内容：冷星是致密天体的伴星，已知它们的锂丰度比同光谱类型的场星高，场星的锂丰度严重不足。这可能是由于在这些系统中的Li生产或Li保存。目的：测量中子星X射线双星岑X-4伴星的锂同位素比值。方法：利用2000年和2004年获得的眼眶周围的UVES光谱。用频谱合成技术分析了频谱，用蒙特卡罗模拟估计了误差。结果：在68%置信水平下，测得A（Li）=2.87 ± 0.20，6Li/7 Li = 0.12 ± 0.08-0.05。我们还提出了更新的系统参数，精确地确定了轨道周期和组分质量，即中子星和伴星的质量分别为1.14+-0.45 Msun和0.23+-0.10 Msun。结论：在我们看来，低水平的6Li有利于Li保存方案，虽然不能排除Li生产机制。在保存的情况下，没有Li是在双星系统中新产生的，但是潮汐锁定的伴星通过某种机制保存了它原来的Li，可能是由于它的快速旋转而抑制了破坏。
英文摘要：
Context: Cool stars, companions to compact objects, are known to show Li abundances which are high compared to field stars of the same spectral type, which are heavily Li depleted. This may be due either to Li production or Li preservation in these systems. Aims: To measure the lithium isotopic ratio in the companion star of the neutron star X-ray binary Cen X-4. Method: We use UVES spectra obtained in years 2000 and 2004 around the orbital quadratures. The spectra are analysed with spectrum synthesis techniques and the errors estimated with Monte Carlo simulations. Results: We measure A(Li)=2.87+-0.20 and 6Li/7Li = 0.12+0.08-0.05 at 68% confidence level. We also present updated system parameters with a refined determination of the orbital period and component masses i.e. 1.14+-0.45 Msun and 0.23+-0.10 Msun for the neutron star and companion, respectively. Conclusions: In our view the low level of 6Li favours Li preservation scenarios, although Li production mechanisms cannot be ruled out. In the case of preservation, no Li is freshly created in the binary, but the tidally-locked companion has preserved its original Li by some mechanism, possibly inhibited destruction due to its fast rotation.
Dynamically Influenced Molecular Clouds in the Nucleus of NGC 6946: Variations in the CO Isotopic Line Ratios
We present high resolution (~5'') maps of the J = 1 - 0 transitions of ^{13}CO and C^{18}O towards the nucleus of NGC 6946, made with the Owens Valley Millimeter Array. The images are compared with existing ^{12}CO(1-0) maps to investigate localized changes in gas properties across the nucleus. As compared to ^{12}CO, both ^{13}CO and C^{18}O are more confined to the central ring of molecular gas associated with the nuclear star formation; that is, ^{12}CO is stronger relative to ^{13}CO and C^{18}O away from the nucleus and along the spiral arms. The ^{12}CO(1-0)/^{13}CO(1-0) line ratio reach…
High-precision elements of double-lined spectroscopic binaries from combined interferometry and spectroscopy. Application to the beta Cephei star beta Centauri
