检索结果-内蒙古大学图书馆

arXiv 2020年

作者： Xiang, Yue Gu, Shenghong Collier Cameron, A. Barnes, J.R. Christensen-Dalsgaard, J. Grundahl, F. Antoci, V. Andersen, M.F. Pallé, P.L. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences Beijing101408 China School of Physics and Astronomy University of St Andrews FifeKY16 9SS United Kingdom Department of Physical Sciences Open University Walton Hall Milton KeynesMK7 6AA United Kingdom Department of Physics and Astronomy Aarhus University Ny Munkegade 120 AarhusDK-8000 Denmark Instituto de Astrofísica de Canarias La Laguna TenerifeE-38205 Spain Departamento de Astrofísica Universidad de la Laguna La Laguna TenerifeE-38205 Spain

We present new Doppler images of both components of the double-lined binary σ2CrB, based on the high-resolution spectroscopic data collected during 11 nights in 2015 March-April. The observed spectra form two independent data sets with sufficient phase coverage. We apply the least-squares deconvolution to all observed spectra to obtain high signal-to-noise mean profiles, from which we derive the Doppler images of both components of σ2CrB simultaneously. The surfaces of both F9 and G0 components are dominated by pronounced polar spots. The F9 component exhibits a weak spot at latitude 30° and its mid-to-low latitudes are relatively featureless. The G0 star shows an extended spot structure at latitude 30°, and its surface spot coverage is larger than that of the F9 star, which suggests a higher level of magnetic activity. With the cross-correlation method, we derive a solar-like surface differential rotation on the G0 star of cr2CrB for the first time, and the surface shear rate is ΔΩ = 0.180 + 0.004 rad d-1and a = ΔΩ/Ωeq= 0.032 + 0.001. We do not obtain a clear surface shear law for the F9 star due to the lack of mid-to-low latitude features, but detect a systematic longitude shift of high-latitude spots, which indicates a slower rotation with respect to the co-rotating frame. Copyright © 2020, The Authors. All rights reserved.

关键词： Stars

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Reddening of the blr and nlr in agn from a systematic analysis of balmer decrement

arXiv

引用

arXiv 2018年

作者： Lu, Kai-Xing Zhao, Yinghe Bai, Jin-Ming Fan, Xu-Liang Chinese Academy of Sciences KunmingYunnan650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Physics Huazhong University of Science and Technology Wuhan430074 China

We selected an active galactic nuclei (AGN) sample (0 b/Hβb) and narrow-line Balmer decrements (Hαn/Hβn) of 554 selected AGNs. We found that the distributions of Balmer decrements can be fitted by a Gaussian function and give the best estimates of Hαb/Hβb = 3.16 with a standard deviation 0.07 dex, and Hαn/Hβn = 4.37 with a standard deviation 0.10 dex. We inspected the distributions of Hαb/Hβb and Hαn/Hβn in the Baldwin−Phillips−Terlevich (BPT) diagram and found that only narrow-line Balmer decrements depend on the physical conditions of the narrow-line region (NLR). We tested the relationship between Hαb/Hβb and Hαn/Hβn, and found that Hαb/Hβb does not correlate with Hαn/Hβn. We investigated the relationship between Balmer decrements and Seyfert sub-type, and found that only broad-line Balmer decrements correlate with Seyfert sub-type, We also examined the dependency of Balmer decrements on AGN properties, and found that Balmer decrements have no correlation with optical luminosity, but show some dependence on accretion rate. These results indicate that the NLR is subject to more reddening by dust than the broad-line region (BLR). Copyright © 2018, The Authors. All rights reserved.

关键词： Statistics

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SN 2015bf: A fast declining type II supernova with flash-ionised signatures

arXiv

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arXiv 2021年

作者： Lin, Han Wang, Xiaofeng Zhang, Jujia Lin, Weili Mo, Jun Filippenko, Alexei V. Zheng, WeiKang Brown, Peter J. Xiang, Danfeng Huang, Fang Cai, Yongzhi Zhang, Tianmeng Li, Xue Rui, Liming Zhang, Xinghan Sai, Hanna Zhao, Xulin Graham, Melissa L. Shivvers, I. Halevi, G. Yuk, H. Brink, Thomas G. Tsinghua University Beijing100084 China Beijing Planetarium Beijing Academy of Sciences and Technology Beijing100044 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 20A Datun Road Chaoyang District Beijing100012 China Department of Astronomy University of California BerkeleyCA94720-3411 United States Miller Institute for Basic Research in Science University of California BerkeleyCA94720-3411 United States George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy Texas A&M University Department of Physics and Astronomy 4242 TAMU College StationTX77843 United States Department of Astronomy Shanghai Jiao Tong University Shanghai200240 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China School of Science Tianjin University of Technology Tianjin300384 China DiRAC Institute Department of Astronomy University of Washington Box 351580 SeattleWA98195 United States Homer L. Dodge Department of Physics and Astronomy University of Oklahoma 440 W. Brooks St. NormanOK73019 United States

