Predicting chaotic systems is crucial for understanding complex behaviors, yet challenging due to their sensitivity to initial conditions and inherent unpredictability. Probabilistic reservoir computing (RC) is well suited for long-term chaotic predictions by handling complex dynamic systems. Spin–orbit torque (SOT) devices in spintronics, with their nonlinear and probabilistic operations, can enhance performance in these tasks. This study proposes an RC system utilizing SOT devices for predicting chaotic dynamics. By simulating the reservoir in an RC network with SOT devices that achieve nonlinear resistance changes with random distribution, we enhance the robustness for the predictive capability of the model. The RC network predicted the behaviors of the Mackey–Glass and Lorenz chaotic systems, demonstrating that stochastic SOT devices significantly improve long-term prediction accuracy.
{"title":"Improved long-term prediction of chaos using reservoir computing based on stochastic spin–orbit torque devices","authors":"Cen Wang, Xinyao Lei, Kaiming Cai, Xu Ge, Xiaofei Yang, Yue Zhang","doi":"10.1063/5.0231863","DOIUrl":"https://doi.org/10.1063/5.0231863","url":null,"abstract":"Predicting chaotic systems is crucial for understanding complex behaviors, yet challenging due to their sensitivity to initial conditions and inherent unpredictability. Probabilistic reservoir computing (RC) is well suited for long-term chaotic predictions by handling complex dynamic systems. Spin–orbit torque (SOT) devices in spintronics, with their nonlinear and probabilistic operations, can enhance performance in these tasks. This study proposes an RC system utilizing SOT devices for predicting chaotic dynamics. By simulating the reservoir in an RC network with SOT devices that achieve nonlinear resistance changes with random distribution, we enhance the robustness for the predictive capability of the model. The RC network predicted the behaviors of the Mackey–Glass and Lorenz chaotic systems, demonstrating that stochastic SOT devices significantly improve long-term prediction accuracy.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"56 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670407","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}
Xian-Song Zhao, Chao Yu, Chong Wang, Tianyi Li, Bo Liu, Hai Lu, Rong Zhang, Xiankang Dou, Jun Zhang, Jian-Wei Pan
Differential absorption Lidar (DIAL) in the ultraviolet (UV) region is an effective approach for monitoring tropospheric ozone. 4H-SiC single-photon detectors (SPDs) are emergent devices for UV single-photon detection. Here, we demonstrate a 4H-SiC SPD-based ozone DIAL. We design and fabricate the 4H-SiC single-photon avalanche diode with a beveled mesa structure and optimized layer thickness. An active quenching circuit with a quenching time of 1.03 ns is developed to significantly mitigate the afterpulsing effect while enhancing the maximum count rate. After characterization, the SPD exhibits excellent performance with a photon detection efficiency of 16.6% at 266 nm, a dark count rate of 138 kcps, a maximum count rate of 13 Mcps, and an afterpulse probability of 2.7% at room temperature. Then, we apply two 4H-SiC SPDs in an ozone DIAL. The measured ozone concentrations at altitudes of 1–3.5 km agree well with the results of a commercial ozone DIAL. Our work provides an alternative solution for general UV Lidar applications.
