Pub Date : 2026-03-23DOI: 10.3847/1538-4357/ae4de6
Li Tang and Liang Liu
Fast radio bursts (FRBs) are millisecond-duration radio transients whose physical origin and population structure remain unresolved. A commonly invoked observational distinction—whether a source repeats—has been used to constrain progenitor models, yet this classification is inherently incomplete because the absence of detected repetition does not imply a truly nonrepeating source. Here we cast FRB classification as a positive-unlabeled learning problem and apply a semisupervised machine learning framework to the CHIME/FRB catalog, without presuming that unlabeled sources are genuine nonrepeaters. The resulting classifier successfully recovers most confirmed repeaters and identifies a substantial subset of apparently nonrepeating sources with properties consistent with repetition. Feature-based analyses further reveal that the spectral quality factor and the rest-frame temporal width dominate the population separation. These findings demonstrate that explicitly accounting for label uncertainty is crucial for robust FRB population studies and provides a physically interpretable route toward constraining FRB emission mechanisms.
{"title":"Classification of the CHIME Fast Radio Bursts with Semisupervised Method","authors":"Li Tang and Liang Liu","doi":"10.3847/1538-4357/ae4de6","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4de6","url":null,"abstract":"Fast radio bursts (FRBs) are millisecond-duration radio transients whose physical origin and population structure remain unresolved. A commonly invoked observational distinction—whether a source repeats—has been used to constrain progenitor models, yet this classification is inherently incomplete because the absence of detected repetition does not imply a truly nonrepeating source. Here we cast FRB classification as a positive-unlabeled learning problem and apply a semisupervised machine learning framework to the CHIME/FRB catalog, without presuming that unlabeled sources are genuine nonrepeaters. The resulting classifier successfully recovers most confirmed repeaters and identifies a substantial subset of apparently nonrepeating sources with properties consistent with repetition. Feature-based analyses further reveal that the spectral quality factor and the rest-frame temporal width dominate the population separation. These findings demonstrate that explicitly accounting for label uncertainty is crucial for robust FRB population studies and provides a physically interpretable route toward constraining FRB emission mechanisms.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495331","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 : 2026-03-23DOI: 10.3847/1538-4357/ae48e8
Michael Messere, Kirill Tchernyshyov, Mary E. Putman, Greg L. Bryan, Jessica K. Werk, Yong Zheng and David Schiminovich
This paper explores the extent to which the circumgalactic medium (CGM) of Milky Way (MW)-like galaxies is located in an extended, ionized, disklike structure. To test this hypothesis, we analyze the spatial and kinematic distributions of different ion species within a sample of MW-like systems in IllustrisTNG. We model commonly observed ions (H I, Mg II, Si IV, C IV, and O VI) and calculate (1) their angular momentum misalignment from the star-forming disk (θ) and (2) the fraction of absorption consistent with galaxy rotation (fEWcorot). We find that 63% of Mg ii, 45% of Si iv, 38% of C iv, and 35% of O vi mass along the major axis have kinematics aligned with the galaxy angular momentum axis. We extend this to a mock absorption line survey and quantify fEWcorot. We find that fEWcorot(Mg ii) ∼ 80% and fEWcorot(O vi) ∼ 60% at ∼0.5R200c, in agreement with recent observational work. We find that in the typical MW analog, there is evidence of cool–warm material in an extended, corotating structure, regardless of whether the angular momentum or observational definition is used. Hence, we expect that the typical MW CGM, especially in the low ions, should be mainly on the plane.
