Pub Date : 2024-01-31DOI: 10.3847/1538-4357/ad13e8
R. Yadav, Arvind K. Dattatrey, G. Rangwal, A. Subramaniam, D. Bisht, Ram Sagar
We present the study of four far-ultraviolet (FUV) bright stars in the field of the open cluster NGC 2420 using the Ultra Violet Imaging Telescope mounted on AstroSat. The three stars 525, 527, and 560 are members, while star 646 is a nonmember of the cluster. To characterize and determine the parameters of these stars, multiwavelength spectral energy distributions (SEDs) are analyzed using UV, optical, and IR data sets. For all four FUV bright stars, a two-component SED model fits well. Our findings indicate that two stars, 525 and 560, are binary blue straggler star (BSS) systems. These BSS systems may have formed in a tertiary system due to mass transfer from an evolved outer tertiary companion. Star 527 is a binary system of a BSS and an extremely low-mass (ELM) white dwarf, while star 646 is a binary system of a horizontal branch star and an ELM white dwarf. The effective temperatures, radii, luminosities, and masses of the two ELMs are (10250, 11500) K (0.42, 0.12) R ⊙, (1.61, 0.23) L ⊙, and (0.186, 0.170) M ⊙, respectively. The star 527 could be a post-mass-transfer system and may have originated through the Case A/B mass-transfer process in a low-density environment. The cooling age of the ELMs is < 1 Myr, indicating that they have only recently formed.
我们利用安装在 AstroSat 上的紫外成像望远镜对疏散星团 NGC 2420 星域中的四颗远紫外（FUV）亮星进行了研究。525、527和560这三颗星是该星团的成员，而646星则是该星团的非成员。为了描述和确定这些恒星的参数，利用紫外、光学和红外数据集分析了多波长光谱能量分布（SED）。对于所有四颗 FUV 明亮恒星，双分量 SED 模型都拟合得很好。我们的研究结果表明，525 和 560 这两颗恒星是双蓝色流浪星（BSS）系统。这些 BSS 系统可能是在一个三级系统中形成的，原因是来自一个演化的外三级伴星的质量转移。527 星是由一颗 BSS 星和一颗极低质量（ELM）白矮星组成的双星系统，而 646 星则是由一颗水平分支星和一颗 ELM 白矮星组成的双星系统。两颗 ELM 的有效温度、半径、光度和质量分别为 (10250, 11500) K (0.42, 0.12) R ⊙, (1.61, 0.23) L ⊙ 和 (0.186, 0.170) M ⊙。527 星可能是一个后质量转移系统，可能是在低密度环境中通过情况 A/B 质量转移过程起源的。ELM的冷却年龄小于1 Myr，表明它们是最近才形成的。
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Pub Date : 2024-01-31DOI: 10.3847/1538-4357/ad0b15
V. Florinski, Juan Alonso Guzman, J. Kleimann, I. Baliukin, Keyvan Ghanbari, D. Turner, B. Zieger, J. Kóta, M. Opher, V. Izmodenov, D. Alexashov, J. Giacalone, J. Richardson
This paper examines the geometry of interstellar magnetic field lines close to the boundary of the heliosphere in the direction of the unperturbed local interstellar magnetic field, where the field lines are spread apart by the heliopause (HP). Such field parting establishes a region of weaker magnetic field of about 300 au in size in the northern hemisphere that acts as a giant magnetic trap affecting the propagation of galactic cosmic rays (GCRs). The choice of an analytic model of the magnetic field in the very local interstellar medium allows us to qualitatively study the resulting magnetic field draping pattern while avoiding unphysical dissipation across the HP-impeding numerical magnetohydrodynamic (MHD) models. We investigate GCR transport in the region exterior to the heliosphere, including the magnetic trap, subject to guiding center drifts, pitch angle scattering, and perpendicular diffusion. The transport coefficients were derived from Voyager 1 observations of magnetic turbulence in the VLISM. Our results predict a ring current of energetic ions drifting around the interior of the magnetic trap. It is also demonstrated that GCRs cross the HP for the first time preferentially through a crescent-shaped region between the magnetic trap and the upwind direction. The paper includes results of MHD modeling of the heliosphere that provide the coordinates of the center of the magnetic trap in ecliptic coordinates. In addition to the heliosphere, we examine several extreme field draping configurations that could describe the astrospheres of other stars.