We present optical and ultraviolet photometry, as well as optical spectra, for the type II supernova (SN) 2015bf. Our observations cover the phases from ∼ 2 to ∼ 200 d after explosion. The first spectrum is characterised by a blue continuum with a blackbody temperature of ∼ 24, 000 K and flash-ionised emission lines. After about one week, the spectra of SN 2015bf evolve like those of a regular SN II. From the luminosity of the narrow emission component of Hα, we deduce that the mass-loss rate is larger than ∼ 3.7 × 10−3 M☉ yr−1. The disappearance of the flash features in the first week after explosion indicates that the circumstellar material is confined within ∼ 6 × 1014 cm. Thus, we suggest that the progenitor of SN 2015bf experienced violent mass loss shortly before the supernova explosion. The multiband light curves show that SN 2015bf has a high peak luminosity with an absolute visual magnitude MV = −18.11 ±0.08 mag and a fast post-peak decline with a V-band decay of 1.22 ±0.09 mag within ∼ 50 d after maximum light. Moreover, the R-band tail luminosity of SN 2015bf is fainter than that of SNe II with similar peak by 1–2 mag, suggesting a small amount of 56Ni (∼ 0.009 M☉) synthesised during the explosion. Such a low nickel mass indicates that the progenitor of SN 2015bf could be a super-asymptotic-giant-branch star that collapsed owing to electron capture. Copyright © 2021, The Authors. All rights reserved.

关键词： Supernovae

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Lijiang 2.4-meter Telescope and its Instruments∗

arXiv

引用

arXiv 2019年

作者： Wang, Chuan-Jun Bai, Jin-Ming Fan, Yu-Feng Mao, Jirong Chang, Liang Xin, Yu-Xin Zhang, Ju-Jia Lun, Bao-Li Wang, Jian-Guo Zhang, Xi-Liang Ying, Mei Lu, Kai-Xing Wang, Xiao-Li Ji, Kai-Fan Xiong, Ding-Rong Yu, Xiao-Guang Ding, Xu Ye, Kai Xing, Li-Feng Yi, Wei-Min Xu, Liang Zheng, Xiang-Ming Feng, Yuan-Jie He, Shou-Sheng Wang, Xue-Li Liu, Zhong Chen, Dong Xu, Jun Qin, Song-Nian Zhang, Rui-Long Tan, Hui-Song Li, Zhi Lou, Ke Li, Jian Liu, Wei-Wei Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang GuanduKunming650216 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 Astrophysics Center of Guangzhou University Guangzhou510006 China

Lijiang 2.4-meter Telescope(LJT), the largest common-purpose optical telescope in China, has been applied to the world-wide astronomers since 2008. It is located at Gaomeigu site, Lijiang Observatory(LJO), the southwest of China. The site has very good observational conditions. Since 10-year operation, several instruments have been equipped on the LJT. Astronomers can perform both photometric and spectral observations. The main scientific goals of LJT include photometric and spectral evolution of supernova, reverberation mapping of active galactic nucleus, physical properties of binary star and near-earth object(comet and asteroid), identification of exoplanet, and all kinds of transients. Until now, the masses of 41 high accretion rate black holes have been measured, and more than 168 supernova have been identified by the LJT. More than 190 papers related to the LJT have been published. In this paper, the general observation condition of the Gaomeigu site is introduced at first. Then, the LJT structure is described in detail, including the optical, mechanical, motion and control system. The specification of all the instruments, and some detailed parameters of the YFOSC is also presented. Finally, some important scientific results and future expectations Copyright © 2019, The Authors. All rights reserved.

