The Astrophysical Journal最新文献_第9页

Magnetic Island Structures Associated with Kinetic Alfvén Solitary Wave in Two-fluid Plasma 双流体等离子体中与动力学alfv<s:1>孤波相关的磁岛结构

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/ae0716

Cheong R. Choi, M.-H. Woo, Peter H. Yoon, Kwangsun Ryu, H. K. Cho, Jungjoon Seough and D.-Y. Lee

{"title":"Magnetic Island Structures Associated with Kinetic Alfvén Solitary Wave in Two-fluid Plasma","authors":"Cheong R. Choi, M.-H. Woo, Peter H. Yoon, Kwangsun Ryu, H. K. Cho, Jungjoon Seough and D.-Y. Lee","doi":"10.3847/1538-4357/ae0716","DOIUrl":"https://doi.org/10.3847/1538-4357/ae0716","url":null,"abstract":"We investigate the formation of magnetic islands and the onset of tearing instability within kinetic Alfvén solitary waves in a two-fluid space plasma. These localized structures, featuring internal magnetic shear, naturally support magnetic reconnection processes analogous to tearing modes in magnetically confined fusion plasmas. Treating the solitary wave as a quasi-static background equilibrium, we analyze the resulting topological modifications by making use of the magnetic flux function, in analogy with tokamak plasmas. We find that the spatial size of the magnetic island scales with the square root of the magnetic flux perturbation. Introducing the tearing stability index , we derive the growth rate of the tearing mode using a resistive magnetohydrodynamic framework. Our analysis reveals that tearing modes grow only when the mode’s wavenumber exceeds the inhomogeneity scale, becoming marginally stable when the two are comparable. The emergence of magnetic islands has significant implications for cross-field particle transport, turbulence, and acceleration. In particular, the electron diffusion across magnetic fields may be governed by the island size rather than the Larmor radius, potentially accounting for anomalous transport. Furthermore, in certain regimes, unbounded island growth may signal the collapse of the solitary wave structure, enabling a large-scale transfer of magnetic energy to particle energy. These results suggest a unifying mechanism connecting magnetic reconnection in space plasmas with tearing instabilities in laboratory fusion plasmas.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"84 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246729","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}

引用次数: 0

Classifying Cool Dwarfs: Comprehensive Spectral Typing of Field and Peculiar Dwarfs Using Machine Learning 冷矮星分类：利用机器学习对场和特殊矮星进行综合光谱分型

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/adfb7d

Tianxing Zhou, Christopher A. Theissen, S. Jean Feeser, William M. J. Best, Adam J. Burgasser, Kelle L. Cruz, Lexu Zhao

{"title":"Classifying Cool Dwarfs: Comprehensive Spectral Typing of Field and Peculiar Dwarfs Using Machine Learning","authors":"Tianxing Zhou, Christopher A. Theissen, S. Jean Feeser, William M. J. Best, Adam J. Burgasser, Kelle L. Cruz, Lexu Zhao","doi":"10.3847/1538-4357/adfb7d","DOIUrl":"https://doi.org/10.3847/1538-4357/adfb7d","url":null,"abstract":"Low-mass stars and brown dwarfs—spectral types (SpTs) M0 and later—play a significant role in studying stellar and substellar processes and demographics, reaching down to planetary-mass objects. Currently, the classification of these sources remains heavily reliant on visual inspection of spectral features, equivalent width measurements, or narrow/wideband spectral indices. Recent advances in machine learning (ML) methods offer automated approaches for spectral typing, which are becoming increasingly important as large spectroscopic surveys such as Gaia, SDSS, and SPHEREx generate data sets containing millions of spectra. We investigate the application of ML in spectral type classification on low-resolution (<italic toggle=\"yes\">R</italic> ∼ 120) near-infrared spectra of M0–T9 dwarfs obtained with the SpeX instrument on the NASA Infrared Telescope Facility. We specifically aim to classify the gravity- and metallicity-dependent subclasses for late-type dwarfs. We used binned fluxes as input features and compared the efficacy of spectral type estimators built using Random Forest (RF), Support Vector Machine, and K-Nearest Neighbor (KNN) models. We tested the influence of different normalizations and analyzed the relative importance of different spectral regions for surface gravity and metallicity subclass classification. Our best-performing model (using KNN) classifies 95.5% ± 0.6% of sources to within ±1 SpT, and assigns surface gravity and metallicity subclasses with 89.5% ± 0.9% accuracy. We test the dependence of signal-to-noise ratio on classification accuracy and find sources with SNR ≳60 have ≳95% accuracy. We also find that <italic toggle=\"yes\">zy </italic>band plays the most prominent role in the RF model, with FeH and TiO having the highest feature importance.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145247173","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}