本文研究了日光层边界附近未受扰动的本地星际磁场方向的星际磁场线的几何形状，在那里，磁场线被日光层（HP）分开。这种磁场分离在北半球形成了一个面积约为 300 au 的较弱磁场区域，它就像一个巨大的磁阱，影响着银河宇宙射线（GCR）的传播。我们选择了一个非常局部的星际介质磁场分析模型，这使我们能够定性地研究由此产生的磁场垂悬模式，同时避免了横跨HP阻碍数值磁流体动力（MHD）模型的非物理耗散。我们研究了日光层外部区域（包括磁阱）的 GCR 传输，受制于制导中心漂移、俯仰角散射和垂直扩散。传输系数来自旅行者 1 号对 VLISM 中磁湍流的观测。我们的结果预测高能离子环流在磁阱内部漂移。研究还证明，GCRs 首次穿过 HP 时，会优先通过磁阱与上风方向之间的新月形区域。论文包括日光层的 MHD 建模结果，该结果提供了磁阱中心在黄道坐标上的坐标。除了日光层之外，我们还研究了可能描述其他恒星天球的几种极端磁场垂悬构型。
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Pub Date : 2024-01-31DOI: 10.3847/1538-4357/ad2458
D. Balser, T. Wenger
H ii region heavy-element abundances throughout the Galactic disk provide important constraints to theories of the formation and evolution of the Milky Way. In LTE, radio recombination line (RRL) emission and free–free continuum emission are accurate extinction-free tracers of the H ii region electron temperature. Since metals act as coolants in H ii regions via the emission of collisionally excited lines, the electron temperature is a proxy for metallicity. Shaver et al. found a linear relationship between metallicity and electron temperature with little scatter. Here we use CLOUDY H ii region simulations to (1) investigate the accuracy of using RRLs to measure the electron temperature and (2) explore the metallicity–electron temperature relationship. We model 135 H ii regions with different ionizing radiation fields, densities, and metallicities. We find that electron temperatures derived under the assumption of LTE are about 20% systematically higher owing to non-LTE effects, but overall LTE is a good assumption for centimeter-wavelength RRLs. Our CLOUDY simulations are consistent with the Shaver et al. metallicity–electron temperature relationship, but there is significant scatter since earlier spectral types or higher electron densities yield higher electron temperatures. Using RRLs to derive electron temperatures assuming LTE yields errors in the predicted metallicity as large as 10%. We derive correction factors for log(O/H) + 12 in each CLOUDY simulation. For lower metallicities the correction factor depends primarily on the spectral type of the ionizing star and ranges from 0.95 to 1.10, whereas for higher metallicities the correction factor depends on the density and is between 0.97 and 1.05.
整个银河系盘的 H ii 区域重元素丰度为银河系的形成和演化理论提供了重要的约束条件。在 LTE 中，射电重组线（RRL）发射和自由连续面发射是 H ii 区域电子温度的精确无消光追踪器。由于金属通过碰撞激发线的发射在 H ii 区域充当冷却剂，因此电子温度可以代表金属度。Shaver 等人发现金属性与电子温度之间呈线性关系，且散射很小。在这里，我们利用 CLOUDY H ii 区域模拟来：（1）研究使用 RRL 测量电子温度的准确性；（2）探索金属性与电子温度之间的关系。我们模拟了 135 个具有不同电离辐射场、密度和金属性的 H ii 区域。我们发现，由于非 LTE 效应，在 LTE 假设下得出的电子温度系统性地高了约 20%，但总体而言，LTE 对于厘米波长的 RRL 是一个很好的假设。我们的 CLOUDY 模拟与 Shaver 等人的金属性-电子温度关系一致，但由于较早的光谱类型或较高的电子密度会产生较高的电子温度，因此存在明显的差异。使用RRL来推导假定LTE的电子温度，会产生高达10%的金属性预测误差。我们在每一次CLOUDY模拟中都得出了log(O/H) + 12的修正系数。对于较低的金属性，校正因子主要取决于电离星的光谱类型，范围在 0.95 到 1.10 之间；而对于较高的金属性，校正因子则取决于密度，范围在 0.97 到 1.05 之间。
{"title":"The Metallicity–Electron Temperature Relationship in H ii Regions","authors":"D. Balser, T. Wenger","doi":"10.3847/1538-4357/ad2458","DOIUrl":"https://doi.org/10.3847/1538-4357/ad2458","url":null,"abstract":"\u0000 H ii region heavy-element abundances throughout the Galactic disk provide important constraints to theories of the formation and evolution of the Milky Way. In LTE, radio recombination line (RRL) emission and free–free continuum emission are accurate extinction-free tracers of the H ii region electron temperature. Since metals act as coolants in H ii regions via the emission of collisionally excited lines, the electron temperature is a proxy for metallicity. Shaver et al. found a linear relationship between metallicity and electron temperature with little scatter. Here we use CLOUDY H ii region simulations to (1) investigate the accuracy of using RRLs to measure the electron temperature and (2) explore the metallicity–electron temperature relationship. We model 135 H ii regions with different ionizing radiation fields, densities, and metallicities. We find that electron temperatures derived under the assumption of LTE are about 20% systematically higher owing to non-LTE effects, but overall LTE is a good assumption for centimeter-wavelength RRLs. Our CLOUDY simulations are consistent with the Shaver et al. metallicity–electron temperature relationship, but there is significant scatter since earlier spectral types or higher electron densities yield higher electron temperatures. Using RRLs to derive electron temperatures assuming LTE yields errors in the predicted metallicity as large as 10%. We derive correction factors for log(O/H) + 12 in each CLOUDY simulation. For lower metallicities the correction factor depends primarily on the spectral type of the ionizing star and ranges from 0.95 to 1.10, whereas for higher metallicities the correction factor depends on the density and is between 0.97 and 1.05.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"400 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140474107","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 : 2024-01-30DOI: 10.3847/1538-4357/ad0cee
