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Photometric study for near-Earth asteroid (155140) 2005 UD

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arXiv 2020年

作者： Huang, Jianing N. Muinonen, K. Chen, T. Wang, Jianing B. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for Structure and Evolution of Celestial Objects CAS Kunming650216 China Department of Physics University of Helsinki Gustaf Hällströmin katu 2 P.O. Box 64 HelsinkiFI-00014 U Finland Finnish Geospatial Research Institute Geodeetinrinne 2 MasalaFI-02430 Finland Corona borealis Observatiories Ali China

The Apollo-type near-Earth asteroid (155140) 2005 UD is thought to be a member of the Phaethon-Geminid meteor stream Complex (PGC). Its basic physical parameters are important for unveiling its origin and its relationship to the other PGC members as well as to the Geminid stream. Adopting the Lommel-Seeliger ellipsoid method and H,G1,G2 phase function, we carry out spin, shape, and phase curve inversion using the photometric data of 2005 UD. The data consists of 11 new lightcurves, 3 lightcurves downloaded from the Minor Planet Center, and 166 sparse data points downloaded from the Zwicky Transient Facility database. As a result, we derive the pole solution of (285◦.8+1−5.13, −25◦.8+5−1235) in the ecliptic frame of J2000.0 with the Copyright © 2020, The Authors. All rights reserved.

关键词： Asteroids

Candidates of eclipsing multiples based on extraneous eclipses on binary light curves： KIC 7622486, KIC 7668648, KIC 7670485 and KIC 8938628

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Research in Astronomy and Astrophysics 2017年第3期17卷 1-12页

作者： Jia Zhang Sheng-Bang Qian Jian-Duo He Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China

Four candidates of eclipsing multiples, based on new extraneous eclipses found on Kepler binary light curves, are presented and studied. KIC 7622486 is a double eclipsing binary candidate with orbital periods of 2.2799960 d and 40.246503 d. The two binary systems do not eclipse each other in the line of sight, but there is mutual gravitational influence between them which leads to the small but definite eccentricity of 0.0035（0.0022） associated with the short 2.2799960 d period orbit. KIC 7668648 is a hierarchical quadruple system candidate, with two sets of solid 203 4- 5 d period extraneous eclipses and another independent set of extraneous eclipses. A clear and credible extraneous eclipse is found on the binary light curve of KIC 7670485 which makes it a triple system candidate. Two sets of extraneous eclipses with periods of about 390 d and 220 d are found on KIC 8938628 binary curves, which not only confirm the previous conclusion of the 388.5 4- 0.3 triple system, but also indicate new additional objects that make KIC 8938628 a hierarchical quadruple system candidate. The results from these four candidates will contribute to the field of eclipsing multiples.

关键词： binaries eclipsing - techniques photometric - methods observational

High-velocity feature as the indicator of the stellar population of Type Ia supernovae

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arXiv 2019年

作者： Meng, Xiang-Cun 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 20A Datun Road Chaoyang District Beijing100012 China

Although type Ia supernovae (SNe Ia) are very useful in many astrophysical fields, their exact nature is still unclear, e.g. the progenitor and explosion models. The high-velocity features (HVFs) in optical spectra of SNe Ia could provide some meaningful information to constrain the nature of SNe Ia. Here, I show strong evidence that the SNe Ia with strong CaII infrared triple (CaII IR3) HVF around maximum brightness associate with relatively younger population than those with weak CaII IR3 HVF, e.g. the SNe Ia with strong CaII IR3 HVF tend to occur in late-type galaxy, or early-type galaxy with significant star formation. In addition, using pixel statistics I find that the SNe Ia with strong maximum-light CaII IR3 HVF show a higher degree of association with star formation index, e.g. Hα or near-UV emission, than those with weak CaII IR3 HVF. Moreover, I find that the strength of the CaII IR3 HVF is linearly dependent on the difference of the absorption-weighted velocities between CaII IR3 and SiII 635.5 nm absorption lines, which then is a good index to diagnose whether or not there is a high-velocity component in the CaII IR3 absorption feature in the spectra of SNe Ia. I finally discussed the origin of the HVFs and the constraints from our discoveries on the progenitor model of SNe Ia. Copyright © 2019, The Authors. All rights reserved.