{"title":"Differential absorption ozone Lidar with 4H-SiC single-photon detectors","authors":"Xian-Song Zhao, Chao Yu, Chong Wang, Tianyi Li, Bo Liu, Hai Lu, Rong Zhang, Xiankang Dou, Jun Zhang, Jian-Wei Pan","doi":"10.1063/5.0232210","DOIUrl":"https://doi.org/10.1063/5.0232210","url":null,"abstract":"Differential absorption Lidar (DIAL) in the ultraviolet (UV) region is an effective approach for monitoring tropospheric ozone. 4H-SiC single-photon detectors (SPDs) are emergent devices for UV single-photon detection. Here, we demonstrate a 4H-SiC SPD-based ozone DIAL. We design and fabricate the 4H-SiC single-photon avalanche diode with a beveled mesa structure and optimized layer thickness. An active quenching circuit with a quenching time of 1.03 ns is developed to significantly mitigate the afterpulsing effect while enhancing the maximum count rate. After characterization, the SPD exhibits excellent performance with a photon detection efficiency of 16.6% at 266 nm, a dark count rate of 138 kcps, a maximum count rate of 13 Mcps, and an afterpulse probability of 2.7% at room temperature. Then, we apply two 4H-SiC SPDs in an ozone DIAL. The measured ozone concentrations at altitudes of 1–3.5 km agree well with the results of a commercial ozone DIAL. Our work provides an alternative solution for general UV Lidar applications.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"64 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670408","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}
Winda Purwitasari, Ali Sufyan, Rovi Angelo B. Villaos, Zhi-Quan Huang, Arun Bansil, Hsin Lin, Feng-Chuan Chuang
Owing to their unique topologically protected gapless boundary states, topological insulators (TIs) are attracting substantial interest in spintronics and quantum computing. Here, we discuss the structural, electronic, and topological properties of bulk alkaline earth di-pnictides AX2 (where A= Ca, Sr, or Ba and X= As, Sb, or Bi) using first-principles calculations under the hybrid functional approach. Our structural analysis based on phonon dispersion and molecular dynamics calculations establishes the thermodynamic stability of these materials and indicates their potential for synthesis. All investigated compounds are shown to host nontrivial phases upon including spin–orbit coupling. CaAs2, SrSb2, and BaSb2 are found to be strong TIs with sizable bandgaps of up to 213 meV. Nontrivial topology in the case of SrSb2 was further confirmed through surface state computations which showed the presence of gapless surface states. In addition, we demonstrate that using the hybrid functional approach can enhance the accuracy of the calculations to predict experimental findings. Finally, our study suggests that the alkaline earth di-pnictide family would provide a promising materials platform for developing applications of TIs.
{"title":"Topological insulating phase in nonsymmorphic bulk AX2 (A = Ca, Sr, or Ba; and X = As, Sb, or Bi) compounds","authors":"Winda Purwitasari, Ali Sufyan, Rovi Angelo B. Villaos, Zhi-Quan Huang, Arun Bansil, Hsin Lin, Feng-Chuan Chuang","doi":"10.1063/5.0237667","DOIUrl":"https://doi.org/10.1063/5.0237667","url":null,"abstract":"Owing to their unique topologically protected gapless boundary states, topological insulators (TIs) are attracting substantial interest in spintronics and quantum computing. Here, we discuss the structural, electronic, and topological properties of bulk alkaline earth di-pnictides AX2 (where A= Ca, Sr, or Ba and X= As, Sb, or Bi) using first-principles calculations under the hybrid functional approach. Our structural analysis based on phonon dispersion and molecular dynamics calculations establishes the thermodynamic stability of these materials and indicates their potential for synthesis. All investigated compounds are shown to host nontrivial phases upon including spin–orbit coupling. CaAs2, SrSb2, and BaSb2 are found to be strong TIs with sizable bandgaps of up to 213 meV. Nontrivial topology in the case of SrSb2 was further confirmed through surface state computations which showed the presence of gapless surface states. In addition, we demonstrate that using the hybrid functional approach can enhance the accuracy of the calculations to predict experimental findings. Finally, our study suggests that the alkaline earth di-pnictide family would provide a promising materials platform for developing applications of TIs.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"80 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670402","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}
Understanding the fundamental link between structure and functionalization is crucial for designing and optimizing functional materials, since different structural configurations could trigger materials to demonstrate diverse physical and chemical properties. However, the correlation between crystal structure and thermal conductivity (κ) remains unclear. In this study, taking two-dimensional (2D) carbon allotropes Janus-graphene and graphene as study cases, we utilize phonon Boltzmann transport equation combined with machine learning potential to thoroughly investigate the complex folding structure of pure sp2 hybridized Janus-graphene from the perspective of crystal structure, phonon modal resolved thermal transport, and atomic interactions, with the goal of identifying the underlying relationship between 2D geometry and κ. The results reveal that the folded structure in Janus-graphene causes strong symmetry breaking, significantly reduces phonon group velocities, increases phonon–phonon scattering, and ultimately leads to low κ. These findings enhance our understanding of how atomic structure folding affects thermal transport and the relationship between structure and functionalization.
