter of 17%, (ii) $76\pm 3$% with a scatter of 25%, and (iii) $84\pm 2$% with a scatter of 18%. From this we conclude that, on average, free-free, not thermal dust, remains the dominant emission component at 33 GHz. While scenario (ii) yields a thermal fraction that is $\approx$10% larger than scenario (iii), this difference decreases to $\approx$5% after AGN are removed. Consequently, star formation rates measured with thermal fractions at 33 GHz are only mildly biased high without 90 GHz data for the spectral decomposition. Furthermore, a power law fit of data from 3 to 33 GHz still provides a reliable estimate of the free-free emission at 33 GHz.

Ly-$\alpha$ observations provide a powerful probe of stellar activity and atmospheric escape in exoplanetary systems. We present here an analysis of 104 HST/STIS orbits monitoring the TRAPPIST-1 system between 2017 and 2022, covering 3--5 transits for each of its seven planets. We rule out transit depths $\gtrsim20\%$, which translates into an upper limit on the escape rate of $1064~EO_H$/Gyr for planet b ($1~EO_H$ is the Earth-ocean-equivalent hydrogen content), in agreement with recent claims that planet b should be airless. These upper limits are $\sim$3 times larger than expected from the photon noise due to a large baseline scatter, which we ultimately link to TRAPPIST-1's intrinsic Ly-$\alpha$ variability from frequent ``microflares.'' While JWST observations of TRAPPIST-1 in the near infrared have shown that $\sim10^{30}$-erg flares occur every $\sim$6 hours, we report here $\sim10^{29}$-erg flares on sub-hour timescales in the HST/STIS and also Very Large Telescope (VLT) $g^{'}$ observations. The FUV and optical amplitudes ($\sim$400$\%$ vs $\sim$3$\%$, respectively) for flares with similar waiting-times indicate flare temperatures of 11000$^{+4200}_{-3100}$~K over 0.011$^{+0.03}_{-0.01}$\% of the stellar disk. Finally, our multi-year baseline reveals a variability with $P = 3.27 \pm 0.04$ days, providing further validation of the previously reported 3.295-day rotation period for TRAPPIST-1. These results highlight the importance of accounting for stellar microvariability when searching for exospheres around active M dwarfs.

We report the discovery of a little red dot (LRD), dubbed BiRD ('big red dot'), at $z=2.33$ in the field around the $z=6.3$ quasar SDSSJ1030+0524. Using NIRCam images, we identified it as a bright outlier in the $F200W-F356W$ color vs $F356W$ magnitude diagram of point sources in the field. The NIRCam/WFSS spectrum reveals the emission from HeI$\lambda 10830$ and PaG line, both showing a narrow and a broad ($FWHM\gtrsim 2000\ \rm kms^{-1}$) component. The HeI line is affected by an absorption feature, tracing dense gas with HeI column density in the $2^3S$ level $N\sim 0.5-1.2\times 10^{14}\rm cm^{-2}$, depending on the location of the absorber, which is outflowing at the speed of $\Delta v \sim -830\ \rm kms^{-1}$. As observed in the majority of LRDs, BiRD does not show X-ray or radio emission. The BH mass and the bolometric luminosity, both inferred from the PaG broad component, amount to $M_{\rm BH}\sim 10^8\rm M_{\odot}$ and $L_{\rm bol}\sim 2.9\times 10^{45}\rm ergs^{-1}$, respectively. Intriguingly, BiRD presents strict analogies with other two LRDs spectroscopically confirmed at cosmic noon, GN-28074 ("Rosetta Stone") at $z=2.26$ and RUBIES-BLAGN-1 at $z=3.1$. The blueshifted HeI absorption detected in all three sources suggests that gas outflows may be common in LRDs. We derive a first estimate of the space density of LRDs at $z<3$ based on JWST data, as a function of $L_{\rm bol}$ and BH mass. The space density is only a factor of $\sim 2-3$ lower than that of UV-selected quasars with comparable $L_{\rm bol}$ and $z$, meaning that the contribution of LRDs to the broader AGN population is also relevant at cosmic noon. A similar trend is also observed in terms of BH masses. If, as suggested by recent theories, LRDs probe the very first and rapid growth of black hole seeds, our finding may suggest that the formation of black hole seeds remains efficient at least up to cosmic noon.

Cassini's observations of Titan's atmosphere are exemplary benchmarks for exoplanet atmospheric studies owing to (1) their precision and (2) our independent knowledge of Titan. Leveraging these observations, we perform retrievals (i.e., analyses) of Titan's transmission spectrum to investigate the strengths/limitations of exoplanet atmospheric retrievals with a particular focus on the underlying assumptions regarding the molecular species included in the retrieval. We find that multiple hydrocarbons can be ``retrieved'' depending on the selection made ahead of a retrieval. More importantly, we find that the estimates of other parameters such as the abundance of key absorbers like methane can be biased by $\sim$0.5 dex (by a factor of $\sim$3) due to such choices. This shows that beyond the possible misidentification of a molecular feature (e.g., current debate surrounding dimethyl sulfide, DMS, in K2-18 b), the implicit molecular detections made pre-retrieval to avoid retrieving for hundreds of molecules at a time can bias a large range of parameters. We thus recommend sensitivity analysis to assess the dependencies of atmospheric inferences on such selections in tandem with complementary information (e.g., chemistry models) to support any pre-retrieval selection. Finally, we introduce an independent path to constrain the dominant atmospheric constituent, even when lacking observable absorption feature (e.g., H$_2$ and N$_2$) through the scale height.

We present 21 infrared transients found in our three-epoch, four-band NIRCam observations covering 14.16 arcmin^2 in the Spitzer IRAC Dark Field (IDF), taken by the JWST Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) program in Cycle 1 with a time cadence of ~6 months. A separate HST program provided complementary ACS optical imaging contemporaneous with the second and third epochs of the NIRCam observations. Spectroscopic identifications were carried out for three transients using the NIRSpec instrument. One of them was confirmed to be a Type Ia supernova at z=1.63, while the other two had their host galaxies identified at $z=2.64$ and 1.90, respectively. Combining these redshifts with the photometric redshifts of the host galaxies in the rest of the sample, we find that the transients are either in a "mid-z" group at z>1.6 with M_V < -16.0 mag or a "low-z" group at z<0.4 with M_H > -14.0 mag. The mid-z transients are consistent with various types of supernovae. In contrast, by their luminosities, the low-z transients fall in the range of the so-called ``gap transients'' between those of supernovae and classical novae. While they might contain some known types of gap transients (e.g., supernova impostors and luminous red novae), there could also be new kinds of transients. To reveal their nature, we will need a long-term, multi-band NIRCam monitoring program with a higher cadence and prompt NIRSpec follow-up spectroscopy. Being in the continuous viewing zone of the JWST, the IDF is an ideal field for such a future program.

We investigate the redshift evolution of disk and bulge-dominated galaxies using a mass-complete sample of $\sim$14,000 galaxies from the CANDELS survey, selected with $H_{\rm mag} \leq 24$, $M_{\rm stellar} \geq 10^9\,{\rm M}_\odot$, and spanning $0.2 \leq z \leq 2.4$. Adopting an unbiased morphological classification, free from visual inspection or parametric assumptions, we explore the evolution of specific star formation rate (sSFR), stellar mass, structural properties, and galaxy fractions as a function of redshift and morphology. We find that while disk and bulge-dominated galaxies exhibit similar sSFR distributions at $z \sim 2.4$, bulge-dominated systems develop a redshift-dependent bimodality below $z < 1.6$, unlike the unimodal behaviour of disks. This bimodality correlates with stellar mass: bulge-dominated galaxies with lower sSFR are significantly more massive and exhibit higher Sérsic indices than their star-forming counterparts, despite having similar effective radii. Based on a Gaussian mixture decomposition, we identify two evolutionary tracks for bulge-dominated galaxies: G1, a long-lived, star-forming population with disk-like properties; and G2, a quenched, massive population whose prominence increases with decreasing redshift. The evolution of the star formation main sequence and morphology--mass fractions support a scenario in which G2 systems form through merger-driven transformations of massive disks. Our results indicate that bulge-dominated galaxies are not a homogeneous population, but instead follow divergent evolutionary paths driven by distinct physical mechanisms.

Galaxy clusters host a hot, diffuse plasma with poorly understood viscosity and magnetic field amplification. Astrophysical plasmas are often modeled with magnetohydrodynamics (MHD), but low collision rates in environments like the intracluster medium (ICM) hinder thermodynamic equilibrium, causing pressure anisotropies and high viscosity. High-$\beta$ plasmas, dominated by thermal pressure, are prone to instabilities (e.g., firehose, mirror) that limit anisotropy, reduce viscosity, and enable small-scale dynamo-driven magnetic amplification. This study examines viscosity evolution in the ICM during turbulent magnetic field amplification. We performed 3D MHD simulations of forced turbulence with an initially weak, uniform magnetic field. Using the CGL-MHD framework, we incorporate anisotropic pressure dynamics and instability-driven anisotropy limitation. We analyze effective viscosity and dynamo evolution, comparing results with Braginskii-MHD and uniform-viscosity MHD. Results show viscosity decreases over time, allowing magnetic field amplification to saturation levels similar to non-viscous MHD. Viscosity distribution becomes bimodal, reflecting (i) collisional values and (ii) turbulence-dominated values proportional to $10^{-4} L_{\rm turb} U_{\rm turb}$ in unstable regions. At saturation, 60% of plasma retains collisional viscosity. Braginskii-MHD reproduces similar magnetic amplification and viscosity structures. However, uniform-viscosity MHD, where viscosity equals the mean saturated CGL-MHD value, fails to capture the turbulence inertial range. These findings highlight the need for anisotropic viscosity models in studying ICM processes like magnetic topology, cosmic ray transport, and AGN-driven shocks. Moreover, our CGL-MHD and Braginskii-MHD models match the Coma cluster density fluctuation spectrum, reinforcing its weakly collisional nature.

This textbook provides a systematic treatment of statistical machine learning for astronomical research through the lens of Bayesian inference, developing a unified framework that reveals connections between modern data analysis techniques and traditional statistical methods. We show how these techniques emerge from familiar statistical foundations. The consistently Bayesian perspective prioritizes uncertainty quantification and statistical rigor essential for scientific inference in astronomy. The textbook progresses from probability theory and Bayesian inference through supervised learning including linear regression with measurement uncertainties, logistic regression, and classification. Unsupervised learning topics cover Principal Component Analysis and clustering methods. We then introduce computational techniques through sampling and Markov Chain Monte Carlo, followed by Gaussian Processes as probabilistic nonparametric methods and neural networks within the broader statistical context. Our theory-focused pedagogical approach derives each method from first principles with complete mathematical development, emphasizing statistical insight and complementing with astronomical applications. We prioritize understanding why algorithms work, when they are appropriate, and how they connect to broader statistical principles. The treatment builds toward modern techniques including neural networks through a solid foundation in classical methods and their theoretical underpinnings. This foundation enables thoughtful application of these methods to astronomical research, ensuring proper consideration of assumptions, limitations, and uncertainty propagation essential for advancing astronomical knowledge in the era of large astronomical surveys.

We present an analysis of the polarization of three black widow pulsars, PSRs B1957+20, J2055+3829 and J1544+4937 at 1250\,MHz using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Radio eclipses for PSRs B1957+20 and J2055+3829 are detected, while the radio emission for J1544+4937 is detected throughout the eclipse. We study the polarization and dispersion measure properties of the pulsars near and during the eclipse. The position angle of the linear polarization is observed to shift at the eclipse boundary in all of these three pulsars implying a lower limit line-of-sight magnetic field strength of the eclipse medium of approximately a few mG to tens of mG. We also find evidence that the magnetic field in the eclipse medium of PSRs B1957+20 and J1544+4937 reverses.

