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arXiv 2025年

作者： Xiong, Jianping Cheng, Qiyuan Chen, Xiaodian Li, Jiao Zhang, Xiaobin Han, Zhanwen Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of the Chinese Academy of Sciences Beijing101408 China Department of Astronomy China West Normal University Nanchong China

Context. Surface brightness-color relations (SBCRs) are essential for estimating distances and stellar properties. Previously, SBCRs were based on a limited number of red clump giant (RC) stars, and red giant branch (RGB) stars with infrared interferometric measurements or eclipsing binaries with high-precision radii measurements, resulting in discrepancies in precision and accuracy. Recently, the large number of RGB stars with asteroseismic parameters and precise Gaia distance measurements has enabled the development of more accurate and robust SBCRs. Aims. Asteroseismic radius and Gaia distance (ARD) method has been proposed to establish the SBCRs for late-type stars. Methods. We select Kepler RGB stars with high-precision asteroseismic radii (uncertainties s-band photometric data. After applying selection criteria, we obtain 626 RGB stars to build the SBCR. Among these, 100 RGBs are used as independent validation for the distance, and the remaining samples are used to fit the SBCR. Results. First, using 526 targets with asteroseismic radii and Gaia distances, nine SBCRs are proposed based on 2MASS (J, H, Ks), APASS (Johnson-B, Johnson-V), and Gaia (G) photometry. The average rms scatter in these relations is 0.075 mag, which corresponds to an uncertainty of approximately 3.5% in distance. These relations are further validated using 100 independent samples with Gaia distances, showing no bias, with a dispersion of approximately 3%. Compared to interferometric measurements, a systematic underestimation of 2.3% was observed, and the discrepancy decreases as the angular diameter increases. Additionally, the distances of eclipsing binaries in the Large Magellanic Cloud and Small Magellanic Cloud obtained using our SBCRs are generally consistent with those measured in the literature, with a dispersion of 1% and a slight overestimation of 1% to 2.5%. Conclusions. The ARD method capitalizes on two key advantages for precise stellar distance determination: a statistically

关键词： Luminance

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Measuring the Virial Factor in SDSS DR7 AGNs with Redshifted Hβ and Hα Broad Emission Lines

arXiv

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arXiv 2024年

作者： Liu, H.T. Feng, Hai-Cheng Li, Sha-Sha Bai, J.M. Li, H.Z. Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Yunnan Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Yunnan Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Physics Department Yuxi Normal University 134 Fenghuang Road Hongta District Yuxi Yunnan653100 China

Under the hypothesis of gravitational redshift induced by the central supermassive black hole, and based on line widths and shifts of redward shifted Hβ and Hα broad emission lines for more than 8000 SDSS DR7 AGNs, we measure the virial factor in determining supermassive black hole masses. The virial factor had been believed to be independent of accretion radiation pressure on gas clouds in broad-line region (BLR), and only dependent on inclination effects of BLR. The virial factor measured spans a very large range. For the vast majority of AGNs (>96%) in our samples, the virial factor is larger than f = 1 usually used in literatures. The f correction makes the percent of high-accreting AGNs decrease by about 100 times. There are positive correlations of f with the dimensionless accretion rate and Eddington ratio. The redward shifts of Hβ and Hα are mainly the gravitational origin, confirmed by a negative correlation between the redward shift and the dimensionless radius of BLR. Our results show that radiation pressure force is a significant contributor to the measured virial factor, containing the inclination effects of BLR. The usually used values of f should be corrected for high-accreting AGNs, especially high redshift quasars. The f correction increases their masses by one–two orders of magnitude, which will make it more challenging to explain the formation and growth of supermassive black holes at high redshifts. Copyright © 2024, The Authors. All rights reserved.

关键词： Active Galactic Nuclei

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A quasi-periodic oscillation in the γ-ray emission from the non-blazar active galactic nucleus PKS 0521-36

arXiv

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arXiv 2021年

作者： Zhang, Haiyun Yan, Dahai Zhang, Pengfei Yang, Shenbang Zhang, Li Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatory Chinese Academy of Sciences Kunming650011 China

