Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad1dd5
S. Lyu, Yuming Wang, Xiaolei Li, Quanhao Zhang, Jiajia Liu
Based on the Heliospheric Imager-1 images of the STEREO twin spacecraft, we established the CORrelation-Aided Reconstruction (CORAR) technique to locate and reconstruct the 3D structures of solar wind transients in interplanetary space. Here, we extend the CORAR method to images of COR2 on board STEREO to study the evolution of small-scale transients in the outer corona from 2010 January to May. We confirm that the transients can be located and reconstructed well by comparing the results with those of a self-similar expanding model. The speed distribution of the reconstructed transients generally shows the typical characteristics of the slow solar wind. We further study the sources of the transients on the Sun, and find that most reconstructed transients are located near the top of streamer belts or the heliospheric current sheet and can be tracked back to the boundaries of the closed-field and open-field regions along the field lines extrapolated by corona models. The formation mechanisms of these transients in the slow solar wind are also discussed.
{"title":"Inferring the Solar Wind Velocity in the Outer Corona Based on Multiview Observations of Small-scale Transients by STEREO/COR2","authors":"S. Lyu, Yuming Wang, Xiaolei Li, Quanhao Zhang, Jiajia Liu","doi":"10.3847/1538-4357/ad1dd5","DOIUrl":"https://doi.org/10.3847/1538-4357/ad1dd5","url":null,"abstract":"\u0000 Based on the Heliospheric Imager-1 images of the STEREO twin spacecraft, we established the CORrelation-Aided Reconstruction (CORAR) technique to locate and reconstruct the 3D structures of solar wind transients in interplanetary space. Here, we extend the CORAR method to images of COR2 on board STEREO to study the evolution of small-scale transients in the outer corona from 2010 January to May. We confirm that the transients can be located and reconstructed well by comparing the results with those of a self-similar expanding model. The speed distribution of the reconstructed transients generally shows the typical characteristics of the slow solar wind. We further study the sources of the transients on the Sun, and find that most reconstructed transients are located near the top of streamer belts or the heliospheric current sheet and can be tracked back to the boundaries of the closed-field and open-field regions along the field lines extrapolated by corona models. The formation mechanisms of these transients in the slow solar wind are also discussed.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"36 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140463589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad18bd
M. Korsós, R. Jarolim, R. Erdélyi, Astrid M. Veronig, Huw Morgan, F. Zuccarello
The three-dimensional (3D) coronal magnetic field has not yet been directly observed. However, for a better understanding and prediction of magnetically driven solar eruptions, 3D models of solar active regions are required. This work aims to provide insight into the significance of different extrapolation models for analyzing the preeruptive conditions of active regions with morphological parameters in 3D. Here, we employed potential field (PF), linear force-free field (LFFF), and nonlinear force-free field (NLFFF) models and a neural network-based method integrating observational data and NLFFF physics (NF2). The 3D coronal magnetic field structure of a “flaring” (AR11166) and “flare-quiet” (AR12645) active region, in terms of their flare productivity, is constructed via the four extrapolation methods. To analyze the evolution of the field, six prediction parameters were employed throughout, from the photosphere up to the base of the lower corona. First, we find that the evolution of the adopted morphological parameters exhibits similarity across the investigated time period when considering the four types of extrapolations. Second, all the parameters exhibited preeruptive conditions not only at the photosphere but also at higher altitudes in the case of active region (AR) 11166, while three out of the six proxies also exhibited preeruptive conditions in the case of AR12645. We conclude that: (i) the combined application of several different precursor parameters is important in the lower solar atmosphere to improve eruption predictions, and (ii) to gain a quick yet reliable insight into the preflare evolution of active regions in 3D, the PF and LFFF are acceptable; however, the NF2 method is likely the more suitable option.
