GRB 170817A的洛伦兹因子和观测角

伴随着引力波事件GW170817的短暴GRB (Gamma-Ray Burst) 170817A首次提供了双中子星并合与短暴相联系的直接证据.但是短暴GRB 170817A具有非常弱的光度,意味着观测的视线方向可能偏离喷流轴方向.根据短暴静止系的峰值能量E_(p,i)和各向同性光度L_(iso)。之间的关系以及洛伦兹因子Γ和L_(iso)。之间的关系估算了短暴GRB 170817A以及长短暴GRB 060614观测角与喷流边缘的夹角θ'_(obs)和洛伦兹因子Γ,结果表明GRB 170817A的Γ=45±27,θ'_(obs)=2.2±0.5°,而GRB 060614的Γ=214±93,θ'_(obs)=0.5±0.1°.这个结果相当于GRB 170817A的正轴各向同性光度L_(iso,on)=(2.1±0.7)×10~(49) erg·s~(-1),比典型的短暴少2-3个数量级.GRB 060614的L_(iso,on)=(5.12±1.91)×10~(51) erg·s~(-1)与典型短暴相当.这意味着GRB 060614可能属于短暴类型,而GRB 170817A可能本质上就是一个弱暴.     

亮暗暴的早期X射线研究

研究亮暴和暗暴的X射线余辉,发现它们的X射线和γ流量的分布基本上相同。即:从统计学的角度上讲,亮暴和暗暴没有本质不同,它们的中心机制应该是相同的,暗暴的形成应该是由环境原因引起的。     

Explosion Mechanism of Core-Collapse Supernovae and Collapsars

We have performed 2-dimensional MHD simulations of collapsars with magnetic fields and neutrino cooling/heating processes. It is found that explosion energy of a hypernova is not obtained from the neutrino heating process. However, strong jet is found when magnetic fields are included, and total energy of the jet component can be of the order of 10⁵² erg, which is comparable to the one of a hypernova.     

泥蚶(Tegillarca granosa)生长因子受体结合蛋白2(GRB2)基因的克隆与表达分析

通过已构建的泥蚶(Tegillarca granosa)转录组文库, 利用SMART RACE技术扩增得到泥蚶Tg-GRB2基因的全长cDNA序列, 并对其生物信息学、组织表达及发育阶段表达特征进行了分析。结果表明, 泥蚶Tg-GRB2 cDNA全长1283bp, 开放阅读框为708bp, 编码236个氨基酸; 蛋白结构预测显示, Tg-GRB2蛋白包含SH3-SH2-SH3三个功能域, SH2结构域由两端的α-螺旋和中间反向平行的β-折叠片构成, SH3结构域主要由β-折叠片组成, 具备典型的结构特征; 氨基酸序列比对发现, Tg-GRB2与脊椎动物的同源性为62.1%—63.8%, 而与玻璃海鞘和日本血吸虫同源性较低。qRT-PCR检测结果显示: Tg-GRB2 mRNA在泥蚶血液、斧足、鳃、外套膜、闭壳肌、内脏团6个组织中都有表达, 而在血液中的表达量极显著地高于其它组织; 在泥蚶的不同发育阶段中, Tg-GRB2 mRNA在 2—4细胞胚胎、原肠胚、担轮幼虫、D形幼虫中均有较高的表达量, 而在D形幼虫中表达量最高, 表明Tg-GRB2基因在泥蚶早期发育中发挥重要调节作用。     

X-ray afterglow of GRB 050712: multiple energy injections into the external shock

As indicated by observed X-ray flares,a great amount of energy can be intermittently released from the postburst central engine of gamma-ray bursts(GRBs).As a natural consequence,the GRB’s external shock could be repeatedly energized.With such a multiple energy injection model,we explore the unique X-ray afterglow light curve of GRB 050712,which exhibits four shallow decay plateaus.Together with three early X-ray flares,the central engine of GRB 050712 is believed to have released energy at least seven times after the burst.Furthermore,we find that the energies released during the four plateaus are all on the same order of magnitude,but the luminosity significantly decreased with time.These results may provide some interesting implications for the GRB central engine.     