A numerical framework to calculate the height and potential of the vacuum inner gap is proposed here. The results show that small mountains on a pulsar's polar cap tend to significantly influence the properties of the inner vacuum gap, making it easier for sparks to form. In this scenario, the magnetospheric activity observed from the pulsars PSR J0250$+$5854 and PSR J2144$-$3933, which lie below the pulsar death line, would be reproduced, and the irregular discharge behaviour in other polar cap regions could also be understood. Furthermore, the presence of small mountains could provide a new way to probe the puzzling state of supranuclear matter inside pulsars. In order to have stable mountains on the surface, pulsars might be made of solid strangeon matter, which is favoured by both the charge neutrality and the flavour symmetry of quarks.

Galaxy mergers, each hosting a supermassive black hole (SMBH), are thought to form SMBH binaries. Motivated by recent observations from the East Asian VLBI Network (EAVN) showing periodic behavior in the M87 jet, a precession of about 11 years and a transverse oscillation of about 0.9 years, we constrain the mass of a hypothetical secondary black hole orbiting the primary SMBH in M87. To constrain the mass ratio between the primary SMBH ($M_{1}$) and the secondary black hole ($M_{2}$) defined as $q \equiv M_{2}/M_{1} \leq 1$, and the length of the semimajor axis of the binary system ($a$), we impose the following three constraints: (i) the lower limit of $a$, below which the SMBH binary is expected to merge. (ii) the strain amplitude of the gravitational wave background (GWB) at nanohertz frequencies shown in the NANOGrav 15-year dataset. (iii) a finite length of the semimajor axis of $M_{1}$, that can induce periodic behavior in the jet. By combining these constraints, we obtain the allowed parameter space for $q$ and $a$. If either of the EAVN-detected periods ($T$) corresponds to the binary's orbital period, the allowed range of $q$ is $6.9 \times 10^{-3} \le q \le 4.2 \times 10^{-2}$ for $T \approx 11$ years, and $3.7\times 10^{-2} \le q \le 1$ for $T \approx 0.9$ years. VLBI astrometric monitoring of the jet base of M87 is essential to explore the allowed parameter space for $q$ and $a$.

Tracking the correlation between radio and X-ray luminosities during black hole X-ray binary outbursts is a key diagnostic of the coupling between accretion inflows (traced by X-rays) and relativistic jet outflows (traced by radio). We present the radio--X-ray correlation of the black hole low-mass X-ray binary Swift~J1727.8$-$1613 during its 2023--2024 outburst. Our observations span a broad dynamic range, covering $\sim$4 orders of magnitude in radio luminosity and $\sim$6.5 in X-ray luminosity. This source follows an unusually radio-quiet track, exhibiting significantly lower radio luminosities at a given X-ray luminosity than both the standard (radio-loud) track and most previously known radio-quiet systems. Across most of the considered distance range ($D {\sim} 1.5--4.3$ kpc), Swift~J1727.8$-$1613 appears to be the most radio-quiet black hole binary identified to date. For distances ${\geq} 4$ kpc, while Swift~J1727.8$-$1613 becomes comparable to one other extremely radio-quiet system, its peak X-ray luminosity (${\gtrsim} 5{\times}10^{38}$ erg/s) exceeds that of any previously reported hard-state black hole low-mass X-ray binary, emphasising the extremity of this outburst. Additionally, for the first time in a radio-quiet system, we identify the onset of X-ray spectral softening to coincide with a change in trajectory through the radio--X-ray plane. We assess several proposed explanations for radio-quiet behaviour in black hole systems in light of this dataset. As with other such sources, however, no single mechanism fully accounts for the observed properties, highlighting the importance of regular monitoring and the value of comprehensive (quasi-)simultaneous datasets.

The data from the FAST and MeerKAT surveys has significantly increased the number of radio pulsars for which the polarization characteristics of their mean profiles have been determined in detail. This has allowed us to confirm earlier conclusions both about the nature of propagation of two orthogonal modes in the pulsar magnetospheres and about the mechanism of particle production in neutron star polar regions and their evolutionary features. We can now say with even greater confidence that mean profiles formed by the O-mode are significantly wider than those formed by the X-mode. Moreover, the observations confirm the validity of the classical Ruderman-Sutherland vacuum model of particle generation, as well as the evolution of the inclination angles of the magnetic axis to the rotation one in the direction of $90^{\circ}$.

In light of the recent results from the Atacama Cosmology Telescope (ACT), which have provided a notable shift in the constraints on $(n_s, r)$ and placed several otherwise viable models of inflation in tension with the latest data, we investigate the possible effects that radiative corrections can have on $\xi$-attractor and $\alpha$-attractor models of inflation. These models, which share much in common with Starobinsky-Higgs inflation, have likewise been put under pressure by these results. We find that percent (and even sub-percent) level radiative corrections can easily shift both of these classes of inflation models comfortably into the regions of parameter space favoured by the most recent constraints. However, the flexibility under such corrections (which one can argue should be generally expected) calls into question to what extent it is possible to precisely pin down model-specific predictions for important cosmological observables.

A recent study on the dynamics of the quasi-stationary component (QSC) in the jet of BL~ Lacertae highlighted its significance in evaluating the physical properties of relativistic transverse waves in the parsec-scale jet. Motivated by this finding, we selected a different type of blazar, the flat-spectrum radio quasar (FSRQ) 3C~279, which hosts a QSC at an angular median distance of 0.35~mas from the radio core, as revealed by 27 years of VLBA monitoring data at 15~GHz. We investigate the positional scatter and dynamics of a QSC in the 3C~279 jet, aiming to detect the presence of a relativistic transverse wave and estimate its characteristics. We employ an analytical statistical method to estimate the mean intrinsic speed of the QSC, while moving average and refinement methods are used to smooth its trajectory. Analysis of the QSC position scatter shows that the jet axis change its direction by about $21\degr$ over 27 years and jet mean intrinsic full opening angle is $\approx 0.30\degr \pm 0.03\degr$. The apparent displacement vectors of the QSC exhibit strong asymmetry and anisotropy along the jet direction, indicating pronounced anisotropic displacements of the core along the jet axis. We estimated the mean intrinsic speed of the QSC to be superluminal, $\overline{\beta_{\rm s}} \approx 15$ in units of the speed of light, which, within the framework of the seagull-on-wave model, is interpreted as evidence for a relativistic transverse wave propagating through the QSC. Analysis of the reversing trajectory of the QSC enables the classification and characterization of reversal patterns, which, in turn, allows the determination of key transverse wave parameters such as frequency, amplitude, inclination angle, and magnetic energy of the wave (abbrev.).

Context. Radio frequency molecular absorption lines appear along sight lines with AV well below 1 mag, revealing the presence of H2 in diffuse gas even when 2.6mm CO emission is absent. Aims. We discuss absorption lines of HCO+, C2H, HCN, CS, and HCO in a larger sample (88 sight lines) than was available before. Methods. We observed millimeter-wave absorption at the IRAM and ALMA interferometers over the past 30 years and gathered the results for to compare with observations of HCO+ and CO emission taken at the ARO KP12m and IRAM 30m telescopes. Results: We detected HCO+ along 72 of 86 sightlines where it was observed, C2H along 53 of 76 sightlines and HCN along 38 of 57 sightlines. C2H is ubiquitous and N(C2H)/N(HCO+) increases at smaller EB-V and smaller N(HCO+) but C2H absorption is intrinsically weaker, decreasing the number of sightlines with low column density along which it was this http URL dense-gas tracer HCN was uniformly detected down to N(H2) = 10^20 cm-2 with little change in the relative abundance N(HCN)/N(HCO+) = 1.25. HCO was detected along only 4 of 46 sight lines that were newly observed at ALMA because its lines are intrinsically weak, but HCO is ubiquitous in the interstellar medium with N(HCO)/N(HCO+) = 1/3 or N(HCO)/N(H2) = 10^-9. The line widths of HCN features are (like those of CO) narrower than those of matching features observed in HCO+, and those of C2H are broader. HCO+ emission is commonly observed at log levels -2+/-0.3 dex with respect to CO emission.

The origin of repeating Fast Radio Bursts (FRBs) is an open question, with observations suggesting that at least some are associated with old stellar populations. It has been proposed that some repeating FRBs may be produced by interactions of the binary neutron star magnetospheres decades to centuries before the coalescence. These systems would also emit centi-Hertz gravitational waves during this period, which can be detectable by space-borne gravitational wave detectors. We explore the prospects of using current and future space-borne gravitational wave detectors, such as TianQin, LISA, and DECIGO, to test this FRB formation hypothesis. Focusing on nearby galaxies like M81, which hosts a repeating FRB source in a globular cluster, we calculate the detection capabilities for binary neutron star systems. Our analysis reveals that while missions like TianQin and LISA face limitations in horizon distance, changing detector pointing direction could significantly enhance detection probabilities. Considering the chance of a Milky Way-like galaxy coincidentally containing a BNS within 100 years before merger is only $3\times10^{-5}$ to $5\times10^{-3}$, if a signal is detected originating from M81, we can establish the link between FRB and binary neutron stars with a significance level of at least 2.81$\sigma$, or a Bayes factor of $4\times10^6 - 7\times10^8$ / $5\times10^2 - 10^5$ against the background model with optimistic/realistic assumptions. Next-generation detectors such as DECIGO offer enhanced capabilities and should easily detect these systems in M81 and beyond. Our work highlights the critical role of space-borne gravitational wave missions in unraveling FRB origins.

Hycean planets -- exoplanets with substantial water ice layers, deep surface oceans, and hydrogen-rich atmospheres -- are thought to be favorable environments for life. Due to a relative paucity of atmospheric greenhouse gases, hycean planets have been thought to have wider habitable zones than Earth-like planets, extending down to a few times 0.001 au for those orbiting M dwarfs. In this Letter, we reconsider the hycean habitable zone accounting for star-planet tidal interaction. We show that for a moderately eccentric hycean planet, the surface temperature contribution from tidal heating truncates the habitable zone at significantly larger orbital radii, and that moderate eccentricity is readily obtained from any massive outer companion in the system. Though few current hycean planet candidates orbit stars of low enough mass for tides to plausibly significantly alter the extent of the habitable zone, this effect will be important to note as more such candidates are identified orbiting M dwarfs. We suggest that tides are a significant factor both for determining the extent of the hycean habitable zone around low-mass stars and for the development of a detectable hycean biosphere.

We use late Universe probes - Type Ia Supernovae from the PantheonPlus compilation, Quasars, and Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) BAO data - along with Cosmic Chronometers or Megamasers to constrain various dark energy parameterizations. These include the standard $\Lambda$CDM model ($w_0=-1,w_a=0$), as well as the Chevallier-Polarski-Linder (CPL), Barboza-Alcaniz (BA), Jassal-Bagla-Padmanabhan (JBP), Exponential (EXP), and Transitional Dark Energy (TDE) parameterizations. We find that across all parameterizations, the constrained values of $w_0$ and $w_a$ remain within $(1-2)\sigma$ of the standard $\Lambda$CDM model, irrespective of spatial curvature, dataset combinations, or prior choices. We find from Bayesian model comparison that $\Lambda$CDM remains the most favored model for both flat and non-flat cases, with results remaining robust under different priors. Across all dataset combinations, we reaffirm the fact that LRG1 and LRG2 data points from the DESI BAO dataset are responsible for driving the preference for dynamical dark energy.

Recent observations indicate that both the Milky Way bulge and inner halo exhibit angular momentum, although the origin and evolution of this prograde signature remain ambiguous. One plausible scenario involves secular evolution induced by the central bar and spiral arms. In this study, we identified a component consisting of 1,175,737 stars with net rotation through the application of a neural network (NN) method. To investigate the composition of this rotating sample and the origin of its rotation, we conducted a test particle simulation incorporating an equilibrium axisymmetric background potential together with a central decelerating bar. The test particles were generated using a distribution function (DF) model derived from observational constraints. Our results indicate that the decelerating bar transfers angular momentum to the pseudo-stars, and the rotational profile from our simulation shows strong agreement with observational data. These findings suggest that the rotating sample identified by our NN model predominantly comprises bulge, halo, and thick disk stars, and that the central decelerating bar is pivotal in shaping the inner Galaxy's kinematics through angular momentum transfer.