{"title":"Revealing the correlation between asymmetric structure and low thermal conductivity in Janus-graphene via machine learning force constant potential","authors":"Linfeng Yu, Kexin Dong, Qi Yang, Yi Zhang, Xiong Zheng, Huimin Wang, Zhenzhen Qin, Guangzhao Qin","doi":"10.1063/5.0237434","DOIUrl":"https://doi.org/10.1063/5.0237434","url":null,"abstract":"Understanding the fundamental link between structure and functionalization is crucial for designing and optimizing functional materials, since different structural configurations could trigger materials to demonstrate diverse physical and chemical properties. However, the correlation between crystal structure and thermal conductivity (κ) remains unclear. In this study, taking two-dimensional (2D) carbon allotropes Janus-graphene and graphene as study cases, we utilize phonon Boltzmann transport equation combined with machine learning potential to thoroughly investigate the complex folding structure of pure sp2 hybridized Janus-graphene from the perspective of crystal structure, phonon modal resolved thermal transport, and atomic interactions, with the goal of identifying the underlying relationship between 2D geometry and κ. The results reveal that the folded structure in Janus-graphene causes strong symmetry breaking, significantly reduces phonon group velocities, increases phonon–phonon scattering, and ultimately leads to low κ. These findings enhance our understanding of how atomic structure folding affects thermal transport and the relationship between structure and functionalization.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"76 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142665461","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}
Pub Date : 2024-11-18DOI: 10.1088/2058-9565/ad8d07
Sean Lourette, Andrey Jarmola, Jabir Chathanathil, Sebastián C Carrasco, Dmitry Budker, Svetlana A Malinovskaya, A Glen Birdwell, Tony G Ivanov and Vladimir S Malinovsky
We report the first experimental demonstration of stimulated Raman adiabatic passage (STIRAP) in nuclear-spin transitions of 14N within nitrogen-vacancy color centers in diamond. It is shown that the STIRAP technique suppresses the occupation of the intermediate state, which is a crucial factor for improvements in quantum sensing technology. Building on that advantage, we develop and implement a generalized version of the Ramsey interferometric scheme, employing half-STIRAP pulses to perform the necessary quantum-state manipulation with high fidelity. The enhanced robustness of the STIRAP-based Ramsey scheme to variations in the pulse parameters is experimentally demonstrated, showing good agreement with theoretical predictions. Our results pave the way for improving the long-term stability of diamond-based sensors, such as gyroscopes and frequency standards.
{"title":"Ramsey interferometry of nuclear spins in diamond using stimulated Raman adiabatic passage","authors":"Sean Lourette, Andrey Jarmola, Jabir Chathanathil, Sebastián C Carrasco, Dmitry Budker, Svetlana A Malinovskaya, A Glen Birdwell, Tony G Ivanov and Vladimir S Malinovsky","doi":"10.1088/2058-9565/ad8d07","DOIUrl":"https://doi.org/10.1088/2058-9565/ad8d07","url":null,"abstract":"We report the first experimental demonstration of stimulated Raman adiabatic passage (STIRAP) in nuclear-spin transitions of 14N within nitrogen-vacancy color centers in diamond. It is shown that the STIRAP technique suppresses the occupation of the intermediate state, which is a crucial factor for improvements in quantum sensing technology. Building on that advantage, we develop and implement a generalized version of the Ramsey interferometric scheme, employing half-STIRAP pulses to perform the necessary quantum-state manipulation with high fidelity. The enhanced robustness of the STIRAP-based Ramsey scheme to variations in the pulse parameters is experimentally demonstrated, showing good agreement with theoretical predictions. Our results pave the way for improving the long-term stability of diamond-based sensors, such as gyroscopes and frequency standards.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"99 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670318","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}
Pub Date : 2024-11-18DOI: 10.1051/0004-6361/202449941
R. Niedziela, K. Murawski, S. Poedts
Context. This study was carried out in the context of chromosphere heating.Aims. This paper aims to discuss the evolution of driven slow magnetoacoustic waves (SMAWs) in the solar chromosphere modelled with a realistic ionisation profile and to consider their potential role in plasma heating and the generation of plasma outflows.Methods. Two-dimensional (2D) numerical simulations of the solar atmosphere are performed using the JOANNA code. The dynamic behaviour of the atmospheric plasma is governed by the two-fluid equations (with ionisation and recombination terms taken into account) for neutrals (hydrogen atoms) and ions (protons)+electrons. The initial atmosphere is described by a hydrostatic equilibrium (HE) supplemented by the Saha equation (SE) and embedded in a fanning magnetic field. This initial equilibrium is perturbed by a monochromatic driver which operates in the chromosphere on the vertical components of the ion and neutral velocities.Results. Our work shows that the HE+SE model results in time-averaged (net) plasma outflows in the top chromosphere, which are larger than their pure HE counterpart. The parametric studies demonstrate that the largest chromosphere temperature rise occurs for smaller wave driving periods. The plasma outflows exhibit the opposite trend, growing with the driver period.Conclusions. We find that the inclusion of the HE+SE plasma background plays a key role in the evolution of SMAWs in the solar atmosphere.
