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Evolving neutron star+helium star systems to intermediate-mass binary pulsars

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arXiv 2019年

作者： Tang, W. Liu, D. Wang, B. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Intermediate-mass binary pulsars (IMBPs) are composed of neutron stars (NSs) and CO/ONe white dwarfs (WDs). It is generally suggested that IMBPs evolve from intermediate-mass X-ray binaries (IMXBs). However, this scenario is difficult to explain the formation of IMBPs with orbital periods (Porb) less than 3 d. It has recently been proposed that a system consisting of a neutron star (NS) and a helium (He) star can form IMBPs with Porbless than 3 d (known as the NS+He star scenario), but previous works can only cover a few observed sources with short orbital periods. We aim to investigate the NS+He star scenario by adopting different descriptions of the Eddington accretion rate ( MEdd) for NSs and different NS masses (MNS) varying from 1.10Moto 1.80Mo. Our results can cover most of the observed IMBPs with short orbital periods and almost half of the observed IMBPs with long orbital periods. We found that MEdd∝MNS-1/3could match the observations better than a specific value for all NSs. We also found that the final spin periods of NSs slightly decrease with the initial MNS. The observed parameters of PSR J0621+1002, which is one of the well-observed IMBPs whose pulsar mass has been precisely measured, can be reproduced by the present work. Copyright © 2019, The Authors. All rights reserved.

关键词： White dwarfs

Hot subdwarf stars observed in Gaia DR2 and LAMOST DR5

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arXiv 2019年

作者： Luo, Yangping Németh, Péter Deng, Licai Han, Zhanwen Department of Astronomy China West Normal University Nanchong637002 China Astronomical Institute Czech Academy of Sciences CZ-25 165 Ondrejov Czech Republic *** Malomsok8533 Hungary Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

Combing Gaia DR2 with LAMOST DR5, we spectroscopically identified 924 hot subdwarf stars, among which 32 stars exhibit strong double-lined composite spectra. We measured the effective temperature Teff, surface gravity log g, helium abundance y = nHe/nH, and radial velocities of 892 non-composite spectra hot subdwarf stars by fitting LAMOST observations with Tlusty/Synspec non-LTE synthetic spectra. We outlined four different groups in the Teff − log g diagram with our helium abundance classification scheme and two nearly parallel sequences in the Teff −log(y) diagram. 3D Galactic space motions and orbits of 747 hot subdwarf stars with (GBP − GRP)0 z−eccentricity diagram, and Galactic orbits, we derived Galactic population classifications and the fractional distributions of the four hot subdwarf helium groups in the halo, thin disk and thick disk. Comparisons with the predictions of binary population synthesis calculations (Han 2008) suggest that He-rich hot subdwarf stars with log(y) ≥ 0 are from the double helium white dwarfs merger, He-deficient hot subdwarf stars with −2.2 ≤ log(y) Copyright © 2019, The Authors. All rights reserved.

关键词： White dwarfs

Optical Continuum Reverberation Mapping of a Candidate IMBH in a Nearby Seyfert 1 Galaxy

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arXiv 2024年

作者： Zuo, Wenwen Guo, Hengxiao Sun, Jingbo Yuan, Qi Lira, Paulina Gu, Minfeng Edwards, Philip G. Gupta, Alok C. Kishore, Shubham Stevens, Jamie An, Tao Cai, Zhen-Yi Feng, Hai-Cheng Ho, Luis C. Ilić, Dragana Kovačević, Andjelka B. Li, Sha-Sha Mezcua, Mar Popović, Luka Č. Sun, Mouyuan Tripathi, Tushar Vivian, U. Vince, Oliver Wang, Jianguo Wang, Junxian Wang, Shu Wu, Xuebing Zheng, Zhenya Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China University of Chinese Academy of Sciences 19A Yuquan Road Beijing100049 China Changchun Observatory National Astronomical Observatories Chinese Academy of Sciences West Hill of Jingyue Lake Changchun130117 China Departamento de Astronom Universidad de Chile Casilla Santiago Chile36D Chile CSIRO Astronomy and Space Science PO Box 76 EppingNSW1710 Australia Manora Peak Nainital263001 India Department of Physics DDU Gorakhpur University Gorakhpur273009 India CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Anhui Hefei230026 China School of Astronomy and Space Science University of Science and Technology of China Hefei230026 China 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 Department of Astronomy School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China University of Belgrade Faculty of Mathematics Department of Astronomy Studentski trg 16 Belgrade Serbia Hamburger Sternwarte Universitat Hamburg Gojenbergsweg 112 HamburgD-21029 Germany Campus UAB Carrer de Magrans Barcelona08193 Spain Edifici RDIT Campus UPC Castelldefels Barcelona08860 Spain Astronomical Observatory Volgina 7 Belgrade11060 Serbia Department of Astronomy Xiamen University Fujian Xiamen361005 China Department of Physics and Astronomy University of California 4129 Frederick Reines Hall IrvineCA92697-4575 United States Department of Physics & Astronomy Seoul National University Seoul08826