Recent observations presented in Cendes et al. (2024a) show that optically selected tidal disruption events (TDEs) commonly produce delayed radio emission that can peak years post-disruption. Here, we explore the multi-wavelength properties of a sample of radio-observed optically selected TDEs to shed light on the physical process(es) responsible for the late-rising radio emission. We combine new late-time X-ray observations with archival optical, UV, X-ray, and radio data to conclude that a diversity of accretion-driven outflows may power delayed radio emission in TDEs. Simultaneous X-ray data and modeling of the UV/optical emission suggest that some late radio outflows may be launched by a delayed phase of super-Eddington accretion onto the central supermassive black hole (SMBH), while others may result from a state transition to a "low-hard" radiatively inefficient accretion flow or the deceleration of an off-axis relativistic jet. We additionally find weak statistical evidence that TDEs with delayed radio emission have larger optical/UV photospheric radii than other TDEs and are less likely to exhibit helium emission lines at early times, possibly also supporting the hypothesis that the onset of SMBH accretion is delayed in these systems. Our results have implications for our understanding of state changes in SMBH accretion flows, the circularization timescale for TDE debris, and the prevalence of off-axis jets in TDEs, and motivates systematic, long-term monitoring of these unique transients. The brightest objects in our sample are also detected in the VLA Sky Survey (VLASS), demonstrating that all-sky radio surveys can play an important role in discovering unexpected radio properties of the TDE population.

In this paper, we test the cosmic distance duality relation (CDDR), as required by the Etherington reciprocity theorem, which connects the angular diameter distance and the luminosity distance via the relation \( D_{\rm L}(z) = D_{\rm A}(z)(1+z)^2 \). Our analysis is based on the latest baryon acoustic oscillation (BAO) measurements provided by the Dark Energy Survey (DES), the Baryon Oscillation Spectroscopic Survey (BOSS)/Extended BOSS (eBOSS), and the Dark Energy Spectroscopic Instrument (DESI) surveys. Specifically, an unbiased test of the CDDR is performed through a novel, model-independent method inspired by the two-point diagnostic approach, with DES-SN5YR and Pantheon type Ia supernova (SN Ia) sample reconstructed using the Artificial Neural Network (ANN) technique. This methodology effectively eliminates all nuisance parameters, including the sound horizon scale \( r_{\rm d} \) from BAO and the absolute magnitude \( M_{\rm B} \) from SN Ia. A set of \( N-1 \) independent CDDR ratios \( \eta_{ij} \) are constructed for statistical analysis. At the current observational level, no significant deviation from the CDDR is observed at low redshifts, whereas we find positive evidence ($>2\sigma$ C.L.) of deviation from the CDDR at two high redshifts ($z=2.33$ and $z=2.334$). Therefore, our results confirm that the BAO measurement provides a powerful tool to test such fundamental relation in modern cosmology.

Constraining the chemical structure of exoplanetary atmospheres is pivotal for interpreting spectroscopic data and understanding planetary evolution. Traditional retrieval methods often assume thermochemical equilibrium or free profiles, which may fail to capture disequilibrium processes like photodissociation and vertical mixing. This study leverages the TauREx 3.1 retrieval framework coupled with FRECKLL, a disequilibrium chemistry model, to address these challenges. The study aims to (1) assess the impact of disequilibrium chemistry on constraining metallicity and C/O ratios; (2) evaluate the role of refractory species (TiO and VO) in spectral retrievals; (3) explore consistency between transit and eclipse observations for temperature and chemical profiles; and (4) determine the effects of retrieval priors and data reduction methods. Ten hot-Jupiter atmospheres were reanalyzed using Hubble Space Telescope (HST) WFC3 data in eclipse and transit. The TauREx-FRECKLL model incorporated disequilibrium chemistry calculations with a Bayesian framework to infer atmospheric properties. The disequilibrium approach significantly altered retrieved metallicity and C/O ratios compared to equilibrium models, impacting planet formation insights. Retrievals reconciled transit and eclipse temperature profiles in deeper atmospheric layers but not in upper layers. Results were highly dependent on spectral resolution and retrieval priors, emphasizing limitations of HST data and the need for broader spectral coverage from instruments like JWST. This study demonstrates the feasibility and importance of incorporating disequilibrium chemistry in atmospheric retrievals, highlighting its potential for advancing our understanding of exoplanetary atmospheres with next-generation telescopes.

The Lyman-$\alpha$ photons couple the spin temperature of neutral hydrogen (HI) to the kinetic temperature during the era of cosmic dawn. During this process, they also exchange energy with the medium, heating and cooling the HI. In addition, we expect X-ray photons to heat the mostly neutral gas during this era. We solve this coupled system (Lyman-$\alpha$-HI system along with X-ray heating) for a period of 500 Myr (redshift range $8 <z < 25$). Our main results are: (a) without X-ray heating, the temperature of the gas reaches an equilibrium which is nearly independent of photon intensity and only weakly dependent on the expansion of the universe. The main determinant of the quasi-static temperature is the ratio of injected and continuum Lyman-$\alpha$ photons, (b) while X-ray photons provide an additional source of heating at initial times, for large enough Lyman-$\alpha$ photon intensity, the system tends to reach the same quasi-static temperature as expected without additional heating. This limit is reached when the density of photons close to the Lyman-$\alpha$ resonance far exceeds the HI number density, (c) we compute the global HI signal for these scenarios. In the limit of the large density of Lyman-$\alpha$ photons, the spin temperature of the hyperfine line is fixed. This freezes the global HI signal from the era of cosmic dawn and the cross-over redshift from absorption to emission. This feature depends only on the ratio of injected to continuum Lyman-$\alpha$ photons, and the global HI signal can help us determine this ratio.

We present a comprehensive temporal and spectral analysis of a few blazars using multi-wavelength observations. Rapid flux variations are quantified via the doubling/halving timescale method, revealing the shortest variability timescales of a few hours in $\gamma$-ray emissions. The broadband fractional variability is systematically computed and examined as a function of frequency, displaying a characteristic double-hump structure akin to the typical spectral energy distribution (SED) of blazars. To distinguish between different emission states, we utilize the Bayesian block algorithm, which effectively identifies distinct flux states for targeted spectral modeling. A one-zone leptonic emission framework is employed to model the broadband emission during these states. The minimum Doppler factors are estimated based on the shortest variability timescales observed in the $\gamma$-ray emissions. Under the external Compton scenario, we constrain the location of the gamma-ray emitting region and the Lorentz factor using three physical conditions: the upper limit on the jet collimation parameter, $\Gamma \theta < 1$; the upper limit on the synchrotron self-Compton contribution, $L_{\mathrm{SSC}} \lesssim L_X$; and the observational constraint on the cooling break energy, $E_{\mathrm{cool, obs}} \lesssim 100$ MeV.

We present a search for spatio-temporal clusters in 16 years of Fermi-LAT very high-energy (VHE; $E>100$ GeV) data using the DBSCAN algorithm, focusing on high Galactic latitude ($|b|>10^{\circ}$) clusters with $\geq5$ events and transient doublets (two events within $\leq 3$ days). Of 107 detected clusters, two correspond to previously unidentified VHE sources: weak BL Lacertae objects 4FGL J0039.1-2219 and 4FGL J0212.2-0219, promising targets for next-generation VHE observatories. Due to low VHE photon background, even doublets with a duration of several days exhibited high statistical significance. While most of the 114 detected doublets originated from bright TeV emitters (e.g., Mrk 421, Mrk 501), we identified six VHE flares lacking TeVCat associations. Five of these flares correlate with sources from the Third Catalog of Fermi-LAT High-Energy Sources (3FHL), while one 'orphan' flare lacks a high-energy (HE; $E > 10$ GeV) source counterpart. Some of these flares reached extreme luminosities of $\mathcal{O}(10^{47} \mathrm{erg~s^{-1}})$. No consistent temporal correlation emerged between HE and VHE activity: HE flares preceded, coincided with, or followed VHE emission across sources, with some showing no HE counterpart. Remarkably, 3FHL J0308.4+0408 (NGC 1218) is a Seyfert Type I galaxy, while no object of this class was known VHE emitter before. The 'orphan' flare without any known HE source in the vicinity may originate from NGC 5549, a low-luminosity LINER galaxy. Both sources expand the limited sample of non-blazar AGN detected at VHE energies.

An unusual orbital element clustering of Kuiper belt objects (KBOs) has been observed. The most promising dynamic solution is the presence of a giant planet in the outer Solar system, Planet Nine. However, due to its extreme distance, intensive searches in optical have not been successful. We aim to find Planet Nine in the far-infrared, where it has the peak of the black body radiation, using the most sensitive all-sky far-infrared survey to date, AKARI. In contrast to optical searches, where the energy of reflected sunlight decreases by $d^{4}$, thermal radiation in the infrared decreases with the square of the heliocentric distance $d^{2}$. We search for moving objects in the AKARI Single Scan Detection List. We select sources from a promising region suggested by an N-body simulation from Millholland and Laughlin 2017: $30^{\circ}<$ R.A. $<50^{\circ}$ and $-20^{\circ}<$ Dec. $<20^{\circ}$. Known sources are excluded by cross-matching AKARI sources with 9 optical and infrared catalogues. Furthermore, we select sources with small background strength to avoid sources in the cirrus. Since Planet Nine is stationary in a timescale of hours but moves on a monthly scale, our primary strategy is to select slowly moving objects that are stationary in 24 hours but not in six months, using multiple single scans by AKARI. The selected slowly moving AKARI sources are scrutinised for potential contamination from cosmic rays. Our analysis reveals two possible Planet Nine candidates whose positions and flux are within the theoretical prediction ranges. These candidates warrant further investigation through follow-up observations to confirm the existence and properties of Planet Nine.

Recent hydrodynamical simulations of isolated barred disc galaxies have suggested a structural change in the distribution of the interstellar medium (ISM) around a stellar mass M$_{*}$ of $10^{10}$ M$_{\odot}$. In the higher-mass regime (M$_{*} \geq 10^{10}$ M$_{\odot}$), we observe the formation of a central gas and stellar disc with a typical size of a few hundred parsecs connected through lanes to the ends of the stellar bar. In the lower-mass regime (M$_{*} < 10^{10}$ M$_{\odot}$), such an inner disc is absent and the gas component exhibits a more chaotic distribution. Observations of nearby star-forming galaxies support the existence of such a change. These inner gas discs may represent an important intermediate scale connecting the large kiloparsec-scale structures with the nuclear (sub-parsec) region, transporting gas inwards to fuel the central supermassive black hole (SMBH). For this work, we used an extended set of high-resolution hydrodynamical simulations of isolated disc galaxies with initial properties (i.e. stellar mass, gas fraction, stellar disc scale length, and the bulge mass fraction) with properties covering the range of galaxies in the PHANGS sample to investigate this change of regime. We studied the physical properties of the star-forming ISM in both stellar mass regimes and extracted a few physical tracers: the inner Lindblad resonance (ILR), the probability distribution function (PDF), the virial parameter, and the Mach number. In line with observations, we confirm a structure transition in the simulations that occurs between a stellar mass of $10^{9.5}$ and $10^{10}$ M$_{\odot}$. We show that the physical origin of this change of regime is driven by stellar feedback and its contribution relative to the underlying gravitational potential.

Photoionization by high-energy photons creates nonthermal electrons with a broad range of energies that heat and chemically transform the atmospheres of planets. The specifics of the interactions are notably different when the gas is atomic or molecular. Motivated by the idea that molecules survive to high altitudes in some exoplanets, we built a model for the energy transfer from nonthermal electrons to the H2O, H2, and O2 molecules. Our calculations show that the primary electrons of energy above about a hundred eV, a likely outcome from X-ray photoionization at moderately high atmospheric densities, expend most of their energy in ionization, dissociation, and electronic excitation collisions. In contrast, the primary electrons of less than about ten eV, such as those produced by extreme-ultraviolet photons at low densities, expend most of their energy in momentum transfer (heating), rotational, and vibrational excitation collisions. The partitioning between channels with weak thresholds is particularly sensitive to local fractional ionization. The transition between these two situations introduces a parallel transition in the way that the stellar energy is deposited in the atmosphere. Our calculations show that the nonthermal electrons enhance the ionization rate by a factor of a few or more with respect to photoionization alone but may not greatly contribute to the direct dissociation of molecules unless the local flux of far-ultraviolet photons is relatively weak. These findings highlight the importance of tracking the energy from the incident photons to the nonthermal electrons and onto the gas for problems concerned with the remote sensing and energy balance of exoplanet atmospheres.