Erick Powell, M. Opher, M. Kornbleuth, I. Baliukin, A. Michael, B. Wood, V. Izmodenov, Gábor Tóth, V. Tenishev
Lyα absorption profiles have been used to detect astrospheres and heliospheric absorption from the hydrogen wall and heliotail. Using magnetohydrodynamic models of the heliosphere, we can compare simulated to observed Lyα profiles to probe the neutral hydrogen within and near the heliosphere. There is an ongoing controversy whether the heliosphere has a long “comet-like” tail or a short “croissant-like” tail. Here we present the first Lyα absorption investigation using a croissant-like heliosphere. With identical boundary conditions we compare the BU model, which presents a croissant-like tail, and the Moscow model, which presents a comet-like tail. The BU and Moscow models present nearly identical Lyα profiles toward nose targets (α Cen and 36 Oph). Differences in Lyα profiles are shown toward the tail target (HD 35296). Despite the shortened heliotail of the croissant model, significant downwind heliosheath absorption is seen, just 5% shallower and shifted by 4 km s−1. This implies that an extended tail model is not required to reproduce the heliosheath Lyα absorption observations. Finer observation gratings may be able to resolve this shift. Additionally, when using higher interstellar medium (ISM) neutral and plasma densities and lower magnetic field (∣B LISM∣ = 3.2 μG, α BV ≈ 40°) than in the Moscow model, we find better agreement with observed Lyα profiles. None of the models presented show agreement in all directions simultaneously. Furthermore, we show that for the ISM conditions with the least certainty (n p,LISM, n H,LISM, T LISM, B LISM), B LISM has the most significant effect on the structure of the hydrogen wall and Lyα profiles.
{"title":"Lyα Absorption in a “Croissant-like” Heliosphere","authors":"Erick Powell, M. Opher, M. Kornbleuth, I. Baliukin, A. Michael, B. Wood, V. Izmodenov, Gábor Tóth, V. Tenishev","doi":"10.3847/1538-4357/ad0cee","DOIUrl":"https://doi.org/10.3847/1538-4357/ad0cee","url":null,"abstract":"\u0000 Lyα absorption profiles have been used to detect astrospheres and heliospheric absorption from the hydrogen wall and heliotail. Using magnetohydrodynamic models of the heliosphere, we can compare simulated to observed Lyα profiles to probe the neutral hydrogen within and near the heliosphere. There is an ongoing controversy whether the heliosphere has a long “comet-like” tail or a short “croissant-like” tail. Here we present the first Lyα absorption investigation using a croissant-like heliosphere. With identical boundary conditions we compare the BU model, which presents a croissant-like tail, and the Moscow model, which presents a comet-like tail. The BU and Moscow models present nearly identical Lyα profiles toward nose targets (α Cen and 36 Oph). Differences in Lyα profiles are shown toward the tail target (HD 35296). Despite the shortened heliotail of the croissant model, significant downwind heliosheath absorption is seen, just 5% shallower and shifted by 4 km s−1. This implies that an extended tail model is not required to reproduce the heliosheath Lyα absorption observations. Finer observation gratings may be able to resolve this shift. Additionally, when using higher interstellar medium (ISM) neutral and plasma densities and lower magnetic field (∣B\u0000 LISM∣ = 3.2 μG, α\u0000 BV ≈ 40°) than in the Moscow model, we find better agreement with observed Lyα profiles. None of the models presented show agreement in all directions simultaneously. Furthermore, we show that for the ISM conditions with the least certainty (n\u0000 p,LISM, n\u0000 H,LISM, T\u0000 LISM, B\u0000 LISM), B\u0000 LISM has the most significant effect on the structure of the hydrogen wall and Lyα profiles.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"138 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140485379","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 : 2024-01-30DOI: 10.3847/1538-4357/ad26e8
Pablo Santamarina Guerrero, Yukio Katsukawa, Shin Toriumi, D. O. Su'arez
