bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and fabrication of intermetallic NiCo electrocatalysts for the alkaline HER
Authors: Wu Chun , Wang Xuhui , Huang Mengyao , Meng Chao , Chang Ling , Xu Dake , Pei Wenli
Published: July 2024

The intermetallic L10-NiCo electrocatalysts play a crucial role in reducing energy consumption, improving hydrogen production rates, and prolonging the service life of alkaline electrolyzers.
Visible light induced palladium-catalyzed Suzuki–Miyaura cross-coupling of glycosyl chlorides to form C-aryl glycosides
Authors: Lai Jinsheng , Zhang Yufeng , Zhan Ying , Zhou Zhuoyi , Wang Zhen , Liu Hui , Zhang Qingju , Sun Jian-Song , Wang Liming
Published: July 2024

A powerful method is developed utilizing excited-state palladium-catalyzed Suzuki–Miyaura reaction to synthesize C-aryl glycosides. It can be applied to a wide range of aryl and heteroaryl boronic ester substrates as well as glycosyl chlorides.
Correction: Structure formation of PNIPAM microgels in foams and foam films
Authors: Kühnhammer Matthias , Gräff Kevin , Loran Edwin , Soltwedel Olaf , Löhmann Oliver , Frielinghaus Henrich , von Klitzing Regine
Published: July 2024

Correction for ‘Structure formation of PNIPAM microgels in foams and foam films’ by Matthias Kühnhammer et al., Soft Matter, 2022, 18, 9249–9262, https://doi.org/10.1039/D2SM01021F.
A mixed-valent nonanuclear [Mn5IIMn4III] molecular cluster with cubic topology of highest symmetry as a bifunctional electrocatalyst for efficient water splitting
Authors: Sarkar Chandan , Sarkar Tapan , De Aditi , Dutta Nityananda , Kłak Julia , Oliver Allen G. , Tiwari Ranjay K. , Behera J. N. , Kundu Subrata , Bera Manindranath
Published: July 2024

A mixed-valent nonanuclear molecular cluster [Mn9L4(μ2-O)4(μ3-Cl)2] with cubic topology has been explored as a bifunctional electrocatalyst for efficient water splitting that produces molecular H2 and O2.
An amphiphilic interface for constructing a uniform composite solid-state electrolyte towards long-life all-solid-state sodium metal batteries
Authors: Peng Chengyuan , Huang Shizhi , Shen Xuyang , Ding Jingyi , Luo Junrong , Du Junhao , Xia Zongpu , Zhang Xinxiang , Chen Jitao
Published: July 2024

A polydopamine amphiphilic compatibility layer was applied to meliorate filler dispersion, and enhance the electrochemical performance and stability of all-solid-state sodium metal batteries.
Substrate-free growth of N-doped bamboo tube morphology on CoNi alloy nanoparticles as an electrocatalyst for anion exchange membrane fuel cells
Authors: U. Anil Kumar , Dhavale Vishal M.
Published: July 2024

The beneficial role of the CoNi-alloy for the formation of N-doped bamboo knotted tube morphology via the tip-in growth mechanism as a Pt-free cathode electrocatalyst for anion exchange membrane fuel cells.
Carbon nanosheet-supported CrN nanoparticles as efficient and robust oxygen reduction electrocatalysts in acidic media and seawater Zn–air batteries
Authors: Zhang Yating , Wu Haoming , Ma Jun , Luo Junming , Lu Zhe , Feng Suyang , Deng Yijie , Chen Hui , Wang Qi , Miao Zhengpei , Rao Peng , Yu Neng , Yuan Yuliang , Li Jing , Tian Xinlong
Published: July 2024

Carbon nanosheet-supported CrN nanoparticles render excellent ORR activity in acidic media and long-term stability in natural seawater Zn–air batteries.
Magnetic MOF composites for the electrocatalysis and biosensing of dopamine released from living cells
Authors: Guo Jiarong , Ma Ying , Han Tongyu , Yang Jiao , Miao Peng
Published: July 2024

We have synthesized novel magnetic metal–organic frameworks as electrocatalysts and constructed a novel biosensor for electrochemical detection of dopamine released from living cells.
Finite‐time consensus for variable‐order fractional non‐linear multi‐agent systems under actuator faults and external disturbances
Authors: Nazemorroaya Ehsan , Shafieirad Mohsen , Hashemi Mahnaz
Published: July 2024

The present investigation aims to address the leader‐following consensus issue for variable‐order fractional multi‐agent systems (VOFMASs) under actuator faults and unknown external disturbances. The Caputo definition for the variable‐order fractional (VOF) derivative is used to model the non‐linear dynamics of the leader and follower agents. Consequently, two lemmas are developed for the Caputo VOF derivative of the Lyapunov function. In the first case, it is assumed that the multi‐agent system (MAS) operates without actuator faults and an adaptive controller is proposed. With the aid of the developed lemmas, assurance is provided for the finite‐time bounded cooperative tracking of the VOFMAS despite the presence of unknown external disturbances. In the second case, a novel fault‐tolerant controller is designed for the finite‐time consensus of the MAS under two common kinds of actuator faults: loss of effectiveness fault and bias fault. Finally, the efficacy of the proposed controller is demonstrated through the presentation of results from three simulation examples.
2D sectorial dipole‐enabled planar endfire circularly polarized antenna with widened azimuth half‐power beamwidth
Authors: Gu Shan‐Shan , Lu Wen‐Jun , Zhu Lei
Published: July 2024

