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A characteristic optical variability time scale in jetted active galactic nuclei: a large gamma-ray emission sample

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arXiv 2025年

作者： Xiong, Dingrong Sun, Mouyuan Wang, Jun-Xian Fan, Junhui Xue, Yongquan Gu, Minfeng Chen, Liang Chen, Yongyun Ding, Nan Guo, Fei Mao, Jirong Ren, Guowei Xue, Rui Yan, Dahai Yang, Shenbang Zhang, Haiyun Bai, Jinming Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Department of Astronomy Xiamen University Fujian Xiamen361005 China Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Science University of Science and Technology of China Hefei230026 China Center for Astrophysics Guangzhou University Guangzhou510006 China Astronomy Science and Technology Research Laboratory Department of Education of Guangdong Province Guangzhou510006 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China College of Physics and Electronic Engineering Qujing Normal University Qujing655011 China School of Physical Science and Technology Kunming University 650214 China Yunnan Normal University Kunming650500 China Department of Physics Zhejiang Normal University Jinhua321004 China Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Faculty of Science Kunming University of Science and Technology Kunming650500 China

The variability mechanisms from jetted AGNs are still under debate. Here the damped random walk (DRW) model, implemented through Gaussian Processe (GPs), is used to fit the ZTF long-term optical light curves of 1684 γ-ray emission jetted AGNs. This analysis yields one of the largest samples with characteristic optical variability timescales for jetted AGNs. A single DRW model from GPs can fit the optical light curve of most jetted AGNs well/potentially well, while there are still some jetted AGNs whose light curve can not be fitted well by a single DRW model. After the jet power, proxied by gamma-ray luminosity, is introduced as a new parameter, new relationships among intrinsic variability time scales, black hole mass and jet power are discovered for efficient accretion AGNs (formula presented) with scatter of approximately 0.09 dex) and for inefficient accretion AGNs (formula presented) with scatter of approximately 0.14 dex), respectively. Our results support that the optical variability of jetted AGNs with efficient accretion may originate within the standard accretion disk at UV emitting radii similar to non-jetted AGNs, and is directly related to the acceleration of shock in the jet and then enhanced through the beaming effect in beamed AGNs. For the jetted AGNs with inefficient accretion, the intrinsic timescale is consistent with the escape timescale of electrons. © 2025, CC BY.

关键词： Active Galactic Nuclei

Minute-Cadence Observations of the LAMOST Fields with the TMTS: V. Machine Learning Classification of TMTS Catalogues of Periodic Variable Stars

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arXiv 2024年

作者： Guo, Fangzhou Lin, Jie Wang, Xiaofeng Chen, Xiaodian Li, Tanda Chen, Liyang Xia, Qiqi Mo, Jun Xi, Gaobo Zhang, Jicheng Liu, Qichun Jiang, Xiaojun Yan, Shengyu Peng, Haowei Liu, Jialian Li, Wenxiong Lin, Weili Xiang, Danfeng Ma, Xiaoran Cai, Yongzhi Tsinghua University Haidian District Beijing100084 China CAS Key laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China Beijing Planetarium Beijing Academy of Sciences and Technology Beijing100044 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China Department of Astronomy Beijing Normal University Beijing100875 China School of Physics and Astronomy The University of Birmingham B15 2TT United Kingdom National Astronomical Observatories of China Chinese Academy of Sciences Beijing100012 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