背景。这项研究是在色球加热的背景下进行的。本文旨在讨论太阳色球层中驱动慢磁声波（SMAWs）的演化，模拟了现实的电离轮廓，并考虑它们在等离子体加热和产生等离子体外流中的潜在作用。使用 JOANNA 代码对太阳大气进行二维（2D）数值模拟。大气等离子体的动态行为受中子（氢原子）和离子（质子）+电子的双流体方程（考虑了电离和重组项）支配。初始大气由静力学平衡（HE）描述，并辅以萨哈方程（SE），嵌入扇形磁场。这种初始平衡受到单色驱动器的扰动，该驱动器在色球层中对离子和中性速度的垂直分量起作用。我们的研究结果表明，HE+SE 模型会导致顶部色球层出现时间平均（净）等离子体外流，其规模大于纯 HE 模型。参数研究表明，在较小的波驱动周期内，色球层的温升最大。等离子体外流则表现出相反的趋势，随着驱动周期的增长而增长。我们发现 HE+SE 等离子体背景的加入在太阳大气中 SMAW 的演化过程中起着关键作用。
{"title":"Driven two-fluid slow magnetoacoustic waves in the solar chromosphere with a realistic ionisation profile","authors":"R. Niedziela, K. Murawski, S. Poedts","doi":"10.1051/0004-6361/202449941","DOIUrl":"https://doi.org/10.1051/0004-6361/202449941","url":null,"abstract":"<i>Context.<i/> This study was carried out in the context of chromosphere heating.<i>Aims.<i/> This paper aims to discuss the evolution of driven slow magnetoacoustic waves (SMAWs) in the solar chromosphere modelled with a realistic ionisation profile and to consider their potential role in plasma heating and the generation of plasma outflows.<i>Methods.<i/> Two-dimensional (2D) numerical simulations of the solar atmosphere are performed using the JOANNA code. The dynamic behaviour of the atmospheric plasma is governed by the two-fluid equations (with ionisation and recombination terms taken into account) for neutrals (hydrogen atoms) and ions (protons)+electrons. The initial atmosphere is described by a hydrostatic equilibrium (HE) supplemented by the Saha equation (SE) and embedded in a fanning magnetic field. This initial equilibrium is perturbed by a monochromatic driver which operates in the chromosphere on the vertical components of the ion and neutral velocities.<i>Results.<i/> Our work shows that the HE+SE model results in time-averaged (net) plasma outflows in the top chromosphere, which are larger than their pure HE counterpart. The parametric studies demonstrate that the largest chromosphere temperature rise occurs for smaller wave driving periods. The plasma outflows exhibit the opposite trend, growing with the driver period.<i>Conclusions.<i/> We find that the inclusion of the HE+SE plasma background plays a key role in the evolution of SMAWs in the solar atmosphere.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"36 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670325","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}
Pub Date : 2024-11-18DOI: 10.1051/0004-6361/202346361
C. Romero, J. Milli, A.-M. Lagrange, R. De Rosa, S. Ertel, C. del Burgo
Context. High-contrast imaging observations mostly rely on angular differential imaging, a successful technique for detecting point-sources, such as planets. However, in the vicinity of the star (typically below 300 mas), this technique suffers from signal self-subtraction when there is not enough field rotation. Building large libraries of reference stars from archival data later used to optimally subtract the stellar halo is a powerful technique known as reference star differential imaging (RSDI) that can overcome this limitation.Aims. We aim at investigating new methods for creating reference libraries composed of multiple stars when applying reference star differential imaging to VLT/SPHERE data. We used for that purpose a data set from the SPHERE High Angular Resolution Debris Disk Survey (SHARDDS), composed of 55 targets observed in broad-band H with the InfraRed Dual-band Imager and Spectrograph (IRDIS) during 2015-2016, with a total of ~20 000 frames. We consider HD 206893, known to host a close-in bound substellar companion HD 206893 B, as a benchmark science target to demonstrate