This letter proposes a novel planar endfire circularly polarized antenna with widened half‐power beamwidth. Widened azimuth beamwidth mechanism of 2D sectorial electric dipole is theoretically revealed, thus it is able to combine with a rectangular magnetic dipole to yield a half‐power beamwidth widened planar endfire circularly polarized antenna. Finally, a prototype planar endfire circularly polarized antenna with sectorial flared angle of α = 270° is fabricated, simulated, and implemented to validate the design approach. As investigated, the antenna exhibits broadened azimuth half‐power beamwidth of 150° over a frequency range of 2.40–2.45 GHz.
The Retinex enhancement algorithm for low‐light intensity image based on improved illumination map
Authors: Weng Ruidi , Zhang Ya , Wu Hanyang , Wang Weiyong , Wang Dongyun
Published: July 2024

Taken in low‐light intensity conditions, image with low brightness affects processing precision. In this article, the Gamma Function based on the brightness average and weighted fusion method according to gray entropy is proposed, which is combined with the improved Retinex algorithm. First, the maximum values of R, G, and B channels in original image are extracted to generate the primary illumination map. Second, the illumination map is optimized and adjusted via the Gamma correction function based on the average brightness value. Finally, the illumination map and detail layer are fused by a weighted fusion algorithm of gray entropy to obtain the reflection map. Reflection maps are used as enhancement. The algorithm proposed in this article can improve the brightness and maintain light distribution in the original image with higher precision and less color distortion.
Research on image saliency detection based on deep neural network
Authors: Qiu Linrun , Zhang Dongbo , Hu Yingkun
Published: July 2024

As a hot research field at present, computer vision is devoted to the rapid acquisition and application of target information from images or videos by simulating human visual mechanism. In order to improve the accuracy and efficiency of image detection, image saliency region detection technology has received more and more attention in the field of computer vision research; an important research content in the field, the core part of which lies in the research on algorithms related to feature extraction and saliency calculation of targets. This paper analyzes the multi‐feature fusion saliency detection model and visual saliency calculation process, and based on the existing algorithm, by improving the VGG16 network, a fully convolutional network saliency detection algorithm is proposed. The qualitative and quantitative experimental results show that compared with the four mainstream methods of BL, GS, SF, and RFCN, our algorithm not only improves the accuracy of salient object detection, but also effectively solves the problem of target edge blur. Therefore, this study has improved the accuracy and efficiency of saliency detection, which can not only promote the development of computer vision technology, but also provide support for research in the field of image processing.
An unsupervised coherent receiver digital signal processing algorithm based on spectral clustering with no data preamble
Authors: He Jianhua , Zhan Yueying , Pan Haoyuan , Peng Hui
Published: July 2024

A coherent optical receiver digital signal processing (DSP) scheme is proposed based on spectral clustering, which utilises spectral clustering to cluster the signals outputted by the DSP. Compared to existing blind DSP algorithms for coherent optical receivers operating at over 100Gbps with PM‐mQAM, the proposed scheme effectively suppresses various physical impairments, achieving lower bit error rates (BERs) at the same transmission distance, thus enabling longer transmission distances under the same forward error correction threshold. Furthermore, simulations of the proposed scheme on a 14GBaud PM‐16QAM coherent optical transmission system show that, at a BER of 1.9E‐2, the maximum transmission distance increases from 1700 to 2000 km, and at a BER of 3.8E‐3, it increases from 700 to 900 km.
Optimal robust sizing of distributed energy storage considering power quality management
Authors: Zhu Ying , Wei Juan , Wang Bozhong , Hong Shiyu , Liu Yutong , Lu Liang
Published: July 2024

This paper proposes an optimal robust sizing model for distributed energy storage systems (DESSs) considering power quality management. The power conversion systems (PCSs) of DESSs with four‐quadrant operation characteristics can provide power quality management services to customers. To improve capacity utilization of the DESS, power quality management services are quantified and integrated into an optimal bi‐level sizing model, where the upper level addresses the sizing problem concerning battery and PCS capacities, while the lower level focuses on coordinating active/reactive power control of the DESS. A robust optimization approach for DESS scheduling is adopted to consider uncertainties of distributed photovoltaic (PV) power generation and power quality management requirements. The column and constraint generation (C&CG) algorithm is applied for efficient handling of this model. Ultimately, the effectiveness of the proposed approach is validated through comprehensive comparative analysis of four cases, resulting in a 12.44% increase in the net present value (NPV) over the entire lifecycle.
Development of intelligent traction walking plate for tension overhead construction
Authors: Li Xiaobin , Li Ye , Wang Feng , Huang Zhiming , Yao Pan , Li Baoguo
Published: July 2024

