Pub Date : 2026-02-23DOI: 10.3847/2041-8213/ae36aa
Momoko Makita, Tomoharu Oka, Shiho Tsujimoto and Tatsuya Kotani
We report the discovery of multiple compact molecular features exhibiting extremely broad velocity widths toward the W44 molecular cloud. Atacama Large Millimeter/submillimeter Array CO J = 3–2 data reveal eight “Petit-Bullets” surrounding the previously known “Bullet.” Each Petit-Bullet shows a distinct V-shaped structure in position–velocity space, reminiscent of the Y-shaped morphology of the Bullet, suggesting a common origin. These features are interpreted as the result of high-velocity plunges of compact gravitational objects into dense molecular gas. The spatial and kinematic properties of the Petit-Bullets suggest that the plunging material was not a single object but rather a small cluster of compact bodies. A virial mass of 1.0 × 105M⊙ inferred from their velocity dispersion is comparable to that of typical globular clusters. Momentum analysis further implies that the main Bullet likely formed by an isolated black hole. These findings provide new evidence for dynamical interactions between halo clusters and disk molecular gas.
{"title":"Discovery of Multiple Ultra-broad-velocity Molecular Features Associated with the W44 Molecular Cloud","authors":"Momoko Makita, Tomoharu Oka, Shiho Tsujimoto and Tatsuya Kotani","doi":"10.3847/2041-8213/ae36aa","DOIUrl":"https://doi.org/10.3847/2041-8213/ae36aa","url":null,"abstract":"We report the discovery of multiple compact molecular features exhibiting extremely broad velocity widths toward the W44 molecular cloud. Atacama Large Millimeter/submillimeter Array CO J = 3–2 data reveal eight “Petit-Bullets” surrounding the previously known “Bullet.” Each Petit-Bullet shows a distinct V-shaped structure in position–velocity space, reminiscent of the Y-shaped morphology of the Bullet, suggesting a common origin. These features are interpreted as the result of high-velocity plunges of compact gravitational objects into dense molecular gas. The spatial and kinematic properties of the Petit-Bullets suggest that the plunging material was not a single object but rather a small cluster of compact bodies. A virial mass of 1.0 × 105M⊙ inferred from their velocity dispersion is comparable to that of typical globular clusters. Momentum analysis further implies that the main Bullet likely formed by an isolated black hole. These findings provide new evidence for dynamical interactions between halo clusters and disk molecular gas.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"104 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147278406","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 : 2026-02-23DOI: 10.3847/2041-8213/ae4337
Yici Zhong and Elias R. Most
Recent observations of long period radio transients, such as GLEAM-X J0704–37 and ILT J1101+5521, have revealed a previously unrecognized population of Galactic radio transient sources associated with white dwarf (WD)–M dwarf (MD) binaries. It is an open question how to produce coherent radio emission in these systems, though a model driven by binary interaction seems likely given the nature and correlation of the emission with the binaries’ orbital period. Using kinetic plasma simulations, we demonstrate that the relativistic electron cyclotron maser instability (ECMI) is a viable mechanism for generating radio pulses in WD–MD systems, akin to planetary radio emission, such as that from the Jupiter–Io system. We quantify the relativistic ECMI in the nonlinear regime under conditions relevant for WD radio emission for the first time. Our simulations demonstrate that the ECMI can intrinsically produce partially linearly polarized emission relevant to explaining the observed emission spectra of two Galactic sources, though the precise details will depend on the plasma composition. Our work paves the way for a systematic and fully nonlinear computational modeling of radio emission from interacting WD sources.