Understanding the magnetic fields of the Sun is essential for unraveling the underlying mechanisms driving solar activity. Integrating topological data analysis techniques into these investigations can provide valuable insights into the intricate structures of magnetic fields, enhancing our comprehension of solar activity and its implications. In this study, we explore what persistent homology can offer in the analysis of solar magnetograms, with the objective of introducing a novel tool that will serve as the foundation for further studies of magnetic structures at the solar surface. By combining various filtration methods of the persistent homology analysis, we conduct an analysis of solar magnetograms that captures the broad magnetic scene, involving a mixture of positive and negative polarities. This analysis is applied to observations of both quiet-Sun and active regions, taken with the Hinode/Solar Optical Telescope and SDO/Helioseismic and Magnetic Imager, respectively. Our primary focus is on analyzing the properties of the spatial structures and features of the magnetic fields identified through these techniques. The results show that persistent diagrams can encode the spatial structural complexity of the magnetic flux of active regions by identifying the isolated, connected, and interacting features. They facilitate the classification of active regions based on their morphology and the detection and quantification of interacting structures of opposing polarities, such as δ spots. The small-scale events in the quiet Sun, such as magnetic flux cancellation and emergence, are also revealed in persistent diagrams and can be studied by observing the evolution of the plots and tracking the relevant features.
{"title":"Persistent Homology Analysis for Solar Magnetograms","authors":"Pablo Santamarina Guerrero, Yukio Katsukawa, Shin Toriumi, D. O. Su'arez","doi":"10.3847/1538-4357/ad26e8","DOIUrl":"https://doi.org/10.3847/1538-4357/ad26e8","url":null,"abstract":"\u0000 Understanding the magnetic fields of the Sun is essential for unraveling the underlying mechanisms driving solar activity. Integrating topological data analysis techniques into these investigations can provide valuable insights into the intricate structures of magnetic fields, enhancing our comprehension of solar activity and its implications. In this study, we explore what persistent homology can offer in the analysis of solar magnetograms, with the objective of introducing a novel tool that will serve as the foundation for further studies of magnetic structures at the solar surface. By combining various filtration methods of the persistent homology analysis, we conduct an analysis of solar magnetograms that captures the broad magnetic scene, involving a mixture of positive and negative polarities. This analysis is applied to observations of both quiet-Sun and active regions, taken with the Hinode/Solar Optical Telescope and SDO/Helioseismic and Magnetic Imager, respectively. Our primary focus is on analyzing the properties of the spatial structures and features of the magnetic fields identified through these techniques. The results show that persistent diagrams can encode the spatial structural complexity of the magnetic flux of active regions by identifying the isolated, connected, and interacting features. They facilitate the classification of active regions based on their morphology and the detection and quantification of interacting structures of opposing polarities, such as δ spots. The small-scale events in the quiet Sun, such as magnetic flux cancellation and emergence, are also revealed in persistent diagrams and can be studied by observing the evolution of the plots and tracking the relevant features.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"122 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140484424","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 : 2024-01-30DOI: 10.3847/1538-4357/ad0549
A. L. Williams, G. Heald, E. Wilcots, E. Zweibel
We present λ13 cm polarization observations of the nearby spiral galaxy NGC 6946 with the Westerbork Synthesis Radio Telescope (WSRT) to examine the nearside halo magnetic fields. Despite λ13 cm exhibiting similar two-dimensional morphology as observed at longer (λ18–22 cm) or shorter (λ3 and λ6 cm) wavelengths, more complete frequency coverage will be required to explain the gap in polarization in the southwest quadrant of the galaxy. We fit models of the turbulent and coherent line-of-sight magnetic fields to the fractional degree of linearly polarized emission at λ3, λ6, λ13, λ18, and λ22 cm from observations taken with the WSRT, Karl G. Jansky Very Large Array, and Effelsberg telescopes. The results favor a multilayer turbulent magneto-ionized medium consistent with current observations of edge-on galaxies. We constrain the physical properties of the synchrotron-emitting thin and thick disks (scale heights of 300 pc and 1.4 kpc, respectively) along with the thermal thick disk and halo (scale heights of 1 and 5 kpc, respectively). Our preferred model indicates a clumpy and highly turbulent medium within 1 kpc of the midplane, and a diffuse extraplanar layer with a substantially lower degree of Faraday depolarization. In the halo, we estimate a regular magnetic field strength of 0.4–2.2 μG and that turbulence and a total magnetic field strength of ∼6 μG result in a Faraday dispersion of σ RM = 4–48 rad m−2. This work is an example of how the advanced capabilities of modern radio telescopes are opening a new frontier for the study of cosmic magnetism.
