Large grains in discs around young stars: ATCA observations of WW Chamaeleontis, RU Lupi and CS Chamaeleontis
Large grains in discs around young stars: ATCA observations of WW Chamaeleontis, RU Lupi and CS Chamaeleontis
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年轻恒星周围圆盘中的大颗粒：ATCA 对 WW Chamaeleontis、RU Lupi 和 CS Chamaeleontis 的观测
DOI：
10.1051/0004-6361:200810999
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发表时间：
2008
影响因子：
6.5
通讯作者：
T. Bourke
中科院分区：
文献类型：
--
作者：
D. Lommen;S. Maddison;C. Wright;E. Dishoeck;D. Wilner;T. Bourke
上下文。在几个百万年的过程中，年轻恒星周围圆盘中的颗粒从星际亚微米大小增长到小行星，大小可达数千公里。大颗粒或鹅卵石的热发射在厘米波长下最容易观察到。然而，其他排放机制也有贡献，最显著的是来自恒星风和色球活动的自由排放。目标。我们的目标是确定三颗T-Tauri恒星的厘米辐射机制。WW Cha和RU Lup最近被发现在它们的星周圆盘中至少有高达毫米大小的颗粒生长，根据高达3.3毫米的毫米数据。CS Cha在其外二元圆盘中也有类似的颗粒生长迹象。方法：研究方法。利用澳大利亚望远镜紧凑型阵列(ATCA)对TTauri恒星WW Cha和RU Lup进行了几年的毫米和厘米波长监测。新的ATCA7 mm系统也用于观察7 mm处的CS Cha。结果。在7 mm和16 mm处多次检测到WW Cha。我们在3.5厘米处检测到一次WWCHA，上限仅为6.3厘米。在16毫米处的排放在天、月和年的周期内是稳定的，而在3.5厘米处的排放是可变的。在16毫米的WW Cha区域发现了第二个年轻的恒星天体，Ced 112IRS 4。在7 mm处检测到RU Lup。在16 mm处观察3次，在3和6 cm处观察4次，发现这三个波段都是不同的。在7 mm处可检测到CS Cha，但信噪比不够高，不足以分辨外圆盘中的间隙。7毫米和16毫米观测的典型分辨率为5-10角秒，均方根∼为0.2mJy。结论。WW Cha在3、7和16 mm处的发射可以用毫米和厘米大小的“鹅卵石”的热发射很好地解释。在3.5至6.3厘米之间的厘米光谱指数与光厚电离风的发射是一致的，尽管厘米发射的高变率指向非热力贡献。RU Lup和CS Cha在1~7 mm的光谱能量分布与毫米级颗粒的热发射相一致。RU LUP的长波辐射和负光谱指数的变化表明，非热辐射是由光学薄等离子体产生的。
Context. Grains in discs around young stars grow from interstellar submicron sizes to planetesimals, up to thousands of kilometres in size, over the course of several Myr. Thermal emission of large grains or pebbles can be best observed at centimetre wavelengths. However, other emission mechanisms can contribute, most notably free-free emission from stellar winds and chromospheric activity. Aims. We aim to determine the mechanisms of centimetre emission for three T Tauri stars. WW Cha and RU Lup have recently been found to have grain growth at least up to millimetre sizes in their circumstellar discs, based on millimetre data up to 3.3 mm. CS Cha has similar indications of grain growth in its circumbinary disc. Methods. The T Tauri stars WW Cha and RU Lup were monitored over the course of several years at millimetre and centimetre wavelengths, using the Australia Telescope Compact Array (ATCA). The new ATCA 7 mm system was also used to observe CS Cha at 7 mm. Results. WW Cha was detected on several occasions at 7 and 16 mm. We obtained one detection of WW Cha at 3.5 cm and upper limits only for 6.3 cm. The emission at 16 mm was stable over periods of days, months, and years, whereas the emission at 3.5 cm is found to be variable. A second young stellar object, Ced 112 IRS 4, was found in the field of WW Cha at 16 mm. RU Lup was detected at 7 mm. It was observed at 16 mm three times and at 3 and 6 cm four times and found to be variable in all three wavebands. CS Cha was detected at 7 mm, but the signal-to-noise ratio was not high enough to resolve the gap in the circumbinary disc. The typical resolution of the 7 and 16 mm observations was 5-10 arcsec with rms ∼0.2 mJy. Conclusions. The emission at 3, 7, and 16 mm for WW Cha is explained well by thermal emission from millimetre and centimetre-sized "pebbles". The cm spectral index between 3.5 and 6.3 cm is consistent with the emission from an optically-thick ionised wind, although the high variability of the cm emission points to a non-thermal contribution. The spectral energy distributions of both 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 suggests non-thermal emission, arising from an optically-thin plasma.
适合 VLTI 观测的前主序谱双星，
影响因子：
6.5
作者：
Guenther;Esposito;Covino;Alcalá;Cusano;Stecklum
通讯作者：
Stecklum