检索结果-内蒙古大学图书馆

TY Pup: a low-mass-ratio and deep contact binary as a progenitor candidate of luminous red novae

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Sarotsakulchai, T. Qian, S.-B. Soonthornthum, B. Zhou, X. Zhang, J. Reichart, D.E. Haislip, J.B. Kouprianov, V.V. Poshyachinda, S. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Rd. Chaoyang District Beijing100012 China University of Chinese Academy of Sciences 19 A Yuquan Rd. Shijingshan Beijing100049 China National Astronomical Research Institute of Thailand Ministry of Science and Technology Bangkok Thailand Department of Physics and Astronomy University of North Carolina CB #3255 Chapel HillNC27599 United States

TY Pup is a well-known bright eclipsing binary with an orbital period of 0.8192 days. New light curves in B, V, (RI)C bands were obtained with the 0.61-m reflector robotic telescope (PROMPT-8) at CTIO in Chile during 2015 and 2017. By analysing those photometric data with the W-D method, it is found that TY Pup is a low-mass-ratio (q ∼ 0.184) and deep contact binary with a high fill-out factor (84.3 %). An investigation of all available times of minimum light including three new ones obtained with the 60-cm and the 1.0-m telescopes at Yunnan Observatories in China indicates that the period change of TY Pup is complex. An upward parabolic variation in the O − C diagram is detected to be superimposed on a cyclic oscillation. The upward parabolic change reveals a long-term continuous increase in the orbital period at a rate of dP/dt = 5.57(±0.08) × 10−8 d yr−1. The period increase can be explained by mass transfer from the less massive component (M2 ∼ 0.3M☉) to the more massive one (M1 ∼ 1.65M☉). The binary will be merging when it meets the criterion that the orbital angular momentum is less than 3 times the total spin angular momentum, i.e., Jorb rot. This suggests that the system will finally merge into a rapid-rotating single star and may produce a luminous red nova. The cyclic oscillation in the O − C diagram can be interpreted by the light-travel time effect (LITE) via the presence of a third body. Copyright © 2018, The Authors. All rights reserved.

关键词： Stars

A gamma-ray periodic modulation in globular cluster 47 tucanae

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Zhang, Peng-Fei Zhou, Jia-Neng Yan, Da-Hai Yan, Jing-Zhi Fan, Yi-Zhong Zhang, Li Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210034 China Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Yunnan Observatory Chinese Academy of Sciences Kunming650011 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 School of Astronomy and Space Science University of Science and Technology of China Hefei Anhui230026 China

The Globular Cluster 47 Tucanae was firstly detected in gamma-rays by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, and the gamma-ray emission has been widely attributed to the millisecond pulsars. In this work, we analyze the Fermi-LAT pass 8 data ranging from 2008 August to 2017 May and report the detection of a modulation with a period of 18:416 ± 0:008 hours at a significance level of ∼ 4:8σ. This is the first time to detect a significant modulation with a period much longer than that of millisecond pulsars in gamma-rays from Globular Clusters. The periodic modulation signal displays in the Swift-BAT data as well. The phase-folded Chandra X-ray light curve of a point source may have provided an additional clue. These facts indicate the detection of the first young pulsar binary in gamma-rays in Globular Clusters. Copyright © 2018, The Authors. All rights reserved.

关键词： Gamma rays

A search for exoplanets around northern circumpolar stars. IV. Six planet candidates to the K giants, HD 44385, HD 97619, HD 106574, HD 118904, HD 164428, and HD 202432

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Jeong, Gwanghui Han, Inwoo Park, Myeong-Gu Hatzes, Artie P. Bang, Tae-Yang Gu, Shenghong Bai, Jinming Lee, Byeong-Cheol Korea Astronomy and Space Science Institute 776 Daedeokdae-Ro Youseong-Gu Daejeon34055 Korea Republic of Korea University of Science and Technology 217 Gajeong-ro Yuseong-gu Daejeon34113 Korea Republic of Department of Astronomy and Atmospheric Sciences Kyungpook National University Daegu41566 Korea Republic of Thüringer Landessternwarte Tautenburg Sternwarte 5 TautenburgD-07778 Germany Yunnan Observatories Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

We report the discovery of long-period radial velocity (RV) variations in six intermediate mass K giant stars using precise RV measurements. These discoveries are part of the Search for Exoplanets around Northern Circumpolar Stars (SENS) survey being conducted at the Bohyunsan Optical Astronomy Observatory (BOAO). The nature of the RV variations was investigated by looking for photometric and line shape variations. We can find no variability with the RV period in these quantities and conclude that RV variations are most likely due to unseen sub-stellar companions. Orbital solutions for the six stars yield orbital periods in the range 418 - 1065 d and minimum masses in the range 1.9 - 8.5 MJ. These properties are typical on planets around intermediate mass stars. Our SENS survey so far has about an 8% confirmed planet occurrence rate, and it will provide better statistics on planets around giant stars when the survey is completed. Copyright © 2018, The Authors. All rights reserved.

