标题： 彗星 C/2012 F6（莱蒙）和 C/2014 Q2（洛夫乔伊）的 H、C、N、O 和 S 的同位素比值 显示英文标题

标题： Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy)

摘要： 柯伊伯带天体C/2012 F6（莱蒙）和C/2014 Q2（洛夫乔伊）在2013年3-4月和2015年1月的出现，结合亚毫米波段设施观测能力的提升，为我们提供了进行敏感的组成和同位素研究的机会，以研究其彗发中的挥发性物质。 我们在2015年1月13日至26日使用IRAM 30米望远镜观测了彗星洛夫乔伊，并于2015年1月29日至2月3日使用 Odin 亚毫米空间天文台进行了观测。 我们检测到了22种分子及其若干同位素变体。 使用Odin测量得到的H$_2^{16}$O 和 H$_2^{18}$O 生产量呈现出周期性模式，周期为0.94天，振幅约为25%。 彗星洛夫乔伊推断出的同位素比率是$^{16}$O/$^{18}$O = 499$\pm$24 和水中的 D/H = 1.4$\pm$0.4$\times 10^{-4}$，在CS中的$^{32}$S/$^{34}$S = 24.7$\pm$3.5，所有这些都与地球上的值相符。 该比例 $^{12}$C/$^{13}$C = 109 $\pm$ 14在HCN中略高于地球值，而$^{14}$N/$^{15}$N = 145 $\pm$ 12在HCN中是地球比例的一半。 据报道，其他分子中的D/H或12C/13C有几个上限值。 根据我们对彗星C/2014 Q2（Lovejoy）中HDO的观测，我们报告了首个不超过地球值的奥尔特云彗星的D/H比值。 另一方面，在另一个奥尔特云彗星， C/2012 F6（Lemmon）中观测到相同的HDO线，表明D/H值高出四倍。 鉴于之前对彗星水的D/H测量值，这表明即使在同一动力学群组内的彗星中也存在D/H比值和化学成分的多样性，这暗示当前的动力学群组包含了在早期太阳系中形成于不同地点或时间的彗星。 显示英文摘要

摘要： The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30m telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January - 3 February 2015. We detected 22 molecules and several isotopologues. The H$_2^{16}$O and H$_2^{18}$O production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of ~25%. The inferred isotope ratios in comet Lovejoy are $^{16}$O/$^{18}$O = 499 $\pm$ 24 and D/H = 1.4 $\pm$ 0.4 $\times 10^{-4}$ in water, $^{32}$S/$^{34}$S = 24.7 $\pm$ 3.5 in CS, all compatible with terrestrial values. The ratio $^{12}$C/$^{13}$C = 109 $\pm$ 14 in HCN is marginally higher than terrestrial and $^{14}$N/$^{15}$N = 145 $\pm$ 12 in HCN is half the Earth ratio. Several upper limits for D/H or 12C/13C in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.