Koushik Chatterjee, Ziri Younsi, Prashant Kocherlakota and Ramesh Narayan
{"title":"On the Universality of Energy Extraction from Black Hole Spacetimes","authors":"Koushik Chatterjee, Ziri Younsi, Prashant Kocherlakota and Ramesh Narayan","doi":"10.3847/2041-8213/ae0740","DOIUrl":"https://doi.org/10.3847/2041-8213/ae0740","url":null,"abstract":"The launching of astrophysical jets provides the most compelling observational evidence for direct extraction of black hole (BH) spin energy via the Blandford–Znajek (BZ) mechanism. While it is known that spinning Kerr BHs within general relativity (GR) follow the BZ jet power relation, the nature of BH energy extraction in general theories of gravity has not been adequately addressed. This study performs the first comprehensive investigation of the BZ jet power relation by utilizing a generalized BH spacetime geometry that describes parametric deviations from the Kerr metric of GR yet recovers the Kerr metric in the limit where all deviation parameters vanish. Through performing and analyzing an extensive suite of three-dimensional covariant magnetohydrodynamics simulations of magnetized gas accretion onto these generalized BH spacetimes, we find that the BZ jet power relation still holds, in some instances yielding jet powers far in excess of what can be produced by even extremal Kerr BHs. It is shown that independent variation of the frame-dragging rate of the BH can enhance or suppress the effects of BH spin, and by extension, of frame-dragging. This variation greatly enhances or suppresses the observed jet power and underlying photon ring image asymmetry, introducing a previously unexplored yet important degeneracy in BH parameter inference. Finally, we show that sufficiently accurate measurements of the jet power, accretion rate, and photon ring properties from supermassive BHs can potentially break this degeneracy, highlighting the need of independent investigations of BH frame dragging from observations.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"214 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145195142","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}
Eduard P. Kontar, A. Gordon Emslie, Daniel L. Clarkson and Alexander Pitňa
{"title":"Ion-scale Turbulence and Energy Cascade Rate in the Solar Corona and Inner Heliosphere","authors":"Eduard P. Kontar, A. Gordon Emslie, Daniel L. Clarkson and Alexander Pitňa","doi":"10.3847/2041-8213/ae09b0","DOIUrl":"https://doi.org/10.3847/2041-8213/ae09b0","url":null,"abstract":"Plasma turbulence cascading from MHD to kinetic scales in the heliospheric plasma is believed to play a key role in coronal heating and fast solar wind acceleration, but the properties of the turbulence remain poorly constrained by observations. Here we compare the ion-scale density fluctuation levels inferred from the properties of solar radio bursts with the magnetic field fluctuation levels obtained through in situ measurements in the inner heliosphere. We find that the observed magnetic and density fluctuation amplitudes are consistent with excitation by kinetic Alfvén waves (KAWs) and/or KAW structures over a broad range of distances from the Sun. We then use the radio diagnostics and the KAW scenario to deduce the radial variation of magnetic fluctuation amplitudes in regions close to the Sun where in situ measurements cannot be obtained. Further, we calculate the energy cascade rate (plasma heating rate) profile over a region that extends from the low corona (∼0.1 R⊙) into the heliosphere (out to ∼1 au), and compare it to the energy deposition rate required to drive the solar wind. The cascade rate agrees with the available in situ measurements and also provides predictions closer than ∼10 R⊙ where in situ approaches are not available. The results provide unique diagnostics of the ion-scale plasma turbulence amplitude and energy cascade rate spanning over 3 orders of magnitude in solar distance.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145195143","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}
Qiuhan He, Andrew Robertson, James W. Nightingale, Aristeidis Amvrosiadis, Shaun Cole, Carlos S. Frenk, Samuel C. Lange, Shubo Li, Ran Li, Xiaoyue Cao, Leo W. H. Fung, Xianghao Ma, Richard Massey, Kaihao Wang and Maximilian von Wietersheim-Kramsta