Periodic variables are always of great scientific interest in astrophysics. Thanks to the rapid advancement of modern large-scale time-domain surveys, the number of reported variable stars has experienced substantial growth for several decades, which significantly deepened our comprehension of stellar structure and binary evolution. The Tsinghua University–Ma Huateng Telescopes for Survey (TMTS) has started to monitor the LAMOST sky areas since 2020, with a cadence of 1 minute. During the period from 2020 to 2022, this survey has resulted in densely sampled light curves for ~30,000 variables of the maximum powers in the Lomb-Scargle periodogram above the 5σ threshold. In this paper, we classified 11,638 variable stars into 6 main types using XGBoost and Random Forest classifiers with accuracies of 98.83% and 98.73%, respectively. Among them, 5301 (45.55%) variables are newly discovered, primarily consisting of δ Scuti stars, demonstrating the capability of TMTS in searching for short-period variables. We cross-matched the catalogue with Gaia’s second Data Release (DR2) and LAMOST’s seventh Data Release (DR7) to obtain important physical parameters of the variables. We identified 5504 δ Scuti stars (including 4876 typical δ Scuti stars and 628 high-amplitude δ Scuti stars), 5899 eclipsing binaries (including EA-, EB- and EW-type) and 226 candidates of RS Canum Venaticorum. Leveraging the metal abundance data provided by LAMOST and the Galactic latitude, we discovered 8 candidates of SX Phe stars within the class of "δ Scuti stars". Moreover, with the help of Gaia color-magnitude diagram, we identified 9 ZZ ceti stars. Copyright © 2024, The Authors. All rights reserved.

关键词： Stars

Application of a screened Coulomb potential in fitting the DAV star HS 0507+0434B

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arXiv 2020年

作者： Chen, Y.H. Chen, Y.H. Chen, Y.H. Institute of Astrophysics Chuxiong Normal University Chuxiong675000 China School of Physics and Electronical Science Chuxiong Normal University Chuxiong675000 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650011 China

We use WDEC to evolve grids of DAV star models adopting the element diffusion scheme with pure and screened Coulomb potential effect. The core compositions are thermonuclear burning results which are derived from MESA. MESA yields composition profiles that the version of WDEC used in this work could not accommodate (most notably the presence of helium in the core of the model). According to the theory of rotational splitting, Fu et al. identified 6 triplets for a DAV star HS 0507+0434B based on 206h photometric data. The grids of DAV star models are used to fit the 6 reliable m = 0 modes. When adopting the screened Coulomb potential, we obtain a best fitting model of log(MHe/M∗) = -3.0, log(MH/M∗) = -6.1, Teff = 11790K, M∗ = 0.625M., logg = 8.066, and σRMS = 2.08s. Compared with adopting the pure Coulomb potential, the value of σRMS is improved by 34%. The study may provide a new method for the research of mode trapping properties. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

Binary evolution and double sequences of blue stragglers in globular clusters

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Proceedings of the International Astronomical Union 2019年第S343期14卷 427-428页

作者： Jiang D. Chen X. Li L. Han Z. Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Beijing 100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

Binary evolution can produce different blue-straggler binaries, for example, blue stragglers with a bright, red component, or with a faint, blue component. In globular clusters, these blue-straggler binaries are generally observed as a single star, because two components can not be distinguished. Therefore, these blue-straggler binaries can be located in different regions of the color-magnitude diagram of globular clusters, e.g. blue sequence and red sequence observed in M30. We suggest that binary evolution can contribute to the blue stragglers in both of the sequences. Some blue stragglers in the blue sequence may have a faint white dwarf companion, while the red sequence includes some binaries experiencing mass transfer. It should be noted that the red sequence may also have other binaries, for example, the binaries just finished the mass transfer, and the binaries including a blue straggler (the accretors) that have evolved away from the blue sequence. © International Astronomical Union 2019.

关键词： Binaries: General blue stragglers globular clusters stars: evolution

GABE: Galaxy Assembly with Binary evolution

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Research in Astronomy and Astrophysics 2019年第10期19卷 121-137页

作者： Zhen Jiang Jie Wang Liang Gao Feng-Hui Zhang Qi Guo Lan Wang Jun Pan Key Laboratory for Computational Astrophysics National Astronomical Observatories Chinese Academy of Sciences Beijing 100101 China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Institute of Computational Cosmology Department of PhysicsUniversity of DurhamSouth RoadDurham DH1 3LEUK Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011 China

