The Astrophysical Journal Letters最新文献

{"title":"Intermingled Open and Closed Magnetic Field Lines near the Radial Origin of the Heliospheric Current Sheet","authors":"F. S. Mozer, A. Voshchepynets, O. V. Agapitov, K.-E. Choi, L. Colomban and R. Sydora","doi":"10.3847/2041-8213/adee08","DOIUrl":"https://doi.org/10.3847/2041-8213/adee08","url":null,"abstract":"On 2024 March 30, the Parker Solar Probe crossed the heliospheric current sheet at 13 solar radii while encountering two distinctly different regions at sharp boundaries on several occasions. The two regions had very different plasma densities, electric-field spectra, and magnetic-field geometries. In one region the strahl flowed only along the direction from the Sun, and there were relatively few particles at pitch angles near 90°, while in the other region the strahl flowed both toward and away from the Sun, and there were relatively many particles at pitch angles near 90°. These different properties are interpreted as being due to the spacecraft being in the heliospheric current sheet on long open magnetic field lines in the case of unidirectional strahl flow and the spacecraft being in coronal loops having much shorter closed magnetic field lines in the case with bidirectional strahl flow. The two regions intermingled on time scales less than 100 ms to create a complex magnetic field geometry. Broadband waves were observed in the open field-line regions, while narrowband electrostatic harmonic waves were observed in both regions. These harmonic frequencies correlated with the proton plasma frequency, fpp, with the lowest frequency at ∼0.1fpp. This result, plus the field-aligned electric field waves and plasma density fluctuations, requires that the observed electrostatic mode and associated harmonics were ion acoustic waves.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701922","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":"JWST’s First View of Tidal Disruption Events: Compact, Accretion-driven Emission Lines and Strong Silicate Emission in an Infrared-selected Sample","authors":"Megan Masterson, Kishalay De, Christos Panagiotou, Erin Kara, Wenbin Lu, Anna-Christina Eilers, Muryel Guolo, Armin Rest, Claudio Ricci and Sjoert van Velzen","doi":"10.3847/2041-8213/ade153","DOIUrl":"https://doi.org/10.3847/2041-8213/ade153","url":null,"abstract":"Mid-infrared (MIR) emission from tidal disruption events (TDEs) is a powerful probe of the circumnuclear environment around dormant supermassive black holes. This emission arises from the reprocessing of intrinsic emission into thermal MIR emission by circumnuclear dust. While the majority of optical- and X-ray-selected TDEs show only weak dust echoes consistent with primarily unobscured sight lines, there have been growing efforts aimed at finding TDEs in obscured environments using MIR selection methods. In this work, we present the first JWST observations of four MIR-selected TDEs with the JWST Mid-Infrared Instrument (MIRI) Medium-Resolution Spectrometer (MRS). Two of these sources show flares in other wavelength bands (one in optical, one in X-ray), while the other two are MIR-only transients. None of these TDEs showed pre-outburst nuclear activity, but all of the MIRI/MRS observations reveal emission lines associated with highly ionized gas in the nucleus, implying ionization from TDE accretion. Additionally, all four sources show silicate emission features around 10 and 18 μm that are much stronger than the features seen in active galactic nuclei. We suggest that the emitting dust is optically thin to its own emission and show that the MIR spectrum is consistent with emission from optically thin dust in the nucleus. All four sources show an excess at short wavelengths (λ < 8 μm), which could arise from a late-time plateau in the intrinsic flare, akin to what is seen in late-time UV observations of unobscured TDEs, although self-consistent dust modeling is required to fully assess the strength of this late-time plateau.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144694058","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":"Near-horizon Polarization as a Diagnostic of Black Hole Spacetime","authors":"Yehui Hou, Jiewei Huang, Minyong Guo, Yosuke Mizuno and Bin Chen","doi":"10.3847/2041-8213/adee09","DOIUrl":"https://doi.org/10.3847/2041-8213/adee09","url":null,"abstract":"A key challenge in imaging supermassive black holes is disentangling gravitational effects from plasma physics in order to accurately determine spacetime properties, particularly black hole spin. In this Letter, we present a fully covariant and rigorous analysis of the synchrotron emission from accreting plasma in the equatorial plane in the stationary, axisymmetric, high-conductivity regime and identify—for the first time—a distinctive near-horizon polarization pattern that remains robust across different flow structures. This pattern arises from strong frame dragging near the event horizon, which induces a degeneracy among plasma flow and magnetic field configurations, yielding a polarization signature determined solely by the spacetime geometry and the observer’s inclination. The near-horizon polarization thus offers a clean and precise probe of black hole spin and other fundamental parameters. If future space-based millimeter very long baseline interferometry observations can resolve synchrotron emission originating within approximately 1% of the event horizon radius in M87* or Sgr A*, this universal polarization pattern may become observable.