{"title":"Not So Dark, Not So Dense: An Alternative Explanation for the Lensing Subhalo in SDSS J0946+1006","authors":"Qiuhan He, Andrew Robertson, James W. Nightingale, Aristeidis Amvrosiadis, Shaun Cole, Carlos S. Frenk, Samuel C. Lange, Shubo Li, Ran Li, Xiaoyue Cao, Leo W. H. Fung, Xianghao Ma, Richard Massey, Kaihao Wang and Maximilian von Wietersheim-Kramsta","doi":"10.3847/2041-8213/ae072d","DOIUrl":"https://doi.org/10.3847/2041-8213/ae072d","url":null,"abstract":"Previous studies of the strong-lens system SDSS J0946+1006 have reported a dark matter subhalo with an unusually high central density, potentially challenging the standard cold dark matter (CDM) paradigm. However, most analyses have assumed the subhalo to be completely dark, neglecting the possibility that it may host a faint galaxy. In this work, we revisit the lensing analysis of SDSS J0946+1006, explicitly modelling the subhalo as a luminous satellite. Incorporating light from the perturber broadens the range of allowed subhalo properties, revealing solutions with significantly lower central densities that are consistent with CDM expectations. The inferred luminosity of the satellite also aligns with predictions from hydrodynamical simulations. While high-concentration subhalos remain allowed, they are no longer statistically preferred. The luminous subhalo model yields a better fit to the data, while also offering a more plausible explanation that is in line with theoretical expectations. We validate our methodology using mock data, demonstrating that neglecting subhalo light can lead to inferred mass distributions that are artificially compact.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188711","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}
{"title":"High-redshift Merger-induced Bar-like Galaxies in IllustrisTNG","authors":"Ewa L. Łokas","doi":"10.3847/2041-8213/ae07c2","DOIUrl":"https://doi.org/10.3847/2041-8213/ae07c2","url":null,"abstract":"Recent discoveries made with JWST observations include a significant number of barred galaxies at high redshift. Their origin remains unclear, and their presence seems difficult to reproduce in cosmological simulations of galaxy formation and evolution. In this Letter, I present four examples of high-redshift bars selected from a sample of bar-like galaxies studied previously using IllustrisTNG simulations. All the galaxies formed their bars at redshifts z > 3 via mergers with smaller satellites, although one had its bar formed even earlier, at z > 5. The bars were born long, with lengths on the order of 3 kpc, and grew in time. Three of the four galaxies were later accreted by clusters and underwent multiple interactions with their respective brightest cluster galaxies. Their bar strength was to some extent affected by these interactions, but all the galaxies preserved their bar-like shape until the present time. By the end of the evolution, all the galaxies lost their gas and stopped forming stars; they retained essentially no disk component and were no longer rotationally supported. The examples demonstrate that high-z bars do not evolve into present-day barred disk galaxies similar to the Milky Way but rather into S0s or ellipticals typically found in galaxy clusters.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188712","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}
Zexi Xing, Shawn Oset, John Noonan and Dennis Bodewits
{"title":"Water Production Rates of the Interstellar Object 3I/ATLAS","authors":"Zexi Xing, Shawn Oset, John Noonan and Dennis Bodewits","doi":"10.3847/2041-8213/ae08ab","DOIUrl":"https://doi.org/10.3847/2041-8213/ae08ab","url":null,"abstract":"We report the detection of water activity in the third confirmed interstellar object, 3I/ATLAS, based on ultraviolet imaging with the Neil Gehrels Swift Observatory’s Ultraviolet/Optical Telescope. Assuming a reddening of 29% between 3325.7 and 5437.8 Å, measurements on 2025 July 31–August 1 yielded a first, marginal detection of OH (A2Σ–X2Π) emission near 3085 Å, corresponding to a water production rate of (0.74 ± 0.50) × 1027 molecules s−1. The subsequent visit on 2025 August 18–20 revealed a clear OH detection, implying a higher water production rate of (1.36 ± 0.35) × 1027 molecules s−1 (40 kg s−1) at a heliocentric distance of 2.90 au. This places 3I/ATLAS among the few comets with confirmed OH emission beyond 2.5 au, where water ice sublimation from the nucleus is typically inefficient. The inferred production rate at 2.9 au implies an active area of at least 7.8 km2, assuming equilibrium sublimation. This requires that over 8% of the surface is active, which is larger than activity levels observed in most solar system comets. Contemporaneous near-infrared spectroscopy indicated the presence of icy grains in the coma, which may serve as an extended source of water vapor.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188714","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}
Adnan Ali Ahmad, Benot Commerçon, Gilles Chabrier and Antonin Borderies