the improved sensitivity provided by this method.Methods. We created libraries of reference frames based on different image similarity metrics: the cosine distance between descriptors created by a convolutional neural network, the Pearson correlation coefficient, the Structural Similarity Index, the Strehl ratio, and raw contrast criteria. We used principal component analysis (PCA) to subtract the stellar halo and tested various normalization options.Results. We obtained the best signal-to-noise ratio (S/N) on HD 206893 B by using the Pearson correlation coefficient (PCC) applied to an annulus between 245 and 612 mas to select reference frames. The ten reference libraries with the highest S/N on the substellar companion HD 206893 B were all based on the PCC method, outperforming other similarity metrics. While the Strehl ratio is the environment variable most correlated to the contrast, it is insufficient to select similar images. We also show that having multiple reference stars in the reference library produces better results than using a single well-chosen reference star.Conclusions. Using the Pearson correlation computed on a specific area of interest to select reference frames is a promising alternative to improve the detectability of faint point-sources when applying reference star differential imaging. In the future, reducing all the data available in the SPHERE archive using this technique might offer interesting results in the search for previously undetected planets.
背景。高对比度成像观测主要依靠角差分成像，这是一种成功的探测点源（如行星）的技术。然而，在恒星附近（通常低于 300mas），如果没有足够的场旋转，这种技术就会受到信号自减的影响。从档案数据中建立大型参考恒星库，然后用于优化减去恒星晕，这是一种强大的技术，被称为参考恒星差分成像（RSDI），可以克服这一局限。我们的目的是研究在对 VLT/SPHERE 数据进行参考星差分成像时创建由多颗恒星组成的参考库的新方法。为此，我们使用了 SPHERE 高角分辨率碎片盘巡天（SHARDDS）的数据集，该数据集由 2015-2016 年期间用红外双波段成像仪和摄谱仪（IRDIS）在宽波段 H 波段观测到的 55 个目标组成，共约 20 000 帧。我们将HD 206893作为一个基准科学目标，以展示这种方法所提供的更高灵敏度。我们根据不同的图像相似性指标创建了参考帧库：卷积神经网络创建的描述符之间的余弦距离、皮尔逊相关系数、结构相似性指数、Strehl 比率和原始对比度标准。我们使用主成分分析（PCA）来减去恒星光环，并测试了各种归一化选项。我们使用皮尔逊相关系数（PCC）对 245 至 612 马斯之间的环形区域进行筛选，从而在 HD 206893 B 上获得了最佳信噪比（S/N）。在亚恒星伴星HD 206893 B上信噪比最高的十个参考库都是基于皮尔逊相关系数方法，优于其他相似性指标。虽然施特莱尔比是与对比度最相关的环境变量，但它不足以选出相似的图像。我们还表明，在参考库中拥有多个参考星比使用一个精心挑选的参考星能产生更好的结果。在应用参考星差分成像时，使用在特定感兴趣区域计算的皮尔逊相关性来选择参考帧是提高微弱点源可探测性的一种有前途的替代方法。今后，利用这种技术减少 SPHERE 档案中的所有可用数据，可能会为寻找以前未探测到的行星提供有趣的结果。
{"title":"Multiple reference star differential imaging with VLT/SPHERE","authors":"C. Romero, J. Milli, A.-M. Lagrange, R. De Rosa, S. Ertel, C. del Burgo","doi":"10.1051/0004-6361/202346361","DOIUrl":"https://doi.org/10.1051/0004-6361/202346361","url":null,"abstract":"<i>Context<i/>. High-contrast imaging observations mostly rely on angular differential imaging, a successful technique for detecting point-sources, such as planets. However, in the vicinity of the star (typically below 300 mas), this technique suffers from signal self-subtraction when there is not enough field rotation. Building large libraries of reference stars from archival data later used to optimally subtract the stellar halo is a powerful technique known as reference star differential imaging (RSDI) that can overcome this limitation.<i>Aims<i/>. We aim at investigating new methods for creating reference libraries composed of multiple stars when applying reference star differential imaging to VLT/SPHERE data. We used for that purpose a data set from the SPHERE High Angular Resolution Debris Disk Survey (SHARDDS), composed of 55 targets observed in broad-band H with the InfraRed Dual-band Imager and Spectrograph (IRDIS) during 2015-2016, with a total of ~20 000 frames. We consider HD 206893, known to host a close-in bound substellar companion HD 206893 B, as a benchmark science target to demonstrate the improved sensitivity provided by this method.