关键词： Photometry

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Photometric analysis of the eclipsing polar MN Hya

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Research in Astronomy and Astrophysics 2018年第7期18卷 11-20页

作者： Qi-Shan Wang Sheng-Bang Qian Zhong-Tao Han Miloslav Zejda Eduardo Fernandez-Lajus Li-Ying Zhu Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming650216China University of Chinese Academy of Sciences Beijing 100049China Department of Theoretical Physics and Astrophysics Masaryk UniversityKotlfirgkfi 2Bmo 611 37Czech Republic Facultad de Ciencias Astron6micas y Geoffsicas Universidad Nacional de La PlataPaseo del Bosque s/n1900La PlataPcia.Bs.As.Argentina Instituto de Astroffsica de La Plata(CCT La plata-CONICET/UNLP) Argentina

As an eclipsing polar with a 3.39 h orbital period, MN Hya was going through a state change when we observed it during 2009-2016. Ten new mid-eclipse times, along with others obtained from literature, allow us to give a new ephemeris. The residuals of a linear fit show that period decreased during the phase of state change, which means angular momentum was lost during this phase. The associated X-ray observation indicates the mass accretion rate was about 3.6 x 10^-9 Mo yr^-1. The period decrease indicates that at least 60% of mass being transferred from the secondary was lost, maybe in the form of spherically symmetric stellar wind. In the high state, the data show the intensity of flickering reduced when the system had a higher accretion rate, and that flickering sticks out with a primary timescale of about 2 min, which implies the position of the threading point was about 30 white dwarf radii above its surface. The trend of light curves for the system in its high state follows that of the low state for a large fraction of the phase interval from phase 0 to phase 0.4 since, starting at phase 0.4, the cyclotron feature is visible, and the primary intensity hump of the light curves near phase 0.7 when the system is in the high state did not appear on the curve when it was in the low state. Those facts contradict predictions of the two-pole model.

关键词： techniques photometric-stars cataclysmic variables eclipsing polars-stars individ-ual （MN Hya）

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GeV-TeV γ-ray energy spectral break of BL Lac objects

arXiv

引用

arXiv 2018年

作者： Zhong, W. Liu, W.G. Zheng, Y.G. Department of Physics Yunnan Normal University Kunming650092 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

In this paper, we compile the very-highenergy and high-energy spectral indices of 43 BL Lac objects from the literature. Based on a simple math model, ΔΓobs= αz + β, we present evidence for the origin of an observed spectral break that is denoted by the difference between the observed very-high-energy and high-energy spectral indices, ΔΓobs. We find by linear regression analysis that α ≠ 0 and β ≠ 0. These results suggest that the extragalactic background light attenuation and the intrinsic curvature dominate on the GeV-TeV γ-ray energy spectral break of BL Lac objects. We argue that the extragalactic background light attenuation is an exclusive explanation for the redshift evolution of the observed spectral break. Copyright © 2018, The Authors. All rights reserved.

关键词： Regression analysis

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Physical properties and catalog of EW-type eclipsing binaries observed byLAMOST

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Research in Astronomy and Astrophysics 2017年第8期17卷 109-122页

作者： Sheng-Bang Qian Jia-Jia He Jia Zhang Li-Ying Zhu Xiang-Dong Shi Er-Gang Zhao Xiao Zhou Yunnan Observatories Chinese Academy of Sciences Kunming 650011 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China University of the Chinese Academy of Sciences Beijing 100049 China

EW-type eclipsing binaries(hereafter called EWs)are strong interacting systems in which both component stars usually fill their critical Roche lobes and share a common *** EWs were discovered by several deep photometric surveys and there were about 40 785 EW-type binary systems listed in the international variable star index(VSX)by 2017 March 13.7938 of them were observed with LAMOST by 2016 November 30 and their spectral types were *** atmospheric parameters of 5363 EW-type binary stars were determined based on good spectroscopic *** the paper,those EWs are cataloged and their properties are *** distributions of orbital period(P),effective temperature(T),gravitational acceleration(log(g)),metallicity([Fe/H])and radial velocity(RV)are presented for these observed EW-type *** is shown that about 80.6% of sample stars have metallicity below zero,indicating that EW-type systems are old stellar *** is in agreement with the conclusion that EW binaries are formed from moderately close binaries through angular momentum loss via magnetic braking that takes a few hundred million to a few billion *** unusually high metallicities of a few percent of EWs may be caused by contamination of material from the evolution of unseen neutron stars or black holes in the *** correlations between orbital period and effective temperature,gravitational acceleration and metallicity are presented and their scatters are mainly caused by(i)the presence of third bodies and(ii)sometimes wrongly determined *** is shown that some EWs contain evolved component stars and the physical properties of EWs mainly depend on their orbital *** is found that extremely short-period EWs may be older than their long-period cousins because they have lower *** reveals that they have a longer timescale of pre-contact evolution and their formation and evolution are mainly driven by angular momentum loss vi