我们利用韦斯特伯克合成射电望远镜（Westerbork Synthesis Radio Telescope，WSRT）对附近的螺旋星系NGC 6946进行了λ13厘米偏振观测，以研究近侧光环磁场。尽管λ13 厘米波长的二维形态与在更长（λ18-22 厘米）或更短（λ3 和 λ6 厘米）波长上观测到的二维形态相似，但要解释该星系西南象限的极化差距，还需要更完整的频率覆盖。我们根据WSRT、Karl G. Jansky超大阵列和Effelsberg望远镜的观测结果，将湍流磁场和相干视线磁场模型与λ3、λ6、λ13、λ18和λ22厘米处的线性偏振发射分数度进行了拟合。结果表明这是一种多层湍流磁电离介质，与目前对边缘星系的观测结果一致。我们对同步辐射薄盘和厚盘（尺度高度分别为 300 pc 和 1.4 kpc）以及热厚盘和晕（尺度高度分别为 1 kpc 和 5 kpc）的物理特性进行了约束。我们首选的模型显示，在中面 1 kpc 范围内有一个团块状的高湍流介质，以及一个法拉第去极化程度较低的弥漫平面外层。在光环中，我们估计规则磁场强度为 0.4-2.2 μG，湍流和 ∼6 μG 的总磁场强度导致了 σ RM = 4-48 rad m-2 的法拉第色散。这项工作是现代射电望远镜的先进功能如何为宇宙磁性研究开辟新领域的一个例子。
{"title":"Disentangling Magnetic Fields in NGC 6946 with Wide-band Polarimetry","authors":"A. L. Williams, G. Heald, E. Wilcots, E. Zweibel","doi":"10.3847/1538-4357/ad0549","DOIUrl":"https://doi.org/10.3847/1538-4357/ad0549","url":null,"abstract":"\u0000 We present λ13 cm polarization observations of the nearby spiral galaxy NGC 6946 with the Westerbork Synthesis Radio Telescope (WSRT) to examine the nearside halo magnetic fields. Despite λ13 cm exhibiting similar two-dimensional morphology as observed at longer (λ18–22 cm) or shorter (λ3 and λ6 cm) wavelengths, more complete frequency coverage will be required to explain the gap in polarization in the southwest quadrant of the galaxy. We fit models of the turbulent and coherent line-of-sight magnetic fields to the fractional degree of linearly polarized emission at λ3, λ6, λ13, λ18, and λ22 cm from observations taken with the WSRT, Karl G. Jansky Very Large Array, and Effelsberg telescopes. The results favor a multilayer turbulent magneto-ionized medium consistent with current observations of edge-on galaxies. We constrain the physical properties of the synchrotron-emitting thin and thick disks (scale heights of 300 pc and 1.4 kpc, respectively) along with the thermal thick disk and halo (scale heights of 1 and 5 kpc, respectively). Our preferred model indicates a clumpy and highly turbulent medium within 1 kpc of the midplane, and a diffuse extraplanar layer with a substantially lower degree of Faraday depolarization. In the halo, we estimate a regular magnetic field strength of 0.4–2.2 μG and that turbulence and a total magnetic field strength of ∼6 μG result in a Faraday dispersion of σ\u0000 RM = 4–48 rad m−2. This work is an example of how the advanced capabilities of modern radio telescopes are opening a new frontier for the study of cosmic magnetism.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"319 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140480978","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 : 2024-01-30DOI: 10.3847/1538-4357/ad175f
S. Sahu, B. Medina-Carrillo, D. I. Páez-Sánchez, G. Sánchez-Colón, Subhash Rajpoot
The High Energy Stereoscopic System (H.E.S.S.) started observing the extremely powerful long-duration gamma-ray burst (GRB) GRB 221009A starting 53 hr after the triggering event. The H.E.S.S. collaboration carried out observations on 2022 October 11, 12, and 17 under poor atmospheric conditions, without detecting significant very-high-energy photons from the source and computed the upper limits of the fluxes for the different nights. We study these flux upper limits by using the photohadronic model and show that the interaction of high-energy protons with synchrotron seed photons in the forward-shock region of the GRB jet exhibits behavior compatible with the upper limits computed by the H.E.S.S. collaboration.