Long-term γ-ray variability of a non-blazar Active Galactic Nucleus (AGN) PKS 0521-36 is investigated by using Fermi-LAT pass 8 data covering from 2008 August to 2021 March. The results show that the histogram of the γ-ray fluxes follows a log-normal distribution. Interestingly, in the analysis of ∼5.8-year (from MJD 56317 to 58447) LAT data between two outbursts (occurring during 2012 October and 2019 May respectively), a quasi-periodic oscillation (QPO) with a period of ∼ 1.1 years (∼ 5σ of significance) is found in the Lomb-Scargle Periodogram (LSP), the Weighted Wavelet Z-transform (WWZ) and the REDFIT results. This quasi-periodic signal also appears in the results of Gaussian process modeling the light curve. Therefore, the robustness of the QPO is examined by four different methods. This is the first γ-ray QPO found in a mildly beamed jet. Our results imply that the γ-ray outbursts play an important role in the formation of the γ-ray QPO. © 2021, CC BY.

关键词： Gamma rays

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New insights into the helium star formation channel of AM CVn systems with explanations of Gaia14aae and ZTFJ1637+49

arXiv

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arXiv 2022年

作者： Sarkar, Arnab Ge, Hongwei Tout, Christopher A. Institute of Astronomy The Observatories Madingley Road CambridgeCB3 OHA United Kingdom Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China

We model helium-rich stars with solar metallicity (X = 0.7, Z = 0.02) progenitors that evolve to form AM Canum Venaticorum systems through a helium-star formation channel, with the aim to explain the observed properties of Gaia14aae and ZTFJ1637+49. We show that semi-degenerate, H-exhausted (X 6 10−5), He-rich (Y ≈ 0.98) donors can be formed after a common envelope evolution (CEE) phase if either additional sources of energy are used to eject the common envelope, or a different formalism of CEE is implemented. We follow the evolution of such binary systems after the CEE phase using the Cambridge stellar evolution code, when they consist of a He-star and a white dwarf accretor, and report that the mass, radius, and mass-transfer rate of the donor, the orbital period of the system, and the lack of hydrogen in the spectrum of Gaia14aae and ZTFJ1637+49 match well with our modelled trajectories wherein, after the CEE phase Roche lobe overflow is governed not only by the angular momentum loss (AML) owing to gravitational wave radiation (AMLGR) but also an additional AML owing to α − Ω dynamos in the donor. This additional AML is modelled with our double-dynamo (DD) model of magnetic braking in the donor star. We explain that this additional AML is just a consequence of extending the DD model from canonical cataclysmic variable donors to evolved donors. We show that none of our modelled trajectories match with Gaia14aae or ZTFJ1637+49 if the systems are modelled only with AMLGR Copyright © 2022, The Authors. All rights reserved.

关键词： White dwarfs

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Contact binaries at different evolutionary stages

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Research in Astronomy and Astrophysics 2020年第10期20卷 229-248页

作者： Sheng-Bang Qian Li-Ying Zhu Liang Liu Xu-Dong Zhang Xiang-Dong Shi Jia-Jia He Jia Zhang Yunnan Observatories Chinese Academy of SciencesKunming 650216China School of Physics and Astronomy Yunnan UniversityKunming 650091China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Contact binaries consist of two strongly interacting component stars where they are filling their critical Roche lobes and sharing a common *** of them are main-sequence stars,but some of them are post main-sequence *** are good astrophysical laboratories for studying several problems such as the merging of binary stars,evolution of the common envelope,the origin of luminous red nova outbursts and the formation of rapidly rotating single stars with possible planetary systems.A large number of contact binary candidates were detected by several photometric surveys around the world and many of them were observed by the LAMOST spectroscopic *** on follow-up observations,the evolutionary states and geometrical structures of some systems were understood *** this review,we will introduce and catalog new stellar atmospheric parameters(i.e.,the effective temperature(Teff),the gravitational acceleration(log(g)),metallicity([Fe/H])and radial velocity(Vr))for 9149 EW-type contact binaries that were obtained based on low-and medium-resolution spectroscopic surveys of *** we will focus on several groups of contact binary stars,i.e.,marginal contact binary systems,deep and low-mass ratio contact binary stars,binary systems below the short-period limit of contact binaries and evolved contact *** contact binaries are at the beginning of the contact stage,while deep and low-mass ratio contact binary stars are at the final evolutionary stage of tidally locked *** statistical relations including the period-temperature relation are determined well by applying LAMOST data and their formation and evolutionary states are *** period-color relation of M-type binaries reveals that there are contact binaries below the short-period *** for and investigating contact binaries near and below this limit will help us to understand the formation of contact binary systems and a new prediction for the short-period l