We developed a new semi-analytic galaxy formation model: Galaxy Assembly with Binary evolution(GABE). For the first time, we introduce binary evolution into semi-analytic models of galaxy formation by using the Yunnan-Ⅱ stellar population synthesis model, which includes various binary interactions. When implementing our galaxy formation model onto the merger trees extracted from the Millennium simulation, it can reproduce a large body of observational results. We find that in the local universe, the model including binary evolution reduces the luminosity at optical and infrared wavelengths slightly, but it increases the luminosity at ultraviolet wavelengths significantly, especially in FUV band. The resulting luminosity function does not change very much over SDSS optical bands and infrared band, but the predicted colors are bluer, especially when the FUV band is under consideration. The new model allows us to explore the physics of various high energy events related to the remnants of binary stars, such as type Ia supernovae, short gamma-ray bursts and gravitational wave events, and their relation with host galaxies in a cosmological context.

关键词： galaxies formation一galaxies luminosity function, mass function-galaxies stellar content

Velocity-resolved Reverberation Mapping of Changing-look Active Galactic Nucleus NGC 4151 During Outburst Stage: Evidence for Kinematics evolution of Broad-line Region

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arXiv 2022年

作者： Li, Sha-Sha Feng, Hai-Cheng Liu, H.T. Bai, J.M. Li, Rui Lu, Kai-Xing Wang, Jian-Guo Huang, Ying-Ke Zhang, Zhi-Xiang Yunnan Observatories Chinese Academy of Sciences Yunnan Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Yunnan Kunming650011 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Qian Xuesen Laboratory of Space Technology China Academy of Space Technology 104 Youyi Road Haidian District Beijing100094 China Multi-disciplinary Research Division Institute of High Energy Physics Chinese Academy of Sciences 19B Yuquan Road Beijing100049 China Department of Astronomy Xiamen University Fujian Xiamen361005 China

Changing-look active galactic nucleus NGC 4151, which has attracted a lot of attention, is undergoing the second dramatic outburst stage in its evolutionary history. To investigate the geometry and kinematics of the broad-line region (BLR), and measure the mass of supermassive black hole in NGC 4151, we perform a seven-month photometric and spectroscopic monitoring program in 2020–2021, using the 2.4 m telescope at Lijiang Observatory. We successfully measure the time lags of the responses from broad Hα, Hβ, Hγ, He I, and He II emission lines to continuum variation, which are 7.63+1.85−2.62, 6.21+1.41−1.13, 5.67+1.65−1.94, 1.59+0.86−1.11, and 0.46+1.22−1.06 days, respectively, following radial stratification. The ratios of time lags among these lines are 1.23: 1.00: 0.91: 0.26: 0.07. We find that the continuum lag between the ultraviolet and optical bands can significantly affect the lag measurements of He I and He II. Virial and infalling gas motions coexist in this campaign, which is different from previous results, implying the evolutionary kinematics of BLR. Based on our measurements and previous ones in the literature, we confirm that the BLR of NGC 4151 is basically virialized. Finally, we compute the black hole mass through multiple lines, and the measurement from Hβ to be 3.94+0.90−0.72 × 107Mo, which is consistent with previous results. The corresponding accretion rate is 0.02+0.01−0.01LEddc−2, implying a sub-Eddington accretor. © 2022, CC BY.

关键词： Active Galactic Nuclei

Detection of δ Scuti pulsators in the eclipsing binaries observed by TESS

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arXiv 2022年

作者： Chen, Xinghao Ding, Xu Cheng, Liantao Zhang, Xiaobin Li, Yan Ji, Kaifan Xiong, Jianping Li, Xuzhi Luo, Changqing Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China School of Opto-electronic Engineering Zaozhuang University Zaozhuang277160 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Deep Space Exploration Laboratory Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China