To investigate the short-term variability and determine the size of the optical continuum emitting region of intermediate-mass black holes (IMBHs), we carried out high-cadence, multiband photometric monitoring of a Seyfert 1 galaxy J0249−0815 across two nights, together with a one-night single-band preliminary test. The presence of the broad Hα component in our target was confirmed by recent Palomar/P200 spectroscopic observations, 23 yr after the Sloan Digital Sky Survey, ruling out the supernovae origin of the broad Hα line. The photometric experiment was primarily conducted utilizing four-channel imagers MuSCAT 3 and 4 mounted on 2 m telescopes within the Las Cumbres Observatory Global Telescope Network. Despite the expectation of variability, we observed no significant variation ( Copyright © 2024, The Authors. All rights reserved.

关键词： Reverberation

Case AD, AR, and AS binary evolution and their possible connections with W UMa binaries

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arXiv 2019年

作者： Jiang, Dengkai 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

Close detached binaries were theoretically predicted to evolve into contact by three subtypes of case A binary evolution: case AD, AR, and AS, which correspond to the formation of contact during dynamic-, thermal-, and nuclear-timescale mass transfer phase, respectively. It is unclear, however, what is the difference between contact binaries in these subtypes, and whether all of these subtypes can account for the formation of observed W UMa binaries. Using Eggleton’s stellar evolution code with the nonconservative assumption, I obtained the low-mass contact binaries produced by case AD, AR, and AS at the moment of contact, and their parameter spaces. The results support that the progenitors of low-mass contact binaries are detached binaries with orbital periods shorter than ∼ 2 − 5 d, and their borderlines depend strongly on the primary mass. In addition, the period-colour relations for case AR and AS can be in better agreement with that for observed W UMa candidates, but case AD shows a significantly worse agreement. Moreover, case AR and AS can produce a short-period limit (corresponding to a low-mass limit) at almost any age, e.g. from young age (∼ 0.2 Gyr) to old age (∼ 13 Gyr), agreeing with observed W UMa binaries in star clusters, but no such limit occurs for case AD at any age. These results support that case AR and AS, as opposed to case AD, can lead to W UMa binaries (including young W UMa binaries). Copyright © 2019, The Authors. All rights reserved.

关键词： Mass transfer

Astrometry and Spectra Classification of Near Earth Asteroids with Lijiang 2.4m Telescope

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Proceedings of the International Astronomical Union 2018年第S330期12卷 413-414页

作者： X. L. Zhang B. Yang J. M. Bai Yunnan Observatories Chinese Academy of Sciences Kunming 650011 China email: zhangxiliang@*** Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

The Lijiang 2.4m telescope of Yunnan Observatories is located at longitude E100°01′51″, latitude N26°42′32″ and height 3250m above sea level (IAU code O44). Because of low latitude of the site, long-focus system and planetary tracking mode of telescope, high accuracy positioning and spectral classification of the near Earth objects (NEAs) especially in the Southern Hemisphere can be studied with the Lijiang 2.4m telescope. As a set of observational campaigns organized by the GAIA-FUN-SSO, astrometry of several near Earth asteroids including (367943) Duende and (99942) Apophis were made with Lijiang 2.4m telescope during 2013. From December 12, 2015, spectra of three near earth asteroids were also observed with the YFOSC terminal attached to the Lijiang 2.4m telescope. This paper will give the detailed introduction of Lijiaing 2.4m telescope and observational results of near Earth asteroids obtained with it.

关键词： methods: observational techniques: astrometry spectrum classification

Particle accleration and synchrotron self-compton emission in blazar jets I: An application to the quiescent emission

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arXiv 2019年

作者： Zheng, Y.G. Kang, S.J. Yang, C.Y. Bai, J.M. Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Department of Physics Yunnan Normal University Kunming650092 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial EnvironmentShandong University Weihai264209 China School of Electrical Engineering Liupanshui Normal University Liupanshui Guizhou553004 China

There are still some important unanswered questions about the detailed particle acceleration and escape occurring during the quiescent epoches. As a result, the particle distribution that is adopted in the blazar quiescent spectral model have numerous unconstrained shapes. To help remedy this problem, we introduce a analytical particle transport model to reproduce quiescent broadband spectral energy distribution of blazar. In this model, the exact electron distribution is solved from a generalized transport equation that contains the terms describing first-order and secondary-order Fermi acceleration, escape of particle due to both the advection and spatial diffusion, energy losses due to synchrotron emission and inverse-Compton scattering of an assumed soft photon field. We suggest that the advection is a significant escape mechanism in blazar jet. We find that in our model the advection process tends to harden the particle distribution, which enhances the high energy components of resulting synchrotron and synchrotron self-Comptom spectrum from jet. Our model is able to roughly reproduce the observed spectra of extreme BL Lac object 1ES 0414+009 with reasonable assumptions about the physical parameters. Copyright © 2019, The Authors. All rights reserved.

