446494 research outputs found
Sort by
The Modular Computational Simulation Interface (MoCSI) code
No full textContext. With many different missions to small bodies and (icy) moons currently ongoing or on the horizon, modern thermophysical models for planetary science need to be able to be adapted to quickly changing parameters and science objectives.
Aims. We aim to develop the public and open-source Modular Computational Simulation Interface (MoCS
The intermediate neutron capture process
No full textContext. The intermediate neutron-capture process (i-process) can occur during proton ingestion events (PIEs), which may take place in the early evolutionary phases of asymptotic giant branch (AGB) stars.
Aims. We investigate the impact of rotational and magnetic mixing on i-process nucleosynthesis in low-metallicity, low-mass AGB stars.
Methods. We computed AGB models with [Fe/H] = −2.5 and −1.7 and initial masses of 1 and 1.5 M⊙ using the STAREVOL code, including a network of 1160 nuclei coupled to transport equations. Rotating models incorporate a calibrated Tayler-Spruit (TS) dynamo to account for core rotation rates inferred from asteroseismic observations of solar-metallicity sub-giants and giants. Initial rotation velocities of 0, 30, and 90 km s−1 were considered, along with varying assumptions for magnetic mixing.
Results. Rotation without magnetic fields strongly suppresses the i-process due to the production of primary 14N, which is subsequently converted into 22Ne – a potent neutron poison during the PIE. Including magnetic fields via the TS dynamo restores the models close to their non-rotating counterparts: strong core-envelope coupling suppresses shear mixing and prevents primary 14N synthesis, yielding i-process nucleosynthesis similar to non-rotating models. We also find that rotational mixing during the AGB phase is insufficient to affect the occurrence of PIEs.
Conclusions. Proton ingestion event-driven nucleosynthesis proceeds similarly in asteroseismic-calibrated magnetic rotating AGB stars and non-rotating stars, producing identical abundance patterns
Perceptual effects of modified late reverberation and reverberation time in auditory augmented reality in two rooms
No full textThis paper presents two experiments investigating perceptual tolerances regarding deviations in the late reverberation of a room in augmented reality (AR) audio rendering. The study is based on binaural room impulse responses (BRIRs) measured with a KEMAR head-and-torso-simulator in two seminar rooms with reverberation times (RTs) of about 0.4s and 1.1s. We implemented an algorithm to modify the RT while maintaining the spectral profile of the room’s reverberation. In a single stimulus listening test design, participants had to rate externalization, audiovisual plausibility, and room perception for different RT scalings. Differentiating between audiovisual plausibility for source and room helped capture the different perceptual phenomena. In this context, the concept of room acoustic signature preservation has also been proposed. The results indicate that in the reverberant room, RT deviations of 0.1s already reveal that
the acoustics of the room are different. However, plausible illusions in AR can be maintained despite significant perceptible deviations in RT, considering the original early room response. For originally short RT, audiovisual source plausibility is even robust towards larger RT modifications
Luminous fast blue optical transients as very massive star core-collapse events
No full textContext. Luminous fast blue optical transients (LFBOTs) are rare extragalactic events of unknown origin. Tidal disruption events (TDEs) involving white dwarfs by intermediate mass black holes (BHs), mergers of BHs and Wolf-Rayet (WR) stars, and failed supernovae (SNe) are among the proposed explanations.
Aims. In this paper, we explore the viability of very massive star core-collapse (CC) events as the origin of LFBOTs. The appeal of such a model is that the formation of massive BHs via CC events could yield observational signatures that can match the disparate lines of evidence that point towards both CC and TDE origins for LFBOTs.
Methods. We explored the formation rate of massive BHs in binary population synthesis models and compared the metallicities of their progenitors with the observed metallicities of LFBOT host galaxies. We further examined the composition, mass-loss rates, and fallback masses of these stars, placing them in the context of LFBOT observations.
Results. We determined the formation rate of BHs with masses greater than ∼30–40 M⊙ to be similar to the observed LFBOT rate. The stars producing these BHs are biased towards a low metallicity (Z < 0.3 Z⊙) and they are H- and He-poor, with dense circumstellar media. However, some LFBOTs have host galaxies with higher metallicities than predicted and they typically have denser local environments (plausibly due to late stage mass loss not captured in the models). We find that long-lived emission from an accretion disc (as implicated in the prototypical LFBOT AT 2018cow) can only be produced in these events under maximal disc mass and angular momentum conditions.
Conclusions. We conclude that a (very) massive star CC scenario is a plausible explanation for at least some LFBOTs, but it still faces challenges. The preferred progenitors for LFBOTs in the failed SN interpretation overlap with those predicted to produce super-kilonovae (super-KNe). We therefore suggest that LFBOTs are promising targets in the search for super-KNe and that they could offer a non-negligible contribution to the r-process enrichment of galaxies
Origin of asteroid (469219) Kamo‘oalewa: The main asteroid belt or the Giordano Bruno crater on the Moon?
