Pub Date : 2026-03-29DOI: 10.3847/1538-4357/ae4d44
Andrei Igoshev, Nicolás A. Moraga, Andreas Reisenegger, Calum S. Skene and Rainer Hollerbach
Magnetic field evolution in neutron star cores is not fully understood. We describe the field evolution both for one barotropic fluid as well as two collisionally coupled barotropic fluids with different density profiles using the anelastic approximation and the Navier–Stokes equations, to simulate the evolution in three dimensions. In the one-fluid case, a single fluid describes the motion of the charged particles. In the two-fluid model, the neutral fluid is coupled to the electrically conductive fluid by collisions, the latter being dragged by the magnetic field. In this model, both fluids have distinct density profiles. This forces them to move at slightly different velocities, resulting in a relative motion between the two barotropic fluids—ambipolar diffusion. We develop a code based on Dedalus and study the evolution of simple poloidal dipolar and toroidal magnetic fields. Unlike previous 2D studies that found poloidal magnetic fields evolving towards a stable Grad–Shafranov equilibrium, in our 3D simulations, we find an instability. The fastest growing azimuthal harmonics are m = 4 and m = 6 for Re = 2, and m = 2 for Re = 0.1, which might be more relevant for neutron star core conditions. The instability grows on Alfvén timescale. After the instability saturates, a highly nonlinear Lorentz force introduces small-scale fluid motion that leads to turbulence, development of a cascade and significant, non-axially symmetric changes in the magnetic field configuration. Fluid viscosity plays an essential role in regularizing the small-scale fluid motion, providing an energy drain.
{"title":"Three-dimensional Numerical Simulations of Neutron Star Cores in the Two-fluid MHD Approximation: Simple Configurations","authors":"Andrei Igoshev, Nicolás A. Moraga, Andreas Reisenegger, Calum S. Skene and Rainer Hollerbach","doi":"10.3847/1538-4357/ae4d44","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d44","url":null,"abstract":"Magnetic field evolution in neutron star cores is not fully understood. We describe the field evolution both for one barotropic fluid as well as two collisionally coupled barotropic fluids with different density profiles using the anelastic approximation and the Navier–Stokes equations, to simulate the evolution in three dimensions. In the one-fluid case, a single fluid describes the motion of the charged particles. In the two-fluid model, the neutral fluid is coupled to the electrically conductive fluid by collisions, the latter being dragged by the magnetic field. In this model, both fluids have distinct density profiles. This forces them to move at slightly different velocities, resulting in a relative motion between the two barotropic fluids—ambipolar diffusion. We develop a code based on Dedalus and study the evolution of simple poloidal dipolar and toroidal magnetic fields. Unlike previous 2D studies that found poloidal magnetic fields evolving towards a stable Grad–Shafranov equilibrium, in our 3D simulations, we find an instability. The fastest growing azimuthal harmonics are m = 4 and m = 6 for Re = 2, and m = 2 for Re = 0.1, which might be more relevant for neutron star core conditions. The instability grows on Alfvén timescale. After the instability saturates, a highly nonlinear Lorentz force introduces small-scale fluid motion that leads to turbulence, development of a cascade and significant, non-axially symmetric changes in the magnetic field configuration. Fluid viscosity plays an essential role in regularizing the small-scale fluid motion, providing an energy drain.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-29DOI: 10.3847/1538-4357/ae4c51
F. Sánchez-Bajo, V. M. S. Carrasco, A. J. P. Aparicio and J. M. Vaquero
This study examines several sources of uncertainty affecting sunspot area measurements, with particular emphasis on projection effects caused by the curvature of the Sun. Using simple geometric models, we derived analytical and approximate corrections for sunspots with circular and elliptical shapes. Although projection uncertainties are generally small, they become increasingly relevant for large sunspots. Among the various sources of uncertainty, thresholding and perspective effects emerged as the most significant. In contrast, the impact of the image resolution was found to be relatively minor. The corrections proposed here provide a straightforward way to refine area estimates and can be applied to both modern digital data sets and historical sunspot records. This contributes to a more consistent and homogeneous reconstruction of long-term solar activity trends.
