Pub Date : 2026-02-27DOI: 10.3847/1538-4357/ae355f
Maria D. Kazachenko, Yuhong Fan and Andrey N. Afanasyev
Understanding the three-dimensional evolution of coronal magnetic fields during solar flares remains challenging due to the lack of direct coronal field measurements. Here, we combine data-driven MHD simulations of NOAA AR 11158 with flare-ribbon and coronal-dimming observations to investigate realistic coronal magnetic-field evolution during an X-class flare. We introduce L-maps—maps of natural logarithm of magnetic field-line lengths—as a diagnostic tool to track the dynamics of simulated coronal magnetic structures. Variations in L-maps identify flare ribbons through field-line shortening and coronal dimmings through field-line lengthening. Comparison with Solar Dynamics Observatory/Atmospheric Imaging Assembly observations demonstrates strong morphological and temporal agreement, validating the simulated field evolution. Applying K-means clustering to the L-map temporal profiles, we distinguish three stages of coronal evolution: (1) slow preflare rise phase, (2) flare reconnection accompanied by coronal mass ejection (CME) rise, and (3) post-reconnection CME expansion. We detect a slow preflare rise phase of magnetic field lines routed in ribbon footpoints and identify reconnection dimming—an area of rapid expansion of active-region core magnetic field lines during the flare impulsive phase due to reconnection. Our results show that L-maps provide a powerful and physically intuitive framework for bridging simulations and observations and for tracking the full three-dimensional evolution of coronal magnetic fields during flares.
由于缺乏直接的日冕磁场测量，了解太阳耀斑期间日冕磁场的三维演变仍然具有挑战性。在这里，我们将数据驱动的MHD模拟NOAA AR 11158与耀斑带和日冕变暗观测相结合，研究x级耀斑期间真实的日冕磁场演变。我们引入l -映射-磁场线长度的自然对数映射-作为一种诊断工具来跟踪模拟日冕磁结构的动力学。l图的变化通过场线缩短来识别耀斑带，通过场线延长来识别日冕变暗。与太阳动力学观测站/大气成像组件观测结果的比较显示了强烈的形态和时间一致性，验证了模拟场的演变。通过对L-map时间剖面的K-means聚类分析，我们将日冕演化分为三个阶段：(1)耀斑前缓慢上升阶段，(2)耀斑重连伴随日冕物质抛射（CME）上升阶段，以及(3)重连后日冕物质抛射膨胀阶段。我们检测到磁力线在带状脚点上的缓慢的耀斑前上升阶段，并确定了重连变暗——在耀斑脉冲阶段，由于重连，活跃区磁芯磁力线迅速膨胀的区域。我们的研究结果表明，l -map为连接模拟和观测以及跟踪耀斑期间日冕磁场的全三维演变提供了一个强大而直观的物理框架。
{"title":"When Magnetic Field Lines Stretch, Snap, and Expand: A New Look at Solar Flares with L-maps","authors":"Maria D. Kazachenko, Yuhong Fan and Andrey N. Afanasyev","doi":"10.3847/1538-4357/ae355f","DOIUrl":"https://doi.org/10.3847/1538-4357/ae355f","url":null,"abstract":"Understanding the three-dimensional evolution of coronal magnetic fields during solar flares remains challenging due to the lack of direct coronal field measurements. Here, we combine data-driven MHD simulations of NOAA AR 11158 with flare-ribbon and coronal-dimming observations to investigate realistic coronal magnetic-field evolution during an X-class flare. We introduce L-maps—maps of natural logarithm of magnetic field-line lengths—as a diagnostic tool to track the dynamics of simulated coronal magnetic structures. Variations in L-maps identify flare ribbons through field-line shortening and coronal dimmings through field-line lengthening. Comparison with Solar Dynamics Observatory/Atmospheric Imaging Assembly observations demonstrates strong morphological and temporal agreement, validating the simulated field evolution. Applying K-means clustering to the L-map temporal profiles, we distinguish three stages of coronal evolution: (1) slow preflare rise phase, (2) flare reconnection accompanied by coronal mass ejection (CME) rise, and (3) post-reconnection CME expansion. We detect a slow preflare rise phase of magnetic field lines routed in ribbon footpoints and identify reconnection dimming—an area of rapid expansion of active-region core magnetic field lines during the flare impulsive phase due to reconnection. Our results show that L-maps provide a powerful and physically intuitive framework for bridging simulations and observations and for tracking the full three-dimensional evolution of coronal magnetic fields during flares.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"116 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292500","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 : 2026-02-27DOI: 10.3847/1538-4357/ae3dae
Daniel L. Clarkson and Eduard P. Kontar