{"title":"First Insights into the Applicability and Importance of Different 3D Magnetic Field Extrapolation Approaches for Studying the Preeruptive Conditions of Solar Active Regions","authors":"M. Korsós, R. Jarolim, R. Erdélyi, Astrid M. Veronig, Huw Morgan, F. Zuccarello","doi":"10.3847/1538-4357/ad18bd","DOIUrl":"https://doi.org/10.3847/1538-4357/ad18bd","url":null,"abstract":"\u0000 The three-dimensional (3D) coronal magnetic field has not yet been directly observed. However, for a better understanding and prediction of magnetically driven solar eruptions, 3D models of solar active regions are required. This work aims to provide insight into the significance of different extrapolation models for analyzing the preeruptive conditions of active regions with morphological parameters in 3D. Here, we employed potential field (PF), linear force-free field (LFFF), and nonlinear force-free field (NLFFF) models and a neural network-based method integrating observational data and NLFFF physics (NF2). The 3D coronal magnetic field structure of a “flaring” (AR11166) and “flare-quiet” (AR12645) active region, in terms of their flare productivity, is constructed via the four extrapolation methods. To analyze the evolution of the field, six prediction parameters were employed throughout, from the photosphere up to the base of the lower corona. First, we find that the evolution of the adopted morphological parameters exhibits similarity across the investigated time period when considering the four types of extrapolations. Second, all the parameters exhibited preeruptive conditions not only at the photosphere but also at higher altitudes in the case of active region (AR) 11166, while three out of the six proxies also exhibited preeruptive conditions in the case of AR12645. We conclude that: (i) the combined application of several different precursor parameters is important in the lower solar atmosphere to improve eruption predictions, and (ii) to gain a quick yet reliable insight into the preflare evolution of active regions in 3D, the PF and LFFF are acceptable; however, the NF2 method is likely the more suitable option.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"44 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140464651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad21fd
E. M. Wraback, A. P. Hoffmann, W. Manchester, I. V. Sokolov, B. van der Holst, D. Carpenter
We used the stream-aligned magnetohydrodynamics (SA-MHD) model to simulate Carrington rotation 2210, which contains Parker Solar Probe’s (PSP) first perihelion at 36.5 R ⊙ on 2018 November 6, to provide context to the in situ PSP observations by FIELDS and SWEAP. The SA-MHD model aligns the magnetic field with the velocity vector at each point, thereby allowing for clear connectivity between the spacecraft and the source regions on the Sun, without unphysical magnetic field structures. During this Carrington rotation, two stream interaction regions (SIRs) form, due to the deep solar minimum. We include the energy partitioning of the parallel and perpendicular ions and the isotropic electrons to investigate the temperature anisotropy through the compression regions to better understand the wave energy amplification and proton thermal energy partitioning in a global context. Overall, we found good agreement in all in situ plasma parameters between the SA-MHD results and the observations at PSP, STEREO-A, and Earth, including at PSP’s perihelion and through the compression region of the SIRs. In the typical solar wind, the parallel proton temperature is preferentially heated, except in the SIR, where there is an enhancement in the perpendicular proton temperature. This is further showcased in the ion cyclotron relaxation time, which shows a distinct decrease through the SIR compression regions. This work demonstrates the success of the Alfvén wave turbulence theory for predicting interplanetary magnetic turbulence levels, while self-consistently reproducing solar wind speeds, densities, and overall temperatures, including at small heliocentric distances and through SIR compression regions.