{"title":"On the Uncertainties of the Sunspot Area Measurements","authors":"F. Sánchez-Bajo, V. M. S. Carrasco, A. J. P. Aparicio and J. M. Vaquero","doi":"10.3847/1538-4357/ae4c51","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c51","url":null,"abstract":"This study examines several sources of uncertainty affecting sunspot area measurements, with particular emphasis on projection effects caused by the curvature of the Sun. Using simple geometric models, we derived analytical and approximate corrections for sunspots with circular and elliptical shapes. Although projection uncertainties are generally small, they become increasingly relevant for large sunspots. Among the various sources of uncertainty, thresholding and perspective effects emerged as the most significant. In contrast, the impact of the image resolution was found to be relatively minor. The corrections proposed here provide a straightforward way to refine area estimates and can be applied to both modern digital data sets and historical sunspot records. This contributes to a more consistent and homogeneous reconstruction of long-term solar activity trends.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147536578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4722
Vishal Verma and Quinn Minor
One of the biggest challenges in cosmology, the Hubble tension, requires independent measurements of H0, and strong lensing with time-delay cosmography is a promising avenue. The inclusion of spatially resolved kinematic data helps break the mass–sheet degeneracy, a key limitation in strong lensing. Kinematics, however, suffers from its own degeneracy due to unknown stellar velocity anisotropy, which can bias galaxy mass profile inferences. We investigate the bias in H0 using a sample of 10 massive elliptical galaxies at z = 0.2 from the Illustris TNG100 simulations. We generate mock line-of-sight velocity-dispersion maps resembling JWST NIRSpec observations and test four anisotropy models: Osipkov–Merritt (OM), Mamon–Łokas (ML), constant β, and a generalized–OM (gOM) profile, under both kinematics-only and joint kinematics plus strong lensing analyses. We find a subpercent average bias in H0 across 10 galaxies with joint modeling for three models: +0.2% ± 1.6% (ML), −0.9% ± 1.9% (constant) and −0.9% ± 1.6% (gOM), with ∼5% scatter. Joint modeling reduces bias, improves precision, and mitigates outlier results. Overall, the gOM model best recovers galaxy parameters and delivers the most accurate H0 relative to posterior uncertainties considering both analyses. However, the single-parameter OM model produces large systematic biases: with kinematics-only data, H0 errors can exceed 20%, and even with joint modeling, it produces an overall bias of +11.5% ± 1.3% (OM). The higher bias in OM is thus unlikely to average out across an ensemble of galaxies. Our findings highlight the impact of anisotropy assumptions on H0 inference, and more broadly, in galaxy dynamics.
{"title":"The Stellar Velocity Anisotropy of Strong Lensing Massive Elliptical Galaxies and Its Role in the Inference of the Hubble Parameter H 0 Using Spatially Resolved Kinematics","authors":"Vishal Verma and Quinn Minor","doi":"10.3847/1538-4357/ae4722","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4722","url":null,"abstract":"One of the biggest challenges in cosmology, the Hubble tension, requires independent measurements of H0, and strong lensing with time-delay cosmography is a promising avenue. The inclusion of spatially resolved kinematic data helps break the mass–sheet degeneracy, a key limitation in strong lensing. Kinematics, however, suffers from its own degeneracy due to unknown stellar velocity anisotropy, which can bias galaxy mass profile inferences. We investigate the bias in H0 using a sample of 10 massive elliptical galaxies at z = 0.2 from the Illustris TNG100 simulations. We generate mock line-of-sight velocity-dispersion maps resembling JWST NIRSpec observations and test four anisotropy models: Osipkov–Merritt (OM), Mamon–Łokas (ML), constant β, and a generalized–OM (gOM) profile, under both kinematics-only and joint kinematics plus strong lensing analyses. We find a subpercent average bias in H0 across 10 galaxies with joint modeling for three models: +0.2% ± 1.6% (ML), −0.9% ± 1.9% (constant) and −0.9% ± 1.6% (gOM), with ∼5% scatter. Joint modeling reduces bias, improves precision, and mitigates outlier results. Overall, the gOM model best recovers galaxy parameters and delivers the most accurate H0 relative to posterior uncertainties considering both analyses. However, the single-parameter OM model produces large systematic biases: with kinematics-only data, H0 errors can exceed 20%, and even with joint modeling, it produces an overall bias of +11.5% ± 1.3% (OM). The higher bias in OM is thus unlikely to average out across an ensemble of galaxies. Our findings highlight the impact of anisotropy assumptions on H0 inference, and more broadly, in galaxy dynamics.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4742