{"title":"Unraveling the Emission Mechanism Powering Long Period Radio Transients from Interacting White Dwarf Binaries via Kinetic Plasma Simulations","authors":"Yici Zhong and Elias R. Most","doi":"10.3847/2041-8213/ae4337","DOIUrl":"https://doi.org/10.3847/2041-8213/ae4337","url":null,"abstract":"Recent observations of long period radio transients, such as GLEAM-X J0704–37 and ILT J1101+5521, have revealed a previously unrecognized population of Galactic radio transient sources associated with white dwarf (WD)–M dwarf (MD) binaries. It is an open question how to produce coherent radio emission in these systems, though a model driven by binary interaction seems likely given the nature and correlation of the emission with the binaries’ orbital period. Using kinetic plasma simulations, we demonstrate that the relativistic electron cyclotron maser instability (ECMI) is a viable mechanism for generating radio pulses in WD–MD systems, akin to planetary radio emission, such as that from the Jupiter–Io system. We quantify the relativistic ECMI in the nonlinear regime under conditions relevant for WD radio emission for the first time. Our simulations demonstrate that the ECMI can intrinsically produce partially linearly polarized emission relevant to explaining the observed emission spectra of two Galactic sources, though the precise details will depend on the plasma composition. Our work paves the way for a systematic and fully nonlinear computational modeling of radio emission from interacting WD sources.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146778110","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 : 2026-02-23DOI: 10.3847/2041-8213/ae3f2a
Abdujappar Rusul, Z. G. Wen, J. P. Yuan, Ali Esamdin, X. P. Zheng and Michael Kramer
Pulsars are typically characterized by their stable, highly magnetized, and fast-rotating nature, which underpins their persistent radio emissions. However, the discovery of prolonged radio-quiet (“off”) states in intermittent pulsars, such as PSR B1931+24, has been challenging the fundamental theory of pulsar magnetospheric emission. Despite long-term monitoring with several telescopes over 20 yr, the observations of PSR B1931+24 had not detected any significant emission during its “off” states. Recently, sensitive observations via the Five-hundred-meter Aperture Spherical radio Telescope revealed the mysterious weak emissions containing occasional faint bursting pulses during the “off” states of PSR B1931+24, signifying the theory of pulsar magnetospheric emission that the pulsar cannot remain off for long unless it truly dies. Along with a substantial decrease in flux density, a contraction and change in the integrated pulse profile are measured in the “off” state compared to the radio-loud (“on”) state, indicating alterations in the plasma supply and magnetospheric structure. Additionally, previously unobserved asynchronous, nonuniform emission patterns are found in both states, implying a spatially inhomogeneous pair-cascade associated with the coherent radio emission of the pulsar. Furthermore, statistical comparisons between the faint off-state bursts and the on-state emission show that the faint bursts cannot be explained simply as a scaled-down version of the on-state emission. Instead, they constitute a distinct emission mode, plausibly linked to changes in plasma supply and the magnetospheric configuration of PSR B1931+24. These findings greatly advance our understanding of pulsar magnetospheric dynamics and emission mechanisms.
{"title":"Revealing the Unseen: The Discovery of Long-awaited Radiation from the Intermittent Pulsar PSR B1931+24","authors":"Abdujappar Rusul, Z. G. Wen, J. P. Yuan, Ali Esamdin, X. P. Zheng and Michael Kramer","doi":"10.3847/2041-8213/ae3f2a","DOIUrl":"https://doi.org/10.3847/2041-8213/ae3f2a","url":null,"abstract":"Pulsars are typically characterized by their stable, highly magnetized, and fast-rotating nature, which underpins their persistent radio emissions. However, the discovery of prolonged radio-quiet (“off”) states in intermittent pulsars, such as PSR B1931+24, has been challenging the fundamental theory of pulsar magnetospheric emission. Despite long-term monitoring with several telescopes over 20 yr, the observations of PSR B1931+24 had not detected any significant emission during its “off” states. Recently, sensitive observations via the Five-hundred-meter Aperture Spherical radio Telescope revealed the mysterious weak emissions containing occasional faint bursting pulses during the “off” states of PSR B1931+24, signifying the theory of pulsar magnetospheric emission that the pulsar cannot remain off for long unless it truly dies. Along with a substantial decrease in flux density, a contraction and change in the integrated pulse profile are measured in the “off” state compared to the radio-loud (“on”) state, indicating alterations in the plasma supply and magnetospheric structure. Additionally, previously unobserved asynchronous, nonuniform emission patterns are found in both states, implying a spatially inhomogeneous pair-cascade associated with the coherent radio emission of the pulsar. Furthermore, statistical comparisons between the faint off-state bursts and the on-state emission show that the faint bursts cannot be explained simply as a scaled-down version of the on-state emission. Instead, they constitute a distinct emission mode, plausibly linked to changes in plasma supply and the magnetospheric configuration of PSR B1931+24. These findings greatly advance our understanding of pulsar magnetospheric dynamics and emission mechanisms.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146777172","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 : 2026-02-23DOI: 10.3847/2041-8213/ae43ec
