New magnetic field measurements of β Cephei stars and slowly pulsating B stars

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B‐type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B (hereafter SPB) stars, along with a small number of normal B‐type stars. A weak mean longitudinal magnetic field of the order of a few hundred Gauss was detected in three β Cephei stars and two stars suspected to be β Cephei stars, in five SPB stars and eight stars suspected to be SPB stars. Additionally, a longitudinal magnetic field at a level larger than 3σ has been diagnosed in two normal B‐type stars, the nitrogen‐rich early B‐type star HD 52089 and in the B5 IV star HD 153716. Roughly one third of β Cephei stars have detected magnetic fields: Out of 13 β Cephei stars studied to date with FORS 1, four stars possess weak magnetic fields, and out of the sample of six suspected β Cephei stars two show a weak magnetic field. The fraction of magnetic SPBs and candidate SPBs is found to be higher: Roughly half of the 34 SPB stars have been found to be magnetic and among the 16 candidate SPBs eight stars possess magnetic fields. In an attempt to understand why only a fraction of pulsating stars exhibit magnetic fields, we studied the position of magnetic and non‐magnetic pulsating stars in the H‐R diagram. We find that their domains in the H‐R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence. It is possible that stronger fields tend to be found in stars with lower pulsating frequencies and smaller pulsating amplitudes. A somewhat similar trend is found if we consider a correlation between the field strength and the v sin i ‐values, i.e. stronger magnetic fields tend to be found in more slowly rotating stars (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A very rare triple-peaked type-I X-ray burst in the low-mass X-ray binary 4U 1636−53

We have discovered a triple-peaked X-ray burst from the low-mass X-ray binary (LMXB) 4U 1636−53 with the Rossi X-ray Timing Explorer ( RXTE ). This is the first triple-peaked burst reported from any LMXB using RXTE , and it is only the second burst of this kind observed from any source. (The previous one was also from 4U 1636−53, and was observed with EXOSAT .) From fits to time-resolved spectra, we find that this is not a radius-expansion burst, and the same triple-peaked pattern seen in the X-ray light curve is also present in the bolometric light curve of the burst. Similar to what was previously observed in double-peaked bursts from this source, the radius of the emitting area increases steadily during the burst, with short periods in between during which the radius remains more or less constant. The temperature first increases steeply, and then decreases across the burst also showing three peaks. The first and last peak in the temperature profile occur, respectively, significantly before and after the first and last peaks in the X-ray and bolometric light curves. We found no significant oscillations during this burst. This triple-peaked burst, as well as the one observed with EXOSAT and the double-peak bursts in this source, all took place when 4U 1636−53 occupied a relatively narrow region in the colour–colour diagram, corresponding to a relatively high (inferred) mass-accretion rate. No model presently available is able to explain the multiple-peaked bursts.     

Constraining jet/disc geometry and radiative processes in stellar black holes XTE J1118+480 and GX 339−4

We present results from modelling of quasi-simultaneous broad-band (radio through X-ray) observations of the Galactic stellar black hole (BH) transient X-ray binary (XRB) systems XTE J1118+480 and GX 339−4 using an irradiated disc + compact jet model. In addition to quantifying the physical properties of the jet, we have developed a new irradiated disc model which also constrains the geometry and temperature of the outer accretion disc by assuming a disc heated by viscous energy release and X-ray irradiation from the inner regions. For the source XTE J1118+480, which has better spectral coverage of the two in optical and near-infrared (OIR) wavelengths, we show that the entire broad-band continuum can be well described by an outflow-dominated model + an irradiated disc. The best-fitting radius of the outer edge of the disc is consistent with the Roche lobe geometry of the system, and the temperature of the outer edge of the accretion disc is similar to those found for other XRBs. Irradiation of the disc by the jet is found to be negligible for this source. For GX 339−4, the entire continuum is well described by the jet-dominated model only, with no disc component required. For the two XRBs, which have very different physical and orbital parameters and were in different accretion states during the observations, the sizes of the jet base are similar and both seem to prefer a high fraction of non-thermal electrons in the acceleration/shock region and a magnetically dominated plasma in the jet. These results, along with recent similar results from modelling other galactic XRBs and AGNs, may suggest an inherent unity in diversity in the geometric and radiative properties of compact jets from accreting black holes.     

