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Exploring the origin of multiwavelength activities of high-redshift FSRQ PKS 1502+106 during 2014–2018

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arXiv 2019年

作者： Ding, N. Gu, Q.S. Geng, X.F. Xiong, Ding-Rong Xue, R. Wang, X.Y. Guo, X.T. School of Astronomy and Space Science Nanjing University Nanjing Jiangsu210093 China Ministry of Education Nanjing210093 China Department of Physics Yunnan University Kunming650091 China Key Laboratory of Astroparticle Physics Yunnan Province Kunming650091 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

The origin of the multi-band activities (outbursts/flares) of blazars is still a heavily debated topic. Shock and magnetic reconnection have long been considered as possible triggers for the multi-band activities. In this paper, we present an exploration of the origin of multi-band activities for a high-redshift (z =1.8385) FSRQ PKS 1502+106. Utilizing multi-band data from radio to γ-ray and optical polarization observations, we investigate two dramatic activities in detail: a γ-ray dominated outburst in 2015 and an optical dominated outburst in 2017. Our main results are as follows. (I) A fast γ-ray flare with a flux-doubling time-scale as short as 1-hr in 2015 is discovered. Based on the variability time-scale, the physical parameters of the flaring region (e.g, minimum Doppler factor, emission region size, etc.) are constrained. At the peak of the flare, the γ-ray spectrum hardens to Γγ = 1.82 ± 0.04 and exhibits an obvious curvature/break characteristic that is caused by the typical "cooling break". Modelings of multi-band SEDs reveal a very hard electronic energy spectrum with the electronic spectral index of 1.07 ± 0.53. This result suggests that this fast γ-ray flare may be triggered by magnetic reconnection. (II) During the outburst in 2017, the optical polarization degree and optical fluxes show a very tight correlation. By analyzing Stokes parameters of polarization observations, our results show that this outburst could be triggered by a transverse shock with a compression ratio of η > 2.2, and the magnetic field intensity of the shock emission region is about 0.032 G. Copyright © 2019, The Authors. All rights reserved.

关键词： Galaxies

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

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

Spectroscopic properties of the dwarf nova-type cataclysmic variables observed by LAMOST

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arXiv 2020年

作者： Zhongtao, Han Soonthornthum, Boonrucksar Shengbang, Qian Xiaohui, Fang Qishan, Wang Liying, Zhu Aijun, Dong Qijun, Zhi P. O. Box 110 Kunming650216 China National Astronomical Research Institute of Thailand Higher Education Science Research and Innovation 260 Moo 4 T. Donkaew A. MaerimChiangmai50180 Thailand Guizhou Provincial Key Laboratory of Radio Data Processing School of Physics and Electronic Sciences Guizhou Education University Guiyang550001 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 University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China

Spectra of 76 known dwarf novae from the LAMOST survey were presented. Most of the objects were observed in quiescence, and about 16 systems have typical outburst spectra. 36 of these systems were observed by SDSS, and most of their spectra are similar to the SDSS spectra. 2 objects, V367 Peg and V537 Peg, are the first to observe their spectra. The spectrum of V367 Peg shows a contribution from a M-type donor and its spectral type could be estimated as M3-5 by combining its orbital period. The signature of white dwarf spectrum can be seen clearly in four low-accretion-rate WZ Sge stars. Other special spectral features worthy of further observations are also noted and discussed. We present a LAMOST spectral atlas of outbursting dwarf novae. 6 objects have the first outburst spectra, and the others were also compared with the published outburst spectra. We argue that these data will be useful for further investigation of the accretion disc properties. The HeII λ4686 emission line can be found in the outburst spectra of seven dwarf novae. These objects are excellent candidates for probing the spiral asymmetries of accretion disc. Copyright © 2020, The Authors. All rights reserved.

关键词： White dwarfs

XMM-Newton and NICER measurement of the rms spectrum of the millihertz quasi-periodic oscillations in the neutron-star low-mass X-ray binary 4U 1636−53

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arXiv 2020年

作者： Lyu, Ming Zhang, Guobao Méndez, Mariano Altamirano, D. Mancuso, G.C. Xiang, Fu-Yuan Xiao, Huaping Department of Physics Xiangtan University Xiangtan Hunan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Xiangtan Hunan411105 China Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Kapteyn Astronomical Institute University of Groningen PO BOX 800 GroningenNL-9700 AV Netherlands Physics & Astronomy University of Southampton SouthamptonHampshireSO17 1BJ United Kingdom C.C. No. 5 Villa Elisa1894 Argentina Facultad de Ciencias Astronómicas y Geofísicas Universidad Nacional de La Plata Paseo del Bosque s/n La Plata1900 Argentina

We used two XMM-Newton and six Neutron Star Interior Composition Explorer (NICER) observations to investigate the fractional rms amplitude of the millihertz quasi-periodic oscillations (mHz QPOs) in the neutron-star low-mass X-ray binary 4U 1636–53. We studied, for the first time, the fractional rms amplitude of the mHz QPOs vs. energy in 4U 1636–53 down to 0.2 keV. We find that, as the energy increases from ∼0.2 keV to ∼3 keV, the rms amplitude of the mHz QPOs increases, different from the decreasing trend that has been previously observed above 3 keV. This finding has not yet been predicted by any current theoretical model, however, it provides an important observational feature to speculate whether a newly discovered mHz oscillation originates from the marginally stable nuclear burning process on the neutron star surface. Copyright © 2020, The Authors. All rights reserved.