In the process of tension wire construction of transmission lines, the key state quantities such as tension, inclination and spatial position of the traction walking plate directly affect the construction safety. At present, the construction personnel use visual observation to obtain the state quantity of traction walking plate in the process of tension wire construction. This monitoring method is not only inefficient, and there are personal subjective factors of judgment errors. For this reason, this paper develops a kind of intelligent traction walking plate for tension wire construction, based on the principle of resistance strain type and gyroscope to obtain the tension and inclination of the traction walking plate, respectively, using two front cameras and two rear cameras to obtain the spatial position of the traction walking plate, and finally completing the real‐time transmission of the monitoring data through the Lora technology. The developed intelligent traction walking plate was applied in Shandong Heze Yongfeng 220 kV transmission line project on 11 October 2020, which improved the construction efficiency by 15.71% while ensuring the construction safety.
MUSE adaptive-optics spectroscopy confirms dual active galactic nuclei and strongly lensed systems at sub-arcsec separation
Authors: Scialpi M. , Mannucci F. , Marconcini C. , Venturi G. , Pancino E. , Marconi A. , Cresci G. , Belfiore F. , Amiri A. , Bertola E. , Carniani S. , Cicone C. , Ciurlo A. , D’Amato Q. , Ginolfi M. , Lusso E. , Marasco A. , Nardini E. , Rubinur K. , Severgnini P. , Tozzi G. , Ulivi L. , Vignali C. , Volonteri M.
Published: July 2024

The novel Gaia multi peak (GMP) technique has proven to be able to successfully select dual and lensed active galactic nuclei (AGN) candidates at sub-arcsecond separations. Both populations are important because dual AGN represent one of the central, still largely untested, predictions of ΛCDM cosmology, and compact lensed AGN allow us to probe the central regions of the lensing galaxies. In this work, we present high-spatial-resolution spectroscopy of 12 GMP-selected systems. We used the adaptive-optics assisted integral-field spectrograph MUSE at the VLT to resolve each system and investigate the nature of each component. All targets show the presence of two components confirming the GMP selection. We classify 4 targets as dual AGN, 3 as lensed quasar candidates, and 5 as a chance alignment of a star and an AGN. With separations ranging from 0.30″ to 0.86″, these dual and lensed systems are among the most compact systems discovered to date at z > 0.5. This is the largest sample of distant dual AGN with sub-arcsecond separations ever presented in a single paper.
Vanadium oxide clusters in substellar atmospheres
Authors: Lecoq-Molinos H. , Gobrecht D. , Sindel J. P. , Helling Ch. , Decin L.
Published: July 2024

Context. As a refractory material, vanadia (solid V2O5) is likely to be found as a condensate in the atmospheres of substellar objects such as exoplanets and brown dwarfs. However, the nature of the nanometer-sized vanadium oxide clusters that partake in the nucleation process is not well understood.

Aims. We aim to understand the formation of cloud condensation nuclei in oxygen-rich substellar atmospheres by calculating the relevant fundamental properties of the energetically most favorable vanadium oxide molecules and clusters and, investigate how they contribute to the formation of condensation seeds.

Methods. We applied a hierarchical optimization approach in order to find the most favourable structures for clusters of (VO)N and (VO2)N for N = 1−10, and of (V2O5)N for N = 1−4, and to calculate their thermodynamical potentials. The candidate geometries are initially optimized by applying classical interatomic potentials; these are then refined at the B3LYP/cc-pVTZ level of theory to obtain accurate zero-point energies and thermochemical quantities.

Results. We present previously unreported vanadium oxide cluster structures as the lowest-energy isomers. Moreover, we report revised cluster energies and their thermochemical properties. Chemical equilibrium calculations are used to assess the impact of the updated and newly derived thermodynamic potentials on the gas-phase abundances of vanadium-bearing species. In chemical equilibrium, larger clusters from different stoichiometric families are found to be the most abundant vanadium-bearing species for temperatures below ~1000 K, while molecular VO is the most abundant between ~1000 K and ~2000 K. We determine the nucleation rates of each stoichiometric family for a given (Tgas, pgas) profile of a brown dwarf using both classical and non-classical nucleation theory.

Conclusions. Small differences in the revised Gibbs free energies of the clusters have a large impact on the abundances of vanadium-bearing species in chemical equilibrium at temperatures below ~1000 K. These abundance changes subsequently have an impact on the nucleation rates of each stoichiometric family. We find that with the revised and more accurate cluster data, non-classical nucleation rates are up to 15 orders of magnitude higher than classical nucleation rates.
Unveiling the nature of two dwarf novae: CRTS J080846.2+313106 and V416 Dra
Authors: Joshi Arti , Catelan Márcio , Scaringi Simone , Schwope Axel , Anupama G. C. , Rawat Nikita , Sahu Devendra K. , Singh Mridweeka , Dastidar Raya , Subramanian Rama Venkata , Rao Srinivas M.
Published: July 2024

We present the analysis of optical photometric and spectroscopic observations of two non-magnetic cataclysmic variables, namely CRTS J080846.2+313106 and V416 Dra. We find CRTS J080846.2+313106 to vary with a period of 4.9116 ± 0.0003 h, which was not found in earlier studies and which we provisionally suggest is the orbital period of the system. In both long-period systems, the observed dominant signal at the second harmonic of the orbital frequency and the orbital modulation during quiescence are suggestive of ellipsoidal variation from changing aspects of the secondary, with an additional contribution from the accretion stream or hotspot. However, during the outburst, the hotspot itself is overwhelmed by the increased brightness, which is possibly associated with the accretion disc. The mid-eclipse phase for V416 Dra occurs earlier and the width of the eclipse is greater during outbursts compared to quiescence, suggesting an increased accretion disc radius during outbursts. Furthermore, from our investigation of the accretion disc eclipse in V416 Dra, we find that a total disc eclipse is possible during quiescence, whereas the disc seems to be partially obscured during outbursts, which further signifies that the disc may grow in size as the outburst progresses. The optical spectra of CRTS J080846.2+313106 and V416 Dra are typical of dwarf novae during quiescence, and they both show a significant contribution from the M2-4V secondary. The light curve patterns, orbital periods, and spectra observed in the two systems look remarkably similar, and seem to resemble the characteristics of U Gem-type dwarf novae.
The expansion of the GRB 221009A afterglow
Authors: Giarratana S. , Salafia O. S. , Giroletti M. , Ghirlanda G. , Rhodes L. , Atri P. , Marcote B. , Yang J. , An T. , Anderson G. , Bright J. S. , Farah W. , Fender R. , Leung J. K. , Motta S. E. , Pérez-Torres M. , van der Horst A. J.
Published: July 2024