本文探讨了银河系（MW）类星系的环星系介质（CGM）位于扩展的、电离的、盘状结构中的程度。为了验证这一假设，我们在IllustrisTNG中分析了mw类系统样本中不同离子种类的空间和运动学分布。我们模拟了常见的离子（H I, Mg II, Si IV， C IV和O VI），并计算了(1)它们与恒星形成盘的角动量偏差（θ）和(2)与星系旋转一致的吸收分数（fEWcorot）。我们发现63%的Mg ii、45%的Si iv、38%的C iv和35%的O vi质量沿长轴的运动学与星系角动量轴对齐。我们将其扩展到模拟吸收线调查并量化fEWcorot。我们发现fEWcorot(Mg ii) ~ 80%和fEWcorot(O vi) ~ 60%在~ 0.5R200c，与最近的观测工作一致。我们发现，在典型的微波模拟中，无论是否使用角动量或观测定义，都有证据表明，在扩展的、旋转的结构中存在冷-热物质。因此，我们预计典型的毫瓦CGM，特别是在低离子下，应该主要在平面上。
{"title":"Mainly on the Plane: Observing the Extended, Ionized Disks of Milky Way Analogs in IllustrisTNG","authors":"Michael Messere, Kirill Tchernyshyov, Mary E. Putman, Greg L. Bryan, Jessica K. Werk, Yong Zheng and David Schiminovich","doi":"10.3847/1538-4357/ae48e8","DOIUrl":"https://doi.org/10.3847/1538-4357/ae48e8","url":null,"abstract":"This paper explores the extent to which the circumgalactic medium (CGM) of Milky Way (MW)-like galaxies is located in an extended, ionized, disklike structure. To test this hypothesis, we analyze the spatial and kinematic distributions of different ion species within a sample of MW-like systems in IllustrisTNG. We model commonly observed ions (H I, Mg II, Si IV, C IV, and O VI) and calculate (1) their angular momentum misalignment from the star-forming disk (θ) and (2) the fraction of absorption consistent with galaxy rotation (fEWcorot). We find that 63% of Mg ii, 45% of Si iv, 38% of C iv, and 35% of O vi mass along the major axis have kinematics aligned with the galaxy angular momentum axis. We extend this to a mock absorption line survey and quantify fEWcorot. We find that fEWcorot(Mg ii) ∼ 80% and fEWcorot(O vi) ∼ 60% at ∼0.5R200c, in agreement with recent observational work. We find that in the typical MW analog, there is evidence of cool–warm material in an extended, corotating structure, regardless of whether the angular momentum or observational definition is used. Hence, we expect that the typical MW CGM, especially in the low ions, should be mainly on the plane.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495323","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}
The origin of the jets in young stellar objects (YSOs) remains a subject of active investigation. We present a 3D MHD simulation of the jet launching in YSOs, focusing on the interaction between the stellar magnetosphere and the accretion disk. In our model, a fast low-density bipolar jet is powered by disk–magnetosphere interaction and launched through the polar cavity that is mass-loaded from the disk rather than the star. Specifically, outflows are driven by toroidal magnetic pressure generated along “two-legged” field lines, anchored at a magnetically dominated stellar footpoint and a mass-dominated point on the (magnetically elevated) disk surface via a cyclic “load–fire–reload” process: in the “load” stage, the differential rotation between the stellar and disk footpoints generates toroidal magnetic pressure; in the “fire” stage, vertical gradients in the toroidal field accelerate plasma and transport the Poynting flux into the polar cavity; and in the “reload” stage, magnetic reconnection allows the cycle to repeat, reforming “two-legged” field lines. These field lines are not required to be fully reset to a dipolar loop configuration; it is only required that the disk end be shallowly embedded in the (elevated) disk surface. This rapid asynchronous process produces a continuous large-scale outflow. The resulting magnetically dominated (Poynting) jet, accelerated by magnetic pressure within the low-density polar cavity, is distinct from the denser, slower disk wind launched through the classic magnetic tower mechanism. Comparison with a disk-only model shows that the rotating stellar magnetosphere promotes bipolar jet launching by shaping a magnetic geometry favorable to symmetric outflows.
