Context. The Gaia BH3 system hosts the most massive known stellar-origin black hole and a low-mass metal-poor companion whose chemical composition may help us constrain early explosive nucleosynthesis processes. Aims. We investigated the chemical abundances of the companion in order to place constraints on the formation history of this remarkable system. Methods. We performed a detailed analysis of high-resolution ESO-UVES spectra of the companion. 51 elements from lithium to uranium were investigated through spectral synthesis, including 15 treated in non-local thermodynamic equilibrium. We compared the resulting pattern to r-process-enriched stars, to nucleosynthesis models, and to stars of the ED-2 stream, from which BH3 is thought to originate. Results. The abundance pattern of the BH3 companion is consistent with that of r-I stars and is well reproduced by a combination of core-collapse supernova yields and an r-process component. The chemical patterns of four ED-2 stars closely match that of the companion, particularly after accounting for different levels of mixing of the enriched material with the ambient gas. Conclusions. The present analysis provides the most detailed chemical characterisation of a metal-poor star associated with a stellar-mass black hole. The chemical similarity with ED-2 stars argue against local pollution across the binary system. The abundances instead reflect an early spatially inhomogeneous enrichment of the progenitor cluster.
Aims. Ultra-light axions are viable fuzzy or wave-like dark matter (ψDM) candidates generically predicted by the string axiverse paradigm with multiple particle copies, whereas most of the discussions and constraints on ψDM from astronomical observations to date are based on the assumption of a single-particle copy. We aim to bridge this gap by exploring the generic multi-axion scenario motivated in the string axiverse context and investigate its astronomical implications in the linear and non-linear regimes. Methods. In the linear regime, we performed a linear density perturbation analysis to investigate the ψDM transfer functions and determined the corresponding suppression scale on the large-scale structure (LSS) in the context of the multi-copy axion. In the non-linear regime within individual galaxies, we investigated the superposition of Gaussian random fields from individual particle copies to determine the net lensing and stellar heating signatures. Results. In the linear regime, we provide a simplified prescription for obtaining multi-copy axion transfer functions, and we also identify an equivalence among all axion copies owing to the mutual coupling to the gravitational potential. As a result of this equivalence, we argue that the suppression to LSS is governed by an effective mass meff−2 = ∑iwimi−2 m eff − 2 = ∑ i w i m i − 2 $ m_{\mathrm{eff}}^{-2}=\sum_i w_i m_i^{-2} $ , with {wi} being fractional contributions of different copies to the full cosmic dark matter density. In the non-linear regime within galaxy haloes, we show that similar notions of effective mass, with expressions provided, govern the collective wave interference and hence determine the net stellar heating rates and the substructure-induced spread of James Webb Space Telescope (JWST) transients near critical curves. Distinctive to the multi-copy scenario, the effective mass governing the net surface-density perturbations within galaxy haloes is generically anticipated to vary radially. This spatial variation leads to different spreading scales for micro-lensed transients at different radial positions. This signature might be tested with future JWST lensing observations.