我们使用流对齐磁流体力学（SA-MHD）模型模拟了卡灵顿自转2210，其中包含帕克太阳探测器（PSP）于2018年11月6日在36.5 R ⊙处的首次近日点，为FIELDS和SWEAP的现场PSP观测提供背景资料。SA-MHD模型将磁场与每个点的速度矢量对齐，从而使航天器与太阳上的源区之间具有清晰的连接，而不会出现非物理的磁场结构。在这次卡林顿旋转期间，由于太阳深度极小，形成了两个流相互作用区（SIR）。我们将平行和垂直离子以及各向同性电子的能量分配纳入研究范围，以调查压缩区域的温度各向异性，从而更好地理解波能放大和质子热能分配的全局背景。总之，我们发现 SA-MHD 结果与在 PSP、STEREO-A 和地球上观测到的所有原位等离子体参数都非常吻合，包括在 PSP 的近日点和 SIR 的压缩区域。在典型的太阳风中，平行质子温度优先被加热，但在 SIR 中除外，因为在 SIR 中垂直质子温度被提高。离子回旋弛豫时间进一步证明了这一点，在 SIR 压缩区域，离子回旋弛豫时间明显减少。这项工作证明了阿尔芬波湍流理论在预测行星际磁湍流水平方面的成功，同时自洽地再现了太阳风的速度、密度和总体温度，包括在较小的日心距离和通过 SIR 压缩区时的情况。
{"title":"Simulating Compressive Stream Interaction Regions during Parker Solar Probe’s First Perihelion Using Stream-aligned Magnetohydrodynamics","authors":"E. M. Wraback, A. P. Hoffmann, W. Manchester, I. V. Sokolov, B. van der Holst, D. Carpenter","doi":"10.3847/1538-4357/ad21fd","DOIUrl":"https://doi.org/10.3847/1538-4357/ad21fd","url":null,"abstract":"\u0000 We used the stream-aligned magnetohydrodynamics (SA-MHD) model to simulate Carrington rotation 2210, which contains Parker Solar Probe’s (PSP) first perihelion at 36.5 R\u0000 ⊙ on 2018 November 6, to provide context to the in situ PSP observations by FIELDS and SWEAP. The SA-MHD model aligns the magnetic field with the velocity vector at each point, thereby allowing for clear connectivity between the spacecraft and the source regions on the Sun, without unphysical magnetic field structures. During this Carrington rotation, two stream interaction regions (SIRs) form, due to the deep solar minimum. We include the energy partitioning of the parallel and perpendicular ions and the isotropic electrons to investigate the temperature anisotropy through the compression regions to better understand the wave energy amplification and proton thermal energy partitioning in a global context. Overall, we found good agreement in all in situ plasma parameters between the SA-MHD results and the observations at PSP, STEREO-A, and Earth, including at PSP’s perihelion and through the compression region of the SIRs. In the typical solar wind, the parallel proton temperature is preferentially heated, except in the SIR, where there is an enhancement in the perpendicular proton temperature. This is further showcased in the ion cyclotron relaxation time, which shows a distinct decrease through the SIR compression regions. This work demonstrates the success of the Alfvén wave turbulence theory for predicting interplanetary magnetic turbulence levels, while self-consistently reproducing solar wind speeds, densities, and overall temperatures, including at small heliocentric distances and through SIR compression regions.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"108 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140465336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad1932
F. Maeda, F. Egusa, A. Tsujita, Shuhei Inoue, K. Kohno, S. Komugi, K. Ohta, Yoshihisa Asada, Y. Fujimoto, A. Habe, B. Hatsukade, Shin Inoue, Hiroyuki Kaneko, Masato I. N. Kobayashi, T. Tosaki
The tip of the tidal tail, resulting from an encounter between galaxies, features gas concentrations and some star-forming regions, such as tidal dwarf galaxies (TDGs). This region provides a unique laboratory for examining the star formation process in a dynamical environment distinct from that of disk galaxies. Using the Nobeyama 45 m telescope, we conducted 12CO(1−0) position-switching observations at the tips of the southern tidal tail in the Antennae galaxies. We detected CO emission not only from the two star-forming TDG candidates but also in regions with no significant star formation. Adopting a Galactic CO-to-H2 conversion factor without helium correction, the H2 gas surface density is ∼5–12 M ⊙ pc−2. In most regions, the molecular-to-atomic gas ratio is around unity (0.6–1.9), but we find a region with a high ratio with a 3σ lower limit of >7.2. The star formation efficiency (SFE) of molecular gas is notably low (<0.15 Gyr−1), indicating less active star formation than in both nearby disk galaxies (∼0.5–1.0 Gyr−1) and other TDGs previously observed. Including previous observations, the molecular gas SFEs vary widely among TDGs/tidal tails, from 10−2 to 10 Gyr−1, demonstrating significant variations in star formation activity. Potential factors contributing to the low SFE in the Antennae tail tips include extensive tides and/or the young age of the tail.
