The Astrophysical Journal Letters最新文献

{"title":"Zeeman Doppler Imaging of τ Ceti: The Weakest Magnetic Field Detected in a Sun-like Star","authors":"Federica Chiti, Oleg Kochukhov, Jennifer L. van Saders and Travis S. Metcalfe","doi":"10.3847/2041-8213/ae018a","DOIUrl":"https://doi.org/10.3847/2041-8213/ae018a","url":null,"abstract":"For nearly a decade, observations have shown that many older Sun-like stars spin faster than predicted, a phenomenon known as weakened magnetic braking (WMB). The leading hypothesis for WMB is a weakening of the large-scale dipole field, which leads to a less efficient angular momentum loss. To test this hypothesis on a star known to be in the WMB regime, we present the first Zeeman Doppler imaging (ZDI) map of the Sun-like star τ Ceti, reconstructed using spectropolarimetric data from the Canada–France–Hawai‘i Telescope. Our ZDI analysis reveals a remarkably simple, stable, and weak (〈B〉 = 0.17 G) magnetic field, characterized by a predominantly dipolar (∼92% magnetic energy contained in l = 1 modes), and highly axisymmetric (∼88% magnetic energy contained in m < l/2 modes) morphology. We infer a dipole field strength of Bdip = 0.31 G, nearly an order of magnitude weaker than standard braking model predictions, providing direct confirmation of the weakened large-scale dipole predicted by the WMB hypothesis. This work establishes a new benchmark for ZDI, demonstrating that even extremely quiet stars in the WMB regime are accessible to this technique.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059510","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":"On the Search for a Generation Mechanism for the Ion Acoustic Waves Observed by the Parker Solar Probe","authors":"Sergio E. Vidal-Luengo, David M. Malaspina and Stefan Eriksson","doi":"10.3847/2041-8213/adff88","DOIUrl":"https://doi.org/10.3847/2041-8213/adff88","url":null,"abstract":"The solar wind plasma is strongly accelerated near the Sun—this acceleration and heating remain beyond 1 au, which contradicts cooling by adiabatic expansion. Wave–particle interaction has been recognized as one of the key mechanisms for particle acceleration and heating in the solar wind. In this context, it is relevant to analyze the origin of the ion acoustic waves (IAWs) observed by the Parker Solar Probe (PSP) and their possible role in solar wind acceleration and heating. PSP has recorded various phenomena during its close encounters with the Sun, including IAWs, current sheets, ion velocity streams, and reconnection exhausts. The origin of the observed IAWs remains unknown. This study investigates the temporal correlation between IAWs, current sheets, ion speed streams, and reconnection exhausts as possible sources of ion beams. Our analysis reveals that current sheets and ion speed streams exhibit a statistically significant temporal proximity with IAWs and also between them, while reconnection exhausts did not show a statistical association with IAWs. These results suggest that current sheets may be associated with proton beams, which then excite IAWs.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"71 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145068146","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":"Neutron-quark Stars: Discerning Viable Alternatives for the Higher-density Part of the Equation of State of Compact Stars","authors":"Sudipta Hensh, Yong-Jia Huang, Toru Kojo, Luca Baiotti, Kentaro Takami, Shigehiro Nagataki and Hajime Sotani","doi":"10.3847/2041-8213/ae0031","DOIUrl":"https://doi.org/10.3847/2041-8213/ae0031","url":null,"abstract":"We investigate binary neutron star (BNS) mergers using general-relativistic numerical simulations with hadronic and hybrid equations of state (EOSs), incorporating the latest observations and theoretical constraints. We address two viable scenarios for the transition to quark matter: a quark-hadron crossover (QHC) or a strong first-order phase transition (1PT). To distinguish between different models, we define neutron-quark stars (NQSs) as configurations where quark effects emerge at masses below the lowest observed neutron-star mass. While traditional “hybrid stars” may be distinguished by purely hadronic configurations through mass–radius measurements, the mass–radius relations of NQSs resemble those of purely hadronic models, with no sharp boundary between hadrons and quarks. The name NQS effectively captures the absence of a phase boundary between hadrons and quarks in QHC scenarios. Our results indicate that QHC models can be distinguished from hadronic ones if both the inspiral and postmerger gravitational waves (GWs) are observed. In particular, the dominant postmerger frequency (f2) tends to be lower than in hadronic models with the same tidal deformability (Λ). We also present the first general-relativistic simulations of BNS mergers where the stars already contain quark matter before merging. These involve a strong 1PT at 1.8 times nuclear saturation density, followed by a stiff quark EOS. Finally, we identify a robust linear correlation between the total GW energy emitted after the merger and the f2 frequency. Remarkably, this relation holds regardless of the quark presence.