Context. Abell 3266 (A3266) is a dynamically active galaxy cluster embedded in a dense environment of galaxy groups and clusters at similar redshift. Data from the Spektrum Roentgen Gamma (SRG)/eROSITA all-sky survey enable us to study the large-scale emission with a low X-ray surface brightness in the outskirts of galaxy clusters. Aims. We investigate the unexplored outskirts of A3266 out to 3R100, characterize its closest neighboring galaxy group, and search for connecting filaments using X-ray emission and galaxy number density. Methods. We performed a detailed X-ray image, surface brightness, and spectral analysis in selected regions and sectors. The X-ray analysis was complemented by the distribution of member galaxies from the NASA/IPAC Extragalactic Database NED and by a comparison with the cosmological simulation Simulating the LOcal Web (SLOW). Results. An X-ray emission filament, connecting A3266 to its closest neighboring group in the northwest and extending over a 3D length of LR200−R200 = 1.1+0.5−0.1 Mpc L R 200 − R 200 = 1.1 − 0.1 + 0.5 Mpc $ L_{R_{200}{-}R_{200}} = {1.1}_{-0.1}^{+0.5}\,\mathrm{Mpc} $ , is detected with a significance of 3.6 σ. The group exhibits cool-core properties and is embedded within the filament. The filament temperature is T = 1.2−0.2+0.3 keV T = 1.2 − 0.2 + 0.3 keV $ T={1.2}_{-0.2}^{+0.3}\,\mathrm{{keV}} $ , the metallicity is Z = 0.07−0.05+0.09 Z⊙ Z = 0.07 − 0.05 + 0.09 Z ⊙ $ Z = {0.07}_{-0.05}^{+0.09}\,Z_{\odot} $ , and for a simple geometry, we derived its electron number density as ne = 8−2+1 × 10−5 cm−3 n e = 8 − 2 + 1 × 10 − 5 cm − 3 $ n_{\mathrm{e}} = {8}_{-2}^{+1}\times10^{-5}\,\mathrm{cm}^{-3} $ . Conclusions. Our findings reveal a coherent network of galaxy groups in the outskirts of A3266, tracing the ongoing assembly of the cluster along large-scale structure. The detected filament is hotter and denser than expected for the pristine warm-hot intergalactic medium, consistent with gas processed in the cluster environment and further affected by the infall of the northwest group. The comparison with SLOW shows that the observed group distribution and filamentary connections are qualitatively consistent with expectations for an actively accreting cluster embedded in a large-scale structure.
We report the first in-situ observation of magnetic reconnection within the nightside ionosphere of Mars during the disappearing solar wind (DSW) event on 26 December, 2022, a region where such processes were previously not expected. Data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission reveal that this event occurs between two open magnetic field lines. This event exhibits a complete set of reconnection signatures, which include changes in the magnetic field topology, clear Hall magnetic field reversal, ion acceleration, and sub-Alfvén outflow. Furthermore, we observed a notable similarity in the pitch angle distributions of photoelectrons and suprathermal electrons. We attribute this phenomenon to the radial expansion of the ionosphere, which caused the upward migration of ionospheric ions and neutrals. This upward movement allowed nightside ionospheric regions above the reconnection site to be illuminated by extreme ultraviolet radiation, leading to the generation of photoelectrons. These photoelectrons subsequently propagated towards the planetary surface along open magnetic field lines together with suprathermal electrons from the solar wind. This process underscores the profound reshaping of magnetosphere-ionosphere coupling dynamics that can occur under extreme solar wind conditions on Mars.
Context . Planetary magnetospheres throughout the Solar System exhibit diverse plasma environments in which ultra-low-frequency pulsations can induce nonlinear ponderomotive effects. Recent analytical studies have predicted a significant effect of the Kappa velocity distribution on the ponderomotive force (PF) induced by electromagnetic ion cyclotron (EMIC) waves. Since suprathermal populations modeled by Kappa distributions are ubiquitous in planetary magnetospheres (from Mercury to the ice giants), their effect on ponderomotive phenomena must be accounted for. Aims . We investigated the field-aligned plasma density redistribution driven by the PF of traveling EMIC waves by performing a comparative analysis in the different regimes that are characteristic of the planetary magnetospheres of our Solar System. Methods . We applied a generalized slow-timescale force balance equation to model the stationary plasma density solutions for each planetary magnetosphere. The model incorporates the PF induced by traveling EMIC waves in low-beta plasmas ( β < 1) with isotropic Kappa distributions. To enable a systematic comparison, the wave modulation is described using the Wentzel–Kramers–Brillouin approximation in a dipole magnetic field model, neglecting curvature effects to first order in planetary fields. Results . We find that the plasma response varies significantly depending on the magnetospheric parameters: a decrease in the kappa parameter and an increase in plasma beta counteract plasma accumulation towards the equator. In low-beta planetary environments, nonthermal effects significantly reduce the nonlinear response to short-period pulsations without altering the qualitative behavior predicted by Maxwellian models. We also characterized the variation in the critical parameter governing the phase transition between equatorial density minima and maxima with the specific combinations of plasma beta, the kappa parameter, and L-shell observed in the Solar System. Furthermore, applying this model to the dayside low-beta inner magnetospheres of Earth, Jupiter, and Saturn revealed that the PF exerts a substantial effect primarily during exceptionally high-amplitude EMIC wave events. Conclusions . Our analytical study demonstrates that the nonthermal properties of plasma are a governing factor in the field-aligned density redistribution driven by ultra-low-frequency waves. These results highlight the necessity of incorporating nonthermal effects to accurately model ponderomotive phenomena in the multifaceted types of planetary magnetospheres of the Solar System.