潮汐尾部的顶端是星系间相遇产生的，那里有气体聚集区和一些恒星形成区，如潮汐矮星系（TDGs）。这一区域为研究不同于盘状星系的动力学环境中的恒星形成过程提供了一个独特的实验室。我们利用野边山 45 米望远镜，在天线星系南部潮汐尾端进行了 12CO(1-0)位置切换观测。我们不仅在两个恒星形成的 TDG 候选星系中探测到了 CO 辐射，而且在没有明显恒星形成的区域也探测到了 CO 辐射。采用不含氦校正的银河 CO-H2 换算系数，H2 气体表面密度为 ∼5-12 M ⊙ pc-2。在大多数区域，分子-原子气体比约为 1（0.6-1.9），但我们发现一个区域的分子-原子气体比很高，其 3σ 下限大于 7.2。分子气体的恒星形成效率（SFE）明显偏低（＜0.15 Gyr-1），表明恒星形成的活跃程度低于附近的盘状星系（∼0.5-1.0 Gyr-1）和之前观测到的其他TDG。包括以前的观测在内，不同TDGs/潮汐尾部的分子气体SFEs差异很大，从10-2到10 Gyr-1不等，这表明恒星形成的活跃程度存在很大差异。导致天线尾端 SFE 值较低的潜在因素包括广泛的潮汐和/或尾端年龄较小。
{"title":"Detection of CO(1−0) Emission at the Tips of the Tidal Tail in the Antennae Galaxies","authors":"F. Maeda, F. Egusa, A. Tsujita, Shuhei Inoue, K. Kohno, S. Komugi, K. Ohta, Yoshihisa Asada, Y. Fujimoto, A. Habe, B. Hatsukade, Shin Inoue, Hiroyuki Kaneko, Masato I. N. Kobayashi, T. Tosaki","doi":"10.3847/1538-4357/ad1932","DOIUrl":"https://doi.org/10.3847/1538-4357/ad1932","url":null,"abstract":"\u0000 The tip of the tidal tail, resulting from an encounter between galaxies, features gas concentrations and some star-forming regions, such as tidal dwarf galaxies (TDGs). This region provides a unique laboratory for examining the star formation process in a dynamical environment distinct from that of disk galaxies. Using the Nobeyama 45 m telescope, we conducted 12CO(1−0) position-switching observations at the tips of the southern tidal tail in the Antennae galaxies. We detected CO emission not only from the two star-forming TDG candidates but also in regions with no significant star formation. Adopting a Galactic CO-to-H2 conversion factor without helium correction, the H2 gas surface density is ∼5–12 M\u0000 ⊙ pc−2. In most regions, the molecular-to-atomic gas ratio is around unity (0.6–1.9), but we find a region with a high ratio with a 3σ lower limit of >7.2. The star formation efficiency (SFE) of molecular gas is notably low (<0.15 Gyr−1), indicating less active star formation than in both nearby disk galaxies (∼0.5–1.0 Gyr−1) and other TDGs previously observed. Including previous observations, the molecular gas SFEs vary widely among TDGs/tidal tails, from 10−2 to 10 Gyr−1, demonstrating significant variations in star formation activity. Potential factors contributing to the low SFE in the Antennae tail tips include extensive tides and/or the young age of the tail.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"39 32","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139683961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad17be
Priyanka Chakraborty, Rachel Hemmer, Adam R. Foster, J. Raymond, Arnab Sarkar, Randall K. Smith, Nancy Brickhouse
Accurate atomic data and plasma models are essential for interpreting the upcoming high-quality spectra from missions like XRISM and Athena. Estimating physical quantities, like temperature, abundance, turbulence, and the resonance scattering factor, is highly dependent on the underlying atomic data. We use the AtomDB tool variableapec to estimate the impact of atomic data uncertainties in Einstein A coefficients, collisional rate coefficients, and the ionization and recombination rates of H-, He-, and Li-like iron in modeling the spectrum of Perseus observed by Hitomi. The best-fit temperatures, abundances, resonance scattering factors, and turbulence parameters including atomic data uncertainties vary by approximately 17%, 35%, 30%, and 3%, respectively, from the best-fit temperatures, abundances, RS factors, and turbulence parameters estimated without atomic data uncertainties. These indicate that approximately 32%, 35%, and 25% of the best-fit temperatures, abundances, and resonance scattering factors when including uncertainties lie outside the 3σ error regions of their corresponding best-fit values computed with zero atomic data errors. Expanding the energy range to 1.8–20.0 keV shows less variability, with 26% of the abundances and 22% of the resonance scattering factors lying outside the 3σ errors of the best-fit values. We also studied correlations between physical parameters and atomic rate uncertainties to identify key atomic quantities requiring precise lab measurements. We report negative correlations between the best-fit temperatures and the z (1s2s 3S1 → 1s2) collisional rate coefficients, abundances and y (1s2p 3P1 → 1s2) collisional rate coefficients, and abundances and z collisional rate coefficients, and a positive correlation between the resonance scattering factors and the w (1s2p 1P1 → 1s2) collisional rate coefficients.