{"title":"A Photohadronic Interpretation of H.E.S.S. Afterglow Observations of GRB 221009A","authors":"S. Sahu, B. Medina-Carrillo, D. I. Páez-Sánchez, G. Sánchez-Colón, Subhash Rajpoot","doi":"10.3847/1538-4357/ad175f","DOIUrl":"https://doi.org/10.3847/1538-4357/ad175f","url":null,"abstract":"\u0000 The High Energy Stereoscopic System (H.E.S.S.) started observing the extremely powerful long-duration gamma-ray burst (GRB) GRB 221009A starting 53 hr after the triggering event. The H.E.S.S. collaboration carried out observations on 2022 October 11, 12, and 17 under poor atmospheric conditions, without detecting significant very-high-energy photons from the source and computed the upper limits of the fluxes for the different nights. We study these flux upper limits by using the photohadronic model and show that the interaction of high-energy protons with synchrotron seed photons in the forward-shock region of the GRB jet exhibits behavior compatible with the upper limits computed by the H.E.S.S. collaboration.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"698 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140482870","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 : 2024-01-29DOI: 10.3847/1538-4357/ad1603
Chunming Zhu, C. R. DeVore, J. Dahlin, Jiong Qiu, Maria D. Kazachenko, Vadim M. Uritsky, Jackson S. Vandervelde
Understanding large-scale solar eruptions requires detailed investigation of the entire system’s evolution, including the magnetic environment enveloping the source region and searches for precursor activity prior to event onset. We combine stereoscopic observations from the Solar Dynamics Observatory (SDO) and STEREO-B spacecraft for several hours before a filament ejection, M1.2-class eruptive flare, and coronal mass ejection (CME) originating in NOAA active region (AR) 11305 on 2011 October 1. Two episodes of significant preeruption coronal dimming that occurred well to the southeast of the ejected filament are identified. The CME subsequently took off with a substantial component of velocity toward the dimming, which became very pronounced during eruption. We used SDO/Helioseismic and Magnetic Imager (HMI) data to reconstruct the magnetic environment of the system and found that it contains a null point near the dimming region. AR 11305 had quite complex connections to nearby ARs 11302 and 11306, as well as to other regions of decayed AR flux. The intensifying and spatially expanding precursor dimming was accompanied by southeastward rising motions of loops toward the null point and northeastward and southwestward motions of loops retracting away. These motions and the dimming are consistent with persistent magnetic reconnection occurring at the null point as it moved upward and southeastward, thereby removing a strapping magnetic field high above AR 11305. Eventually, the filament was ejected explosively toward the null point. We conclude that the breakout model for solar eruptions provides a compelling account of this event. Furthermore, we conjecture that preeruption dimmings may be much more frequent than currently recognized.
{"title":"Large-scale Coronal Dimming Foreshadowing a Solar Eruption on 2011 October 1","authors":"Chunming Zhu, C. R. DeVore, J. Dahlin, Jiong Qiu, Maria D. Kazachenko, Vadim M. Uritsky, Jackson S. Vandervelde","doi":"10.3847/1538-4357/ad1603","DOIUrl":"https://doi.org/10.3847/1538-4357/ad1603","url":null,"abstract":"\u0000 Understanding large-scale solar eruptions requires detailed investigation of the entire system’s evolution, including the magnetic environment enveloping the source region and searches for precursor activity prior to event onset. We combine stereoscopic observations from the Solar Dynamics Observatory (SDO) and STEREO-B spacecraft for several hours before a filament ejection, M1.2-class eruptive flare, and coronal mass ejection (CME) originating in NOAA active region (AR) 11305 on 2011 October 1. Two episodes of significant preeruption coronal dimming that occurred well to the southeast of the ejected filament are identified. The CME subsequently took off with a substantial component of velocity toward the dimming, which became very pronounced during eruption. We used SDO/Helioseismic and Magnetic Imager (HMI) data to reconstruct the magnetic environment of the system and found that it contains a null point near the dimming region. AR 11305 had quite complex connections to nearby ARs 11302 and 11306, as well as to other regions of decayed AR flux. The intensifying and spatially expanding precursor dimming was accompanied by southeastward rising motions of loops toward the null point and northeastward and southwestward motions of loops retracting away. These motions and the dimming are consistent with persistent magnetic reconnection occurring at the null point as it moved upward and southeastward, thereby removing a strapping magnetic field high above AR 11305. Eventually, the filament was ejected explosively toward the null point. We conclude that the breakout model for solar eruptions provides a compelling account of this event. Furthermore, we conjecture that preeruption dimmings may be much more frequent than currently recognized.