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Optical Transient Source AT2021lfa:A Possible“Dirty Fireball”

Research in Astronomy and Astrophysics 2024年第4期24卷 124-133页

作者： Xue-Mei Ye da-ming wei Yi-ming Zhu Zhi-Ping Jin Key Laboratory of dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China National Astronomical Observatories/Nanjing Institute of Astronomical Optics&Technology Chinese Academy of SciencesNanjing 210042China CAS Key Laboratory of Astronomical Optics&Technology Nanjing Institute of Astronomical Optics&TechnologyNanjing 210042China

AT2021lfa,also known as ZTF21aayokph,was detected by the Zwicky Transient Facility on 2021 May 4,a 05:34:48 ***-up observations were conducted using a range of ground-based optical telescopes,as wel as Swift/XRT and VLA ***2021lfa is classified as an“orphan afterglow”candidate due to its rapid flux decline and its reddened color(g-r=0.17±0.14 mag).For an optical transient source without promp gamma-ray detection,one key point is to determine its burst *** we measure the burst time through fitting the initial bump feature of AT2021lfa and obtain its burst time as 2021 May 3,at 22:09:50 *** afterglowpy,we model the multi-band afterglow of AT2021lfa and find that the standard model canno reproduce the late radio observations *** that the microphysical parameters ε_(e),ε_(B)(the energy fraction given to electrons and magnetic field),andξN(the fraction of accelerated electrons)may vary with time we then model the afterglow of AT2021lfa taking into account the temporal evolution of the physical parameters ε_(e),ε^(B),and ξ_(N) and find in this case the multi-wavelength observations can be reproduced *** initial Lorentz factor of AT2021lfa can be estimated from the peak time of the early afterglow,which yields a value of about 18 suggesting that AT2021lfa should be classified as a“dirty fireball.”From the upper limit for the prompt emission energy of AT2021lfa,we obtain that the radiation efficiency is less than 0.02%,which is much smaller than that of ordinary gamma-ray bursts(GRBs).It is also interesting that the fitted values of jet angle and viewing angle are very large,θ_(c)~0.66 rad,θ_(v)~0.53 rad,which may lead to the low Lorentz factor and radiation *** compared with GRB afterglow samples,it is evident that the onset bump timescale of AT2021lfa satisfies the empirical relationships observed in GRB ***,the luminosity of AT2021lfa falls within the range of observations for GRB samples;howeve

关键词： gamma-rays:ISM methods:numerical radiation mechanisms:non-thermal

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Black holes as the source of dark energy:A stringent test with high-redshift JWST AGNs

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Science China(Physics,Mechanics & Astronomy) 2024年第2期67卷 181-188页

作者： Lei Lei Lei Zu Guan-Wen Yuan Zhao-Qiang Shen Yi-Ying Wang Yuan-Zhu Wang Zhen-Bo Su Wen-Ke Ren Shao-Peng Tang Hao Zhou Chi Zhang Zhi-Ping Jin Lei Feng Yi-Zhong Fan da-ming wei Key Laboratory of dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China CAS Key Laboratory for Research in Galaxies and Cosmology Department of AstronomyUniversity of Science and Technology of ChinaHefei 230026China

Studies have proposed that there is evidence for cosmological coupling of black holes(BHs)with an index of k≈3;hence,BHs serve as the astrophysical source of dark ***,the data sample is limited for the redshifts of≤*** recent years,the James Webb Space Telescope(JWST)has detected many high-redshift active galactic nuclei(AGNs)and *** the JWST NIRSpec-/NIRCam-resolved AGNs,three are determined to be in early-type host galaxies with a redshift of z~***,their M_(*)and MBH are in tension with the predicted cosmological coupling of black holes with k=3 at a confidence level of~2σ,which challenges the hypothesis that BHs serve as the origin of dark *** work on high-redshift AGNs using the JWST will further assess such a hypothesis by identifying more early-type host galaxies in the higher mass range.

关键词： dark energy supermassive black hole active galactic nuclei James Webb Space Telescope

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X-ray Flashes from Off-axis Nonuniform Jets

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Chinese Journal of Astronomy and Astrophysics 2004年第5期4卷 473-480页

作者： Zhi-Ping Jin da-ming wei Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008 National Astronomical Observatories Chinese Academy of SciencesBeijing 100012

It has been widely believed that the outflows in gamma-ray bursts are jetted and some jets may have structures like ∈(θ)∝θ-k. We check the possibility that X-ray flashes come from such jets. Both qualitative and quantitative analyses have shown that this model can reproduce most of the observational features of both X-ray flashes and gamma-ray bursts. Using the usual parameters of gamma-ray bursts, we have carried out numerical calculations for both uniform and nonuniform jets, of their fluxes, spectra and peak energies. It seems that nonuniform jets are more appropriate to these observational properties than uniform jets. We have also shown that in our model the observational ratio of gamma-ray bursts to X-ray flashes is about a few units.

