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New parameters for star-cluster dynamics: Observational results
No full textWe recently used a large set of Monte Carlo simulations of globular clusters (GCs) to define new, fully empirical parameters (named A_5, P_5, and S_2.5) able to trace the internal dynamical evolution of dense stellar systems. These parameters are specifically designed to quantify the steepness of the cumulative radial distribution of stars in the innermost region of the host system, which tends to progressively increase with dynamical aging due to core contraction. Following the original definitions, here we measure A_5 and P_5 in a sample of 40 Galactic GCs homogeneously surveyed through HST photometric observations. In agreement with the predictions of our simulations, the largest values of A_5 and P_5 are found for the most dynamically evolved GCs --i.e., those previously classified as post-core-collapse systems based on the shape of their density profile-- and those characterized by the shortest central relaxation times. Moreover, the new dynamical parameters here measured strongly correlate with A^+_rh, another fully empirical, independent parameter that traces the dynamical age of star clusters through the level of central segregation of blue straggler stars
The gas-phase nitridation processes of large, astronomically relevant polycyclic aromatic hydrocarbons cations in the interstellar medium
No full textAtomic nitrogen reacts efficiently with polycyclic aromatic hydrocarbons species, and potentially generates a diverse array of complex organic molecules in the interstellar medium. In this work, the gas-phase chemical evolution of large, astronomically relevant PAH, tetra-benzo-pero-pyrene (TBPP, C_36H_16) cations under N-atom bombardment is investigated experimentally and theoretically. A series of nitridated TBPP cations, including C_36H_16N_n +^+). We investigated the structures and the vibrational infrared spectra of newly formed nitridated TBPP cations and the bonding energy for the reaction pathways using theoretical calculations, which were based on density functional theory with the hybrid density functional B3LYP/6-311++G(d, p). The reaction energy is relatively high, which indicates that the addition of N atoms to the carbon skeleton is a random and independent event, i.e., there is no carbon-edge structural effect. Furthermore, theoretical analyses confirm that denitridation pathways involving the loss of CN or HCN/HNC units are energetically favorable, which underscores their potential role in the top-down evolution of large PAHs. The obtained results highlight the importance of PAH cations evolution under N-atom bombardment, and demonstrate the formation of complex organic species containing nitrogen functionalities, such as C=N, C–N–H, and C–N–C groups. Furthermore, these findings provide insights into the molecular diversity and chemical evolution of PAHs, where ion-atom collisions drive both the functionalization and structural truncation of large molecules in astrophysical environments
Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts
No full textWe report the confirmation of three transiting exoplanets orbiting , (LSPM J0902+7138), (G 2--21), and (Wolf 346) that were initially detected by through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of 4.65, 5.88, and 2.59 days, and they orbit early-M dwarfs (M2.0,V, M1.5,V, and M3.0,V, respectively). We were able to precisely determine the radius of all three planets with a precision of , the mass of with a precision of 19, %, and upper mass limits for and The radius of is 2.33 _ , its mass is 7.7 ± 1.5, , and the mean density is 0.61 ± 0.15 , M_⊕ The radius of is 1.77 ^ +0.09 -0.08 R_⊕ , the 3 , and the 3 . The third planet, _ upper mass limit is 4.9 , M_⊕ upper density limit is 0.88, ̊ho_⊕ is Earth-sized with a radius of 0.99 ^ +0.07 -0.06 , R_⊕ , a 3 ,and a 3 . While upper mass limit of 2.2 , M_⊕ upper density limit of 2.2, ̊ho_⊕ is most probably rocky, given its Earth-like radius, and are located in a highly degenerate region in the mass-radius space. appears to lean toward a water-world composition. has enough mass to host a significant H-He envelope, although a water-world and pure rocky compositions are also consistent with the data. Our analysis indicates that future atmospheric observations using JWST can aid in determining their real composition. The sample of small planets around M dwarfs is widely used to understand planet formation and composition theories, and our study adds three planets to this sample
Detecting gravitational lensing by matter currents
No full textWe explored the observational prospects for detecting gravitational lensing induced by cosmological matter currents, a relativistic correction to the standard density lensing effect arising from the motion of matter. We propose isolating this contribution by cross-correlating the weak-lensing convergence field with a reconstructed cosmic momentum field inferred from galaxy redshift surveys. Using numerical simulations, we demonstrate that this reconstructed momentum field is uncorrelated with the density lensing signal, enabling a clean separation of the gravitomagnetic component. We then forecast the detectability of this signal for upcoming wide-field galaxy and weak-lensing surveys, showing that a statistically significant detection may be achievable under realistic observational conditions. Such a measurement would provide the first direct probe of the large-scale cosmic momentum field, offering a novel test of general relativity and Lorentz invariance on cosmological scales
Consistent tidal and rotational models for satellites in synchronous rotation