Zesen Huang, 泽森 黄, Marco Velli, Olga Panasenco, Richard J. Morton, Chen Shi, 辰 时, Yeimy J. Rivera, Benjamin Chandran, Samuel T. Badman, Yuliang Ding, 宇量 丁, Nour Raouafi, Stuart D. Bale, Michael Stevens, Tamar Ervin, Chuanpeng Hou, Kristopher G. Klein, Orlando Romeo, Jia Huang, 佳 黄, Mingzhe Liu, 明哲 刘, Davin E. Larson, Marc Pulupa, Roberto Livi and Federico Fraschetti
The Sun’s surface vibrates in characteristic 5 minute oscillations, known as p-modes, generated by sound waves trapped within the convection zone. Although these oscillations have long been hypothesized to reach into the solar wind, direct in situ evidence has remained elusive, even during previous close encounters by Parker Solar Probe (PSP). Here, we present strong in situ evidence of 5 minute oscillations in the upper solar corona, based on observations from PSP’s three closest perihelia. In two events at 9.9 solar radii (R⊙), we identify statistically significant (∼6σ) 3.1–3.2 mHz peaks in the magnetic field power spectrum, each appearing as a large-amplitude, spherically polarized Alfvénic wave train lasting approximately 35 minutes. These results demonstrate that global solar oscillations can reach the solar wind.
{"title":"Evidence of 5 minute Oscillations from Parker Solar Probe","authors":"Zesen Huang, 泽森 黄, Marco Velli, Olga Panasenco, Richard J. Morton, Chen Shi, 辰 时, Yeimy J. Rivera, Benjamin Chandran, Samuel T. Badman, Yuliang Ding, 宇量 丁, Nour Raouafi, Stuart D. Bale, Michael Stevens, Tamar Ervin, Chuanpeng Hou, Kristopher G. Klein, Orlando Romeo, Jia Huang, 佳 黄, Mingzhe Liu, 明哲 刘, Davin E. Larson, Marc Pulupa, Roberto Livi and Federico Fraschetti","doi":"10.3847/2041-8213/ae43ec","DOIUrl":"https://doi.org/10.3847/2041-8213/ae43ec","url":null,"abstract":"The Sun’s surface vibrates in characteristic 5 minute oscillations, known as p-modes, generated by sound waves trapped within the convection zone. Although these oscillations have long been hypothesized to reach into the solar wind, direct in situ evidence has remained elusive, even during previous close encounters by Parker Solar Probe (PSP). Here, we present strong in situ evidence of 5 minute oscillations in the upper solar corona, based on observations from PSP’s three closest perihelia. In two events at 9.9 solar radii (R⊙), we identify statistically significant (∼6σ) 3.1–3.2 mHz peaks in the magnetic field power spectrum, each appearing as a large-amplitude, spherically polarized Alfvénic wave train lasting approximately 35 minutes. These results demonstrate that global solar oscillations can reach the solar wind.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146778127","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 : 2026-02-20DOI: 10.3847/2041-8213/ae42c1
Yingjie Luo, 英杰 骆, Eduard P. Kontar, Roelf Du Toit Strauss, Gert J. J. Botha, Tomasz Mrozek, Gelu M. Nita, Sarah Buchner and James O. Chibueze
Radio observations provide powerful diagnostics of energy release, particle acceleration, and transport processes in solar flares. However, despite recent progress in radio interferometric imaging spectroscopy, current instruments still face limitations in image fidelity and resolution, restricting detailed spectroscopic studies of flaring regions. Here we present high-fidelity imaging spectroscopy of an M1.3 GOES class flare with MeerKAT, a precursor to the future-generation array SKA-Mid. Radio emissions at the observed frequencies typically originate in the low corona, offering valuable insights into magnetic reconnection and primary energy-release sites. The obtained images achieve an unprecedented dynamic range exceeding 103, enabling simultaneous analysis of bright coherent bursts and faint incoherent emission from the active region. Multiple spatially distinct coherent sources are identified, implying contributions from different populations of accelerated electrons. The incoherent emission extends beyond Atmospheric Imaging Assembly structures, highlighting MeerKAT’s ability to detect dilute but hot plasma invisible to extreme-ultraviolet instruments. Combined with cotemporal hard X-ray images and magnetic field extrapolations, the radio sources are located within distinct magnetic structures, further revealing their association with different populations of accelerated electrons. These results demonstrate MeerKAT imaging spectroscopy as a powerful diagnostic of solar flares and pave the way for future solar flare studies with SKA-Mid.