关键词： stars binaries close—stars binaries spectroscopic—stars binaries eclipsing—stars evolution

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Observational constraints on the rastall gravity from rotation curves of low surface brightness galaxies

arXiv

引用

arXiv 2019年

作者： Tang, Meirong Xu, Zhaoyi Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory of Particle Astrophysics Institute of High Energy Physics 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 University of Chinese Academy of Sciences Beijing100049 China

The Rastall gravity is a modification of Einstein's general relativity, in which the energy-momentum conservation is not satisfied and depends on the gradient of the Ricci curvature. It is in dispute whether the Rastall gravity is equivalent to the general relativity (GR). In this work, we constrain the theory using the rotation curves of Low Surface Brightness (LSB) spiral galaxies. Through fitting the rotation curves of LSB galaxies, we obtain the parameter β of the Rastall gravity. The β values of LSB galaxies satisfy Weak Energy Condition (WEC) and Strong Energy Condition(SEC). Combining the β values of type Ia supernovae and gravitational lensing of elliptical galaxies on the Rastall gravity, we conclude that the Rastall gravity is equivalent to the general relativity. Copyright © 2019, The Authors. All rights reserved.

关键词： Galaxies

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SPECTRAL PROPERTIES OF MAGNETOHYDRODNAMIC TURBULENCE REVEALED BY POLARIZATION SYNCHROTRON EMISSION WITH FARADAY ROTATION

arXiv

引用

arXiv 2018年

作者： Zhang, Jian-Fu Lazarian, Alex Xiang, Fu-Yuan Department of Physics Xiangtan University Xiangtan Hunan411105 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Astronomy Department University of Wisconsin MadisonWI53711 United States

We investigate how to recover the spectral properties of underlying magnetohydrodynamic (MHD) turbulence using fluctuation statistics of synchrotron polarization radiation, based on the synthetic observations. Taking spatially coincident, separated, and compounded synchrotron emission and Faraday rotation regions into account, we extract the power spectrum of synchrotron polarization intensities integrated along the line of sight. Our results demonstrate that in the short wavelength range, the power spectra reflect fluctuation statistics of the perpendicular component of turbulent magnetic fields, and the spectra at long wavelengths reveal the fluctuation of the Faraday rotation density, which is a product of the parallel component of magnetic field and thermal electron density. We find that our numerical results (in the case of spatially coincident regions) are in agreement with the analytical prediction in Lazarian & Pogosyan (2016), and this theoretical prediction is applicable to more complicated settings, i.e., the spatially separated and compounded regions. We simulate telescopic observations that incorporate the effects of telescope angular resolution and noise, and find that statistics of underlying MHD turbulence can be recovered successfully. We expect that the technique can be applied to a variety of astrophysical environments, with existing synchrotron data cubes and a large number of forthcoming data sets from such as the LOw-Frequency Array for Radio astronomy (LOFAR), the Square Kilometer Array (SKA) and the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Copyright © 2018, The Authors. All rights reserved.

关键词： Power spectrum

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EXPLORING THE CONVECTIVE CORE OF THE HYBRID δ SCUTI-γ DORADUS STAR COROT 100866999 WITH ASTEROSEISMOLOGY

arXiv

引用

arXiv 2019年

作者： Chen, Xinghao Li, Yan Zhang, Xiaobin 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 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 of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

We computed a grid of theoretical models to fit the δ Scuti frequencies of CoRoT 100866999 detected earlier from the CoRoT timeserials. The pulsating primary star is determined to be a main sequence star with a rotation period of 4.1+0−0..65 days, rotating slower than the orbital motion. The fundamental parameters of the primary star are determined to be M = 1.71+0−0..1304 M∙, Z = 0.012+0−0..004000, fov = 0.02+0−0..0002, Teff = 8024+249−297 K, L = 11.898+2−1..156847 L∙, log g = 4.166+0−0..013002, R = 1.787+0−0..040016 R∙, and Xc = 0.488+0−0..011020, matching well those obtained from the eclipsing light curve analysis. Based on the model fittings, p1 and p5 are suggested to be two dipole modes, and p3, p4, p6, and p7 to be four quadrupole modes. In particular, p4 and p7 are identified as two components of one quintuplet. Based on the best-fitting model, we find that p1 is a g mode and the other nonradial modes have pronounced mixed characters, which give strong constraints on the convective core. Finally, the relative size of the convective core of CoRoT 100866999 is determined to Rconv/R = 0.0931+0−0..00030013. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

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