Yang Huang, 样 黄, Timothy C. Beers, Kai Xiao, 凯 肖, C. Mendes de Oliveira, Felipe Almeida-Fernandes, G.B. Oliveira Schwarz, Young Sun Lee, Jihye Hong, Huiling Chen, 慧玲 陈, Huawei Zhang, 华伟 张, Guilherme Limberg, Maiara S. Carvalho, Pedro K. Humire, André Luiz Figueiredo, Bruno Dias, Alvaro Alvarez-Candal, Marcos Fonseca-Faria, A. Kanaan, T. Ribeiro, W. Schoenell and Silvia Rossi
We combine narrow/medium-band filter photometry from the Southern Photometric Local Universe Survey (S-PLUS) DR4 with ultrabroadband filter photometry from Gaia EDR3 to derive fundamental stellar parameters (Teff, , [Fe/H], and ages) and elemental-abundance ratios ([C/Fe] and [α/Fe]) for 5.4 million stars in the Galaxy (4.9 million dwarfs and 0.5 million giants), as well as for over 0.7 million red giant stars in the Large and Small Magellanic Clouds (LMC and SMC). The precisions of the abundance estimates range from 0.05 to 0.10 dex for metallicity in the relatively metal-rich range ([Fe/H] > −1.0) to 0.10–0.30 dex in the metal-poor regime ([Fe/H] < −1.0), 0.10–0.20 dex for [C/Fe], and 0.05 dex for [α/Fe]. The stellar parameters for LMC and SMC member stars are somewhat less precise than those from the S-PLUS main survey, primarily because of the effect of high reddening. The use of both metallicity- and carbon-sensitive filters provides unbiased measurements of both [Fe/H] and [C/Fe], of particular importance for very low-metallicity ([Fe/H] < −2.0) stars, where carbon enhancement can lead to systematically high estimates of [Fe/H] when only a single metallicity-sensitive filter is employed. Furthermore, multiple narrowband filters enable metallicity estimates down to [Fe/H] ∼ −4.0 with an accuracy of around 0.3 dex, exceeding the precision typically achieved by low/medium-resolution spectroscopy. This extensive photometric data set, combined with the other three data sets in this series, will serve as a valuable legacy resource for Milky Way and Magellanic Clouds studies.
{"title":"S-PLUS: Beyond Spectroscopy. IV. Stellar Parameters and Elemental-abundance Ratios for Six Million Stars from DR4 and First Results for the Magellanic Clouds","authors":"Yang Huang, 样 黄, Timothy C. Beers, Kai Xiao, 凯 肖, C. Mendes de Oliveira, Felipe Almeida-Fernandes, G.B. Oliveira Schwarz, Young Sun Lee, Jihye Hong, Huiling Chen, 慧玲 陈, Huawei Zhang, 华伟 张, Guilherme Limberg, Maiara S. Carvalho, Pedro K. Humire, André Luiz Figueiredo, Bruno Dias, Alvaro Alvarez-Candal, Marcos Fonseca-Faria, A. Kanaan, T. Ribeiro, W. Schoenell and Silvia Rossi","doi":"10.3847/1538-4357/ae4742","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4742","url":null,"abstract":"We combine narrow/medium-band filter photometry from the Southern Photometric Local Universe Survey (S-PLUS) DR4 with ultrabroadband filter photometry from Gaia EDR3 to derive fundamental stellar parameters (Teff, , [Fe/H], and ages) and elemental-abundance ratios ([C/Fe] and [α/Fe]) for 5.4 million stars in the Galaxy (4.9 million dwarfs and 0.5 million giants), as well as for over 0.7 million red giant stars in the Large and Small Magellanic Clouds (LMC and SMC). The precisions of the abundance estimates range from 0.05 to 0.10 dex for metallicity in the relatively metal-rich range ([Fe/H] > −1.0) to 0.10–0.30 dex in the metal-poor regime ([Fe/H] < −1.0), 0.10–0.20 dex for [C/Fe], and 0.05 dex for [α/Fe]. The stellar parameters for LMC and SMC member stars are somewhat less precise than those from the S-PLUS main survey, primarily because of the effect of high reddening. The use of both metallicity- and carbon-sensitive filters provides unbiased measurements of both [Fe/H] and [C/Fe], of particular importance for very low-metallicity ([Fe/H] < −2.0) stars, where carbon enhancement can lead to systematically high estimates of [Fe/H] when only a single metallicity-sensitive filter is employed. Furthermore, multiple narrowband filters enable metallicity estimates down to [Fe/H] ∼ −4.0 with an accuracy of around 0.3 dex, exceeding the precision typically achieved by low/medium-resolution spectroscopy. This extensive photometric data set, combined with the other three data sets in this series, will serve as a valuable legacy resource for Milky Way and Magellanic Clouds studies.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4b35
David Afonso Delgado, Rebecca Centeno, Roberto Casini and Matthias Rempel