Context . Open clusters are excellent tracers of the Galactic thin disk, providing insights into its formation and evolution. Precise cluster age determination is essential for studying cluster evolution as well as the evolution of the disk as a whole. Aims . With this work, our aim was to produce an updated catalog of cluster parameters (age, extinction, distance) by constraining cluster ages via newly available spectroscopic measurements of metallicity. Methods . Using high-quality astrometry from Gaia Data Release 3, we derived new cluster memberships via a machine learning-based clustering algorithm (AstroLink). We compiled metallicity measurements from multiple ground-based spectroscopic surveys (Gaia-ESO, GALAH DR3, APOGEE-OCCAM) and Gaia GSP-Spec into a uniform scale. The ages of 320 clusters were determined using a machine learning-accelerated approximate Bayesian isochrone-fitting code (based on ASteCA), adopting a multiband approach that incorporates Gaia XP and synthetic photometry. Results . This work resulted in a robust sample of open clusters with precisely determined parameters and uncertainties. In addition, this catalog may provide a foundation for machine learning models to infer parameters for a larger sample of objects without spectroscopic data, which is to be explored in future work.
This work presents calculations of state-to-state collisional rate coefficients for the rotational excitation of the deuterated formaldehyde isotopologs, HDCO and D 2 CO, induced by collisions with molecular hydrogen, coupled with experimental verification by pressurebroadening measurements. Time-independent scattering calculations were performed using the close-coupling method to compute inelastic cross sections for collisions with both para- H 2 ( j 2 = 0) and ortho- H 2 ( j 2 = 1). These calculations are based on the H 2 CO–H 2 potential energy surface previously determined at the CCSD(T) level of theory and transformed to account for the isotopic substitution. The resulting rate coefficients cover the lowest 100 rotational states of HDCO and 60 states of ortho- and para- D 2 CO with internal energies less than 200 cm −1 . Collisional data were obtained for temperatures up to 100 K for HDCO and D 2 CO and extended up to 300 K using the coupled-states approximation. The computed rate coefficients show systematic differences between ortho- H 2 and para- H 2 collisions, with the former generally yielding larger values by a factor of 2–3. Rate coefficients for HDCO–H 2 are found to be lower by a factor of 2 to 3 compared to those of H 2 CO–H 2 and D 2 CO–H 2 . Pressure-broadening coefficients were also calculated using the random-phase approximation and compared with new laboratory measurements, yielding agreement by about 5–30%.