We observed γ-ray burst (GRB) 221009A using very long baseline interferomety (VLBI) with the European VLBI Network (EVN) and the Very Long Baseline Array (VLBA), over a period spanning from 40 to 262 days after the initial GRB. The high angular resolution (mas) of our observations allowed us, for the second time ever, after GRB 030329, to measure the projected size, s, of the relativistic shock caused by the expansion of the GRB ejecta into the surrounding medium. Our observations support the expansion of the shock with a > 4σ-equivalent significance, and confirm its relativistic nature by revealing an apparently superluminal expansion rate. Fitting a power law expansion model, s ∝ ta, to the observed size evolution, we find a slope a = 0.69−0.14+0.13. Fitting the data at each frequency separately, we find different expansion rates, pointing to a frequency-dependent behaviour. We show that the observed size evolution can be reconciled with a reverse shock plus forward shock, provided that the two shocks dominate the emission at different frequencies and, possibly, at different times.
Machine learning for exoplanet detection in high-contrast spectroscopy
Authors: Nath-Ranga R. , Absil O. , Christiaens V. , Garvin E. O.
Published: July 2024

Context.The advent of high-contrast imaging instruments combined with medium-resolution spectrographs allows spectral and temporal dimensions to be combined with spatial dimensions to detect and potentially characterize exoplanets with higher sensitivity.

Aims.We developed a new method to effectively leverage the spectral and spatial dimensions in integral-field spectroscopy (IFS) datasets using a supervised deep-learning algorithm to improve the detection sensitivity to high-contrast exoplanets.

Methods.We began by applying a data transform whereby the four-dimensional (two spatial dimensions, one spectral dimension, and one temporal dimension) IFS datasets are replaced by four-dimensional cross-correlation coefficient tensors obtained by cross-correlating our data with young gas giant spectral template spectra. Thus, the spectral dimension is replaced by a radial velocity dimension and the rest of the dimensions are retained ‘as is’. This transformed data is then used to train machine learning (ML) algorithms. We trained a 2D convolutional neural network with temporally averaged spectral cubes as input, and a convolutional long short-term memory memory network that uses the temporal data as well. We compared these two models with a purely statistical (non-ML) exoplanet detection algorithm, which we developed specifically for four-dimensional datasets, based on the concept of the standardized trajectory intensity mean (STIM) map. We tested our algorithms on simulated young gas giants inserted into a SINFONI dataset that contains no known exoplanet, and explored the sensitivity of algorithms to detect these exoplanets at contrasts ranging from 10−3to 10−4for different radial separations.

Results.We quantify the relative sensitivity of the algorithms by using modified receiver operating characteristic curves (mROCs). We discovered that the ML algorithms produce fewer false positives and have a higher true positive rate than the STIM-based algorithm. We also show that the true positive rate of ML algorithms is less impacted by changing radial separation than the STIM-based algorithm. Finally, we show that preserving the velocity dimension of the cross-correlation coefficients in the training and inference plays an important role in ML algorithms being more sensitive to the simulated young gas giants.

Conclusions.In this paper we demonstrate that ML techniques have the potential to improve the detection limits and reduce false positives for directly imaged planets in IFS datasets, after transforming the spectral dimension into a radial velocity dimension through a cross-correlation operation and that the presence of the temporal dimension does not lead to increased sensitivity.
The evolution of accreting population III stars at 10−6–103 M⊙ yr−1
Authors: Nandal Devesh , Zwick Lorenz , Whalen Daniel J. , Mayer Lucio , Ekström Sylvia , Meynet Georges
Published: July 2024

Context. The first stars formed over five orders of magnitude in mass by accretion in primordial dark matter halos.

Aims. We study the evolution of massive, very massive and supermassive primordial (Pop III) stars over nine orders of magnitude in accretion rate.

Methods. We use the stellar evolution code GENEC to evolve accreting Pop III stars from 10−6–103 M⊙ yr−1 and study how these rates determine final masses. The stars are evolved until either the end central Si burning or they encounter the general relativistic instability (GRI). We also examine how metallicity affects the evolution of the star at one accretion rate.

Results. At rates below ∼2.5 × 10−5 M⊙ yr−1 the final mass of the star falls below that required for pair-instability supernovae. The minimum rate required to produce black holes with masses above 250 M⊙ is ∼5 × 10−5 M⊙ yr−1, well within the range of infall rates found in numerical simulations of halos that cool via H2, ≲10−3 M⊙ yr−1. At rates of 5 × 10−5 M⊙ yr−1 to 4 × 10−2 M⊙ yr−1, like those expected for halos cooling by both H2 and Lyα, the star collapses after Si burning. At higher accretion rates the GRI triggers the collapse of the star during central H burning. Stars that grow at above these rates are cool red hypergiants with effective temperatures log(Teff) = 3.8 and luminosities that can reach 1010.5 L⊙. At accretion rates of 100–1000 M⊙ yr−1 the gas encounters the general relativistic instability prior to the onset of central hydrogen burning and collapses to a black hole with a mass of ∼106 M⊙ without ever having become a star.