<i>Methods<i/>. We created libraries of reference frames based on different image similarity metrics: the cosine distance between descriptors created by a convolutional neural network, the Pearson correlation coefficient, the Structural Similarity Index, the Strehl ratio, and raw contrast criteria. We used principal component analysis (PCA) to subtract the stellar halo and tested various normalization options.<i>Results<i/>. We obtained the best signal-to-noise ratio (S/N) on HD 206893 B by using the Pearson correlation coefficient (PCC) applied to an annulus between 245 and 612 mas to select reference frames. The ten reference libraries with the highest S/N on the substellar companion HD 206893 B were all based on the PCC method, outperforming other similarity metrics. While the Strehl ratio is the environment variable most correlated to the contrast, it is insufficient to select similar images. We also show that having multiple reference stars in the reference library produces better results than using a single well-chosen reference star.<i>Conclusions<i/>. Using the Pearson correlation computed on a specific area of interest to select reference frames is a promising alternative to improve the detectability of faint point-sources when applying reference star differential imaging. In the future, reducing all the data available in the SPHERE archive using this technique might offer interesting results in the search for previously undetected planets.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"250 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670328","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}
Pub Date : 2024-11-18DOI: 10.1088/1361-6382/ad84ae
Collin D Capano, Jahed Abedi, Shilpa Kastha, Alexander H Nitz, Julian Westerweck, Yi-Fan Wang, Miriam Cabero, Alex B Nielsen and Badri Krishnan
A major aim of gravitational wave astronomy is to test observationally the Kerr nature of black holes. The strongest such test, with minimal additional assumptions, is provided by observations of multiple ringdown modes, also known as black hole spectroscopy. For the gravitational wave merger event GW190521, we have previously claimed the detection of two ringdown modes emitted by the remnant black hole. In this paper we provide further evidence for the detection of multiple ringdown modes from this event. We analyse the recovery of simulated gravitational wave signals designed to replicate the ringdown properties of GW190521. We quantify how often our detection statistic reports strong evidence for a sub-dominant ringdown mode, even when no such mode is present in the simulated signal. We find this only occurs with a probability ∼0.02, which is consistent with a Bayes factor of (1σ uncertainty) found for GW190521. We also quantify our agnostic analysis of GW190521, in which no relationship is assumed between ringdown modes, and find that only 1 in 250 simulated signals without a mode yields a result as significant as GW190521. Conversely, we verify that when simulated signals do have an observable mode they consistently yield a strong evidence and significant agnostic results. We also find that constraints on deviations from the mode on GW190521-like signals with a mode are consistent with what was obtained from our previous analysis of GW190521. Our results support our previous conclusion that the gravitational wave signal from GW190521 contains an observable sub-dominant mode.