No full textContext. Asteroid (469219) Kamo‘oalewa is the target of the Tianwen-2 sample-return mission by the China National Space Administration. Because of its orbit and its peculiar spectral properties, it was proposed that Kamo‘oalewa originated from the Moon as impact ejecta, possibly from the Giordano Bruno crater.
Aims. We aim to estimate the relative contribution of Kamo‘oalewa-like objects originating from the general near-Earth asteroid (NEA) population, which originated in the main asteroid belt, and compare it with the relative contribution of Giordano Bruno ejecta.
Methods. We first estimated the average fraction of quasi-satellite orbits in the Earth co-orbital space at any given time using numerical simulations. Using recently developed NEA population models, we extracted the expected number of Earth co-orbitals of the same size of Kamo‘oalewa, and we obtain an estimate of the average number of Kamo‘oalewa-like objects using the fraction computed before. Similarly, we obtain an estimate for the number of Kamo‘oalewa-like objects that may originate as ejecta from the Giordano Bruno impact. We also performed simulations for the Catalina Sky Survey, Pan-STARRS, and Vera Rubin Observatory to estimate their efficiency in the detection of Kamo‘oalewa-like objects.
Results. Numerical simulations showed that 1.39% of the orbits in the Earth co-orbital space are quasi-satellite, on average. When combined with the expected number of Earth co-orbitals in the same size range as Kamo‘oalewa from the NEA population models, we found that the main belt accounts for 1.23 ± 0.13 Kamo‘oalewa-like objects on average. The expected number of Kamo‘oalewa-like objects originated as Giordano Bruno ejecta is 0.042, which is more than an order of magnitude smaller. On the other hand, we found a discovery efficiency of Earth quasi-satellites between 95% and 70% for an absolute magnitude between 22 and 25 for the Pan-STARRS survey, and population models show that this is in agreement with the known population of Earth quasi-satellites. The Vera Rubin Observatory should reach a discovery efficiency of 92% down to absolute magnitude of 25.
Conclusions. Quantitative estimates show that population models of NEAs based on the migration of objects from the main belt are capable of accounting for Kamo‘oalewa-like objects. This relative contribution supports the hypothesis that (469219) Kamo‘oalewa originated from the main belt, which will be further investigated by future observations and in situ exploration of the Tianwen-2 spacecraft
Exploring the formation mechanisms of tidal structures in globular clusters of extragalactic origin
No full textTidal structures around globular clusters provide valuable insights into cluster evolution and the hierarchical assembly of the Milky Way. Using wide-field imaging data from the DESI Legacy Survey combined with a color-magnitude matched-filter technique, we performed a systematic analysis of extratidal features in 28 Galactic globular clusters of likely extragalactic origin, representing the largest homogeneous sample examined in this context to date. The clusters display diverse morphologies: 12 exhibit tidal tails, nine show diffuse envelopes, and seven reveal no clear extratidal features. Notably, we report the first detection of an extended tidal structure around the Sagittarius-associated cluster Terzan 7. To explore the underlying drivers, we compared intrinsic properties, orbital dynamics, and possible accretion associations across morphological groups. From the parameter distributions, complemented by Kolmogorov-Smirnov tests, we find that total mass, escape velocity, concentration, tidal filling factor, pericentric radius, eccentricity, and radial angle in action-angle coordinates are all likely group-sensitive parameters. These results suggest that both internal cluster properties and orbital configurations play important roles in shaping extratidal morphologies. In addition, the cluster’s accretion history shows no clear correlation with the presence of tidal features, indicating that it is not a direct driver of outer structure formation. Overall, the diversity of tidal structures is unlikely to be governed by a single factor. Instead, it reflects the interplay between internal dynamical evolution and the external Galactic environment. This study provides the most comprehensive constraints so far on the physical processes driving extratidal structures in accreted globular clusters
Four-band flexible metamaterial absorber based on multi-layer square metal rings
No full textThis study proposes a flexible metamaterial absorber based on multi-layer square closed metal rings and PDMS (polydimethylsiloxane). This absorber uses PDMS as the support base and adopts a multi-layer metal ring stacking structure made of stretchable silver conductive ink to achieve four significant absorption peaks in the 0–0.6 THz frequency band, with peak all exceeding 90%. Its absorption mechanism stems from the LC resonance excited by adjacent metal rings and the metal ohmic loss. The intact metal layer at the bottom can reduce the transmittance to nearly zero. Parametric studies show that period, metal ring line width and thickness have regulatory effects on the frequency and intensity of absorption peaks: an increase in period mainly reduces the intensity of high-frequency absorption peaks, an increase in line width causes the absorption peaks to shift blue, and an increase in thickness leads to a decrease in peak values and the merging of low-frequency peaks. This absorber features excellent stretchability, maintaining an absorption peak of over 90%. Moreover, within the incident angle range of 0–70°, the absorption peaks in both TE and TM modes exceed 90%. This design combines flexibility, wide-angle stability and efficient multi-frequency absorption performance, providing potential application prospects for fields such as flexible electronics, wearable technology and terahertz imaging
A catalog to unite them all: REGALADE, a revised galaxy compilation for the advanced detector era
No full textContext. Many applications in transient science, gravitational wave follow-up, and galaxy population studies require all-sky galaxy catalogs with reliable distances, extents, and stellar masses. However, existing catalogs often lack completeness beyond ~100 Mpc, suffer from stellar contamination, or do not provide homogeneous stellar mass estimates and size information.