Type III solar radio bursts are driven by nonthermal electron beams travelling along heliospheric magnetic fields, with the radio emission frequency drift rate determined by the beam speed and the plasma density profile. Analyzing beam kinematics inferred from the drift rate reveals behavior inconsistent with the emitter moving radially through smooth, monotonically decreasing density. We examine whether these features are driven by disturbances in the guiding magnetic field direction, such as switchbacks, rather than plasma inhomogeneities along the beam path. Using simulations and remote observations of 24 interplanetary type III bursts observed by Parker Solar Probe, we relate measured drift rate variations to local field deflections. In 50% of events, we identify disturbances above a 2σ noise level that can be attributed to perpendicular deflections of the field between (0.7 and 1.7) R⊙, over scales (1.8–6.4) R⊙ at heliocentric distances (9–30) R⊙. The features correspond to either density changes of (10%–30%), or deflections of the field direction by (23°–88°). Further, beam transport simulations show field direction perturbations produce additional observational signatures in type III bursts: delayed emission, intensity breaks, and enhanced emission resembling stria fine structures. In addition, we identified four bursts where the observed variations are more plausibly explained by field deflections, possibly in the form of magnetic switchbacks than by unrealistically large density changes along the field line. The results show that variations in type III burst profiles can arise from magnetic as well as density fluctuations and demonstrate the value of type III bursts as remote probes of inner-heliospheric structure at kilometric wavelengths.
{"title":"Signatures of Large-scale Magnetic Field Disturbances and Switchbacks in Interplanetary Type III Radio Bursts","authors":"Daniel L. Clarkson and Eduard P. Kontar","doi":"10.3847/1538-4357/ae3dae","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3dae","url":null,"abstract":"Type III solar radio bursts are driven by nonthermal electron beams travelling along heliospheric magnetic fields, with the radio emission frequency drift rate determined by the beam speed and the plasma density profile. Analyzing beam kinematics inferred from the drift rate reveals behavior inconsistent with the emitter moving radially through smooth, monotonically decreasing density. We examine whether these features are driven by disturbances in the guiding magnetic field direction, such as switchbacks, rather than plasma inhomogeneities along the beam path. Using simulations and remote observations of 24 interplanetary type III bursts observed by Parker Solar Probe, we relate measured drift rate variations to local field deflections. In 50% of events, we identify disturbances above a 2σ noise level that can be attributed to perpendicular deflections of the field between (0.7 and 1.7) R⊙, over scales (1.8–6.4) R⊙ at heliocentric distances (9–30) R⊙. The features correspond to either density changes of (10%–30%), or deflections of the field direction by (23°–88°). Further, beam transport simulations show field direction perturbations produce additional observational signatures in type III bursts: delayed emission, intensity breaks, and enhanced emission resembling stria fine structures. In addition, we identified four bursts where the observed variations are more plausibly explained by field deflections, possibly in the form of magnetic switchbacks than by unrealistically large density changes along the field line. The results show that variations in type III burst profiles can arise from magnetic as well as density fluctuations and demonstrate the value of type III bursts as remote probes of inner-heliospheric structure at kilometric wavelengths.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"190 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292511","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 : 2026-02-27DOI: 10.3847/1538-4357/ae3f99
Rahul Sharma, Andrea Sanna and Prince Sharma
We report on our investigation of the NuSTAR and AstroSat observations along with simultaneous NICER observations of the accreting millisecond X-ray pulsar SAX J1808.4–3658, obtained during its tenth outburst from 2022. The NuSTAR observation captured the source near the outburst peak, while AstroSat observed it during the decay phase. Coherent pulsations at ∼401 Hz were detected throughout the outburst, with the fundamental amplitude in the 3–30 keV range increasing from ∼4% near the peak to ∼6% during the decay. The pulsations display strong energy dependence and negative time lags of ∼0.2–0.3 ms, with harder photons leading softer ones. The broadband spectra in both epochs are well described by a soft thermal component and Comptonized continuum, together with a prominent relativistic reflection component. As the outburst evolved, the continuum softened (Γ increasing from ∼1.88 to ∼1.99) and the coronal electron temperature decreased (kTe from ∼31 to ∼18 keV), consistent with enhanced Compton cooling at lower accretion rates. The ionization parameter declined ( from ∼3.4 to ∼1.8) while the reflection fraction increased, suggesting a changing accretion geometry with a more compact corona and a larger disk covering fraction during the decay phase. The X-ray luminosity decreased by a factor of ∼3 between the two epochs. Our results suggest the coupled evolution of the corona, disk, and magnetosphere as the mass accretion rate declines.
