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X-ray spectroscopy evidence for plasma shell formation in experiments modeling accretion columns in young stars

Matter and Radiation at Extremes 2019年第6期4卷 22-29页

作者： E.D.Filippov I.Yu.Skobelev G.Revet S.N.Chen B.Khiar A.Ciardi D.Khaghani D.P.Higginson S.A.Pikuz J.Fuchs Joint Institute for High Temperatures RAS125412 MoscowRussia National Research Nuclear University “MEPHI”115409 MoscowRussia LULI-CNRS ´Ecole PolytechniqueCEA:Universit´e Paris-SaclayUPMC Univ Paris 06:Sorbonne Universit´eF-91128 Palaiseau CedexFrance ELI-NP “Horia Hulubei”National Institute for Physics and Nuclear Engineering30 Reactorului StreetRO-077125 Bucharest-MagureleRomania Sorbonne Universit´e Observatoire de ParisUniversit´e PSLCNRSLERMAF-75005 ParisFrance Flash Center for Computational Science University of Chicago5640 S.Ellis AvenueChicagoIllinois 60637USA University of Bordeaux CEACNRSCentre Lasers Intenses et ApplicationsUMR 510733405 Talence CedexFrance Lawrence Livermore National Laboratory LivermoreCalifornia 94551USA

Recent achievements in laboratory astrophysics experiments with high-power lasers have allowed progress in our understanding of the early stages of star formation.In particular,we have recently demonstrated the possibility of simulating in the laboratory the process of the accretion of matter on young stars[G.Revet et al.,Sci.Adv.3,e1700982(2017)].The present paper focuses on x-ray spectroscopy methods that allow us to investigate the complex plasma hydrodynamics involved in such experiments.We demonstrate that we can infer the formation of a plasma shell,surrounding the accretion column at the location of impact with the stellar surface,and thus resolve the present discrepancies between mass accretion rates derived from x-ray and optical-radiation astronomical observations originating from the same object.In our experiments,the accretion column ismodeled by having a collimated narrow(1 mm diameter)plasma stream first propagate along the lines of a large-scale external magnetic field and then impact onto an obstacle,mimicking the high-density region of the stellar chromosphere.A combined approach using steady-state and quasi-stationarymodels was successfully applied tomeasure the parameters of the plasma all along its propagation,at the impact site,and in the structure surrounding the impact region.The formation of a hot plasma shell,surrounding the denser and colder core,formed by the incoming stream of matter is observed near the obstacle using x-ray spatially resolved spectroscopy.

关键词： accretion stars stellar

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The Orbital Modulation for the Spectrum and Mass accretion Rate in Circinus X-1

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International Journal of Astronomy and Astrophysics 2012年第4期2卷 256-265页

作者： Guoqiang Ding Chunping Huang Jinlu Qu Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China University of Chinese Academy of Sciences Beijing China Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi China

Using the data from the Proportional Counter Array on board theRossi X-Ray Timing Explorersatellite, we study the orbital modulation for the spectrum and mass accretion rate of Cir X-1 during its two orbital periods. We use a model consisting of a blackbody, a multicolor disk blackbody, and a line component to fit the spectrum and find that the spectrum is obviously modulated by the orbital phase. It is shown that the disk accretion rate in Cir X-1 undergoes three states during the orbital period. At the periastron with orbital phase 0-0.1, the disk accretion rate is sup-Eddington, then from phase 0.1 to the apastron (phase 0.5) it decreases dramatically and becomes near-Eddington, and from the apastron to the next periastron (phase 1) the disk accretion rate approximates Eddington and tends to be steady. We argue that the evolution of the disk accretion rate is attributed to the high orbital eccentricity of this source. The mass accretion rate onto the neutron star is much less than that onto the inner disk, indicating significant outflows in this source.