We investigate the suitability of the combined spectral windows of Mg iih and k and the Fe ii lines around 261 nm as magnetic markers of filament formation. Using two magnetohydrodynamic simulations representative of a magnetic flux rope (MFR) and a sheared magnetic arcade (SMA), we model the spectropolarimetric signals of the Mg iih and k resonant doublet and five Fe ii spectral lines (260.018, 261.265, 261.460, 262.119, and 262.25 nm) and degrade them following the instrumental specification proposed for the Chromospheric Magnetism Explorer (CMEx) imitating an eventual observation. We apply the weak-field approximation (WFA) to these theoretical observations and analyze its suitability to infer the magnetic field stratification through the solar chromosphere. We demonstrate that the application of the WFA to the Mg ii and Fe ii enables us to robustly discriminate between the relatively weak magnetic gradient below the MFR and the much stronger vertical gradient associated with the SMA, providing the observables and techniques needed to distinguish between these two magnetic configurations. This result provides a methodology to validate or refute current models of solar filament formation and determine how and when an SMA evolves into an MFR, which is thought to be a necessary condition prior to certain types of solar eruptions.
{"title":"Near-ultraviolet Spectropolarimetry as a Tracer of Magnetic Markers of Flux Rope Formation","authors":"David Afonso Delgado, Rebecca Centeno, Roberto Casini and Matthias Rempel","doi":"10.3847/1538-4357/ae4b35","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4b35","url":null,"abstract":"We investigate the suitability of the combined spectral windows of Mg iih and k and the Fe ii lines around 261 nm as magnetic markers of filament formation. Using two magnetohydrodynamic simulations representative of a magnetic flux rope (MFR) and a sheared magnetic arcade (SMA), we model the spectropolarimetric signals of the Mg iih and k resonant doublet and five Fe ii spectral lines (260.018, 261.265, 261.460, 262.119, and 262.25 nm) and degrade them following the instrumental specification proposed for the Chromospheric Magnetism Explorer (CMEx) imitating an eventual observation. We apply the weak-field approximation (WFA) to these theoretical observations and analyze its suitability to infer the magnetic field stratification through the solar chromosphere. We demonstrate that the application of the WFA to the Mg ii and Fe ii enables us to robustly discriminate between the relatively weak magnetic gradient below the MFR and the much stronger vertical gradient associated with the SMA, providing the observables and techniques needed to distinguish between these two magnetic configurations. This result provides a methodology to validate or refute current models of solar filament formation and determine how and when an SMA evolves into an MFR, which is thought to be a necessary condition prior to certain types of solar eruptions.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4e1f
Mitsuo Oka, Alexander J. B. Russell, Yuki Harada, Seiji Zenitani, Tai D. Phan, Marit Øieroset, Steven J. Schwartz, Tetsu Anan, Abhishek Rajhans, Hiroshi Tanabe and Yasushi Ono
Particles are energized—heated and accelerated to nonthermal energies—in laboratory, space, solar, and astrophysical plasmas. In collisionless plasmas, ion and electron temperatures are often unequal and cannot be fully understood within the framework of magnetohydrodynamics (MHD). In this context, a relation, Δεs = qsVBLs, for each species can be useful, where Δεs is the energy gain for species s, measured in the plasma rest frame, relative to the upstream region of shocks and magnetic reconnection; qs is the charge; V is the plasma bulk flow speed; B is the magnetic field strength; and Ls is a characteristic length scale of energization. From this relation, we recently derived semiempirical scalings for ion and electron temperature increases across shocks and magnetic reconnection in Earth’s plasma environment. However, it remains unclear how broadly these scalings apply. Here we show that the same scalings explain temperature increases in other plasma environments such as laboratory experiments, planetary magnetospheres, solar flares, and supernova remnant shocks. Combined with another recent report that the maximum energy of particles in various plasma environments follows the same relation when Ls is taken as the system size, our results indicate that Δεs = qsVBLs provides a novel framework that universally captures particle energization—both heating and acceleration to nonthermal energies. Additionally, the scaling captures the essential MHD trends while revealing systematic deviations that point to kinetic effects beyond fluid models, highlighting promising directions for theoretical and simulation studies.