{"title":"Estimating false alarm rates of sub-dominant quasi-normal modes in GW190521","authors":"Collin D Capano, Jahed Abedi, Shilpa Kastha, Alexander H Nitz, Julian Westerweck, Yi-Fan Wang, Miriam Cabero, Alex B Nielsen and Badri Krishnan","doi":"10.1088/1361-6382/ad84ae","DOIUrl":"https://doi.org/10.1088/1361-6382/ad84ae","url":null,"abstract":"A major aim of gravitational wave astronomy is to test observationally the Kerr nature of black holes. The strongest such test, with minimal additional assumptions, is provided by observations of multiple ringdown modes, also known as black hole spectroscopy. For the gravitational wave merger event GW190521, we have previously claimed the detection of two ringdown modes emitted by the remnant black hole. In this paper we provide further evidence for the detection of multiple ringdown modes from this event. We analyse the recovery of simulated gravitational wave signals designed to replicate the ringdown properties of GW190521. We quantify how often our detection statistic reports strong evidence for a sub-dominant ringdown mode, even when no such mode is present in the simulated signal. We find this only occurs with a probability ∼0.02, which is consistent with a Bayes factor of (1σ uncertainty) found for GW190521. We also quantify our agnostic analysis of GW190521, in which no relationship is assumed between ringdown modes, and find that only 1 in 250 simulated signals without a mode yields a result as significant as GW190521. Conversely, we verify that when simulated signals do have an observable mode they consistently yield a strong evidence and significant agnostic results. We also find that constraints on deviations from the mode on GW190521-like signals with a mode are consistent with what was obtained from our previous analysis of GW190521. Our results support our previous conclusion that the gravitational wave signal from GW190521 contains an observable sub-dominant mode.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"33 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Prebiotic synthesis of complex organic molecules in water-rich environments has been a long-standing challenge. In the modern deep sea, emission of liquid CO2 has been observed in multiple locations, which indicates the existence of benthic CO2 pools. Recently, a liquid/supercritical CO2 (ScCO2) hypothesis has been proposed that a two-phase ScCO2-water environment could lead to efficient dehydration and condensation of organics. To confirm this hypothesis, we conducted a nucleoside phosphorylation reaction in a hydrothermal reactor creating ScCO2-water two-phase environment. After 120 h of uridine, cytosine, guanosine, and adenosine phosphorylation at 68.9°C, various nucleoside monophosphates (NMPs), nucleotide diphosphates, and carbamoyl nucleosides were produced. The addition of urea enhanced the overall production of phosphorylated species with 5'-NMPs, the major products that reached over 10% yield. As predicted, phosphorylation did not proceed in the fully aqueous environment without ScCO2. Further, a glass window reactor was introduced for direct observation of the two-phase environment, where the escape of water into the ScCO2 phase was observed. These results are similar to those of a wet-dry cycle experiment simulating the terrestrial hot spring environment, indicating that the presence of ScCO2 can create a comparatively dry condition in the deep sea. In addition, the high acidity present in the aqueous phase further supports nucleotide synthesis by enabling the release of orthophosphate from the hydroxyapatite mineral solving the phosphate problem. Thus, the present study highlights the potential of the unique ScCO2-water two-phase environment to drive prebiotic nucleotide synthesis and likely induce condensation reactions of various organic and inorganic compounds in the deep-sea CO2 pool on Earth and potentially other ocean worlds.
{"title":"Prebiotic Nucleoside Phosphorylation in a Simulated Deep-Sea Supercritical Carbon Dioxide-Water Two-Phase Environment.","authors":"Shotaro Tagawa, Ryota Hatami, Kohei Morino, Shohei Terazawa, Caner Akıl, Kristin Johnson-Finn, Takazo Shibuya, Kosuke Fujishima","doi":"10.1089/ast.2024.0016","DOIUrl":"https://doi.org/10.1089/ast.2024.0016","url":null,"abstract":"<p><p>Prebiotic synthesis of complex organic molecules in water-rich environments has been a long-standing challenge. In the modern deep sea, emission of liquid CO<sub>2</sub> has been observed in multiple locations, which indicates the existence of benthic CO<sub>2</sub> pools. Recently, a liquid/supercritical CO<sub>2</sub> (ScCO<sub>2</sub>) hypothesis has been proposed that a two-phase ScCO<sub>2</sub>-water environment could lead to efficient dehydration and condensation of organics. To confirm this hypothesis, we conducted a nucleoside phosphorylation reaction in a hydrothermal reactor creating ScCO<sub>2</sub>-water two-phase environment. After 120 h of uridine, cytosine, guanosine, and adenosine phosphorylation at 68.9°C, various nucleoside monophosphates (NMPs), nucleotide diphosphates, and carbamoyl nucleosides were produced. The addition of urea