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"76 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059247","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 Confirmed Deficit of Hot and Cold Dust Emission in the Most Luminous Little Red Dots","authors":"David J. Setton, Jenny E. Greene, Justin S. Spilker, Christina C. Williams, Ivo Labbé, Yilun Ma, 马逸伦, Bingjie Wang, 王冰洁, Katherine E. Whitaker, Joel Leja, Anna de Graaff, Stacey Alberts, Rachel Bezanson, Leindert A. Boogaard, Gabriel Brammer, Sam E. Cutler, Nikko J. Cleri, Olivia R. Cooper, Pratika Dayal, Seiji Fujimoto, Lukas J. Furtak, Andy D. Goulding, Michaela Hirschmann, Vasily Kokorev, Michael V. Maseda, Ian McConachie, Jorryt Matthee, Tim B. Miller, Rohan P. Naidu, Pascal A. Oesch, Richard Pan, Sedona H. Price, Katherine A. Suess, John R. Weaver, Mengyuan Xiao, Yunchong Zhang and Adi Zitrin","doi":"10.3847/2041-8213/ade78b","DOIUrl":"https://doi.org/10.3847/2041-8213/ade78b","url":null,"abstract":"Luminous broad Hα emission and red rest-optical spectral energy distributions (SEDs) are the hallmark of compact little red dots (LRDs), implying highly attenuated dusty starbursts and/or obscured active galactic nuclei (AGN). However, the lack of observed far-infrared (FIR) emission has proved difficult to reconcile with the implied attenuated luminosity in these models. Here, we utilize deep new Atacama Large Millimeter/submillimeter Array imaging, new and existing JWST/MIRI imaging, and archival Spitzer/Herschel imaging of two of the rest-optically brightest LRDs (z = 3.1 and z = 4.47) to place the strongest constraints on the IR luminosity in LRDs to date. The detections at λrest = 1–4 μm imply flat slopes in the rest-IR, ruling out a contribution from hot (T ≳ 500 K) dust. Similarly, FIR nondetections rule out any appreciable cold (T ≲ 75 K) dust component. Assuming energy balance, these observations are inconsistent with the typical FIR dust emission of dusty starbursts and quasar tori, which usually show a mixture of cold and hot dust. Additionally, our [C ii] nondetections rule out typical dusty starbursts. We compute empirical maximum IR SEDs and find that both LRDs must have at the 3σ level. These limits are in tension with the predictions of rest-optical spectrophotometric fits, be they galaxy-only, AGN-only, or composite. It is unlikely that LRDs are highly dust-reddened intrinsically blue sources with a dust temperature distribution that conspires to avoid current observing facilities. Rather, we favor an intrinsically redder LRD SED model that alleviates the need for strong dust attenuation.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145035511","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 Radially Resolved Magnetic Field Threading the Disk of TW Hya","authors":"Richard Teague, Boy Lankhaar, Sean M. Andrews, Chunhua Qi, Roger R. Fu, David J. Wilner, John B. Biersteker and Joan R. Najita","doi":"10.3847/2041-8213/adff4d","DOIUrl":"https://doi.org/10.3847/2041-8213/adff4d","url":null,"abstract":"We present a new approach to detecting and characterizing a magnetic field in protoplanetary disks through the differential broadening of unpolarized molecular emission from CN. To demonstrate this technique, we apply it to new Atacama Large Millimeter/submillimeter Array observations of the full complement of hyperfine components from the N = 1–0 transition, achieving a spatial and spectral resolution of and 80 m s−1, respectively. By fitting a model that incorporates the velocity structure of the disk, the potential non-LTE excitation of the molecule, and the Zeeman effect, we recover a radially resolved magnetic field with a strength of ∼10 mG between 60 and 120 au. The morphology of the field is also inferred through azimuthal variations in the line broadening, revealing a predominantly poloidal field at 60 au, sharply transitioning to one within the disk plane outside of the gap at 82 au. The signal-to-noise ratio of the data meant that the planar component was unable to be decomposed into toroidal and radial components. Lower limits on the local gas density (n(H2) ≳ 108 cm−3) from the excitation analysis of the CN emission correspond to a lower limit between 0.1 and 0.01 for the plasma β.