引用次数: 0

Irradiated Pulsar Planets and Companions as 511 keV Positron Annihilation Line Sources 辐射脉冲星行星及其伴星作为511kev正电子湮灭线源

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/ae031f

Zachary Metzler and Zorawar Wadiasingh

{"title":"Irradiated Pulsar Planets and Companions as 511 keV Positron Annihilation Line Sources","authors":"Zachary Metzler and Zorawar Wadiasingh","doi":"10.3847/1538-4357/ae031f","DOIUrl":"https://doi.org/10.3847/1538-4357/ae031f","url":null,"abstract":"Millisecond pulsars (MSPs) are prolific GeV γ-ray emitters, and nearly 80% of Fermi Large Area Telescope MSPs reside in compact binaries. For the first time in the literature, we demonstrate that the companions in these compact MSPs binaries are also 511 keV annihilation line emitters using MEGAlib simulations (a high-energy radiation transport software built with Geant4) to compute the particle showers and resulting backsplash emission from the pulsar irradiation. The 511 keV signal exhibits strong flux modulation and red- and blueshifts associated with a binary orbit, enabling powerful coherent searches. Measuring the 511 keV emission would enable direct γ-ray characterization of unusual pulsar exoplanets and companions, and allow one to identify the unambiguous presence of active pulsars whose beams do not intercept Earth. Intriguingly, the 511 keV flux is brightest for ultracompact systems, against which pulsar surveys are systematically biased. These ultracompact systems are also possibly prime Laser Interferometer Space Antenna (LISA) Galactic sources. This necessitates future joint LISA–MeV γ-ray techniques to characterize MSP binaries. These MSP binaries may also contribute to the puzzling source of the excess 511 keV photons near the Galactic bulge and center.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246686","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}

引用次数: 0

A Time-dependent Solution for GSN 069 Disk Evolution and the Nature of Long-lived Tidal Disruption Events GSN 069盘演化和长周期潮汐破坏事件性质的时间依赖解

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/ae039e

M. Guolo, A. Mummery, A. Ingram, M. Nicholl, S. Gezari and E. Nathan

{"title":"A Time-dependent Solution for GSN 069 Disk Evolution and the Nature of Long-lived Tidal Disruption Events","authors":"M. Guolo, A. Mummery, A. Ingram, M. Nicholl, S. Gezari and E. Nathan","doi":"10.3847/1538-4357/ae039e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae039e","url":null,"abstract":"We present the implementation of a fully time-dependent relativistic disk model—based on the light-curve fitting package FitTeD—into the X-ray spectral fitting environment, pyXspec. This implementation enables simultaneous fitting of multi-epoch and multiwavelength spectral data, where the only free parameters are those describing the black hole and the initial conditions, while the subsequent evolution is governed by the dynamical equations of an evolving accretion flow. We use it to fit seven epochs of X-ray spectra and two epochs of UV spectra of the “long-lived” tidal disruption event (TDE) and quasiperiodic eruption (QPE) source GSN 069, from 2010 through late-2019. Our results show that such “long-lived,” X-ray-bright TDEs—of which GSN 069 is a prime, but not unique, example—can naturally be explained within the same framework as events with shorter-lived X-ray emission, like ASASSN-14li and AT2019dsg. Their distinction lies in the “viscous” timescale parameter—tied to the disk’s angular momentum transport efficiency—which should be treated as a free parameter when modeling the disk evolution of transient events. We examine the implications for QPE models by tracking the time evolution of disk properties such as mass surface density and accretion rate. We argue that existing QPE models may not be able to reproduce the observed connection between the presence (2018) or absence (2014) of eruptions and the disk properties. In the context of orbiter–disk collision models, the change in mass surface density appears insufficient to explain the needed variation in the eruption’s temperature. The absence of eruptions in GSN 069 in 2014 remains a challenge for QPE models.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"84 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246688","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}

引用次数: 0

Radio Variability in Recently Quenched Galaxies: The Impact of Tidal Disruption Event or Active Galactic Nucleus-Driven Outflows 最近淬灭星系的无线电变异性：潮汐破坏事件或活跃星系核驱动外流的影响

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/adff7a

K. Decker French, Kristina Nyland, Pallavi Patil, Kishalay De, Dillon Dong, Nicholas Earl, Samaresh Mondal, Kate Rowlands, Margaret Shepherd and Margaret E. Verrico

