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A new C-D-like diagram for SPB stars: The variations of period spacing as a signature of evolutionary status

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arXiv 2018年

作者： Wu, Tao Li, Yan Deng, Zhen-Min Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects 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 University of Chinese Academy of Sciences Beijing100049 China

The Slowly Pulsating B-type (SPB) stars are the upper main-sequence stars on the HR diagram. Their oscillations are high-order, low-degree g-mode and can be used to probe the structure of the radiative zone where is near the outer boundary of the convective core and constrain the chemical mixing in stellar interiors. In SPB stars, the period spacing periodically varies with periods. It has regarded as a signature of the chemical composition gradient beyond the convective core. Based on theoretical calculations, we find that the variation frequency of the period spacings (fδP) is related to the width of the μ-gradient region on the buoyancy radius (Λμ) with the relation of fδP∼ 0.5Λμ. This indicates that the variation frequency fδPis sensitive to the central hydrogen mass fraction XC(i.e., the evolutionary status). Finally, we find that the variation frequency fδPand the means of the period spacings 〈δP〉 can be used to construct a new C-D-like diagram (fδPvs. 〈δP〉) which can be used to roughly decide the stellar evolutionary stages and to approximately determine stellar mass for SPB stars. Copyright © 2018, The Authors. All rights reserved.

关键词： Stars

Determining the core radio luminosity function of radio agns via copula

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arXiv 2018年

作者： Yuan, Zunli Wang, Jiancheng Worrall, D.M. Zhang, Bin-Bin Mao, Jirong Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China HH Wills Physics Laboratory University of Bristol Tyndall Avenue BristolBS8 1TL United Kingdom School of Astronomy and Space Science Nanjing University Nanjing210093 China Key Laboratory of Modern Astronomy and Astrophysics Nanjing University Ministry of Education China

The radio luminosity functions (RLFs) of active galactic nuclei (AGNs) are traditionally measured based on total emission, which doesn't reflect the current activity of the central black hole. The increasing interest in compact radio cores of AGNs requires determination of the RLF based on core emission (i.e., core RLF). In this work we have established a large sample (totaling 1207) of radio-loud AGNs, mainly consisting of radio galaxies (RGs) and steep-spectrum radio quasars (SSRQs). Based on the sample, we explore the relationship between core luminosity (Lc) and total luminosity (Lt) via a powerful statistical tool called "Copula". The conditional probability distribution p(log Lc | log Lt) is obtained. We derive the core RLF as a convolution of p(log Lc | log Lt) with the total RLF which was determined by previous work. We relate the separate RG and SSRQ core RLFs via a relativistic beaming model and find that SSRQs have an average Lorentz factor of γ = 9.84+3−2..6150, and that most are seen within 8◦ . θ . 45◦ of the jet axis. Compared with the total RLF which is mainly contributed by extended emission, the core RLF shows a very weak luminosity-dependent evolution, with the number density peaking around z ∼ 0.8 for all luminosities. Differences between core and total RLFs can be explained in a framework involving a combination of density and luminosity evolutions where the cores have significantly weaker luminosity evolution than the extended emission. Copyright © 2018, The Authors. All rights reserved.

关键词： Luminance

NSVS 01286630: A detached binary with a close-in companion

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arXiv 2018年

作者： Zhang, Bin Qian, Sheng-bang Liao, Wen-ping Zhu, Li-ying Dong, Ai-jun Zhi, Qi-jun P. O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China School of Physics and Electronic Science Guizhou Normal University Guiyang550001 China

New photometric observations of NSVS 01286630 were performed and two sets of four-color (B, V, Rc, Ic) light curves (LCs) were obtained. Using the 2013 version of the Wilson-Devinney (W − D) code, we analyzed these data. The photometric solutions reveal that NSVS 01286630 is an active detached eclipsing binary (EB) with a high orbit inclination (nearly 90◦). Remarkably, the temperature of the primary component (the hotter star) is higher than the secondary one, but, the value of mass ratio q(MM21 ) for NSVS 0128663 is more than 1, which can be explained that the surface of the secondary component of NSVS 01286630 is covered with big cool-star-spots. Based on our new CCD mid-eclipse times and the data published until now, the variations of the mid-eclipse times were reanalyzed in detail using a weighted least-squares method. It is discovered that the (O − C) diagram of the system shows a cyclic oscillation with a period of 3.61 yr and an amplitude of 0.001 days. The cyclic variation may be caused by the light travel time effect (LTTE) due to the presence of a third companion, whose mass we calculated is M3sin(i3)=0.11 Mo. The third body may affect the orbital evolution of the central binary system by transferring the angular momentum. Copyright © 2018, The Authors. All rights reserved.