{"title":"Investigating the Impact of Atomic Data Uncertainties on the Measured Physical Parameters of the Perseus Galaxy Cluster","authors":"Priyanka Chakraborty, Rachel Hemmer, Adam R. Foster, J. Raymond, Arnab Sarkar, Randall K. Smith, Nancy Brickhouse","doi":"10.3847/1538-4357/ad17be","DOIUrl":"https://doi.org/10.3847/1538-4357/ad17be","url":null,"abstract":"\u0000 Accurate atomic data and plasma models are essential for interpreting the upcoming high-quality spectra from missions like XRISM and Athena. Estimating physical quantities, like temperature, abundance, turbulence, and the resonance scattering factor, is highly dependent on the underlying atomic data. We use the AtomDB tool variableapec to estimate the impact of atomic data uncertainties in Einstein A coefficients, collisional rate coefficients, and the ionization and recombination rates of H-, He-, and Li-like iron in modeling the spectrum of Perseus observed by Hitomi. The best-fit temperatures, abundances, resonance scattering factors, and turbulence parameters including atomic data uncertainties vary by approximately 17%, 35%, 30%, and 3%, respectively, from the best-fit temperatures, abundances, RS factors, and turbulence parameters estimated without atomic data uncertainties. These indicate that approximately 32%, 35%, and 25% of the best-fit temperatures, abundances, and resonance scattering factors when including uncertainties lie outside the 3σ error regions of their corresponding best-fit values computed with zero atomic data errors. Expanding the energy range to 1.8–20.0 keV shows less variability, with 26% of the abundances and 22% of the resonance scattering factors lying outside the 3σ errors of the best-fit values. We also studied correlations between physical parameters and atomic rate uncertainties to identify key atomic quantities requiring precise lab measurements. We report negative correlations between the best-fit temperatures and the z (1s2s 3S1 → 1s2) collisional rate coefficients, abundances and y (1s2p 3P1 → 1s2) collisional rate coefficients, and abundances and z collisional rate coefficients, and a positive correlation between the resonance scattering factors and the w (1s2p 1P1 → 1s2) collisional rate coefficients.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"870 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140469424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad2204
J. Ng, N. Bessho, J. Dahlin, L.-J. Chen
Numerous structures conducive to magnetic reconnection are frequently observed in the turbulent regions at quasi-parallel shocks. In this work, we use a particle-in-cell simulation to study 3D magnetic reconnection in shock turbulence. We identify and characterize magnetic null points, and focus on reconnection along the separator between them. We identify a reconnection region with strong parallel current, a finite parallel potential, and counterrotating electron flows. Electrons are shown to be accelerated by the parallel electric field before being scattered at the null.