{"title":"Radio Variability in Recently Quenched Galaxies: The Impact of Tidal Disruption Event or Active Galactic Nucleus-Driven Outflows","authors":"K. Decker French, Kristina Nyland, Pallavi Patil, Kishalay De, Dillon Dong, Nicholas Earl, Samaresh Mondal, Kate Rowlands, Margaret Shepherd and Margaret E. Verrico","doi":"10.3847/1538-4357/adff7a","DOIUrl":"https://doi.org/10.3847/1538-4357/adff7a","url":null,"abstract":"Outflows and jets launched from the nuclei of galaxies emit radio synchrotron emission that can be used to study the impact of accretion energy on the host galaxy. The decades-long baseline now enabled by large radio surveys allows us to identify cases where new outflows or jets have been launched. Here, we present the results of a targeted Very Large Array program observing four poststarburst galaxies that have brightened significantly in radio emission over the past ∼20 yr. We obtain quasi-simultaneous observations in five bands (1–18 GHz) for each source. We find peaked spectral energy distributions, indicative of self-absorbed synchrotron emission. While all four sources have risen significantly over the past ∼20 yr in the 1–2 GHz band, two also show clear recent flares in the 2–4 GHz band. These sources are less luminous than typical peaked-spectrum radio active galactic nucleus (AGN). It remains unclear whether these sources are low luminosity analogs of the peaked radio AGN from accreted gas, or driven by tidal disruption events with missed optical flares. Regardless of the source of the accreted material, these newly launched outflows contain sufficient energy to drive the molecular gas outflows observed in poststarburst galaxies and to drive turbulence, suppressing star formation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246725","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}

引用次数: 0

Prospects of Constraining Equilibrium Tides in Low-mass Binary Stars 低质量双星中约束平衡潮汐的前景

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/adf4cf

Jessica Birky, Rory Barnes and James R. A. Davenport

{"title":"Prospects of Constraining Equilibrium Tides in Low-mass Binary Stars","authors":"Jessica Birky, Rory Barnes and James R. A. Davenport","doi":"10.3847/1538-4357/adf4cf","DOIUrl":"https://doi.org/10.3847/1538-4357/adf4cf","url":null,"abstract":"The dynamical evolution of short-period low-mass binary stars (with mass M < 1.5M⊙, from formation to the late main sequence, and with orbital periods less than ∼10 days) is strongly influenced by tidal dissipation. This process drives orbital and rotational evolution that ultimately results in circularized orbits and rotational frequencies synchronized with the orbital frequency. Despite the fundamental role of tidal dissipation in binary evolution, constraining its magnitude (typically parameterized by the tidal quality factor ) has remained discrepant by orders of magnitude in the existing literature. Recent observational constraints from time-series photometry (e.g., Kepler, K2, TESS), as well as advances in theoretical models to incorporate a more realistic gravitational response within stellar interiors, are invigorating new optimism for resolving this long-standing problem. To investigate the prospects and limitations of constraining tidal , we use global sensitivity analysis and simulation-based inference to examine how the initial conditions and tidal influence the observable orbital and rotational states. Our results show that, even under the simplest and most tractable models of tides, the path toward inferring from individual systems is severely hampered by inherent degeneracies between tidal and the initial conditions, even when considering the strongest possible constraints (i.e., binaries with precise masses, ages, orbital periods, eccentricities, and rotation periods). Finally, as an alternative, we discuss how population synthesis approaches may be a more promising path forward for validating tidal theories.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246773","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}

引用次数: 0

High-sensitivity Molecular Line Observations toward the L1544 Prestellar Core Challenge Current Models * L1544星前核心的高灵敏度分子线观测挑战当前模型*