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"50 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140487450","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 : 2024-01-26DOI: 10.3847/1538-4357/ad0ce8
Kate Storey-Fisher, J. Tinker, Zhongxu Zhai, J. DeRose, R. Wechsler, Arka Banerjee
There is untapped cosmological information in galaxy redshift surveys in the nonlinear regime. In this work, we use the Aemulus suite of cosmological N-body simulations to construct Gaussian process emulators of galaxy clustering statistics at small scales (0.1–50 h −1 Mpc) in order to constrain cosmological and galaxy bias parameters. In addition to standard statistics—the projected correlation function w p(r p), the redshift-space monopole of the correlation function ξ 0(s), and the quadrupole ξ 2(s)—we emulate statistics that include information about the local environment, namely the underdensity probability function P U(s) and the density-marked correlation function M(s). This extends the model of Aemulus III for redshift-space distortions by including new statistics sensitive to galaxy assembly bias. In recovery tests, we find that the beyond-standard statistics significantly increase the constraining power on cosmological parameters of interest: including P U(s) and M(s) improves the precision of our constraints on Ωm by 27%, σ 8 by 19%, and the growth of structure parameter, f σ 8, by 12% compared to standard statistics. We additionally find that scales below ∼6 h −1 Mpc contain as much information as larger scales. The density-sensitive statistics also contribute to constraining halo occupation distribution parameters and a flexible environment-dependent assembly bias model, which is important for extracting the small-scale cosmological information as well as understanding the galaxy–halo connection. This analysis demonstrates the potential of emulating beyond-standard clustering statistics at small scales to constrain the growth of structure as a test of cosmic acceleration.
在非线性机制下的星系红移测量中存在着尚未开发的宇宙学信息。在这项工作中，我们利用 Aemulus 宇宙学 N-体模拟套件来构建小尺度（0.1-50 h -1 Mpc）星系聚类统计的高斯过程模拟器，以约束宇宙学和星系偏差参数。除了标准统计量--投影相关函数w p(r p)、相关函数ξ 0(s)的红移空间单极和四极ξ 2(s)之外，我们还模拟了包含局部环境信息的统计量，即欠密度概率函数P U(s)和密度标记相关函数M(s)。这就扩展了 Aemulus III 的红移空间扭曲模型，加入了对星系集合偏差敏感的新统计量。在恢复测试中，我们发现超标准统计量大大提高了对相关宇宙学参数的约束能力：与标准统计量相比，包含 P U(s) 和 M(s) 的统计量使Ωm 的约束精度提高了 27%，σ 8 的约束精度提高了 19%，结构参数 f σ 8 的增长精度提高了 12%。我们还发现，低于 ∼6 h -1 Mpc 的尺度与更大的尺度包含同样多的信息。密度敏感统计也有助于约束光环占据分布参数和一个灵活的环境依赖组装偏差模型，这对于提取小尺度宇宙学信息和理解星系-光环联系非常重要。这项分析展示了在小尺度上模拟超标准聚类统计来约束结构增长的潜力，以此来检验宇宙加速。
{"title":"The Aemulus Project. VI. Emulation of Beyond-standard Galaxy Clustering Statistics to Improve Cosmological Constraints","authors":"Kate Storey-Fisher, J. Tinker, Zhongxu Zhai, J. DeRose, R. Wechsler, Arka Banerjee","doi":"10.3847/1538-4357/ad0ce8","DOIUrl":"https://doi.org/10.3847/1538-4357/ad0ce8","url":null,"abstract":"\u0000 There is untapped cosmological information in galaxy redshift surveys in the nonlinear regime. In this work, we use the Aemulus suite of cosmological N-body simulations to construct Gaussian process emulators of galaxy clustering statistics at small scales (0.1–50 h\u0000 −1 Mpc) in order to constrain cosmological and galaxy bias parameters. In addition to standard statistics—the projected correlation function w\u0000 p(r\u0000 p), the redshift-space monopole of the correlation function ξ\u0000 0(s), and the quadrupole ξ\u0000 2(s)—we emulate statistics that include information about the local environment, namely the underdensity probability function P\u0000 U(s) and the density-marked correlation function M(s). This extends the model of Aemulus III for redshift-space distortions by including new statistics sensitive to galaxy assembly bias. In recovery tests, we find that the beyond-standard statistics significantly increase the constraining power on cosmological parameters of interest: including P\u0000 U(s) and M(s) improves the precision of our constraints on Ωm by 27%, σ\u0000 8 by 19%, and the growth of structure parameter, f\u0000 σ\u0000 8, by 12% compared to standard statistics. We additionally find that scales below ∼6 h\u0000 −1 Mpc contain as much information as larger scales. The density-sensitive statistics also contribute to constraining halo occupation distribution parameters and a flexible environment-dependent assembly bias model, which is important for extracting the small-scale cosmological information as well as understanding the galaxy–halo connection. This analysis demonstrates the potential of emulating beyond-standard clustering statistics at small scales to constrain the growth of structure as a test of cosmic acceleration.