关键词： accretion Disk Compact Object Neutron Star Individual (Circinus X-1)

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Remote Sensing and GIS for the Spatio-Temporal Change Analysis of the East and the West River Bank Erosion and accretion of Jamuna River (1995-2015), Bangladesh

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Journal of Geoscience and Environment Protection 2017年第9期5卷 79-92页

作者： Md Arafat Hassan Suriya Jesmine Ratna Masud Hassan Sonia Tamanna Department of Geography and Environment University of Dhaka Dhaka Bangladesh Department of Soil Water and Environment University of Dhaka Dhaka Bangladesh Chittagong University of Engineering and Technology Chittagong Bangladesh

Jamuna River is one of the principal rivers of Bangladesh, changing continuously due to erosion and accretion over the past decades. This analysis evaluates the East Bank and the West Bank erosion and accretion between 1996 and 2015 for Jamuna River. An unsupervised classification algorithm and post-classification change employing skills in Geographic Information System are performed to evaluate spatial and temporal dynamics of erosion and accretion for different points of Jamuna River using Bangladesh. Landsat image (1995, 2005, 2015). The correctness of the Landsat-produced map ranges from 82% to 84%. It has been evidently observed that changes in the proportion of erosion and accretion differ in different points of Jamuna River. The highest eroded area is 3.82 square kilometers (km2) during the period of 1995 to 2005 and the highest accreted area is 6.15 square kilometers (km2) during the period of 1995 to 2015. The erosion and accretion values fluctuated from place to place. The changing trend of Riverbank is creating many socio-economic problems in the proximate areas.

关键词： Remote Sensing GIS River Erosion accretion Change Analysis Jamuna River

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Stability of accretion Discs around Magnetized Stars

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International Journal of Astronomy and Astrophysics 2014年第2期4卷 319-331页

作者： Solomon Belay Tessema Department of Physics Kotebe University College Addis Ababa Ethiopia

We study the stability of accretion disc around magnetised stars. Starting from the equations of magnetohydrodynamics we derive equations for linearized perturbation of geometrically thin, optically thick axisymmetric accretion disc with an internal dynamo around magnetized stars. The structure and evolution of such discs are governed by an evolution equation for matter surface density ∑(R,T). Using the time-dependent equations for an accretion disc we do a linear stability analysis of our steady disc solutions in the presence of the magnetic field generated due to an internal dynamo.

关键词： accretion accretion Discs Instabilities Stability Magnetic Fields MHD Stars Neutron X-Rays Binaries

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Coastal Abrasion and accretion Studies of West Sumatera Province in Period 2003-2016

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Journal of Environmental Science and Engineering(A) 2018年第1期7卷 22-29页

作者： Haryani Agus Irianto Nurhasan Syah Faculty of Civil Engineering and Planning Bung Hatta UniversityPadang City 25133Indonesia Faculty of Economi State University of PadangPadang City 25132Indonesia Faculty of Engineering State University of PadangPadang City 25132Indonesia

West Sumatera province has 19 cities and regencies where 6 of them often experience abrasion and accretion disaster,because it is a coastal area directly adjacent to the Indian Ocean.This study aims to examine the characteristics of abrasion and accretion disasters along the coast of West Sumatera Province from 2003 to 2016.By knowing the characteristics of abrasion and accretion from 2003 and 2016,it will be known which beaches are experiencing abrasion or accretion.This research is qualitative and quantitative descriptive research with GIS(Geographic Information System)analysis method to get characteristic of abrasion and accretion disaster in coastal area of West Sumatera.There has been a disaster of abrasion and accretion in 32 points spread across 6 districts and cities,namely West Pasaman District,Agam Regency,Padang Pariaman District,Pariaman City,Padang City and Padang Pariaman District,an abrasion disaster in the coastal area of West Sumatera Province of 732.69 Ha and 55.4 Ha of acres.This proves that the abrasion debacle causes the decrease of land in West Sumatera Province which is big enough that is average 56.3 Ha/year,while the addition of land is only 4.26 Ha/year.The farthest abrasion disasters are located in South Pesisir Regency,which is 45.70 m or 3.52 m/year on average.While the farthest accretion is in the South Pesisir Regency,and is as far as 36.91 m or an average of 2.84 m/year.