We report the first detection of HS2 towards the cold dark cloud TMC-1. This is the first observation of a chemical species containing more than one sulphur atom in this type of sources. The astronomical observations are part of QUIJOTE, a line survey of TMC-1 in the Q band (31-50 GHz). The detection is confirmed by the observation of the fine and hyperfine components of two rotational transitions (2(0,2)-1(0,1) and 3(0,3)-2(0,2)). Assuming a rotational temperature of 7 K, we derived an HS2 column density of 5.7x10^11 cm-2, using a local thermodynamic equilibrium model that reproduces the observed spectra. The abundance of HS2 relative to H2 is 5.7x10^-11, which means that it is about seven times more abundant than its oxygenated counterpart HSO. We also explored the main formation and destruction mechanisms of HS2 using a chemical model, which reproduces the observed abundance of HS2 and indicates that dissociative recombination reactions from the ions H2S2+ and H3S2+ play a major role in forming HS2.

The stellar initial mass function (IMF) is one of the most important astrophysical distribution function, and is defined as the mass distribution for stars formed in a single star-formation event and when they just enter the main-sequence stage. The measurement of IMF is challenging even in the solar neighbourhood where IMF can be extracted by star-counting. This is because the definition of the IMF should be handled cautiously, and there are multiple corrections should be made from observation to a well-founded measurement. We present a new parametrisation of the stellar IMF in the 100-pc solar neighbourhood, leveraging the astrometric and photometric data from \textsl{Gaia} DR3: we model the colour-magnitude diagram of the field star population while accounting for observational uncertainties, Malmquist bias, Lutz-Kelker bias, the effect of varying mass-luminosity relation caused by mixture of different metallicity, and the effect of unresolved binaries. In particular, we synthesise the binaries with a process imitating the dynamical evolution observed in star clusters to model their present-day mass-ratio distribution. We derive a stellar IMF consistent with canonical IMFs but with significantly reduced uncertainties: $\alpha_1=0.81^{+0.06}_{-0.05}$, $\alpha_2=2.12^{+0.04}_{-0.04}$, and a break point at $m_{\mathrm{break}}=0.41^{+0.01}_{-0.01}$ $\mathrm{M_{\odot}}$. Our model also constrains the binary fraction to $\sim$25\% and the \textsl{Gaia} DR3 angular resolution to $1.31^{+0.24}_{-0.29}$ arcsec. We also provide the $\xi$-parameter for our IMF to be $0.5075_{-0.0051}^{+0.0112}$ for the users to compare our result with other work.

We present a radial velocity (RV) survey of the field OB and OBe stars of the SMC Wing. We use multi-epoch observations of 55 targets obtained with the Magellan IMACS and M2FS multi-object spectrographs to identify single- and double-lined spectroscopic binaries. We also use TESS light curves to identify new eclipsing binary candidates. We find that 10 each of our 34 OB (29\%) and 21 OBe (48\%) stars are confirmed binaries, and at least $\sim$ 6 more are candidates. Using our RV measurements, we set constraints on the companion masses, and in some cases, on periods, eccentricities and inclinations. The RV data suggest that OB binaries favor more circular orbits (mean eccentricity $\langle e\rangle = 0.08\pm 0.02$) while OBe binaries are eccentric ($\langle e\rangle = 0.45\pm 0.04$). We identify 2 candidate black hole binaries, [M2002] 77616, and 81941. We use BPASS to predict the frequencies of ejected OB and OBe stars and binaries, assuming OBe stars are binary mass gainers ejected by the companion supernova. We also predict the frequencies of black-hole, neutron-star, and stripped-star companions, and we model the distributions of primary and secondary masses, periods, eccentricities, and velocity distributions. The models are broadly consistent with the binary origin scenario for OBe stars, and predict an even larger number of post-supernova OB binaries. Comparison with the kinematics supports a significant contribution from dynamical ejections for both OB and OBe stars, although less so for binaries.

The Lyman-alpha forests observed in the spectra of high-redshift quasars can be used as a tracer of the cosmological matter density to study baryon acoustic oscillations (BAO) and the Alcock-Paczynski effect. Extraction of cosmological information from these studies requires modeling of the forest correlations. While the models depend most importantly on the bias parameters of the intergalactic medium (IGM), they also depend on the numbers and characteristics of high-column-density systems (HCDs) ranging from Lyman-limit systems with column densities log NHI/1cm^{-2} > 17 to damped Lyman-alpha systems (DLAs) with log NHI/1cm^{-2} > 20.2. These HCDs introduce broad damped absorption characteristic of a Voigt profile. Consequently they imprint a component on the power spectrum whose modes in the radial direction are suppressed, leading to a scale-dependent bias. Using mock data sets of known HCD content, we test a model that describes this effect in terms of the distribution of column densities of HCDs, the Fourier transforms of their Voigt profiles and the bias of the halos containing the HCDs. Our results show that this physically well-motivated model describes the effects of HCDs with an accuracy comparable to that of the ad-hoc models used in published forest analyses. We also discuss the problems of applying the model to real data, where the HCD content and their bias is uncertain.

In this study, the non-potential magnetic field parameters of active region NOAA 9077 are investigated; this AR experienced a super-strong X5.7 solar flare. Using advanced extrapolation techniques, the 3D magnetic field structure from vector magnetograms is obtained from the Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station (HSOS). Then various non-potential parameters are calculated, including current density, shear angle, quasi-separatrix layers (QSLs), twist, and field line helicity. By analyzing the spatial and temporal distributions of these parameters, we aim to shed light on the relationship between magnetic field properties and solar flare occurrence. Our findings reveal that high twist and complex magnetic field configurations are prevalent before flares, while these features tend to weaken after the eruption. Additionally, we observe decreases in helicity and free energy after the flare, while the free energy peaks approximately 1.5 days prior to the onset of the flare. Furthermore, we investigate the distribution of quasi-separatrix layers and twist, finding high degrees of complexity before flares. Multiple patterns of high current density regions suggest unstable magnetic structures prone to flaring, coinciding with shear angle distribution. Relative field line helicity patterns exhibit distinct characteristics compared to current density, concentrating before flares and diverging afterward. Overall, our results highlight the contrasting nature of current density and relative field line helicity patterns in relation to solar flares, in addition to the aforementioned feature in the set of commonly derived non-potential parameters for this particular event.

With the rapid advancement of aerospace technology and the large-scale deployment of low Earth orbit (LEO) satellite constellations, the challenges facing astronomical observations and deep space exploration have become increasingly pronounced. As a result, the demand for high-precision orbital data on space objects-along with comprehensive analyses of satellite positioning, constellation configurations, and deep space satellite dynamics-has grown more urgent. However, there remains a notable lack of publicly accessible, real-world datasets to support research in areas such as space object maneuver behavior prediction and collision risk assessment. This study seeks to address this gap by collecting and curating a representative dataset of maneuvering behavior from Starlink satellites. The dataset integrates Two-Line Element (TLE) catalog data with corresponding high-precision ephemeris data, thereby enabling a more realistic and multidimensional modeling of space object behavior. It provides valuable insights into practical deployment of maneuver detection methods and the evaluation of collision risks in increasingly congested orbital environments.

We used laser ablation to fabricate sub-wavelength structure anti-reflection coating (SWS-ARC) on a 5 cm diameter alumina lens. With an aspect ratio of 2.5, the SWS-ARC are designed to give a broad-band low reflectance response between 110 and 290 GHz. SWS shape measurements conducted on both sides of the lens give 303 $\mu$m pitch and total height between 750 and 790 $\mu$m, matching or exceeding the aspect ratio design values. Millimeter-wave transmittance measurements in a band between 140 and 260 GHz show the increase in transmittance expected with the ARC when compared to finite element analysis electromagnetic simulations. To our knowledge, this is the first demonstration of SWS-ARC on an alumina lens, opening the path for implementing the technique for larger diameter lenses.

Recent analyses from the DESI collaboration suggest that the dark energy density of the Universe may be decreasing with time, slowing the acceleration of the scale factor $a$. Typically these studies are performed assuming an ansatz for the equation of state $w(a)$. In this work, we instead consider simple models of a scalar quintessence potential with linear and quadratic behavior, which could be more representative of real models than particular parametrizations of $w(a)$. We observe a significant preference for dynamical dark energy when using supernova data from DESY5 along with DESI BAO and Planck data, at the cost of slightly exacerbating the Hubble tension. However, when using supernova data from Pantheon+ or Union3, we find only a mild preference for dynamical dark energy.

We study the acceleration and collimation of the two-sided jets in the nearby low-luminosity active galactic nucleus NGC 4261 (3C 270) using archival multifrequency, multi-epoch Very Long Baseline Array data. By applying multiple analysis methods and incorporating results from the literature, we robustly identify a parabolic-to-conical structural transition in both the jet and counterjet, with the transition occurring at $(1.23\pm0.24)\,$pc or $(8.1\pm1.6)\times10^3\,R_{\rm s}$ (Schwarzschild radii) for the jet and $(0.97\pm0.29)\,$pc or $(6.4\pm1.9)\times10^3\,R_{\rm s}$ for the counterjet. Assuming that the brightness asymmetry between the twin jets is primarily due to relativistic Doppler (de)boosting, we derive the jet velocity field at distances of $\sim (10^3-2\times10^4)\,R_{\rm s}$ based on the jet-to-counterjet brightness ratio and spectral index. Although local kinematic variations are present, the jet shows an overall acceleration to relativistic speeds from $\sim 10^3$ to $\sim8\times10^3\,R_{\rm s}$, with a maximum Lorentz factor of $\Gamma_{\rm max} \approx 2.6$. Beyond this region, the jet gradually decelerates to sub-relativistic speeds. These results support the existence of a (sub)parsec-scale ($\lesssim 1.5\,$pc) acceleration and collimation zone (ACZ) in NGC 4261, where the jet is accelerated via magnetic-to-kinetic energy conversion while being confined by external pressure. A brief comparison with M 87 suggests that the ACZ in NGC 4261 may represent a scaled-down analogue of that in M 87.

We present a structural analysis of 138 compact elliptical galaxies (cEs) in the redshift range of $z < 0.05$ using the Sloan Digital Sky Survey (SDSS) DR12 data. We perform single- and double-component Sérsic model fitting to their SDSS $r$-band surface brightness profiles. By dividing cEs into those with [cE(w)] and without [cE(w/o)] a bright host galaxy, we find a significant structural dichotomy: the majority ($\sim$85\%) of cE(w)s exhibit single-component profiles, while a similar proportion ($\sim$85\%) of isolated cE(w/o)s display double-component profiles, characterized by a compact, inner component and a diffuse, disk-like outer component. These results suggest that host-associated cE(w)s primarily form through the tidal stripping of larger progenitors, resulting in a compact bulge-like core. In contrast, isolated cE(w/o)s appear to form intrinsically at early epochs, likely through gas-rich mergers, and retain disk-like outer structures. The Sérsic index distribution of cE(w)s with single-component structure indicates progenitor types ranging from pseudo-bulge to classical bulge, supported by differences in stellar populations. A small fraction of cEs, including double-component cE(w)s and single-component cE(w/o)s, suggests complex evolutionary channels involving environmental capture or ejection. Our results emphasize that the structural characteristics of cEs, specifically the presence or absence of an extended outer envelope, serve as a crucial diagnostic tool to distinguish tidally stripped remnants from intrinsically formed low-mass cEs in isolation.