{"title":"Universality of the Scaling Law for Particle Energization in Collisionless Plasmas","authors":"Mitsuo Oka, Alexander J. B. Russell, Yuki Harada, Seiji Zenitani, Tai D. Phan, Marit Øieroset, Steven J. Schwartz, Tetsu Anan, Abhishek Rajhans, Hiroshi Tanabe and Yasushi Ono","doi":"10.3847/1538-4357/ae4e1f","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4e1f","url":null,"abstract":"Particles are energized—heated and accelerated to nonthermal energies—in laboratory, space, solar, and astrophysical plasmas. In collisionless plasmas, ion and electron temperatures are often unequal and cannot be fully understood within the framework of magnetohydrodynamics (MHD). In this context, a relation, Δεs = qsVBLs, for each species can be useful, where Δεs is the energy gain for species s, measured in the plasma rest frame, relative to the upstream region of shocks and magnetic reconnection; qs is the charge; V is the plasma bulk flow speed; B is the magnetic field strength; and Ls is a characteristic length scale of energization. From this relation, we recently derived semiempirical scalings for ion and electron temperature increases across shocks and magnetic reconnection in Earth’s plasma environment. However, it remains unclear how broadly these scalings apply. Here we show that the same scalings explain temperature increases in other plasma environments such as laboratory experiments, planetary magnetospheres, solar flares, and supernova remnant shocks. Combined with another recent report that the maximum energy of particles in various plasma environments follows the same relation when Ls is taken as the system size, our results indicate that Δεs = qsVBLs provides a novel framework that universally captures particle energization—both heating and acceleration to nonthermal energies. Additionally, the scaling captures the essential MHD trends while revealing systematic deviations that point to kinetic effects beyond fluid models, highlighting promising directions for theoretical and simulation studies.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4c50
Sarbani Basu, Sylvain G. Korzennik and Sushanta C. Tripathy
We have examined how the characteristics of the tachocline—i.e., the change in rotation rate δΩ, or the “jump,” the position of the midpoint of the tachocline, rd, and the width of the tachocline, wd—change as a function of time at different latitudes using 30 yr of helioseismic data obtained by the GONG network. We find a statistically significant change in the jump; however, these changes do not have a simple correlation with solar activity. The dependence is different for Solar Cycles 23 and 24, and for Cycle 25, it is more similar to that of Cycle 24. While our measured changes of the tachocline’s width with time are marginally statistically significant, the cross correlation is statistically significant and implies that the width is larger when the solar activity is smaller, suggesting that magnetic fields play a role in confining the tachocline. The position of the tachocline shows a significant secular change at low latitudes (≲50°). At these latitudes, the tachocline has been moving steadily closer to the base of the convection zone. This is consistent with other measurements that have shown that the overall complexity of solar activity has been decreasing over the last few decades. It leads us to speculate that strong magnetic fields tend to push the tachocline deeper into the radiative zone.