{"title":"Reconnection along a Separator in Shock Turbulence","authors":"J. Ng, N. Bessho, J. Dahlin, L.-J. Chen","doi":"10.3847/1538-4357/ad2204","DOIUrl":"https://doi.org/10.3847/1538-4357/ad2204","url":null,"abstract":"\u0000 Numerous structures conducive to magnetic reconnection are frequently observed in the turbulent regions at quasi-parallel shocks. In this work, we use a particle-in-cell simulation to study 3D magnetic reconnection in shock turbulence. We identify and characterize magnetic null points, and focus on reconnection along the separator between them. We identify a reconnection region with strong parallel current, a finite parallel potential, and counterrotating electron flows. Electrons are shown to be accelerated by the parallel electric field before being scattered at the null.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"129 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140462903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad1602
Z. Chen 陈, Keming 可名 Zhang 张, Benjamin F. Williams, M. Durbin
deepCR is a deep-learning-based cosmic-ray (CR) rejection framework originally presented by Zhang & Bloom. The original approach requires a dedicated training set that consists of multiple frames of the same fields, enabling automatic CR labeling through comparison with their median coadds. Here, we present a novel training approach that circumvents the need for a dedicated training set, but instead utilizes dark frames and the science images requiring CR removal themselves. During training, CRs present in dark frames are added to the science images, which the network is then trained to identify. In turn, the trained deepCR model can then be applied to identify CRs originally present in the science images. Using this approach, we present a new deepCR model trained on a diverse set of Hubble Space Telescope images taken from resolved galaxies in the Local Group, which is universally applicable across all WFC3/UVIS filters. We introduce a robust approach to determining the threshold for generating binary cosmic-ray masks from predictions from deepCR probability maps. When applied to the Panchromatic Hubble Andromeda Southern Treasury survey, our new deepCR model added ∼7% of good-quality stars that exhibit distinct features in their color–magnitude diagrams.
{"title":"A New Cosmic-Ray Rejection Routine for HST WFC3/UVIS via Label-free Training of deepCR","authors":"Z. Chen 陈, Keming 可名 Zhang 张, Benjamin F. Williams, M. Durbin","doi":"10.3847/1538-4357/ad1602","DOIUrl":"https://doi.org/10.3847/1538-4357/ad1602","url":null,"abstract":"\u0000 \u0000 deepCR is a deep-learning-based cosmic-ray (CR) rejection framework originally presented by Zhang & Bloom. The original approach requires a dedicated training set that consists of multiple frames of the same fields, enabling automatic CR labeling through comparison with their median coadds. Here, we present a novel training approach that circumvents the need for a dedicated training set, but instead utilizes dark frames and the science images requiring CR removal themselves. During training, CRs present in dark frames are added to the science images, which the network is then trained to identify. In turn, the trained deepCR model can then be applied to identify CRs originally present in the science images. Using this approach, we present a new deepCR model trained on a diverse set of Hubble Space Telescope images taken from resolved galaxies in the Local Group, which is universally applicable across all WFC3/UVIS filters. We introduce a robust approach to determining the threshold for generating binary cosmic-ray masks from predictions from deepCR probability maps. When applied to the Panchromatic Hubble Andromeda Southern Treasury survey, our new deepCR model added ∼7% of good-quality stars that exhibit distinct features in their color–magnitude diagrams.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"32 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139684667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad22da
Anna Taylor, Audrey Dunn, Sarah Peacock, A. Youngblood, Seth Redfield
The Mg ii h&k emission lines (2803, 2796 Å) are a useful tool for understanding stellar chromospheres and transition regions due to their intrinsic brightness, relatively low interstellar medium (ISM) absorption interference, and abundance of archival spectra available. Similar to other optically thick chromospheric emission lines such as H i Lyα, Mg ii emissions commonly present with a self-reversed line core, the depth and shape of which vary from star to star. We explore the relationship between self-reversal and the stellar atmosphere by investigating the extent to which fundamental stellar parameters affect self-reversal. We present a search for correlations between photospheric parameters such as effective temperature, surface gravity, and metallicity with the Mg ii k self-reversal depth for a group of 135 FGKM main-sequence stars with high-resolution near-ultraviolet spectra from the Hubble Space Telescope. We modeled the observed Mg ii k line profiles to correct for ISM attenuation and recover the depth of the emission line’s self-reversal in relation to the intensity of the line. We used the PHOENIX atmosphere code to homogeneously determine the stellar parameters by computing a suite of stellar atmosphere models that include a chromosphere and transition region, and using archival photometry to guide the models of each star. We quantify the sensitivity of the visible and near-infrared photometry to chromospheric and photospheric parameters. We find weak trends between Mg ii k self-reversal depth and age, rotation period, Mg ii luminosity, temperature, and mass. All stars in our sample older than ∼2 Gyr or rotating slower than ∼10 days exhibit self-reversal.
