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Physical properties and evolutionary status of the W-subtype contact binary V502 Oph with a stellar companion

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arXiv 2017年

作者： Xiao, Zhou Shengbang, Qian Binghe, Huang Hao, Li Jia, Zhang Yunnan Observatories Chinese Academy of Sciences PO Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences PO Box 110 Kunming650216 China Graduate University of the Chinese Academy of Sciences Yuquan Road 19 Sijingshang Block Beijing100049 China

Multi-color (B V Rc Ic) CCD photometric light curves of the contact binary V502 Oph are analyzed using the Wilson-Devinney (W-D) program. The solutions reveal that V502 Oph is a W-subtype contact (f = 35.3%) binary system. The temperature difference between its two components is 240K and the more massive star has a lower surface temperature. A cool spot is added in our model to account for the light curves' asymmetry (O'Connell effect) and third light is detected for the first time in the light curves' modeling. Combining the orbital inclination (i = 76.4◦) with the published mass function of V502 Oph, the absolute physical parameters of the two components are determined, which are M1 = 0.46(±0.02)M☉, M2 = 1.37(±0.02)M☉, R1 = 0.94(±0.01)R☉, R2 = 1.51(±0.01)R☉, L1 = 1.13(±0.02)L☉ and L2 = 2.49(±0.03)L☉. The formation and evolutionary status of V502 Oph are discussed. All photoelectric and CCD times of light minimum about V502 Oph are gathered and its orbital period variations are analyzed. The results show that the orbital period of V502 Oph is decreasing continuously at a rate of dP/dt = −1.69 × 10−7day · year−1, which corresponds to a conservative mass transfer rate of dMdt2 = −3.01 × 10−8M☉/year. The light-travel time effect (LTTE) is due to the presence of a close-in tertiary component with a period of P3 = 18.7 years and an amplitute of 0.00402days. V502 Oph is an ideal target to test the formation and evolution theories of binary and multiple systems in which the light curves, O − C curve and spectroscopic observations are comprehensively researched. Copyright © 2017, The Authors. All rights reserved.

关键词： Travel time

Low-mass active galactic nuclei on the fundamental plane of black hole activity

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arXiv 2017年

作者： Qian, Lei Dong, Xiao-Bo Xie, Fu-Guo Liu, Wenjuan Li, Di CAS Key Laboratory of FAST NAOC Chinese Academy of Sciences Beijing100012 China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming Yunnan650011 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China

It is widely known that in active galactic nuclei (AGNs) and black hole X-ray binaries (BHXBs), there is a tight correlation among their radio luminosity (LR), X-ray luminosity (LX) and BH mass (MBH), the so-called 'fundamental plane' (FP) of BH activity. Yet the supporting data are very limited in the MBH regime between stellar mass (i.e., BHXBs) and 106.5 M☉ (namely, the lower bound of supermassive BHs in common AGNs). In this work, we developed a new method to measure the 1.4 GHz flux directly from the images of the VLA FIRST survey, and apply it to the type-1 low-mass AGNs in the Dong et al. (2012) sample. As a result, we obtained 19 new low-mass AGNs for FP research with both MBH estimates (MBH ≈ 105.5−6.5 M☉), reliable X-ray measurements, and (candidate) radio detections, tripling the number of such candidate sources in the literature. Most (if not all) of the low-mass AGNs follow the standard radio/X-ray correlation and the universal FP relation fitted with the combined dataset of BHXBs and supermassive AGNs by Gültekin et al. (2009);the consistency in the radio/X-ray correlation slope among those accretion systems supports the picture that the accretion and ejection (jet) processes are quite similar in all accretion systems of different MBH. In view of the FP relation, we speculate that the radio loudness R (i.e., the luminosity ratio of the jet to the accretion disk) of AGNs depends not only on Eddington ratio, but probably also on MBH. Copyright © 2017, The Authors. All rights reserved.

关键词： Galaxies

Analytic properties of force-free jets in the kerr spacetime - III: Uniform field solution

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arXiv 2017年

作者： Pan, Zhen Yu, Cong Huang, Lei Department of Physics University of California One Shields Avenue DavisCA95616 United States 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 for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai200030 China