{"title":"Broadband Timing and Spectral Study of Accreting Millisecond X-Ray Pulsar SAX J1808.4–3658 during Its 2022 Outburst","authors":"Rahul Sharma, Andrea Sanna and Prince Sharma","doi":"10.3847/1538-4357/ae3f99","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3f99","url":null,"abstract":"We report on our investigation of the NuSTAR and AstroSat observations along with simultaneous NICER observations of the accreting millisecond X-ray pulsar SAX J1808.4–3658, obtained during its tenth outburst from 2022. The NuSTAR observation captured the source near the outburst peak, while AstroSat observed it during the decay phase. Coherent pulsations at ∼401 Hz were detected throughout the outburst, with the fundamental amplitude in the 3–30 keV range increasing from ∼4% near the peak to ∼6% during the decay. The pulsations display strong energy dependence and negative time lags of ∼0.2–0.3 ms, with harder photons leading softer ones. The broadband spectra in both epochs are well described by a soft thermal component and Comptonized continuum, together with a prominent relativistic reflection component. As the outburst evolved, the continuum softened (Γ increasing from ∼1.88 to ∼1.99) and the coronal electron temperature decreased (kTe from ∼31 to ∼18 keV), consistent with enhanced Compton cooling at lower accretion rates. The ionization parameter declined ( from ∼3.4 to ∼1.8) while the reflection fraction increased, suggesting a changing accretion geometry with a more compact corona and a larger disk covering fraction during the decay phase. The X-ray luminosity decreased by a factor of ∼3 between the two epochs. Our results suggest the coupled evolution of the corona, disk, and magnetosphere as the mass accretion rate declines.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292552","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 : 2026-02-27DOI: 10.3847/1538-4357/ae2be2
James J. Bock, Asad M. Aboobaker, Joseph Adamo, Rachel Akeson, John M. Alred, Farah Alibay, Matthew L. N. Ashby, Yoonsoo P. Bach, Lindsey E. Bleem, Douglas Bolton, David F. Braun, Sean Bruton, Sean A. Bryan, Tzu-Ching Chang, Shuang-Shuang Chen, Yun-Ting Cheng, James R. Cheshire, Yi-Kuan Chiang, Jean Choppin de Janvry, Samuel Condon, Walter R. Cook, Asantha Cooray, Brendan P. Crill, Ari J. Cukierman, Olivier Doré, C. Darren Dowell, Gregory P. Dubois-Felsmann, Tim Eifler, Spencer Everett, Beth E. Fabinsky, Andreas L. Faisst, James L. Fanson, Allen H. Farrington, Tamim Fatahi, Candice M. Fazar, Richard M. Feder, Eric H. Frater, Henry S. Grasshorn Gebhardt, Utkarsh Giri, Tatiana Goldina, Varoujan Gorjian, Salman Habib, William G. Hart, Chen Heinrich, Joseph L. Hora, Zhaoyu Huai, Howard Hui, Young-Soo Jo, Woong-Seob Jeong, Jae Hwan Kang, Miju Kang, Branislav Kecman, Chul-Hwan Kim, Jaeyeong Kim, Minjin Kim, Young-Jun Kim, Yongjung Kim, J. Davy Kirkpatrick, Yosuke Kobayashi, Phil M...
Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), a NASA Explorer satellite launched on 2025 March 11, is carrying out the first all-sky near-infrared spectral survey. The satellite observes in 102 spectral bands from 0.75 to 5.0 μm with a resolving power ranging from λ/Δλ = 35–130 in 6 2 pixels. The observatory obtains a 5σ depth of 19.5–19.9 AB mag for 0.75 < λ < 3.8 μm with λ/Δλ ∼ 40 and 17.8–18.8 AB mag for 3.8 < λ < 5.0 μm with λ/Δλ ∼ 120 after mapping the full sky four times over two years. Scientifically, SPHEREx will produce a large galaxy redshift survey over the full sky to constrain the amplitude of inflationary non-Gaussianity. The observations will produce two deep spectral maps near the ecliptic poles that use intensity mapping to probe the evolution of galaxies over cosmic history. By mapping the depth of infrared absorption features over the Galactic plane, SPHEREx will comprehensively survey the abundance and composition of water and other biogenic ice species in the interstellar medium. The project will release initial data rapidly in the form of spectral images, and specialized data products over the life of the mission as the surveys proceed. The science team will also produce spectral catalogs of planet-bearing and low-mass stars, solar system objects, and galaxy clusters three years after launch. We describe the design of the instrument and spacecraft, which flow from the core science requirements. Finally, we present an initial evaluation of the satellite’s in-flight performance and key characteristics.
{"title":"The SPHEREx Satellite Mission","authors":"James J. Bock, Asad M. Aboobaker, Joseph Adamo, Rachel Akeson, John M. Alred, Farah Alibay, Matthew L. N. Ashby, Yoonsoo P. Bach, Lindsey E. Bleem, Douglas Bolton, David F. Braun, Sean Bruton, Sean A. Bryan, Tzu-Ching Chang, Shuang-Shuang Chen, Yun-Ting Cheng, James R. Cheshire, Yi-Kuan Chiang, Jean Choppin de Janvry, Samuel Condon, Walter R. Cook, Asantha Cooray, Brendan P. Crill, Ari J. Cukierman, Olivier Doré, C. Darren Dowell, Gregory P. Dubois-Felsmann, Tim Eifler, Spencer Everett, Beth E. Fabinsky, Andreas L. Faisst, James L. Fanson, Allen H. Farrington, Tamim Fatahi, Candice M. Fazar, Richard M. Feder, Eric H. Frater, Henry S. Grasshorn Gebhardt, Utkarsh Giri, Tatiana Goldina, Varoujan Gorjian, Salman Habib, William G. Hart, Chen Heinrich, Joseph L. Hora, Zhaoyu Huai, Howard Hui, Young-Soo Jo, Woong-Seob Jeong, Jae Hwan Kang, Miju Kang, Branislav Kecman, Chul-Hwan Kim, Jaeyeong Kim, Minjin Kim, Young-Jun Kim, Yongjung Kim, J. Davy Kirkpatrick, Yosuke Kobayashi, Phil M...","doi":"10.3847/1538-4357/ae2be2","DOIUrl":"https://doi.org/10.3847/1538-4357/ae2be2","url":null,"abstract":"Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), a NASA Explorer satellite launched on 2025 March 11, is carrying out the first all-sky near-infrared spectral survey. The satellite observes in 102 spectral bands from 0.75 to 5.0 μm with a resolving power ranging from λ/Δλ = 35–130 in 6 2 pixels. The observatory obtains a 5σ depth of 19.5–19.9 AB mag for 0.75 < λ < 3.8 μm with λ/Δλ ∼ 40 and 17.8–18.8 AB mag for 3.8 < λ < 5.0 μm with λ/Δλ ∼ 120 after mapping the full sky four times over two years. Scientifically, SPHEREx will produce a large galaxy redshift survey over the full sky to constrain the amplitude of inflationary non-Gaussianity. The observations will produce two deep spectral maps near the ecliptic poles that use intensity mapping to probe the evolution of galaxies over cosmic history. By mapping the depth of infrared absorption features over the Galactic plane, SPHEREx will comprehensively survey the abundance and composition of water and other biogenic ice species in the interstellar medium. The project will release initial data rapidly in the form of spectral images, and specialized data products over the life of the mission as the surveys proceed. The science team will also produce spectral catalogs of planet-bearing and low-mass stars, solar system objects, and galaxy clusters three years after launch. We describe the design of the instrument and spacecraft, which flow from the core science requirements. Finally, we present an initial evaluation of the satellite’s in-flight performance and key characteristics.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292459","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 : 2026-02-27DOI: 10.3847/1538-4357/ae32eb
Aritra Kundu, Robyn Sanderson, Adam Lidz, Pratik J. Gandhi, Andrew Wetzel, Robert Feldmann, Nondh Panithanpaisal, Jasjeev Singh and Michael Boylan-Kolchin