关键词： Stars

A compact X-Ray emitting binary in likely association with 4FGL J0935.3+0901

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arXiv 2020年

作者： Wang, Zhongxiang Xing, Yi Zhang, Jujia Boutsia, Konstantina Wang, Gege Jithesh, V. Burdge, Kevin B. Coughlin, Michael W. Duev, Dmitry A. Kulkarni, S.R. Riddle, Reed Serabyn, Eugene Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 Las Campanas Observatory Carnegie Observatories Casilla 601 La Serena Inter-University Centre for Astronomy Astrophysics Pune411007 India Caltech Optical Observatories California Institute of Technology PasadenaCA91125 United States Division of Physics Math and Astronomy California Institute of Technology PasadenaCA91125 United States Jet Propulsion Laboratory California Institute of Technology PasadenaCA91109 United States

4FGL J0935.3+0901 is a --ray source detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope. We have conducted detailed analysis of the LAT data for this source and multi-wavelength studies of the source field. Its --ray emission can be described with a power law (2.0 ± 0.2) with an exponential cutoff (Ec = 2.9±1.6 GeV), while the flux shows significant long-term variations. From analysis of archival Neil Gehrels Swift X-ray Telescope data, we find only one X- ray source in the LAT's 2- error region. Within a 37 radius error circle of the X-ray source, there is only one optical object down to r 23 mag. Time-resolved photometry of the optical object indicates a likely 2.5 hr periodic modulation, while its spectrum shows double-peaked hydrogen and helium emission lines (similar to those seen in accretion discs in low-mass X-ray binaries). Combining these results, we conclude that we have discovered a compact X-ray emitting binary in likely association with 4FGL J0935.3+0901, i.e., a millisecond pulsar (MSP) binary. We discuss the implication of the optical spectral features: this binary could be a transitional MSP system at a sub- luminous disc state, although the other possibility, the binary in a rotation-powered state showing the optical emission lines due to intrabinary interaction processes, can not be excluded. Further observational studies will help determine detailed properties of this candidate MSP binary and thus clarify its current state. Copyright © 2020, The Authors. All rights reserved.

关键词： Electromagnetic wave emission

Hot subdwarf B stars with neutron star components II: Binary population synthesis

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arXiv 2019年

作者： Wu, You Chen, Xuefei Chen, Hailiang Li, Zhenwei Han, Zhanwen 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 the Chinese Academy of Science Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

Context. Subdwarf B stars (sdBs) play a crucial role in stellar evolution, asteroseismology, and far-UV radiation of early-type galaxies, and have been intensively studied with observation and theory. It has theoretically been predicted that sdBs with neutron star (NS) companions exist in the Galaxy, but none have been discovered yet. This remains a puzzle in this field. In a previous study (hereafter Paper I), we have studied the formation channels of sdB+NS binaries from main-sequence (MS) stars plus NS binaries by establishing a model grid, but it is still unclear how these binaries consisting of MS stars and NS binaries came to be in the first place. Aims. We systematically study the formation of sdB+NS binaries from their original zero-age main-sequence progenitors. We bridge the gap left by our previous study in this way. We obtain the statistical population properties of sdB+NS binaries and provide some guidance for observational efforts. Methods. We first used Hurley’s rapid binary evolution code BSE to evolve 107 primordial binaries to the point where the companions of NS+MS, NS+Hertzsprung gap (HG) star, and NS+Giant Branch (GB) star binaries have just filled their Roche lobes. Next, we injected these binaries into the model grid we developed in Paper I to obtain the properties of the sdB+NS populations. We adopted two prescriptions of NS natal kicks: the classical Maxwellian distribution with a dispersion of σ = 265kms−1, and a linear formula that assumes that the kick velocity is associated with the ratio of ejected to remnant mass. Different values of αCE, where αCE is the common-envelope ejection efficiency, were chosen to examine the effect of common-envelope evolution on the results. Results. In the Galaxy, the birthrate of sdB+NS binaries is about 10−4yr−1 and there are ∼ 7000−21000 such binaries. This contributes 0.3-0.5% of all sdB binaries in the most favorable case. Most Galactic sdB+NS binaries (& 60%) arise from the channel of stable mass tran

关键词： Neutrons

Three new late-type hypervelocity star candidates from gaia DR2 by refined selection criteria

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arXiv 2020年

作者： Li, Jiao Jia, Shi Gao, Yan Jiang, Dengkai Kupfer, Thomas Heber, Ulrich Liu, Chao Chen, Xuefei Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China State Key Laboratory of Lunar and Planetary Sciences Macau University of Science and Technology Macau China Kavli Institute for Theoretical Physics University of California Santa BarbaraCA93106 United States Department of Physics University of California Santa BarbaraCA93106 United States Dr. Remeis-Sternwarte and Ecap University of Erlangen-Nürnberg Erlangen Key Lab of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

Several dozen hypervelocity star (HVS) candidates have been reported based on the second data release of Gaia (Gaia DR2). However, it has been proven that the radial velocities of some Gaia HVS candidates are not reliable. In this paper, we employ refined astrometric criteria to re-examine Gaia DR2, arriving at a more reliable sample of HVS and high velocity star candidates than those found by previous authors. We develop a method called Binary Escape Probability Analysis to identify some HVS candidates. This method allows us to work with stars having only two epochs of measured radial velocity. These stars were usually discarded in previous similar studies. A scrutiny of our final results sheds light on selection effects present in our studies, which we propose to be the focus of future studies. In total, we find three late-type (2 G-type and 1 K-type) HVS and 21 high velocity star candidates, 3 and 11 of which are new, respectively. Judging by their historical trajectories, which we calculate, all three HVS candidates could not have had Galactic centre origins. Copyright © 2020, The Authors. All rights reserved.

关键词： Stars