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arXiv 1809.07352astro-ph.SRastro-ph.GA
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Gaia DR2 F/1O双模造父变星的Milky Way金属丰度梯度

Milky Way metallicity gradient from Gaia DR2 F/1O double-mode Cepheids

Bertrand Lemasle, Gergely Hajdu, Valery Kovtyukh, Laura Inno, Eva. K. Grebel, Márcio Catelan, Giuseppe Bono, Patrick François, Alexei Kniazev, Ronaldo da Silva, Jesper Storm

摘要:

混合模式造父变星的第一泛音(1 O)/基本(F)周期之比(F/1 O)与金属度有关。因此,它可以用来描述拥有这种变星的系统。我们想利用Gaia DR 2星表中的F/1 O双模造父变星来计算银河系盘的金属丰度梯度。金属丰度是由盖亚DR 2提供的第一泛音和基本周期的比值得出的,而盖亚DR 2的周期则用于确定恒星的银心距离。从光变曲线的视觉检查,它原来是银河系的F/1 O双模造父变星在盖亚DR 2的大部分(77%)是虚假的检测。盖亚DR 2提供了3个新的真正的F/1 O造父变星。将它们与目前已知的F/1 O造父变星相结合,并使用整个样本的盖亚DR 2弛豫,我们可以推导出银河系盘中的金属丰度梯度。我们发现使用自助法的斜率为-0.045 $\pm$ 0.007 dex/kpc,使用总最小二乘法的斜率为-0.040 $\pm$ 0.002 dex/kpc。这些结果与先前基于典型造父变星的[Fe/H]梯度的测定结果吻合得很好。F/1 O造父变星的周期比可以可靠地确定银河系中的金属丰度梯度,反过来,在其他系统中,通过经典的光谱方法很难达到。

英文摘要:

The ratio of the first overtone (1O) / fundamental (F) periods of mixed-mode Cepheids that pulsate simultaneously in these two modes (F/1O) is metallicity-dependent. It can therefore be used to characterize the systems that host such variable stars. We want to take advantage of the F/1O double-mode Cepheids listed in the Gaia DR2 catalogue to derive the metallicity gradient in the Milky Way disk. The metallicity is derived from the ratio of the first overtone and fundamental periods provided by Gaia DR2 while the Gaia DR2 parallaxes are used to determine the Galactocentric distances of the stars. From a visual inspection of the light curves, it turns out that a large fraction (77%) of the Galactic F/1O double-mode Cepheids in Gaia DR2 are spurious detections. Gaia DR2 provides 3 new bona fide F/1O Cepheids. Combining them with the currently known F/1O Cepheids and using the Gaia DR2 parallaxes for the entire sample, we can derive the metallicity gradient in the Milky Way disk. We find a slope of -0.045$\pm$0.007 dex/kpc using a bootstrap method, and of -0.040$\pm$0.002 dex/kpc using a total least squares method. These results are in good agreement with previous determinations of the [Fe/H] gradient in the disk based on canonical Cepheids. The period ratio of F/1O Cepheids allows for a reliable determination of the metallicity gradient in the Milky Way, and in turn, in other systems that would be difficult to reach via classical spectroscopic methods.

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。

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