The Astrophysical Journal Letters最新文献

{"title":"Hydrogen Loss on Venus Driven by Photochemistry","authors":"Hao Gu, Jun Cui, Xiaoshu Wu, Xu Huang, Shiqi Wu, Wenlong Li, Jinjin Zhao, Haoyu Lu and Lei Li","doi":"10.3847/2041-8213/adec90","DOIUrl":"https://doi.org/10.3847/2041-8213/adec90","url":null,"abstract":"Venus has experienced substantial H loss through hydrodynamic outflow in its early history, transforming from a warm and wet state to the current arid and scorching state. While Venus continues to lose H today, no consensus has been reached regarding the present dominant escape mechanisms. Recently, photochemical escape via HCO+ dissociative recombination (DR) has been proposed as a prevailing process that had previously been overlooked. However, due to uncertainties in the underlying H2 abundance and the solar cycle variations of the input radiative energy, it is essential to explore how these factors influence the modeled H escape flux under different conditions. By combining a photochemical model with a Monte Carlo test particle model, we demonstrate that the H escape flux increases with the underlying H2 concentration over a possible range of 1 × 106–2 × 108 cm−2 s−1, but varies nonmonotonically with solar activity due to the competition between photochemical production and collisional hindrance. While our results confirm the dominant role of HCO+ DR, we find that the ion-neutral reaction makes an additional contribution, which could reach more than 30% of total H escape. Our findings provide valuable insights into the foundational understanding of photochemically driven H escape because the same mechanism should function in a much broader context.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144652428","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 Universality of the Split Monopole Black Hole Magnetosphere","authors":"S. Selvi, O. Porth, B. Ripperda and L. Sironi","doi":"10.3847/2041-8213/adeb6c","DOIUrl":"https://doi.org/10.3847/2041-8213/adeb6c","url":null,"abstract":"Black holes (BHs) can acquire magnetic flux from their progenitor, through merger with a magnetized star, or via prolonged accretion. We study the evolution of BH magnetospheres using axisymmetric general relativistic magnetohydrodynamic simulations. We show that all initial magnetic field configurations, regardless of complexity, ultimately evolve into a split monopole. The magnetospheric evolution proceeds in two phases. In the first phase, pressure equilibrates on fast Alfvénic timescales (∼60 gravitational light-crossing times), and the flux on the BH event horizon drops sharply. The second phase proceeds in pressure balance, in which the magnetic flux decays via magnetic reconnection in current sheets, governing the dynamics on slower resistive timescales. We present an analytic model for the second phase, quantitatively describing the evolution of flux and current sheet dynamics. Additionally, we show that in the split monopole configuration, magnetic flux decays exponentially, with higher BH spin leading to slower decay. Our results enable a quantitative prediction of the timescales and spatial structure of these evolving magnetospheres, essential for understanding electromagnetic counterparts to gravitational wave events and reconnection-powered flares from accreting BHs.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144652332","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":"Langmuir-wave Excitation in Solar Wind Magnetic Holes","authors":"Jingting Liu, 婧婷 刘, Daniel Verscharen, Jesse Coburn, Georgios Nicolaou, Xiangyu Wu, 翔宇 吴, Wence Jiang, 文策 蒋, Oreste Pezzi, Francesco Pucci, Matteo Zuin, Christopher J. Owen and Hamish Reid","doi":"10.3847/2041-8213/adea4f","DOIUrl":"https://doi.org/10.3847/2041-8213/adea4f","url":null,"abstract":"Magnetic holes (MHs) are structures commonly observed in various space plasma environments throughout the solar system, including the solar wind. These structures are characterized by a localized decrease in magnetic field strength, coincident with an increase in plasma density. Previous observational studies in the solar wind link the presence of Langmuir waves to MHs, suggesting a strong correlation between these phenomena. We develop a model based on magnetic-moment conservation and its violation to explain the excitation of Langmuir waves in MHs. Our model illustrates that MHs induce changes in the electron velocity distribution function that emit electrostatic Langmuir waves due to the bump-on-tail instability. Using data from the Solar Orbiter spacecraft, we provide a comprehensive analysis of this process and test our predictions with observations. The consistency between our model and observations indicates that the proposed process is a viable mechanism for producing Langmuir waves in MHs in the solar wind.