The structure of steady axisymmetric force-free magnetosphere of a Kerr black hole (BH) is governed by a second-order partial differential equation of Aφ depending on two "free" functions Ω(Aφ) and I(Aφ), where Aφ is the φ component of the vector potential of the electromagnetic field, Ω is the angular velocity of the magnetic field lines and I is the poloidal electric current. In this paper, we investigate the solution uniqueness. Taking asymptotically uniform field as an example, analytic studies imply that there are infinitely many solutions approaching uniform field at infinity, while only a unique one is found in general relativistic magnetohydrodynamic simulations. To settle down the disagreement, we reinvestigate the structure of the governing equation and numerically solve it with given constraint condition and boundary condition. We find that the constraint condition (field lines smoothly crossing the light surface (LS)) and boundary conditions at horizon and at infinity are connected via radiation conditions at horizon and at infinity, rather than being independent. With appropriate constraint condition and boundary condition, we numerically solve the governing equation and find a unique solution. Contrary to naive expectation, our numerical solution yields a discontinuity in the angular velocity of the field lines and a current sheet along the last field line crossing the event horizon. We also briefly discuss the applicability of the perturbation approach to solving the governing equation. Copyright © 2017, The Authors. All rights reserved.

关键词： Magnetohydrodynamics

Using deep Residual Networks to search for galaxy-Lyα emitter lens candidates based on spectroscopic-selection

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arXiv 2018年

作者： Li, Rui Shu, Yiping Su, Jianlin Feng, Haicheng Zhang, Guobao Wang, Jiancheng Liu, Hongtao Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 Purple Mountain Observatory Chinese Academy of Sciences 2 West Beijing Road Nanjing Jiangsu210008 China Institute of Astronomy University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom School of Mathematics Sun Yat-sen University Guangzhou China

More than one hundred galaxy-scale strong gravitational lens systems have been found by searching for the emission lines coming from galaxies with redshifts higher than the lens galaxies. Based on this spectroscopic-selection method, we introduce the deep Residual Networks (ResNet, a kind of deep Convolutional Neural Networks) to search for the galaxy-Lyα emitter (LAE) lens candidates by recognizing the Lyα emission lines coming from high redshift galaxies (2 Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

New photometric investigation of the low-mass-ratio contact binary star V1853 Orionis

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arXiv 2018年

作者： He, Jia-Jia Qian, Sheng-Bang Soonthornthum, B. Aungwerojwit, A. Liu, Niang-Ping Sarotsakulchai, T. 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 Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China National Astronomical Research Institute of Thailand 191 Siriphanich Bidg. 2nd Fl. Huay Kaew Rd. Suthep District Muang Chiang Mai50200 Thailand Department of Physics Faculty of Science Naresuan University Phitsanulok65000 Thailand

Four-color charge-coupled device (CCD) light curves in B, V, Rc and Ic bands of the total-eclipsing binary system, V1853 Ori, are presented. By comparing our light curves with those published by previous investigators, it is detected that the O’Connell effect on the light curves is disappeared. By analyzing those multi-color light curves with the Wilson-Devinney code (W-D code), it is discovered that V1853 Ori is an A-type intermediate-contact binary with a degree of contact factor of f = 33.3%(3.7%) and a mass ratio of q = 0.1896(0.0013). Combining our 10 new determined times of light minima together with the others published in the literature, the period changes of the system is investigated. We found that the general trend of the observed-calculated (O − C) curve shows a downward parabolic variation that corresponds to a long-term decrease in the orbital period with a rate of dP/dt = −1.96(0.46) × 10−7 d yr−1. The long-term period decrease could be explained by mass transfer from the more-massive component to the less-massive one. By combining our photometric solutions with the Gaia DR 2 data, absolute parameters were derived as M1 = 1.20 M☉, M2 = 0.23 M☉, R1 = 1.36 R☉, and R2 = 0.66 R☉. The long-term period decrease and the intermediate-contact configuration suggest that V1853 Ori will evolve into a high fill-out overcontact binary. Copyright © 2018, The Authors. All rights reserved.

关键词： Photometry

Contribution of primordial binary evolution to the two blue-straggler sequences in globular cluster M30

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arXiv 2017年

作者： Jiang, Dengkai Chen, Xuefei Li, Lifang Han, Zhanwen 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 Kunming650011 China

Two blue-straggler sequences discovered in globular cluster M30 provide a strong constraint on the formation mechanisms of blue stragglers. We study the formation of the blue-straggler binaries through binary evolution, and find that binary evolution can contribute to the blue stragglers in both of the sequences. Whether a blue straggler is located in the blue sequence or red sequence depends on the contribution of the mass donor to the total luminosity of the binary, which is generally observed as a single star in globular clusters. The blue stragglers in the blue sequence have a cool white-dwarf companion, while the majority (∼ 60%) of the objects in the red sequence are the binaries that are still experiencing mass transfer, but there are also some objects that the donors have just finished the mass transfer (the stripped-core stars, ∼ 10%) or the blue stragglers (the accretors) have evolved away from the blue sequence (∼ 30%). Meanwhile, W UMa contact binaries found in both sequences may be explained by various mass ratios, that is, W UMa contact binaries in the red sequence have two components with comparable masses (e.g. mass ratio q ∼ 0.3-1.0), while those in the blue sequence have low mass ratio (e.g. q Copyright © 2017, The Authors. All rights reserved.