关键词： X-rays general-gamma rays bursts-ISM jets and outflows

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X-ray Emission Lines in GRB Afterglows: Evidence for a Two-component Jet Model

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Chinese Journal of Astronomy and Astrophysics 2005年第6期5卷 571-578页

作者： wei-Hong Gao da-ming wei Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

X-ray emission lines have been observed in X-ray afterglows of several T-ray bursts （GRBs）. It is a major breakthrough for understanding the nature of the progenitors. It has been proposed that the X-ray emission lines can be well explained by the Geometry-Dominated models, but in these models the illuminat- ing angle is much larger than that of the collimated jet of the GRB. For GRB 011211, we have obtained an illuminating angle of about 0 - 45°, while the angle of the GRB jet is only 3.6°. So we propose that the outflow of GRBs with emission lines should have two distinct components： a wide component that illuminates the reprocessing material and produces the emission lines and a narrow one that produces the GRB. Observations show the energy for producing the emission lines is higher than that of the GRB. In this case, when the wide component dominates the afterglows, a bump should appear in the GRB afterglow. For GRB 011211, the bump should occur within 0.05 days of the GRB, which is obviously too early for the observation to catch it. Alongside the X-ray emission lines there should also be a bright emission component between the UV and the soft X-rays. These features can be tested by the Swift satellite in the near future.

关键词： gamma rays: bursts -- line: profiles -- ISM: jets and outflows -- supernovae: general

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The Synchrotron-self-Compton Radiation Accompanying Shallow Decaying X-Ray Afterglow:the Case of GRB 940217

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Chinese Journal of Astronomy and Astrophysics 2007年第4期7卷 509-515页

作者： da-ming wei Yi-Zhong Fan Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Joint Center for Particle Nuclear Physics and Cosmology of Purple Mountain Observatory - Nanjing University Nanjing 210008 The Racah Inst. of Physics Hebrew University Jerusalem 91904 Israel Golda Meir Fellow

High energy emission （〉 tens MeV） of Gamma-Ray Bursts （GRBs） provides an important clue on the physical processes occurring in GRBs that may be correlated with the GRB early afterglow. A shallow decline phase has been well identified in about half of Swift Gamma-ray Burst x-ray afterglows. The widely considered interpretation *** a significant energy injection and possibly time-evolving shock parameter（s）. We calculate the synchrotron-self-Compton （SSC） radiation of such an external forward shock and show that it could explain the well-known long term high energy （i.e., tens MeV to GeV） afterglow of GRB 940217. We propose that cooperation of Swift and GLAST will help to reveal the nature of GRBs.

关键词： gamma-rays: bursts - ISM: jets and outflows - radiation mechanisms: non-thermal

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Run-and-Tumble Dynamics and Mechanotaxis Discovered in Microglial Migration

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Research 2024年第2期2023卷 95-103页

作者： Yiyu Zhang da wei Xiaochen Wang Boyi Wang ming Li Haiping Fang Yi Peng Qihui Fan Fangfu Ye Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Wenzhou Institute University of Chinese Academy of SciencesWenzhouZhejang 325000China Songshan Lake Materials Laboratory DongguanGuangdong 523808China School of Science East China University of Science and TechnologyShanghai 200237China Oujang Laboratory(Zhejiang Lab for Regenerative Medicine Vision and Brain Health)WenzhouZhejiang 325000China

Microglia are resident macrophage cells in the central nervous system that search for pathogens or abnormal neural activities and migrate to resolve the *** effective search and targeted motion of macrophages mean dearly to maintaining a healthy brain,yet little is known about their migration *** this work,we study microglial motion with and without the presence of external *** discover that the cells are promptly attracted by the applied forces(i.e.,mechanotaxis),which is a tactic behavior as yet unconfirmed in ***,in both the explorative and the targeted migration,microglia display dynamics that is strikingly analogous to bacterial run-and-tumble motion.A closer examination reveals that microglial run-and-tumble is more sophisticated,e.g.,they display a short-term memory when tumbling and rely on active steering during runs to achieve mechanotaxis,probably via the responses of mechanosensitive ion *** differences reflect the sharp contrast between microglia and bacteria cells(eukaryotes ***)and their environments(compact tissue ***).Further analyses suggest that the reported migration dynamics has an optimal search efficiency and is shared among a subset of immune cells(human monocyte and macrophage).This work reveals a fruitful analogy between the locomotion of 2 remote systems and provides a framework for studying immune cells exploring complex environments.