Context . The Fornax cluster, the second-nearest rich galaxy cluster, constitutes a suitable laboratory to explore the evolution of galaxies in a dense environment. Recently, the Southern Photometric Local Universe Survey (S-PLUS) has obtained unprecedented photometric information on Fornax, which reveals new features regarding its galaxy populations and surrounding regions. In this context, simulations are invaluable tools to interpret the past, present, and outcome of such observational findings. Aims . We aim to deliver a robust photometric catalog of simulated Fornax-like systems in a cosmological context to consistently contrast them with S-PLUS data. Such a comparison will lead to our long-term goal: to trace the origin of Fornax galaxy populations and their environment. Methods . We analyzed Fornax analogs from the EAGLE and ILLUSTRISTNG simulations that were selected using the observed properties of the Fornax cluster and its central galaxy NGC 1399. For each system, we generated synthetic photometry in the 12 S-PLUS bands using the SKIRT radiative transfer code, with the instrumental configuration of the S-PLUS survey. Simulated data cubes, mock images, spectral energy distributions, magnitudes, and colors were obtained for each galaxy in our selected simulated Fornax analogs. Results . The synthetic photometry and spectra derived from simulations show good agreement with the S-PLUS observations, especially in the case of the central galaxy NGC 1399. We identify particular systems that show some similarity with the spatial distribution of galaxies in Fornax. Such simulated candidates reproduce the observed color–magnitude relation and the spatial substructure between the cluster core and the Fornax A region. Also, simulated galaxies are bluer at higher cluster-centric distances, in agreement with observations. Although modest discrepancies were obtained between the observed and simulated color–magnitude diagrams in some cases, our results support the suitability of our selection criteria and synthetic photometry, and the reliability of current cosmological simulations to reproduce key general features of the Fornax cluster.
Binary stars are key tracers of the dynamical evolution of star clusters and provide important constraints on stellar populations and mass functions. The Magellanic Clouds host clusters with a wide range of ages and masses, offering an ideal laboratory to investigate these properties in regimes poorly sampled in the Milky Way. We aim to characterize the binary populations, mass functions (MFs), blue straggler (BS) content, and structural parameters of intermediate-age Magellanic Cloud clusters, and to explore their dependence on global cluster properties. We analyzed high-precision Hubble Space Telescope photometry for 16 clusters obtained with ACS/WFC and WFC3/UVIS. Structural parameters were derived from stellar density profiles. Binary fractions were measured using the binary map technique, focusing on systems with mass ratios q > 0.7. We derived MFs accounting for unresolved binaries and identified candidate BS populations from color-magnitude diagrams. The fraction of binaries with q > 0.7 ranges from 5% in NGC2121 up to 13% in NGC 2173, with a mass-ratio distribution that is consistent with being flat on average. By combining our results with literature data, we confirm a clear anticorrelation between the core binary fraction and cluster mass, while no significant dependence on cluster age is found. The clusters follow the established relation between age and core radius, although with substantial scatter at fixed age. Within the narrow age range explored here, clusters exhibiting steeper MFs are found to have smaller core radii. We find no evidence of a correlation between the fractions of binaries and BS fractions. These findings are consistent with a scenario in which dynamical evolution plays a primary role in the formation of binary populations. The connection between MF slope and structural parameters provides new constraints on cluster evolution and suggests a link between MF slope and structural evolution.
Context . Old, metal-poor stars are perfect tracers of the formation of the Milky Way. The combination of chemical and kinematic investigations into them provides an insight into accretion episodes in the past history of our Galaxy. Aims . We present here a detailed chemical abundance analysis of 16 metal-poor stars, selected from the RAVE survey, which are characterised by a high radial velocity. Methods . We derived stellar parameters from Gaia photometry and parallaxes. Using high-resolution spectra obtained with UVES at the ESO-VLT, we determined elemental abundances for α -, iron-peak, and neutron-capture elements using the M Y GI S FOS pipeline. Departures from local thermodynamic equilibrium, where available, were investigated. We used the SPInS bayesian inference pipeline to derive ages for all the stars. Actions and other dynamical quantities were computed using the galpy pipeline applying the Galactic potential MWPotential2014, in order to classify the stars kinematically. Results . The stars span a wide metallicity range (−1.2 ≲ [Fe/H] ≲ −2.9) and exhibit kinematic properties consistent with the outer halo population. Star C0213360–505024, [Fe/H]=−1.4, appears to have an age of 1.3 Gyr and a mass of 1.6 M ⊙ . Based also on its kinematics and line broadening, which we attribute to stellar rotation, we argue that this star is young and not an evolved blue straggler. The available evidence points towards an accreted origin for this star and we speculate about its possible progenitor. The other 15 stars have ages compatible with an old population.