{"title":"Modeling YSO Jets in 3D. II. Accretion-fed, Star-anchored Poynting Jets in the Low-density Polar Cavity Powered by Disk–Magnetosphere Interaction","authors":"Yisheng Tu, 以晟 涂, Zhi-Yun Li, Zhaohuan Zhu, 照寰 朱, Xiao Hu, 晓 胡, Chun-Yen Hsu and 峻彥 徐","doi":"10.3847/1538-4357/ae4598","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4598","url":null,"abstract":"The origin of the jets in young stellar objects (YSOs) remains a subject of active investigation. We present a 3D MHD simulation of the jet launching in YSOs, focusing on the interaction between the stellar magnetosphere and the accretion disk. In our model, a fast low-density bipolar jet is powered by disk–magnetosphere interaction and launched through the polar cavity that is mass-loaded from the disk rather than the star. Specifically, outflows are driven by toroidal magnetic pressure generated along “two-legged” field lines, anchored at a magnetically dominated stellar footpoint and a mass-dominated point on the (magnetically elevated) disk surface via a cyclic “load–fire–reload” process: in the “load” stage, the differential rotation between the stellar and disk footpoints generates toroidal magnetic pressure; in the “fire” stage, vertical gradients in the toroidal field accelerate plasma and transport the Poynting flux into the polar cavity; and in the “reload” stage, magnetic reconnection allows the cycle to repeat, reforming “two-legged” field lines. These field lines are not required to be fully reset to a dipolar loop configuration; it is only required that the disk end be shallowly embedded in the (elevated) disk surface. This rapid asynchronous process produces a continuous large-scale outflow. The resulting magnetically dominated (Poynting) jet, accelerated by magnetic pressure within the low-density polar cavity, is distinct from the denser, slower disk wind launched through the classic magnetic tower mechanism. Comparison with a disk-only model shows that the rotating stellar magnetosphere promotes bipolar jet launching by shaping a magnetic geometry favorable to symmetric outflows.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495322","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 : 2026-03-23DOI: 10.3847/1538-4357/ae48eb
Jack T. Dinsmore and Roger W. Romani
We present X-ray proper motion (PM) measurements of 19 pulsars using new and archival data from the Chandra X-ray Observatory, including pulsar wind trails and X-ray filaments. Precise X-ray PMs are often limited by uncertainties in aligning observations to a common reference frame. Our analysis uses unresolved X-ray flux from stars in the Gaia catalog in addition to X-ray bright point sources for alignment, improving uncertainties. We obtain absolute positions referenced to Gaia with typical astrometric precision ∼30 mas and PM statistical uncertainties down to 1.3 mas yr−1, the most precise X-ray PM achieved to date. With our improved frame alignment, PM accuracies are now limited by the pulsar flux in most cases. These results reveal a new X-ray filament and illuminate the wind nebula structures and origins of several of these pulsars.
我们利用钱德拉x射线天文台的新数据和档案数据，包括脉冲星风迹和x射线细丝，对19颗脉冲星进行了x射线固有运动（PM）测量。精确的x射线pm通常受到将观测结果对准共同参考框架的不确定性的限制。我们的分析使用了盖亚星表中未解析的x射线通量，以及x射线亮点源进行校准，从而改善了不确定性。我们获得了参考盖亚的绝对位置，其典型天文测量精度为30 mas， PM统计不确定性降至1.3 mas yr - 1，这是迄今为止实现的最精确的x射线PM。随着我们改进的框架对准，PM精度现在在大多数情况下受到脉冲星通量的限制。这些结果揭示了一个新的x射线灯丝，并照亮了风星云的结构和一些脉冲星的起源。
{"title":"Chandra Proper Motions and Milliarcsecond Astrometry of 19 Pulsars","authors":"Jack T. Dinsmore and Roger W. Romani","doi":"10.3847/1538-4357/ae48eb","DOIUrl":"https://doi.org/10.3847/1538-4357/ae48eb","url":null,"abstract":"We present X-ray proper motion (PM) measurements of 19 pulsars using new and archival data from the Chandra X-ray Observatory, including pulsar wind trails and X-ray filaments. Precise X-ray PMs are often limited by uncertainties in aligning observations to a common reference frame. Our analysis uses unresolved X-ray flux from stars in the Gaia catalog in addition to X-ray bright point sources for alignment, improving uncertainties. We obtain absolute positions referenced to Gaia with typical astrometric precision ∼30 mas and PM statistical uncertainties down to 1.3 mas yr−1, the most precise X-ray PM achieved to date. With our improved frame alignment, PM accuracies are now limited by the pulsar flux in most cases. These results reveal a new X-ray filament and illuminate the wind nebula structures and origins of several of these pulsars.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495324","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 : 2026-03-23DOI: 10.3847/1538-4357/ae4c56
Melanie Ficarra, Fronefield Crawford and T. Joseph W. Lazio
We have conducted a search for radio pulsars in six Galactic stellar binary systems with unseen primary stars. All six systems have estimated primary masses in the range that could be consistent with neutron stars. We used the Green Bank Telescope at a center frequency of 350 MHz to search for dispersed periodicities and single pulses across a range of possible dispersion measures and binary accelerations. No astrophysical signals were detected in our search. The estimated 400 MHz luminosity upper limits from the search are comparable to or smaller than the lowest values observed for almost all the known Galactic binary pulsars with cataloged 400 MHz radio luminosities. This implies that the systems we observed either do not harbor radio-emitting pulsars, contain pulsars that do not beam in our direction, or contain pulsars with luminosities that are significantly lower than this subset of the known Galactic binary pulsar population.
