High-resolution H i and radio continuum observations of the SNR G290.1−0.8

We have observed the supernova remnant (SNR) G290.1−0.8 in the 21-cm H  i line and the 20-cm radio continuum using the Australia Telescope Compact Array (ATCA). The H  i data were combined with data from the Southern Galactic Plane Survey to recover the shortest spatial frequencies. In contrast, H  i absorption was analysed by filtering extended H  i emission, with spatial frequencies shorter than 1.1 kλ. The low-resolution ATCA radio continuum image of the remnant shows considerable internal structure, resembling a network of filaments across its 13-arcmin diameter. A high-resolution ATCA radio continuum image was also constructed to study the small-scale structure in the SNR. It shows that there are no structures smaller than ∼17 arcsec, except perhaps for a bright knot to the south, which is probably an unrelated object. The H  i absorption study shows that the gas distribution and kinematics in front of SNR G290.1−0.8 are complex. We estimate that the SNR probably lies in the Carina arm, at a distance 7 (±1) kpc. In addition, we have studied nearby sources in the observed field using archival multiwavelength data to determine their characteristics.     

γ射线暴的研究进展（Ⅳ：特强γ射线暴和软γ重复暴

最近CGRO上的仪器观测到了两个迄今为止发现的最强的λ暴GB930131和GB940217,其光子最高能量均达GeV量级;GB930131的峰值计数率达2×10~6个光子s~(-1);而GB940217的持续时间竟长达90min。另外沉寂了多年的软重复暴源SGR1900 14和SGR1806-20的再次爆发也由BATSE发现。一系列的观测还发现这些软重复暴均与X射线源对应且与超新星遗迹成协。文中对特强暴和软重暴(SGR)的性质及研究进展作了较为详细的评述。     

The integrated optical spectrum of the Crab nebula and evidence for its fading synchrotron continuum

A flux-calibrated optical spectrum integrated over the entire Crab nebula was obtained by making drift scans with a long-slit spectrograph. Compared to observations obtained over the past 40 years, these new data confirm an earlier controversial result that the [O iii ]  λλ4959, 5007  equivalent width is increasing with time, although the rate of ∼0.9 per cent yr⁻¹ is somewhat slower than that measured previously. Additionally, the Hβ equivalent width is increasing at a comparable rate, but the measured fluxes of both Hβ and [O  iii ] have changed less than their respective equivalent widths. The different rates of change in the measured fluxes and equivalent widths of these lines suggest that the optical synchrotron continuum from the Crab nebula is indeed fading rapidly. The apparent decline is consistent with a rate around  −0.5 (±0.2)  per cent yr⁻¹ at wavelengths near 5000  Å inferred independently from measurements of the optical continuum flux during the same time period.     

青藏高原唐古拉山口第四纪冰碛层划分及其地质环境意义

在对唐古拉山口现代冰川和古冰川考察研究的基础上，结合定位观测资料和TL、^10B-^26Al-^21Ne及^14C测年数据，对区内第四纪冰川遗迹进行了深入讨论，划分出二次冰期(即中更新世晚期的倒数第二次冰期、晚更新世中一晚期的末次冰期)和二次全新世冰进(即新冰期和小冰期)。提出在早更新世时，由于山体未达到当时冰川发育的雪线高度，所以未发育冰川。但在唐古拉山口地区，截止目前还未找到中更新世早期的倒数第三次冰期的冰川遗迹，由于高原隆升的滞后性和冰川发育的延滞效应及“亚洲干极”的耦合，推测仍只发育局部冰川作用。进一步研究表明，古今雪线由高原边缘向腹地升高，唐古拉山地区高出边缘1500m左右，生动表现了“亚洲干极”的作用；广泛分布的湖群说明羌塘地区是一个大江大河尚未伸入的内流地区，意味着青藏高原是个年青的高原。由于青藏高原的隆升，对高原腹地引起的干旱化过程和水分严重不足，使唐古拉山地区的冰川自倒数第二次冰期以来，冰川规模一次比一次明显地减小。     