关键词： Abrasion accretion coastal disaster West Sumatera

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Areal Extent of Erosion and accretion in and around the Gahirmatha Coast, NW of Bay of Bengal by Remote Sensing and GIS Analysis of Multi-Temporal Satellite Imagery

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International Journal of Geosciences 2015年第7期6卷 705-719页

作者： Balabathina Veeraanarayanaa Kandula Ravikumar Talluri Ramesh Mopada Venkateswararao Pattam N. Sridhar P.I SYS-SERC Department of Science & Technology New Delhi India Department of Geology Andhra University Waltair India Department of Geography Andhra University Waltair India National Remote Sensing Agency Department of Space ISRO Hyderabad India

The shoreline morphology change due to erosion and deposition is a major concern for coastal zone management. In the present study, a highly dynamic coast of Gahirmatha on Bay of Bengal? in northeast India is experiencing active erosion, which is mainly wave and tide erosion related hazard threat ending human habitation and sustainability of the coast. In our study, high resolution satellite imagery of time series provided detailed sequence of coastal morphology and their changes in all respects. Comparison study of relative shoreline positions on time series satellite data spanning?three decades from 1973 to 2004 covering for the years of 1973, 1983, 1987, 1990, 1998, 2000 and 2004, provided regional changes with accelerated erosion and accretion. The result of the studies?have revealed that the areas of severe erosion found along the coast are confined to the promontories of the present day mouths itself of the Baitrani at Dhamra and Brahmani at Maipura inlets. In this background, it is significant to understand the magnitude of factors that are responsible for prograding or retrograding of coast. The present study is an attempt in this direction.

关键词： accretion Erosion Morphology Coast Temporal Satellite Data

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Cold Atoms Identified as Inflows Fueling Quasar Black Hole accretion Disks

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Bulletin of the Chinese Academy of Sciences 2019年第2期33卷 87-90页

作者： SONG Jianlan 不详

A group of scientists reported in Nature their latest discovery of a large amount of hydrogen and helium gases on the outer brim of the accretion disks surrounding the central supermassive black holes in a sample of quasars. Their strongly redshifted and broadened absorption lines indicate that they are moving at freefall-like speeds and hence deemed prey of the mighty gravitation of the supermassive black holes.

关键词： discovery accretion holes

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Repeating fast radio bursts from collapses of the crust of a strange star

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The Innovation 2021年第4期2卷 5-10页

作者： Jinjun Geng Bing Li Yongfeng Huang Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Particle Astrophysics Division Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China School of Astronomy and Space Science Nanjing UniversityNanjing 210023China Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210023China

Strange stars(SSs)are compact objects made of deconfined quarks.It is hard to distinguish SSs from neutron stars as a thin crust composed of normal hadronic matter may exist and obscure the whole surface of the SS.Here we suggest that the intriguing repeating fast radio bursts(FRBs)are produced by the intermittent fractional collapses of the crust of an SS induced by refilling of materials accreted from its low-mass companion.The periodic/sporadic/clustered temporal behaviors of FRBs could be well understood in our scenario.Especially,the periodicity is attributed to the modulation of accretion rate through the disk instabilities.To account for a~16-day periodicity of the repeating FRB source of 180916.J0158+65,a Shakura-Sunyaev disk with a viscosity parameter of 0.004 and an accretion rate of 3×10^(16)gs^(-1) is invoked.Our scenario,if favored by future observations,will serve as indirect evidence for the strange quark matter hypothesis.