关键词： Photometry

Black hole space-time in dark matter halo

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arXiv 2018年

作者： Xu, Zhaoyi Hou, Xian Gong, Xiaobo Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects 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

For the first time, we obtain the analytical form of black hole space-time metric in dark matter halo for the stationary situation. Using the relation between the rotation velocity (in the equatorial plane) and the spherical symmetric space-time metric coefficient, we obtain the space-time metric for pure dark matter. By considering the dark matter halo in spherical symmetric space-time as part of the energy-momentum tensors in the Einstein field equation, we then obtain the spherical symmetric black hole solutions in dark matter halo. Utilizing Newman-Jains method, we further generalize spherical symmetric black holes to rotational black holes. As examples, we obtain the space-time metric of black holes surrounded by Cold Dark Matter and Scalar Field Dark Matter halos, respectively. Our main results regarding the interaction between black hole and dark matter halo are as follows: (i) For both dark matter models, the density profile always produces "cusp" phenomenon in small scale in the relativity situation;(ii) Dark matter halo makes the black hole horizon to increase but the ergosphere to decrease, while the magnitude is small;(iii) Dark matter does not change the singularity of black holes. These results are useful to study the interaction of black hole and dark matter halo in stationary situation. Particularly, the "cusp" produced in the 0 ∼ 1 kpc scale would be observable in the Milky Way. Perspectives on future work regarding the applications of our results in astrophysics are also briefly discussed. Copyright © 2018, The Authors. All rights reserved.

关键词： Gravitation

Black hole shadow of Sgr a∗ in dark matter halo

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arXiv 2018年

作者： Hou, Xian Xu, Zhaoyi Zhou, Ming Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects 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 University of Chinese Academy of Sciences Beijing100049 China

We study, for the first time, the shadow of the supermassive black hole Sgr A∗ at the center of the Milky Way in dark matter halos. For the Cold Dark Matter and Scalar Field Dark Matter models considered in this work, the apparent shape of the shadow depends upon the black hole spin a and the dark matter parameter k. We find that both dark matter models influence the shadow in a similar way. The shadow is a perfect circle in the non-rotating case ( a = 0) and a deformed one in the rotating case ( a ≠ 0). The size of the shadow increases with increasing k in both non-rotating and rotating cases, while the shadow gets more and more distorted with increasin g a in the rotating case. We further investigate the black hole emission rate in both dark matter halos. We find that the emission rate decreases with increasing k and the peak of the emission shifts to lower frequency. Finally, by calculating the angular radius of the shadow, we estimate that the dark matter halo could influence the shadow of Sgr A∗ at a level of order of magnitude of 10-3μas and 10-5μas, for CDM and SFDM, respectively. Future astronomical instruments with high angular resolution would be able to observe this effect and shed light on the nature of Sgr A∗. More interestingly, it may be possible to distinguish between CDM and SFDM models given the resolutions required differing by two orders of magnitude from each other. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

A scenario on the power-law total mass-density profile of the inner regions of early-type-galaxies

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arXiv 2018年

作者： Li, Rui Xu, Zhaoyi Wang, Jiancheng Hou, Xian Tang, Meirong Guo, Xiaotong Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 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 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China

We naturally obtain a power-law total mass-density profile for the inner regions (within several effective radius) of early-type galaxies(ETGs) from space-time structures, which are described by the static spherically-symmetric solutions of Einstein equations with the perfect fluid matters. We point out that, in the inner region of an early type galaxy, the average value of the equation of state ω determines the power-law index γ of the total mass-density profile given by Koopmans et al. (2006). We then use 119 galaxy-galaxy strong gravitational lensing systems from SLACS, BELLS, BELLS GALLERY and SL2S, to constrain the equation of state ω for the inner regions of ETGs. We find that the average value of ω for totally 119 ETGs is ω = −0.315 ± 0.073 (68% CL), which is very close to −1/3. If ω = −1/3 is the best value to describe the equation of state of the inner regions of the dark matter in galaxies, the deviation from −1/3 could represent the mixture of baryonic matter and dark matter in galaxies. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Optical and γ-ray variability behaviors of 3C 454.3 from 2006 to 2011