Mg ii h&k 发射线（2803，2796 Å）是了解恒星色球层和过渡区的有用工具，因为它们具有固有亮度、相对较低的星际介质（ISM）吸收干扰以及丰富的档案光谱。与 H i Lyα 等其他光学厚层发射线类似，Mg ii 发射通常也有一个自反转线核，其深度和形状因恒星而异。我们通过研究基本恒星参数对自反转的影响程度，探索自反转与恒星大气之间的关系。我们利用哈勃太空望远镜的高分辨率近紫外光谱，对一组 135 颗 FGKM 主序恒星的光层参数（如有效温度、表面引力和金属性）与 Mg ii k 自反转深度之间的相关性进行了研究。我们对观测到的 Mg ii k 线剖面进行了建模，以校正 ISM 衰减并恢复发射线自反转深度与发射线强度的关系。我们使用 PHOENIX 大气层代码，通过计算一套包括色球层和过渡区在内的恒星大气层模型，并使用档案光度测量来指导每颗恒星的模型，从而均匀地确定恒星参数。我们量化了可见光和近红外光度测量对色球和光球参数的敏感性。我们发现 Mg ii k 自反转深度与年龄、自转周期、Mg ii 光度、温度和质量之间存在微弱的趋势。在我们的样本中，所有年龄大于 ∼2 Gyr 或自转速度慢于 ∼10 天的恒星都表现出了自反转。
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Pub Date : 2024-02-01DOI: 10.3847/1538-4357/ad1f67
G. Cao, Xiongbang Yang
We study the pulsar energy-dependent γ-ray light curves and spectra from curvature radiation in the dissipative magnetospheres. The dissipative magnetospheres with the combined force-free (FFE) and Aristotelian are computed by a pseudo-spectral method with a high-resolution simulation in the rotating coordinate system, which produces a near-FFE field structure with the dissipative region only near the equatorial current sheet outside the light cylinder. We use the test-particle trajectory method to compute the energy-dependent γ-ray light curves and phase-average and phase-resolved spectra by including both the accelerating electric field and radiation reaction. The predicted energy-dependent γ-ray light curves and spectra are then compared with those of the Vela pulsar observed by Fermi. Our results can generally reproduce the observed trends of the energy-dependent γ-ray light curves and spectra for the Vela pulsar.
{"title":"The Energy-dependent Gamma-Ray Light Curves and Spectra of the Vela Pulsar in the Dissipative Magnetospheres","authors":"G. Cao, Xiongbang Yang","doi":"10.3847/1538-4357/ad1f67","DOIUrl":"https://doi.org/10.3847/1538-4357/ad1f67","url":null,"abstract":"\u0000 We study the pulsar energy-dependent γ-ray light curves and spectra from curvature radiation in the dissipative magnetospheres. The dissipative magnetospheres with the combined force-free (FFE) and Aristotelian are computed by a pseudo-spectral method with a high-resolution simulation in the rotating coordinate system, which produces a near-FFE field structure with the dissipative region only near the equatorial current sheet outside the light cylinder. We use the test-particle trajectory method to compute the energy-dependent γ-ray light curves and phase-average and phase-resolved spectra by including both the accelerating electric field and radiation reaction. The predicted energy-dependent γ-ray light curves and spectra are then compared with those of the Vela pulsar observed by Fermi. Our results can generally reproduce the observed trends of the energy-dependent γ-ray light curves and spectra for the Vela pulsar.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"37 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140464070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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