{"title":"First Detailed MeerKAT Imaging Spectroscopy of a Solar Flare","authors":"Yingjie Luo, 英杰 骆, Eduard P. Kontar, Roelf Du Toit Strauss, Gert J. J. Botha, Tomasz Mrozek, Gelu M. Nita, Sarah Buchner and James O. Chibueze","doi":"10.3847/2041-8213/ae42c1","DOIUrl":"https://doi.org/10.3847/2041-8213/ae42c1","url":null,"abstract":"Radio observations provide powerful diagnostics of energy release, particle acceleration, and transport processes in solar flares. However, despite recent progress in radio interferometric imaging spectroscopy, current instruments still face limitations in image fidelity and resolution, restricting detailed spectroscopic studies of flaring regions. Here we present high-fidelity imaging spectroscopy of an M1.3 GOES class flare with MeerKAT, a precursor to the future-generation array SKA-Mid. Radio emissions at the observed frequencies typically originate in the low corona, offering valuable insights into magnetic reconnection and primary energy-release sites. The obtained images achieve an unprecedented dynamic range exceeding 103, enabling simultaneous analysis of bright coherent bursts and faint incoherent emission from the active region. Multiple spatially distinct coherent sources are identified, implying contributions from different populations of accelerated electrons. The incoherent emission extends beyond Atmospheric Imaging Assembly structures, highlighting MeerKAT’s ability to detect dilute but hot plasma invisible to extreme-ultraviolet instruments. Combined with cotemporal hard X-ray images and magnetic field extrapolations, the radio sources are located within distinct magnetic structures, further revealing their association with different populations of accelerated electrons. These results demonstrate MeerKAT imaging spectroscopy as a powerful diagnostic of solar flares and pave the way for future solar flare studies with SKA-Mid.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"235 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146222935","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 : 2026-02-20DOI: 10.3847/2041-8213/ae43ed
Macarena G. del Valle-Espinosa, Matilde Mingozzi, Bethan James, Rubén Sánchez-Janssen, Juan Antonio Fernández-Ontiveros, Ryan J. Vaught, Ricardo O. Amorín, Leslie Hunt, Alessandra Aloisi, Karla Z. Arellano-Córdova, Danielle A. Berg, John Chisholm, Matthew Hayes, Svea Hernandez, Alec S. Hirschauer, Logan Jones, Crystal L. Martin, Livia Vallini and Xinfeng Xu
Polycyclic aromatic hydrocarbons (PAHs) are key diagnostics of the physical conditions in the interstellar medium and are widely used to trace star formation in the mid-infrared (mid-IR). The relative strengths of mid-IR PAH features (e.g., 6.2, 7.7, and 11.3 μm) are sensitive to both the size and ionization state of the molecules and can be strongly influenced by the local radiation field. However, at low metallicities (Z < 0.2Z⊙), detecting PAHs remains notoriously difficult, likely reflecting a combination of suppressed formation and enhanced destruction mechanisms. We present new JWST/MIRI Medium Resolution Spectroscopy (MRS) observations of the metal-poor (Z ∼ 0.1Z⊙) dwarf galaxy CGCG 007-025. We confirm the tentative PAH detection previously reported from Spitzer data and, for the first time, identify a compact (∼50 pc) PAH-emitting region nearly cospatial with the newly detected [Ne v] (Ionization potential (I.P.) ∼ 97 eV) emission and the galaxy’s most metal-poor, strongly star-forming region. The PAH11.3μm and PAH 12.7μm features are detected, while no emission is found from other typically brighter features, suggesting a PAH population dominated by large, neutral molecules resilient to hard ionizing fields. When compared with models, mid-IR line ratios involving [Ne iii], [O iv], and [Ne v] can only be reproduced by a combination of star formation and AGN ionization, with the latter contributing 4%–8%. The [O iv] and [Ne v] luminosities exceed what massive stars or shocks can produce, highlighting a puzzling scenario in line with recent JWST observations of similar galaxies. This work provides a crucial reference for studying the physical conditions of the dust and star formation in low-metallicity starburst regions, environments typical of the early Universe.