{"title":"Upper Limits on Pulsed Radio Emission from Unseen Compact Objects in Six Galactic Stellar Binaries","authors":"Melanie Ficarra, Fronefield Crawford and T. Joseph W. Lazio","doi":"10.3847/1538-4357/ae4c56","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c56","url":null,"abstract":"We have conducted a search for radio pulsars in six Galactic stellar binary systems with unseen primary stars. All six systems have estimated primary masses in the range that could be consistent with neutron stars. We used the Green Bank Telescope at a center frequency of 350 MHz to search for dispersed periodicities and single pulses across a range of possible dispersion measures and binary accelerations. No astrophysical signals were detected in our search. The estimated 400 MHz luminosity upper limits from the search are comparable to or smaller than the lowest values observed for almost all the known Galactic binary pulsars with cataloged 400 MHz radio luminosities. This implies that the systems we observed either do not harbor radio-emitting pulsars, contain pulsars that do not beam in our direction, or contain pulsars with luminosities that are significantly lower than this subset of the known Galactic binary pulsar population.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495326","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 : 2026-03-23DOI: 10.3847/1538-4357/ae47fd
Antonio J. Porras-Valverde, Priyamvada Natarajan, Angelo Ricarte, Kung-Yi Su, Hyerin Cho, 혜린 조, Ramesh Narayan and Ben S. Prather
The accretion and feedback processes governing supermassive black hole (SMBH) growth span an enormous range of spatial scales, from the Event Horizon to the circumgalactic medium. Recent general relativistic magnetohydrodynamic (GRMHD) simulations demonstrate that strong magnetic fields can substantially suppress gas accretion onto black holes. These simulations show that magnetic fields create magnetically arrested disk states, reducing inflow rates by up to 2 orders of magnitude relative to classical predictions. We incorporate this magnetic suppression prescription from recent GRMHD studies into Dark Sage, a semianalytic model that tracks SMBH and galaxy coevolution over cosmic time. Implementing the suppression across different accretion rate regimes, we explore its impact on the distribution of black hole masses, stellar masses in galaxies, and active galactic nucleus (AGN) luminosities. We find that restricting suppression to sub-Eddington accretors (fEdd < 3 × 10−3) and rescaling AGN feedback efficiencies gives simultaneous agreement with the observed local distributions of both galaxy and black hole masses. At early cosmic times (z > 6), super-Eddington growth episodes dominate in our model, reproducing the high number densities of luminous AGN recently discovered by the James Webb Space Telescope. Our results highlight the critical sensitivity of galaxy assembly to the coupling between small-scale accretion physics and large-scale feedback regulation. Magnetic suppression of hot gas accretion can reconcile low-redshift constraints while preserving the rapid black hole growth required at early cosmic epochs, thereby providing a physically motivated bridge between horizon-scale GRMHD simulations and cosmological galaxy-formation models.
