物理与天体物理最新文献

{"title":"A multi-frequency, multi-epoch radio continuum study of the Arches cluster with the Very Large Array","authors":"M. Cano-González, R. Schödel, A. Alberdi, J. Moldón, M. Pérez-Torres, F. Najarro, A. T. Gallego-Calvente","doi":"10.1051/0004-6361/202451771","DOIUrl":"https://doi.org/10.1051/0004-6361/202451771","url":null,"abstract":"<i>Context.<i/> The Arches cluster, one of the most massive clusters in the Milky Way, is located about 30 pc in projection from the central massive black hole Sagittarius A* at a distance of ≈8 kpc from Earth. With its high mass, young age, and location in the Galaxy’s most extreme star forming environment, the Arches is an extraordinary laboratory for studying massive stars and clusters.<i>Aims.<i/> Our objective is to improve our knowledge of the properties of massive stars and the Arches cluster through high-angular-resolution radio continuum studies.<i>Methods.<i/> We observed the Arches cluster with the Karl G. Jansky Very Large Array in the <i>C<i/>- and <i>X<i/>-bands (central frequencies of 6 and 10 GHz respectively) in two epochs at <i>C<i/>-band and five epochs at <i>X<i/>-band throughout 2016, 2018, and 2022, covering time spans ranging from 22 days to 6 years. We used the A-configuration to achieve the highest possible angular resolution and cross-matched the detected point-sources with stars detected in the infrared, using proper motion catalogues to ensure cluster membership.<i>Results.<i/> We report the most extensive radio point-source catalogue of the cluster to date, with a total of 25 radio detections (7 more than the most recent study). We also created the deepest (2.5 <i>μ<i/>Jy in <i>X<i/>-band) images of the cluster so far in the 4 to 12 GHz frequency range. Most of our stellar radio sources (12 out of 18) show a positive spectral index, indicating that the dominant emission process is free-free thermal radiation, which probably originates from stellar winds. We find that radio variability is more frequent than what was inferred from previous observations, and affects up to 60% of the sources associated with bright stellar counterparts, with two of them, F18 and F26, showing extreme flux variability. We propose four of our detections (F6, F18, F19, and F26) as primary candidates for colliding-wind binaries (CWBs) based on their consistent flat-to-negative spectral index. We classify F7, F9, F12, F14, and F55 as CWB binary candidates based on their high flux and/or spectral index variability, and X-ray counterparts. Thus, we infer a 14/23 ≈ 61% multiplicity fraction for the radio stars of the Arches cluster when combining our findings with recent infrared radial velocity studies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"16 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measuring high-efficiency perfect composite vortex beams with reflective metasurfaces in microwave band","authors":"Jing Hong, Mengyi Ni, Zhengping Zhang, Zheng-Da Hu, Jicheng Wang, Xiaopeng Shen, Xiong Wang, Mengmeng Li, Sergei Khakhomov","doi":"10.1515/nanoph-2024-0294","DOIUrl":"https://doi.org/10.1515/nanoph-2024-0294","url":null,"abstract":"Optical vortex beams carrying orbit angular momentum have attracted significant attention recently. Perfect vortex beams, characterized by their topological charge-independent intensity profile, have important applications in enhancing communication capacity and optimizing particle manipulation. In this paper, metal-insulator-metal copper-coin type reflective metasurfaces are proposed to generate perfect composite vortex beams in X-band. We introduce the qualified equivalent circuit model based on the theory of transmission line to design the meta-atom of the structure. The experiments are performed to measure the far-field and near-field perfect composite vortex beams and evaluate their orbital angular momentum purity at different frequencies. The experimental results agree well with the theoretical predictions. This work provides new ideas and methods for generating high-quality metasurface-based perfect composite vortex beams in the microwave region, paving an ideal path for microwave communication systems, optical manipulation and radar detection.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"45 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Highly Efficient Novel Garnet-Structured Yellow Emitting Phosphor for High Power Laser-Driven Lighting","authors":"Jiarui Duan, Chen Bai, Jiacheng Sun, Deyin Wang, Yuhua Wang","doi":"10.1002/lpor.202401371","DOIUrl":"https://doi.org/10.1002/lpor.202401371","url":null,"abstract":"A novel blue light excitable yellow emitting phosphor, BaLu₂(Mg_0.6Al_2.8Si_1.6)O₁₂:Ce³⁺, with an external quantum efficiency (EQE) of 66.2%, is developed by substituting Al³⁺-Al³⁺ pairs in BaLu₂Al₄SiO₁₂:Ce³⁺ with Mg²⁺-Si⁴⁺ pairs. Alongside the redshift of Ce³⁺ emission, this substitution also broadened Ce³⁺ emission and reduced its thermal stability. The spectral changes are found to result from variations in the local crystal