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144652330","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":"EP 250108a/SN 2025kg: Observations of the Most Nearby Broad-line Type Ic Supernova Following an Einstein Probe Fast X-Ray Transient","authors":"Jillian C. Rastinejad, Andrew J. Levan, Peter G. Jonker, Charles D. Kilpatrick, Christopher L. Fryer, Nikhil Sarin, Benjamin P. Gompertz, Chang Liu, Rob A. J. Eyles-Ferris, Wen-fai Fong, Eric Burns, James H. Gillanders, Ilya Mandel, Daniele Bjørn Malesani, Paul T. O’Brien, Nial R. Tanvir, Kendall Ackley, Amar Aryan, Franz E. Bauer, Steven Bloemen, Thomas de Boer, Clécio R. Bom, Jennifer A. Chacón, Ken Chambers, Ting-Wan Chen, Ashley A. Chrimes, Joyce N. D. van Dalen, Valerio D’Elia, Massimiliano De Pasquale, Michael D. Fulton, Paul J. Groot, Rahul Gupta, Dieter H. Hartmann, Agnes P. C. van Hoof, Mark E. Huber, Luca Izzo, Wynn Jacobson-Galan, Páll Jakobsson, Albert Kong, Tanmoy Laskar, Thomas B. Lowe, Eugene A. Magnier, Elisabetta Maiorano, Antonio Martin-Carrillo, Lluis Mas-Ribas, Daniel Mata Sánchez, Matt Nicholl, Christopher J. Nixon, Samantha R. Oates, Gregory Paek, Jesse Palmerio, Diego Paris, Daniëlle L. A. Pieterse, Giovanna Pugliese, Jonathan A. Quirola Vasquez, Jan va..","doi":"10.3847/2041-8213/ade7f9","DOIUrl":"https://doi.org/10.3847/2041-8213/ade7f9","url":null,"abstract":"With a small sample of fast X-ray transients (FXTs) with multiwavelength counterparts discovered to date, their progenitors and connections to γ-ray bursts (GRBs) and supernovae (SNe) remain ambiguous. Here, we present photometric and spectroscopic observations of SN 2025kg, the SN counterpart to the FXT EP 250108a. At z = 0.17641, this is the closest known SN discovered following an Einstein Probe (EP) FXT. We show that SN 2025kg’s optical spectra reveal the hallmark features of a broad-lined Type Ic SN. Its light-curve evolution and expansion velocities are comparable to those of GRB-SNe, including SN 1998bw, and two past FXT-SNe. We present JWST/NIRSpec spectroscopy taken around SN 2025kg’s maximum light, and find weak absorption due to He I 1.0830 μm and 2.0581 μm and a broad, unidentified emission feature at ∼4–4.5 μm. Further, we observe broadened Hα in optical data at 42.5 days that is not detected at other epochs, indicating interaction with H-rich material. From its light curve, we derive a 56Ni mass of 0.2–0.6 M⊙. Together with our companion Letter, our broadband data are consistent with a trapped or low-energy (≲1051 erg) jet-driven explosion from a collapsar with a zero-age main-sequence mass of 15–30 M⊙. Finally, we show that the sample of EP FXT-SNe supports past estimates that low-luminosity jets seen through FXTs are more common than successful (GRB) jets, and that similar FXT-like signatures are likely present in at least a few percent of the brightest Type Ic-BL SNe.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"247 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144645520","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":"Stellar Distributions around Supermassive Black Holes in Gas-rich Nuclear Star Clusters","authors":"Mor Rozner and Enrico Ramirez-Ruiz","doi":"10.3847/2041-8213/adeca7","DOIUrl":"https://doi.org/10.3847/2041-8213/adeca7","url":null,"abstract":"We study the stellar distribution around supermassive black holes in gas-rich nuclear star clusters (NSCs). NSCs could contain vast amounts of gas, which contribute significantly to shaping the stellar distribution, typically altering the stellar density cusp from the usual J. N. Bahcall & R. A. Wolf solution and consequently affecting the dynamics in the NSC. The dense gaseous environment in NSCs gives rise to dynamical phenomena that are otherwise rare in other gas-free environments. Here we extend the derivation introduced in J. N. Bahcall & R. A. Wolf to include an additional energy dissipation term associated with gas drag. We examine the effects of different forms of gas drag on the stellar density distribution. Finally, we discuss implications on the rates of tidal disruption events and other transients triggered by stellar interactions in gas-rich galactic nuclei.