The Astrophysical Journal最新文献

{"title":"Quantifying the Effects of Parameters in Widespread Solar Energetic Particle Events with EPREM","authors":"Matthew A. Young and Bala Poduval","doi":"10.3847/1538-4357/ae5818","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5818","url":null,"abstract":"The Energetic Particle Radiation Environment Model (EPREM) solves the focused transport equation on a Lagrangian grid in a frame comoving with the solar wind plasma and simulates the acceleration and transport of solar energetic particles (SEPs) in the heliosphere. When not coupled to an external magnetohydrodynamic model, EPREM functions in an uncoupled mode, in which an ideal cone shock is injected into a homogeneous background solar wind. We carried out an analysis of the effects of multiple physical parameters on the generation of widespread SEP events using uncoupled EPREM, employing a relatively simple model of a strong, magnetized shock propagating radially outward through the inner heliosphere to produce the magnetohydrodynamic quantities required for EPREM’s sophisticated treatment of proton acceleration and transport. We compared a baseline simulation with seven variations in which a single parameter differed from its baseline value. All simulations exhibit complex SEP flux profiles as a function of time and energy, with clear dependence on parameters related to diffusion, mean free path, and shock profile. Moreover, while all simulations exhibit significant longitudinal spread in SEP flux, certain parameter values produce a decrease, or even absence, of SEP flux at observers located ≥90° from the shock origin. Relating differences in SEP flux to specific parameter values in the simulations provides insight into the morphology of observed SEP events and the state of the solar wind through which the driving coronal mass ejection propagates.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755057","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":"Mapping Jet-gas Coupling and Energetic Ionized Outflows in High-redshift Radio Galaxies with JWST/NIRSpec","authors":"Namrata Roy, Timothy Heckman, Alaina Henry, Wuji Wang and Pranav Kukreti","doi":"10.3847/1538-4357/ae5b68","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5b68","url":null,"abstract":"We present spatially resolved maps of morphology, kinematics, and energetics of warm ionized gas in six powerful radio galaxies at z ∼ 3.5-4, using JWST/NIRSpec integral field unit to quantify jet-driven feedback in the early Universe. All sources exhibit broad [O III] emission-line profiles with W80 (line width) values of 950–2500 km s−1 across approximately tens of kiloparsecs, signifying large-scale outflows. The outflowing nebulae are preferentially aligned with the radio jet axis, suggesting a jet-driven origin. On average, the regions with the broadest lines and highest velocities are co-spatial with radio lobes or cores, and exhibit the strongest kinetic power. Ionized gas masses associated with the outflows span from ∼1 to 8 × 109M⊙, with total mass outflow rates of 80–950 M⊙ yr−1 and kinetic powers between 1043.2 and 1045.0 erg s−1. The outflow kinetic power corresponds to 0.15%–2% of the AGN bolometric luminosity, sufficient to impact galaxy evolution. However, only ≲1% of the jet's mechanical energy couples to the warm ionized gas via outflows, consistent with predictions from hydrodynamic simulations. A large fraction of the jet energy may instead reside in shock-heated hot gas, supported by X-ray detection, or used to thermalize the gas and produce the observed emission-line nebulae. Our results demonstrate that radio jets in massive, gas-rich systems at high redshift can inject significant kinetic and thermal energy into the surroundings, providing direct evidence for jet-driven feedback operating during the peak epoch of galaxy formation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755066","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":"Resolved UV–Optical HST Imaging and Spectral Energy Distribution Modeling of Nearby BAT Active Galactic Nuclei","authors":"Connor Auge, Michael Koss, Kriti K. Gupta, Claudio Ricci, Benny Trakhtenbrot, Franz E. Bauer, Ezequiel Treister, Alessandro Peca, Brad Cenko, Kohei Ichikawa, Arghajit Jana, Darshan Kakkad, Richard Mushotzky, Kyuseok Oh, Alejandra Rojas Lilayú, David Sanders, Roberto Serafinelli, Matilde Signorini, Alessia Tortosa and C. Megan Urry","doi":"10.3847/1538-4357/ae581d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae581d","url":null,"abstract":"We use high-resolution UV-to-optical imaging from the Hubble Space Telescope (HST) to construct spatially resolved spectral energy distributions (SEDs) for seven nearby (z < 0.07) hard (14–195 keV) X-ray-selected broad-line active galactic nuclei (AGN) with Lbol = 1043.26–1045.34 erg s−1. The high spatial resolution of HST, which physically resolves structures on the scale of ∼50 pc at z = 0.05, enables the separation of AGN and host-galaxy emission through morphological decomposition with GALFIT, yielding improved measurements of AGN properties compared to those obtained with lower-resolution Swift UV/Optical Telescope (UVOT) data. AGN UV magnitudes derived from HST imaging (e.g., F225W) can differ by more than a magnitude from those from Swift/UVOT UVM2 due to extended nuclear emission. Additionally, the inclusion of high-resolution data at longer wavelengths (e.g., F814W) can significantly affect the resulting SED fit. Comparing fits of accretion disk and extinction models using HST and Swift/UVOT data, we find significant differences in the resulting parameters, with average differences of 2.0 eV in the maximum disk temperature and 2.2 mag in the AGN host-galaxy extinction. These differences ultimately lead to significant changes in bolometric luminosities and X-ray bolometric corrections, with the HST-based fits yielding average increases of ∼0.57 dex and ∼0.66 dex, respectively. This demonstrates host-galaxy contamination in unresolved UV–optical data can strongly bias SED-based estimates of disk temperatures, extinction, bolometric luminosities, and X-ray bolometric corrections in AGN. Large-area, high-resolution imaging surveys from Euclid and the Nancy Grace Roman Space Telescope will extend these techniques to much larger AGN samples, enabling uniform, high-precision SED measurements in the near-IR.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755060","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":"A Theoretical Investigation of He i Line Profiles for the Spectroscopic Analysis of DB White Dwarfs","authors":"Patrick Tremblay, Pierre Bergeron and Alain Beauchamp","doi":"10.3847/1538-4357/ae5e72","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5e72","url":null,"abstract":"We present a comprehensive investigation of He i line profile calculations used in the spectroscopic analyses of DB white dwarfs. Our study includes an in-depth photometric and spectroscopic analysis of all DB white dwarfs in Data Release 17 of the Sloan Digital Sky Survey, examining the effects of frequency sampling, Doppler broadening, line dissolution, broadening by neutral particles, and 3D hydrodynamical corrections on our results. More importantly, we compare the outcomes obtained from the semianalytical He i Stark profiles commonly used in DB white dwarf spectroscopic analyses with our recent calculations of Stark-broadened profiles derived from computer simulations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"71 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755068","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":"A Novel Parameterization for Rapid Cooling in Supernova Remnants, with Applications to the Pa 30 Nebula","authors":"Miranda Pikus, Paul Duffell, Soham Mandal and Abigail Polin","doi":"10.3847/1538-4357/ae57ac","DOIUrl":"https://doi.org/10.3847/1538-4357/ae57ac","url":null,"abstract":"We systematically study how cooling creates structural changes in supernova remnants as they evolve. Inspired by the peculiar morphology of the Pa 30 nebula, we adopt a framework in which to characterize supernova remnants under different degrees of cooling. Our cooling framework characterizes remnants with a singular parameter called β that sets how rapidly the system’s thermal energy is radiated or emitted away. A continuum of morphologies is created by the implementation of different cooling timescales. For β ≳ 400, or when the cooling timescale is shorter than of the Sedov time, the ejecta are shaped into a filamentary structure similar to Pa 30. We explain the filament creation by the formation of Rayleigh–Taylor instability fingers where cooling has prevented the Kelvin–Helmholtz instability from overturning and mixing out the tips. The ejecta in these filaments have not decelerated and are moving almost completely ballistically at ≈95%–100% their free expansion speed. In this rapid cooling regime, an explosion energy of ≈3.5 × 1047 erg is inferred. We also propose that the cooling mechanism required to create these structures necessitates removing energy at a rate of 2% of Eej/t, which implies a cooling luminosity of ≈1036 erg s−1.