捕鱼--用光谱干涉观测法约束TX Psc的恒星参数
Catching the fish - Constraining stellar parameters for TX Psc using spectro-interferometric observations
摘要：
恒星参数的确定是一个具有挑战性的任务，在处理银河系巨星。事实证明，不同调查技术的结合是一种很有前途的方法。我们分析档案光谱获得的短波长光谱仪（SWS）板载的ISO，和新的干涉观测从甚大望远镜中红外干涉仪（VLTI/VLBI）的一个非常好的研究富碳巨星：TX Psc。这项工作的目的是确定恒星参数使用光谱学和干涉。观测结果被用来约束模型大气，并最终在碳星序列开始的轨迹映射区域的恒星演化模型。两种不同的方法被用来确定恒星参数：（一）“经典”的干涉测量方法，其中的有效温度是固定的，通过使用在N波段的角直径（从干涉测量）和表观测辐射热星等;（二）参数是通过拟合网格的国家的最先进的流体静力学模型光谱和干涉测量观测。我们发现这两种方法的参数之间有很好的一致性。有效温度和光度清楚地将TX Psc置于H-R图中富含碳的AGB星域中。目前的演化轨迹表明，TX Psc最近才成为一颗C星，这意味着与随后的强风状态相比，这颗恒星仍然处于“安静”阶段。这与C/O比仅略大于1是一致的。
英文摘要：
Stellar parameter determination is a challenging task when dealing with galactic giant stars. The combination of different investigation techniques has proven to be a promising approach. We analyse archive spectra obtained with the Short-Wavelength-Spectrometer (SWS) onboard of ISO, and new interferometric observations from the Very Large Telescope MID-infrared Interferometric instrument (VLTI/MIDI) of a very well studied carbon-rich giant: TX Psc. The aim of this work is to determine stellar parameters using spectroscopy and interferometry. The observations are used to constrain the model atmosphere, and eventually the stellar evolutionary model in the region where the tracks map the beginning of the carbon star sequence. Two different approaches are used to determine stellar parameters: (i) the 'classic' interferometric approach where the effective temperature is fixed by using the angular diameter in the N-band (from interferometry) and the apparent bolometric magnitude; (ii) parameters are obtained by fitting a grid of state-of-the-art hydrostatic models to spectroscopic and interferometric observations. We find a good agreement between the parameters of the two methods. The effective temperature and luminosity clearly place TX Psc in the carbon-rich AGB star domain in the H-R-diagram. Current evolutionary tracks suggest that TX Psc became a C-star just recently, which means that the star is still in a 'quiet' phase compared to the subsequent strong-wind regime. This is in agreement with the C/O ratio being only slightly larger than 1.
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