Wolf-Rayet stars

Summary Recent literature on Population I Wolf-Rayet star research extending from the Milky Way to blue compact dwarf galaxies is reviewed, broken down into inventory, basic parameters and galactic distribution, atmospheres, binaries, intrinsic variability, mass loss, enrichment and evolution. Also the incidence of Wolf-Rayet stars with variable non-thermal radio emission, excess X-ray fluxes, and episodic/periodic IR excesses is reviewed. These phenomena appear to be associated with wind-wind interaction in wide long-period WR+OB binaries and with wind-compact object interaction in WR+c binaries, with orbit sizes of the order of magnitude of the WR radio photosphere sizes or larger.     

Detecting the first objects in the mid-infrared with the Next Generation Space Telescope

We calculate the expected mid-infrared (MIR) molecular hydrogen line emission from the first objects in the Universe. As a result of their low masses, the stellar feedback from massive stars is able to blow away their gas content and collect it into a cooling shell where H₂ rapidly forms and IR roto-vibrational (as for example the rest-frame 2.12 μm) lines carry away a large fraction (up to 10 per cent) of the explosion energy. The fluxes from these sources are in the range 10⁻²¹–10⁻¹⁷ erg s⁻¹ cm⁻² . The highest number counts are expected in the 20-μm band, where about 10⁵ sources deg⁻² are predicted at the limiting flux of 3×10⁻¹⁸ erg s⁻¹ cm⁻². Among the planned observational facilities, we find that the best detection perspectives are offered by the Next Generation Space Telescope ( NGST ), which should be able to reveal about 200 first objects in one hour observation time at its limiting flux in the above band. Therefore, mid-IR instruments appear to represent perfect tools to trace star formation and stellar feedback in the high ( z ≳5) redshift Universe.     

The radio and X-ray properties of Abell 2319

New radio and X-ray data are reported for the rich cluster Abell 2319. This object is known from optical data to consist of two separate clusters, which are displaced by about 10′ in the NW direction, and could be in a pre-merger state.

In the radio domain, the cluster is characterized by the presence of a central diffuse halo source, more extended and powerful than the prototype halo in the Coma cluster. The radio halo shows an irregular structure, elongated in the NE-SW direction, and also extended towards the NW. We also report data on the extended radio galaxies located within the halo, or in its proximity.

The cluster X-ray brightness distribution shows an elongated structure towards the NW, in the radial region between 6′–12′, i.e. in the direction of the subcluster. This feature is exactly coincident with the NW extension of the radio halo. In addition, more substructural features are identified which could be due to an ongoing merger of the cluster with yet another mass component.

The radio halo morphology is correlated with the X-ray structure and the existence of merger processes in the cluster. The cluster merger can provide energy to maintain the radio halo, while the origin of the relativistic particles seems more problematic.     

矿物的导电类型与矿物形成温度的关系

通过杂质对导电类型的影响的研究,得出了同种矿物的不同导电类型与矿物形成温度的规律:电子型(n型)导电矿物的形成温度大于电子与空穴混合型导电矿物的形成温度,又大于空穴型(p型)导电矿物的形成温度,绝缘体矿物的形成温度低于上述三种导电类型矿物。应用矿物热电图谱仪,天然金刚石半导体测试仪对闪锌矿、黄铁矿、金刚石等矿物的导电类型进行了测试,并探讨了导电类型成因,证实了上述规律的正确性。