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145043399","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":"Three-dimensional Dynamics of Strongly Magnetized Ion–Electron Relativistic Reconnection","authors":"Fabio Bacchini, Gregory R. Werner, Camille Granier and Jesse Vos","doi":"10.3847/2041-8213/ae0197","DOIUrl":"https://doi.org/10.3847/2041-8213/ae0197","url":null,"abstract":"We present 3D simulations of semirelativistic collisionless magnetic reconnection, where upstream ions are subrelativistic while electrons are ultrarelativistic. We employ the realistic proton-to-electron mass ratio and explore a range of upstream ion magnetizations spanning 2 orders of magnitude, with our highest-magnetization run achieving unprecedentedly large domain sizes. Through a parameter scan, we find that as the system transitions from mildly to trans- and ultrarelativistic regimes, the qualitative behavior of reconnection becomes strongly influenced by 3D effects mediated by drift-kink and flux-rope kink dynamics. As a result, magnetic-energy dissipation at high magnetizations, and the subsequent nonthermal particle acceleration, can become less efficient, contrary to general expectations for 3D relativistic reconnection. Our results have important implications for understanding reconnection in magnetized astrophysical scenarios, such as the surroundings of black holes and neutron stars.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145035513","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":"Imaging and Radio Signatures of Shock–Plasmoid Interaction","authors":"Pankaj Kumar, Judith T. Karpen, P. K. Manoharan and N. Gopalswamy","doi":"10.3847/2041-8213/ae0009","DOIUrl":"https://doi.org/10.3847/2041-8213/ae0009","url":null,"abstract":"Understanding how shocks interact with coronal structures is crucial for understanding the mechanisms of particle acceleration in the solar corona and inner heliosphere. Using simultaneous radio and white-light observations, we investigate the interaction between a coronal mass ejection (CME)-driven shock and a plasmoid. LASCO and STEREO-A COR-2 white-light images are analyzed to track the evolution of the plasmoid, CME, and its associated shock, while the Wind/WAVES and STEREO/WAVES dynamic spectra provide complementary radio signatures of the shock–plasmoid interaction at ≈7 R⊙. An interplanetary type II radio burst was detected as the shock propagated through the plasmoid. The merging of the plasmoid into the CME was accompanied by interplanetary type III radio bursts, suggesting escaping electron beams during the reconnection process. These observations clearly demonstrate that shock–plasmoid interactions can enhance the efficiency of particle acceleration associated with CMEs, with implications for electron acceleration in flare and heliospheric current sheets as well.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145031850","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 Detection of Teraelectronvolt Radiation from a Flat-spectrum Radio Quasar","authors":"Vaidehi S. Paliya, M. Böttcher, Kiran Wani, P. N. Naseef Mohammed, C. S. Stalin, S. Sahayanathan, D. J. Saikia and S. Muneer","doi":"10.3847/2041-8213/ae018d","DOIUrl":"https://doi.org/10.3847/2041-8213/ae018d","url":null,"abstract":"The very high-energy (VHE; >100 GeV) radiation carries the signatures of the matter–energy interaction in some of the most extreme astrophysical environments. Considering broad emission line blazars, i.e., flat-spectrum radio quasars (FSRQs), the dense photon fields surrounding the relativistic jet can prohibit the particle population from accelerating to very high energies and producing VHE radiation. They can also possibly make the environment opaque for the VHE γ rays due to γγ pair production, thus explaining the paucity of VHE-detected FSRQs and nondetection of TeV radiation (>1 TeV) from them. Here we report, for the first time, a >7σ detection of an FSRQ, S5 1027+74 (z = 0.123), in the VHE band, including the first ever detection of TeV emission from an object of this class, using the Fermi Large Area Telescope observations. Its γ-ray spectrum covering the 100 MeV–2 TeV band revealed a prominent spectral break with a flat, rising shape above ∼10 GeV, a feature never detected from other VHE-detected FSRQs. The radio-to-γ-ray spectral energy distribution of S5 1027+74 provides strong evidence of a third bump peaking at multi-TeV energies. These enigmatic findings imply that FSRQ jets can accelerate particles to extremely high energies and provide tantalizing clues about the complex radiative environment of relativistic jets.