{"title":"JWST/MIRI-MRS View of the Metal-poor Galaxy CGCG 007-025: The Spatial Location of Polycyclic Aromatic Hydrocarbons and Very Highly Ionized Gas","authors":"Macarena G. del Valle-Espinosa, Matilde Mingozzi, Bethan James, Rubén Sánchez-Janssen, Juan Antonio Fernández-Ontiveros, Ryan J. Vaught, Ricardo O. Amorín, Leslie Hunt, Alessandra Aloisi, Karla Z. Arellano-Córdova, Danielle A. Berg, John Chisholm, Matthew Hayes, Svea Hernandez, Alec S. Hirschauer, Logan Jones, Crystal L. Martin, Livia Vallini and Xinfeng Xu","doi":"10.3847/2041-8213/ae43ed","DOIUrl":"https://doi.org/10.3847/2041-8213/ae43ed","url":null,"abstract":"Polycyclic aromatic hydrocarbons (PAHs) are key diagnostics of the physical conditions in the interstellar medium and are widely used to trace star formation in the mid-infrared (mid-IR). The relative strengths of mid-IR PAH features (e.g., 6.2, 7.7, and 11.3 μm) are sensitive to both the size and ionization state of the molecules and can be strongly influenced by the local radiation field. However, at low metallicities (Z < 0.2Z⊙), detecting PAHs remains notoriously difficult, likely reflecting a combination of suppressed formation and enhanced destruction mechanisms. We present new JWST/MIRI Medium Resolution Spectroscopy (MRS) observations of the metal-poor (Z ∼ 0.1Z⊙) dwarf galaxy CGCG 007-025. We confirm the tentative PAH detection previously reported from Spitzer data and, for the first time, identify a compact (∼50 pc) PAH-emitting region nearly cospatial with the newly detected [Ne v] (Ionization potential (I.P.) ∼ 97 eV) emission and the galaxy’s most metal-poor, strongly star-forming region. The PAH11.3μm and PAH 12.7μm features are detected, while no emission is found from other typically brighter features, suggesting a PAH population dominated by large, neutral molecules resilient to hard ionizing fields. When compared with models, mid-IR line ratios involving [Ne iii], [O iv], and [Ne v] can only be reproduced by a combination of star formation and AGN ionization, with the latter contributing 4%–8%. The [O iv] and [Ne v] luminosities exceed what massive stars or shocks can produce, highlighting a puzzling scenario in line with recent JWST observations of similar galaxies. This work provides a crucial reference for studying the physical conditions of the dust and star formation in low-metallicity starburst regions, environments typical of the early Universe.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146222933","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 : 2026-02-20DOI: 10.3847/2041-8213/ae3d37
Henric Krawczynski
Magnetic reconnection is one of the prime candidate mechanisms that may energize the plasma emitting the strongly polarized X-ray emission from black hole X-ray binaries (BHXRBs) in their hard states. The mechanism requires strong magnetic fields in the upstream plasma entering the reconnection layer, and weaker, but still substantial, magnetic fields in the downstream regions. In this Letter, we estimate the coronal magnetic fields for three different magnetic energy dissipation mechanisms: plasmoid-dominated magnetic reconnection, fast collisionless reconnection, and magnetic field relaxation. We show that the lack of strong Faraday depolarization constrains viable models and can be used to benchmark numerical accretion flow models. We conclude by discussing the difficulties of disentangling the various effects that can depolarize the signals from BHXRBs at low energies. We furthermore emphasize that Faraday rotation is unlikely to play a role in the polarization of the coronal X-ray emission of active galactic nuclei.