Current gravitational wave detectors are sensitive to coalescing black holes and neutron stars. However, double white dwarfs (DWDs) have long been recognized as promising sources of gravitational waves, and upcoming detectors like LISA will be able to observe these systems in abundance. DWDs are expected to be the dominant gravitational wave (GW) sources in parts of the LISA frequency range, making it crucial to understand their formation for future detections. The Milky Way contains many white dwarfs (WDs) in both the field and star clusters, promising a rich population of DWDs for LISA. However, the large number of sources may make it difficult to resolve individual binaries, and DWDs in the field and clusters often have similar properties, complicating the identification of their origins from GW signals alone. In this work, we focus on eccentric and tight DWDs, which cannot form in the field, but require dynamical interactions in dense clusters to increase their eccentricity after circularization through mass transfer phases and common-envelope evolution during binary evolution. These binaries may also form in three- and four-body dynamical interactions where a DWD binary may directly form with high eccentricity and low separation. Our results show that we should expect eccentric and tight DWDs in clusters that can provide meaningful GW signal, however, the number is low; with an upper limit of 10-15 in the MW. These can be used to independently obtain distances of their host cluster.

We present a series of parameter recovery test results of the Bayesian analysis tool IZI, which analyses emission lines from H II regions and star-forming galaxies and returns the estimates of the gas metallicity 12 + log (O/H), ionisation parameter log q, and nebular emission-line colour excess E(B-V). We created several mock datasets using IZI to represent a few different ideal or realistic datasets and performed parameter estimation on the mock data with IZI. We found that IZI underestimated or overestimated the parameters by approximately 1-$\sigma$ or greater when the model error was included, even when using all emission lines available in the model grids. We strongly recommend that IZI users run parameter recovery tests adjusted for their data before interpreting the IZI estimates. To encourage the appropriate use of IZI, we also share a script for parameter recovery tests. The cause of IZI's biased estimation is the substantial model error in the likelihood term, which varies with the model parameters. We thus note that any parameter estimation with a substantial, varying model error in the likelihood term could return biased estimates for the model parameters, such as in the case of NebulaBayes, another Bayesian analysis tool for photoionisation emission lines. We also note two issues relevant to setting the log q prior using the observed line ratio [S III]$\lambda$$\lambda$9068,9532/[S II]$\lambda$6717,6731 (the mismatch of line flux terms and violation of Bayes' theorem) and propose a way to avoid the issues.

We present a novel method combining existing cosmological simulations and orbital integration to study the hierarchical assembly of globular cluster (GC) populations in the Milky Way (MW). Our method models the growth and evolution of GC populations across various galactic environments as well as the dynamical friction and mass loss experienced by these objects. This allows us to track the trajectory of about 18,000 GCs over cosmic time in 198 MW-like galaxies from TNG50. This cosmological-scale tracking of the dynamics of in-situ and ex-situ GC populations with such a large statistical sample allows us to confirm the presence of an overlap between the two populations in MW-like galaxies, occurring below an energy threshold of $E < 0.7 E_{\rm circ}(r_{\rm hm}^{*})$ where $E_{\rm circ}(r_{\rm hm}^{*})$ is the energy of a circular orbit at the galaxy's stellar half-mass radius $r_{\rm hm}^{*}$. Our results challenge the validity of current classification schemes commonly adopted in the literature, which ultimately fail to provide a clear separation between the two populations. Instead, they tend to isolate only a subset of the ex-situ GCs. More precisely, we argue that it is highly unlikely to find in-situ clusters at $E > 0.7 E_{\rm circ}(r_{\rm hm}^{*})$, and that the real challenge lies in distinguishing the two populations below this energy threshold. In this context, we provide new predictions regarding the origins of the MW GCs observed with Gaia, as well as a comparison with existing literature. Additionally, we highlight that even if ex-situ clusters share a common origin, they inevitably lose their dynamical coherence in the $E$-$L_{z}$ space within MW-like galaxies. We observe a dispersion of GC groups as a function of $E$ and $L_{z}$, primarily driven by the evolution of the galactic potential over time and by dynamical friction, respectively.

Weak lensing has become a powerful tool for probing the matter distribution in the Universe and constraining cosmological parameters. This paper aims to explore the fast mock generation pipeline to obtain the covariance matrix of the $3\times 2$pt analysis for the upcoming China Space Station Telescope (CSST). We adopt the $N_\mathrm{side}$ pipeline, which generates matter distribution with lognormal assumptions, to create full-sky galaxy mocks with certain two-point statistics. We also employ the Markov-Chain Monte Carlo simulation to test the accuracy of the covariance matrix from the mock-generated galaxy catalogue. Our work validates the accuracy of the $3\times 2$pt statistics in both spherical harmonic space and real space. The critical scale below which the fractional error of correlation exceeds 1$\%$ can decrease as the resolution parameter $N_\mathrm{side}$ increases. After excluding certain scales, the covariance matrix from the mock-generated galaxy catalogue can constrain the cosmological parameters with 0.1$\%$ accuracy. This work demonstrates the potential of $\texttt{GLASS}$ for real-space cosmological measurements and highlights the importance of discarding appropriate scales.

Core rotation rates of red-giant stars inferred from asteroseismic observations are substantially lower than predicted by current stellar models. This indicates the lack of an efficient angular momentum transport mechanism in radiative interiors. Mixed pressure-gravity modes are a promising candidate to extract angular momentum from the core of red giants. We focus on determining the effect of mixed modes on the rotation rates of stars evolving along the red giant branch (RGB). We developed a post-processing code that computes the angular momentum transport by meridional currents, shear-induced turbulence and mixed modes. Rotation rates were computed for models along the RGB with different stellar masses and different initial rotation profiles. We find that the mixed modes can explain some of the spin down observed in red giant stars, however, the values of non-radial mode amplitudes strongly affect the efficiency of this mechanism. Rotation rates from models neglecting radiative damping on the mixed mode amplitudes overlap with observations and produce a localised spin down around the hydrogen-burning shell, whereas the inclusion of radiative damping strongly suppresses and delays this spin down. We also show that including an additional viscosity term with values in the range $10^3-10^4$ cm$^2$s$^{-1}$ redistributes the localised spin down due to the mixed modes, enhancing their efficiency. Our results reveal that the mixed mode amplitudes need to be constraint to precisely quantify the spin down of red giant cores. Nevertheless, the mixed mode mechanism by itself cannot explain the full spread in observed core rotation rates along the RGB. This will only be possible with an additional mechanism for angular momentum transport.

We examine a modified late-Universe dynamics where dark energy decays into dark matter, within the framework of metric $f(R)$-gravity in the Jordan frame. After a detailed analysis of the modified $\Lambda \text{CDM}$ model, we introduce a theoretical diagnostic tool to capture the emergence of an effective running Hubble constant as a function of redshift. We then compare this theoretical model with the 40-bin analysis of the Supernova Pantheon sample. This comparison allows us to determine the value of the additional free parameter that appears in our model, beyond those of the standard $\Lambda \text{CDM}$ model. Our modified late Universe dynamics provides a good-quality fit to the binned data, improving upon the previous phenomenological interpretation based on a power-law decay. However, unlike the power-law model, our approach cannot be extrapolated to the recombination redshift to match the Hubble constant measured by the Planck satellite. In fact, the dynamics resulting from the binned Pantheon sample analysis address only weakly the Hubble tension between the SH0ES and the Planck Collaboration values of the Hubble constant. Here we provide a convincing representation of the observed deviation of the cosmological dynamics from the $\Lambda$CDM-one, as it out-stands from the low redshift observed sources.

Recent work by Kocheril \textit{et al.}\cite{kocheril2025} claimed that phenylium--the cyclic structure of the \ce{C6H5+} species--is unreactive toward key interstellar molecules such as molecular hydrogen (\ce{H2}) and acetylene (\ce{C2H2}). This finding challenges the previously proposed role of phenylium as a cornerstone in the formation of polycyclic aromatic hydrocarbons (PAHs) \cite{cherchneff1992,byrne2024}. Here, we present new experimental and theoretical evidence that challenge this assumption. The study focused on the reactivity of \ce{C6H5+}, formed via the radiative association between \ce{C4H3+} and \ce{C2H2}, believed to be a major pathway for phenylium formation. Our results demonstrate that phenylium does indeed react with \ce{C2H2} under astrophysically relevant conditions. Quantum chemical calculations support this finding by revealing a barrierless mechanism, indicating that the reaction is feasible even in cold interstellar environments. We believe this clarification is critically important, as the conclusions of Kocheril et al. could mislead the community and hinder further investigations into the formation of the first aromatic ring in space--a process that remains a key bottleneck in our understanding of PAHs formation and growth.

We investigate the anisotropic diffusion of cosmic rays in the large-scale Galactic magnetic field, where diffusion occurs at different rates along and across the magnetic field lines. To model this process, we use stochastic differential equations to describe cosmic ray propagation and solve them numerically. The Galactic magnetic field is modeled using the Jansson-Farrar prescription. In this study, we focus on the impact of perpendicular diffusion on the residence time of cosmic rays in the Galaxy. This allows us to estimate how anisotropic diffusion influences both the residence time and the total amount of matter (grammage) traversed by a typical cosmic ray during its journey through the Galaxy.

This study examines the impact of solar modulation on the antiproton excess observed by AMS-02, which may indicate dark matter (DM) annihilation. We analyze three solar modulation models: the force-field approximation (FFA), a time-, charge-, and rigidity-dependent FFA, and a three-dimensional numerical simulation based on the Parker transport equation. Based on AMS-02 latest antiproton data (2025), our results show that the significance of the DM signal is sensitive to the chosen modulation model, with a 2$\sigma$ signal for the FFA (4$\sigma$ if including data from H, He, C, O, B/C, and B/O) and a reduced significance for more complex models. We also address systematic uncertainties using two methods: the add-in-quadrature method, which assumes uncorrelated uncertainties between energy bins, and the nuisance parameter method, which treats systematic uncertainties as nuisance parameters during the fitting process. Fitted to AMS-02 antiproton data, DM annihilation to the $b\bar{b}$ scenario with three different solar modulation models shows that the add-in-quadrature method causes overfitting, whereas the nuisance parameters approach leads to underfitting. Statistically, the signal region of the FFA model using the add-in-quadrature method is the most reliable. This work highlights the need for refined solar modulation models and a better treatment of uncertainties for a conclusive interpretation of the AMS-02 data.

We predict the non-thermal pressure (NTP) induced in the cores of galaxy clusters by kinetic jet feedback from an active galactic nucleus (AGN). We model a population of Fanaroff-Riley type I jets when sampling power-law distributions in jet power and age, which we evolve in time with a two-phase jet-lobe model. We couple the energy of each jet outburst to the surrounding gas inside spherical shells, allowing us to estimate the fraction of NTP to total pressure induced in the cluster. We predict the mean profile for this NTP fraction over the source population in a variety of cluster environments and for different AGN jet duty cycles. For typical gas and dark matter profiles, the mean NTP fraction peaks at ~4-6% when the AGN jets are active for 10-30% of the total AGN lifecycle. These predictions are in good agreement with observational constraints, suggesting that AGN feedback imparts only small non-thermal contributions to the cluster's core. Furthermore, we find a relationship between the peak in the mean NTP fraction and the AGN jet duty cycle in a given cluster environment. Applying this to Hitomi measurements of the NTP in the Perseus cluster, we infer an AGN jet duty cycle that is consistent with independent evidence of Perseus' AGN jet activity. We propose this as a novel approach for observationally inferring the past AGN activity of real clusters from their observed NTP fraction and environmental profiles.