关键词： binaries:eclipsing stars:late-type stars:low-mass stars:formation stars:evolution

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One Fits All: A Unified Synchrotron Model Explains GRBs with FRED-Shaped Pulses

arXiv

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arXiv 2023年

作者： Yan, Zhen-Yu Yang, Jun Zhao, Xiao-Hong Meng, Yan-Zhi Zhang, Bin-Bin School of Astronomy and Space Science Nanjing University Nanjing210093 China Key Laboratory of Modern Astronomy and Astrophysics Nanjing University Ministry of Education China Yunnan Observatories Chinese Academy of Sciences Kunming China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China

The analysis of gamma-ray burst (GRB) spectra often relies on empirical models lacking a distinct physical explanation. Previous attempts to couple physical models with observed data focus on individual burst studies, fitting models to segmented spectra with independent physical parameters. However, these approaches typically neglect to explain the time evolution of observed spectra. In this study, we propose a novel approach by incorporating the synchrotron radiation model to provide a self-consistent explanation for a selection of single-pulse GRBs. Our study comprehensively tests the synchrotron model under a unified physical condition, such as a single injection event of electrons. By tracing the evolution of cooling electrons in a decaying magnetic field, our model predicts time-dependent observed spectra that align well with the data. Using a single set of physical parameters, our model successfully fits all time-resolved spectra within each burst. Our model suggests that the rising phase of the GRB light curve results from the increasing number of radiating electrons, while the declining phase is attributed to the curvature effect, electron cooling, and the decaying magnetic field. Our model provides a straightforward interpretation of the peak energy's evolution, linked to the decline of the magnetic field and electron cooling due to the expansion of the GRB emission region. Our findings strongly support the notion that spectral and temporal evolution in GRB pulses originates from the expansion of the GRB emission region, with an initial radius of approximately 1015 cm, and synchrotron radiation as the underlying emission mechanism. Copyright © 2023, The Authors. All rights reserved.

关键词： Synchrotron radiation

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A Linear Decomposition Method to Analyze and Study Pulsar Mode Changes

arXiv

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arXiv 2025年

作者： Hao, Longfei Li, Zhixuan Shen, Faxin Xu, Yonghua Huang, Yuxiang Lee, Kejia Yu, Qingzheng Wang, Hongguang Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Department of Astronomy School of physics Peking University Beijing100871 China National Astronomical Observatory Chinese Academy of Sciences Beijing100101 China Beijing Laser Acceleration Innovation Center Huairou Beijing101400 China Department of Astronomy Xiamen University Xiamen361005 China School of Physics and Electronic Engineering Guangzhou University Guangzhou510006 China

In this paper, we present the linear decomposition method (LDM), which we developed to detect and analyze pulsar profile variations and mode changing behaviour. We developed LDM utilizing the likelihood function approach assuming the Gaussian noise. The LDM projects pulse profiles onto significance-ordered orthonormal vector bases. We show that the method is similar to the principal component analysis (PCA), but LDM can handle more general situations. We use simulated dataset and data from the Kunming 40-m radio telescope to demonstrate the application of the LDM. We found that the LDM successfully identified mode changes for well-known mode-changing PSR B0329+54 and found a continuous pulse profile evolution for PSR B0355+54 . We also show that the LDM can be used to improve the timing precision for mode changing PSR B0329+54. Copyright © 2025, The Authors. All rights reserved.

关键词： Pulsars

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Astronomical Site Monitoring System at Lijiang Observatory

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Research in Astronomy and Astrophysics 2020年第9期20卷 291-308页

作者： Yu-Xin Xin Jin-Ming Bai Bao-Li Lun Yu-Feng Fan Chuan-Jun Wang Xiao-Wei Liu Xiao Guang Yu Kai Ye Teng-Fei Song Liang Chang Shou-Sheng He Jji-Rong Mao Liang Xu Ding-Rong Xiong Xi-Liang Zhang Jian-Guo Wang Xu Ding Hai-Cheng Feng Xiang-Kun Liu Yang Huang Bing-Qiu Chen Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Sciences Chinese Academy of SciencesBeijing 100101China South-Western Institute for Astronomy Research Yunnan UiversityKunming 650500China

We installed two sets of Astronomical Site Monitoring Systems(ASMSs)at Lijiang Observatory(GMG),for the running of the 2.4-meter Lijiang optical telescope(LJT)and the 1.6-meter Multi-channel Photometric Survey Telescope(Mephisto).The Mephisto is under *** ASMS has been running on robotic mode since *** core instruments:Cloud Sensor,All-Sky Camera and AutonomousDIMM that are developed by our group,together with the commercial Meteorological Station and Sky Quality Meter,are combined into the astronomical optical site monitoring *** new Cloud Sensor's Cloud-Clear Relationship is presented for the first time,which is used to calculate the All-Sky cloud *** designed the Autonomous-DIMM located on a tower,with the same height as *** seeing data have been observed for a full ***'s data for the year 2019 are also analysed in detail,which are valuable to observers.