{"title":"Brown Dwarf Formation through Gravitational Collapse: Insights from 3D Numerical Simulations","authors":"Adnan Ali Ahmad, Benot Commerçon, Gilles Chabrier and Antonin Borderies","doi":"10.3847/2041-8213/ae0640","DOIUrl":"https://doi.org/10.3847/2041-8213/ae0640","url":null,"abstract":"The formation mechanism of brown dwarfs (BDs), whether akin to stars or ejected planetary-mass objects, remains debated. We present the first 3D radiation-MHD simulations of magnetized, turbulent, gravitationally unstable low-mass cores (0.05–0.1M⊙) collapsing into proto-BDs. Using the RAMSES code with adaptive mesh refinement, we model the full dynamical range (105–1022 cm−3), including radiative transfer (flux limited diffusion) and nonideal MHD (ambipolar diffusion). Our simulations self-consistently follow the isothermal collapse, first hydrostatic core formation, H2 dissociation, and BD birth. The resulting BDs have initial radii ≈0.75 R⊙ and masses ≈0.8 MJup, growing via accretion as we follow the early evolution of the object. Crucially, we find that BDs may form similarly to low-mass stars but with a prolonged first-core phase, supporting a starlike formation scenario.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188710","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}
Yi Dai, Xiansheng Zheng, Xinping Zhou, Linqiao Jiang, Jie Zheng, Haiyin Qing and Zhining Qu
{"title":"Coexistence of Decaying and Decayless Kink Oscillations in a Bundle of Coronal Loops Triggered by an X6.3 Solar Flare","authors":"Yi Dai, Xiansheng Zheng, Xinping Zhou, Linqiao Jiang, Jie Zheng, Haiyin Qing and Zhining Qu","doi":"10.3847/2041-8213/ae046c","DOIUrl":"https://doi.org/10.3847/2041-8213/ae046c","url":null,"abstract":"We report the coexistence of decaying and decayless kink oscillations within a single bundle of coronal loops during the X6.3-class solar flare on 2024 February 22. Using coordinated observations from Geostationary Operational Environmental Satellite, Solar Dynamics Observatory/Atmospheric Imaging Assembly, Advanced Space-based Solar Observatory, and New Vacuum Solar Telescope, we analyze five flare-activated coronal loops (S1–S5) and identify distinct oscillation regimes in different segments. Time–distance and curve-fitting analyses of the five selected coronal loops reveal a broad range of oscillation amplitudes (1.1–7.1 Mm) and periods (119–630 s). In loop S2, decayless oscillations with a period of 274.6 ± 1.0 s and nearly constant amplitude are observed to coexist for a period of time with rapidly decaying oscillations of a similar period, 271.1 ± 1.7 s. The differential emission measure diagnostics indicate strong spatial variation in magnetic field strength, decreasing from 30 G near the flare core to 11 G in the peripheral loops. These variations in oscillation regimes and magnetic field strength imply that the local plasma environment strongly influences wave decaying processes. These results suggest that magnetic topology and local plasma conditions play a key role in modulating the wave decaying behavior.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"105 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188680","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}
Thomas S.-Y. Lai, 劭愉 賴, Sara Duval, J. D. T. Smith, Lee Armus, Adolf N. Witt, Karin Sandstrom, Elizabeth Tarantino, Shunsuke Baba, Alberto Bolatto, Grant P. Donnelly, Brandon S. Hensley, Masatoshi Imanishi, Laura Lenkic, Sean Linden, Takao Nakagawa, Henrik W. W. Spoon, Aditya Togi and Cory M. Whitcomb
{"title":"Resolving Emission from Small Dust Grains in the Blue Compact Dwarf II Zw 40 with JWST","authors":"Thomas S.-Y. Lai, 劭愉 賴, Sara Duval, J. D. T. Smith, Lee Armus, Adolf N. Witt, Karin Sandstrom, Elizabeth Tarantino, Shunsuke Baba, Alberto Bolatto, Grant P. Donnelly, Brandon S. Hensley, Masatoshi Imanishi, Laura Lenkic, Sean Linden, Takao Nakagawa, Henrik W. W. Spoon, Aditya Togi and Cory M. Whitcomb","doi":"10.3847/2041-8213/ae0467","DOIUrl":"https://doi.org/10.3847/2041-8213/ae0467","url":null,"abstract":"We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) and Mid-infrared Instrument integral field spectroscopy of the nearby blue compact dwarf II Zw 40, which has a low metallicity of 25% of solar. Leveraging the high spatial/spectral resolution and wavelength coverage of JWST/NIRSpec, we present robust detections of the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission on 20 pc scales. The strength of the Pfδ emission relative to the 3.3 PAH feature is significantly stronger than typical higher-metallicity star-forming galaxies. We find that 3.3 μm PAH emission is concentrated near the northern super star cluster and is cospatial with CO gas. A strong correlation exists between the 3.3/11.3 PAH ratio and radiation hardness probed by [Ne iii]/[Ne ii], providing evidence of photodestruction of PAH molecules in intense radiation environments. Our analysis shows that while the overall PAH fraction is lower in II Zw 40 than in higher-metallicity galaxies, the contribution of the 3.3 μm PAH feature to the total PAH emission is higher. We propose that the PAH size distribution is fundamentally shaped by two competing mechanisms in low-metallicity environments: photodestruction and inhibited growth. Additionally, the high radiation field intensity in II Zw 40 suggests that multiphoton heating of PAHs may be an important effect. As one of the first spatially resolved studies of aromatic emission in a low-metallicity environment, our spectroscopic results offer practical guidance for future observations of the 3.3 μm PAH feature in low-metallicity galaxies using JWST.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188708","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}
