论文标题
HE 0107 $ - $ 5240和其他CEMP-NO星星的意式浓缩咖啡观察结果$ \ rm [fe/h] \ le -4.5 $
Espresso observations of HE 0107$-$5240 and other CEMP-no stars with $\rm [Fe/H]\le -4.5$
论文作者
论文摘要
HE 0107 $ - $ 5240是一颗超贫困的星星，$ \ rm [fe/h] = -5.39 $。我们在VLT上使用浓缩板光谱仪进行了高分辨率观察，以限制二元系统He 0107 $ -5240的运动学特性，并探测了8个最具金属贫困星的二进制性，该样本具有$ \ rm [fe/h] <-4.5 $的$ \ rm [fe/h] <-4.5 $。径向速度是通过在4200 $ -4315a的间隔中使用互相相关获得的，该速度包含强C频段，该速度在迭代过程中与模板相对。通过使用浓缩咖啡测量值和文献中的其他方法，应用了贝叶斯方法来计算轨道。还通过光谱合成在HE0107 $ - $ 5240中进行了化学分析。 HE 0107 $ - $ 5240的观察结果超过3年，显示了径向速度的单调降低趋势，速度大约降低0.5 ms $^{ - 1} $ d $^{ - 1} $。该周期在$ p _ {\ rm orb} = 13009 _ { - 1370}^{+1496} $ d。已经发现了几个元素的新的更严格的上限：a）[sr/fe]和[ba/fe]分别低于$ -0.76 $和$+0.2 $，确认星星是cemp-no； b）$ a（li）<0.5 $远低于高原$ a（li）= 1.1 $ $ a（li）= 1.1 $，这表明李最初是耗尽的； c）同位素比$^{12} $ c/$^{13} $ c是87 $ \ pm6 $显示出非常低的$^{13} $ c与Spinstar祖先的期望相反。我们确认他0107 $ - $ 5240是二进制恒星，长时间约为13000d（$ \ sim36 $年）。碳同位素比不包括同伴经过AGB阶段并将质量转移到当前观察到的星星的可能性。 HE 0107 $ - $ 5240的二进制性意味着在多个系统中形成的第一代低质量恒星，并表明低金属性并不排除二进制的形成。最后，在SMSS 1605 $ - $ 1443中也发现了$ v_ {rad} $变化的可靠指示。
HE 0107$-$5240 is a hyper metal-poor star with $\rm [Fe/H]=-5.39$. We performed high-res observations with the ESPRESSO spectrograph at the VLT to constrain the kinematical properties of the binary system HE 0107$-$5240 and to probe the binarity of the sample of 8 most metal-poor stars with $\rm [Fe/H]<-4.5$. Radial velocities are obtained by using cross-correlation in the interval 4200$-$4315A, which contains the strong CH band, against a template in an iterative process. A Bayesian method is applied to calculate the orbit by using the ESPRESSO measurements and others from the literature. A chemical analysis has also been performed in HE0107$-$5240 by means of spectral synthesis. Observations of HE 0107$-$5240 spanning more than 3 years show a monotonic decreasing trend in radial velocity at a rate of approximately by 0.5 ms$^{-1}$d$^{-1}$. The period is constrained at $P_{\rm orb} = 13009_{-1370}^{+1496}$d. New more stringent upper-limits have been found for several elements: a)[Sr/Fe] and [Ba/Fe] are lower than $-0.76$ and $+0.2$ respectively, confirming the star is a CEMP-no; b)$A(Li)< 0.5$ is well below the plateau at $A(Li)=1.1$ found in the Lower Red Giant Branch stars, suggesting Li was originally depleted; and c)the isotopic ratio $^{12}$C/$^{13}$C is 87$\pm6$ showing very low $^{13}$C in contrast to what expected from a spinstar progenitor. We confirm that HE 0107$-$5240 is a binary star with a long period of about 13000d ($\sim36$ years).The carbon isotopic ratio excludes the possibility that the companion has gone through the AGB phase and transferred mass to the currently observed star. The binarity of HE 0107$-$5240 implies some of the first generations of low-mass stars form in multiple systems and indicates that the low metallicity does not preclude the formation of binaries. Finally, a solid indication of $v_{ rad}$ variation has been found also in SMSS 1605$-$1443.