关键词： White dwarfs

ASAS J174406+2446.8 is identified as a marginal-contact binary with a possible cool third body

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arXiv 2020年

作者： Shi, Xiang-Dong Qian, Sheng-Bang Li, Lin-Jia Na, Wei-Wei Zhou, Xiao P. O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Yuxi normal university Fenghuang Road 134# Yuxi653100 China

ASAS J174406+2446.8 was originally found as a δ Scuti-type pulsating star with the period P=0.189068 days by ASAS survey. However, the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational instability strip on the log g - T diagram of δ Scuti pulsating stars. To understand the physical properties of the variable star, we observed it by the 1.0-m Cassegrain reflecting telescope at Yunnan Observatories. Multicolor light curves in B, V, Rc and Ic bands were obtained and are analyzed by using the W-D program. It is found that this variable star is a shallow-contact binary with an EB-type light curve and an orbital period of 0.3781 days rather than a δ Scuti star. It is a W-subtype contact binary with a mass ratio of 1.135(±0.019) and a fill-out factor of 10.4(±5.6) %. The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn, II Per and GW Tau. All of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation theory. The linear ephemeris was corrected by using 303 new determined times of light minimum. It is detected that the O - C curve shows a sinusoidal variationthat could be explained by the light-travel-time effect via the the presence of a cool red dwarf. The present investigation reveals that some of the δ Scuti-type stars beyond the red edge of pulsating instability strip on the log g - T diagram are misclassified eclipsing binaries. To understand their structures and evolutionary states, more studies are required in the *** Codes 85A05 Copyright © 2020, The Authors. All rights reserved.

关键词： Travel time

evolution of the quiescent disk surrounding a superoutburst of the dwarf nova TW virginis

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arXiv 2020年

作者： Dai, Zhibin Szkody, Paula Garnavich, Peter M. Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu DistrictKunming650216 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 Yuquan Road Shijingshan District Beijing100049 China University of Washington SeattleWA98195 United States University of Notre Dame Notre DameIN46556 United States

Portions of the Kepler K2 Short Cadence light curve of the dwarf nova (DN) TW Vir at quiescence are investigated using light curve modeling. The light curve was separated into 24 sections, each with a data length of ∼ 0.93 d, comprising 4 sections before and 20 after a superoutburst (SO). Due to the morphological differences, the quiescent orbital modulation is classified into three types. Using a fixed disk radius and the two component stellar parameters, all 24 synthetic disk models from the sections show a consistent configuration, consisting of a disk and two hotspots: one at the vertical side of the edge of the disk and the other one on the surface of the disk. Before the SO, the disk and a ringlike surface-hotspot are suddenly enhanced, triggering a precursor and then SO. At the end of the quiescent period following the SO and before the first normal outburst, the edge-hotspot becomes hotter, while the surface-hotspot switches into a "coolspot" with a coverage of nearly one-half of the disk surface. During quiescence, the surface-hotspot is always located at the outer part of the disk with a constant radial width. A flat radial temperature distribution of the disk is found and appears flatter when approaching the outburst. Like many U Gem-type DN with orbital periods of 3-5 hr, the mass transfer rate is significantly lower than the predictions of the standard/revised models of CV evolution. Copyright © 2020, The Authors. All rights reserved.

关键词： Mass transfer

Geometric phase and topological phase diagram of the one-dimensional XXZ Heisenberg spin chain in a longitudinal field

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arXiv 2019年

作者： Liao, Yi Gong, Xiao-Bo Guo, Chu Chen, Ping-Xing Department of Physics National University of Defense Technology Changsha410073 China Interdisciplinary Center for Quantum Information National University of Defense Technology Changsha410073 China Yunnan Observatory and Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Henan Key Laboratory of Quantum Information and Cryptography SSF IEU Zhengzhou450001 China

In this paper, we determine the geometric phase for the one-dimensional XXZ Heisenberg chain with spin-1/2, the exchange couple J and the spin anisotropy parameter ∆ in a longitudinal field(LF) with the reduced field strength h. Using the Jordan-Wigner transformation and the mean-field theory based on the Wick’s theorem, a semi-analytical theory has been developed in terms of order parameters which satisfy the self-consistent equations. The values of the order parameters are numerically computed using the matrix-product-state(MPS) method. The validity of the mean-filed theory could be checked through the comparison between the self-consistent solutions and the numerical results. Finally, we draw the the topological phase diagrams in the case J 0. Copyright © 2019, The Authors. All rights reserved.

关键词： Phase diagrams

Is bremsstrahlung a possible mechanism to explain the thermal feature in the GRB 130925A X-ray afterglow?

