Observational Constraints on the Lifetime of Cometary H2O
Observational Constraints on the Lifetime of Cometary H2O
复制标题
彗星水寿命的观测限制
DOI：
10.1006/icar.1993.1121
复制
发表时间：
1993
期刊：
影响因子：
3.2
通讯作者：
D. Schleicher
中科院分区：
文献类型：
--
作者：
A. Cochran;D. Schleicher
摘要我们利用一组精心挑选的五颗彗星的观测数据沿着矢量模型和Haser模型，探讨了彗星彗星中H2O和OH的光解寿命。本文所述的测光和长缝CCD数据是专门为该项目获得的，而IUE数据是存档的。基本的参数空间进行了检查，我们的知识等因素的外流和喷射速度进行了讨论。我们的结论是，这是很难限制的OH的寿命，但H2 O的寿命必须依赖于太阳紫外线通量的变化。我们的数据是一致的预期，随着太阳活动，从而紫外线通量，增加，水的寿命减少。从我们的数据中，我们表明H2 O和OH的组合理论寿命与数据没有产生良好的拟合;因此，至少有一组理论寿命肯定是错误的。我们的数据需要更短的H2O寿命和/或更短的OH寿命。我们提出了一些有用的关系，以确定哪些寿命和速度用于未来的应用。此外，我们已经得到了改进的寿命和规模长度使用计算生产率与简单的模型。新的母星寿命和标度长度比忽略太阳活动影响的常用值短约15-45%。最后，我们讨论了未来需要哪些数据类型来更好地建模彗星数据。
Abstract We used a carefully selected set of observations of five comets along with a vectorial model and the Haser model to explore the lifetimes against photodissociation of H 2 O and OH in cometary comae. The photometric and long-slit CCD data described in this paper were obtained specifically for this project, while the IUE data are archival. The underlying parameter space was examined and our knowledge of such factors as the outflow and ejection velocities is discussed. We conclude that it is difficult to constrain the lifetime of OH but that the H 2 O lifetimes must be dependent on changes in the solar UV flux. Our data are consistent with the expectation that as the solar activity, and thus UV flux, increases, the H 2 O lifetimes decrease. From our data, we show that the combined theoretical lifetimes for H 2 O and OH do not produce good fits to the data; thus, at least one set of theoretical lifetimes must be in error. Our data require shorter H 2 O lifetimes and/or shorter OH lifetimes. We present some useful relations for determining which lifetimes and velocities to use for future applications. Additionally, we have derived improved lifetimes and scale lengths for use computing production rates with simple models. The new parent lifetimes and scale lengths are about 15-45% shorter than commonly used values which ignore effects due to solar activity. Finally, we discuss what data types are needed in the future to enable better modeling of cometary data.