标题： 经典T Tauri星在J和H波段的过量证据及其对盘结构和估计年龄的影响 显示英文标题

标题： Evidence for J and H-band excess in classical T Tauri stars and the implications for disk structure and estimated ages

摘要： 我们认为经典T Tauri星（cTTs）在J和H波段存在显著的非恒星辐射过剩。 首先我们展示，将cTTs的光谱能量分布（SED）归一化到J波段会导致光学波段的拟合效果较差，而归一化到Ic波段则能更好地拟合光学波段，并且在许多情况下揭示了J和H波段存在相当大的过剩。来自文献中的近红外光谱重归一化测量支持这一结果。 我们发现J和H波段的过剩与K波段的过剩密切相关，而且过剩发射的J-K和H-K颜色与尘埃升华温度下黑体辐射（~1500-2000 K）的颜色一致。 我们提出这种近红外过剩起源于一个热内缘，类似于那些用来解释Herbig Ae/Be星SED中近红外凸起现象所假设的内缘。 为了检验我们的假设，我们使用Dullemond等人（2001年）提出的模型来拟合与Chamaeleon II分子云相关的10颗cTTs在0.5微米到24微米之间的测光数据。 最能拟合这些数据的模型是那些盘内半径大于仅由光球辐射场平衡的内缘半径的模型。 特别是，我们发现需要较大的内缘才能解释由斯皮策太空望远镜获得的中红外通量（3.6-8.0微米）。 最后，我们指出通过修正J波段流量来推导cTTs的恒星亮度会系统性地高估这些亮度。 当把这些星放置在赫罗图中时，这些高估的亮度会转化为低估的年龄。 因此，本文的结果对内吸积盘消散的时间尺度有重要的意义。 显示英文摘要

摘要： We argue that classical T Tauri stars (cTTs) possess significant non- photospheric excess in the J and H bands. We first show that normalizing the spectral energy distributions (SEDs) of cTTs to the J-band leads to a poor fit of the optical fluxes, while normalizing the SEDs to the Ic-band produces a better fit to the optical bands and in many cases reveals the presence of a considerable excess at J and H. NIR spectroscopic veiling measurements from the literature support this result. We find that J and H-band excesses correlate well with the K-band excess, and that the J-K and H-K colors of the excess emission are consistent with that of a black body at the dust sublimation temperature (~ 1500-2000 K). We propose that this near-IR excess originates at a hot inner rim, analogous to those suggested to explain the near-IR bump in the SEDs of Herbig Ae/Be stars. To test our hypothesis, we use the model presented by Dullemond et al. (2001) to fit the photometry data between 0.5 um and 24 um of 10 cTTs associated with the Chamaeleon II molecular cloud. The models that best fit the data are those where the inner radius of the disk is larger than expected for a rim in thermal equilibrium with the photospheric radiation field alone. In particular, we find that large inner rims are necessary to account for the mid infrared fluxes (3.6-8.0 um) obtained by the Spitzer Space Telescope. Finally, we argue that deriving the stellar luminosities of cTTs by making bolometric corrections to the J-band fluxes systematically overestimates these luminosities. The overestimated luminosities translate into underestimated ages when the stars are placed in the H-R diagram. Thus, the results presented herein have important implications for the dissipation timescale of inner accretion disks.