{"title":"Bridging Scales: Modeling Suppressed Bondi Accretion on Black Holes and Its Impact on Galaxy Growth","authors":"Antonio J. Porras-Valverde, Priyamvada Natarajan, Angelo Ricarte, Kung-Yi Su, Hyerin Cho, 혜린 조, Ramesh Narayan and Ben S. Prather","doi":"10.3847/1538-4357/ae47fd","DOIUrl":"https://doi.org/10.3847/1538-4357/ae47fd","url":null,"abstract":"The accretion and feedback processes governing supermassive black hole (SMBH) growth span an enormous range of spatial scales, from the Event Horizon to the circumgalactic medium. Recent general relativistic magnetohydrodynamic (GRMHD) simulations demonstrate that strong magnetic fields can substantially suppress gas accretion onto black holes. These simulations show that magnetic fields create magnetically arrested disk states, reducing inflow rates by up to 2 orders of magnitude relative to classical predictions. We incorporate this magnetic suppression prescription from recent GRMHD studies into Dark Sage, a semianalytic model that tracks SMBH and galaxy coevolution over cosmic time. Implementing the suppression across different accretion rate regimes, we explore its impact on the distribution of black hole masses, stellar masses in galaxies, and active galactic nucleus (AGN) luminosities. We find that restricting suppression to sub-Eddington accretors (fEdd < 3 × 10−3) and rescaling AGN feedback efficiencies gives simultaneous agreement with the observed local distributions of both galaxy and black hole masses. At early cosmic times (z > 6), super-Eddington growth episodes dominate in our model, reproducing the high number densities of luminous AGN recently discovered by the James Webb Space Telescope. Our results highlight the critical sensitivity of galaxy assembly to the coupling between small-scale accretion physics and large-scale feedback regulation. Magnetic suppression of hot gas accretion can reconcile low-redshift constraints while preserving the rapid black hole growth required at early cosmic epochs, thereby providing a physically motivated bridge between horizon-scale GRMHD simulations and cosmological galaxy-formation models.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495329","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}
We used high-resolution observations from the New Vacuum Solar Telescope and the Solar Dynamics Observatory to perform a detailed multiwavelength analysis of the fine structures in the flare ribbon of a C3.9-class flare on 2021 April 22. A segment of the flare ribbon was rooted in a sunspot light bridge and exhibited discrete substructures that we term “burrs,” with equivalent diameters of 233–895 km and intercore separations of 1129–1739 km. These structures are characterized by discrete redshifted cores, accompanied by “tails” (length 700–1370 km and width 310–600 km) exhibiting faint blueshifts. These structures exhibit systematic slipping motions along the ribbon, with apparent velocities decelerating from about 40–21 km s−1, and display a distinct quasiperiodicity of ∼6 minutes in Hα and extreme-ultraviolet passbands. Differential emission measure (DEM) analysis confirms the emitting plasma is multithermal, dominated by temperatures of 1–2 MK. The observed morphology and kinematics are consistent with the scenario of impulsive energy deposition by precipitating plasmoids (oblique flux ropes) originating from tearing-mode fragmentation in the coronal current sheet. The specific spatiotemporal correlation between the tails and blueshifts supports the hypothesis of untwisting magnetic flux ropes. Furthermore, the ∼6 minute periodicity suggests that the reconnection process may be modulated by photospheric p-mode oscillations coupled with the tearing-mode instability. Our findings provide observational evidence that these light-bridge-anchored fine structures constitute elementary units of flare energy release.
利用新真空太阳望远镜和太阳动力学天文台的高分辨率观测数据，对2021年4月22日c3.9级耀斑的耀斑带精细结构进行了详细的多波长分析。耀斑带的一部分根植于太阳黑子光桥，呈现出离散的亚结构，我们称之为“毛刺”，其等效直径为233-895公里，核间间距为1129-1739公里。这些结构的特征是离散的红移核心，伴随着“尾巴”（长度700-1370公里，宽度310-600公里），表现出微弱的蓝移。这些结构呈现出沿带系统的滑动运动，视速度从约40-21 km s−1减速，并在Hα和极紫外波段显示出明显的准周期性~ 6分钟。差分发射测量（DEM）分析证实了发射等离子体是多热的，以1-2 MK的温度为主导。观察到的形态和运动学与由日冕电流片撕裂模式破碎产生的等离子体（斜通量绳）沉淀的脉冲能量沉积的情况一致。尾巴和蓝移之间特定的时空相关性支持了解开磁通绳的假设。此外，约6分钟的周期性表明，重联过程可能被光球p模振荡与撕裂模不稳定性耦合调制。我们的发现提供了观测证据，证明这些光桥锚定的精细结构构成了耀斑能量释放的基本单元。