Conclusions. Our models corroborate previous studies of Pop III stellar evolution with and without hydrodynamics over separate, smaller ranges in accretion rate. They also reveal for the first time the critical transition rate in accretion above which catastrophic baryon collapse, like that which can occur during galaxy collisions in the high-redshift Universe, produces supermassive black holes via dark collapse.
PHANGS-MeerKAT and MHONGOOSE HI observations of nearby spiral galaxies: Physical drivers of the molecular gas fraction, Rmol
Authors: Eibensteiner Cosima , Sun Jiayi , Bigiel Frank , Leroy Adam K. , Schinnerer Eva , Rosolowsky Erik , Kurapati Sushma , Pisano D. J. , de Blok W. J. G , Barnes Ashley T. , Thorp Mallory , Colombo Dario , Koch Eric W. , Chiang I-Da , Ostriker Eve C. , Murphy Eric J. , Zabel Nikki , Laudage Sebstian , Maccagni Filippo M. , Healy Julia , Sekhar Srikrishna , Utomo Dyas , den Brok Jakob , Cao Yixian , Chevance Mélanie , Dale Daniel A. , Faesi Christopher M. , Glover Simon C. O. , He Hao , Jeffreson Sarah , Jiménez-Donaire María J. , Klessen Ralf , Neumann Justus , Pan Hsi-An , Pathak Debosmita , Querejeta Miguel , Teng Yu-Hsuan , Usero Antonio , Williams Thomas G.
Published: July 2024

The molecular-to-atomic gas ratio is crucial to our understanding of the evolution of the interstellar medium (ISM) in galaxies. We investigated the balance between the atomic (ΣHI) and molecular gas (ΣH2) surface densities in eight nearby star-forming galaxies using new high-quality observations from MeerKAT and ALMA (for H I and CO, respectively). We defined the molecular gas ratio as Rmol = ΣH2/ΣHI and measured how Rmol depends on local conditions in the galaxy disks using multiwavelength observations. We find that, depending on the galaxy, H I is detected at > 3σ out to 20 − 120 kpc in galactocentric radius (rgal). The typical radius at which ΣHI reaches 1 M⊙ pc−2 is rH I ≈ 22 kpc, which corresponds to 1 − 3 times the optical radius (r25). We note that, Rmol correlates best with the dynamical equilibrium pressure, PDE, among potential drivers studied, with a median correlation coefficient of ⟨ρ⟩ = 0.89. Correlations between Rmol and the star formation rate surface density, total gas surface density, stellar surface density, metallicity, and ΣSFR/PDE (a proxy for the combined effect of the UV radiation field and number density) are present but somewhat weaker. Our results also show a direct correlation between PDE and ΣSFR, supporting self-regulation models. Quantitatively, we measured similar scalings as previous works, and attribute the modest differences that we do find to the effect of varying resolution and sensitivity. At rgal ≳ 0.4r25, atomic gas dominates over molecular gas among our studied galaxies, and at the balance of these two gas phases (Rmol = 1), we find that the baryon mass is dominated by stars, with Σ* > 5 Σgas. Our study constitutes an important step in the statistical investigation of how local galaxy properties (stellar mass, star formation rate, or morphology) impact the conversion from atomic to molecular gas in nearby galaxies.
Properties of observable mixed inertial and gravito-inertial modes in γ Doradus stars
Authors: Galoy Marion , Lignières François , Ballot Jérôme
Published: July 2024

Context. The space missions Kepler and TESS provided a large number of highly detailed time series for main-sequence stars, including γ Doradus stars. Additionally, numerous γ Doradus stars are to be observed in the near future thanks to the upcoming PLATO mission. In γ Doradus stars, gravito-inertial modes in the radiative zone and inertial modes in the convective core can interact resonantly, which translates into the appearance of dip structures in the period spacing of modes. Those dips are information-rich, as they are related to the star core characteristics.

Aims. Our aim is to characterise these dips according to stellar properties and thus to develop new seismic diagnostic tools to constrain the internal structure of γ Doradus stars, especially their cores.

Methods. We used the two-dimensional oscillation code TOP to compute sectoral prograde and axisymmetric dipolar modes in γ Doradus stars at different rotation rates and evolutionary stages. We then characterised the dips we obtained by their width and location on the period spacing diagram.

Results. We found that the width and the location of the dips depend quasi-linearly on the ratio of the rotation rate and the Brunt-Väisälä frequency at the core interface. This allowed us to determine empirical relations between the width and location of dips as well as the resonant inertial mode frequency in the core and the Brunt-Väisälä frequency at the interface between the convective core and the radiative zone. We propose an approximate theoretical model to support and discuss these empirical relations.