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"69 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139593660","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 : 2024-01-26DOI: 10.3847/1538-4357/ad1662
P. Vemareddy
Using multi-instrument and multiwavelength observations, we studied a coronal mass ejection (CME) that led to an intense geomagnetic storm on 2023 April 23. The eruption occurred on April 21 in solar active region (AR) 13283 near the disk center. The AR was in its decay stage, with fragmented polarities and a preexisting long filament channel a few days before the eruption. The study of the magnetic field evolution suggests that the flux rope (filament) was built up by monotonous helicity accumulation over several days, and furthermore, converging and canceling fluxes led to a change in helicity injection, resulting in an unstable nature of the magnetic flux rope (MFR) and its further eruption. Importantly, the CME morphology revealed that the MFR apex underwent a rotation of up to 56° in clockwise direction owing to its positive helicity. The CME decelerates in the field of view (FOV) of the Large Angle Spectrometric Coronagraph and has a plane-of-sky velocity of 1226 km s−1 at 20 R ⊙. In the FOV of the Heliospheric Imager, the lateral expansion of the CME is tracked better than the earthward motion. This implies that the arrival time is difficult to assess. The in situ arrival of the interplanetary CME shock was at 07:30 UT on April 23, and a geomagnetic storm commenced at 08:30 UT. The flux rope fitting to the in situ magnetic field observations reveals that the magnetic cloud flux rope orientation is consistent with its near-Sun orientation, which has a strong negative Bz-component. The analysis of this study indicates that the near-Sun rotation of the filament during its eruption to the CME is the key to the negative Bz-component and consequently the intense geomagnetic storm.
{"title":"Filament Eruption from Active Region 13283 Leading to a Fast Halo-CME and an Intense Geomagnetic Storm on 2023 April 23","authors":"P. Vemareddy","doi":"10.3847/1538-4357/ad1662","DOIUrl":"https://doi.org/10.3847/1538-4357/ad1662","url":null,"abstract":"\u0000 Using multi-instrument and multiwavelength observations, we studied a coronal mass ejection (CME) that led to an intense geomagnetic storm on 2023 April 23. The eruption occurred on April 21 in solar active region (AR) 13283 near the disk center. The AR was in its decay stage, with fragmented polarities and a preexisting long filament channel a few days before the eruption. The study of the magnetic field evolution suggests that the flux rope (filament) was built up by monotonous helicity accumulation over several days, and furthermore, converging and canceling fluxes led to a change in helicity injection, resulting in an unstable nature of the magnetic flux rope (MFR) and its further eruption. Importantly, the CME morphology revealed that the MFR apex underwent a rotation of up to 56° in clockwise direction owing to its positive helicity. The CME decelerates in the field of view (FOV) of the Large Angle Spectrometric Coronagraph and has a plane-of-sky velocity of 1226 km s−1 at 20 R\u0000 ⊙. In the FOV of the Heliospheric Imager, the lateral expansion of the CME is tracked better than the earthward motion. This implies that the arrival time is difficult to assess. The in situ arrival of the interplanetary CME shock was at 07:30 UT on April 23, and a geomagnetic storm commenced at 08:30 UT. The flux rope fitting to the in situ magnetic field observations reveals that the magnetic cloud flux rope orientation is consistent with its near-Sun orientation, which has a strong negative Bz-component. The analysis of this study indicates that the near-Sun rotation of the filament during its eruption to the CME is the key to the negative Bz-component and consequently the intense geomagnetic storm.","PeriodicalId":504209,"journal":{"name":"The Astrophysical Journal","volume":"70 18","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139593647","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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