{"title":"Quasiperiodic Slipping Motion of Flare Ribbon Fine Structures Anchored in a Sunspot Light Bridge","authors":"Tianyuan Chen, Xiaoli Yan, Zhike Xue, Jincheng Wang, Zhe Xu, Liheng Yang, Yadan Duan, Yian Zhou, Zongyin Wu, Qifan Dong, Guotang Wu and Xinsheng Zhang","doi":"10.3847/1538-4357/ae4d10","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d10","url":null,"abstract":"We used high-resolution observations from the New Vacuum Solar Telescope and the Solar Dynamics Observatory to perform a detailed multiwavelength analysis of the fine structures in the flare ribbon of a C3.9-class flare on 2021 April 22. A segment of the flare ribbon was rooted in a sunspot light bridge and exhibited discrete substructures that we term “burrs,” with equivalent diameters of 233–895 km and intercore separations of 1129–1739 km. These structures are characterized by discrete redshifted cores, accompanied by “tails” (length 700–1370 km and width 310–600 km) exhibiting faint blueshifts. These structures exhibit systematic slipping motions along the ribbon, with apparent velocities decelerating from about 40–21 km s−1, and display a distinct quasiperiodicity of ∼6 minutes in Hα and extreme-ultraviolet passbands. Differential emission measure (DEM) analysis confirms the emitting plasma is multithermal, dominated by temperatures of 1–2 MK. The observed morphology and kinematics are consistent with the scenario of impulsive energy deposition by precipitating plasmoids (oblique flux ropes) originating from tearing-mode fragmentation in the coronal current sheet. The specific spatiotemporal correlation between the tails and blueshifts supports the hypothesis of untwisting magnetic flux ropes. Furthermore, the ∼6 minute periodicity suggests that the reconnection process may be modulated by photospheric p-mode oscillations coupled with the tearing-mode instability. Our findings provide observational evidence that these light-bridge-anchored fine structures constitute elementary units of flare energy release.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495334","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 : 2026-03-23DOI: 10.3847/1538-4357/ae4354
Mayank Narang, Himanshu Tyagi, Nagayoshi Ohashi, P. Manoj, S. Thomas Megeath, John J. Tobin, Ewine F. Van Dishoeck, Neal J. Evans, Dan M. Watson, Alessio Caratti o Garatti, Jes K. Jørgensen, Robert Gutermuth, Yusuke Aso, Henrik Beuther, Leslie W. Looney, David A. Neufeld, Guillem Anglada, Mayra Osorio, Adam E. Rubinstein, Samuel Federman, Lee W. Hartmann, Pooneh Nazari, Nicole Karnath, Hendrik Linz, Thomas Stanke, Tyler L. Bourke, Yao-Lun Yang, Rolf Kuiper, Joel Green, Pamela Klaassen, Wafa Zakri, Nolan Habel, Nashanty Brunken, James Muzerolle, Katerina Slavicinska, Amelia M. Stutz, Lukasz Tychoniec, Scott Wolk, Will R. M. Rocha and William J. Fischer
Understanding the earliest stage of star and planet formation requires detailed observations to address the connection and interplay between the accretion, outflow, and disk evolution. We present results from the observations of the low luminosity (Lbol ∼ 0.2 L⊙) and mass (M* ∼ 0.15 M⊙) Class 0 protostar IRAS 16253−2429, conducted as part of the eDisk Atacama Large Millimeter/submillimeter Array (ALMA) large program and the JWST cycle-1 GO Investigating Protostellar Accretion program. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at ≤5 μm), with a brighter, extended northern side. We detect 15 pure rotational H2 transitions (Eup: 1015–21411 K), revealing a wide-angle molecular outflow. The outflow width (as traced in H2 0–0 S(11)) at the protostellar location measures ≤35 au, slightly larger than the dust and Keplerian disk diameters (∼30 au) but wider than the 20–23 au jet width in [Fe II]. The opening angle narrows from 40° to 35° for the low-J H2 lines (up to S(5)) and the cold gas component (ALMA 12CO) to ∼28°–19° for the high-J H2 lines (S(7)–S(11)). Position–velocity diagrams of H2 reveal higher velocities for higher Eup, ranging from 12.5 km s−1 for H2 0–0 S(1) and S(2) to 28.5 km s−1 for H2 0–0 S(5) and S(7) with respect to the mean flow velocity. The nested excitation and velocity structure of the collimated jet and wide-angle wind suggest a magnetohydrodynamic wind as a likely launching mechanism, similar to the findings in other protostars and Class II sources. The lower velocity millimeter CO may be gas from the infalling envelope accelerated outwards by the wide-angle wind along the cavity walls.