Conclusions. The empirical relations we established could be applied to dips observed in data, which would allow for the estimation of frequencies of resonant inertial modes in the core and of the Brunt-Väisälä jump at the interface between the core and the radiative zone. As those two parameters are both related to the evolutionary stage of the star, their determination could lead to more accurate estimations of stellar ages.
Low-dimensional signal representations for massive black hole binary signals analysis from LISA data
Authors: Leroy Elie , Bobin Jérôme , Moutarde Hervé
Published: July 2024

Context. The space-based gravitational wave observatory LISA will provide a wealth of information to analyze massive black hole binaries with high chirp masses, beyond 105 solar masses. The large number of expected MBHBs (one event a day on average) increases the risk of overlapping between events. As well, the data will be contaminated with non-stationary artifacts, such as glitches and data gaps, which are expected to strongly impact the MBHB analysis, which mandates the development of dedicated detection and retrieval methods on long time intervals.

Aims. Building upon a methodological approach we introduced for galactic binaries, in this article we investigate an original non-parametric recovery of MBHB signals from measurements with instrumental noise typical of LISA in order to tackle detection and signal reconstruction tasks on long time intervals.

Methods. We investigated different approaches based on sparse signal modeling and machine learning. In this framework, we focused on recovering MBHB waveforms on long time intervals, which is a building block to further tackling more general signal recovery problems, from gap mitigation to unmixing overlapped signals. To that end, we introduced a hybrid method called SCARF (sparse chirp adaptive representation in Fourier), which combines a deep learning modeling of the merger of the MBHB with a specific adaptive time-frequency representation of the inspiral.

Results. Numerical experiments have been carried out on simulations of single MBHB events that account for the LISA response and with realistic realizations of noise. We checked the performances of the proposed hybrid method for the fast detection and recovery of the MBHB.
Local spherical collapsing box in ATHENA++: Numerical implementation and benchmark tests
Authors: Xu Ziyan , Lynch Elliot M. , Laibe Guillaume
Published: July 2024

We implement a local model for a spherical collapsing or expanding gas cloud in the ATHENA++ magnetohydrodynamic code. This local model consists of a Cartesian periodic box with time-dependent geometry. We present a series of benchmark test problems, including nonlinear solutions and linear perturbations of the local model, confirming the code’s desired performance. During a spherical collapse, a horizontal shear flow is amplified, corresponding to angular momentum conservation of zonal flows in the global problem; wave speed and the amplitude of sound waves increase in the local frame, due to the reduction in the characteristic length scale of the box, which can lead to an anisotropic effective sound speed in the local box. Our code conserves both mass and momentum-to-machine precision. This numerical implementation of the local model has potential applications to the study of local physics and hydrodynamic instabilities during protostellar collapse, providing a powerful framework for better understanding the earliest stages of star and planet formation.
Common origin for black holes in both high mass X-ray binaries and gravitational-wave sources
Authors: Belczynski Krzysztof , Done Christine , Hagen Scott , Lasota Jean-Pierre , Sen Koushik
Published: July 2024

Black-hole (BH) high-mass X-ray binary (HMXB) systems are likely to be the progenitors of BH-BH mergers detected in gravitational waves by LIGO/Virgo/KAGRA (LVK). Yet merging BHs reach higher masses (∼100 M⊙) than BHs in HMXBs (∼20 M⊙) and typically exhibit lower spins (aBH ≲ 0.25 with a larger values tail) than what is often claimed for BHs in HMXBs (aBH ≳ 0.9). This could suggest that these two classes of systems belong to different populations, but here we show that this may not necessarily be the case. The difference in masses is easily explained as the known HMXB-BHs are in galaxies with relatively high metallicity, so their progenitor stars are subject to strong mass loss from winds, leading to relatively low-mass BH at core collapse. Conversely, LVK is also able to detect BHs from low-metallicity galaxies that are known to naturally produce more massive stellar-origin BHs. However, the difference in spin is more difficult to explain. Models with efficient angular momentum transport in stellar interiors produce slowly spinning progenitors for both LVK and HMXB BHs. Known HMXBs have orbital periods that are too long for efficient tidal spin-up and are also unlikely to have undergone significant accretion spin-up. Instead, we show that the derived value of the BH spin depends strongly on how the HMXB accretion disc emission is modelled. We argue that since Cyg X-1 is never observed to be in a soft spectral state, the appropriate spectral models must take into account the Comptonisation of the disc photosphere. We show that such models are consistent with low spin values, namely: aBH ∼ 0.1. This was recently confirmed by other teams for both Cyg X-1 and LMC X-1 and here we show this is also the case for M33 X-7. We conclude that all known HMXB BHs can exhibit a low spin, in accordance with the results of stellar evolution models. Hence, the observations presented in this work are consistent with LVK BHs and HMXB BHs belonging to the same population.
Extended gamma-ray emission from particle escape in pulsar wind nebulae
Authors: Martin Pierrick , de Guillebon Louis , Collard Eliot , Mertz Inès , Mohrmann Lars , Principe Giacomo , Lemoine-Goumard Marianne , Marcowith Alexandre , Terrier Régis , Filipović Miroslav D.
Published: July 2024

Context. There is growing evidence from gamma-ray observations at high and very high energies that particle escape is a key aspect shaping the morphological properties of pulsar wind nebulae (PWNe) at various evolutionary stages.

Aims. We aim to provide a simple model for the gamma-ray emission from these objects including the transport of particles across the different components of the system. We applied it to sources HESS J1809−193 and HESS J1825−137.