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145031851","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":"Jet Collimation in a Spiral-hosted Active Galactic Nucleus: A Parabolic Jet Profile in 0313–192","authors":"Seung Yeon Lee and Jae-Young Kim","doi":"10.3847/2041-8213/adf72b","DOIUrl":"https://doi.org/10.3847/2041-8213/adf72b","url":null,"abstract":"Double-lobed active galactic nuclei (DRAGNs) are typically found in elliptical galaxies, while supermassive black holes (SMBHs) in disk galaxies rarely produce powerful kiloparsec-scale jets. However, the growing number of spiral- and disk-hosted DRAGNs challenges this classical dichotomy. We present a study of the jet collimation profile for one such source, 0313–192, using Very Long Base Line Array and Very Large Array data, tracing the jet morphology across nearly 5 orders of magnitude in scale—from ∼a few pc to ∼100 kpc (projected). We find that the jet exhibits a parabolic expansion up to ∼610 pc (∼7.9 × 106 Schwarzschild radii), followed by a transition to a nearly conical shape, assuming kiloparsec-scale emission primarily originates from the jet rather than the lobe. This structural evolution closely resembles those in active galactic nuclei (AGNs) hosted by elliptical galaxies and provides an explanation for how the jet in this system could extend to large distances by magnetohydrodynamic collimation and acceleration. However, this collimation break occurs beyond the sphere of gravitational influence of the SMBH (∼7.3 × 105RS), and no extended X-ray halos or dense molecular gas structures are detected to provide the necessary external pressure. Therefore, we suggest that jet confinement in 0313–192 is mediated by contributions from nonthermal components, such as ram and magnetic pressure from magnetized disk winds. These mechanisms may enable jet collimation even in the absence of dense ambient gas. Our results highlight how large-scale jets can arise in disk galaxies under rare conditions and demonstrate the need to broaden studies of AGN jet formation beyond traditional models.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145035515","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":"Precovery Observations of 3I/ATLAS from TESS Suggest Possible Distant Activity","authors":"Adina D. Feinstein, John W. Noonan and Darryl Z. Seligman","doi":"10.3847/2041-8213/adfd4d","DOIUrl":"https://doi.org/10.3847/2041-8213/adfd4d","url":null,"abstract":"3I/ATLAS is the third macroscopic interstellar object detected traversing the solar system. Since its initial discovery on UT 2025 July 1, hundreds of hours on a range of observational facilities have been dedicated to measuring the physical properties of this object. These observations have provided astrometry to refine the orbital solution, photometry to measure the color, a rotation period and secular light curve, and spectroscopy to characterize the composition of the coma. Here, we report precovery photometry of 3I/ATLAS as observed with NASA’s Transiting Exoplanet Survey Satellite (TESS). 3I/ATLAS was observed nearly continuously by TESS from UT 2025 May 7 to 2025 June 2. We use the shift-stack method to create deepstack images to recover the object. These composite images reveal that 3I/ATLAS has an average TESS magnitude of Tmag = 20.83 ± 0.05, 19.28 ± 0.05 and an absolute visual magnitude of HV = 13.72 ± 0.35;12.52 ± 0.35, the latter being consistent with magnitudes reported in 2025 July. When coupled with recent Hubble Space Telescope images deriving a nucleus size of R < 2.8 km (H > 15.4), our measurements suggest that 3I/ATLAS may have been active out at ∼6 au. Additionally, we extract a ∼20 day light curve and find no statistically significant evidence of a nucleus rotation period. Nevertheless, the data presented here are some of the earliest precovery images of 3I/ATLAS and may be used in conjunction with future observations to constrain the properties of our third interstellar interloper.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"86 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145035516","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}