{"title":"Latitude-dependent Time Variations of the Solar Tachocline","authors":"Sarbani Basu, Sylvain G. Korzennik and Sushanta C. Tripathy","doi":"10.3847/1538-4357/ae4c50","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c50","url":null,"abstract":"We have examined how the characteristics of the tachocline—i.e., the change in rotation rate δΩ, or the “jump,” the position of the midpoint of the tachocline, rd, and the width of the tachocline, wd—change as a function of time at different latitudes using 30 yr of helioseismic data obtained by the GONG network. We find a statistically significant change in the jump; however, these changes do not have a simple correlation with solar activity. The dependence is different for Solar Cycles 23 and 24, and for Cycle 25, it is more similar to that of Cycle 24. While our measured changes of the tachocline’s width with time are marginally statistically significant, the cross correlation is statistically significant and implies that the width is larger when the solar activity is smaller, suggesting that magnetic fields play a role in confining the tachocline. The position of the tachocline shows a significant secular change at low latitudes (≲50°). At these latitudes, the tachocline has been moving steadily closer to the base of the convection zone. This is consistent with other measurements that have shown that the overall complexity of solar activity has been decreasing over the last few decades. It leads us to speculate that strong magnetic fields tend to push the tachocline deeper into the radiative zone.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae355e
Tri L. Astraatmadja, Andrew S. Fruchter, Susana E. Deustua, Helen Qu, Masao Sako, Russell E. Ryan, Yannick Copin, Greg Aldering, Rebekah A. Hounsell, David Rubin, Lluís Galbany, Saul Perlmutter and Benjamin M. Rose
The Nancy Grace Roman Space Telescope will carry out a wide-field imaging and slitless spectroscopic survey of Type Ia supernovae to improve our understanding of dark energy. Crucial to this endeavor is obtaining supernova spectra uncontaminated by light from their host galaxies. However, obtaining such spectra is made more difficult by the inherent problem in wide-field slitless spectroscopic surveys: the blending of spectra of close objects. The spectrum of a supernova will blend with the host galaxy, even from regions distant from the supernova on the sky. If not properly removed, this contamination will introduce systematic bias when the supernova spectra are later used to determine intrinsic supernova parameters and to infer the parameters of dark energy. To address this problem, we developed an algorithm that makes use of the spectroscopic observations of the host galaxy at all available observatory roll angles to reconstruct a 3D (2D spatial, 1D spectral) representation of the underlying host galaxy that accurately matches the 2D slitless spectrum of the host galaxy when projected to an arbitrary rotation angle. We call this “scene reconstruction.” The projection of the reconstructed scene can be subtracted from an observation of a supernova to remove the contamination from the underlying host. Using simulated Roman data, we show that our method has extremely small systematic errors and significantly less random noise than if we subtracted a single perfectly aligned spectrum of the host obtained before or after the supernova was visible.
{"title":"Three-dimensional Scene Reconstruction Using Roman Slitless Spectra","authors":"Tri L. Astraatmadja, Andrew S. Fruchter, Susana E. Deustua, Helen Qu, Masao Sako, Russell E. Ryan, Yannick Copin, Greg Aldering, Rebekah A. Hounsell, David Rubin, Lluís Galbany, Saul Perlmutter and Benjamin M. Rose","doi":"10.3847/1538-4357/ae355e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae355e","url":null,"abstract":"The Nancy Grace Roman Space Telescope will carry out a wide-field imaging and slitless spectroscopic survey of Type Ia supernovae to improve our understanding of dark energy. Crucial to this endeavor is obtaining supernova spectra uncontaminated by light from their host galaxies. However, obtaining such spectra is made more difficult by the inherent problem in wide-field slitless spectroscopic surveys: the blending of spectra of close objects. The spectrum of a supernova will blend with the host galaxy, even from regions distant from the supernova on the sky. If not properly removed, this contamination will introduce systematic bias when the supernova spectra are later used to determine intrinsic supernova parameters and to infer the parameters of dark energy. To address this problem, we developed an algorithm that makes use of the spectroscopic observations of the host galaxy at all available observatory roll angles to reconstruct a 3D (2D spatial, 1D spectral) representation of the underlying host galaxy that accurately matches the 2D slitless spectrum of the host galaxy when projected to an arbitrary rotation angle. We call this “scene reconstruction.” The projection of the reconstructed scene can be subtracted from an observation of a supernova to remove the contamination from the underlying host. Using simulated Roman data, we show that our method has extremely small systematic errors and significantly less random noise than if we subtracted a single perfectly aligned spectrum of the host obtained before or after the supernova was visible.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae48f9
Alberto Magaraggia and Nico Cappelluti
The detection of subsolar mass black holes is a milestone of modern astrophysics as it would open a window either onto new stellar physics or could potentially unveil the nature of dark matter as primordial black holes (PBHs). On 2025 November 12, the LIGO–Virgo–KAGRA (LVK) collaboration reported the compact binary merger candidate S251112cm, a system with no obvious electromagnetic counterpart, consistent with binary black hole merger with a chirp mass in the range 0.1–0.87 M⊙. The probability that at least one component has mass <1 M⊙ is >99%. Inspired by this trigger, we tested if a population of PBHs formed at the quantum chromodynamics epoch with a broad mass function could account for a signal of this type. Our results, corresponding to a predicted event rate of 0.8 yr−1 as seen by LVK O3b, suggest that the observed merger rate of if the trigger is confirmed as an astrophysical event would be compatible with such a model. Our predicted detection rate is also in agreement with current LVK expectations for stellar-mass binaries, remaining consistent with a scenario in which a nonnegligible fraction of the 3–200 M⊙ mergers observed by LVK originate from PBHs. If confirmed, this detection would place a lower limit to the PBH abundance fPBH > 0.04 for our adopted model.