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"120 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701923","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 Probable Direct-imaging Detection of the Stellar Companion to Betelgeuse","authors":"Steve B. Howell, David R. Ciardi, Catherine A. Clark, Douglas A. Hope, Colin Littlefield and Elise Furlan","doi":"10.3847/2041-8213/adeaaf","DOIUrl":"https://doi.org/10.3847/2041-8213/adeaaf","url":null,"abstract":"Betelgeuse—the closest M-supergiant to the Sun—has recently been predicted to host a lower-mass stellar companion that orbits the primary with a period of ∼6 yr. The putative stellar companion is thought to cause the long photometric modulation observed in Betelgeuse, which cannot be explained by stellar pulsations. Additionally, radial velocity and astrometric data also point to a stellar companion. Here we present diffraction-limited optical speckle imaging observations obtained on the 8.1 m Gemini North telescope in 2020 and 2024. The 2020 observations were taken during the Great Dimming event and at a time when the stellar companion was predicted to be unobservable because it was directly in line with Betelgeuse itself. The 2024 observations were taken 3 days after the predicted time of greatest elongation for the companion. A comparison of the 2020 and 2024 data reveals no companion in 2020 (as expected) and the probable detection of a companion in 2024. The presumed stellar companion has an angular separation and position angle of 52 mas and 115° east of north, respectively, which is in excellent agreement with predictions from dynamical considerations. The detected companion is roughly 6 magnitudes fainter than Betelgeuse at 466 nm. While this is only a 1.5σ detection, five results are in reasonable agreement with the predictions: the appearance of the companion at quadrature; the angular separation from Betelgeuse; the position angle with respect to Betelgeuse; the magnitude difference; and the estimated mass of the companion.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144684791","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 Deep Search for Ethylene Glycol and Glycolonitrile in the V883 Ori Protoplanetary Disk","authors":"Abubakar M. A. Fadul, Kamber R. Schwarz, Tushar Suhasaria, Jenny K. Calahan, Jane Huang and Merel L. R. van ’t Hoff","doi":"10.3847/2041-8213/adec6e","DOIUrl":"https://doi.org/10.3847/2041-8213/adec6e","url":null,"abstract":"Ethylene glycol ( ; hereafter EG) and glycolonitrile ( ; hereafter GN) are considered molecular precursors of nucleic acids. EG is a sugar alcohol and the reduced form of glycolaldehyde (CH2(OH)CHO; hereafter GA). GN is considered a key precursor of adenine formation (nucleotide) and can be a precursor of glycine (amino acid). Detections of such prebiotic molecules in the interstellar medium are increasingly common. How much of this complexity endures to the planet formation stage, and thus is already present when planets form, remains largely unknown. Here we report Atacama Large Millimeter/submillimeter Array observations in which we tentatively detect EG and GN in the protoplanetary disk around the outbursting protostar V883 Ori. The observed EG emission is best reproduced by a column density of and a temperature of at least 300 K. The observed GN emission is best reproduced by a column density of and a temperature of K. Comparing the abundance of EG and GN relative to methanol in V883 Ori with other objects, V883 Ori falls between hot cores and comets in terms of increasing complexity. This suggests that the buildup of prebiotic molecules continues past the hot core phase into the epoch of planet formation. Nascent planets in such environments may inherit essential building blocks for life, enhancing their potential habitability. Further observations of this protoplanetary disk at higher spectral resolution are required to resolve blended lines and to confirm these tentative detections.