field and site symmetry of Ce³⁺ due to Mg²⁺-Si⁴⁺ substitution. To assess the feasibility of the newly developed yellow-emitting phosphor for high-power laser lighting, it is constructed into a phosphor wheel. Owing to the efficient heat dissipation via high speed rotation of phosphor wheel, the yellow phosphor exhibit a luminous flux of 3894 lm and shows no obvious emission saturation even excited by blue laser light with a power density of 90.7 W mm⁻². Exciting the yellow phosphor wheel with a blue laser diode (LDs) at a power density of 25.2 W mm⁻² resulted in bright white light with a luminous of 1718.1 lm, a correlated color temperature of 5983 K, a color rendering index of 65.0, and chromatic coordinates of (0.3203, 0.3631). These results suggest that the newly synthesized yellow-emitting phosphor holds significant potential for high-power laser-driven lighting applications.","PeriodicalId":204,"journal":{"name":"Laser & Photonics Reviews","volume":"79 1","pages":""},"PeriodicalIF":11.0,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring Dynamic Dark Energy Models in f(T) Gravity: A Comparative Study of NHDE, THDE, and BHDE","authors":"S. H. Shekh,&nbsp;Anirudh Pradhan,&nbsp;S. P. Gaikwad,&nbsp;K. R. Mule","doi":"10.1007/s10773-024-05833-2","DOIUrl":"10.1007/s10773-024-05833-2","url":null,"abstract":"<div><p>In this work, we explore the cosmological implications of three dynamic dark energy models-New Holographic Dark Energy (NHDE), Tsallis Holographic Dark Energy (THDE), and Barrow Holographic Dark Energy (BHDE)-within the framework of <i>f</i>(<i>T</i>) gravity. These models are motivated by the holographic principle and provide alternatives to the standard <span>(Lambda )</span>CDM model. We adopt a flat, isotropic Friedmann-Robertson-Walker (FRW) universe and employ a specific forms of <i>f</i>(<i>T</i>) gravity. The evolution of key cosmological parameters, such as the isotropic pressure, equation of state (EoS) parameter, and energy conditions, is analyzed for each model. Using observational data from Type Ia supernovae (SNIa), Cosmic Microwave Background (CMB), Baryon Acoustic Oscillations (BAO), and Hubble parameter measurements, we constrain the free parameters of each model and evaluate their compatibility with observational data. The analysis reveals that NHDE, THDE, and BHDE models are viable alternatives to <span>(Lambda )</span>CDM, offering a more dynamic description of dark energy. Each model satisfies key energy conditions, providing a stable framework for explaining cosmic acceleration. The results show deviations from the constant behavior of <span>(Lambda )</span>CDM, indicating the potential for time-evolving dark energy in these models.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"63 12","pages":""},"PeriodicalIF":1.3,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142757999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Methylhydrazinium Lead Halide Perovskites: Effect of Composition and Dimensionality on Their Optoelectronic and Photodetection Properties","authors":"Apurba Mahapatra, Vishnu Anilkumar, Andrea Scarperi, Dominik J. Kubicki, Pankaj Yadav, Mirosław Mączka, Daniel Prochowicz","doi":"10.1021/acsphotonics.4c00599","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c00599","url":null,"abstract":"Over the past few years, lead halide perovskites (LHPs) in the form of single crystals (SCs) have been intensively investigated for photodetection applications. Methylhydrazinium (MHy) is a new type of organic cation that can form either 2D or 3D halide perovskite structures. Here, we study single crystals MHy₂PbI₄ (2D), MHy₂PbBr₄ (2D), MHyPbBr₃ (3D), and mixed-cation MA_0.725MHy_0.275PbBr₃ to determine for the first time how dimensionality and composition affect the photodetection properties of photoconductor-type photodetectors fabricated using this class of solids. The results provide a reference for researchers working in the same domain by revealing the relationship between different types and structures of LHPs and their optoelectronic properties, which is crucial for the further advancement of LHP-based optoelectronic devices.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"31 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photometric detection of internal gravity waves in upper main-sequence stars","authors":"Dominic M. Bowman, Pieterjan Van Daele, Mathias Michielsen, Timothy Van Reeth","doi":"10.1051/0004-6361/202451419","DOIUrl":"https://doi.org/10.1051/0004-6361/202451419","url":null,"abstract":"<i>Context.<i/> Massive main-sequence stars have convective cores and radiative envelopes, but can also have sub-surface convection zones caused by partial ionisation zones. However, the convective properties of such regions strongly depend on opacity and therefore a star’s metallicity. Non-rotating 1D evolution models of main-sequence stars between 7 ≤ <i>M<i/> ≤ 40 M<sub>⊙<sub/> and the metallicity of the Small Magellanic Cloud (SMC) galaxy suggest tenuous (if any) sub-surface convection zones when using the Rayleigh number as a criterion for convection owing to their substantially lower metallicity compared to Galactic massive stars.