{"title":"Investigating the Nested Structure of the Outflow from the Low Luminosity Protostar IRAS 16253-2429 Using JWST and ALMA","authors":"Mayank Narang, Himanshu Tyagi, Nagayoshi Ohashi, P. Manoj, S. Thomas Megeath, John J. Tobin, Ewine F. Van Dishoeck, Neal J. Evans, Dan M. Watson, Alessio Caratti o Garatti, Jes K. Jørgensen, Robert Gutermuth, Yusuke Aso, Henrik Beuther, Leslie W. Looney, David A. Neufeld, Guillem Anglada, Mayra Osorio, Adam E. Rubinstein, Samuel Federman, Lee W. Hartmann, Pooneh Nazari, Nicole Karnath, Hendrik Linz, Thomas Stanke, Tyler L. Bourke, Yao-Lun Yang, Rolf Kuiper, Joel Green, Pamela Klaassen, Wafa Zakri, Nolan Habel, Nashanty Brunken, James Muzerolle, Katerina Slavicinska, Amelia M. Stutz, Lukasz Tychoniec, Scott Wolk, Will R. M. Rocha and William J. Fischer","doi":"10.3847/1538-4357/ae4354","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4354","url":null,"abstract":"Understanding the earliest stage of star and planet formation requires detailed observations to address the connection and interplay between the accretion, outflow, and disk evolution. We present results from the observations of the low luminosity (Lbol ∼ 0.2 L⊙) and mass (M* ∼ 0.15 M⊙) Class 0 protostar IRAS 16253−2429, conducted as part of the eDisk Atacama Large Millimeter/submillimeter Array (ALMA) large program and the JWST cycle-1 GO Investigating Protostellar Accretion program. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at ≤5 μm), with a brighter, extended northern side. We detect 15 pure rotational H2 transitions (Eup: 1015–21411 K), revealing a wide-angle molecular outflow. The outflow width (as traced in H2 0–0 S(11)) at the protostellar location measures ≤35 au, slightly larger than the dust and Keplerian disk diameters (∼30 au) but wider than the 20–23 au jet width in [Fe II]. The opening angle narrows from 40° to 35° for the low-J H2 lines (up to S(5)) and the cold gas component (ALMA 12CO) to ∼28°–19° for the high-J H2 lines (S(7)–S(11)). Position–velocity diagrams of H2 reveal higher velocities for higher Eup, ranging from 12.5 km s−1 for H2 0–0 S(1) and S(2) to 28.5 km s−1 for H2 0–0 S(5) and S(7) with respect to the mean flow velocity. The nested excitation and velocity structure of the collimated jet and wide-angle wind suggest a magnetohydrodynamic wind as a likely launching mechanism, similar to the findings in other protostars and Class II sources. The lower velocity millimeter CO may be gas from the infalling envelope accelerated outwards by the wide-angle wind along the cavity walls.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495364","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 : 2026-03-23DOI: 10.3847/1538-4357/ae3156
Chinmay S. Kulkarni, Thomas Behling, Elisabeth E. Banks, Jason Jones, Tyler Robbins, Nathanael Burns-Watson, S. Thomas Megeath, Robert Gutermuth, Samuel Federman, Savio B. Oliveira, Wafa Zakri, William J. Fischer and Riwaj Pokhrel
Infrared observations can probe photometric variability across the full evolutionary range of young stellar objects (YSOs), from deeply embedded protostars to pre-main-sequence stars with dusty disks. We present 3–8 μm light curves extending 27 yr from 1997 to 2024 obtained with three space-based IR telescopes: Infrared Space Observatory, Spitzer, and Wide-field Infrared Survey Explorer (WISE). Although unevenly sampled with large gaps in coverage, these light curves show variability on timescales ranging from days to decades. We focus on the Spitzer-identified YSOs with disks and envelopes that exhibit variations of a factor of two or more in this wavelength range. We identified seven YSOs where the light curves are dominated by bursts of sustained (>5 yr) high flux, including four that show a steep decay ending the burst and three that are ongoing as of the final observation. We find six YSOs that are undergoing declines, which may be the end of bursts that began before 1997. The most common form of variability, exhibited by 26 YSOs in our sample, show variations over time intervals of years to months but do not exhibit sustained bursts or fades. The Spitzer [3.6] – [4.5] and WISE [3.5] – [4.6] colors either increase or remain constant with increasing brightness, inconsistent with dust extinction as being the primary source of the large-amplitude variability.