关键词： Extrasolar planets

Applications of the k-ω model in stellar evolutionary models

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Li, Yan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

The k-ω model for turbulence was first proposed by Kolmogorov (1942). A new k-ω model for stellar convection was developed by Li (2012), which could reasonably describe turbulent convection not only in the convectively unstable zone but also in the overshooting regions. We have revised the k-ω model by improving several model assumptions (including the macro-length of turbulence, convective heat flux, and turbulent mixing diffusivity, etc.), making it applicable for not only convective envelopes but also convective cores. Eight parameters are introduced in the revised k-ω model. It should be noted that the Reynolds stress (turbulent pressure) is neglected in the equation of hydrostatic support. We have applied it into solar models and 5M stellar models, in order to calibrate the eight model parameters, as well as to investigate the effects of the convective overshooting on the sun and intermediate mass stellar models. Copyright © 2017, The Authors. All rights reserved.

关键词： Turbulence

Study of the X-ray properties of the neutron-star binary 4U 1728-34 from the soft to hard state

学校读者我要写书评

暂无评论

arXiv 2019年

作者： Wang, Yanan Méndez, Mariano Altamirano, Diego Zhang, Guobao Belloni, T.M. Ribeiro, Evandro M. Linares, M. Sanna, Andrea Motta, S.E. Tomsick, John A. Kapteyn Astronomical Institute University of Groningen PO BOX 800 GroningenNL-9700 AV Netherlands Physics & Astronomy University of Southampton Southampton HampshireSO17 1BJ United Kingdom Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Istituto Nazionale di Astrofisica Osservatorio Astronomico di Brera Via E. Bianchi 46 MerateI-23807 Italy Departament de Física EEBE Universitat Politècnica de Catalunya Av. Eduard Maristany 16 BarcelonaE-08019 Spain BarcelonaE-08034 Spain Dipartimento di Fisica Universitá degli Studi di Cagliari SP Monserrato-Sestu km 0.7 MonserratoI-09042 Italy University of Oxford Department of Physics Astrophysics Denys Wilkinson Building Keble Road OxfordOX1 3RH United Kingdom Space Sciences Laboratory University of California 7 Gauss Way BerkeleyCA94720-7450 United States

We studied five XMM-Newton observations of the neutron-star binary 4U 1728-34 covering the hard, intermediate and soft spectral states. By jointly fitting the spectra with several reflection models, we obtained an inclination angle of 25◦ − 53◦ and an iron abundance up to 10 times the solar. From the fits with reflection models, we found that the fluxes of the reflection and the Comptonised components vary inconsistently;since the latter is assumed to be the illuminating source, this result possibly indicates the contribution of the neutron star surface/boundary layer to the disc reflection. As the source evolved from the relatively soft to the intermediate state, the disc inner radius decreased, opposite to the prediction of the standard accretion disc model. We also explore the possible reasons why the supersolar iron abundance is required by the data and found that this high value is probably caused by the absence of the hard photons in the XMM-Newton data. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

Chemical properties of two dense cores in a planck galactic cold clump G168.72-15.48

学校读者我要写书评

暂无评论

arXiv 2019年

作者： Tang, Mengyao Ge, J.X. Qin, Sheng-Li Liu, Tie Wu, Yuefang Kim, Kee-Tae Liu, Sheng-Yuan Zhang, Chao He, J.H. Ju, Bing-Gang Fang, Xinhe Department of Astronomy Yunnan University Key Laboratory of Astroparticle Physics of Yunnan Province Kunming650091 China Departamento de Astronomía Universidad de Chile Camino el Observatorio 1515 Las Condes Santiago Chile Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Department of Astronomy Peking University Beijing100871 China Korea Astronomy and Space Science Institute 776 Daedeokdaero Yuseong-gu Daejeon34055 Korea Republic of University of Science and Technology 217 Gajeong-ro Yuseong-gu Daejeon34113 Korea Republic of Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Taipei10617 Taiwan Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming Yunnan Province650011 China Camino El Observatorio 1515 Las Condes Santiago Chile Departamento de Astronomía Universidad de Chile Las Condes Santiago Chile Purple Mountain Observatory Qinghai Station Delingha817000 China Department of Electronic Engineering Zhengzhou Railway Vocational & Technical College Zhengzhou451460 China