<i>Aims.<i/> We test whether massive stars of different metallicities both inside and outside of asteroseismically calibrated stability windows for sub-surface convection exhibit different properties in stochastic low-frequency (SLF) variability. Thus, we aim to constrain the metallicity dependence of the physical mechanism responsible for SLF variability commonly found in light curves of massive stars.<i>Methods.<i/> We extracted customised light curves from the ongoing NASA Transiting Exoplanet Survey Satellite (TESS) mission for a sample of massive stars using an effective point spread function (ePSF) method, and compared their morphologies in terms of characteristic frequency, <i>ν<i/><sub>char<sub/>, and amplitude using a Gaussian process (GP) regression methodology.<i>Results.<i/> We demonstrate that the properties of SLF variability observed in time series photometry of massive stars are generally consistent across the metallicity range from the Milky Way down to the SMC galaxy, for stars both inside and outside of the sub-surface stability windows based on the Rayleigh number as a criterion for convection.<i>Conclusions.<i/> We conclude that non-rotating 1D stellar structure models of sub-surface convection cannot alone be used to explain the mechanism giving rise to SLF variability in light curves of massive stars. Additionally, the similar properties of SLF variability across a wide range of metallicity values, which follow the same trends in mass and age in the Hertzsprung–Russell (HR) diagram at both high and low metallicity, support a transition in the dominant mechanism causing SLF variability from younger to more evolved stars. Specifically, core-excited internal gravity waves (IGWs) are favoured for younger stars lacking sub-surface convection zones, especially at low metallicity, and sub-surface convection zones are favoured for more evolved massive stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"260 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-NA 2D Image Edge Detection Using Tamm Plasmon Polaritons in Few-Layer Stratified Media","authors":"Bernardo S. Dias, Jorik van de Groep","doi":"10.1021/acsphotonics.4c01667","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c01667","url":null,"abstract":"Analog optical computing with nanophotonic devices has emerged as a promising solution to the need for ultrafast computation with low power consumption. Several key mathematical operations, including spatial derivatives for edge detection, have recently been demonstrated. However, these initial approaches are typically characterized by a small numerical aperture (NA), strong polarization dependence, narrow operational bandwidths, or the need for complex nanofabrication procedures. Here, we demonstrate how a very simple 7-layer thin-film stack provides dual-channel, high efficiency, polarization-independent 2D edge detection with a numerical aperture approaching 0.9, by leveraging the intrinsic properties of Tamm plasmon polariton resonances. By engineering the resonant decay rates, we propose simple design rules for the layer stack to achieve high-efficiency edge detection with a NA that matches the desired spatial resolution. Using this, we experimentally demonstrate edge detection of micrometer-scale targets with a bandwidth reaching up to 10 nm, enabling operation under filtered, unpolarized, and low-coherence illumination from a halogen lamp. Our results push optical image edge detection toward a wider range of practical applications, including high-resolution microscopy.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"75 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extension of the multilevel radiative transfer code PyRaTE to model linear polarization of molecular lines","authors":"A. Tritsis, N. Kylafis","doi":"10.1051/0004-6361/202347791","DOIUrl":"https://doi.org/10.1051/0004-6361/202347791","url":null,"abstract":"<i>Context.<i/> Linear polarization of spectral lines, commonly known as the Goldreich-Kylafis effect within the star formation community, is one of the most underutilized techniques for probing magnetic fields in the dense and cold interstellar medium.<i>Aims.<i/> In this study, we implement linear polarization of molecular spectral lines into the multilevel, non-local thermodynamic equilibrium radiative transfer code PYRATE.<i>Methods.<i/> Different modes of polarized radiation are treated individually, with separate optical depths computed for each polarization direction. Our implementation is valid in the so-called strong magnetic field limit and is exact for either a system satisfying the large-velocity-gradient approximation, and/or for any system with a uniform magnetic field. We benchmark our implementation against analytical results and provide tests for various limiting cases.<i>Results.