No full textTidal dissipation in natural satellites plays a crucial role in shaping their thermal state, internal structure, and evolution; for example, sustaining subsurface oceans in Europa and Enceladus and driving Io’s volcanic activity. The amount of dissipation can be inferred from secular orbital drift and gravity variations induces by tides, which can be measured through astrometric observations and spacecraft radiometric data. We examine a discrepancy in the literature regarding the semimajor axis evolution due to tides in synchronously rotating satellites, whereby predictions from the variation of orbital elements approach (using direct tidal accelerations) differ by nearly a factor of three from the classical energetic method. This discrepancy may introduce systematic biases in dissipation estimates of the same order. We identify the source of this inconsistency as the effect of tidal dissipation on the moon’s rotation, which induces an offset of the prime meridian. In classical synchronous rotation models, the prime meridian always points to the empty focus of the orbit, but once this offset is properly accounted for we recover an agreement with the energetic method. We then extend our analysis to include the main physical libration at the orbital period. Additionally, we compare the time-lag and complex Love number tidal models from an orbital evolution perspective, finding unexpected differences and proposing a formula to reconcile the two models. Finally, we observe that a nonzero static S_2,2 gravity coefficient of a moon, considering the classical synchronous rotation as mentioned above, produces a variation in energy and angular momentum, suggesting that it must be constrained with dissipation parameters to avoid biases
Transit distances and compositions of low-velocity exocomets in the beta Pic system
No full textBeta Pictoris is a young nearby A5V star, about 20 Myr old, that is embedded in a prominent debris disc. For the past 40 years, variable absorption features, produced by the gaseous tails of exocomets transiting the star, have been observed in the stellar spectrum. Yet, despite the large number of observations available, the origin and dynamical evolution of the exocomets remain poorly understood. Here we present new spectroscopic observations of Space Telescope and the High Accuracy Radial Velocity Planet Searcher. We report the detection of three strong exocomet signatures at low radial velocities (-7.5, and km/s) from a large set of lines from various species and excitation levels. We show that the three exocometary tails have different excitation states, indicating that they are located at different distances from the star. Using a detailed modelling of the excitation state of the transiting gas, which includes both radiative and collisional excitation, we derived the transit distance of the three exocometary gaseous tails to be 0.88 ± 0.08,, 4.7 ± 0.3,, and 1.52 ± 0.15,au. These values are much larger than previous estimates, which generally placed the transient features within 0.2,au. This reveals that gaseous tails produced by exocomets sublimating close to the star can expand and migrate over large distances while still remaining detectable in absorption spectroscopy. Our study provides a new method for measuring the transit distance of exocomets based on excitation modelling; this complements the acceleration method, which is only applicable to high-velocity objects. obtained on April 29, 2025, with the Hubbl
How a close-in planet protects its white dwarf host from pollution
No full textApproximately 25–50% of the white dwarfs (WDs) exhibit metal absorption lines in their photospheres. The lines are attributed to accretion from their remnant planetary systems. Although WDs with detected planetary systems are more likely to show photospheric pollution, one notable exception, WD 1856+534, hosts a close-in giant planet, but exhibits no detectable photospheric metal pollution. Previous studies have proposed that massive close-in planets can block the inward transport of small particles driven by radiative forces (e.g., Poynting–Robertson drag and the Yarkovsky effect). It remains unclear, however, whether the close-in planet can similarly prevent the delivery of larger bodies via dynamical interactions.
We aim to quantify the protective effect of close-in planets on WD pollution by asteroids that approach on near-parabolic orbits and to explore the planetary masses and orbital separations required to provide an effective protection.
We performed ensembles of short-term N-body integrations that sampled a range of planet masses and orbital separations and initialized asteroids on highly eccentric orbits with periapses near the WD Roche radius in order to measure scattering, capture, and ejection outcomes and to quantify the planet’s shielding efficiency.
For WD1856+534b-like configurations (a_p=0.02 au), giant planets with masses greater than 0.5 Jupiter masses are sufficient to clear over 80% of the highly eccentric small-body contaminants. The effectiveness of the protective effect diminishes with decreasing planetary mass and increasing semimajor axis. These findings help us to explain why some WDs that host close-in giant planets do not show the photospheric metal pollution commonly observed in other systems
Cepheid Metallicity in the Leavitt Law (C--MetaLL) survey. IX. Metallicity dependence of period-Wesenheit relations based on a homogeneous spectroscopic sample
No full textThe C-MetaLL project has provided homogeneous spectroscopic abundances of 290 Classical Cepheids (DCEPs) for which we have the intensity-averaged magnitudes in multiple optical and NIR bands, periods, pulsation modes, and Gaia parallaxes corrected for individual zero-point (ZP) biases.
Our goal is to derive updated period--Wesenheit--metallicity (PWZ) relations using the largest and most homogeneous metallicity sample ever used for such analyses, covering a range of -1.3< Fe/H dex, and to assess the metallicity dependence of these relations.