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144645533","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":"Nonstandard Collapse of Strong Langmuir Turbulence: Constraints on Its Occurrence and Observation in the Solar Corona","authors":"Yaokun Li, Haomin Sun, Hao Ning, Sulan Ni, Xiangliang Kong, Jiansen He and Yao Chen","doi":"10.3847/2041-8213/ade9bb","DOIUrl":"https://doi.org/10.3847/2041-8213/ade9bb","url":null,"abstract":"We present fully kinetic simulations of strong Langmuir turbulence (SLT) excited by electron beams with solar coronal conditions. We study two different collapsing processes within the parameter regimes of classical modulational instability (MI) and electron MI (EMI). For the first time, we simulated the EMI-induced collapse of moving multiple packets that is referred to as the non-Zakharov (or nonstandard) process here. We also simulated the classical Zakharov collapse of SLT induced by MI. During the early stage of the nonstandard collapse, the propagating packets get localized to form density cavities with depths of less than 0.1 n0 (the background electron density) that are too shallow to trap the packets. As a result, a majority of the packet energy runs away, undergoes a secondary collapse, and generates stationary packets with cavities. During the damping stage, the packets accelerate the background electrons to form numerous bidirectional propagating jets that distribute asymmetrically. This study reveals novel features of SLT collapse under coronal conditions.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"96 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144645535","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":"Measuring Emission Lines with JWST MegaScience Medium Bands: A New Window into Dust and Star Formation at Cosmic Noon","authors":"Brian Lorenz, Katherine A. Suess, Mariska Kriek, Sedona H. Price, Joel Leja, Erica Nelson, Hakim Atek, Rachel Bezanson, Gabriel Brammer, Sam E. Cutler, Pratika Dayal, Anna de Graaff, Jenny E. Greene, Lukas J. Furtak, Ivo Labbé, Danilo Marchesini, Michael V. Maseda, Tim B. Miller, Abby Mintz, Ikki Mitsuhashi, Richard Pan, Natalia Porraz Barrera, Bingjie Wang, 冰洁 王, John R. Weaver, Christina C. Williams and Katherine E. Whitaker","doi":"10.3847/2041-8213/ade887","DOIUrl":"https://doi.org/10.3847/2041-8213/ade887","url":null,"abstract":"We demonstrate the power of JWST-NIRCam medium-band photometry to measure emission line fluxes and study the dust and star formation properties of galaxies at cosmic noon. In this work, we present photometric emission line measurements and spatially resolved maps of Hα and Paβ for 14 galaxies at 1.3 ≤ z ≤ 2.4, observed by the MegaScience medium-band survey and the UNCOVER spectroscopic survey. We measure line fluxes directly from medium-band photometry and compare with spectroscopic measurements from UNCOVER. We find reasonable agreement between the photometric and spectroscopic emission line fluxes for both Hα and Paβ, with scatter <0.15 dex down to emission line equivalent widths of 10 Å. We also make a nebular dust measurement from the ratio Paβ/Hα, finding an average nebular attenuation in the V band, AV, of 1.4 with a standard deviation of 0.8. Our photometric AV measurements show a slightly larger scatter of 0.5 mag when compared to spectroscopic measurements; however, this scatter may be partially caused by aperture effects. Finally, we produce spatially resolved maps of Hα emission, Paβ emission, and the stellar continuum. We find offsets between Hα and Paβ emission, especially for galaxies with high AV, indicating dusty substructures. Furthermore, the correlation between Hα and continuum emission decreases with increasing AV, suggesting that the dustiest objects have clumpy dust and star formation distributions. Our study demonstrates the power of medium-band photometry to directly probe emission line strengths, star formation, and dust attenuation for hundreds of galaxies in UNCOVER and thousands of galaxies in upcoming JWST medium-band surveys.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"676 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144645525","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":"Little Red Dots as the Very First Activity of Black Hole Growth","authors":"Kohei Inayoshi","doi":"10.3847/2041-8213/adea66","DOIUrl":"https://doi.org/10.3847/2041-8213/adea66","url":null,"abstract":"The James Webb Space Telescope has detected massive black holes (BHs) with masses of ∼106−8M⊙ within the first billion years of the Universe. One of the remarkable findings is the identification of “little red dots” (LRDs), a unique class of active galactic nuclei (AGNs) with distinct characteristics representing a key phase in the formation and growth of early BHs. Here, we analyze the occurrence rate of LRDs, which emerge around redshifts z ∼ 6–8 and sharply decline at z < 4. We find that this trend follows a log-normal distribution, commonly observed in phenomena driven by stochastic and random factors. We propose a hypothesis that the first one or two AGN events associated with newly formed seed BHs are observed as LRDs, and their unique features fade in the subsequent episodes. This naturally explains the cosmic evolution of AGN abundance over 0 < z < 5, which follows ∝(1 + z)−5/2 due to the cumulative effect of recurring AGN activity. The unique characteristics of LRDs are likely linked to the dense gas environments around the seed BHs, which create strong absorption features in the broad-line emission and enable super-Eddington accretion bursts, ultimately yielding the observed overmassive nature of BHs compared to the local relationship. An analytical expression for the redshift evolution of LRD abundance is provided for direct comparison with future observational constraints.