enhanced the overall production of phosphorylated species with 5'-NMPs, the major products that reached over 10% yield. As predicted, phosphorylation did not proceed in the fully aqueous environment without ScCO<sub>2</sub>. Further, a glass window reactor was introduced for direct observation of the two-phase environment, where the escape of water into the ScCO<sub>2</sub> phase was observed. These results are similar to those of a wet-dry cycle experiment simulating the terrestrial hot spring environment, indicating that the presence of ScCO<sub>2</sub> can create a comparatively dry condition in the deep sea. In addition, the high acidity present in the aqueous phase further supports nucleotide synthesis by enabling the release of orthophosphate from the hydroxyapatite mineral solving the phosphate problem. Thus, the present study highlights the potential of the unique ScCO<sub>2</sub>-water two-phase environment to drive prebiotic nucleotide synthesis and likely induce condensation reactions of various organic and inorganic compounds in the deep-sea CO<sub>2</sub> pool on Earth and potentially other ocean worlds.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142667024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2024-11-18DOI: 10.1051/0004-6361/202451396
L. Mousset, E. Allys, M. A. Price, J. Aumont, J.-M. Delouis, L. Montier, J. D. McEwen
Scattering transforms are a new type of summary statistics recently developed for the study of highly non-Gaussian processes, which have been shown to be very promising for astrophysical studies. In particular, they allow one to build generative models of complex non-linear fields from a limited amount of data and have been used as the basis of new statistical component separation algorithms. In the context of upcoming cosmological surveys, such as LiteBIRD for the cosmic microwave background polarisation or the Vera C. Rubin Observatory and the Euclid space telescope for study of the large-scale structures of the Universe, extending these tools to spherical data is necessary. In this work, we developed scattering transforms on the sphere and focused on the construction of maximum-entropy generative models of several astrophysical fields. We constructed, from a single target field, generative models of homogeneous astrophysical and cosmological fields, whose samples were quantitatively compared to the target fields using common statistics (power spectrum, pixel probability density function, and Minkowski functionals). Our sampled fields agree well with the target fields, both statistically and visually. We conclude, therefore, that these generative models open up a wide range of new applications for future astrophysical and cosmological studies, particularly those for which very little simulated data is available.
散射变换是最近为研究高度非高斯过程而开发的一种新型汇总统计，已被证明在天体物理研究中大有可为。特别是，它们允许人们从有限的数据量中建立复杂非线性场的生成模型，并被用作新的统计成分分离算法的基础。在即将开展的宇宙学调查中，如用于宇宙微波背景极化的 LiteBIRD 或用于研究宇宙大尺度结构的 Vera C. Rubin 天文台和 Euclid 空间望远镜，有必要将这些工具扩展到球形数据。在这项工作中，我们开发了球面散射变换，并重点构建了几个天体物理场的最大熵生成模型。我们从单个目标场构建了同质天体物理场和宇宙学场的生成模型，并使用通用统计（功率谱、像素概率密度函数和闵科夫斯基函数）将其样本与目标场进行了定量比较。我们的采样场与目标场在统计和视觉上都非常吻合。因此，我们得出结论，这些生成模型为未来的天体物理学和宇宙学研究开辟了广泛的新应用领域，尤其是那些模拟数据非常少的领域。
{"title":"Generative models of astrophysical fields with scattering transforms on the sphere","authors":"L. Mousset, E. Allys, M. A. Price, J. Aumont, J.-M. Delouis, L. Montier, J. D. McEwen","doi":"10.1051/0004-6361/202451396","DOIUrl":"https://doi.org/10.1051/0004-6361/202451396","url":null,"abstract":"Scattering transforms are a new type of summary statistics recently developed for the study of highly non-Gaussian processes, which have been shown to be very promising for astrophysical studies. In particular, they allow one to build generative models of complex non-linear fields from a limited amount of data and have been used as the basis of new statistical component separation algorithms. In the context of upcoming cosmological surveys, such as LiteBIRD for the cosmic microwave background polarisation or the <i>Vera C. Rubin<i/> Observatory and the <i>Euclid<i/> space telescope for study of the large-scale structures of the Universe, extending these tools to spherical data is necessary. In this work, we developed scattering transforms on the sphere and focused on the construction of maximum-entropy generative models of several astrophysical fields. We constructed, from a single target field, generative models of homogeneous astrophysical and cosmological fields, whose samples were quantitatively compared to the target fields using common statistics (power spectrum, pixel probability density function, and Minkowski functionals). Our sampled fields agree well with the target fields, both statistically and visually. We conclude, therefore, that these generative models open up a wide range of new applications for future astrophysical and cosmological studies, particularly those for which very little simulated data is available.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"17 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670333","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}
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