The “near–far” approach to studying reionization leverages the star formation histories of the Milky Way (MW) or Local Group (LG) galaxies, derived from resolved photometry, to infer the low-mass/faint end of the stellar mass functions (SMFs) or the ultraviolet luminosity functions (UVLFs) of high-redshift galaxies (z ≳ 6), beyond the current James Webb Space Telescope detection limits (MUV ≳ −15). Previous works considered only intact low-mass galaxies in the MW and LG, neglecting disrupted galaxies such as stellar streams and phase-mixed objects. Using the FIRE-2 simulations, we show that these disrupted galaxies contribute up to ∼50% of the total stellar-mass budget of the proto-MW/LG at z = 6−9. Including all the progenitors of these disrupted galaxies improves the normalization of the recovered SMFs/UVLFs by factors of ∼2–3 and reduces the halo-to-halo variation in the slope by ∼20%–40%. This enables robust constraints down to at least the resolution limit of the simulations, near M⋆ ∼ 105M⊙or MUV ∼ −10 at z ≳ 6. We also show that “fossil-record” reconstructions—which assume each present-day system descends from a single reionization-era progenitor—are sensitive to the stellar-mass/UV-magnitude thresholds, which introduces bias in the inferred slopes at the low-mass/faint end. Additionally, we demonstrate that neglecting disrupted systems underestimates the contribution of galaxies with MUV ≲ −15 to the reionization-era UV luminosity density. Finally, we estimate that a significant fraction (∼50%) of streams with M⋆ ≳ 106M⊙ at z = 0 should be detectable from upcoming Rubin Observatory and Roman Space Telescope observations.
{"title":"Rise of the Forsaken Relics: Connecting Present-day Stellar Streams and Phase-mixed Galaxies to the Epoch of Reionization","authors":"Aritra Kundu, Robyn Sanderson, Adam Lidz, Pratik J. Gandhi, Andrew Wetzel, Robert Feldmann, Nondh Panithanpaisal, Jasjeev Singh and Michael Boylan-Kolchin","doi":"10.3847/1538-4357/ae32eb","DOIUrl":"https://doi.org/10.3847/1538-4357/ae32eb","url":null,"abstract":"The “near–far” approach to studying reionization leverages the star formation histories of the Milky Way (MW) or Local Group (LG) galaxies, derived from resolved photometry, to infer the low-mass/faint end of the stellar mass functions (SMFs) or the ultraviolet luminosity functions (UVLFs) of high-redshift galaxies (z ≳ 6), beyond the current James Webb Space Telescope detection limits (MUV ≳ −15). Previous works considered only intact low-mass galaxies in the MW and LG, neglecting disrupted galaxies such as stellar streams and phase-mixed objects. Using the FIRE-2 simulations, we show that these disrupted galaxies contribute up to ∼50% of the total stellar-mass budget of the proto-MW/LG at z = 6−9. Including all the progenitors of these disrupted galaxies improves the normalization of the recovered SMFs/UVLFs by factors of ∼2–3 and reduces the halo-to-halo variation in the slope by ∼20%–40%. This enables robust constraints down to at least the resolution limit of the simulations, near M⋆ ∼ 105M⊙or MUV ∼ −10 at z ≳ 6. We also show that “fossil-record” reconstructions—which assume each present-day system descends from a single reionization-era progenitor—are sensitive to the stellar-mass/UV-magnitude thresholds, which introduces bias in the inferred slopes at the low-mass/faint end. Additionally, we demonstrate that neglecting disrupted systems underestimates the contribution of galaxies with MUV ≲ −15 to the reionization-era UV luminosity density. Finally, we estimate that a significant fraction (∼50%) of streams with M⋆ ≳ 106M⊙ at z = 0 should be detectable from upcoming Rubin Observatory and Roman Space Telescope observations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292499","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 : 2026-02-27DOI: 10.3847/1538-4357/ae3a9e
Andrew G. Sullivan, Jack T. Dinsmore and Roger W. Romani
The intrabinary shocks (IBSs) in spider pulsars emit nonthermal synchrotron X-rays from accelerated electrons and positrons in the shocked pulsar wind, likely energized by magnetic reconnection. The double-peaked X-ray light curves from these shocks have been well characterized in several spider systems. In this paper, we analyze Imaging X-ray Polarimetry Explorer observations of the redback pulsar J1723−2837 to examine the expected synchrotron polarization. Using advanced extraction methods that include spatial, temporal, and particle background weights, we constrain the polarization of the IBS. We compare different models for the magnetic field in the radiation zone and find that the best fit prefers a striped pulsar wind model over other polarized models, with maximum polarization degree of the IBS emission component , in addition to an unpolarized non-IBS component. Since this is only 2.4σ, we cannot claim strong preference over an unpolarized model; we report a 99% confidence level upper limit on the total polarization of both IBS and non-IBS components Π99 < 36%, which is improved over the 50% limit obtained in previous work. The best-fit polarization of the IBS component is consistent with numerical simulations. Detailed tests of such models are accessible to future measurements.