Methods. We developed a multi-zone framework applicable to dynamically young PWNe, taking into account the diffusive escape of relativistic electron-positron pairs out of the nebula into the parent supernova remnant (SNR) and their confinement downstream of the magnetic barrier of the forward shock until an eventual release into the surrounding interstellar medium (ISM).

Results. For a wide range of turbulence properties in the nebula, the GeV–TeV inverse-Compton radiation from pairs that escaped into the remnant can be a significant if not dominant contribution to the emission from the system. It may dominate the pion-decay radiation from cosmic rays accelerated at the forward shock and advected downstream of it. In the TeV–PeV range, the contribution from particles escaped into the ISM can exceed by far that of the SNR+PWN components. Applied to HESS J1809−193 and HESS J1825−137, we found that spatially extended GeV–TeV emission components can be accounted for mostly from particles escaped into the ISM, while morphologically more compact components above 50 − 100 TeV are ascribed to the PWNe. In these two cases, the model suggests high turbulence in the nebula and a forward shock accelerating cosmic rays up to ∼100 TeV at most.

Conclusions. The model provides the temporal and spectral properties of the flux of particles originally energized by the pulsar wind and ultimately released in the ISM. It can be used to constrain the transport of particles in the vicinity of pulsar-PWN-SNR systems from broadband gamma-ray observations, or in studies of the contribution of pulsar-related systems to the local positron flux.
Parameter estimation from the Lyα forest in the Fourier space using an information-maximizing neural network
Authors: Maitra Soumak , Cristiani Stefano , Viel Matteo , Trotta Roberto , Cupani Guido
Published: July 2024

Aims. Our aim is to present a robust parameter estimation with simulated Lyα forest spectra from Sherwood-Relics simulations suite by using an information-maximizing neural network (IMNN) to extract maximal information from Lyα 1D-transmitted flux in the Fourier space.

Methods. We performed 1D estimations using IMNN for intergalactic medium (IGM) thermal parameters T0 and γ at z = 2 − 4, and cosmological parameters σ8 and ns at z = 3 − 4. We compared our results with estimates from the power spectrum using the posterior distribution from a Markov chain Monte Carlo (MCMC). We then checked the robustness of IMNN estimates against deviation in spectral noise levels, continuum uncertainties, and instrumental smoothing effects. Using mock Lyα forest sightlines from the publicly available CAMELS project, we also checked the robustness of the trained IMNN on a different simulation. As a proof of concept, we demonstrated a 2D-parameter estimation for T0 and H I photoionization rates, ΓHI.

Results. We obtain improved estimates of T0 and γ using IMNN over the standard MCMC approach. These estimates are also more robust against signal-to-noise deviations at z = 2 and 3. At z = 4, the sensitivity to noise deviations is on par with MCMC estimates. The IMNN also provides T0 and γ estimates that are robust against continuum uncertainties by extracting small-scale continuum-independent information from the Fourier domain. In the cases of σ8 and ns, the IMNN performs on par with MCMC but still offers a significant speed boost in estimating parameters from a new dataset. The improved estimates with IMNN are seen for high instrumental resolution (FWHM = 6 km s−1). At medium or low resolutions, the IMNN performs similarly to MCMC, suggesting an improved extraction of small-scale information with IMNN. We also find that IMNN estimates are robust against the choice of simulation. By performing a 2D-parameter estimation for T0 and ΓHI, we also demonstrate how to take forward this approach observationally in the future.
ViCTORIA project: The LOFAR-MeerKAT view of active galactic nuclei in Virgo cluster early-type galaxies
Authors: Spasic A. , Edler H. W. , Su Y. , Brüggen M. , de Gasperin F. , Pasini T. , Heesen V. , Simonte M. , Boselli A. , Röttgering H. J. A. , Fossati M.
Published: July 2024

Context. The evolution of active galactic nuclei (AGNs) is closely connected to their host galaxies and surroundings. Via feedback processes, AGNs can counteract the cooling of the intracluster medium (ICM) and suppress star formation in their host galaxies. Radio observations at low frequencies provide a glimpse into the history of AGN activity. The Virgo cluster is a substantial reservoir of nearby galaxies and provides an ideal laboratory for the study of AGNs as well as their feedback mechanisms.

Aims. The aim of our work is to characterise the AGN population within the Virgo cluster down to low radio luminosities, constrain the AGN duty cycle, and investigate environmental feedback in cluster member galaxies.

Methods. We analysed 144 MHz and 1.3 GHz radio observations of early-type galaxies from the ACS Virgo Cluster Survey (ACSVCS) taken with LOFAR and MeerKAT.

Results. We detect 12 of these galaxies at 144 MHz, five of which show clearly extended radio emission. The radio luminosity shows a strong dependence on the stellar mass of the host galaxy, in agreement with previous results. As a notable outlier, the massive elliptical galaxy NGC 4365 (M* = 2.2 × 1011 M⊙) is not detected as compact source in the LOFAR observations. Instead, it is surrounded by diffuse, low-surface brightness emission, which hints towards a past phase of stronger nuclear activity. Furthermore, we find a cavity in NGC 4472 (=M 49) inflated by the wide-angle tail only visible in the LOFAR data, which implies that the cavity was created by a past outburst. The corresponding cavity power is of the same order of magnitude as the jet power in the present duty cycle of the AGN.
Dynamical formation of Gaia BH3 in the progenitor globular cluster of the ED-2 stream
Authors: Marín Pina Daniel , Rastello Sara , Gieles Mark , Kremer Kyle , Fitzgerald Laura , Rando Forastier Bruno
Published: July 2024

Context. The star–black hole (S–BH) binary known as Gaia BH3, discovered by the Gaia Collaboration is chemically and kinematically associated with the metal-poor ED-2 stream in the Milky Way halo.