Context . Orion is the closest region hosting active star formation and young OBA stars. Accurately determining the far-ultraviolet (FUV) flux at its stellar population is essential to connect stellar and protoplanetary disc properties to the environment. Aims . We (1) accurately estimated the FUV flux and its distribution at a numerous stellar population of Orion by statistically accounting for the uncertainty in parallax measurements, and (2) investigated the relation between stellar accretion and external FUV radiation field by comparing observations and disc evolution models. Methods . We selected a large stellar population in Orion (within a 6° radius of the Orion Nebula Cluster core), assigned sub-cluster memberships, and used the two-dimensional sub-cluster geometry to infer three-dimensional separations from OBA stars and compute the FUV flux (and its uncertainty) at each stellar position. We studied the accretion luminosities ( L acc ) inferred from H α emission in Gaia XP spectra of Orion sources and determined their detection fraction as a function of age and FUV flux. We compared the results with population synthesis models of viscous discs experiencing external photoevaporation. Results . We provided a publicly available table of FUV fluxes at ~8600 stars in Orion. Most of this stellar population is weakly FUV irradiated, <10 2 G 0 , ~ 35% is intermediately irradiated, 10 2 –10 4 G 0 , and only ~5% has FUV fluxes >10 4 G 0 . Gaia -based L acc decreases with age, and H α detection fraction declines more rapidly in regions with strong FUV fluxes (≳10 2 G 0 ) than in regions exposed to weaker FUV fluxes (≲10 2 G 0 ), broadly consistent with the model. This result may suggest that external photoevaporation efficiently depletes strongly FUV irradiated accretion discs, but it is not sufficient to reliably confirm this conclusion. Conclusions . The tools we provided for accurately computing FUV fluxes at the Orion stellar population will be essential for targeting sources in future observations aimed at assessing the role of external photoevaporation on protoplanetary disc. Our study highlights the need for additional measurements of stellar and disc properties across the Orion population, covering the FUV flux range 1–10 5 G 0 .
Context. The formation pathways of sulfur-bearing species in the interstellar medium (ISM) are crucial for our understanding of astrochemical processes in cold molecular clouds and gaining new insights into the sulfur budget in these regions. Aims. We aim to explore the recently detected thioethanal (CH3CHS) formation mechanisms from thioethanol (CH3CH2SH) as a precursor, in addition to secondary sulfur products. Methods. We employed electronic structure methods and density functional theory for both gas-phase and ice-grain surface environments. To mimic interstellar ice-mantles, we used both medium (W6) and large amorphous (W22) water clusters, as implemented in Binding Energy Evaluation Platform (BEEP). Results. We identified a formation mechanism that is effectively barrierless with respect to the reactant asymptote for CH3CHS, which remains kinetically feasible under low-temperature interstellar conditions, in the gas phase. Surface environments modulate activation barriers in a site-specific manner, elucidated through both Langmuir-Hinshelwood and Eley-Rideal initiated surface reaction pathways. Compared to oxygen analogs, sulfur chemistry enables alternate pathways due to weaker S–H bonding, with a competing route forming ethane-1,1-di-thiol (CH3CH(SH)SH) on the ice-grain surface, potentially reducing CH3CHS yields. The first accurate binding energy for thioethanol on water ice is also reported here, confirming its greater volatility in comparison to ethanol. Conclusions. The proposed mechanism offers a tentative hypothesis for the apparent mutual exclusive detections of CH3CH2SH and CH3 CHS in TMC-1, Orion, and Sgr B2(N), which requires further validation through quantitative astrochemical modeling and also to distinguish this chemical differentiation from observational sensitivity limitations. These qualitative findings highlight the multifaceted chemical behavior of sulfur-bearing organics in the ISM and support CH3CH(SH)SH as a promising astrochemical target.
