arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0812.0388astro-ph
收藏

晚型恒星Stromgren紫外-β测光的定标--一种模式大气方法

The Calibration of Stromgren uvby-Hbeta Photometry for Late-Type Stars -- a Model Atmosphere Approach

A. Önehag, B. Gustafsson, K. Eriksson, B. Edvardsson

摘要:

我们的目标是测试的权力的理论校准的基础上,新一代的MARCS模型与观测photomeric数据进行比较。我们计算合成uvby-Hbeta颜色指数从合成光谱。一个388场星以及恒星的球状星团的样本是用来直接比较的综合指数与经验数据和仔细研究的可能性,温度,金属丰度和重力的理论校准。我们表明,合成(b-y)颜色的温度敏感性是非常接近其经验对应,而基于Hbeta的温度标度显示出轻微的偏移。根据光谱测定,m1指数(以及G型星与c1的组合)的理论金属丰度灵敏度略大于经验值。与F星的观测结果相比,合成c1指数的重力灵敏度表现出令人满意的行为。对于温度比太阳低的恒星,c1-(b-y)图中的偏差是显著的。(b-y)、(v-y)和c1的理论校准似乎适用于Pop II恒星,并导致球状星团恒星的有效温度支持Korn等人(2007)最近的主张,即在NGC 6397的关闭点附近的恒星中发生原子扩散。在许多情况下,恒星大气的合成颜色确实可以用来导出可靠的基本恒星参数。与观测数据相比,观察到的偏差可能是由于不完整的线表,但也可能是由于假设平行平面或球形几何形状和LTE的影响。

英文摘要:

We aim to test the power of theoretical calibrations based on a new generation of MARCS models by comparisons with observational photomteric data. We calculate synthetic uvby-Hbeta colour indices from synthetic spectra. A sample of 388 field stars as well as stars in globular clusters is used for a direct comparison of the synthetic indices versus empirical data and for scrutinizing the possibilities of theoretical calibrations for temperature, metallicity and gravity. We show that the temperature sensitivity of the synthetic (b-y) colour is very close to its empirical counterpart, whereas the temperature scale based upon Hbeta shows a slight offset. The theoretical metallicity sensitivity of the m1 index (and for G-type stars its combination with c1) is somewhat larger than the empirical one, based upon spectroscopic determinations. The gravity sensitivity of the synthetic c1 index shows a satisfactory behaviour when compared to obervations of F stars. For stars cooler than the sun a deviation is significant in the c1-(b-y) diagram. The theoretical calibrations of (b-y), (v-y) and c1 seem to work well for Pop II stars and lead to effective temperatures for globular cluster stars supporting recent claims by Korn et al. (2007) that atomic diffusion occurs in stars near the turnoff point of NGC 6397. Synthetic colours of stellar atmospheres can indeed be used, in many cases, to derive reliable fundamental stellar parameters. The deviations seen when compared to observational data could be due to incomplete linelists but are possibly also due to effects of assuming plane-parallell or spherical geometry and LTE.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