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755058","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":"Strongly Subisothermal Polytropic Behavior of Ions in the Martian Magnetosheath Revealed by MAVEN Observations","authors":"Han-Wen Shen, Jasper S. Halekas, Shaosui Xu, Jih-Hong Shue, Yuanzheng Wen, Chi Zhang, Shannon M. Curry, David A. Brain, David L. Mitchell and Jared R. Espley","doi":"10.3847/1538-4357/ae5a91","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5a91","url":null,"abstract":"Energy redistribution during plasma compression or expansion remains poorly understood, particularly within induced magnetospheric systems. The polytropic index serves as an important diagnostic of this process by characterizing the thermodynamic response of temperature and pressure to density variations. This study presents the first statistical determination of the ion polytropic index in the Martian magnetosheath, leveraging 9 yr of Mars Atmosphere and Volatile EvolutioN (MAVEN) observations. Derived indices largely fall within the subisothermal range, yielding a median value of 0.42. Such polytropic behavior signifies systematic ion cooling during local compression—a thermodynamic response that departs significantly from both the adiabatic condition and the near-isothermal trends typically observed in Earth’s magnetosheath. Beyond this characteristic, a well-defined spatial trend is also identified, with the index increasing radially from the bow shock toward the induced magnetosphere boundary. The polytropic index displays a clear anticorrelation with the amplitude of low-frequency magnetic field fluctuations, indicating a close association between wave activity and ion thermodynamics in the Martian magnetosheath. In summary, this study provides a pioneering quantitative characterization of ion polytropic behavior at Mars, offering a critical benchmark for comparative analyses between induced and intrinsic magnetospheric environments.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755181","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":"Pervasive Cavity-rim Structure for Star Formation in Dwarf Irregular Galaxies","authors":"Bruce G. Elmegreen and Deidre A. Hunter","doi":"10.3847/1538-4357/ae5a1f","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5a1f","url":null,"abstract":"Unsharp-mask images of H I emission from 36 dwarf irregular (dIrr) galaxies illustrate star formation in dispersed clouds and on the rims of large cavities. The cavities can extend for a radial scale length and typically have circular or slightly sheared forms. The average surface density of cloud peaks is ∼20 M⊙ pc−2, and, combined with their average far-UV star formation rate, this suggests a gas consumption time of ∼3.2 Gyr. Vertical hydrostatic equilibrium calculations for 24 of these dIrrs give a typical scale height of ∼400 pc, which combines with the gas and star formation surface densities to suggest an efficiency per freefall time of ∼1%. These values are comparable to those in the molecular clouds of spiral galaxies, suggesting that the primary difference between clouds is the presence of CO at higher metallicity in the spirals. U − B color images of the dIrrs suggest that cavity ages range between 107 and 108 yr, with the longer times explaining the common lack of bright OB associations in their centers and their low expansion speeds. Most are circular because the shear time exceeds 100 Myr, although some of the H I has spiral structure. These observations suggest that star formation in dIrrs proceeds slowly in a sequential fashion in dispersed clouds and on the periphery of giant cavities that move and expand during the ∼50 Myr supernova era of the previous generation. In contrast, spiral galaxies have shear times 10× shorter and more important stellar dynamics that compresses the gas into filaments.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755061","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":"X-Ray Pulsar Period Dynamic Estimation: A Model Based on the Interlayer Phase Difference of the Fast Folding Algorithm","authors":"Tianhao Xie, Peiling Cui, Xiaolin Ning and Xin Ma","doi":"10.3847/1538-4357/ae5dc0","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5dc0","url":null,"abstract":"To further improve the accuracy and speed of real-time dynamic estimation of X-ray pulsar periods, this paper proposes a pulsar period estimation model based on the interlayer phase difference (IPD) of the fast folding algorithm (FFA) and the weighted Z2 (WZ) test. This paper adopts a staged estimation strategy and divides the pulsar period estimation into a fast initial estimation stage and a local refinement search stage. First, in the fast initial estimation stage, an FFA IPD model based on the relationship among phase, time, and period is established. The interlayer phase is used to directly perform a single initial estimation of a large range of periods, thereby improving the period estimation speed. Second, in the local refinement search