Galaxy formation models predict that galaxies grow inside-out, becoming larger over time. While observations broadly support this paradigm, the nature and timescales of this growth remain poorly constrained. We report the discovery of an extremely faint and young (∼600 Myr) stellar component in the outer regions of the nearby galaxy Messier 74 (M74). Using deep optical imaging from the TST telescope at the Teide Observatory, reaching surface brightness limits of ∼30-31.5 mag arcsec−2 in the g, r, and i bands, we detect stellar emission extending well beyond the previously known disc radius of ∼14 kpc. This newly identified component reaches galactocentric distances of ∼30 kpc, effectively doubling the known size of the stellar disc and matching the extent of the HI disc. The revised size of M74 places it in the upper envelope of the mass–size relations. The young age of the outer stellar population suggests a recent episode of disc growth, potentially occurring on timescales shorter than ∼1 Gyr. We discuss a possible scenario in which a past flyby interaction with UGC 1176 may have triggered this extended star formation. Further studies of galaxies with similarly deep imaging will be key to determining whether such rapid outer disc growth is common or exceptional.
Context.γ2 Velorum is the closest and visually brightest Wolf-Rayet (WR) binary system. Its eccentric orbit modulates the X-rays observed from the wind-wind interaction, and its large separation enables spatial resolution of both components. Aims. We aim to strengthen the constraints on the properties of γ2 Velorum and, in particular, to resolve the discrepancy between the eccentricity determined from the emission lines and that from the absorption lines. Methods. We obtained VLT/GRAVITY observations and combined them with earlier spatially resolved data covering different orbital phases. Results. We determine strong constraints on all orbital parameters and find that e = 0.322, close to the value derived from the emission lines. The X-ray light curve declines as s−3 after periastron, where s is the separation of the two stars, but its modulation is likely affected by absorption and occultation of the X-ray emitting region at other orbital phases. We find that previous discrepancies in the reddening value can be traced to a brighter K-band magnitude than predicted by the WR wind models. We derive E(B − V) = 0.02 ± 0.02 mag. Our more precise mass and radius values, combined with previously determined effective temperatures, provide strong constraints on evolutionary models. The closest match for the O star comes from a rotationally mixed model with initial mass Minit = 28.7 M⊙ and an Minit = 32 M⊙ model for the WR star, with negligible accretion onto the O star during the WR progenitor’s Roche lobe overflow phase. However, the temperature of the O star is higher and the mass of the WR star is smaller than predicted by the evolutionary tracks at the current epoch, consistent with the well-known “mass-discrepancy problem” in massive stars. Conclusions.γ2 Velorum’s strongly constrained parameters make it ideal for testing structure, evolution, and stellar wind models.
Context. Diffuse γ-ray emission from cosmic-ray (CR) protons scattering off the gas in the intracluster and intergalactic medium remains out of reach for current observations. Detecting this emission would provide constraints on the nonthermal pressure support by CR protons in these environments. Aims. We provide estimates for diffuse γ-ray emission in the Fermi-LAT band from galaxy clusters and the cosmic web in the local Universe. Methods. In this work, we show results from the first cosmological magnetohydrodynamic simulation with an on-the-fly spectral CR model. We modeled CR injection at shocks, accounted for adiabatic energy changes and advection of CR protons, and obtained their γ-ray emissivity directly from the simulated CR energy density and spectra. To do this, we used constrained initial conditions that evolved in a field closely resembling that of the local Universe, allowing a direct comparison to Fermi-LAT data on massive clusters. Results. We find CR proton acceleration at all structure formation and accretion shocks in galaxy clusters and cosmic web filaments. These protons provide the basis for diffuse γ-ray emission in these regimes. The absolute value of the diffuse γ-ray emission in our simulation lies a few orders of magnitude below the current upper limits found by Fermi-LAT. Under the assumption of our model, a sensitivity of Fγ < 10−11γ s−1 cm−2 would be required for a detection of diffuse emission in Coma. This provides a lower limit for diffuse emission from CR protons accelerated at structure formation shocks.
