e-MERLIN在波长5 cm处分辨参宿四
e-MERLIN resolves Betelgeuse at wavelength 5 cm
摘要：
对流、脉动和磁场都被认为是红超巨星的光学光球层向星风发射区输送质量和能量的机制。我们用e-MERLIN在5.5- 6.0GHz的频率上以0.06-0.18角秒的分辨率对红超巨星参宿四进行了成像，灵敏度为~ 0.01mJy/束。大部分射电辐射都来自一个椭圆（0.235x0.218）弧秒^[2]（约为光学半径的5倍）内，通量密度为1.62 mJy，平均亮温约为1250 K。这个射电光球包含两个热点，0.53和0.79 mJy/束，相隔90毫角秒，亮度温度为5400+/-600 K和3800+/-500 K。1992年、1995年和1996年，灵敏度较低的“老”MERLIN探测到了类似的热点，其距光球的距离是任何其他区域的两倍多，许多热点的温度超过了3600 K的光球温度。这样的亮度温度高到足以从色球等离子体的口袋中发出。其他可能性包括局部激波加热，热物质的对流疏浚或异常冷，低密度区域，透明到最热的层在~40毫弧秒半径。我们还检测到一个弧0.2- 0.3弧秒的SW，亮度温度~150 K，在一个类似的方向上看到的扩展在更小和更大的尺度在红外线和CO在毫米波长。这些初步结果将随后进行进一步的e-MERLIN，VLA和ALMA观测，以帮助解决红超巨星质量从1到10 R* 的问题。
英文摘要：
Convection, pulsation and magnetic fields have all been suggested as mechanisms for the transport of mass and energy from the optical photosphere of red supergiants, out to the region where the stellar wind is launched. We imaged the red supergiant Betelgeuse at 0.06-0.18 arcsec resolution, using e-MERLIN at 5.5--6.0 GHz, with a sensitivity of ~0.01 mJy/beam. Most of the radio emission comes from within an ellipse (0.235x0.218) arcsec^2 (~5x the optical radius), with a flux density of 1.62 mJy, giving an average brightness temperature ~1250 K. This radio photosphere contains two hotspots of 0.53 and 0.79 mJy/beam, separated by 90 milli-arcsec, with brightness temperatures 5400+/-600 K and 3800+/-500 K. Similar hotspots, at more than double the distance from the photosphere of those seen in any other regime, were detected by the less-sensitive `old' MERLIN in 1992, 1995 and 1996 and many exceed the photospheric temperature of 3600 K. Such brightness temperatures are high enough to emanate from pockets of chromospheric plasma. Other possibilities include local shock heating, the convective dredge-up of hot material or exceptionally cool, low density regions, transparent down to the hottest layer at ~40 milliarcsec radius. We also detect an arc 0.2--0.3 arcsec to the SW, brightness temperature ~150 K, in a similar direction to extensions seen on both smaller and larger scales in the infra-red and in CO at mm wavelengths. These preliminary results will be followed by further e-MERLIN, VLA and ALMA observations to help resolve the problem of mass elevation from 1 to 10 R* in red supergiants.
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