{"title":"27 yr of Spaceborne IR Astronomy: An ISO, Spitzer, WISE, and NEOWISE Survey for Large-amplitude Variability in Young Stellar Objects","authors":"Chinmay S. Kulkarni, Thomas Behling, Elisabeth E. Banks, Jason Jones, Tyler Robbins, Nathanael Burns-Watson, S. Thomas Megeath, Robert Gutermuth, Samuel Federman, Savio B. Oliveira, Wafa Zakri, William J. Fischer and Riwaj Pokhrel","doi":"10.3847/1538-4357/ae3156","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3156","url":null,"abstract":"Infrared observations can probe photometric variability across the full evolutionary range of young stellar objects (YSOs), from deeply embedded protostars to pre-main-sequence stars with dusty disks. We present 3–8 μm light curves extending 27 yr from 1997 to 2024 obtained with three space-based IR telescopes: Infrared Space Observatory, Spitzer, and Wide-field Infrared Survey Explorer (WISE). Although unevenly sampled with large gaps in coverage, these light curves show variability on timescales ranging from days to decades. We focus on the Spitzer-identified YSOs with disks and envelopes that exhibit variations of a factor of two or more in this wavelength range. We identified seven YSOs where the light curves are dominated by bursts of sustained (>5 yr) high flux, including four that show a steep decay ending the burst and three that are ongoing as of the final observation. We find six YSOs that are undergoing declines, which may be the end of bursts that began before 1997. The most common form of variability, exhibited by 26 YSOs in our sample, show variations over time intervals of years to months but do not exhibit sustained bursts or fades. The Spitzer [3.6] – [4.5] and WISE [3.5] – [4.6] colors either increase or remain constant with increasing brightness, inconsistent with dust extinction as being the primary source of the large-amplitude variability.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495319","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 : 2026-03-23DOI: 10.3847/1538-4357/ae4d0e
Giuseppe Ficarra, Michele Arcuri, Rita Megale and Sergio Servidio
Observations of supermassive black holes by the Event Horizon Telescope reveal significant inhomogeneities, most likely related to density and magnetic field perturbations. To model these features, we conduct high-resolution 2D general-relativistic magnetohydrodynamic simulations of a Fishbone–Moncrief torus around a Kerr black hole using the black hole accretion code BHAC. We compare unperturbed accretion with a case featuring plasma density bubbles with pressure-balanced magnetic islands of different amplitudes. Power spectrum analysis of accretion time series, performed via the Blackman–Tukey method, shows that the perturbed case exhibits (1) steeper spectral indices compared to the unperturbed case, deviating from the characteristic 1/ω noise spectrum, and (2) increased correlation times, providing evidence for absorption of macrostructures at the event horizon. Spatial autocorrelation analysis of near-horizon turbulence confirms larger energy-containing coherent structures in the perturbed case, altering the accretion rate. These results provide new insights for interpreting observations of supermassive black hole environments, where near-horizon turbulence may play a key role in the accretion process.
{"title":"The Role of Inhomogeneities in the Turbulent Accretion of Black Holes","authors":"Giuseppe Ficarra, Michele Arcuri, Rita Megale and Sergio Servidio","doi":"10.3847/1538-4357/ae4d0e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d0e","url":null,"abstract":"Observations of supermassive black holes by the Event Horizon Telescope reveal significant inhomogeneities, most likely related to density and magnetic field perturbations. To model these features, we conduct high-resolution 2D general-relativistic magnetohydrodynamic simulations of a Fishbone–Moncrief torus around a Kerr black hole using the black hole accretion code BHAC. We compare unperturbed accretion with a case featuring plasma density bubbles with pressure-balanced magnetic islands of different amplitudes. Power spectrum analysis of accretion time series, performed via the Blackman–Tukey method, shows that the perturbed case exhibits (1) steeper spectral indices compared to the unperturbed case, deviating from the characteristic 1/ω noise spectrum, and (2) increased correlation times, providing evidence for absorption of macrostructures at the event horizon. Spatial autocorrelation analysis of near-horizon turbulence confirms larger energy-containing coherent structures in the perturbed case, altering the accretion rate. These results provide new insights for interpreting observations of supermassive black hole environments, where near-horizon turbulence may play a key role in the accretion process.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"271 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147495328","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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