Using a large sample of 9617 molecular clouds (MCs) from the Milky Way Imaging Scroll Painting survey, we mainly measure one-dimensional cloud-to-cloud velocity dispersions across a 450 deg$^{2}$ segment of the Local arm in the Galactic second quadrant. We define the cloud-to-cloud velocity dispersion using two metrics: the standard deviation ($\sigma_{\rm bin}$) and flux-weighted root-mean-squared value ($\sigma_{\rm bin, w}$) of the centroid velocities of $^{12}$CO-detected MCs within spatial bins. The typical values of $\sigma_{\rm bin}$ and $\sigma_{\rm bin, w}$ are 7.5$\pm$0.5 km s$^{-1}$ and 6.2$\pm$0.5 km s$^{-1}$, respectively. After categorizing clouds by sizes into three types: Type $S$ (0.15 $-$ 1.2 pc), Type $M$ (1.2 $-$ 4.8 pc), and Type L ($\gtrsim$ 4.8 pc), we find that the spatial distribution of Type $S$ and $M$ MCs projected onto the Galactic longitude-latitude (l-b) plane is generally uniform. Additionally, the cloud-to-cloud velocity dispersion among Type $S$ clouds ($\sim$ 7.6 and 7.4 km s$^{-1}$ for $\sigma_{\rm bin}$ and $\sigma_{\rm bin, w}$, respectively) is systematically greater than that among Type $M$ clouds ($\sim$ 6.7 and 6.0 km s$^{-1}$ for $\sigma_{\rm bin}$ and $\sigma_{\rm bin, w}$, respectively), with differences of 0.9 $-$ 1.4 km s$^{-1}$. From these measurements, we estimate merger timescales between MCs to be approximately 0.3 to 0.9 Myr, which is shorter than their internal crossing timescales ($\sim$ 1 Myr for Type $S$, $\sim$ 2 Myr for Type $M$, and $\gtrsim$ 5 Myr for Type $L$). This disparity, particularly pronounced for larger Type $L$ clouds, suggests that MCs are dynamically transient structures, with their gas content changing due to frequent interactions with neighboring clouds.

Here we analyse the archival data for a set of 27 Transiting Exoplanet Survey Satellite (TESS) Targets of Interest (TOIs) in search for artificially generated radio signals, or 'technosignatures', interrupted by occultation. Exoplanetary eclipses are notable events to observe in the search for technosignatures, as they mark the geometrical alignment of the target, its host star, and Earth. During an eclipse event, any signal emanating from the target of interest should cease for the duration of the eclipse, and resume after the line-of-sight has been restored. Target observations were made by Breakthrough Listen (BL) using Murriyang, the CSIRO Parkes 64-m radio telescope, coupled with the Ultra-wide Low frequency (UWL) receiver covering a continuous range of frequencies spanning 704-4032 MHz inclusive. Each target was observed in a pattern consisting of six back-to-back 5-minute source and reference sky positions for comparison during data analysis. We performed a Doppler search for narrowband signals with a minimum signal-to-noise (S/N) ratio of 10, a minimum drift rate of $\pm0.1$ Hz/s, and a maximum drift rate of $\pm4.0$ Hz/s using the turboSETI pipeline. In the analysis of 1,954,880 signals, 14,639 passed automated radio interference filters where each event was presented as a set of stacked dynamic spectra. Despite manually inspecting each diagram for a signal of interest, all events were attributed to terrestrial radio frequency interference (RFI).

The EHT collaboration released in 2019 the first horizon-scale images of a black hole accretion flow, opening a novel route for plasma physics comprehension and gravitational tests. Although the present unresolved images deeply depend on the astrophysical properties of the accreted matter, GR predicts that they contain highly lensed observables, the "photon rings", embodying the effects of strong-field gravity. Focusing on the supermassive black hole M87* and adopting a geometrically thin, equatorial disc as a phenomenological configuration for the accreting matter, our goal is to study the degeneracy of spacetime curvature and of physically-motivated emission processes on EHT-like images observed at 230 and 345 GHz. In a parametric framework, we simulate adaptively ray-traced images using GYOTO in various spherically-symmetric spacetime geometries, for a comprehensive class of disc velocities and realistic synchrotron emission profiles. We then extract the width and the peak position of 1D intensity cross sections on the direct image and the first photon ring. We show that, among the investigated quantities, the most appropriate observables to probe the geometry are the peak positions of the first photon ring. Small geometric deviations can be unequivocally detected, regardless of the motion of the disc, ranging from a Keplerian to a radially infalling one, if the black hole mass-to-distance estimate is accurate up to around 2%; the current uncertainty of 11% being sufficient just to access extreme deviations. The equatorial set-up of this paper, favoured by present EHT observations of M87*, is adapted to model future measurements at higher observing frequencies, where absorption effects are negligible, and with higher resolution, indispensable to resolve the photon rings. Additional work is needed to investigate if our conclusions hold for more realistic disc configurations.

We present a spectral-timing analysis of two NICER observations of the weakly magnetized neutron star low-mass X-ray binary Cygnus X-2. During these observations, we detect a rapid transition from a narrow 50-Hz horizontal-branch oscillation to a broad 5-Hz normal-branch oscillation, accompanied by an increase in source flux and a decrease in spectral hardness. Thanks to the large effective area of NICER, we are able to conduct a detailed comparison of the spectra associated with different types of quasi-periodic oscillations (QPOs) on short timescales. By fitting the spectra with a model that includes a disc and Comptonization components plus two emission lines, we find that the parameters of the disc component do not change significantly during the transition. However, assuming a fixed electron temperature, the optical depth of the Comptonization component decreases significantly. This drop in optical depth may be attributed to the expansion of the boundary layer or spreading this http URL addition, we find that the rms spectra for both the HBO and NBO are hard, suggesting that the boundary layer or spreading layer is driving the variability. We discuss the potential physical origin of the different types of QPOs.

Magnetar phenomena are likely intertwined with the location and structure of magnetospheric currents. While general-relativistic effects may be important in shaping the force-free equilibria describing static configurations, most studies have been restricted to axial symmetry. Using a novel methodology based on physics-informed neural networks, fully three-dimensional configurations of varying stellar compactness are constructed. Realistic profiles for surface currents, qualitatively capturing the geometry of observed hotspots, are applied as boundary conditions to deduce the amount of free energy available to fuel outburst activity. It is found that the lowest-energy solution branches permit only a $\approx 30\%$ excess relative to current-starved solutions in axisymmetric cases with global twists, regardless of compactness, reducing to $\approx 5\%$ in 3D models with localised spots. Accounting for redshift reductions to their inferred dipole moments from timing data, explaining magnetar burst energetics therefore becomes more difficult unless the field hosts non-negligible multipoles. Discussions on other aspects of magnetar phenomena are also provided.

The star NGC 3603-A1 has long been known to be a very massive binary, consisting of a pair of O2-3If*/WN5-6 stars, which show Wolf-Rayet-like emission due to their luminosities being near the Eddington limit. The system has been poorly characterized until now, due to the difficulties of obtaining reliable radial velocities from broad, blended emission lines and the extreme crowding in the cluster. However, previously unpublished archival HST/STIS spectra revealed that some of the upper Balmer lines (seen in absorption) are well separated at favorable orbital phases, prompting us to obtain our own carefully-timed new HST/STIS spectra, which we have analyzed along with the older data. Radial velocities measured from these spectra allow us to obtain an orbit for this 3.77298 day system. We also used archival STIS imaging of the cluster to obtain a more accurate light curve for this eclipsing system, which we then modeled, yielding the orbital inclination and providing values for the stellar radii and temperatures. Together, these data show that the NGC 3603-A1 system consists of a 93.3+/-11.0 Mo O3If*/WN6 primary with an effective temperature of 37,000 K, and a 70.4+/-9.3 Mo O3If*/WN5 secondary that is slightly hotter, 42,000 K. Although a more massive binary is known in the LMC, NGC 3603-A1 is the most massive binary in our own Galaxy for which a direct measurement of its mass has been made by a fundamental method. The secondary has been spun up by mass accretion from the primary, and we discuss the evolutionary status of this intriguing system.

In the last years with the increasing precision in cosmological observations we have been able to establish an standard model of cosmology, the so-called $\Lambda$CDM, but also find some tensions between cosmological probes that are difficult to explain within the context of this model. We tested several phenomenological extensions of the $\Lambda$CDM with the newest datasets from the chain CMB+BAO+SNIa, to see whether they are able to alleviate the aforementioned tensions. We find that when the updated version of the Planck CMB likelihood (PR4 LoLLiPoP and HiLLiPoP), with respect to the more used likelihoods (PR4 CamSpec and PR3), is considered, the lensing anomaly is reduced, and the preference for $A_L>1$ and $\Omega_k<0$ is less significant. From the CMB+BAO+SNIa dataset, in the context of the parameterization $w_0w_a$CDM we find a preference for a time-evoling dark energy over the rigid cosmological constant which is consistent with the most recent results from DESI collaboration.

We present the results of the spectral and timing analyses of the accreting X-ray pulsar, 2S 1417-624, during the 2018 and 2021 outbursts with Insight-HXMT. We find that the pulse profiles in all energy bands exhibit clear double-peaked structures at low flux states. In the 1-10 keV band, the pulse profiles evolve from double to triple peaks at a flux level of $\sim$4.1$\ \times \ 10^{-9}$ erg cm$^{-2}$ s$^{-1}$, and from triple to quadruple peaks at $\sim$6.4$\ \times \ 10^{-9}$ erg cm$^{-2}$ s$^{-1}$. In the 10-30 keV and 30-100 keV bands, the pulse profiles become narrower at the first transition flux level, followed by a stark transition to quadruple-peaked and triple-peaked structures around the second flux level, respectively. The change of the pulse profile {during the second transition} reveals the transition of the emission pattern from the sub-critical (pencil beam) to the supercritical (fan beam) regime. By performing the binary orbital fitting of the observed spin periods, we provide new measurements of the orbital parameters from the 2021 outburst. Applying different accretion torque models and using the critical luminosity inferred from the pulse profile transitions, we derive a self-consistent distance of {2S 1417-624} in the range of approximately 12.0-15.0~kpc, based on the magnetic field strength derived from the cyclotron resonance scattering feature (CRSF). From the estimated distance of 13 kpc and Gaia's distance of 7.4 kpc, we can infer the observed transition luminosity of \((1.0-1.4) \times 10^{38} \, \mathrm{erg \, s^{-1}}\) and \((3.0-5.0) \times 10^{37} \, \mathrm{erg \, s^{-1}}\), respectively, and compare them with theoretical models. The spectral continuum parameters and the hardness ratio also show significant transitions around the second transition, strongly supporting a change in the accretion regime.

How the large-scale kinematics of the Milky Way (MW) relate -- or even regulate -- the formation of large-to-small scale structures is incredibly hard to infer from observations. Here we investigate this interplay through a detailed analysis of a MW-like galaxy simulation, generated through the self-consistent evolution of gas, stars, and dark matter. We show that our model provides a close match to many of the MW's stellar structure and kinematic features (including in the inner Galaxy, and around the Solar neighbourhood), and find that the stellar spiral pattern in our model is very faint, with significantly less multiplicity than the sharper gaseous this http URL taken as an analogue to the MW, this finding would explain the difficulty in observational studies to agree on the number and location of our Galaxy's spiral arms. We also examine radial and tangential velocity residuals in the disc, and find that sharp kinematic transitions correlate with spiral arms, especially in the gas, where values reach $30 - 50$\,km\,s$^{-1}$. We find strong radial converging flows promoting spiral-arm growth, while diverging flows disrupt them. A time-resolved analysis of spiral-ridge segments confirms that convergence precedes density enhancements and potential star-forming conditions, while divergence leads to fragmentation and mass redistribution. These patterns evolve on relatively short timescales ($\sim10-20$\,Myr), highlighting the transient nature of spiral arms. Our model's spiral arms are dynamically driven, short-lived features shaped by evolving flows, rather than static density waves, which could explain the observed lack of contrast of cloud properties and star formation within and outside spiral arms in the MW.

The mutual inclination $\psi$ between orbits within multi-planetary systems is difficult to measure directly. Through a joint analysis of RVs, Hipparcos-Gaia absolute astrometry and relative astrometry of JWST, \citet{Bardalez2025} recently found two possible values of $\psi_{bc}={32_{-15.1}^{+13.6}}^{\circ}$ and $\psi_{bc}={145.0_{-11.1}^{+15.8}}^{\circ}$ for the nearby, non-transit planet system, 14\,Her. By incorporating additional astrometry from Gaia second data release (DR2), we have further constrained the orbital orientation of 14\,Her\,b, resulting in a definitive and unambiguous mutual inclination of $\psi_{bc}={35.3_{-7.3}^{+6.8}}^{\circ}$. The unusual misaligned orbital architecture of 14\,Her system may serve as a benchmark for dynamical studies.

