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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

Comprehensive Photometric Investigation of an Active Early K-type Contact System – IL Cnc

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arXiv 2020年

作者： Liu, N.-P. Sarotsakulchai, T. Rattanasoon, S. Zhang, B. Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China National Astronomical Research Institute of Thailand 260 Moo 4 T.Donkaew A.MaerimChiangmai50180 Thailand Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Shijingshan Block Beijing100049 China Department of Physics and Astronomy University of Shelffield Hounsfield Road SheffieldS3 7RH United Kingdom Guizhou Normal University Guiyang550001 China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guiyang550001 China

Comprehensive photometric investigation was carried out to the early K-type contact binary - IL Cnc. A few light curves from both ground-based telescopes and the Kepler space telescope were obtained (or downloaded) and then analyzed in detail. They are mostly found to be asymmetric and there are even continuously changing O’Connell effect in the light curves from Kepler K2 data, suggesting the system to be highly active. Using the Wilson-Devinney code (version 2013), photometric solutions were derived and then compared. It is found that the calculation of the mass ratio is easily affected by the spot settings. Combining the radial velocities determined from LAMOST median resolution spectral data, the mass ratio of the binary components is found to be M2/M1 = 1.76±0.05. The components are in shallow contact (f ∼ 9%) and have a temperature difference about T2 − T1 = −280 ± 20 K. The system is demonstrated to be W-subtype, which may be a common feature of K-type contact binaries. The masses of the binary components were estimated to be M1 ∼ 0.51 M and M2 ∼ 0.90 M. The values are in good agreement with that deduced from the parallax data of Gaia. The results suggest that the primary component lacks luminosity compared with the zero main sequence. The Hα spectral line of the primary component is found to be peculiar. Combining newly determined minimum light times with those collected from literature, the orbital period of IL Cnc is studied. It is found that the (O−C)s of the primary minima show sinusoidal variation while the secondary do not. The oscillation is more likely to be caused by the starspot activities. Yet this assumption needs more data to support. Copyright © 2020, The Authors. All rights reserved.

关键词： Photometry

Statistical analysis on X-ray flares from the nucleus and HST-1 knot in the M87 jet

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arXiv 2019年

作者： Yang, Shenbang Yan, Dahai Dai, Benzhong Zhang, Pengfei Zhu, Qianqian Wang, Jiancheng Zhang, Li Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Department of General Studies Nanchang Institute of Science & Technology Nanchang330108 China

The statistical properties of X-ray flares from two separate locations (nucleus and HST-1) in the M87 jet are investigated to reveal the physical origin of the flares. We analyse the archival Chandra data for M87, and identify 14 flares in the nucleus and 9 flares in HST-1. The peak intensity (IP) and the flaring duration time (Tfl) for each flare are obtained. It is found that the distributions of both IP and Tfl for the nucleus obey a power-law form with a similar index. A similar result is also obtained for HST-1, and no significant inconsistency between the nucleus and HST-1 is found for the indices. Similar to solar X-ray flares, the power-law distributions of the flare event parameters can be well explained by a self-organized criticality (SOC) system, which are triggered by magnetic reconnection. Our results suggest that the flares from nucleus and HST-1 are possibly triggered by magnetic reconnection process. The consistent indices for the distributions of IP and Tfl in the CORE and HST-1 indicate that the dimensions of the energy dissipation of the magnetic reconnection is identical in the two regions. A strong correlation between the flares in the two regions also suggests a similar physical origin for the flares. Copyright © 2019, The Authors. All rights reserved.

关键词： Energy dissipation

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

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

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

The photometric monitoring of γ-ray-loud narrow-line Seyfert 1 galaxy 1H0323+342 from 2006 to 2010

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Research in Astronomy and Astrophysics 2017年第7期17卷 47-56页

作者： Fang Wang Ding-Rong Xiong Jin-Ming Bai Shao-Kun Li Jian-Guo Wang Yunnan Observatories Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Center for Astronomical Mega-Science Chinese Academy of Sciences

1H 0323＋342 is a γ-ray-loud narrow-line Seyfert 1 galaxy（NLS1）. The variability mechanism of γ-ray-loud NLS1 s remains unclear. We have observed 1H 0323＋342 photometrically from 2006 to2010 with a total of 41 nights of observations in order to constrain the variability mechanism. Intraday variabilities（IDVs） are detected on four nights. When considering the nights with time spans 〉 2 hours,the duty cycle is 28.3%. The average variability amplitude is 10.8% for IDVs and possibly variable nights. In the color-magnitude diagram, there are bluer-when-brighter chromatic trends for intraday and long-term timescales, which could be explained by the shock-in-jet model, and also could possibly be due to two distinct components or an accretion disk model.

关键词： galaxies active - galaxies individual （1H 0323＋342）- galaxies jets

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

Optical flare events on the RS Canum Venaticorum star UX Arietis

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Research in Astronomy and Astrophysics 2017年第6期17卷 55-66页

作者： Dong-Tao Cao Sheng-Hong Gu Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China

Based on long-term high-resolution spectroscopic observations obtained during five observing runs from 2001 to 2004, we study optical flare events and chromospheric activity variability of the very active RS CVn star UX Ari. By means of the spectral subtraction technique, several optical chromospheric activity indicators （including the He IDa, Na I D1, D2 doublet, Ha and Ca II IRT lines） covered in our echelle spectra were analyzed. Four large optical flare events were detected on UX Ari during our observations, which show prominent He I D3 line emission together with great enhancement in emission of the Ha and Ca II IRT lines and strong filled-in or emission reversal features in the Na ! D1, D2 doublet lines. The newly detected flares are much more energetic than previous discoveries, especially for the flare identified during the 2002 December observing run. Optical flare events on UX Ari are more likely to be observed around two quadratures of the system, except for our optical flares detected during the 2004 November observing run. Moreover, we have found rotational modulation of chromospheric activity in the Ha and Ca II IRT lines, which suggests the presence of chromospherically active longitudes over the surface of UX Ari. The change in chromospherically active longitudes among our observing runs, as well as the variation in chromospheric activity level from 2001 to 2004, indicates a long-term evolution of active regions.

关键词： stars activity - stars chromospheres - stars binaries spectroscopic -stars flare -stars individual （UX Ari）