Aims. We explore the possibility that Gaia BH3 was assembled dynamically in the progenitor globular cluster (GC) of the ED-2 stream.

Methods. We used a public suite of star-by-star dynamical Monte Carlo models to identify S–BH binaries in GCs with different initial masses and (half-mass) radii.

Results. We show that a likely progenitor of the ED-2 stream was a relatively low-mass (≲105 M⊙) GC with an initial half-mass radius of ∼4 pc. Such a GC can dynamically retain a large fraction of its BH population and dissolve on the orbit of ED-2. From the suite of models we find that GCs produce ∼3 − 30 S–BH binaries, approximately independently of initial GC mass and inversely correlated with initial cluster radius. Scaling the results to the Milky Way GC population, we find that ∼75% of the S–BH binaries formed in GCs are ejected from their host GC, all in the early phases of evolution (≲1 Gyr); these are expected to no longer be close to streams. The ∼25% of S–BH binaries retained until dissolution are expected to form part of streams, such that for an initial mass of the progenitor of ED-2 of a few 104 M⊙, we expect ∼2 − 3 S–BH to end up in the stream. GC models with metallicities similar to Gaia BH3 (≲1% solar) include S–BH binaries with similar BH masses (≳30 M⊙), orbital periods, and eccentricities.

Conclusion. We predict that the Galactic halo contains of order 105 S–BH binaries that formed dynamically in GCs, a fraction of which may readily be detected in Gaia DR4. The detection of these sources provides valuable tests of BH dynamics in clusters and their contribution to gravitational wave sources.
Hydrodynamical simulations of wind interaction in spider systems
Authors: Guerra C. , Meliani Z. , Voisin G.
Published: July 2024

Context. The detected population of “spiders”, referring to millisecond pulsar binaries, has significantly grown in the past decade thanks to multiwavelength follow-up investigations of unidentified Fermi sources. These systems consist of low-mass stellar companions orbiting rotation-powered millisecond pulsars in short periods of a few hours up to day. Among them, a subset of intriguing objects called transitional millisecond pulsars (tMSPs) has been shown to exhibit a remarkable behavior, transitioning between pulsar-binary and faint low-mass X-ray binary states over a span of a few years.

Aims. Our objective is to study the interaction of stellar winds in tMSPs in order to understand their observational properties. To this end we focus on the parameter range that places the system near Roche-lobe overflow.

Methods. Employing the adaptative mesh refinement (AMR) AMRVAC 2.0 code, we performed 2D hydrodynamical (HD) simulations of the interaction between the flows from both stars, accounting for the effects of gravity and orbital motion.

Results. By studying the mass loss and launch speed of the winds, we successfully recreated two phenomenologically distinct regimes: the accretion stream and the pulsar radio state. We also identified the tipping point that marks the sharp transition between these two states. In the accretion stream state, we discover a very strong variability induced by the pulsar wind. In the pulsar state, we reconstructed the corresponding X-ray light curves of the system that produces the characteristic double-peak pattern of these systems. The position of the peaks is shifted due to orbital motion and the leading peak is weaker due to eclipsing by the companion.

Conclusions. This study highlights the importance of gravity and orbital motion in the interaction between the companion and pulsar winds. Our setup allows the study of the complex interaction between the pulsar wind and an accretion stream during mass transfer. We suggest that a smaller leading peak in X-rays is indicative of a nearly edge-on system.
Magnetism in LAMOST CP stars observed by TESS
Authors: Thomson-Paressant K. , Neiner C. , Labadie-Bartz J.
Published: July 2024

Context. A thousand new magnetic candidate CP stars have been identified with LAMOST, of which ∼700 prime targets have had rotational modulation determined by TESS.

Aims. We aim to check for the presence of a magnetic field in a subsample of these LAMOST CP stars, test the viability of the 5200 Å depression used to select the mCP candidates in the LAMOST survey as a reliable indicator of magnetism, and expand on the limited database of known magnetic hot stars. The sample includes some pulsators that would be valuable targets for magneto-asteroseismology.

Methods. We selected ∼100 magnetic candidate LAMOST CP stars that present a depression at 5200 Å in their spectrum and that also display rotational modulation in their TESS photometric light curves. We obtained spectropolarimetric observations of 39 targets from this sample with ESPaDOnS at CFHT. We utilised the least squares deconvolution method to generate the mean profile of the Stokes V and I parameters, from which the longitudinal magnetic field strength for each target can be determined. For HD 49198, we performed more in-depth analysis to determine the polar magnetic field strength and configuration.

Results. We detect fields in at least 36 of the 39 targets in our sample. This success rate in detecting a magnetic field (above 92%) is very high compared to the occurrence of magnetic fields in hot stars (∼10%). Four of these newly discovered magnetic stars are magnetic pulsators. In particular, we detect the strongest field around a δ Scuti star discovered to date: a 12 kG dipolar field in HD 49198.

Conclusions. From our analysis, we conclude that using the 5200 Å depression displayed in the spectra in combination with rotational modulation in photometric data is a very reliable method of identifying magnetic candidates in this population of stars.