Based on 2-minute cadence TESS data from sectors 1-50, we report the results of the systematic extraction of δ Scuti-type pulsations in the 6431 eclipsing binaries with orbital periods shorter than 13 days. A total number of 242 pulsators were found in those systems, including 143 new discoveries. We examined their pulsation properties based on the H-R diagram and the relationships between the dominant pulsation period Pdom, orbital period Porb, and effective temperature Teff. As a consequence, 216 targets are likely δ Scuti stars (123 new), 11 likely γ Doradus-δ Scuti hybrid stars (8 new), 5 likely β Cephei stars (4 new), 4 likely δ Scuti-γ Doradus hybrid stars (3 new), 3 likely Maia stars (3 new), 2 likely pulsating red giants (1 new), and a new unclassified star. As for the 6 new δ Scuti pulsators in eclipsing binaries with Porb dom/Porb ratio. This may indicate that Pdom and Porb are uncorrelated for them. Finally, we statistically analyzed the dominant pulsation periods of the 216 δ Scuti stars in eclipsing binaries. Those stars concentrate around 225 µHz and the proportion of stars in the high-frequency region is significantly higher than that of single stars, which could be ascribed to the mass transfer process. Copyright © 2022, The Authors. All rights reserved.

关键词： Mass transfer

Mass transfer of low-mass binaries and chemical anomalies among unevolved stars in globular clusters

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arXiv 2020年

作者： Wei, Dandan Wang, Bo Chen, Xuefei Chen, Hailiang Li, Lifang Jiang, Dengkai Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

While it is well known that mass transfer in binaries can pollute the surfaces of the accretors, it is still unclear whether this mechanism can reproduce the observed chemical inhomogeneities in globular clusters. We study the surface abundances of the accretors in low-mass binaries, as a first step towards understanding whether mass transfer in low-mass binaries is one of the potential origins of the aforementioned abundance anomalies in globular clusters. We use the Modules for Experiments in Stellar Astrophysics code to calculate binary evolutionary models with different initial donor masses between 0.9 and 1.9 M for an initial metallicity of Z = 0.0034. The results show that in some low-mass binary systems, the accretors exhibit peculiar chemical patterns when they are still unevolved stars, e.g. C and O depletion;Na and N enhancement;constant Mg, Al and C+N+O. The abundance patterns of the accretors are significantly different from their initial abundances (or that of normal single stars), and can match the observed populations. These abundance patterns strongly depend not only on the initial parameters of binaries (donor mass, mass ratio, and orbital period), but also on the assumptions regarding mass-transfer efficiency and angular momentum loss. These results support the hypothesis that mass transfer in low-mass binaries is at least partly responsible for the unevolved anomalous stars in globular clusters. More work on binary evolutionary models and binary population synthesis is required to fully evaluate the contribution of this scenario. Copyright © 2020, The Authors. All rights reserved.

关键词： Mass transfer

OO Dra: An Algol-type binary formed through an extremely helium-poor mass accretion revealed by asteroseismology

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arXiv 2021年

作者： Chen, Xinghao Zhang, Xiaobin Li, Yan Luo, Changqing Li, Xuzhi Su, Jie Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

Based on the two-minutes TESS data, we analyzed intrinsic oscillations of the primary component and identified seven confident independent δ Scuti frequencies (f1, f2, f3, f4, f7, f11, and f12). Both of single-star evolutionary models and mass-accreting models are computed to reproduce the δ Scuti freqiencies. Fitting results of them match well with each other. The stellar parameters of the primary star yielded by asteroseismology are (Equation presented), which match well with the dynamic ones by the binary model. Furthermore, our asteroseismic results show that OO Dra is another Algol system that has just undergone the rapid mass-transfer stage. Fitting results of single-star evlutionary models indicate that the pulsator is helium-poor star with an age of 8.22+0.12−1.33 Myr, and the further mass-accreting models show that the primary star looks like an almost unevolved star formed by an extremely helium-poor mass accretion in Case A evolutionary scenario. Copyright © 2021, The Authors. All rights reserved.

关键词： Helium