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arXiv 2018年

作者： Fan, Xu-Liang Li, Shao-Kun Liao, Neng-Hui Chen, Liang Liu, Hong-Tao Lu, Kai-Xing Yan, Da-Hai Zhang, Rui-Yu Guo, Qian Wu, Qingwen Bai, Jin-Ming School of Physics Huazhong University of Science and Technology Wuhan430074 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China University of Chinese Academy of Sciences Beijing100049 China

We present our photometric monitoring of a flat spectrum radio quasar (FSRQ) 3C 454.3 at Yunnan observatories from 2006 to 2011. We find that the optical color of 3C 454.3 shows obvious redder-when-brighter trend, which reaches a saturation stage when the source is brighter than 15.15 mag at V band. We perform a simulation with multiple values of disk luminosity and spectral index to reproduce the magnitude-color diagram. The results show that the contamination caused by the disk radiation alone is difficult to produce the observed color variability. The variability properties during the outburst in December 2009 are also compared with γ-ray data derived from Fermi γ-ray space telescope. The flux variation of these two bands follow a linear relation with Fγ∝ FR1.14±0.07, which provides an observational evidence for external Compton process in 3C 454.3. Meanwhile, this flux correlation indicates that electron injection is the main mechanism for variability origin. We also explore the variation of the flux ratio Fγ/FRand the detailed structures in the lightcurves, and discuss some possible origins for the detailed variability behaviors. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Frequency identification and asteroseismic analysis of the red giant kic 9145955: Fundamental parameters and helium core size

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arXiv 2018年

作者： Zhang, Xinyi Wu, Tao Li, Yan Yunnan Observatories Chinese Academy of Sciences 396Yangfangwang Guandu District Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang DistrictBeijing100012 China

We have analyzed 18 quarters of long-cadence data of KIC 9145955 provided by Kepler, and extracted 61 oscillation frequencies from these high precision photometric data. The oscillation frequencies include 7 l = 0 modes, 44 l = 1 modes, 7 l = 2 modes, and 3 l = 3 modes. We identify l = 0 modes as p modes and l = 2 modes as p-dominated modes. For l = 1 modes, all of them are identified as mixed modes. These mixed modes can be used to determine the size of the helium core. We conduct a series of asteroseismic models and the size of the helium core is determined to be MHe = 0.210 ± 0.002 Mo and RHe = 0.0307 ± 0.0002 Ro. Furthermore, we find that only the acoustic radius τ0 can be precisely determined with the asteroseismic method independently. The value of tau;0 is determined to be 0.494 ± 0.001 days. By combining asteroseismic results and spectroscopic observations, we obtain the best-fitting model. The physical parameters of this model are M = 1.24 Mo, Z = 0.009, α = 2.0, Teff = 5069 K, log g = 3.029, R = 5.636 Ro, and L = 18.759 Lo. In addition, we think that the observed frequency F39 (96.397 Hz) is more appropriate to be identified as a mixed mode of the most p-dominated. Copyright © 2018, The Authors. All rights reserved.

关键词： Helium

Statistical study of the swift X-ray flash and X-ray rich gamma-ray bursts

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arXiv 2018年

作者： Bi, Xiongwei Mao, Jirong Liu, Chuanxi Bai, Jin-Ming Department of Physics Honghe University Mengzi661199 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan Province650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

We build a comprehensive sample to statistically describe the properties of X-ray flashes (XRFs) and X-ray riches (XRRs) from the latest third Swift Burst Alert Telescope (BAT3) catalog of Gamma-ray bursts (GRBs). We obtain 81 XRFs, 540 XRRs, and 394 classical GRBs (C-GRBs). We statistically explore the different properties of the γ-ray prompt emission, the X-ray emission, the X-ray lightcurve type, the association with supernovae (SNe), and the host galaxy properties for these sources. We confirm that most XRFs/XRRs are long GRBs with low values of peak energy Epeakobs and they are low-luminosity GRBs. XRFs, XRRs, and C-GRBs follow the same EX,iso-Eγ,iso-Epeak,z correlations. Compared to the classical GRBs, XRFs are favorable to have the association with SN explosions. We do not find any significant differences of redshift distribution and host galaxy properties among XRFs, XRRs, and C-GRBs. We also discuss some observational biases and selection effects that may affect on our statistical results. The GRB detectors with wide energy range and low energy threshold are expected for the XRF/XRR research in the future. Copyright © 2018, The Authors. All rights reserved.

关键词： Gamma rays