Context. Solar active regions are the source of virtually all significant space weather events. It is therefore important to characterize the relationship between their observable properties and flare production. Aims. The flare productivity of solar active regions is analyzed across solar cycles 23–25 as a function of magnetic complexity, sunspot area, and solar-cycle phase. Additionally, the power-law index of the peak flux frequency distribution is estimated. Methods. The GOES soft X-ray event reports matched with daily Solar Region Summaries were used to create a robust active region catalog. This catalog was supplemented with the 50-year HEK flare catalog and the newly released STIX flare catalog from Solar Orbiter to estimate the power-law index. Results. Magnetically complex active regions (βγ, βδ, and βγδ) produce the majority of M- and X-class flares while comprising only ∼13% of all daily active-region observations, showing that larger flares disproportionately occur in larger area sunspots. The peak flux frequency distribution of all three catalogs can be represented with a consistent power-law index of α = 2.02 ± 0.01. However, a class-by-class analysis of the C/X and M/X flare ratios reveals that the distribution steepens significantly toward higher energies. We fit this steepening as a lognormal tail and extrapolated two decades beyond the X-class threshold, which yielded a recurrence time of 370−159+292 yr for an X100-class (“Carrington-type”) superflare, compared to only ∼26 yr from a naive single power-law extrapolation. Conclusions. While α ≈ 2 provides a useful global description of the flare frequency distribution, the steepening area-productivity relation and the divergence between the derived C/X and M/X slopes both point to a deficit of the most energetic flares relative to a single power-law extrapolation. This implies that extreme events such as Carrington-type flares are considerably rarer than a fixed power law would predict. Our extrapolated recurrence time is in much closer agreement with independent literature estimates.
Exoplanet reflection spectra contain a wealth of information, which we are now beginning to access. At a high spectral resolution, the rotation of both the star and the planet affects the shape of the reflected spectral lines. This effect must be accounted for in high-resolution analyses and could be used to measure the orbital alignment of systems. In this work, we derive the rotational broadening kernels for arbitrarily aligned systems, both for the stellar spectrum viewed by the planet and for the reflected component of the planet's spectrum. We then determine the relation between the parameters of the kernels and the standard orbital parameters of an exoplanet system. Finally, we show examples of these kernels, compare them with previous models, and investigate the limitations imposed by our assumptions. We find that the difference in the rotational broadening of a non-aligned system relative to the broadening expected from a prograde aligned orbit can be of the order of 50 km s^-1. We also highlight how the equations and kernels presented in this work could be modified for other uses, such as thermal emission spectra.
GG Tau A is a young triple system consisting of the close pair, Ab_1--Ab_2, and a third component, Aa, surrounded by a massive circumtriple disk whose large inner cavity is difficult to explain in a purely binary framework. Recent astrometric studies have constrained the inner and wide orbits separately. However, only a joint treatment can provide a self-consistent description of the system and constrain the individual stellar masses. We aim to determine the orbital architecture and individual stellar masses of GG Tau A and assess how the available astrometric and disk-based constraints restrict the range of admissible solutions. We performed a joint fit using , developed specifically for hierarchical stellar systems. All astrometric measurements were placed in a common reference frame, since the historical wide-orbit astrometry is given relative to the unresolved photocenter of the Ab subsystem. The fit included one new wide-orbit astrometric epoch and a prior on the total stellar mass derived from disk kinematics. We then applied, in post-processing, an additional geometrical constraint based on the observed center of the circumtriple disk. Oracle The fit yields orbital solutions compatible with the available astrometric and disk-based constraints and provides estimates of the individual stellar masses. The additional wide-orbit epoch only marginally reduces the range of admissible solutions. By contrast, the disk-center constraint leaves the favored orbital architectures largely unchanged but significantly tightens the stellar-mass partition. This yields posterior masses of 0.521^ +0.069 _ -0.051 , 0.106^ +0.017 _ -0.013 , and 0.79^ +0.10 _ -0.10 M_⊙ for Ab_1, Ab_2, and Aa, respectively. The reported values are posterior medians with 16th--84th percentile intervals. A joint treatment of the two orbital levels is required to recover a physically meaningful architecture and constrain the individual stellar masses. The resulting solutions provide a basis for future dynamical modeling of the circumtriple disk and for testing whether the observed cavity can further constrain the system architecture.