关键词： accretion compact objects radio bursts degenerate matter low-mass X-ray binary stars

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Trend judgment of abandoned channels and fine architecture characterization in meandering river reservoirs: A case study of Neogene Minhuazhen Formation NmⅢ2 layer in Shijiutuo bulge, Chengning uplift, Bohai Bay Basin, East China

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Petroleum Exploration and Development 2019年第5期46卷 943-953页

作者： NIU Bo ZHAO Jiahong FU Ping LI Junjian BAO Zhidong HU Yong SU Jinchang GAO Xingjun ZHANG Chi YU Dengfei ZANG Dongsheng LI Min College of Geosciences China University of PetroleumBeijing 102249China Research Institute of Exploration and Development PetroChina Jilin Oilfield CompanySongyuan 138001China No.5 Oil Production Plant PetroChina Changqing Oilfield CompanyXi’an 710020China Bohai Oilfield Research Institute CNOOC Tianjin CompanyTianjin 300452China PetroChina Research Institute of Petroleum Exploration&Development Beijing 100083China

Based on well logging responses,sedimentary patterns and sandstone thickness,the distribution characteristics of meandering river sedimentary sand body of Neogene Minghuazhen Formation NmⅢ2 layer in the west of Shijiutuo Bulge,Chengning Uplift,Bohai Bay Basin were investigated.A new approach to calculate the occurrence of the sand-mudstone interfaces using resistivity log of horizontal well was advanced to solve the multiple solution problem of abandoned channel’s orientation.This method uses the trigonometric function relationship between radius,dip and length of the resistivity log to calculate the occurrence qualitatively-quantitatively to help determine the true direction of the abandoned channels.This method can supplement and improve the architecture dissection technique for meandering river sandbodies.This method was used to study the dip angle and scale of the lateral accretion layers in point bar quantitatively to help determine the spatial distribution of lateral accretion layers.The fine architecture model of underground meandering river reservoir in the study area has been established.Different from traditional grids,different grid densities for lateral accretion layers and bodies were used in this model by non-uniform upscaling to establish the inner architecture model of point-bars and realize industrial numerical simulation of the whole study area.The research results can help us predict the distribution of remaining oil,tap remaining oil,and optimize the waterflooding in oilfields.

关键词： Bohai Bay Basin meandering river horizontal well resistivity curve lateral accretion layers lateral accretion bodies architecture modeling remaining oil distribution

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A striking confluence between theory and observations of high-mass X-ray binary pulsars

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Research in Astronomy and Astrophysics 2018年第10期18卷 117-122页

作者： Dimitris M.Christodoulou Silas G.T.Laycock Demosthenes Kazanas Lowell Center for Space Science and Technology University of Massachusetts Lowell Dept.of Mathematical Sciences Univ.of Massachusetts Lowell Dept. of Physics & Applied Physics Univ. of Massachusetts Lowell NASA/GSFC Laboratory for High-Energy Astrophysics

We analyze the most powerful X-ray outbursts from neutron stars in eleven Magellanic high-mass X-ray binaries and three pulsating ultraluminous X-ray sources. Most of the outbursts rise to Lmax which is about the level of the Eddington luminosity, while the remaining more powerful outbursts also appear to recognize that limit when their emissions are assumed to be anisotropic and beamed toward our direction. We use the measurements of pulsar spin periods Ps and their derivatives Ps to calculate the X-ray luminosities Lp in their faintest accreting （＂propeller-line＂） states. In five cases with unknown Ps, we use the lowest observed X-ray luminosities, which only adds to the heterogeneity of the sample. Then we calculate the ratios Lp/Lmax and we obtain an outstanding confluence of theory and observations from which we conclude that work done on both fronts is accurate and the results are trustworthy： sources known to reside on the lowest Magellanic propeller line are all located on/near that line, whereas other sources jump higher and reach higher-lying propeller lines. These jumps can be interpreted in only one way, higher-lying pulsars have stronger surface magnetic fields in agreement with previous empirical results in which Ps and Lp values were not used.

关键词： accretion accretion disks - stars magnetic fields - stars neutron - X-rays binaries

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