Cohen R J, Downs G, Emerson R, Grimm M, Gulkis S, Stevens G, Tarter J
Nuffield Radio Astronomy Laboratories, Macclesfield, Cheshire.
Mon Not R Astron Soc. 1987;225:491-8. doi: 10.1093/mnras/225.3.491.
High-resolution OH 1612-MHz spectra are presented of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420 and NML Cyg. The spectra have a resolution of 300 Hz. Narrow components in the spectra have linewidths as small as 550 Hz (0.1 km s-1) but there is no evidence for components narrower than this. These results are in accord with present understanding of maser line-narrowing and of the physical conditions in the OH maser regions. Many of the narrow components have an appreciable degree of circular polarization which is not apparent at the lower frequency resolutions usually employed. The circular polarization indicates the presence of magnetic fields of approximately 1 mG in the circumstellar envelopes, at distances of approximately 3x10(16) cm from the central stars. These fields are strong enough to influence the outflow from the stars, and may help to explain some of the asymmetries which are seen in their circumstellar envelopes.
本文给出了超巨星OH红外源VY CMa、VX Sgr、IRC 10420和NML Cyg的高分辨率OH 1612兆赫光谱。这些光谱的分辨率为300赫兹。光谱中的窄成分线宽小至550赫兹（0.1千米每秒），但没有证据表明存在比这更窄的成分。这些结果与目前对脉泽线变窄以及OH脉泽区域物理条件的理解一致。许多窄成分具有相当程度的圆偏振，这在通常采用的较低频率分辨率下并不明显。圆偏振表明在距中心恒星约3×10¹⁶厘米的星周包层中存在约1毫高斯的磁场。这些磁场强度足以影响恒星的外流，并可能有助于解释在它们的星周包层中所观察到的一些不对称现象。
