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GeV-TeV -ray energy spectral break of BL Lac objects

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Astrophysics and Space Science 2018年第9期363卷 1-7页

作者： Zhong, W. Liu, W. G. Zheng, Y. G. Department of Physics Yunnan Normal University Kunming China Yunnan Observatories Chinese Academy of Sciences Kunming China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China

In this paper, we compile the very-high-energy and high-energy spectral indices of 43 BL Lac objects from the literature. Based on a simple math model, $\Delta \Gamma_{obs}= \alpha {{{z}}}+\beta $ , we present evidence for the origin of an observed spectral break that is denoted by the difference between the observed very-high-energy and high-energy spectral indices, $\Delta \Gamma_{obs}$ . We find by linear regression analysis that $\alpha \ne 0$ and $\beta \ne 0$ . These results suggest that the extragalactic background light attenuation and the intrinsic curvature dominate on the GeV-TeV $\gamma $ -ray energy spectral break of BL Lac objects. We argue that the extragalactic background light attenuation is an exclusive explanation for the redshift evolution of the observed spectral break.

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SN 2016ije: An SN 2002es-like Type Ia Supernova Exploded in a Metal-poor and Low-surface Brightness Galaxy

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arXiv 2023年

作者： Li, Zhitong Zhang, Tianmeng Wang, Xiaofeng Zhang, Jujia Galbany, Lluís Filippenko, Alexei V. Brink, Thomas G. Ashall, Chris Zheng, WeiKang de Jaeger, Thomas Ragosta, Fabio Deckers, Maxime Gromadzki, Mariusz Young, D.R. Xi, Gaobo Chen, Juncheng Zhao, Xulin Sai, Hanna Yan, Shengyu Xiang, Danfeng Chen, Zhihao Li, Wenxiong Wang, Bo Zou, Hu Sui, Jipeng Wang, Jiali Ma, Jun Nie, Jundan Xue, Suijian Zhou, Xu Zhou, Zhimin Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Beijing100101 China Tsinghua University Beijing100084 China Beijing Planetarium Beijing Academy of Science and Technology Beijing100044 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 Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain BarcelonaE-08034 Spain Department of Astronomy University of California BerkeleyCA94720-3411 United States Department of Physics Virginia Tech 850 West Campus Drive BlacksburgVA24061 United States Institute for Astronomy University of Hawaii 2680 Woodlawn Drive HonoluluHI96822 United States INAF – Osservatorio Astronomico di Roma via di Frascati 33 Monte Porzio Catone RomaI-00078 Italy School of Physics Trinity College Dublin The University of Dublin Dublin 2 Ireland Astronomical Observatory University of Warsaw Al. Ujazdowskie 4 Warszawa00-478 Poland Astrophysics Research Centre School of Mathematics and Physics Queen’s University Belfast BelfastBT7 1NN United Kingdom Wu Zhou University Wuzhou543002 China Department of Physics Tianjin University of Technology Tianjin300384 China The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel

We have conducted photometric and spectroscopic observations of the peculiar Type Ia supernova (SN Ia) 2016ije that was discovered through the Tsinghua-NAOC Transient Survey. This peculiar object exploded in the outskirts of a metal-poor, low-surface brightness galaxy (i.e., Mg = −14.5 mag). Our photometric analysis reveals that SN 2016ije is subluminous (MB,max = −17.65±0.06 mag) but exhibits relatively broad light curves (∆m15(B) = 1.35±0.14 mag), similar to the behavior of SN 2002es. Our analysis of the bolometric light curve indicates that only 0.14±0.04 Mo of 56Ni was synthesized in the explosion of SN 2016ije, which suggests a less energetic thermonuclear explosion when compared to normal SNe Ia, and this left a considerable amount of unburned materials in the ejecta. Spectroscopically, SN 2016ije resembles other SN 2002es-like SNe Ia, except that the ejecta velocity inferred from its carbon absorption line (∼ 4500 km s−1) is much lower than that from silicon lines (∼ 8300 km s−1) at around the maximum light. Additionally, most of the absorption lines are broader than other 02es-like SNe Ia. These peculiarities suggest the presence of significant unburned carbon in the inner region and a wide line-forming region along the line of sight. These characteristics suggest that SN 2016ije might originate from the violent merger of a white dwarf binary system, when viewed near an orientation along the iron-group-element cavity caused by the companion star. © 2023, CC BY.