To deepen our understanding of the chemical properties of the Planck Galactic Cold Clump (PGCC) G168.72-15.48, we performed observations of nine molecular species, namely, c-C3H, H2CO, HC5N, HC7N, SO, CCH, N2H+, CH3OH, and CH3CCH, toward two dense cores in PGCC G168.72-15.48 using the Tianma Radio Telescope and Purple Mountain Observatory Telescope. We detected c-C3H, H2CO, HC5N, N2H+, CCH, and CH3OH in both G168-H1 and G168-H2 cores, whereas HC7N and CH3CCH were detected only in G168-H1 and SO was detected only in G168-H2. Mapping observations reveal that the CCH, N2H+, CH3OH, and CH3CCH emissions are well coupled with the dust emission in G168-H1. Additionally, N2H+exhibits an exceptionally weak emission in the denser and more evolved G168-H2 core, which may be attributed to the N2H+depletion. We suggest that the N2H+depletion in G168-H2 is dominated by N2depletion, rather than the destruction by CO. The local thermodynamic equilibrium calculations indicate that the carbon-chain molecules of CCH, HC5N, HC7N, and CH3CCH are more abundant in the younger G168-H1 core. We found that starless core G168-H1 may have the properties of cold dark clouds based on its abundances of carbon-chain molecules. While, the prestellar core G168-H2 exhibits lower carbon-chain molecular abundances than the general cold dark clouds. With our gas-grain astrochemical model calculations, we attribute the observed chemical differences between G168-H1 and G168-H2 to their different gas densities and different evolutionary stages. Copyright © 2019, The Authors. All rights reserved.

关键词： Molecules

The discrepancy between Einstein mass and dynamical mass for sis and power-law mass models

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Li, Rui Wang, Jiancheng Shu, Yiping Xu, Zhaoyi Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District 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 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Purple Mountain Observatory Chinese Academy of Sciences 2 West Beijing Road Nanjing Jiangsu210008 China Institute of Astronomy Madingley Road CambridgeCB3 0HA United Kingdom

We investigate the discrepancy between the two-dimensional projected lensing mass and the dynamical mass for an ensemble of 97 strong gravitational lensing systems discovered by the Sloan Lens ACS (SLACS) Survey, the BOSS Emission-Line Lens Survey (BELLS), and the BELLS for GALaxy-Lyα EmitteR sYstems (BELLS GALLERY) Survey. We fit the lensing data to obtain the Einstein mass, and use the velocity dispersion of the lensing galaxies provided by the Sloan Digital Sky Survey (SDSS) to get the projected dynamical mass within the Einstein radius by assuming the power-law mass approximation. The discrepancy is found to be obvious and quantified by Bayesian analysis. For the singular isothermal sphere (SIS) mass model, we obtain that the Einstein mass is 20.7% more than the dynamical mass, and the discrepancy increases with the redshift of the lensing galaxies. For more general power-law mass model, the discrepancy still exists within 1σ credible region. The main reason of the the discrepancy could be mass contamination, including all invisible masses along the line of sight. In addition, the measurement errors and the approximation of the mass models could lead to part of the discrepancy. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Linear polarization, circular polarization, and depolarization of gamma-ray bursts: A simple case of jitter radiation

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Mao, Jirong Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan Province650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Beijing100012 Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011

Linear and circular polarizations of gamma-ray bursts (GRBs) have been detected during recent years. We adopt a simplified model to investigate GRB polarization characteristics in this paper. A compressed two-dimensional turbulent slab containing stochastic magnetic fields is considered, and jitter radiation can produce the linear polarization under this special magnetic field topology. Turbulent Faraday rotation measure (RM) of this slab makes strong wavelengthdependent depolarization. The jitter photons can also scatter with those magnetic clumps inside the turbulent slab, and a nonzero variance of the Stokes parameter V can be generated. Furthermore, the linearly and circularly polarized photons in the optical and radio bands may suffer heavy absorptions from the slab. Thus we consider the polarized jitter radiation transfer processes. Finally, we compare our model results with the optical detections of GRB 091018, GRB 121024A, and GRB 131030A. We suggest simultaneous observations of GRB multi-wavelength polarization in the future. Copyright © 2017, The Authors. All rights reserved.