Context. Very massive clusters and regions of intense star formation such as the center of our Milky Way contain young, hydrogen-burning stars very close to the Eddington Limit. Formally classified as hydrogen-rich Wolf-Rayet stars, the winds and spectra of these stars are distinctively different to the more evolved, classical Wolf-Rayet (cWR) stars. Results. We find an overall downward trend of the mass-loss rate with increasing temperature and decreasing metallicity. However, at SMC metallicities and above, we find a maximum in the wind efficiency with the mass-loss eventually decreasing again at lower temperatures. For intermediate metallicities, we also find strong discontinuities in the mass-loss trends, which do not appear at high or very low metallicities. For the lowest metallicities, a more homogeneous behavior is obtained without any maximum in the wind efficiency. The terminal velocities are generally higher for hotter temperatures. For cooler temperatures, the combined effect of metallicity and mass-loss change significantly reduces the changes in terminal velocity with metallicity. Conclusions. Contrary to cWR stars, the spectral appearance of late-type WNh stars rules out supersonic winds launched at the hot iron bump. Instead, a more extended quasi-hydrostatic regime is necessary. The proximity to the Eddington limit and the complex interactions cause a lot of substructure in the global wind parameter trends. While the strong discontinuities show resemblances to the bi-stability jump predicted for the B-supergiant regime, our models reveal a more complex origin. At sub-SMC metallicity, iron is no longer a major key for setting the mass-loss rate in this WNh regime. Instead, other elements (e.g. nitrogen) and continuum contributions become important.

Resonant Drag Instabilities (RDIs) in protoplanetary discs are driven by the aerodynamic back-reaction of dust on gas and occur when the relative dust-gas motion resonate with a wave mode intrinsic to the gas fluid. Axisymmetric models indicate that the RDI generates filamentary perturbations, leading to grain clumping and planetesimal formation. Motivated by these findings, we investigate the dust-gas interaction in a non-axisymmetric inviscid protoplanetary disc with an embedded low-mass planet ($M_{\mathrm{p}}\in[0.3, 3] M_\oplus$, here $M_\oplus$ is the Earth mass). We conduct global 3D high-resolution two-fluid simulations, with the dust being parametrized by the Stokes number $\mathrm{St}\in[0.01,0.5]$. We find that planetary waves (PWs; also known as Rossby waves), which propagate along the downstream separatrices of the horseshoe region, resonate with the streaming motion and trigger the RDI. The consequent development of a global-scale filamentary dust distribution does not sensitively depend on the Stokes number, nor does it depend on the fast dust settling that takes place in an inviscid disc. The rapid onset of this instability, which is comparable to the dynamical orbital time-scale, suppresses the formation of asymmetric structures in the dust in the vicinity of the planet (such as dust voids and filaments). Additionally, we find that the dust feedback enables buoyancy resonances in an otherwise non-buoyant (globally isothermal) disc. Therefore, our results provide the first numerical evidence of RDIs generation driven by planetary waves.

A tidal disruption event (TDE) occurs when a star travels too close to a supermassive black hole. In some cases, accretion of the disrupted material onto the black hole launches a relativistic jet. In this paper, we present a long term observing campaign to study the radio and sub-millimeter emission associated with the fifth jetted/relativistic TDE: AT2022cmc. Our campaign reveals a long lived counterpart. We fit three different models to our data: a non-thermal jet, a spherical outflow consisting of both thermal and non-thermal electrons, and a jet with thermal and non-thermal electrons. We find that the data is best described by a relativistic spherical outflow propagating into an environment with a density profile following R^-1.8. Comparison of AT2022cmc to other TDEs finds agreement in the density profile of the environment but also that AT2022cmc is twice as energetic as the other well-studied relativistic TDE Swift J1644. Our observations of AT2022cmc allow a thermal electron population to be inferred for the first time in a jetted transient providing, new insights into the microphysics of relativistic transients jets.

The creep tide theory is used to explore several aspects of the tidal evolution of the planetary system of the M-star LP 791-18 . We discuss the early synchronization of the exo-Earth LP 791-18d and show that the trapping of its rotation in a 3:2 spin-orbit resonance would only have been possible if its eccentricity were approximately 0.04 or larger. The planet is likely in synchronous rotation. The perturbations of the other planets in the system do not allow the complete damping of the orbital eccentricity, and the resulting mechanical energy balance indicates that the tidal energy dissipated inside the planet may flow through the planetary surface at approximately 1 watt per square meter.

We present new color transformations between select near-infrared filters on JWST/NIRCam, Euclid/NISP, Roman/WFI, HST, and ground-based $izY+IJHK_S$, for a total of 105 unique filter combinations. Additionally, we apply these transformations to predict the color-magnitude relation of the tip of the red giant branch as seen with JWST, Euclid, and Roman based on theoretical results for HST and 2MASS filters; for JWST we find good agreement with empirical results in the literature. We also find typical residual dispersion around these transformations of 0.01 mag for Cepheid and RR Lyrae variables and RGB stars, but up to 0.1 mag for O- and C-rich TP-AGB stars.

The gravitational $N$-body problem is a nearly universal problem in astrophysics which, despite its deceptive simplicity, still presents a significant computational challenge. For collisional systems such as dense star clusters, the need to resolve individual encounters between $N$ stars makes the direct summation of forces - with quadratic complexity - almost infeasible for systems with $N\gtrsim 10^6$ particles over many relaxation times. At the same time, the most common Monte Carlo $N$-body algorithm - that of Hénon - assumes the cluster to be spherically symmetric. This greatly limits the study of many important features of star clusters, including triaxiality, rotation, and the production of tidal debris. In this paper, we present a new hybrid code, KRIOS, that combines 3D collisionless relaxation using an adaptive self-consistent field method with a collisional dynamics part handled via Hénon's method. We demonstrate that KRIOS can accurately model the long-term evolution of clusters and provide its complete phase-space information over many relaxation times. As a test of our new code, we present detailed comparisons to two well-known results from stellar dynamics: (i) the collisional evolution of an isotropic Plummer sphere to core collapse, and (ii) the emergence of the radial-orbit instability in radially anisotropic star clusters, including its non-spherical effects.

Several supernova remnants and young neutron stars were recently discovered relatively high above the Galactic plane. One possibility is that they originate from runaway OB stars born in the Galactic disk. Understanding their origin will provide key insights into the properties of the Galactic halo. This paper aims to determine the spatial distribution of supernova explosions from runaway OB stars and to assess whether this model can explain certain observed neutron stars. We map the distribution of supernova events produced by runaway OB stars by incorporating their birth rate, initial spatial distribution, lifetime, ejection mechanisms, and velocity distributions. By tracking their motion in the Galactic potential, we determine their final distribution right before the explosion. We show that the neutron star Calvera, which is found at z around 2.2 kpc, could have originated from a runaway OB star. In addition, we compare the probabilities of finding a supernova remnant originating from Type Ia and core-collapse supernovae high above the Galactic plane, showing that supernova remnants related to core-collapse supernovae outnumber those related to Type Ia supernovae.

The possibility of discovering twin stars, two neutron stars (NSs) with the same mass but different radii, is usually studied in forward modelings by using a restricted number of NS matter equation of state (EOS) encapsulating a first-order phase transition from hadronic to quark matter (QM). Informing our likelihood function with the NS radius data from GW170817 and using a meta-model with 9-parameters capable of mimicking most NS EOSs available in the literature, we conduct a Bayesian quantification of the observability and underlying EOSs of twin stars. Of the accepted EOSs, between 12-18\% yield twin stars, depending on the restrictions we place on the twin branch. We show that many of these twin star scenarios are observable with currently available levels of accuracy in measuring NS radii. We also present the marginalized posterior probability density functions (PDFs) of every EOS parameter for each of four mass-radius correlation topologies. We find that the inferred EOS depends sensitively on not only whether twin stars are present, but also the category of twin stars, indicating that the observation of twin stars would provide a strong constraint on the underlying EOS. In particular, for two coexisting hybrid stars having QM cores at different densities, the PDF for QM speed of sound squared $c_{\rm qm}^2$ has two peaks, one below and another above the conformal limit $c_{\rm qm}^2=1/3$ predicted by perturbative QCD.

Gravitational instability (GI) is typically studied in cooling-dominated discs, often modelled using simplified prescriptions such as $\beta$-cooling. In this paper, we investigate the onset and evolution of GI in accretion discs subject to continuous mass injection, combining 1D and 3D numerical simulations. We explore an alternative self-regulation mechanism in which mass replenishment drives the system toward marginal stability $Q\sim 1$. In this regime, the disc establishes a steady-state disc-to-star mass ratio, balancing the mass transported to the central object with that added to the disc. Our 3D simulations reveal that the general scaling predicted from the linear theory are respected, however there are important difference compared to the cooling case in terms of morphology and pattern speed. Unlike the flocculent spirals seen in cooling-driven instability, the power is concentrated towards the dominant modes in infall-driven spirals. Additionally, spiral waves generate at the mass injection location, and propagate at constant pattern speed, unlike in the cooling case. This suggests a fundamental difference in how mass-regulated and cooling-regulated discs behave and transport angular momentum.

We study the CLASH sample of galaxy clusters using a new deprojection method for weak gravitational lensing observations. This method is non-parametric, allowing us to infer mass profiles, or equivalently circular velocities, without having to assume a specific halo profile. While this method assumes spherical symmetry, we show that, on average, triaxiality is unlikely to significantly affect our results. We use this method to study the total mass profiles of the CLASH clusters, as well as the relation between their total and baryonic components: (1) We find that the implied circular velocities are consistent with being approximately flat at large radii, akin to the rotation curves of galaxies. (2) We infer radially resolved baryonic mass fractions, finding that these vary significantly from cluster to cluster and depend strongly on the details of the X-ray gas mass profiles. Since the gas mass profiles are poorly constrained at large radii, it is unclear whether the CLASH clusters reach the cosmic baryon fraction expected in $\Lambda$CDM. (3) The non-parametric masses are consistent with the stellar mass--halo mass relation expected in $\Lambda$CDM; fitting parametric NFW halos to the non-parametric mass profiles gives results in overall agreement with the expected mass-concentration relation, though the concentrations are relatively poorly constrained. (4) Galaxy clusters systematically deviate from the Baryonic Tully-Fisher Relation (BTFR) and the Radial Acceleration Relation (RAR) defined by galaxies, but the magnitude of the offset depends strongly on the gas mass extrapolation at large radii. Contrary to some previous results based on hydrostatic equilibrium, we find that galaxy clusters may fall on the same BTFR and RAR as galaxies if one adds a suitable positive baryonic mass component.

Quasar outflows can play a crucial role in the evolution of their host galaxies through various feedback processes. This effect is expected to be particularly important when the universe was only 2-3 billion years old, during the period known as cosmic noon. By utilizing observations from the Dark Energy Spectroscopy Instrument (DESI), we conduct a survey of high-ionization quasar outflows at cosmic noon, with the aim of doubling the current sample of such outflows with distance and energetics determination. We also aim to compare these properties to those derived from spatially resolved outflows in similar quasars probed through Integral Field Spectroscopy (IFS). In a sample of 130 quasars we detect signatures of high-ionization outflows in the form of a S IV trough in eight objects. We characterize the physical conditions of these outflows by determining their total hydrogen column density ($N_H$), ionization parameter ($U_H$), and electron number density ($n_e$). The detected outflows show complex kinematic structures with a wide range in blueshifted velocities (100$-$4600 km s$^{-1}$). We locate five out of the eight outflows at distances between 240$-$5500 pc away from the central source. From the combined sample of 15 high-ionization S IV outflows at cosmic noon, we find a high fraction (up to 46 %) of them to be powerful enough to contribute significantly to multi-stage AGN feedback processes. Their mass outflow rates and kinetic luminosities are also found to be consistent with spatially resolved outflows in a luminosity and redshift matched sample of quasars. Comparison with previous spectra reveals interesting variations in some objects, with two cases of emerging high-velocity broad absorption line features with velocities of $-$8000 and $-$39,000 km s$^{-1}$. An impressive case of four line-locked Si IV outflow systems is also revealed in one of the objects.