关键词： Supernovae

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

The environmental dependence of Spitzer dusty Supernovae

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arXiv 2023年

作者： Xiao, Lin Szalai, Tamás Galbany, Lluís Fox, Ori Hu, Lei Hu, Maokai Yang, Yi Moriya, Takashi J. Pessi, Thallis Han, Zhanwen Wang, Xiaofeng Yan, Shengyu Department of Physics Hebei University Baoding071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding071002 China Department of Experimental Physics Institute of Physics University of Szeged Dóm tér 9 SzegedH-6720 Hungary HUN-REN–SZTE Stellar Astrophysics Research Group H-6500 BajaSzegedi út Kt. 766 Hungary Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain BarcelonaE-08034 Spain Space Telescope Science Institute 3700 San Martin Drive BaltimoreMD21218 United States McWilliams Center for Cosmology Department of Physics Carnegie Mellon University 5000 Forbes Ave PittsburghPA15213 United States Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China Tsinghua University Beijing100084 China Department of Astronomy University of California BerkeleyCA94720-3411 United States National Astronomical Observatory of Japan National Institutes of Natural Sciences 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Graduate Institute for Advanced Studies SOKENDAI 2-21-1 Osawa Mitaka Tokyo181-8588 Japan School of Physics and Astronomy Monash University ClaytonVIC3800 Australia Instituto de Estudios Astrofísicos Facultad de Ingeniería y Ciencias Universidad Diego Portales Av. Ejército Libertador 441 Santiago Chile Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Beijing Planetarium Beijing Academy of Science and Technology Beijing100044 China

Thanks to the mid-infrared capability offered by Spitzer, systematic searches of dust in SNe have been carried out over the past decade. Studies have revealed the presence of a substantial amount of dust over a broad range of SN subtypes. How normal SNe present mid-IR excess at later time and turn out to be dusty SNe can be affected by several factors, such as mass-loss history and envelope structure of progenitors and their explosion environment. All these can be combined and related to their environmental properties. A systematic analysis of SNe that exploded under a dusty environment could be of critical importance to measure the properties of the dust-veiled exploding stars, and whether such an intense dust production process is associated with the local environment. In this work, we firstly use the IFS data to study the environmental properties of dusty SNe compared to those of normal ones, and analyze correlations between the environmental properties and their dust parameters. We find that dusty SNe have a larger proportion located at higher SFR regions compared to the normal types. The occurrence of dusty SNe is less dependent on metallicity, with the oxygen abundance spanning from subsolar to oversolar metallicity. We also find the host extinction of dusty SNe scatters a lot, with about 40% of dusty SN located at extremely low extinction environments, and another 30% of them with considerably high host extinction of E(B-V)>0.6 mag. Copyright © 2023, The Authors. All rights reserved.

关键词： Supernovae

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

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

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）

Measuring clock jumps using pulsar timing

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arXiv 2019年

作者： Li, Zhi Xuan Lee, Ke Jia Caballero, Ricardo Nicolaos Xu, Yong Hua Hao, Long Fei Wang, Min Wang, Jian Cheng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China University of Chinese Academy of Sciences 19A Yuquan Road Shijingshan District Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

In this paper, we investigate the statistical signal-processing algorithm to measure the instant local clock jump from the timing data of multiple pulsars. Our algorithm is based on the framework of Bayesian statistics. In order to make the Bayesian algorithm applicable with limited computational resources, we dedicated our efforts to the analytic marginalization of irrelevant parameters. We found that the widely used parameter for pulsar timing systematics, the 'Efac' parameter, can be analytically marginalized. This reduces the Gaussian likelihood to a function very similar to the Student's t-distribution. Our iterative method to solve the maximum likelihood estimator is also explained in the paper. Using pulsar timing data from the Yunnan Kunming 40m radio telescope, we demonstrate the application of the method, where 80-ns level precision for the clock jump can be achieved. Such a precision is comparable to that of current commercial time transferring service using satellites. We expect that the current method could help developing the autonomous pulsar time scale. Copyright © 2019, The Authors. All rights reserved.

关键词： Pulsars