关键词： Astronomical Site Monitoring System Lijiang Observatory Cloud Sensor Autonomous-DIMM

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Mean-squared displacement and variance for confined Brownian motion

arXiv

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arXiv 2023年

作者： Liao, Yi Hao, Yu-Zhou Gong, Xiao-Bo Department of Materials Science and Engineering College of Engineering Southern University of Science and Technology Shenzhen518055 China Department of Physics College of Science Southern University of Science and Technology Shenzhen518055 China State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and Engineering Xi’an Jiaotong University Xi’an710049 China Yunnan Observatory Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

For one-dimension Brownian motion in the confined system with the size L, the mean-squared displacement(MSD) defined by 〈(x − x0)2〉 should be proportional to tα(t). The power α(t) should range from 1 to 0 over time, and the MSD turns from 2Dt to cL2, here the coefficient c independent of t, D being the diffusion coefficient. The paper aims to quantitatively solve the MSD in the intermediate confinement regime. The key to this problem is how to deal with the propagator and the normalization factor of the Fokker-Planck equation(FPE) with the Dirichlet Boundaries. Applying the Euler-Maclaurin approximation(EMA) and integration by parts for the small t, we obtain the MSD being (Formular presented), with (Formular presented), t and the power α(t) being 1-0.18√ξ /1-0.18√ξ. Further, we analysis the MSD and the power for the d-dimension system with γ-dimension confinement. In the case of γ 2〉. In the finite system, the variance is not necessarily the same as MSD. The initial conditions are essential to characterize the diffusion behavior described by the FPE, especially in the finite system. Under the initial condition referring to the different probability density function(PDF) being p0(x), MSD and PV should exhibit different dependencies on time, which reflect corresponding diffusion *** examples, the paper discusses the representative initial PDFs reading p0(x) = δ(x − x0), with the midpoint x0 = L/2 and the endpoint x0 = ∊(or 0+). In the case of midpoint, the MSD(equal to PV) reads 2Dt(1 − 5π3Dt)/L2 for the small t, which reflects a kind of sub-diffusion, with D being the diffusion coefficient. In the case of endpoint, the MSD(equal to PV) reads 4/π (2Dt)[1 + 2√πDt/L ] for the small t, which reflects a kind of super-diffusion. © 2023, CC BY.

关键词： Diffusion

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Generalized split monopole magnetospheres: The effects of current sheets

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Physical Review D 2021年第2期104卷 023009-023009页

作者： Huiquan Li Jiancheng Wang Yunnan Observatories Chinese Academy of Sciences 650216 Kunming China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 650216 Kunming China and Center for Astronomical Mega-Science Chinese Academy of Sciences 100012 Beijing China

We show that energy should be dissipated or extracted in the current sheet (CS) of a split magnetosphere deviating from the Michel split monopole, with the CS heating up or cooling down; but the electromagnetic energy remains unchanged everywhere. Based on the decentered monopole solution generated by symmetry in flat spacetime, we construct two generalized split monopole configurations, in which the field lines intersect with the CS at arbitrary angles. One configuration resembles the outer geometry of the so-called “new pulsar magnetosphere model”, for which up to 47% of the spin down energy is transferred to the Joule heating process in the CS. In the other configuration, we observe that negative energy is dissipated in the CS, which is usually observed in magnetospheres on rotating black holes. This means that energy is extracted simultaneously from the central star and the CS to power the output Poynting flux at infinity. We interpret the extraction of energy from the CS as that thermal energy of charged particles in the CS is transferred to the ordered kinetic energy of these particles drifting in the force-free (FF) electromagnetic fields. Hence, the CS is like an “air conditioner” in the sky, which can heat up or cool down, depending on the configurations .

关键词： Neutron stars & pulsars

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