Infrared Afterglow of the Gamma Ray Burst GRB041219 as the Result of Reradiation from Dust in a Circumstellar Cloud

Observations of the afterglows of gamma ray bursts (GRBs) in different spectral ranges yield valuable information both about the nature of GRBs and about the properties of the surrounding medium. A powerful infrared (IR) afterglow has been observed at the site of the strong GRB041219. Here we interpret the observed IR afterglow as the result of a reprocessing of gamma radiation on dust in a cloud surrounding the GRB source. In this model we do not expect the appearance of a prompt optical afterglow which should be absorbed by the surrounding dust cloud. We estimate the collimation angle of the gamma radiation and obtain limits on the red shift (distance to the GRB source) by matching the model parameters to the experimental data.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 439–444 (August 2005).     

On the stellar origin of gamma ray bursts

We show that our original suggestion that gamma-ray bursts (GRB) may be flares on Magnetically Active Stellar Systems (MASS) namely flare stars, RS CVn binaries and Cataclysmic variables agrees well with the new observations of CGRO. We make a multi component fit to the log(N) - log(S) distribution and the high degree of isotropy as observed by the previous generation of satellites as well as BATSE/CGRO using the second BATSE catalogue. We then discuss individual source association and optical transient observations and show that they favor the present suggestion. We discuss the physical mechanisms and gamma-ray production processes that can occur on such systems giving the GRB their characteristics. We predict increase of anisotropy in the BATSE/CGRO observations for bright GRB.     

Relationship between pulse width and energy in GRB 060124: from X-ray to γ-ray bands

GRB 060124 is the first event that both prompt and afterglow emission were observed simultaneously by the three Swift instruments. Its main peak also triggered Konus-Wind and HETE-II. Therefore, investigation on both the temporal and spectral properties of the prompt emission can be extended to X-ray bands. We perform a detailed analysis on the two well identified pulses of this burst, and find that the pulses are narrower at higher energies, and both X-rays and γ-rays follow the same w–E relation for an individual pulse. However, there is no a universal power-law index of the w–E relation among pulses. We find also that the rise-to-decay ratio r/d seems not to evolve with E and the r/d values are well consistent with that observed in typical GRBs. The broadband spectral energy distribution also suggests that the X-rays are consistent with the spectral behavior of the γ-rays. These results indicate that the X-ray emission tracks the γ-ray emission and the emissions in the two energy bands are likely to be originated from the same physical mechanism.     

The investigation of Moskalenko's 1959 optical transient field inside GRB791101 error box

We report the results of an optical study of Moskalenko's OT 1959 field. The deep CCD images were obtained at the 6-m telescope of SAO RAS on June 8/9 1994. The BVR photometry of objects near the position of Moskalenko's OT 1959 are presented. An object with V= 23.43 and peculiar colours B-V= 0.9 and V-R= 1.10 was found. It is a possible candidate for the 1959 optical flash.     

Shallow Decay of X-ray Afterglows in Short GRBs： Energy Injection from a Millisecond Magnetar？

With the successful launch of Swift satellite,more and more data of early X-ray afterglows from short gamma-ray bursts have been collected.Some interesting features such as unusual afterglow light curves and unexpected X-ray flares are revealed.Especially,in some cases,there is a fiat segment in the X-ray afterglow light curve.Here we present a simplified model in which we believe that the flattening part is due to energy injection from the central engine.We assume that this energy injection arises from the magnetic dipole radiation of a millisecond pulsar formed after the merger of two neutron stars.We check this model with the short GRB 060313.Our numerical results suggest that energy injection from a millisecond magnetar could make part of the X-ray afterglow light curve flat.