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"75 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144693987","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":"GRB 221009A: Observations with LST-1 of CTAO and Implications for Structured Jets in Long Gamma-Ray Bursts","authors":"K. Abe, S. Abe, A. Abhishek, F. Acero, A. Aguasca-Cabot, I. Agudo, C. Alispach, D. Ambrosino, F. Ambrosino, L. A. Antonelli, C. Aramo, A. Arbet-Engels, C. Arcaro, T. T. H. Arnesen, K. Asano, P. Aubert, A. Baktash, M. Balbo, A. Bamba, A. Baquero Larriva, U. Barres de Almeida, J. A. Barrio, L. Barrios Jiménez, I. Batkovic, J. Baxter, J. Becerra González, E. Bernardini, J. Bernete, A. Berti, I. Bezshyiko, C. Bigongiari, E. Bissaldi, O. Blanch, G. Bonnoli, P. Bordas, G. Borkowski, G. Brunelli, A. Bulgarelli, M. Bunse, I. Burelli, L. Burmistrov, M. Cardillo, S. Caroff, A. Carosi, R. Carraro, M. S. Carrasco, F. Cassol, D. Cerasole, G. Ceribella, A. Cerviño Cortínez, Y. Chai, K. Cheng, A. Chiavassa, M. Chikawa, G. Chon, L. Chytka, G. M. Cicciari, A. Cifuentes, J. L. Contreras, J. Cortina, H. Costantini, M. Dalchenko, P. Da Vela, F. Dazzi, A. De Angelis, M. de Bony de Lavergne, R. Del Burgo, C. Delgado, J. Delgado Mengual, M. Dellaiera, D. della Volpe, B. De Lotto, L. Del Peral, R. d..","doi":"10.3847/2041-8213/ade4cf","DOIUrl":"https://doi.org/10.3847/2041-8213/ade4cf","url":null,"abstract":"GRB 221009A is the brightest gamma-ray burst (GRB) observed to date. Extensive observations of its afterglow emission across the electromagnetic spectrum were performed, providing the first strong evidence of a jet with a nontrivial angular structure in a long GRB. We carried out an extensive observation campaign in very-high-energy (VHE) gamma rays with the first Large-Sized Telescope of the future Cherenkov Telescope Array Observatory starting on 2022 October 10, about 1 day after the burst. A dedicated analysis of the GRB 221009A data is performed to account for the different moonlight conditions under which data were recorded. We find an excess of gamma-like events with a statistical significance of 4.1σ during the observations taken 1.33 days after the burst, followed by background-compatible results for the later days. The results are compared with various models of afterglows from structured jets that are consistent with the published multiwavelength data but entail significant quantitative and qualitative differences in the VHE emission after 1 day. We disfavor models that imply VHE flux at 1 day considerably above 10−11 erg cm−2 s−1. Our late-time VHE observations can help disentangle the degeneracy among the models and provide valuable new insight into the structure of GRB jets.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144684798","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":"Contemporaneous X-Ray and Optical Polarization of Extremely High-synchrotron-peaked Blazar H 1426+428","authors":"Anuvab Banerjee, Akash Garg, Divya Rawat, Svetlana Jorstad, Alan P. Marscher, Ivan Agudo, Jorge Otero-Santos, Daniel Morcuende, Juan Escudero Pedrosa, Alberto Domínguez, Ayan Bhattacharjee, Isaiah Cox, Indrani Pal, Xiurui Zhao, Andrealuna Pizzetti, Stefano Marchesi, Núria Torres-Albà, Kouser Imam, Ross Silver and Marco Ajello","doi":"10.3847/2041-8213/adeca8","DOIUrl":"https://doi.org/10.3847/2041-8213/adeca8","url":null,"abstract":"We present the first contemporaneous X-ray and optical polarimetric measurement of the extremely high-synchrotron-peaked (HSP) blazar H 1426+428. The X-ray polarimetric observations were undertaken using the Imaging X-ray Polarimetry Explorer (IXPE) on 2024 May 27 and 2024 July 5. The IXPE pointings were accompanied by contemporaneous optical observations of the Observatorio de Sierra Nevada, Calar Alto Observatory, and the Perkins Telescope Observatory. While we observed the X-ray degree of polarization to be >20%, the polarization in the optical band was found to be only 1%–3%. This trend has been observed in several HSP blazars with available optical and X-ray polarimetric data and is typically explained in terms of energy stratification downstream of a shock. However, we observed a significant difference between the optical and X-ray polarization angles, a feature that has been observed in certain HSP blazars, such as Mrk 421, but remains a relatively rare or underreported phenomenon. We discuss possible scenarios for these findings within the framework of a partially turbulent jet model.