Effect of structure-directing agent on AlPO4-n synthesis from aluminum dross

The hydrothermal synthesis of AlPO₄-n which is a functional material of aluminophosphate, was conducted from two kinds of aluminum dross discharged in an aluminum regeneration factory. The effect of structure-directing agent (SDA) on the formation behavior of AlPO₄-n from aluminum dross, the suitable condition to obtain AlPO₄-n efficiently, and the pore structure and gas adsorption property were investigated in this study.AlPO₄-5 and AlPO₄-34 are mainly formed from aluminum dross as a raw material, and it is possible to make AlPO₄-5 successfully as a main product by adjusting the amount of triethylamine (TEA) as SDA. The gas adsorption amount with AlPO₄-5 is the following order; ammonia > dipropylamine > benzene, and it is found that this order mainly corresponds with the polarity of molecule among them.     

Breakdown of hydrous ringwoodite to pyroxene and spinelloid at high P and T and oxidizing conditions

To get deeper insight into the phase relations in the end-member system Fe₂SiO₄ and in the system (Fe, Mg)₂SiO₄ experiments were performed in a multi-anvil apparatus at 7 and 13 GPa and 1,000–1,200°C as a function of oxygen fugacity. The oxygen fugacity was varied using the solid oxygen buffer systems Fe/FeO, quartz–fayalite–magnetite, MtW and Ni/NiO. The run products were characterized by electron microprobe, Raman- and FTIR-spectroscopy, X-ray powder diffraction and transmission electron microscopy. At fO₂ corresponding to Ni/NiO Fe-ringwoodite transforms to ferrosilite and spinelloid according to the reaction: 9 Fe₂SiO₄ + O₂ = 6 FeSiO₃ + 5 Fe_2.40Si_0.60O₄. Refinement of site occupancies in combination with stoichiometric Fe³⁺ calculations show that 32% of the total Fe is incorporated as Fe³⁺ according to From the Rietveld refinement we identified spl as spinelloid III (isostructural with wadsleyite) and/or spinelloid V. As we used water in excess in the experiments the run products were also analyzed for structural water incorporation. Adding Mg to the system increases the stability field of ringwoodite to higher oxygen fugacity and the spinel structure seems to accept higher Fe³⁺ but also water concentrations that may be linked. At oxygen fugacity corresponding to MtW conditions similar phase relations in respect to the breakdown reaction in the Fe-end-member system were observed but with a strong fractionation of Fe into spl and Mg into coexisting cpx. Thus, through this strong fractionation it is possible to stabilize very Fe-rich wadsleyite with considerable Fe³⁺ concentrations even at an intermediate Fe–Mg bulk composition: assuming constant K _D independent on composition and a bulk composition of x _Fe = 0.44 this fractionation would stabilize spl with x _Fe = 0.72. Thus, spl could be a potential Fe³⁺ bearing phase at P–T conditions of the transition zone but because of the oxidizing conditions and the Fe-rich bulk composition needed one would expect it more in subduction zone environments than in the transition zone in senso stricto.

基于SDP4模型的导航卫星仰角及方位角预报

地面站可控天线可以不借助接收机而直接监测导航卫星的信号质量,地面天线伺服系统根据卫星的实时位置计算出仰角及方位角来确定天线的指向。广播星历及历书等常用的计算卫星位置的方法虽误差较小,但其误差随时间迅速扩大,基于该问题,论文论述了双行星历（TLE）结合SDP4模型进行卫星轨道预报方法,利用SDP4模型计算GPS导航卫星的实时位置并预报卫星的仰角及方位角,采用IGS 事后精密星历对其角度预报误差进行了评估,同时,还将该方法的预报误差与广播星历、历书、STK高精度轨道预报等方法的预报误差进行了对比。实验结果表明：采用SDP4模型对导航卫星进行位置预报可满足误差要求,且时间有效性长、通用性好,具备实际应用价值。     

怀4井气体取样对水位观测干扰的解决措施

怀4井水位观测一直存在取气样所造成的干扰,其表现为水位分钟值曲线每天出现有规律的向上脉冲式突跳且持续时间较长,这使得数据连续率及完整率降低。为改变怀4井长期存在的取气样影响水位观测的现状,减少水位观测数据突跳次数,提高观测质量精度,针对取气样方式进行改进,采用球胆排水真空脱气法进行溶解气样品的采集与脱气,避开直接在泄流口采样时的压力效应,从而解决了水位观测中遇到的实际问题。     