关键词： Mass transfer

The orbital period variations of AH Virginis

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Research in Astronomy and Astrophysics 2015年第2期15卷 275-280页

作者： Ming Chen Fu-Yuan Xiang Yun-Xia Yu Ting-Yu Xiao Department of Physics Xiangtan University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences

Abstract We present a study of orbital period changes in AH Virginis. We perform a careful literature search for all available minima times, from which we derived a new linear ephemeris and constructed an O - C curve. We found that the orbital period of AH Virginis shows a long-term increase, dP/dt = （2.1869 ± 0.0161） × 10^-7 d yr^-1, and a small periodic variation with a period of 37.19 yr. Since AH Virginis is an over- contact system and the primary component shows strong Ha and Mg II emission lines, we discuss the possible connection between mass transfer, magnetic activity and or- bital period changes.

关键词： binaries: close binaries: eclipsing stars: individual (AH Virginis)

Mass retention efficiencies of He accretion onto carbon-oxygen white dwarfs and type Ia supernovae

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arXiv 2017年

作者： Wu, C. Wang, B. Liu, D. Han, Z. 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 20A Datun Road Chaoyang District Beijing100012 China

Context. Type Ia supernovae (SNe Ia) play a crucial role in studying cosmology and galactic chemical evolution. They are thought to be thermonuclear explosions of carbon-oxygen white dwarfs (CO WDs) when their masses reach the Chandrasekar mass limit in binaries. Previous studies have suggested that He novae may be progenitor candidates of SNe Ia. However, the mass retention efficiencies during He nova outbursts are still uncertain. Aims. In this article, we aim to study the mass retention efficiencies of He nova outbursts and to investigate whether SNe Ia can be produced through He nova outbursts. Methods. Using the stellar evolution code Modules for Experiments in Stellar Astrophysics, we simulated a series of multicycle He-layer flashes, in which the initial WD masses range from 0.7 to 1.35 M☉ with various accretion rates. Results. We obtained the mass retention efficiencies of He nova outbursts for various initial WD masses, which can be used in the binary population synthesis studies. In our simulations, He nova outbursts can increase the mass of the WD to the Chandrasekar mass limit and the explosive carbon burning can be triggered in the center of the WD;this suggests that He nova outbursts can produce SNe Ia. Meanwhile, the mass retention efficiencies in the present work are lower than those of previous studies, which leads to a lower birthrates of SNe Ia through the WD + He star channel. Furthermore, we obtained the elemental abundances distribution at the moment of explosive carbon burning, which can be used as the initial input parameters in studying explosion models of SNe Ia. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

Constraining the redshifts of TeV BL Lac objects

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arXiv 2017年

作者： Qin, Longhua Jiancheng, Wang Dahai, Yan Yang, Chuyuan Zunli, Yuan Zhou, Ming Yunnan Observatory Chinese Academy of Sciences Kunming Yunnan Province650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China University of Chinese Academy of Sciences Beijing China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We present a model-dependent method to estimate the redshifts of three TeV BL Lac objects (BL Lacs) through fitting their (quasi-) simultaneous multi-waveband spectral energy distributions (SEDs) by one-zone leptonic synchrotron self-Compton (SSC) model. Considering the impact of electron energy distributions (EEDs) on the results, we use three types of EEDs, such as the power-law EED with exponential cut-off (PLC), the log-parabola (PLLP) and the broken power-law (BPL) EEDs, to fit the SEDs. We also use a parameter α to describe the uncertainties of the extragalactic background light (EBL) models, as in (Abdo et al. 2010b). We then use Markov Chain Monte Carlo (MCMC) method to explore multi-dimensional parameter space and obtain the uncertainties of the model parameters based on the observational data. We apply our method to obtain the redshifts of three TeV BL Lac objects in the marginalized 68% confidence, and find that the PLC EED does not fit the SEDs. For 3C66A, the redshift is 0.14 - 0.31 and 0.16 - 0.32 in the BPL and PLLP EEDs;for PKS1424+240, the redshift is 0.55 - 0.68 and 0.55 - 0.67 in the BPL and PLLP EEDs;for PG1553+113, the redshift is 0.22 - 0.48 and 0.22 - 0.39 in the BPL and PLLP EEDs. We also estimate the redshift of PKS1424+240 in the high stage to be 0.46 - 0.67 in the PLLP EED, roughly consistent with that in the low stage. Copyright © 2017, The Authors. All rights reserved.

关键词： Markov processes