stage, the response coverage index is proposed for the Z2 test function. The WZ test function is constructed to perform a refinement test on the local candidate period to improve the period estimation accuracy. Meanwhile, for the PSR B0531+21 source, we conducted ablation tests, analyzed influencing factors and simulation performance of the proposed method, and validated its practical application performance using Neutron Star Interior Composition Explorer observation data. We also performed generalization performance tests on other sources such as PSR B0540-69 and SMC X-1. The results show that our method has significant advantages compared to several existing estimation methods. Specifically, for the PSR B0531+21 source, compared to the integrated χ2 test method, our method improves estimation accuracy by 50.21% and reduces computational time by 73.47%.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755064","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":"Hiding out at the Low End: No Gap and a Peak in the Black-hole Mass Spectrum","authors":"Anarya Ray, Will M. Farr and Vassiliki Kalogera","doi":"10.3847/1538-4357/ae581e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae581e","url":null,"abstract":"In recent years, the existence of a gap in the mass spectrum of compact objects formed from stellar collapse, between the heaviest neutron stars and the lightest black holes, has been a matter of significant debate. The presence or absence of a mass gap has implications for the supernova mechanism, as well as being a fundamental property of the compact object mass function. In X-ray binaries containing black holes, a gap is observed, but it is not known whether this is representative of a true gap in the mass function or due to selection effects or systematic biases in mass estimation. Binary black hole mergers detected from gravitational waves in the GWTC-3 transient catalog furnish a large sample of several tens of low-mass black holes with a well-understood selection function. Here, we analyze the 25 GWTC-3 merger events (along with GW230529_181500) with at least one black hole (3 M⊙ < m1) and chirp masses below those of a 20–20 M⊙ merger ( ) to uncover the structure of the low-mass black hole mass function. Using flexible parameterized models for the mass function, we find, similar to existing studies, a sharp peak in the mass function at m ≃ (8–10M⊙). We observe a steady decline in the merger rate to lower masses but by less than an order of magnitude in total and find that the first percentile of black hole masses in our most flexible model is . In other words, this sample of low-mass black holes is not consistent with the existence of a mass gap.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755062","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":"The Coldest Known Y Dwarfs: Estimates of Their Effective Temperatures","authors":"S. K. Leggett","doi":"10.3847/1538-4357/ae5814","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5814","url":null,"abstract":"For a decade there has been a factor of 2.5 gap in luminosity between the 275 K WISE J085510.83-071442.5 and all other Y dwarfs, with Teff ≳ 350 K. Recently, three objects were found that may fall in this gap. Two are companions to Y dwarfs: WISE J033605.05-014350.4B and CWISEP J193518.58-154620.3B; the third is MEAD 62B, a candidate companion to a white dwarf. Evolutionary models calculate a tight relationship between luminosity and Teff for Y dwarfs. I determine luminosities and hence Teff for three Y dwarfs (WISE J085510.83-071442.5, WISE J173835.53+273259.0, WISE J182831.08+265037.7). I derive relationships between Teff and mid-infrared colors using these together with 22 T and Y dwarfs from S. A. Beiler et al. with luminosity-based Teff values. These relationships are used to explore the Teff distribution for Y dwarfs. A sample of 31 Y dwarfs within ∼20 pc is presented with 275 < Teff K < 425. The JWST colors for WISE J053516.80-750024.9 and WISE J182831.08+265037.7 support previous suggestions that they are unresolved binaries, the former a 480 and 340 K dwarf pair and the latter a pair of 387 K dwarfs. Five other dwarfs have unusual colors; two are likely high-gravity and/or metal-poor (WISE J024714.52+372523.5, WISEA J215949.54-480855.2), two are low-gravity and/or metal-rich (CWISEP J104756.81+545741.6, WISE J150115.92-400418.4), and the fifth cannot be interpreted (WISE J043052.92+463331.6). An Appendix provides colors that can be used as a reference for searches for brown dwarfs in JWST data.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"249 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147755059","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}