关键词： Energy dissipation

R-band host galaxy contamination of TeV γ-ray blazar Mrk 501： effects of aperture size and seeing

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Research in Astronomy and Astrophysics 2018年第2期18卷 93-104页

作者： Hai-Cheng Feng Hong-Tao Liu Ying-He Zhao Jin-Ming Bai Fang Wang Xu-Liang Fan Yunnan Observatories Chinese Academy of Sciences Kunming 650216 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 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China School of Physics and Space Science China West Normal University Nanchong 637009 China School of Physics Huazhong University of Science and Technology Wuhan 430074 China

We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale microvariability. The pure nuclear flux is -8.0 mJy in the R band, i.e., the AGN has a magnitude of R - 13.96 mag.

关键词： galaxies： active - BL Lacertae objects： individual （Mrk 501） - techniques： photometric-- methods： data analysis

Simulating kilonovae in the ΛCDM universe

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arXiv 2020年

作者： Jiang, Zhen Wang, Jie Zhang, Fenghui Li, Li-Xin Wang, Lan Li, Ran Gao, Liang Han, Zhanwen Pan, Jun Key Laboratory for Computational Astrophysics National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Institute of Computational Cosmology Department of Physics University of Durham South Road DurhamDH1 3LE United Kingdom

Kilonovae are optical flashes produced in the aftermath of neutron star-neutron star mergers (NNMs) or neutron star-black hole mergers (NBMs). The multi-messager observation of the recent gravitational wave event GW170817 confirms that it originated from a NNM and triggered a kilonova. In this work, we use the Millennium Simulation, combined with a semi-analytic galaxy formation model-GABE (Galaxy Assembly with Binary evolution) which adopts binary stellar population synthesis models, to explore the cosmic event rate of kilonovae, and the properties of their host galaxies in a cosmological context. We find that model with supernova kick velocity of Vkick = 0 km s−1 fits the observation best, in agreement with the exception of some formation channels of binary neutron star. This indicates that NNMs prefer to originate from binary systems with low kick velocities. With Vkick = 0 km s−1, the cosmic event rate of NNMs and NBMs at z = 0 are 283 Gpc−3 yr−1 and 91 Gpc−3 yr−1, respectively, marginally consistent with the constraint from LVC GWTC-1. For Milky Way-mass galaxies, we predict the NNM rate is 25.7−+759.1.6 Myr−1, which is also in good agreement with the observed properties of binary neutron stars in the Milky Way. Taking all the NNMs into account in the history of Milky Way-mass galaxies, we find that the averaged r-process elements yield with A > 79 in a NNM and NBM event should be 0.01 M☉ to be consistent with observation. We conclude that NGC 4993, the host galaxy of GW170817, is a typical host galaxy for NNMs. However, generally NNMs and NBMs tend to reside in young, blue, star-forming, late-type galaxies, with stellar mass and gaseous metallicity distribution peaking at M∗ = 1010.65 M☉ and 12 + log (O/H) = 8.72 − 8.85, respectively. By studying kilonovae host galaxies in the cosmological background, it is promising to constrain model details better when we have more events in the forthcoming future. Copyright © 2020, The Authors. All rights reserved.

关键词： Nucleosynthesis

Using the Extragalactic Gamma-Ray Background to Constrain the Hubble Constant and Matter Density of the Universe

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arXiv 2019年

作者： Zeng, Houdun Yan, Dahai Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China

The attenuation produced by extragalactic background light (EBL) in γ-ray spectra of blazars has been used to constrain the Hubble constant (H0) and matter density (Ωm) of the Universe. We propose to estimate H0 and Ωm using the well measured >10 GeV extragalactic γ-ray background (EGB). This suggestion is based on the facts that the >10 GeV EGB is totally explained by the emissions from blazars, and an EBL-absorption cutoff occurs at ∼50 GeV in the EGB spectrum. We fit the >10 GeV EGB data with modeled EGB spectrum. This results in H0 = 64.9+4−4..63 km s−1 Mpc−1 and Ωm = 0.31−+00..1314. Note that the uncertainties may be underestimated due to the limit of our realization for EBL model. H0 and Ωm are degenerate in our method. Independent determination of Ωm by other methods would improve the constraint on H0. Copyright © 2019, The Authors. All rights reserved.

关键词： Gamma rays