Extrasolar planetary systems commonly exhibit planets on eccentric orbits, with many systems located near or within mean-motion resonances, showcasing a wide diversity of orbital architectures. Such complex systems challenge traditional secular theories, which are limited to first-order approximations in planetary masses or rely on expansions in orbital elements--eccentricities, inclinations, and semi-major axis ratios--that are subject to convergence issues, especially in highly eccentric, inclined, or tightly-packed systems. To overcome these limitations, we develop a numerical approach to second-order perturbation theory based on the Lie transform formalism. Our method avoids the need for expansions in orbital elements, ensuring broader applicability and more robust convergence. We first outline the Hamiltonian framework for the 3-body planetary problem, and apply a canonical transformation to eliminate fast angle dependencies, deriving the secular Hamiltonian up to second order in the mass ratio. We then use the fast Fourier transform algorithm to numerically simulate, in an accurate way, the long-term evolution of planetary systems near or away from mean-motion resonances. Finally, we validate our methods against well-known planetary configurations, such as the Sun-Jupiter-Saturn system, as well as to exoplanetary systems like WASP-148, TIC 279401253 and GJ 876, demonstrating the applicability of our models across a wide range of planetary configurations.

Dormant black holes (BHs) in X-ray transients can be identified by the presence of broad Ha emission lines from quiescent accretion discs. Unfortunately, short-period cataclysmic variables (CVs) can also produce broad Ha lines, especially when viewed at high inclinations, and are thus a major source of contamination. Here we compare the full width at half maximum (FWHM) and equivalent width (EW) of the Ha line in a sample of 20 quiescent BH transients and 354 CVs (305 from SDSS I to IV) with secure orbital periods (Porb) and find that: (1) FWHM and EW values decrease with Porb, and (2) for a given Porb both parameters are typically larger in BH transients than in CVs. We also compile spectral types for 17 low-mass companions in BH transients from the literature and derive an empirical Porb-Teff calibration. Using this, we conclude that the decrease in EW with Porb is mostly driven by the dilution of the Ha flux by the donor star continuum, which dominates the r-band spectrum for Porb>~0.2 d. At shorter periods, the larger contribution of the disc to the total r-band flux introduces significant scatter in the EWs due to the changing visibility of the disc projected area with binary inclination. On the other hand, the larger EWs observed in BHs can be explained by their extreme mass ratios (which limit the fractional contribution of the companion to the total flux) and the absence of a white dwarf component (important at Porb<~0.085 d). Finally, we present a tentative metric, based on Ha FWHM and EW information, and provide optimal cuts to select ~80 % of the BH X-ray transients, while rejecting ~78 % of the CVs in our sample. Such a metric, combined with other multi-frequency diagnostics, can help detect new dormant BH X-ray transients in blind large-scale surveys such as HaWKs and its pathfinder, Mini-HaWKs.

We propose a novel mechanism for gravitational wave (GW) production sourced by spectator scalar fields during inflation. These fields, while not driving cosmic expansion, generate blue-tilted isocurvature fluctuations that naturally satisfy current CMB constraints at large scales while producing enhanced power spectra at smaller scales accessible to GW detectors. The resulting GW spectrum spans an exceptionally broad frequency range from $10^{-20}$ to $1$ Hz, with amplitudes ranging from $\Omega_{\text{GW}}h^2 \sim 10^{-20}$ to $10^{-12}$ depending on the reheating temperature and spectator field mass. For heavy spectator fields with effective masses near the inflationary Hubble scale $H_I$, the mechanism produces observable signals across multiple detector bands accessible to pulsar timing arrays, space-based interferometers, and ground-based detectors. Our analysis reveals multiple complementary constraints on spectator field parameters. GW-induced limits on the effective number of relativistic species ($\Delta N_{\text{eff}}$) require $m_\chi \gtrsim 0.61 H_I$, stronger than CMB isocurvature bounds alone ($m_\chi \gtrsim 0.54 H_I$). The non-observation of primordial B-modes by \textit{Planck} provides stronger constraints $m_\chi \gtrsim 0.66 H_I$, with projected LiteBIRD sensitivity potentially reaching $m_\chi \gtrsim 0.70 H_I$. This mechanism enables a unique multi-messenger probe of beyond the Standard Model physics during inflation, providing simultaneous constraints on inflationary dynamics, dark matter production, and reheating through current and next-generation GW experiments.

We propose a new model of black hole spontaneous scalarization that combines a scalar--Gauss--Bonnet interaction with a non-minimal coupling to a $U(1)$ gauge field (a dark photon or an electromagnetic field). This construction generalizes earlier single-coupling setups and allows both curvature-induced and matter-induced scalarization within one framework, which allows us to overcome the limitations of each mechanism alone. We focus on charged, spherically symmetric black holes and demonstrate that our model substantially expands the range of black hole masses and charges that permit scalar hair. Negative Gauss--Bonnet couplings, previously associated only with near-extremal charges or rapidly spinning black holes, now trigger scalarization for much broader charge intervals. We develop a numerical procedure to solve the field equations, and investigate the various properties of these black holes. This results in new branches emerging at distinct mass thresholds, a behavior not seen in the pure Einstein--scalar--Gauss--Bonnet or Einstein--scalar--Gauss--Bonnet--Ricci models. The scalar charge depends sensitively on the coupling parameters and on the $U(1)$ charge. Our analysis also shows that these black holes have larger entropy than their Reissner--Nordström counterparts and can become overcharged, surpassing the usual extremal limit of charge-to-mass ratio. Analyzing the scalar charge behavior suggests that adding matter-coupling appears to stabilize solutions that were previously prone to higher-order instabilities in pure Gauss--Bonnet models with quadratic coupling and broadens the range of possible configurations, making this model a promising candidate for further studies in strong gravity.

Dark photons, hypothesized to be sufficiently light and/or weakly interacting, offer a compelling candidate for dark matter. Their decay into three photons, referred to as the "dark photon trident" process, becomes the dominant channel when the dark photon mass lies below the electron pair production threshold. This decay channel produces a significant flux of x-rays, presenting an opportunity for indirect detection. In this study, we analyze 16 years of x-ray data from INTEGRAL/SPI to investigate sub-MeV dark photon decay. By incorporating state-of-the-art astrophysical background modeling and accounting for the full one-loop decay amplitude, we achieve world-leading constraints on the kinetic mixing parameter for dark photon masses in the range of 61-1022 keV. These results represent a significant improvement over previous constraints, narrowing the parameter space for viable dark photon dark matter models. Furthermore, our findings highlight the potential of x-ray observatories to probe unexplored regions of parameter space and pave the way for future searches using next-generation instruments designed to detect faint astrophysical signals.

The line list for the principal isotopologue of CO calculated earlier by the present authors [1, 2] with the irregular dipole-moment function (DMF) is updated with use of the recent high-precision measurements in the 3-0 [3, 4] (Bielska et al. 2022, Hodges et al. 2025) and 7-0 [5] (Balashov et al. 2023) bands. The new data came in contradiction with the experimental data on the 1-0 band [6, 7]. Therefore, we performed fitting several model DMFs to the modified original data set of Meshkov et al. [8] by including the new above-referenced data and by excluding the data for the 1-0 band. The updated line list is calculated with the irregular DMF. In particular, excellent agreement with recent high-level ab initio calculations on the 3-0 band [3] is emphasized and predictions for the 1-0 and 8-0 bands are outlined. In the new update of the HITRAN database [9], new high-precision measurements in the cold and hot fundamental bands are announced. When these data are published, they will be compared with the predictions of our new line list.

The Einstein Telescope (ET), a planned third-generation gravitational-wave (GW) observatory, will offer significantly improved sensitivity, introducing new challenges for data analysis and computing. To prepare for these demands, the ET community has initiated a series of Mock Data Challenges (MDCs) aimed at developing and testing analysis pipelines under realistic conditions. This paper presents the first ET MDC, providing an overview of the simulated dataset and the properties of the injected GW signals, with a focus on populations of compact binary coalescences and Gaussian noise. A tutorial is also included to guide users in accessing the data and performing basic analyses. This initial challenge establishes a baseline for future MDCs and supports collaborative efforts toward the successful scientific operation of the ET.

Here, a natural non-canonical inflationary model based on a power-law Lagrangian is investigated. We analyze the scalar spectral index $n_{\rm s}$ and the tensor-to-scalar ratio $r$ of the model and identify their degeneracies with respect to the free parameters. Notably, $n_{\rm s}$ and $r$ are independent of the model parameters that leads to unresolved degeneracies. Employing the constraints on reheating parameters such as the reheating duration $N_{\rm{reh}}$, the reheating temperature $T_{\rm{reh}}$, and the equation of state parameter $\omega_{\rm{reh}}$, is found to be insufficient to fully break these degeneracies. However, the relic gravitational wave spectrum provides a way to break degeneracy with respect to the non-canonical parameter $\alpha$, degeneracy with respect to the potential parameter $f$ persist. Finally, we specify the allowed ranges for the inflationary duration $N$ and the parameter $\alpha$, in light of the latest observational data. These results highlight the role of relic gravitational waves in refining inflationary models and illustrate the challenges in fully resolving parameter degeneracies.

We explore an interacting dark matter (DM)-dark energy (DE) framework that naturally yields an effective dynamical DE equation of state crossing the phantom barrier at early times, as indicated by recent DESI data, while also accounting for the observed isotropic rotation of the cosmic microwave background (CMB) linear polarization. Within this unified framework, we also explain the DM relic abundance without introducing additional fields or couplings. Depending on the DE potential, we identify two viable scenarios: a superheavy freeze-in DM requiring a high reheating temperature, or a strongly interacting dark sector with a GeV-TeV scale thermal DM candidate.

The Atacama Cosmology Telescope (ACT) collaboration has reported a scalar spectral index $ n_s~=~0.9743~\pm~0.0034 $. This is substantially larger than the classical prediction of non-minimally coupled inflation models such as Higgs Inflation, $n_s \approx 0.965$. Here we revisit the unitarity-conserving non-minimally coupled inflation model proposed in [1]. We show that when the inflaton is a complex non-minimally coupled gauge singlet scalar with additional interactions in the Jordan frame to maintain unitarity, the model predicts $n_s = 0.9730$ and $r \approx 9 \times 10^{-6}$ for scalar self-coupling $\lambda = 0.1$.

Cosmic-rays are charged particles moving in magnetic fields. They not only emit well-known synchrotron photons but also gravitational radiation. We clarify the characteristics of the gravitational wave signal in this specific situation and underline some unexpected features. A phenomenological approximation for the radiated power is given. We derive the shape and peaking frequency of the associated stochastic backgrounds of gravitational waves for both electrons and protons, either of galactic or extra-galactic origin.

Most astrophysical systems (except for very compact objects such as, e.g., black holes and neutron stars) in our universe are characterized by shallow gravitational potentials, with dimensionless compactness parameter. While the existence and characteristic scales of such virialized systems depend on gravity, we demonstrate that the value of the compactness -- and thus the non-relativistic nature of most astrophysical objects -- arises from microphysical parameters, specifically the fine structure constant and the electron-to-proton mass ratio, and is fundamentally independent of the gravitational constant G. It then follows that large-scale astrophysical velocities and escape velocities associated with virialized systems are determined by electromagnetic and atomic physics, not by gravitation, and that the compactness is always set by microphysical scales -- even for the most compact objects, such as neutron stars, where the compactness is determined by quantities like the pion-to-proton mass ratio. This observation, largely overlooked in the literature, explains why the universe is not dominated by relativistic, compact objects and connects the low entropy of the observable universe to underlying microphysics. Our results emphasize the central but underappreciated role played by dimensionless microphysical constants in shaping the macroscopic gravitational landscape of the universe. In particular, we clarify that this independence of compactness from G applies specifically to entire, virialized, naturally formed astrophysical systems -- such as stars, galaxies, and planets -- that have reached equilibrium through self-gravity and microphysical processes. In contrast, arbitrary non-virialized subsystems (e.g., a piece cut from a planet) do not exhibit this property.