{"title":"X-Ray Polarization of the Intrabinary Shock in Redback Pulsar J1723−2837","authors":"Andrew G. Sullivan, Jack T. Dinsmore and Roger W. Romani","doi":"10.3847/1538-4357/ae3a9e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3a9e","url":null,"abstract":"The intrabinary shocks (IBSs) in spider pulsars emit nonthermal synchrotron X-rays from accelerated electrons and positrons in the shocked pulsar wind, likely energized by magnetic reconnection. The double-peaked X-ray light curves from these shocks have been well characterized in several spider systems. In this paper, we analyze Imaging X-ray Polarimetry Explorer observations of the redback pulsar J1723−2837 to examine the expected synchrotron polarization. Using advanced extraction methods that include spatial, temporal, and particle background weights, we constrain the polarization of the IBS. We compare different models for the magnetic field in the radiation zone and find that the best fit prefers a striped pulsar wind model over other polarized models, with maximum polarization degree of the IBS emission component , in addition to an unpolarized non-IBS component. Since this is only 2.4σ, we cannot claim strong preference over an unpolarized model; we report a 99% confidence level upper limit on the total polarization of both IBS and non-IBS components Π99 < 36%, which is improved over the 50% limit obtained in previous work. The best-fit polarization of the IBS component is consistent with numerical simulations. Detailed tests of such models are accessible to future measurements.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292501","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 : 2026-02-27DOI: 10.3847/1538-4357/ae3bd4
Shaunak Modak, Eve C. Ostriker, Chris Hamilton and Scott Tremaine
Substructure in the interstellar medium (ISM) is crucial for establishing the correlation between star formation and feedback and has the capacity to significantly perturb stellar orbits, thus playing a central role in galaxy dynamics and evolution. Contemporary surveys of gas and dust emission in nearby galaxies resolve structure down to ∼10 pc scales, demanding theoretical models of ISM substructure with matching fidelity. In this work, we address this need by quantitatively characterizing the gas density in state-of-the-art magnetohydrodynamic simulations of disk galaxies that resolve parsec to kiloparsec scales. The TIGRESS-NCR framework we employ includes sheared galactic rotation, self-consistent star formation and feedback, and nonequilibrium chemistry and cooling. We fit simple analytic models to the one-point spatial, two-point spatial, and two-point spatiotemporal statistics of the surface density fluctuation field. We find that for both solar neighborhood and inner-galaxy conditions, (i) the surface density fluctuations follow a log-normal distribution, (ii) the linear and logarithmic fluctuation power spectra are well approximated as power laws with indices of ≈−2.2 and ≈−2.8, respectively, and (iii) lifetimes of structures at different scales are set by a combination of feedback and effective pressure terms. Additionally, we find that the vertical structure of the gas is well modeled by a mixture of exponential and profiles, allowing us to link the surface density statistics to those of the volume density and gravitational potential. We provide convenient parameterizations for incorporating realistic ISM effects into stellar-dynamical studies and for comparison with multiwavelength observations.