{"title":"Orbital Eccentricity and Spin–Orbit Misalignment Are Evidence that Neutron Star–Black Hole Mergers Form through Triple Star Evolution","authors":"Jakob Stegmann and Jakub Klencki","doi":"10.3847/2041-8213/ae055b","DOIUrl":"https://doi.org/10.3847/2041-8213/ae055b","url":null,"abstract":"There is growing evidence that a substantial fraction of the neutron star–black holes (NSBHs) detected through gravitational waves merge with nonzero eccentricity or large black hole spin–orbit misalignment. This is in tension with leading formation scenarios to date. Residual eccentricity rules out formation from isolated binary stars, while neutron star (NS) natal kicks and unequal masses of NSBHs inhibit efficient pairing in dense stellar environments. We report that all observed properties—NSBH merger rate, eccentricity, and spin–orbit misalignment—are explained by the high prevalence of massive stellar triples in the field. Modeling their evolution from the zero-age main sequence, we investigate NSBH mergers caused by gravitational perturbations from a tertiary companion. The NS formation decisively impacts the triple stability, preferentially leaving behind surviving NSBHs in compact triple architectures with mild hierarchies. The rich three-body dynamics of compact, unequal-mass triples enables mergers across a wide range of orbital parameters and provides a natural explanation for an abundance of residual eccentricity and spin–orbit misalignment. We infer a total NSBH merger rate of –23 Gpc−3 yr−1 (within uncertainties on NS kicks) with a few 10% exhibiting residual eccentricity e20 > 0.1 or large spin–orbit misalignment , consistent with current observations. The mergers closely track the cosmic star formation rate due to short delay times (∼10–100 Myr), include a substantial fraction of burst-like highly eccentric systems (e20 > 0.9), and almost universally retain eccentricities e20 > 10−3 detectable by next-generation detectors. If evidence for eccentric and misaligned events solidifies, our results suggest that triple dynamics is the dominant formation channel of gravitational-wave events from NSBH mergers.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188709","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}
Goni Halevi, Swapnil Shankar, Philipp Mösta, Roland Haas and Erik Schnetter
{"title":"A Black Hole Is Born: 3D General-relativistic Magnetohydrodynamic Simulation of Black Hole Formation from Core Collapse","authors":"Goni Halevi, Swapnil Shankar, Philipp Mösta, Roland Haas and Erik Schnetter","doi":"10.3847/2041-8213/ae08a6","DOIUrl":"https://doi.org/10.3847/2041-8213/ae08a6","url":null,"abstract":"We present the first three-dimensional, fully general-relativistic magnetohydrodynamic (3D GRMHD) simulation of a black hole (BH) formed from the collapsed core of a massive star. The ability to self-consistently capture the birth of a compact remnant in 3D is crucial for modeling natal BH properties (including masses, spins, and kicks), which are of particular interest in the era of gravitational-wave astronomy. However, such simulations have remained elusive due to extreme computational challenges and demands. We employ the GPU-accelerated dynamical-spacetime GRMHD code GRaM-X to follow the collapse, core bounce, shock propagation, and eventual BH formation of a massive stellar progenitor in full 3D. We initialize our simulation by mapping a one-dimensional (1D) model of a star with a zero-age-main-sequence mass of 45M⊙ to 3D. We use the core rotation velocity expected from stellar evolution modeling and a relatively weak dipolar magnetic field. The collapsing core drives a shock that reaches a maximum radius of roughly 170 km before stalling and does not lead to a successful explosion. The protoneutron star accretes matter before collapsing to form a BH tBH ≈ 325 ms after core bounce. The time of BH formation and initial BH mass are remarkably similar to those obtained with GR1D, a 1D general-relativistic neutrino-hydrodynamics code, to which we compare our results. We track the horizon of the newborn BH after formation and calculate a steady kick velocity of and a mass of MBH ≈ 2.62M⊙, which is still rising at the end of the simulation.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188713","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}