关键词： analogy closer prompt

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On the Jet Structures of GRB 050820A and GRB 070125

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Research in Astronomy and Astrophysics 2022年第8期22卷 249-257页

作者： Xin-Yu Li Hao-Ning He da-ming wei Key Laboratory of dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210033China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China

We present the broadband numerical modeling of afterglows for two remarkably bright long gamma-ray bursts(GRBs),GRB 050820 A and GRB 070125,with a wide range of observations from the radio band to the X-ray *** our work,we fit light curves and constrain physical parameters using a standard forward shock model from the afterglowpy Python package,considering different jet structures and the jet lateral *** GRB 050820 A,the constrained jet is close to a top-hat jet with an extremely small half opening angle of about 0.015 rad,and the circumburst matter density is as small as 10^(-7)cm^(-3),which suggests that this peculiar long GRB might originate from metal-poor stars with low mass-loss *** explain the late time optical light curves of GRB 070125,the effects of the lateral expansion and the participation factor of electrons that are accelerated by the shock have to be taken into *** constrained results for GRB 070125 show that the jet is also close to a top-hat jet with a half opening angle of about 0.1 rad,the viewing angle is about 0.05 rad,the circumburst density is about 10 cm^(-3),and the participation factor is about *** jet energy of the two bursts is required to be~1051–1052 erg,which can be produced by a millisecond magnetar or a hyper-accreting black hole.

关键词： methods:numerical ISM:jets and outflows gamma-rays:ISM gamma-rays:general

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Very Early Optical Afterglows for Geometric Models of X-ray Flashes and X-ray Rich GRBs

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Chinese Journal of Astronomy and Astrophysics 2007年第6期7卷 777-788页

作者： Ting Yan da-ming wei Yi-Zhong Fan Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 National Astronomical Observatories Chinese Academy of SciencesBeijing 100012 Department of Astrophysical and Planetary Sciences University of Colorado Boulder CO 80309 USA Joint Center for Particle Nuclear Physics and Cosmology of Purple Mountain Observatory - Nanjing University Nanjing 210008 The Racah Institute of Physics Hebrew University Jerusalem 91904 Israel

If X-ray flashes （XRFs） and X-ray rich Gamma-ray Bursts （XRRGs） have the same origin as the Gamma-ray bursts （GRBs） but are viewed off-center from structured jets, their early afterglows may differ from those of GRBs, and when the ultra-relativistic outflow inter- acts with the surrounding medium, there are two shocks formed, a forward shock （FS）, and a reverse shock （RS）. We calculate numerically the early afterglow powered by uniform jets, Gaussian jets and power-law jets in the forward-reverse shock scenario. A set of differential equations govern the dynamical evolution. The synchrotron self-Compton effect has been taken into account in the calculation. In the uniform jets, the very early afterglows of XRRGs and XRFs are significantly lower than the GRBs and the observed peak times of RS emission are later in the interstellar medium environment. The RS components in XRRGs and XRFs are difficult to detect, but in the stellar wind environment, the reduction of the very early flux and the delay of the RS peak time are not so remarkable. In nonuniform jets （Gaussian and power-law jets）, where there are emission materials on the line of sight, the very early light curve resembles equivalent isotropic ejecta in general although the RS flux decay index shows notable deviations if the RS is relativistic （in stellar wind）.

关键词： X-rays general -- Gamma rays bursts -- radiation mechanisms non-thermal

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A long journey： report of a case with pancreatic abscess extending to the groin

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Chinese Medical Journal 2010年第22期123卷 3362-3363页

作者： LU Hui-min ZHANG Zhao-da HU wei-ming Department of Hepato-bilio-pancreatic surgery West China Hospital Sichuan University Chengdu Sichuan 610041 China

Acute pancreatitis is an inflammatory process with .variable involvement of regional tissue, remote organ systems, or both. Various complications of pancreatitis are common, including intra- or extrapancreatic fluid collections and development of a pancreatic pseudocyst or abscess, or even pancreatic tissue necrosis. Infected necrosis involves diffuse bacterial inflammation of necrotic pancreatic and peripancreatic tissue without significant pus collection. In contrast, a pancreatic abscess is a circumscribed collection of pus, usually in proximity to the pancreas, that is positive for bacteria, bounded by adjacent tissue and organs and has minimal amounts of associated necrosis.

关键词： pancreatic abscess groin

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Classification of complete 3-dimensional self-shrinkers in the Euclidean space R^(4)

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Science China Mathematics 2024年第4期67卷 873-882页

作者： Qing-ming Cheng Zhi Li Guoxin wei Department of Applied Mathematics Faculty of ScienceFukuoka UniversityFukuoka 814-0180Japan College of Mathematics and Information Science Henan Normal UniversityXinxiang 453007China School of Mathematical Sciences South China Normal UniversityGuangzhou 510631China

In this paper,we completely classify 3-dimensional complete self-shrinkers with the constant norm S of the second fundamental form and the constant f3in the Euclidean space R^(4),where hij’s are components of the sec... 详细信息

关键词： mean curvature ow self-shrinker the generalized maximum principle

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