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arXiv 1004.2659astro-ph.GAastro-ph.SR
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对OH 26.5+0.6的OH极化结构的深入了解

Insight into the OH polarimetric structure of OH 26.5+0.6

S. Etoka, P. J. Diamond

摘要:

我们提出的第一个观点的磁场结构的OH壳的极端OH/IR星OH 26.5+0.6。1993年12月,在1612、1665和1667兆赫的全极化条件下,对该天体进行了梅林干涉仪观测。在1612和1667 MHz频率下,脉泽斑呈球状分布,而在1665 MHz频率下,峰位蓝移的脉泽辐射主要集中在恒星位置,峰位红移的脉泽辐射呈现SE-NW轴向的平行结构。两条主谱线的线性极化相当微弱,在1665 MHz时为9 - 20%,在1667 MHz时为0 - 30%。在1612兆赫的大多数微波激射点表现出类似的线性极化范围,虽然那些在最外面的部分的信封达到高达66%的值。这在贝壳的南部尤为明显。极化矢量的详细分布只能在1612 MHz下获得。极化矢量显示出高度结构化的分布,表明极向磁场相对于视线倾斜40-60 $^\circ$。在长球形包层的情况下,脉泽光斑的速度分布与径向距离的关系可以用等速各向同性流出来解释,该包层也相对于视线倾斜约45-65 $^\circ$。

英文摘要:

We present the first view of the magnetic field structure in the OH shell of the extreme OH/IR star OH 26.5+0.6. MERLIN interferometric observations of this object were obtained in December 1993 in full polarisation, at 1612, 1665 and 1667 MHz. The maser spots show a spheroidal distribution both at 1612 and 1667 MHz, while at 1665 MHz emission from the blue-shifted maser peak is concentrated on the stellar position, and the red-shifted peak emission exhibits a filamentary structure oriented on a SE-NW axis. The linear polarisation in both main lines is rather faint, ranging from 9 to 20% at 1665 MHz and from 0 to 30% at 1667 MHz. At 1612 MHz most maser spots exhibit a similar range of linear polarisation although those in the outermost parts of the envelope reach values as high as 66%. This is particularly apparent in the southern part of the shell. The detailed distribution of the polarisation vectors could only be obtained at 1612 MHz. The polarisation vectors show a highly structured distribution indicative of a poloidal magnetic field inclined by 40-60$^\circ$ to the line of sight. The velocity distribution of the maser spots with respect to the radial distance is well explained by an isotropic outflow at constant velocity in the case of a prolate shaped spheroid envelope, also tilted about 45-65$^\circ$ to the line of sight.

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