A systematic look at the very high and low/hard state of GX 339−4: constraining the black hole spin with a new reflection model

We present a systematic study of GX 339−4 in both its very high and low hard states from simultaneous observations made with XMM–Newton and RXTE in 2002 and 2004. The X-ray spectra of both these extreme states exhibit strong reflection signatures, with a broad, skewed Fe Kα line clearly visible above the continuum. Using a newly developed, self-consistent reflection model which implicitly includes the blackbody radiation of the disc as well as the effect of Comptonization, blurred with a relativistic line function, we were able to infer the spin parameter of GX 339−4 to be  0.935 ± 0.01  (statistical) ±0.01 (systematic) at 90 per cent confidence. We find that both states are consistent with an ionized thin accretion disc extending to the innermost stable circular orbit around the rapidly spinning black hole.     

The Formation of Black Hole Binaries

A peak exists in the distribution of observed black hole masses and no satisfactory explanation has been forthcoming so far. Here, we attempt an interpretation. We first establish a link between the helium core mass and the initial black hole mass, based on the result of 2-dimensional simulation of stellar core collapse by Fryer et al. Then the helium core masses are computed by using the PPE stellar evolution code, and the distribution of initial black hole masses for black hole binaries in stellar populations II and I is obtained. These are then compared with observations.     

The eccentric frame decomposition of central force fields

The rosette-shaped motion of a particle in a central force field is known to be classically solvable by quadratures. We present a new approach of describing and characterizing such motion based on the eccentricity vector of the two body problem. In general, this vector is not an integral of motion. However, the orbital motion, when viewed from the nonuniformly rotating frame defined by the orientation of the eccentricity vector, can be solved analytically and will either be a closed periodic circulation or libration. The motion with respect to inertial space is then given by integrating the argument of periapsis with respect to time. Finally we will apply the decomposition to a modern central potential, the spherical Hernquist–Newton potential, which models dark matter halos of galaxies with central black holes.     

Hyperaccretion after the Blandford-Znajek Process： A New Model for GRBs with X-Ray Flares Observed in Early Afterglows

We propose a three-stage model with Blandford-Znajek (BZ) and hyperaccretion process to interpret the recent observations of early afterglows of Gamma-Ray Bursts (GRBs). In the first stage, the prompt GRB is powered by a rotating black hole (BH) invoking the BZ process. The second stage is a quiet stage, in which the BZ process is shut off, and the accretion onto the BH is depressed by the torque exerted by the magnetic coupling (MC) process. Part of the rotational energy transported by the MC process from the BH is stored in the disk as magnetic energy. In the third stage, the MC process is shut off when the magnetic energy in the disk accumulates and triggers magnetic instability. At this moment, the hyperaccretion process may set in, and the jet launched in this restarted central engine generates the observed X-ray flares. This model can account for the energies and timescales of GRBs with X-ray flares observed in early afterglows.     

XTE J1901+014—the first low-mass Fast X-ray transient?

We continue to study the fast X-ray transient XTE J1901+014 discovered in 2002 by the RXTE observatory, whose nature has not yet been established. Based on the XMM-Newton observations of the source in 2006, we have obtained its energy spectrum, light curves, and power spectrum in the energy range 0.5–10 keV, which are in good agreement with our results obtained previously from the data of other observatories. In turn, this suggests that the source’s emission is stable in the quiescent state. The XMM-Newton observations also allowed the source’s localization accuracy to be improved to ≤2″, which subsequently enabled us to search for its optical companion with the RTT-150 and 6-m BTA (Special Astrophysical Observatory) telescopes. Combining optical, X-ray, and infrared observations, we have concluded that the optical companion in the system under study can be either a later-type star at a distance of several kpc or a very distant red giant or an A or F star. Thus, XTE J1901+014 may be the first low-mass fast X-ray transient.     

Use of the SHMAK clarity tube for measuring water clarity: Comparison with the black disk method

A metre‐long transparent tube for measuring visual water clarity was developed as part of the New Zealand Stream Health Monitoring and Assessment Kit (SHMAK) for use by non‐scientists. Water clarity measured using the tube (the horizontal sighting range of a black target) was compared with that measured using the standard “black disk” method (in which a black target is viewed horizontally underwater) to determine the feasibility of estimating black disk clarities from clarity tube readings. Readings using the two methods showed good agreement for waters with clarity <c. 50 cm. In clearer waters the slope of the relationship depends on the reflectivity of the background material used in the clarity tube. With a reflective background (white, reflectance c. 75%; or grey, reflectance c. 55%), the clarity tube readings are directly proportional and approximately equal to the black disk readings. With a black background (reflectance c. 5.5%), clarity tube readings >c. 50 cm are lower than the black disk visibility and follow a logarithmic relationship with visibility, which enables useful readings to be made in clearer water. Independent testing of the relationship showed that black disk visibilities may be predicted with reasonable confidence in waters that contain very low concentrations of dissolved humic materials (yellow substance). In waters that are noticeably brown‐coloured, the relationship is less consistent especially at black disk visibilities of more than 1.5 m. Recommendations are given for the use of the clarity tube.     

Effects of Laboratory Consolidation on Petrophysical Properties of Fine-Grained Marine Sediments: Electron Microscopic Observations

Abstract

Pliocene-Recent marine sediments, recovered at site 1125 by ODP Leg 181 on the eastern New Zealand margin, were subjected to laboratory consolidation tests and analyzed by scanning electron microscopy (SEM) before and after consolidation test. The primary objective of this study is to document the effects of consolidation on microfabric and petrophysical properties. X-ray diffraction and grain-size distribution data indicate that the samples are mineralogically and texturally similar and thus are ideal for the present study on the role of consolidation solely on petrophysical properties. Porosity was measured before and after each consolidation test, and permeability was estimated indirectly based on the theoretical method. SEM photomicrographs show details of changes of pore geometry and distribution after the consolidation test that account for the porosity loss.     

Preliminary Study on the Water Drag of Schlegel＇s Black Rockfish Sebastes schlegeli

Drag forces acting on Schlegel‘s black rockfish Sebastes schlegeli were studied. A new drag force transducer was designed and used to measure the water drag on Schlegel‘s black rockfish in a vertical recirculating flume tank. Fourteen individuals were investigated, yielding two mean drag coefficients referred to the cross-sectional area and volume^2/3 respectively at water velocities ranging from 0.3 to 1.0 ms^-1 The drag coefficients can be used for estimating the drag forces acting on Sebastes schlegeli in water.     

黔东北地区牛蹄塘组页岩气勘探前景分析

黔东北地区页岩气资源丰富,特别是牛蹄塘组勘探潜力巨大。本文在先期勘探失利井(CY1、HY1、FS1)分析基础之上,结合大量岩石露头、岩心分析测试数据,对黔东北地区页岩气的地质特征进行了系统研究,进一步落实了该地区资源潜力。研究认为：黔东北页岩气区下寒武统牛蹄塘组干酪根有机显微组分主要以腐泥无定型和腐殖无定型为主,有机质类型主要为Ⅰ型和Ⅱ1型;页岩层段有机质含量高,平均3.52%;镜质体反射率平均3.58%,为成熟晚期阶段;储层具有低孔超低渗、高比表面积等特征;页岩层脆性矿物含量平均64.2%,黏土矿物平均含量19.6%,牛蹄塘组硅质含量高,脆性较大,易于储层改造;黔东北地区页岩气可采资源量达0.12×1012 m3。可优选岑巩、沿河、秀山、德江、凯里等有利地区进行下一步的勘探和评价工作。