The SPHERE High-contrast Imaging survey for Exoplanets (SHINE) represents one of the largest and most sensitive direct imaging campaigns conducted to date with the VLT, targeting over 400 young, nearby stars with the goal of detecting and characterizing giant exoplanets and brown dwarfs. This extensive dataset offers a unique opportunity to revisit observations using modern, data-driven approaches, potentially uncovering new substellar candidates that may have been overlooked by classical analysis techniques. In this context, our study focuses on reprocessing and re-analysing the so-called F150 sample, a well-defined subset of 150 main-sequence stars within 100 pc observed in the H band with VLT/SPHERE as part of the SHINE survey. We applied , a supervised deep learning model specifically tailored for detecting faint planetary signals in angular differential imaging (ADI) sequences. Designed to model local noise properties by capturing spatio-temporal correlations, produces network-confidence detection maps that push the detection of faint companions closer to the noise floor than classical S/N-based approaches. To translate the model's pixel-wise confidence maps into actionable detections, we introduced a novel thresholding strategy that selects, for each annulus, the confidence threshold maximizing the F_1 score (the harmonic mean of precision and recall) from injection-recovery experiments. This principled approach balances sensitivity and specificity, addressing a key limitation in current deep learning-based methods. NA-SODINN NA-SODINN NA-SODINN recovers all known companions and some of the debris disks in the F150 sample, and it identifies 13 new substellar candidates not reported in previous studies: ten detected in both the H2 and H3 bands, and three in only one band. For the ten sources detected in both bands, we used the H2--H3 colour–magnitude diagram to perform a first assessment of their nature. Based on this analysis, we identified two ambiguous cases and three photometrically promising candidates. However, in light of the currently available multi-epoch SPHERE data, only the candidate around Smethells 20 remains a strong target for follow-up.
We aim to investigate how galaxy interactions affect the incidence and strength of nuclear activity in active galactic nucleus (AGN) host galaxies. We also aim to determine the roles played by projected separation, dual activation, and the mass (luminosity) ratio between interacting companions. We combined AGN hosts from SDSS DR7 with a large catalog of galaxy pairs identified in SDSS and Galaxy Zoo DECaLS. Physical pairs were selected using projected separation (r_p < 100 kpc h -1 $) and radial velocity difference (Δ V < 350 km s$^ -1 ). Nuclear activity was traced using attenuation-corrected O iii luminosity, while control samples matched in redshift, stellar mass, luminosity, concentration index, and local density were constructed for comparison. In addition, we classified interactions into major and minor mergers based on luminosity ratios. We find that AGNs in interacting pairs exhibit enhanced nuclear activity compared to isolated AGN, with a systematic increase in O iii luminosity toward smaller projected separations. This enhancement is strongest for close pairs (r_p < 25 kpc h -1 $). Systems hosting two AGNs show higher O iii luminosities than single-AGN pairs, particularly at small separations. Major mergers display significantly higher mean O iii luminosities than minor mergers. It is only these interactions that show a clear rise in activity toward small $r_p values. The AGN luminosity is positively correlated with the luminosity of the companion galaxy, and only weakly with its color. Our results indicate that interactions enhance AGN activity primarily in regimes of close proximity and when the companion is of a comparable or moderate mass. Minor mergers exhibit a scarce influence on nuclear activity, suggesting that only sufficiently strong tidal perturbations efficiently channel gas to the central engine.