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/adff78

J. Ferrer Asensio, S. S. Jensen, S. Spezzano, P. Caselli, F. O. Alves, O. Sipilä and E. Redaelli

{"title":"High-sensitivity Molecular Line Observations toward the L1544 Prestellar Core Challenge Current Models *","authors":"J. Ferrer Asensio, S. S. Jensen, S. Spezzano, P. Caselli, F. O. Alves, O. Sipilä and E. Redaelli","doi":"10.3847/1538-4357/adff78","DOIUrl":"https://doi.org/10.3847/1538-4357/adff78","url":null,"abstract":"The increased sensitivity and spectral resolution of observed spectra toward the prestellar core L1544 are challenging the current physical and chemical models. With the aim of further constraining the structure of L1544 as well as assessing the completeness of chemical networks, we turn to radiative transfer modeling of observed molecular lines toward this source. We obtained high-sensitivity and high spectral resolution observations of HCO+ (J = 1–0), CS (J = 2–1), C34S (J = 2–1), H2CO (J = 21,2–11,1), c-C3H2 (J = 21,2–10,1), SO (N, J = 2, 3–1, 2), and 34SO (N, J = 2, 3–1, 2) with the IRAM 30 m telescope toward the dust peak of L1544. A non–local thermodynamic equilibrium radiative transfer code is coupled to the Markov Chain Monte Carlo method to model the observations. We find that with just one transition for each isotope, the modeling cannot find a global minimum that fits the observations. The derived fractional abundance profiles are compared to those computed with chemical models. The observed transitions trace gas components with distinct dynamics at different distances along the radius of the core. Moreover, the results evidence a poor reproduction of sulfur chemistry by chemical modeling and stress the need to include a more consistent S-depletion process to accurately reproduce the S-chemistry toward dense cores.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246678","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}

引用次数: 0

Selection of Dwarf Galaxies Hosting Active Galactic Nuclei: A Measure of Bias and Contamination Using Unsupervised Machine Learning Techniques 选择拥有活动星系核的矮星系：使用无监督机器学习技术测量偏差和污染

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/ae0326

Sogol Sanjaripour, Archana Aravindan, Gabriela Canalizo, Shoubaneh Hemmati, Bahram Mobasher, Alison L. Coil and Barry C. Barish

{"title":"Selection of Dwarf Galaxies Hosting Active Galactic Nuclei: A Measure of Bias and Contamination Using Unsupervised Machine Learning Techniques","authors":"Sogol Sanjaripour, Archana Aravindan, Gabriela Canalizo, Shoubaneh Hemmati, Bahram Mobasher, Alison L. Coil and Barry C. Barish","doi":"10.3847/1538-4357/ae0326","DOIUrl":"https://doi.org/10.3847/1538-4357/ae0326","url":null,"abstract":"Identifying active galactic nuclei (AGNs) in dwarf galaxies is critical for understanding black hole formation but remains observationally challenging due to their low luminosities, metallicities, and star formation–driven emission that can obscure AGN signatures. Machine learning techniques, particularly unsupervised methods, offer new ways to address these challenges by uncovering patterns in complex, multiwavelength data. In this study, we apply Self-Organizing Maps (SOMs) to explore the spectral energy distribution (SED) manifold of dwarf galaxies and evaluate AGN selection biases across various diagnostics. We train a 51 × 51 SOM on 30,344 dwarf galaxies (z < 0.055, M* < 109.5M⊙) from the NSA catalog using nine-band photometry spanning near-UV to mid-infrared. A set of 438 previously identified dwarf AGNs, selected via mid-infrared color, optical emission lines, X-ray, optical variability, and broad-line features, was mapped onto the SOM. AGNs identified by different methods occupy distinct and partially overlapping regions in SED space, reflecting biases related to host galaxy properties. Wide-field Infrared Survey Explorer (WISE)-selected AGNs are strongly concentrated in lower-mass regions and form two distinct clumps: one associated with bluer, starburst-like systems and the other with redder galaxies showing spectral features more typical of AGNs. This separation may help disentangle true AGN hosts from starburst contaminants in WISE-selected samples. Additionally, AGNs selected via various diagnostics tend to avoid regions of strong star formation, while a subset of lower-mass AGNs occupy SOM regions indicative of high AGN luminosity relative to their stellar content. Our results demonstrate the utility of manifold learning in refining AGN selection in the low-mass regime.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"106 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246687","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}

引用次数: 0

Identifying the Secondary Jet in the RadioAstron Image of OJ 287 在oj287射电天文学家图像中识别副喷流

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/ae057e

Mauri J. Valtonen, Lankeswar Dey, Staszek Zola, Alok C. Gupta, Shubham Kishore, Achamveedu Gopakumar, Paul J. Wiita, Minfeng Gu, Kari Nilsson, Zhongli Zhang, Rene Hudec, Katsura Matsumoto, Marek Drozdz, Waldemar Ogloza, Andrei V. Berdyugin, Daniel E. Reichart, Markus Mugrauer, Tapio Pursimo, Stefano Ciprini, Tatsuya Nakaoka, Makoto Uemura, Ryo Imazawa, Michal Zejmo, Vladimir V. Kouprianov, James W. Davidson, Alberto Sadun, Jan Štrobl, Martin Jelínek and Abhimanyu Susobhanan