{"title":"The Role of Faraday Rotation in the Polarization of the X-Rays from Magnetically Powered Black Hole Coronas","authors":"Henric Krawczynski","doi":"10.3847/2041-8213/ae3d37","DOIUrl":"https://doi.org/10.3847/2041-8213/ae3d37","url":null,"abstract":"Magnetic reconnection is one of the prime candidate mechanisms that may energize the plasma emitting the strongly polarized X-ray emission from black hole X-ray binaries (BHXRBs) in their hard states. The mechanism requires strong magnetic fields in the upstream plasma entering the reconnection layer, and weaker, but still substantial, magnetic fields in the downstream regions. In this Letter, we estimate the coronal magnetic fields for three different magnetic energy dissipation mechanisms: plasmoid-dominated magnetic reconnection, fast collisionless reconnection, and magnetic field relaxation. We show that the lack of strong Faraday depolarization constrains viable models and can be used to benchmark numerical accretion flow models. We conclude by discussing the difficulties of disentangling the various effects that can depolarize the signals from BHXRBs at low energies. We furthermore emphasize that Faraday rotation is unlikely to play a role in the polarization of the coronal X-ray emission of active galactic nuclei.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146222783","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 : 2026-02-19DOI: 10.3847/2041-8213/ae3c98
Jacob Cardinal Tremblay, Boris Goncharov, Rutger van Haasteren, N. D. Ramesh Bhat, Zu-Cheng Chen, Valentina Di Marco, Satoru Iguchi, Agastya Kapur, Wenhua Ling, Rami Mandow, Saurav Mishra, Daniel J. Reardon, Ryan M. Shannon, Hiroshi Sudou, Jingbo Wang, Shi-Yi Zhao, Xing-Jiang Zhu and Andrew Zic
A subparsec supermassive black hole binary (SMBHB) at the center of the galaxy 3C 66B is a promising candidate for continuous gravitational-wave searches with pulsar timing arrays (PTAs). In this work, we search for such a signal in the third data release of the Parkes Pulsar Timing Array. Matching our priors to estimates of binary parameters from electromagnetic (EM) observations, we find a log Bayes factor , highlighting that the source can be neither confirmed nor ruled out. We place upper limits at 95% credibility on the chirp mass , and on the characteristic strain amplitude . This partially rules out the parameter space suggested by EM observations of 3C 66B. We also independently reproduce the calculation of the chirp mass with 3 mm flux monitor data of the unresolved core of 3C 66B. Based on this, we outline a new methodology for constructing a joint likelihood of EM and gravitational-wave data from SMBHBs. Finally, we suggest that targeted searches may allow firmly established SMBHB candidates to be treated as standard sirens, for complementary constraints on the Universe’s expansion rate.