{"title":"Characterizing Density and Gravitational Potential Fluctuations of the Interstellar Medium","authors":"Shaunak Modak, Eve C. Ostriker, Chris Hamilton and Scott Tremaine","doi":"10.3847/1538-4357/ae3bd4","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3bd4","url":null,"abstract":"Substructure in the interstellar medium (ISM) is crucial for establishing the correlation between star formation and feedback and has the capacity to significantly perturb stellar orbits, thus playing a central role in galaxy dynamics and evolution. Contemporary surveys of gas and dust emission in nearby galaxies resolve structure down to ∼10 pc scales, demanding theoretical models of ISM substructure with matching fidelity. In this work, we address this need by quantitatively characterizing the gas density in state-of-the-art magnetohydrodynamic simulations of disk galaxies that resolve parsec to kiloparsec scales. The TIGRESS-NCR framework we employ includes sheared galactic rotation, self-consistent star formation and feedback, and nonequilibrium chemistry and cooling. We fit simple analytic models to the one-point spatial, two-point spatial, and two-point spatiotemporal statistics of the surface density fluctuation field. We find that for both solar neighborhood and inner-galaxy conditions, (i) the surface density fluctuations follow a log-normal distribution, (ii) the linear and logarithmic fluctuation power spectra are well approximated as power laws with indices of ≈−2.2 and ≈−2.8, respectively, and (iii) lifetimes of structures at different scales are set by a combination of feedback and effective pressure terms. Additionally, we find that the vertical structure of the gas is well modeled by a mixture of exponential and profiles, allowing us to link the surface density statistics to those of the volume density and gravitational potential. We provide convenient parameterizations for incorporating realistic ISM effects into stellar-dynamical studies and for comparison with multiwavelength observations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292502","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 : 2026-02-27DOI: 10.3847/1538-4357/ae4336
André-Nicolas Chené
Wolf–Rayet (WR) winds exhibit variability driven by small-scale clumping and large-scale corotating interaction regions (CIRs), but their interplay remains uncertain. Archival high-resolution ESPaDOnS spectra of WR 6 were analyzed using wavelet decomposition to isolate variability on different scales. Time variance spectrum diagnostics confirm that clumping contributes 1% variability relative to line intensity, consistent with empirical trends for WR stars. Correlation analysis reveals strong coherence among He ii lines, while the N vλ4945 and He iλ5876 lines display weaker or shifted correlations, reflecting differences in their line-formation regions relative to He ii. Models in which CIRs locally suppress clumping demonstrate that if such interactions occur, spectroscopic diagnostics remain inconclusive. These results provide direct evidence that CIRs and clumping can coexist in WR winds.
{"title":"Disentangling the Spectroscopic Signatures of Clumping and Corotating Interaction Regions in the Wolf–Rayet Star WR 6","authors":"André-Nicolas Chené","doi":"10.3847/1538-4357/ae4336","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4336","url":null,"abstract":"Wolf–Rayet (WR) winds exhibit variability driven by small-scale clumping and large-scale corotating interaction regions (CIRs), but their interplay remains uncertain. Archival high-resolution ESPaDOnS spectra of WR 6 were analyzed using wavelet decomposition to isolate variability on different scales. Time variance spectrum diagnostics confirm that clumping contributes 1% variability relative to line intensity, consistent with empirical trends for WR stars. Correlation analysis reveals strong coherence among He ii lines, while the N vλ4945 and He iλ5876 lines display weaker or shifted correlations, reflecting differences in their line-formation regions relative to He ii. Models in which CIRs locally suppress clumping demonstrate that if such interactions occur, spectroscopic diagnostics remain inconclusive. These results provide direct evidence that CIRs and clumping can coexist in WR winds.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292565","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 : 2026-02-27DOI: 10.3847/1538-4357/ae3d9c
Zhigang Wen, Jianling Chen, Jianping Yuan, Na Wang, Wenming Yan, Wei Han, Zhen Wang, Xuefeng Duan, Liang Jing, Pengcheng He, Abdujappar Rusul, Hui Wang and Chengbing Lyu
In this study, we report on a detailed polarimetric single-pulse analysis of the radio emission from the pulsar B0823+26 (J0825+2637) during its quiescent state. Using the unprecedentedly high-sensitive observations carried out with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at 1250 MHz, potentially interesting emission features are revealed, distinct from bright-state characteristics. The interpulse emission is completely absent, with only the main pulse and postcursor components detected. Notably, no bridging emission is observed between these two distinct emission components. Both the main pulse and postcursor exhibit continuous emission without any pulse nulling phenomenon throughout the observation period. During the nearly 3 hr continuous observation period, a total of 571 bright pulses with relative pulse energy larger than 10 are detected within the main pulse window. Their energy distribution follows a power-law distribution with an index of −2.39 ± 0.03. The interburst time distribution is consistent with a stationary Poisson process, yielding a burst rate of 158 ± 8 events per hour. Furthermore, the fluctuation spectral analysis of single pulse behavior reveals the existence of a periodic amplitude modulation of longitude-stationary subpulses with a periodicity of 20 ± 7 rotational periods across the main pulse window. Possible emission mechanisms are discussed.
