年轻恒星周围盘中的大颗粒：WW Cha、RU Lup和CS Cha的ATCA观测
Large grains in disks around young stars: ATCA observations of WW Cha, RU Lup, and CS Cha
摘要：
年轻恒星周围的尘埃盘中的颗粒从星际亚微米大小成长为星子，经历了数百万年的过程。大颗粒或卵石的热发射可以在cm波长处最好地观察到。然而，其他排放机制也有贡献。我们的目标是确定3 T金牛星的厘米发射机制。最近发现WW Cha和RU Lup在其拱星盘中具有至少达mm尺寸的晶粒生长。CS Cha在其环双星盘中也有类似的晶粒生长迹象。TTauri星WW Cha和RU Lup在毫米和厘米波长上进行了几年的监测，使用ATCA。新的ATCA 7 mm系统也用于观察CS Cha。WW Cha在7和16 mm处多次检测到。我们在3 cm处检测到一次WW Cha，上限仅为6 cm。在16毫米的排放量是稳定的几天，几个月和几年，但在3厘米的排放量是可变的。在7 mm处检测RU Lup，在16 mm处观察3次，在3 cm和6 cm处观察4次，发现在所有3个波段中均可变。在7 mm处检测到CS Cha，但S/N太低，无法分辨环双星盘中的间隙。WW Cha在3、7和16 mm处的发射很好地解释了来自mm和cm大小的卵石的热发射。厘米光谱指数是一致的，从光学厚电离风的排放，但厘米排放点的非热贡献的高变异性。RU Lup和CS Cha从1到7 mm的SED与来自mm尺寸颗粒的热发射一致。RU Lup的较长波长发射的可变性和负光谱指数表明非热发射。
英文摘要：
Grains in disks around young stars grow from interstellar submicron sizes to planetesimals over the course of several Myr. Thermal emission of large grains or pebbles can be best observed at cm wavelengths. However, other emission mechanisms can contribute. We aim to determine the mechanisms of cm emission for 3 T Tauri stars. WW Cha and RU Lup were recently found to have grain growth at least up to mm sizes in their circumstellar disks. CS Cha has similar indications for grain growth in its circumbinary disk. The T Tauri stars WW Cha and RU Lup were monitored over several years at mm and cm wavelengths, using ATCA. The new ATCA 7 mm system was also used to observe CS Cha. WW Cha was detected on several occasions at 7 and 16 mm. We obtained one detection of WW Cha at 3 cm and upper limits only at 6 cm. The emission at 16 mm was stable over days, months and years, but the emission at 3 cm is found to be variable. RU Lup was detected at 7 mm. It was observed at 16 mm 3 times and at 3 and 6 cm 4 times and found to be variable in all 3 wavebands. CS Cha was detected at 7 mm, but the S/N was too low to resolve the gap in the circumbinary disk. The emission at 3, 7 and 16 mm for WW Cha is well explained by thermal emission from mm and cm-sized pebbles. The cm spectral index is consistent with the emission from an optically-thick ionised wind, but the high variability of the cm emission points to a non-thermal contribution. The SEDs of RU Lup and CS Cha from 1 to 7 mm are consistent with thermal emission from mm-sized grains. The variability of the longer-wavelength emission for RU Lup and the negative spectral index suggest non-thermal emission.
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