{"title":"Identifying the Secondary Jet in the RadioAstron Image of OJ 287","authors":"Mauri J. Valtonen, Lankeswar Dey, Staszek Zola, Alok C. Gupta, Shubham Kishore, Achamveedu Gopakumar, Paul J. Wiita, Minfeng Gu, Kari Nilsson, Zhongli Zhang, Rene Hudec, Katsura Matsumoto, Marek Drozdz, Waldemar Ogloza, Andrei V. Berdyugin, Daniel E. Reichart, Markus Mugrauer, Tapio Pursimo, Stefano Ciprini, Tatsuya Nakaoka, Makoto Uemura, Ryo Imazawa, Michal Zejmo, Vladimir V. Kouprianov, James W. Davidson, Alberto Sadun, Jan Štrobl, Martin Jelínek and Abhimanyu Susobhanan","doi":"10.3847/1538-4357/ae057e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae057e","url":null,"abstract":"The 136 yr long optical light curve of OJ 287 is explained by a binary black hole model where the secondary is in a 12 yr orbit around the primary. Impacts of the secondary on the accretion disk of the primary generate a series of optical flares that follow a quasi-Keplerian relativistic mathematical model. The orientation of the binary in space is determined from the behavior of the primary jet. Here, we ask how the jet of the secondary black hole projects onto the sky plane. Assuming that the jet is initially perpendicular to the disk, and that it is ballistic, we follow its evolution after the Lorentz transformation to the observer’s frame. Since the orbital speed of the secondary is of the order of one-tenth of the speed of light, the result is a change in the jet direction by more than a radian during an orbital cycle. We match the theoretical jet line with the recent 12 μas resolution RadioAstron map of OJ 287 and determine the only free parameter of the problem, the apparent speed of the jet relative to speed of light. It turns out that the Doppler factor of the jet, δ ∼ 5, is much lower than in the primary jet. Besides following a unique shape of the jet path, the secondary jet is also distinguished by a different spectral shape than in the primary jet. The present result on the spectral shape agrees with the huge optical flare of 2021 November 12, also arising from the secondary jet.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246726","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}

引用次数: 0

Examining Active Galactic Nucleus UV/Optical Variability beyond the Simple Damped Random Walk. II. Insights from 22 yr Observations of SDSS, PS1, and ZTF 在简单阻尼随机漫步之外研究活动星系核紫外线/光学变异性。2。来自SDSS， PS1和ZTF 22年观测的见解

The Astrophysical Journal Pub Date : 2025-10-08 DOI: 10.3847/1538-4357/adfdd2

Weixiang Yu, 伟翔于, Gordon T. Richards, John J. Ruan, Michael S. Vogeley, Franz E. Bauer and Matthew J. Graham

{"title":"Examining Active Galactic Nucleus UV/Optical Variability beyond the Simple Damped Random Walk. II. Insights from 22 yr Observations of SDSS, PS1, and ZTF","authors":"Weixiang Yu, 伟翔于, Gordon T. Richards, John J. Ruan, Michael S. Vogeley, Franz E. Bauer and Matthew J. Graham","doi":"10.3847/1538-4357/adfdd2","DOIUrl":"https://doi.org/10.3847/1538-4357/adfdd2","url":null,"abstract":"A damped random walk (DRW) process is often used to describe the temporal UV/optical continuum variability of active galactic nuclei (AGN). However, recent investigations have shown that this model fails to capture the full spectrum of AGN variability. In this work, we model the 22 yr long light curves of 21,767 quasars, spanning the redshift range 0.28 < z < 2.71, as a noise-driven damped harmonic oscillator (DHO) process. The light curves, in the optical g and r bands, are collected and combined from the Sloan Digital Sky Survey, the Panoramic Survey Telescope and Rapid Response System, and the Zwicky Transient Facility. A DHO process can be defined using four parameters, two for describing its long-term behavior/variability, and the other two for describing its short-term behavior/variability. We find that the best-fit DHO model describes the observed variability of our quasar light curves better than the best-fit DRW model. Furthermore, the best-fit DHO parameters exhibit correlations with the rest-frame wavelength, the Eddington ratio, and the black hole mass of our quasars. Based on the power spectral density shape of the best-fit DHOs and these correlations, we suggest that the observed long-term variability of our quasars can be best explained by accretion rate or thermal fluctuations originating from the accretion disk, and the observed short-term variability can be best explained by reprocessing of X-ray variability originating from the corona. The additional information revealed by DHO modeling emphasizes the need to go beyond DRW when analyzing AGN light curves delivered by next-generation wide-field time-domain surveys.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145246819","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}

引用次数: 0