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144693990","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":"An Energy Perspective of Core Erosion in Gas Giant Planets","authors":"J. R. Fuentes, Christopher R. Mankovich and Ankan Sur","doi":"10.3847/2041-8213/adef0a","DOIUrl":"https://doi.org/10.3847/2041-8213/adef0a","url":null,"abstract":"Juno and Cassini have shown that Jupiter and Saturn likely contain extended gradients of heavy elements. Yet, how these gradients can survive over billions of years remains an open question. Classical convection theories predict rapid mixing and homogenization, which would erase such gradients on timescales far shorter than the planets’ ages. To address this, we estimate the energy required to erode both dense and fuzzy cores, and compare it to what the planet can realistically supply. If the entire cooling budget is available to drive mixing, then even a compact core can, in principle, be destroyed. But if mixing is limited to the thermal energy near the core, which is another plausible scenario, the energy falls short. In that case, Jupiter can erode a fuzzy core by up to approximately 10 M⊕, but a compact one remains intact. Saturn’s core is more robust. Even in the fuzzy case, only about 1 M⊕ is lost, and if the core is compact, erosion is negligible. The outcome depends sensitively on the assumed initial temperature and entropy profiles. Hotter and more superadiabatic interiors are more prone to mixing. We suggest that 3D simulations of convection driven from above, with realistic stratification and enough depth (i.e., many density scale heights) would be of great interest to further constrain the energy budget for core erosion.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"124 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144693988","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 Star–White Dwarf Merger as One Possible Optional Source of Kilonova-like Emission: Implications for GRB 211211A","authors":"Xiao-Xuan Liu, Hou-Jun Lü, Qiu-Hong Chen, Zhao-Wei Du and En-Wei Liang","doi":"10.3847/2041-8213/adec83","DOIUrl":"https://doi.org/10.3847/2041-8213/adec83","url":null,"abstract":"Long-duration GRB 211211A, which lacked an associated supernova at very a low redshift z = 0.076 but was associated with a possible kilonova emission, has attracted great attention. The neutron star–white dwarf (NS–WD) merger is proposed as a possible progenitor of GRB 211211A, and it could naturally explain the long duration of the prompt emission. However, the NS–WD merger is not an ideal site for producing heavy elements via r-process nucleosynthesis. In this Letter, we investigate the heavy elements produced in NS–WD mergers based on numerical simulations of nucleosynthesis via SkyNet and then calculate the resulting kilonova-like emission to compare with the solidly observed case of possible kilonova emission associated with GRB 211211A. By adopting three models (i.e., Model-A, Model-B, and Model-C) from M. A. R. Kaltenborn et al. at different temperatures (T = 4, 5, and 6 GK), which are treated as free parameters, we find that the mass number of the heaviest element produced in our simulations is less than 90 (A < 90). Moreover, by comparing the calculated kilonova-like emission with the afterglow-subtracted observations of the possible kilonova associated with GRB 211211A, it is found that the merger of an NS and WD cannot be ruled out as the origin of GRB 211211A to produce the possible kilonova emission if the remnant of the WD–NS merger is a supramassive or stable magnetar. Otherwise, it is difficult to explain the early possible kilonova emission following GRB 211211A by invoking the merger of a WD and an NS.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"108 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144684796","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 Intracluster Light Analysis of the Most Evolved Systems of Galaxies: Fossil Groups","authors":"Nícolas O. L. de Oliveira, Yolanda Jiménez-Teja, Renato A. Dupke, Eleazar R. Carrasco, Anton M. Koekemoer, Yuanyuan Su, Jose Manuel Vilchez, Jimmy A. Irwin, Eric D. Miller and Lucas E. Johnson","doi":"10.3847/2041-8213/aded0c","DOIUrl":"https://doi.org/10.3847/2041-8213/aded0c","url":null,"abstract":"We present the analysis of the intracluster light (ICL) in three fossil groups, RX J085640.72+055347.36, RX J1136+0713, and RX J1410+4145, at z ∼ 0.1. We used two optical broadband filters, F435W and F606W, observed with the Hubble Space Telescope, and spectroscopic data obtained with the Gemini Multi-Object Spectrograph to generate the ICL maps and measure the ICL fraction using CICLE, an algorithm developed to disentangle the ICL from the light of galaxies. We found ICL fractions of 9.9%–14.4%, 3.8%–6.1%, and 4.7%–10.7% for RXJ0856, RXJ1136, and RXJ1410, respectively. This behavior is not consistent with the presence of the ICL fraction excess previously observed in merging clusters, and is also inconsistent with the constant ICL fraction distribution characteristic of relaxed systems, although the values found are within the typical range expected for the latter. Instead, they show a significantly increasing trend with wavelengths over ∼3800–5500 Å, indicating that fossil groups are indeed old and undisturbed systems, even compared with regular relaxed clusters.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144684794","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}