更新0.1< M/Mo<1.5的低金属丰度下的主序前轨迹
Updated Pre-Main Sequence tracks at low metallicities for 0.1< M/Mo<1.5
摘要：
正在对Z<Zo的年轻人口进行检查，以了解金属丰度在恒星演化的第一阶段中的作用。为了进行分析，有必要给主序前（PMS）星分配质量和年龄。虽然众所周知，PMS恒星的质量和年龄测定强烈地受到对流处理的影响，但在没有对流参数的任何校准品的情况下，将任何校准扩展到不同于太阳的金属丰度是非常人为的。对于太阳丰度，混合长度理论模型已被使用的二维辐射流体动力学模式（MLTa 2D）的结果进行了校准，其结果是非常相似的非灰色ATLAS 9大气边界条件和湍流（FST）对流模式在大气和内部（NEMO-FST模式）的全谱计算。虽然MLTa 2D模型不适用于较低的金属丰度，我们扩展到较低的Z NEMO-FST模型，在受过教育的猜测，以这种方式，我们也模拟在较小的Z MLTa 2D的结果。我们提出了金属丰度[Fe/H]=-0.5，-1.0和-2.0的0.1 ~ 1.5Mo低质量恒星的PMS模型。计算包括最新的内部物理和最新一代的非灰色大气模型。这些进化轨迹和等时线的电子版可在网址http://www.mporzio.astro.it/%7Etsa/上找到。
英文摘要：
Young populations at Z<Zo are being examined to understand the role of metallicity in the first phases of stellar evolution. For the analysis it is necessary to assign mass and age to Pre--Main Sequence (PMS) stars. While it is well known that the mass and age determination of PMS stars is strongly affected by the convection treatment, extending any calibration to metallicities different from solar one is very artificial, in the absence of any calibrators for the convective parameters. For solar abundance, Mixing Lenght Theory models have been calibrated by using the results of 2D radiative-hydrodynamical models (MLTa2D), that result to be very similar to those computed with non-grey ATLAS9 atmosphere boundary condition and full spectrum of turbolence (FST) convection model both in the atmosphere and in the interior (NEMO--FST models). While MLTa2D models are not available for lower metallicities, we extend to lower Z the NEMO--FST models, in the educated guess that in such a way we are simulating also at smaller Z the results of MLTa2D. We present PMS models for low mass stars from 0.1 to 1.5 Mo for metallicities [Fe/H]= -0.5, -1.0 and -2.0. The calculations include the most recent interior physics and the latest generation of non-grey atmosphere models. These evolutionary tracks and isochrones are available in electronic form at a WEB site http://www.mporzio.astro.it/%7Etsa/
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