宇宙线的超新星遗迹起源

宇宙线的起源是高能天体物理的核心问题之一.一直以来,超新星爆发被认为是能谱膝区以下宇宙线的主要来源.多波段观测表明,超新星遗迹有能力加速带电粒子至亚PeV (10~(15)eV)能量.扩散激波加速被认为是最有效的天体高能粒子加速机制之一,而超新星遗迹的大尺度激波正好为这一机制提供平台.近年来,一系列较高精度的地面和空间实验极大地推动了对宇宙线以及超新星遗迹的研究.新的观测事实挑战着传统的扩散激波加速模型以及其在银河系宇宙线超新星遗迹起源学说上的应用,深化了人们对宇宙高能现象的认识.结合超新星遗迹辐射能谱的时间演化特性,构建的时间依赖的超新星遗迹粒子加速模型,不仅能够解释200 GV附近宇宙线的能谱反常,还自然地形成能谱膝区,甚至可以将超新星遗迹粒子加速对宇宙线能谱的贡献延伸至踝区.该模型预期超新星遗迹中粒子的输运行为表现为湍流扩散,这需要未来的观测以及与粒子输运相关的等离子体数值模拟工作来进一步验证.     

内蒙古巴林右旗晚二叠世埃达克质火山岩特征及其地质意义

内蒙古东南部巴林右旗地区发育晚二叠世埃达克质火山岩,岩石组合为安山岩、粗安岩、英安岩及辉石安山岩,其LA-ICP-MS锆石U-Pb测年结果为256.7±2.7Ma,指示其形成于晚二叠世。地球化学特征显示,该套火山岩属准铝质-弱铝质中钾钙碱性岩石系列,具富Si(SiO_256%)、高Al(Al_2O_315%)、富Na、贫K、高Sr、低Yb和Y等特征,Na_2O/K_2O值为2.33~3.90,Mg~#值为35.3~60.8;稀土元素总量为96.69×10~(-6)~192.4×10~(-6)、轻重稀土元素分馏较明显((La/Yb)_N值为6.27~13.82),具正的Eu(δEu=1~1.67)异常,在原始地幔标准化蛛网图中,富集大离子亲石元素Rb、Ba、U,亏损高场强元素Nb、Ta,为O型(大洋型)埃达克质火山岩地球化学特征。综合区域资料,巴林右旗埃达克质火山岩是残留在地幔中的古亚洲洋残余洋壳部分熔融并受到地幔橄榄岩混染形成的,暗示晚二叠世存在古亚洲洋向华北板块俯冲消亡事件。     

Type Ia supernovae: An explosion in the regime of a convergent delayed detonation wave

The model of a presupernova’s carbon-oxygen (C-O) core with an initial mass of 1.33 M _⊙, an initial carbon abundance X _C ⁽⁰⁾ =0.27, and a mean rate of increase in mass of 5 × 10^?7 M _⊙ yr^?1 through accretion in a binary system evolved from the central density and temperature ρ_c=10⁹ g cm^?3 and T _c=2.05 × 10⁸K, respectively, by forming a convective core and its subsequent expansion to an explosive fuel ignition at the center. The evolution and explosion equations included only the carbon burning reaction ¹²C+¹²C with energy release corresponding to the complete conversion of carbon and oxygen (at the same rate as that of carbon) into ⁵⁶Ni. The ratio of mixing length to convection-zone size α_c was chosen as the parameter. Although the model assumptions were crude, we obtained an acceptable (for the theory of supernovae) pattern of explosion with a strong dependence of its duration on α_c. In our calculations with sufficiently large values of this parameter, α_c=4.0 × 10^?3 and 3.0×10^?3, fuel burned in the regime of prompt detonation. In the range 2.0×10^?3≥α_c≥3.0×10^?4, there was initially a deflagration with the generation of model pulsations whose amplitude gradually increased. Eventually, the detonation regime of burning arose, which was triggered from the model surface layers (with m ? 1.33 M _⊙) and propagated deep into the model up to the deflagration front. The generation of model pulsations and the formation of a detonation front are described in detail for α_c=1.0 × 10^?3.