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arXiv 2019年

作者： Liu, Jie-Ying Mao, Jirong Yunnan Observatories Chinese Academy of Sciences KunmingYunnan Province650011 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 Kunming650011 China

It has been reported that some X-ray spectra of gamma-ray burst (GRB) afterglows cannot be fitted by a simple power law. A blackbody component is added to precisely fit the thermal feature in these spectra. Alternatively, we propose that bremsstrahlung radiation can also be one possible mechanism to explain the thermal component of the GRB X-ray afterglow. In particular, we examine the X-ray afterglow of the ultra-long GRB 130925A in this paper. By our calculation, we find that the X-ray thermal component observed by both Swift-XRT and NuSTAR can be well explained by the bremsstrahlung radiation. Our results indicate that the GRBs with the bremsstrahlung emission in the X-ray afterglow could be born in a metal-rich and dusty environment. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

Effects of Binary Interactions on the Early-type Galaxy Chemical evolution and Gas Cooling Functiontwo

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Chinese Astronomy and Astrophysics 2018年第4期42卷 527-537页

作者： Lang, Wang Yunnan Astronomical Observatories Chinese Academy of Sciences Kunming 650011 China University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China

In the galaxy parameter fitting by means of stellar population synthesis, it is found that compared with the evolutionary population synthesis (EPS) model without binary interactions, the stellar age and metallicity of a galaxy derived from the EPS model with binary interactions are larger. But, we are still unclear how the binary interactions affect the galaxy evolution. For the early-type galaxies with the UV-excess phenomenon, there are two main-stream explanations: recent star formation (RSF) and binary interactions. In this study, we obtain the mass return rate and chemical yield for the stellar populations with and without binary interactions. In combination with the galaxy chemical evolution and photoionization models, we study the effects of binary interactions on the chemical evolution and metallicity evolution for the early-type galaxies with the UV-excess phenomenon under the two formation mechanisms. We find that the inclusion of binary interactions can raise the ejected mass, metallicity, alpha element, and accelerate the gas cooling. These can reasonably explain the conclusions made by the EPS models. Moreover, we find that the gas cooling is more efficient under the UV-excess formation mechanism by the binary interactions rather than the RSF, and the ratio of element abundance is different for the two mechanisms, which can be further used to distinguish these two mechanisms. © 2018

关键词： Abundances—galaxies evolution Galaxies ISM—galaxies

evolution of Dipolar Mixed-mode Coupling Factor in Red Giant Stars: Impact of Buoyancy Spike

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arXiv 2022年

作者： Jiang, Chen Cunha, Margarida Christensen-Dalsgaard, Joergen Zhang, Qiansheng S. Gizon, Laurent Max-Planck-Institut für Sonnensystemforschung Justus-von-Liebig-Weg 3 Göttingen37077 Germany Instituto de Astrofísica e Ciências do Espaço Universidade do Porto CAUP Rua das Estrelas Porto4150-762 Portugal Stellar Astrophysics Centre Department of Physics and Astronomy Aarhus University Ny Munkegade 120 Aarhus CDK-8000 Denmark 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 University of Chinese Academy of Sciences Beijing100049 China Institut für Astrophysik Georg-August-Universität Göttingen Friedrich-Hund-Platz 1 Göttingen37077 Germany Center for Space Science NYUAD Institute New York University Abu Dhabi Abu Dhabi United Arab Emirates

Mixed modes observed in red giants allow for investigation of the stellar interior structures. One important feature in these structures is the buoyancy spike caused by the discontinuity of the chemical gradient left behind during the first dredge-up. The buoyancy spike emerges at the base of the convective zone in low-luminosity red giants and later becomes a glitch when the g-mode cavity expands to encompass the spike. Here, we study the impact of the buoyancy spike on the dipolar mixed modes using stellar models with different properties. We find that the applicability of the asymptotic formalisms for the coupling factor, q, varies depending on the location of the evanescent zone, relative to the position of the spike. Significant deviations between the value of q inferred from fitting the oscillation frequencies and either of the formalisms proposed in the literature are found in models with a large frequency separation in the interval 5 to 15 µHz, with evanescent zones located in a transition region which may be thin or thick. However, it is still possible to reconcile q with the predictions from the asymptotic formalisms, by choosing which formalism to use according to the value of q. For stars approaching the luminosity bump, the buoyancy spike becomes a glitch and strongly affects the mode frequencies. Fitting the frequencies without accounting for the glitch leads to unphysical variations in the inferred q, but we show that this is corrected when properly accounting for the glitch in the fitting. Copyright © 2022, The Authors. All rights reserved.

关键词： Buoyancy