<i/> In agreement with previous theoretical results, we find that in the multilevel case the amount of fractional polarization decreases when compared to the two-level approximation, but this result is subject to the relative importance between radiative and collisional processes. Finally, we post-process an axially symmetric, nonideal magnetohydrodynamic chemo-dynamical simulation of a collapsing prestellar core and provide theoretical predictions regarding the shape (as a function of velocity) of the polarization fraction of CO during the early stages in the evolution of molecular clouds.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"37 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inferring the distribution of the ionising photon escape fraction","authors":"Kimi C. Kreilgaard, Charlotte A. Mason, Fergus Cullen, Ryan Begley, Ross J. McLure","doi":"10.1051/0004-6361/202450747","DOIUrl":"https://doi.org/10.1051/0004-6361/202450747","url":null,"abstract":"<i>Context.<i/> The escape fraction of ionising photons from galaxies (<i>f<i/><sub>esc<sub/>) is a key parameter for understanding how intergalactic hydrogen became reionised, but it remains mostly unconstrained. Measurements have been limited to the average value in galaxy ensembles and to handfuls of individual detections.<i>Aims.<i/> To help understand which mechanisms govern ionising photon escape, here we infer the distribution of <i>f<i/><sub>esc<sub/>.<i>Methods.<i/> We developed a hierarchical Bayesian inference technique to estimate the population distribution of <i>f<i/><sub>esc<sub/> from the ratio of Lyman continuum to non-ionising UV flux measured from broadband photometry. We applied it to a sample of 148 <i>z<i/> ≃ 3.5 star-forming galaxies from the VANDELS spectroscopic survey.<i>Results.<i/> We explored four physically motivated distributions: constant, log-normal, exponential, and bimodal, and recovered ⟨<i>f<i/><sub>esc<sub/>⟩≈5% for most models. We find the observations are best described by an exponential <i>f<i/><sub>esc<sub/> distribution with scale factor . This indicates most galaxies in our sample exhibit very low escape fractions, while predicting substantial ionising photon leakage for only a few galaxies, implying a range of optical depths in the interstellar medium and/or time variability in ionising photon escape. We rule out a bimodal distribution at high significance, indicating that a purely bimodal model of ionising photon escape (due to very strong sightline and/or time variability) is not favoured. We compare our recovered exponential distribution with the SPHINX simulations and find that, while the simulation also predicts an exponential distribution, it significantly underpredicts our inferred mean. The distribution of <i>f<i/><sub>esc<sub/> can be a vital test for simulations in understanding ionising photon leakage, and is important to consider to gain a complete picture of reionisation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"69 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Incidence of afterglow plateaus in gamma-ray bursts associated with binary neutron star mergers","authors":"L. Guglielmi, G. Stratta, S. Dall’Osso, P. Singh, M. Brusa, R. Perna","doi":"10.1051/0004-6361/202451877","DOIUrl":"https://doi.org/10.1051/0004-6361/202451877","url":null,"abstract":"One of the most surprising gamma-ray burst (GRB) features discovered with the <i>Swift<i/> X-ray telescope (XRT) is a plateau phase in the early X-ray afterglow light curves. These plateaus are observed in the majority of long GRBs, while their incidence in short GRBs (SGRBs) is still uncertain due to their fainter X-ray afterglow luminosity with respect to long GRBs. An accurate estimate of the fraction of SGRBs with plateaus is of utmost relevance given the implications that the plateau may have for our understanding of the jet structure and possibly of the nature of the binary neutron star (BNS) merger remnant. This work presents the results of an extensive data analysis of the largest and most up-to-date sample of SGRBs observed with the XRT, and for which the redshift has been measured. We find a plateau incidence of 18–37% in SGRBs, which is a significantly lower fraction than that measured in long GRBs (> 50%). Although still debated, the plateau phase could be explained as energy injection from the spin-down power of a newly born magnetized neutron star (NS; magnetar). We show that this scenario can nicely reproduce the observed short GRB (SGRBs) plateaus, while at the same time providing a natural explanation for the different plateau fractions between short and long GRBs. In particular, our findings may imply that only a minority of BNS mergers generating SGRBs leave behind a sufficiently stable or long-lived NS to form a plateau. From the probability distribution of the BNS remnant mass, a fraction 18–37% of short GRB plateaus implies a maximum NS mass in the range ∼2.3 − 2.35 M<sub>⊙<sub/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"75 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}