{"title":"Unveiling the Hidden Radiation: The Persistent Emission of PSR B0823+26 in Its Quiescent State","authors":"Zhigang Wen, Jianling Chen, Jianping Yuan, Na Wang, Wenming Yan, Wei Han, Zhen Wang, Xuefeng Duan, Liang Jing, Pengcheng He, Abdujappar Rusul, Hui Wang and Chengbing Lyu","doi":"10.3847/1538-4357/ae3d9c","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3d9c","url":null,"abstract":"In this study, we report on a detailed polarimetric single-pulse analysis of the radio emission from the pulsar B0823+26 (J0825+2637) during its quiescent state. Using the unprecedentedly high-sensitive observations carried out with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at 1250 MHz, potentially interesting emission features are revealed, distinct from bright-state characteristics. The interpulse emission is completely absent, with only the main pulse and postcursor components detected. Notably, no bridging emission is observed between these two distinct emission components. Both the main pulse and postcursor exhibit continuous emission without any pulse nulling phenomenon throughout the observation period. During the nearly 3 hr continuous observation period, a total of 571 bright pulses with relative pulse energy larger than 10 are detected within the main pulse window. Their energy distribution follows a power-law distribution with an index of −2.39 ± 0.03. The interburst time distribution is consistent with a stationary Poisson process, yielding a burst rate of 158 ± 8 events per hour. Furthermore, the fluctuation spectral analysis of single pulse behavior reveals the existence of a periodic amplitude modulation of longitude-stationary subpulses with a periodicity of 20 ± 7 rotational periods across the main pulse window. Possible emission mechanisms are discussed.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292504","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 : 2026-02-27DOI: 10.3847/1538-4357/ae40c1
Bhawna Mukhija and Amit Kashi
Evolved massive stars are known to undergo outflow with high-mass ejections, resulting in the loss of a substantial portion of their envelopes. One proposed mechanism driving these events is the release or deposition of energy within the stellar envelope. We use a one-dimensional hydrodynamical code to investigate the resulting outflow and stellar response to energy deposition at specific regions inside a 70 M⊙ star. We compare hydrostatic and hydrodynamic models and test for different energies and widths of the depositing region. We find that due to the deposited energy, the envelope expands significantly, and under certain conditions, such as assuming a uniform electron scattering opacity, this energy input becomes sufficient to unbind material from the outer envelope. This, in turn, leads to the formation of an outflow. We find that higher deposited energy triggers a strong outflow and results in a somewhat hotter and less expanded envelope due to the rapid loss of energy through expelled material. This driving mechanism leads to sudden envelope expansion and the formation of strong outflows in our models, highlighting the generic hydrodynamic response of massive star envelopes to impulsive energy input.
{"title":"Envelope Inflation and Outflow Driven by Energy Deposition in Massive Stars","authors":"Bhawna Mukhija and Amit Kashi","doi":"10.3847/1538-4357/ae40c1","DOIUrl":"https://doi.org/10.3847/1538-4357/ae40c1","url":null,"abstract":"Evolved massive stars are known to undergo outflow with high-mass ejections, resulting in the loss of a substantial portion of their envelopes. One proposed mechanism driving these events is the release or deposition of energy within the stellar envelope. We use a one-dimensional hydrodynamical code to investigate the resulting outflow and stellar response to energy deposition at specific regions inside a 70 M⊙ star. We compare hydrostatic and hydrodynamic models and test for different energies and widths of the depositing region. We find that due to the deposited energy, the envelope expands significantly, and under certain conditions, such as assuming a uniform electron scattering opacity, this energy input becomes sufficient to unbind material from the outer envelope. This, in turn, leads to the formation of an outflow. We find that higher deposited energy triggers a strong outflow and results in a somewhat hotter and less expanded envelope due to the rapid loss of energy through expelled material. This driving mechanism leads to sudden envelope expansion and the formation of strong outflows in our models, highlighting the generic hydrodynamic response of massive star envelopes to impulsive energy input.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"190 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147292556","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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