{"title":"A Multimessenger Search for the Supermassive Black Hole Binary in 3C 66B with the Parkes Pulsar Timing Array","authors":"Jacob Cardinal Tremblay, Boris Goncharov, Rutger van Haasteren, N. D. Ramesh Bhat, Zu-Cheng Chen, Valentina Di Marco, Satoru Iguchi, Agastya Kapur, Wenhua Ling, Rami Mandow, Saurav Mishra, Daniel J. Reardon, Ryan M. Shannon, Hiroshi Sudou, Jingbo Wang, Shi-Yi Zhao, Xing-Jiang Zhu and Andrew Zic","doi":"10.3847/2041-8213/ae3c98","DOIUrl":"https://doi.org/10.3847/2041-8213/ae3c98","url":null,"abstract":"A subparsec supermassive black hole binary (SMBHB) at the center of the galaxy 3C 66B is a promising candidate for continuous gravitational-wave searches with pulsar timing arrays (PTAs). In this work, we search for such a signal in the third data release of the Parkes Pulsar Timing Array. Matching our priors to estimates of binary parameters from electromagnetic (EM) observations, we find a log Bayes factor , highlighting that the source can be neither confirmed nor ruled out. We place upper limits at 95% credibility on the chirp mass , and on the characteristic strain amplitude . This partially rules out the parameter space suggested by EM observations of 3C 66B. We also independently reproduce the calculation of the chirp mass with 3 mm flux monitor data of the unresolved core of 3C 66B. Based on this, we outline a new methodology for constructing a joint likelihood of EM and gravitational-wave data from SMBHBs. Finally, we suggest that targeted searches may allow firmly established SMBHB candidates to be treated as standard sirens, for complementary constraints on the Universe’s expansion rate.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146222771","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 : 2026-02-19DOI: 10.3847/2041-8213/ae40ef
Kyu-Hyun Chae
When 3D relative displacement r and velocity v between the pair in a gravitationally bound system are precisely measured, the six measured quantities at one phase can allow elliptical orbit solutions at a given gravitational parameter G. Due to degeneracies between orbital-geometric parameters and G, individual Bayesian inferences and their statistical consolidation are needed to infer G as recently suggested by a Bayesian 3D modeling algorithm. Here, I present a fully general Bayesian algorithm suitable for wide binaries with two (almost) exact sky-projected relative positions (as in the Gaia data release 3) and the other four sufficiently precise quantities. Wide binaries meeting the requirements of the general algorithm to allow for its full potential are rare at present, largely because the measurement uncertainty of the line-of-sight (radial) separation is usually larger than the true separation. As a pilot study, the algorithm is applied to 32 Gaia binaries for which precise HARPS radial velocities are available. The value of (where GN is Newton’s constant) is supporting Newton for a combination of 24 binaries with Newtonian acceleration gN > 10−9m s−2, while it is ( ) for 8 (6) binaries with gN < 10−9 (<10−9.5) m s−2 representing ≳3.5σ discrepancy with Newton. However, one system (stars HD 189739 and HD 189760) dominates the signal. Without it, the tension with Newton is significantly lessened with . Thus, to verify the tentative signal, many such systems need to be discovered, and their kinematic nature such as any possibility of hidden tertiary stars needs to be thoroughly addressed. The pilot study demonstrates the potential of the algorithm in measuring and testing gravity at low acceleration with future samples of wide binaries.
{"title":"Bayesian Inference of Gravity through Realistic 3D Modeling of Wide Binary Orbits: General Algorithm and a Pilot Study with HARPS Radial Velocities","authors":"Kyu-Hyun Chae","doi":"10.3847/2041-8213/ae40ef","DOIUrl":"https://doi.org/10.3847/2041-8213/ae40ef","url":null,"abstract":"When 3D relative displacement r and velocity v between the pair in a gravitationally bound system are precisely measured, the six measured quantities at one phase can allow elliptical orbit solutions at a given gravitational parameter G. Due to degeneracies between orbital-geometric parameters and G, individual Bayesian inferences and their statistical consolidation are needed to infer G as recently suggested by a Bayesian 3D modeling algorithm. Here, I present a fully general Bayesian algorithm suitable for wide binaries with two (almost) exact sky-projected relative positions (as in the Gaia data release 3) and the other four sufficiently precise quantities. Wide binaries meeting the requirements of the general algorithm to allow for its full potential are rare at present, largely because the