关键词： Stars

SEARCH FOR EXTENDED GEV SOURCES IN THE INNER GALACTIC PLANE

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Abdollahi, S. Acero, F. Acharyya, A. Adelfio, A. Ajello, M. Baldini, L. Ballet, J. Bartolini, C. Gonzalez, J. Becerra Bellazzini, R. Bissaldi, E. Bonino, R. Bruel, P. Cameron, R.A. Caraveo, P.A. Castro, D. Cavazzuti, E. Cheung, C.C. Cibrario, N. Ciprini, S. Cozzolongo, G. Orestano, P. Cristarella Cuoco, A. Cutini, S. D’Ammando, F. Di Lalla, N. Dinesh, A. Di Venere, L. Domínguez, A. Fiori, A. Funk, S. Fusco, P. Gargano, F. Gasbarra, C. Gasparrini, D. Germani, S. Giacchino, F. Giglietto, N. Giliberti, M. Giordano, F. Giroletti, M. Green, D. Grenier, I.A. Guillemot, L. Guiriec, S. Gupta, R. Hashizume, M. Hays, E. Hewitt, J.W. Horan, D. Hou, X. Kayanoki, T. Kuss, M. Laviron, A. Lemoine-Goumard, M. Liguori, A. Li, J. Liodakis, I. Loizzo, P. Longo, F. Loparco, F. Lorusso, L. Lovellette, M.N. Lubrano, P. Maldera, S. Malyshev, D. Martí-Devesa, G. Martin, P. Mazziotta, M.N. Mereu, I. Michelson, P.F. Mirabal, N. Mitthumsiri, W. Mizuno, T. Monti-Guarnieri, P. Monzani, M.E. Morselli, A. Moskalenko, I.V. Negro, M. Omodei, N. Orienti, M. Orlando, E. Paneque, D. Panzarini, G. Persic, M. Pesce-Rollins, M. Pillera, R. Porter, T.A. Rainò, S. Rando, R. Razzano, M. Reimer, A. Reimer, O. Bernal, M. Rocamora Sánchez-Conde, M. Parkinson, P.M. Saz Serini, D. Sgrò, C. Siskind, E.J. Smith, D.A. Spandre, G. Spinelli, P. Strong, A.W. Suson, D.J. Tajima, H. Thayer, J.B. Torres, D.F. Valverde, J. Wadiasingh, Z. Wood, K. Zaharijas, G. IRAP Université de Toulouse CNRS UPS CNES ToulouseF-31028 France AIM CEA CNRS Université Paris-Saclay Université de Paris Gif-sur-YvetteF-91191 France Center for Cosmology and Particle Physics Phenomenology University of Southern Denmark Campusvej 55 Odense MDK-5230 Denmark Istituto Nazionale di Fisica Nucleare Sezione di Perugia PerugiaI-06123 Italy Department of Physics and Astronomy Clemson University Kinard Lab of Physics ClemsonSC29634-0978 United States Università di Pisa Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Université Paris-Saclay Université Paris Cité CEA CNRS AIM Gif-sur-YvetteF-91191 Cedex France Istituto Nazionale di Fisica Nucleare Sezione di Bari BariI-70126 Italy Università degli studi di Trento via Calepina 14 Trento38122 Italy Instituto de Astrofísica de Canarias Universidad de La Laguna Dpto. Astrofísica Tenerife La Laguna38200 Spain Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Dipartimento di Fisica "M. Merlin" dell’Università e del Politecnico di Bari via Amendola 173 BariI-70126 Italy Istituto Nazionale di Fisica Nucleare Sezione di Torino TorinoI-10125 Italy Dipartimento di Fisica Università degli Studi di Torino TorinoI-10125 Italy Laboratoire Leprince-Ringuet CNRS IN2P3 École polytechnique Institut Polytechnique de Paris Palaiseau91120 France W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics SLAC National Accelerator Laboratory Stanford University StanfordCA94305 United States INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano via E. Bassini 15 MilanoI-20133 Italy Harvard-Smithsonian Center for Astrophysics CambridgeMA02138 United States Astrophysics Science Division NASA Goddard Space Flight Center GreenbeltMD20771 United States Italian Space Agency Via del Politecnico snc Roma00133 Italy Space Science Division Naval Research Laboratory Washin

The recent detection of extended γ-ray emission around middle-aged pulsars is interpreted as inverse-Compton scattering of ambient photons by electron-positron pairs escaping the pulsar wind nebula, which are confined near the system by unclear mechanisms. This emerging population of γ-ray sources was first discovered at TeV energies and remains underexplored in the GeV range. To address this, we conducted a systematic search for extended sources along the Galactic plane using 14 years of Fermi-LAT data above 10 GeV, aiming to identify a number of pulsar halo candidates and extend our view to lower energies. The search covered the inner Galactic plane (|l| ≤ 100◦, |b| ≤ 1◦) and the positions of known TeV sources and bright pulsars, yielding broader astrophysical interest. We found 40 such sources, forming the Second Fermi Galactic Extended Sources Catalog (2FGES), most with 68% containment radii smaller than 1.0◦ and relatively hard spectra with photon indices below 2.5. We assessed detection robustness using field-specific alternative interstellar emission models and by inspecting significance maps. Noting 13 sources previously known as extended in the 4FGL-DR3 catalog and five dubious sources from complex regions, we report 22 newly detected extended sources above 10 GeV. Of these, 13 coincide with H.E.S.S., HAWC, or LHAASO sources;six coincide with bright pulsars (including four also coincident with TeV sources);six are associated with 4FGL point sources only;and one has no association in the scanned catalogs. Notably, six to eight sources may be related to pulsars as classical pulsar wind nebulae or pulsar halos. © 2024, CC BY.

关键词： Gamma rays