We computed several optical and NIR Wesenheit magnitudes adopting both Cardelli et al. and Fitzpatrick reddening laws, and transformed Johnson-Cousins Wesenheit magnitudes into their HST equivalents using empirical relations. Using 275 DCEPs with reliable parallaxes, we applied a robust photometric parallax technique, which simultaneously fits all parameters -- including the global ZP counter-correction to parallaxes -- and handles outliers via a Cauchy likelihood to account for the sample's excess variance. Gaia
We find a stronger metallicity dependence (γ ≈ -0.5 mag/dex in optical, -0.4 mag/dex in NIR) than recent literature reports. Gaia parallax ZP counter-correction (ε) varies moderately across bands, with an average value of ∼10 μas, aligning with previous determinations. Applying our PWZ relations to ∼4500 LMC Cepheids yields distances generally consistent within 1σ with geometric estimates. The choice of reddening law has a small impact, while using only fundamental-mode pulsators significantly increases the uncertainties. Including α element corrections increases and reduces ε. However, we find 1σ consistency γ values with the literature, particularly for the Wesenheit magnitude in the HST bands, by restricting the sample to brighter (i.e. closer) objects, or by including only pulsators with -0.7< Fe/H or a non-linear dependence on metallicity of DCEP luminosities at the metal-poor end, which is difficult to quantify with the precision of parallaxes of the present dataset
The effect of gravitational stratification on kink oscillations in curved coronal loops
No full textKink oscillation frequency is a key parameter for coronal seismology. It is still unclear how gravitational stratification affects the kink frequency in curved coronal loops.
This work aims to investigate the effect of gravitational stratification on the frequency of kink oscillations in curved coronal loops and discuss their seismological potential.
We conducted numerical computations within the ideal magnetohydrodynamic framework to study different kink polarizations and harmonics in a curved, gravitationally stratified coronal loop. The oscillation frequencies derived from the Lagrangian displacement were compared with the Wentzel-Kramers-Brillouin (WKB) approximation.
For the vertically polarized fundamental mode, the oscillation frequency deviates from the WKB approximation by about 18% in the current numerical setup . Nevertheless, the oscillation frequency closely matches the local Alfvén frequency near the loop apex. On the other hand, the frequency of the horizontally polarized fundamental mode exhibits only a 7% deviation in our current model from the WKB approximation and closely matches the local Alfvén frequency near one quarter of the loop. For the first overtones, the frequencies for both polarizations can be well described by the WKB approximation.
The frequency of vertically polarized fundamental kink modes can be predicted by the local Alfvén frequency near the loop apex. In contrast, the WKB approximation remains highly reliable for estimating the frequency of horizontally polarized fundamental modes and first overtones, which is also well described by the local Alfvén frequency near one quarter of the loop. These results therefore pave the way for spatially dependent coronal seismology, enabling, for example, the probing of magnetic field strength at different locations along a coronal loop
Photocatalytic Degradation of Malachite Green in Simulated Textile Dyeing Wastewater Using Fe
No full textMalachite Green (MG) is a triphenylmethane-based textile dye that is toxic and difficult to degrade. Various methods for textile wastewater treatment contaiing textile dyes have been developed, one of which involves using composites based on magnetite (Fe₃O₄) coated with silica (SiO₂) and ZnO as a photocatalyst. This study aims to synthesize and characterize the Fe₃O₄/SiO₂/ZnO composite, test its ability to reduce MG concentration in a textile wastewater simulator, and evaluate the reusability of the composite. FTIR spectra showed absorption peaks at 651.94 cm⁻1 and 941.26 cm⁻1, corresponding to Zn-O and Si-O-Zn bonds, confirming the presence of ZnO and SiO₂ in the synthesized composite. The XRD diffractogram showed diffraction patterns consistent with Fe₃O₄/SiO₂/ZnO, with diffraction peaks observed at 31.89°, 34.53°, 36.25°, 47.65°, 57.45°, and 67.85°, measured at 2θ angles. SEM-EDX analysis identified the presence of Fe, O, Si, and Zn elements, the average of composite particle size is 67.636 nm. Performance tests for MG removal demonstrated that the Fe₃O₄/SiO₂/ZnO composite effectively reduced MG concentration of textile waste simulated sample, under UV irradiation at 366 nm for 8 hours, with a removal capacity of 0.5084 mg MG/g composite. Reusability tests showed that in the first cycle, the composite reduced MG concentration by 0.4880 mg/g, while in the second and third cycles, the removal capacities were 0.4863 mg/g and 0.4809 mg/g, respectively. The synthesized Fe₃O₄/SiO₂/ZnO composite successfully degraded Malachite Green (MG) in the textile wastewater simulation under UV 366 nm irradiation. The composite was able to degrade MG over multiple reuse cycles, the performance decline is 2