measurement uncertainty of the line-of-sight (radial) separation is usually larger than the true separation. As a pilot study, the algorithm is applied to 32 Gaia binaries for which precise HARPS radial velocities are available. The value of (where GN is Newton’s constant) is supporting Newton for a combination of 24 binaries with Newtonian acceleration gN > 10−9m s−2, while it is ( ) for 8 (6) binaries with gN < 10−9 (<10−9.5) m s−2 representing ≳3.5σ discrepancy with Newton. However, one system (stars HD 189739 and HD 189760) dominates the signal. Without it, the tension with Newton is significantly lessened with . Thus, to verify the tentative signal, many such systems need to be discovered, and their kinematic nature such as any possibility of hidden tertiary stars needs to be thoroughly addressed. The pilot study demonstrates the potential of the algorithm in measuring and testing gravity at low acceleration with future samples of wide binaries.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"402 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146222772","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}
SGR J1935+2154 is the so-far unique magnetar from which fast radio bursts (FRBs) have been detected. In 2022 October, it resumed its burst activity, and we implemented a dedicated target-of-opportunity observation on it from 2022 October 13 to November 1 (about 940 ks in total) with Insight-HXMT, while the KM40m radio telescope has observed this source for about 1400 hr since October 15. We searched the data of Low Energy (LE), Medium Energy (ME), and High Energy (HE) X-ray telescopes onboard Insight-HXMT in the overlapping observation time windows with the KM40m radio telescope and revealed 60 magnetar X-ray bursts (MXBs), while KM40m only detected 1 radio burst. In particular, we find that there is an X-ray burst on October 21 (denoted as MXB 221021) temporally associated with this radio burst. Interestingly, this association event shows very different morphology from the X-ray and radio association events from this source reported before (e.g., MXB/FRB 200428). Moreover, we systematically analyzed the temporal and spectral properties of the sample of MXBs during this observation and found that the (radio-associated) MXB 221021 shows some different properties from other MXBs without associated radio bursts. These findings shed new light on the physical mechanisms of X-ray bursts and radio burst emission in magnetars.
{"title":"Joint Observation of SGR J1935+2154 with Insight-HXMT and KM40m during the Active Episode of 2022 October","authors":"Wang-Chen Xue, Wen-Jun Tan, Yu-Xiang Huang, Xiao-Bo Li, Long-Fei Hao, Shao-Lin Xiong, Ce Cai, Chen-Wei Wang, Yue Wang, Ke-Jia Lee, Heng Xu, Peng Zhang, Ming-Yu Ge, Hao-Xuan Guo, Yue Huang, Cheng-Kui Li, Jia-Cong Liu, Yang-Zhao Ren, Shuo Xiao, Sheng-Lun Xie, Shu-Xu Yi, Zheng-Hang Yu, Jin-Peng Zhang, Yan-Qiu Zhang, Chao Zheng, Shi-Jie Zheng, Shu-Mei Jia, Xiang Ma, Jin Wang, Hai-Sheng Zhao, Yong Chen, Cong-Zhan Liu, Yu-Peng Xu, Li-Ming Song and Shuang-Nan Zhang","doi":"10.3847/2041-8213/ae422b","DOIUrl":"https://doi.org/10.3847/2041-8213/ae422b","url":null,"abstract":"SGR J1935+2154 is the so-far unique magnetar from which fast radio bursts (FRBs) have been detected. In 2022 October, it resumed its burst activity, and we implemented a dedicated target-of-opportunity observation on it from 2022 October 13 to November 1 (about 940 ks in total) with Insight-HXMT, while the KM40m radio telescope has observed this source for about 1400 hr since October 15. We searched the data of Low Energy (LE), Medium Energy (ME), and High Energy (HE) X-ray telescopes onboard Insight-HXMT in the overlapping observation time windows with the KM40m radio telescope and revealed 60 magnetar X-ray bursts (MXBs), while KM40m only detected 1 radio burst. In particular, we find that there is an X-ray burst on October 21 (denoted as MXB 221021) temporally associated with this radio burst. Interestingly, this association event shows very different morphology from the X-ray and radio association events from this source reported before (e.g., MXB/FRB 200428). Moreover, we systematically analyzed the temporal and spectral properties of the sample of MXBs during this observation and found that the (radio-associated) MXB 221021 shows some different properties from other MXBs without associated radio bursts. These findings shed new light on the physical mechanisms of X-ray bursts and radio burst emission in magnetars.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146222773","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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