Chamaeleon I云中的初始碎片盘
An Incipient Debris Disk in the Chamaeleon I Cloud
摘要：
一个原行星盘变成碎片盘的点很难确定。为了更好地理解这一点，我们在这里研究了Chamaeleon I云中的$\sim$ 40~AU分离双星T~54。我们得到了T~54~A的K5光谱类型（它支配着系统的发射）和$\sim$ 2~Myr的年龄。然而，T~54的尘埃盘性质与在较老和较早型恒星周围看到的碎片盘一致。与此同时，T~54有证据表明，气体残留在磁盘中的[Ne II]，[Ne III]和[O I]线检测。我们模拟了T~54的光谱能量分布，估计$\sim$ 3 $\times$ 10 $^{-3}$地球质量的小尘埃颗粒（$<$ 0.25~ $μ$ m）存在于光学薄的环双星盘中，在环主星盘中至少存在$\sim$ 3 $\times$ 10 $^{-7}$地球质量的较大颗粒（$>$ 10~ $μ$ m）。假设一个类似太阳的混合物，我们使用Ne线的光度来放置一个最小限度的气体质量的磁盘（$\sim$ 3 $\times$ 10 $^{-4}$地球质量），并得出一个气体-尘埃质量比为$\sim$ 0.1。我们没有检测到大量的吸积，但我们确实看到H $α$在一个时期的排放，这表明可能有间歇性的少量物质倾倒到恒星上。考虑到T~54的尘埃质量较低、存在气体和年龄较年轻，我们认为该系统处于原行星阶段和碎片盘阶段之间。
英文摘要：
The point at which a protoplanetary disk becomes a debris disk is difficult to identify. To better understand this, here we study the $\sim$40~AU separation binary T~54 in the Chamaeleon I cloud. We derive a K5 spectral type for T~54~A (which dominates the emission of the system) and an age of $\sim$2~Myr. However, the dust disk properties of T~54 are consistent with those of debris disks seen around older and earlier-type stars. At the same time, T~54 has evidence of gas remaining in the disk as indicated by [Ne II], [Ne III], and [O I] line detections. We model the spectral energy distribution of T~54 and estimate that $\sim$3$\times$10$^{-3}$ Earth-masses of small dust grains ($<$0.25~$μ$m) are present in an optically thin circumbinary disk along with at least $\sim$3$\times$10$^{-7}$ Earth-masses of larger ($>$10~$μ$m) grains within a circumprimary disk. Assuming a solar-like mixture, we use Ne line luminosities to place a minimum limit on the gas mass of the disk ($\sim$3$\times$10$^{-4}$ Earth-masses) and derive a gas-to-dust mass ratio of $\sim$0.1. We do not detect substantial accretion, but we do see H$α$ in emission in one epoch, suggestive that there may be intermittent dumping of small amounts of matter onto the star. Considering the low dust mass, the presence of gas, and young age of T~54, we conclude that this system is on the bridge between the protoplanetary and debris disk stages.
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