Aims. Our goal is to build a high-purity, high-completeness, all-sky galaxy catalog out to 2000 Mpc, specifically designed to support time-domain and multi-messenger astrophysics.
Methods. We combined major galaxy catalogs and deep imaging surveys – including the Legacy Surveys, Pan-STARRS, DELVE, and SDSS – and added spectroscopic, photometric, and redshift-independent distances. We cleaned the sample using the Gaia catalog to remove stars and visually inspected all ambiguous cases below 100 Mpc through a classification platform that gathered 27 000 expert votes. Stellar masses were estimated using optical and mid-infrared profile-fit photometry, and we improved the accuracy of photometric distances by combining multiple independent estimates.
Results. The resulting catalog, REGALADE, includes nearly 80 million galaxies with distances under 2000 Mpc. It provides stellar masses for 88% of the sample and ellipse fits for 80%. REGALADE is more than 90% complete for galaxies contributing 50% of the total r-band luminosity out to 360 Mpc. In science tests, it recovers 60% more known supernova hosts, doubles the number of low-luminosity transient hosts, and identifies more reliable hosts for ultraluminous and hyper-luminous X-ray sources.
Conclusions. REGALADE is one of the most complete and reliable all-sky galaxy catalog to date for the nearby Universe, built for real-world applications in transient and multi-messenger astrophysics. The full dataset, visual classifications, and code will be released to support broad community use
Comfort zones of stars: A limit on orbital tightening via stable mass transfer shapes the properties of binary black hole mergers
No full textMass transfer in binary systems is the key process in the formation of various classes of objects, including merging binary black holes (BBHs) and neutron stars. The orbital evolution that occurs during mass transfer depends on how much mass is accreted and how much angular momentum is lost – two of the main uncertainties in binary evolution. This poses a challenge for obtaining reliable predictions from binary channels. Here, we demonstrate that despite these unknowns, a fundamental limit exists to how close binary systems can become via stable mass transfer (SMT) that is robust against uncertainties in orbital evolution. Based on detailed evolutionary models of interacting systems with a BH accretor and a massive-star companion, we show that the post-interaction orbit is always wider than ∼10 R⊙, even when extreme shrinkage due to L2 outflows is assumed. Systems evolving toward tighter orbits become dynamically unstable and result in stellar mergers. This separation limit has direct implications for the properties of BBH mergers, including long delay times (≳1 Gyr) and an absence of high BH spins from the tidal spin-up of helium stars. At high metallicity, the SMT channel may be severely quenched due to Wolf-Rayet winds. We predict BBH mergers from ∼10 M⊙ to 90 M⊙, with case A mass transfer dominating above 40 M⊙. The reason for the separation limit lies in the stellar structure, not in binary physics. If the orbit becomes too narrow during mass transfer, a dynamical instability is triggered by a rapid expansion of the remaining donor envelope due to its near-flat entropy profile. The closest separations can be achieved from core-He burning (∼8−15 R⊙) and Main Sequence donors (∼15−30 R⊙), while Hertzsprung gap donors lead to wider orbits (≳30−50 R⊙) and non-merging BBHs. These outcomes and mass transfer stability are determined by the entropy structures, which are governed by internal composition profiles. Consequently, the formation of BBH mergers and other compact binaries via SMT is a sensitive probe of chemical mixing in stars, and it may help address open questions of stellar astrophysics, such as the blue supergiant problem. Finally, we propose a new simplified treatment of mass transfer stability that more accurately reproduces detailed results and remains flexible under varying assumptions for orbital evolution
Adaptation in shifting and size-changing environments under selection
No full textWe propose a model to characterize how a diffusing population adapts under a time periodic selection, while its environment undergoes shifts and size changes, leading to significant differences with classical results on fixed domains. After studying the underlying periodic parabolic principal eigenelements, we address the {\it extinction vs. persistence} issue, taking into account the interplay between the moving habitat and periodic selection. Subsequently, we employ a space-time finite element approach, establish the well-posedness of the approximation scheme, and conduct numerical simulations to explore these dynamics.
p, li { white-space: pre-wrap;