{"title":"Implications for Primordial Black Hole Dark Matter from a Single Subsolar Mass Gravitational-wave Detection in LVK O1–O4","authors":"Alberto Magaraggia and Nico Cappelluti","doi":"10.3847/1538-4357/ae48f9","DOIUrl":"https://doi.org/10.3847/1538-4357/ae48f9","url":null,"abstract":"The detection of subsolar mass black holes is a milestone of modern astrophysics as it would open a window either onto new stellar physics or could potentially unveil the nature of dark matter as primordial black holes (PBHs). On 2025 November 12, the LIGO–Virgo–KAGRA (LVK) collaboration reported the compact binary merger candidate S251112cm, a system with no obvious electromagnetic counterpart, consistent with binary black hole merger with a chirp mass in the range 0.1–0.87 M⊙. The probability that at least one component has mass <1 M⊙ is >99%. Inspired by this trigger, we tested if a population of PBHs formed at the quantum chromodynamics epoch with a broad mass function could account for a signal of this type. Our results, corresponding to a predicted event rate of 0.8 yr−1 as seen by LVK O3b, suggest that the observed merger rate of if the trigger is confirmed as an astrophysical event would be compatible with such a model. Our predicted detection rate is also in agreement with current LVK expectations for stellar-mass binaries, remaining consistent with a scenario in which a nonnegligible fraction of the 3–200 M⊙ mergers observed by LVK originate from PBHs. If confirmed, this detection would place a lower limit to the PBH abundance fPBH > 0.04 for our adopted model.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"220 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The physical quantities that directly regulate active galactic nucleus (AGN) feedback in massive galaxies remain poorly understood. Observations of molecular gas surrounding AGNs suggest that this gas serves as a fuel source for AGN activity. Accordingly, we study the relationship between AGN activity and molecular gas properties. In this study, we analyze a large sample of nearby AGNs with available measurements of molecular gas mass, radio luminosity, and [O iii] luminosity. Our results show that radio luminosity and [O iii] luminosity exhibit stronger correlations with molecular gas mass than with other physical parameters such as black hole mass, stellar mass, and bulge mass. Moreover, when controlling for the correlations between radio luminosity, [O iii] luminosity, and molecular gas mass, the relationships between these luminosities and other key physical parameters become significantly weaker or disappear entirely. This suggests that, of all the properties we have considered, it is the molecular gas mass that is most tightly correlated with radio and [O iii] luminosity, and may thus be the most important driver of nuclear activity.
{"title":"The Cold Molecular Gas Regulates the Activity of Active Galactic Nuclei in Massive Galaxies","authors":"Yongyun Chen, 永云 陈, Qiusheng Gu, 秋生 顾, Luis.C Ho, 子山 何, Junhui Fan, 军辉 樊, Feng Yuan, 峰 袁, Tao Wang, 涛 王, Zhifu Chen, 志福 陈, Dingrong Xiong, 定荣 熊, Xiaoling Yu, 效龄 俞, Xiaotong Guo, 晓通 郭, Nan Ding and 楠 丁","doi":"10.3847/1538-4357/ae4aa4","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4aa4","url":null,"abstract":"The physical quantities that directly regulate active galactic nucleus (AGN) feedback in massive galaxies remain poorly understood. Observations of molecular gas surrounding AGNs suggest that this gas serves as a fuel source for AGN activity. Accordingly, we study the relationship between AGN activity and molecular gas properties. In this study, we analyze a large sample of nearby AGNs with available measurements of molecular gas mass, radio luminosity, and [O iii] luminosity. Our results show that radio luminosity and [O iii] luminosity exhibit stronger correlations with molecular gas mass than with other physical parameters such as black hole mass, stellar mass, and bulge mass. Moreover, when controlling for the correlations between radio luminosity, [O iii] luminosity, and molecular gas mass, the relationships between these luminosities and other key physical parameters become significantly weaker or disappear entirely. This suggests that, of all the properties we have considered, it is the molecular gas mass that is most tightly correlated with radio and [O iii] luminosity, and may thus be the most important driver of nuclear activity.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"109 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519237","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：