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"676 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144645536","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":"Explaining Ultramassive Quiescent Galaxies at 3 < z < 5 in the Context of Their Environments","authors":"Christian Kragh Jespersen, Adam C. Carnall and Christopher C. Lovell","doi":"10.3847/2041-8213/adeb7c","DOIUrl":"https://doi.org/10.3847/2041-8213/adeb7c","url":null,"abstract":"The swift assembly of the earliest galaxies poses a significant challenge to our understanding of galaxy formation. Ultramassive quiescent galaxies at intermediate redshifts (3 < z < 5) currently present one of the most pressing problems for theoretical modeling, since very few mechanisms can be invoked to explain how such galaxies formed so early in the history of the Universe. Here, we exploit the fact that these galaxies all reside within significant overdensities to explain their masses. To this end, we construct a modified version of the Extreme Value Statistics (EVS) code, which takes into account galaxy environment by incorporating clustering in the calculation. With this new version of EVS, we find that ultramassive quiescent galaxies at 3 < z < 5 do not present as serious a tension with simple models of galaxy formation when the analysis of a given galaxy is conditioned on its environment.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144645531","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 Kangaroo’s First Hop: The Early Fast Cooling Phase of EP250108a/SN 2025kg","authors":"Rob A. J. Eyles-Ferris, Peter G. Jonker, Andrew J. Levan, Daniele Bjørn Malesani, Nikhil Sarin, Christopher L. Fryer, Jillian C. Rastinejad, Eric Burns, Nial R. Tanvir, Paul T. O’Brien, Wen-fai Fong, Ilya Mandel, Benjamin P. Gompertz, Charles D. Kilpatrick, Steven Bloemen, Joe S. Bright, Francesco Carotenuto, Gregory Corcoran, Laura Cotter, Paul J. Groot, Luca Izzo, Tanmoy Laskar, Antonio Martin-Carrillo, Jesse Palmerio, Maria E. Ravasio, Jan van Roestel, Andrea Saccardi, Rhaana L. C. Starling, Aishwarya Linesh Thakur, Susanna D. Vergani, Paul M. Vreeswijk, Franz E. Bauer, Sergio Campana, Jennifer A. Chacón, Ashley A. Chrimes, Stefano Covino, Joyce N. D. van Dalen, Valerio D’Elia, Massimiliano De Pasquale, Nusrin Habeeb, Dieter H. Hartmann, Agnes P. C. van Hoof, Páll Jakobsson, Yashaswi Julakanti, Giorgos Leloudas, Daniel Mata Sánchez, Christopher J. Nixon, Daniëlle L. A. Pieterse, Giovanna Pugliese, Jonathan Quirola-Vásquez, Ben C. Rayson, Ruben Salvaterra, Ben Schneider, Ma..","doi":"10.3847/2041-8213/ade1d9","DOIUrl":"https://doi.org/10.3847/2041-8213/ade1d9","url":null,"abstract":"Fast X-ray transients are a rare and poorly understood population of events. Previously difficult to detect in real time, the launch of the Einstein Probe with its Wide-field X-ray Telescope has led to a rapid expansionof the sample and allowed the exploration of these transients across the electromagnetic spectrum. EP250108a is a recently detected example linked to an optical counterpart, SN 2025kg, or “the kangaroo.” Together with a companion Letter we present our observing campaign and analysis of this event. In this letter, we focus on the early evolution of the optical counterpart over the first 6 days, including our measurement of the redshift of z = 0.17641. We compare to other supernovae and fast transients showing similar features, finding significant similarities with SN 2006aj and SN 2020bvc, and show that the source is well modelled by a rapidly expanding cooling blackbody. We show the observed X-ray and radio properties are consistent with a collapsar-powered jet that is low energy (≲1051 erg) and/or fails to break out of the dense material surrounding it. While we examine the possibility that the optical emission emerges from the shock produced as the supernova ejecta expand into a dense shell of circumstellar material, due to our X-ray and radio inferences, we favour a model where it arises from a shocked cocoon resulting from a trapped jet. This makes SN 2025 one of the few examples of this currently observationally rare event.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144645469","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}