京津冀一次飑线过程的精细时空演变特征分析

利用常规探空资料、多普勒天气雷达资料和风廓线雷达资料对2013年3月19日夜里到20日凌晨发生在湖南中南部和广东北部的一次区域性雷暴大风天气进行了分析,发现本次强对流天气过程的天气尺度背景是北支高压脊的崩溃和南支槽的建立,槽前出现较强的低空急流和切变线并在湖南中南部和广东北部形成了上干冷下暖湿的温湿配置结构下发生并强烈发展的;地面自动站观测显示北风侵入到前期露点温度较高的贵州黄平地区并形成风向辐合触发了对流,之后对流单体东移进入前期地面辐合线和露点锋相配合,同时500 hPa极为干冷的湖南中部偏南地区不断发展加强成对流带;雷达观测显示19日夜里在湖南西部不断出现对流单体并在其东移南下过程中最终形成飑线结构,该飑线中存在多个超级单体;通过多普勒天气雷达的中气旋产品与雷暴大风出现时间对应比较发现：大多数由中气旋引发的雷暴大风,在雷暴大风出现前2~3个体扫,其中气旋底高不断下降至2 km左右或以下,且在雷暴大风出现前1~2个体扫,中气旋的最强切变高度显著下降至中气旋底高位置附近;通过风廓线雷达数据与雷暴大风出现时间对应比较发现：底层大气折射率结构常数(C2n)大幅度的跃升通常在雷暴大风出现前10~15 min左右出现,其对雷暴大风的出现可能具有一定的指示意义。基于雷达资料快速更新四维变分同化（RR4DVar）分析系统,利用京津冀6部新一代多普勒天气雷达资料和区域（约700个）自动站资料对2013年7月30—31日京津冀地区一次飑线系统在移动过程中系统不同部位的热动力结构及其环境场时空演变特征进行了分析。结果表明,这次飑线过程是在有利的天气尺度背景形势下发生发展的。飑线形成初期,其中段和南段前部有强的暖湿空气辐合上升运动,并受到强的中层垂直风切变的影响,且在飑线中南段两侧水平正负涡度近似平衡,这种环境下,十分有利于飑线中南段的组织发展。而北段前部受弱的中层垂直风切变及辐散下沉运动影响,不利于北段系统有组织的发展;随着飑线移动下山,中段和南段前部在较强的中层垂直风切变控制下,出现强的暖湿空气辐合上升运动,且存在偏南暖湿气流稳定输送到系统上升运动区中,这对飑线系统中段和南段自身对流单体新生及高度组织化极为有利。随着飑线演变为弓形回波,中段环境场仍维持强的中层垂直风切变且位于冷池出流边界的控制之下,由于地形强迫效应,有利于弓形回波前沿低空偏南暖湿气流的辐合上升,是飑线下山迅速增强并发展成弓形回波,且稳定维持的主要原因。     

Studying the X-ray hysteresis in GX 339−4: the disc and iron line over one decade

We report on a comprehensive and consistent investigation into the X-ray emission from GX 339−4. All public observations in the 11 year RXTE archive were analysed. Three different types of model – single power law, broken power law and a disc + power law – were fitted to investigate the evolution of the disc, along with a fixed Gaussian component at 6.4 keV to investigate any iron line in the spectrum. We show that the relative variation in flux and X-ray colour between the two best sampled outbursts are very similar. The decay of the disc temperature during the outburst is clearly seen in the soft state. The expected decay is   S _Disc∝ T ⁴  ; we measure   T ^4.75±0.23  . This implies that the inner disc radius is approximately constant in the soft state. We also show a significant anticorrelation between the iron line equivalent width (EW) and the X-ray flux in the soft state while in the hard state the EW is independent of the flux. This results in hysteresis in the relation between X-ray flux and both line flux and EW. To compare the X-ray binary outburst to the behaviour seen in active galactic nuclei (AGN), we construct a disc fraction luminosity diagram for GX 339−4, the first for an X-ray binary. The shape qualitatively matches that produced for AGN. Linking this with the radio emission from GX 339−4 the change in radio spectrum between the disc and power-law-dominated states is clearly visible.     

Methane-rich fluid inclusions and their hosting volcanic reservoir rocks of the Songliao Basin, NE China

Methane-rich fluids were recognized to be hosted in the reservoir volcanic rocks as primary inclusions.Samples were collected from core-drillings of volcanic gas reservoirs with reversed δ12C of alkane in the Xujiaweizi depression of the Songliao Basin. The volcanic rocks are rhyolite dominant being enriched in the more incompatible elements like Cs, Rb, Ba, Th, U and Th with relative high LREE, depleted HREE and negative anomalies of Ti and Nb,suggesting a melt involving both in mantle source and crustal assimilation. Primary fluids hosted in the volcanic rocks should have the same provenance with the magma. The authors concluded that the enclosed CH4 in the volcanics are mantle/magma-derived alkane and the reversed δ13C of alkane in the corresponding gas reservoirs is partly resulted from mixture between biogenic and abiogenic gases.