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arXiv 0901.3034astro-ph.SR
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用2 MASS星表实现红外通量法的新方法

A new implementation of the infrared flux method using the 2MASS catalogue

J. I. González Hernández, P. Bonifacio

摘要:

我们提出了一个新的实现红外通量方法(IRFM)使用2 MASS目录。我们计算的理论量在2 MASS JHKs过滤器集成理论通量计算从ATLAS模型,并将它们直接与观测到的2 MASS JHKs的幅度。这是我们的IRFM和Ramirez & Melendez的主要区别,因为为了引入最低金属丰度的新恒星,他们将2 MASS JHKs星等转换为TCS测光系统。我们在我们的样本中合并了阿隆索和合作者的矮星与拉米雷斯和梅伦德斯,卡萨格兰德等人,Christlieb et al.和Bonifacio et al.在我们的样本中,最终的恒星数量是555颗矮星和次巨星,以及264颗巨星。我们得到一个新的辐射热通量校准使用现有的约翰逊-费因斯UBVRI和2 MASS JHKs测光。我们还计算新的Teff与颜色的经验校准使用我们的扩展样本的恒星。我们得到了Alonso等人样品中几乎所有恒星的有效温度,发现我们的温度标度比它们高出~ 64 K(dT= 104 K,N=332个矮星)和~ 54 K(dT= 131 K,N=202个巨星)。与Ramirez & Melendez的[Fe/H]<-2.5的恒星样本进行同样的比较,得到了~-87K的差异(dT= 194 K,N=12颗矮星)和~ 61 K的差异(dT= 62 K,N=18颗巨星)。对于富金属矮星,我们的温标比Alonso等人和Ramirez & Melendez的温标略热,但对于贫金属矮星,我们的温标比Ramirez & Melendez的温标冷。我们已经完成了一个完全自洽的IRFM在2 MASS测光系统。对于那些希望使用2 MASS测光和色温校准来获得有效温度的人,特别是对于贫金属恒星,我们推荐我们的校准。

英文摘要:

We present a new implementation of the infrared flux method (IRFM) using the 2MASS catalogue. We compute the theoretical quantities in the 2MASS JHKs filters by integrating theoretical fluxes computed from ATLAS models, and compare them directly with the observed 2MASS JHKs magnitudes. This is the main difference between our implementation of the IRFM and that of Ramirez & Melendez, since to introduce new stars at the lowest metallicities they transform the 2MASS JHKs magnitudes into the TCS photometric system. We merge in our sample the dwarfs stars from Alonso and collaborators with the stars in the sample of Ramirez & Melendez, Casagrande et al., Christlieb et al. and Bonifacio et al. The final number of stars in our sample is 555 dwarf and subgiant field stars, and 264 giant field stars. We derive a new bolometric flux calibration using the available Johnson-Cousins UBVRI and the 2MASS JHKs photometry. We also compute new Teff versus colour empirical calibrations using our extended sample of stars. We derive effectives temperatures for almost all the stars in the Alonso et al. sample and find that our scales of temperature are hotter by ~64K(dT=104K,N=332 dwarfs) and ~54K(dT=131K,N=202 giants). The same comparison with the sample of Ramirez & Melendez for stars with [Fe/H]<-2.5 provides a difference of ~-87K(dT=194K,N=12 dwarfs) and ~61K(dT=62K,N=18 giants). Our temperature scale is slightly hotter than that of Alonso et al. and Ramirez & Melendez for metal-rich dwarf stars but cooler than that of Ramirez & Melendez for metal-poor dwarfs. We have performed a fully self-consistent IRFM in the 2MASS photometric system. For those who wish to use 2MASS photometry and colour-temperature calibrations to derive effective temperatures, especially for metal-poor stars, we recommend our calibrations.

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