| 摘要: | 在我的上一個計劃中，我利用iPTF的大量資料來進行小行星時序研究，並使該領域往前推進一大步。在本計畫，我將利用Zwicky Transient Facility (ZTF) 所取得的巨量資料來繼續小行星時序研究(資料量預期比iPTF大一個量級以上，目前有~15,000個自旋週期)。這將有助於小行星內部結構、自旋狀態改變機制、及雙小行星系統形成與演化的研究。在小行星內部結構研究上：(a)持續尋找超快自旋小行星，此類小行星無法被傳統的瓦礫堆結構所解釋，因此確認它們的族群數量與共同特性可了解超快自旋小行星是否是一個有別於一般小行星的族群，這有助於了解小行星內部結構。(b)判別不同成分類別之小行星的自旋極限，可用來計算不同類別小行星的整體密度，是了解小型內部結構的一項重要參數。(c)利用ZTF找到的雙小行星進行估計小行星質量與整體密度。(d)小行星的形狀會因為相互碰撞與自旋而隨時間而演化，該演化與其內部結構有關(有多少孔隙)。不同成分類別、家族(年紀)與所在位置的小行星的形狀分布可提供其內部結構資訊。在自旋狀態改變機制研究上：(a)我將試著找出自旋週期分布於小行星其他特性與參數間的關係，這些參數包含：在主小星帶中的位置，小行星的大小、及軌道參數。這將有助於量化小行星自旋狀態如何被相互碰撞與YORP效應所改變。(b)除了放射線元素定年外，只有小行星家族可以被判定年紀。因此，不同小行星家族的自旋週期分布代表著不同演化程度，這也有助於了解小行星自旋狀態改變機制。在雙小行星系統研究上：利用ZTF的資料，我們可獲得雙小行星的數量比例及主星與伴星的的配置方式，這些資訊將可用來測試不同雙小行星的形成機制。此外，我也將持續監視靠近自旋極限的小行星，期望有機會見證這些小行星發生自旋分裂，該機制是目前最能解釋已知的雙小行星性質。 ;In my previous project, I have shown how asteroid time-series study has been significantly pushed forward by using a large-volume dataset obtained from the iPTF. In this proposal, I will use the Zwicky Transient Facility (ZTF) to obtain a dataset with a volume more than an order of magnitude than the iPTF (i.e., ~15000 asteroid rotation periods) to continue asteroid time-series study. This will help to investigate asteroid interior structure, constrain the mechanisms of spin-status alteration, and study binary asteroid formation and evolution.For asteroid interior structure study:(a) Looking for super-fast rotators (SFRs, a group of asteroid cannot be explained by the traditional "rubble-pile" structure), which can constrain their population size and study their common properties. This will help to tell whether SFRs are a special group beside the average asteroids.(b) The spin-rate limits for different taxonomic type asteroids. This can help to study asteroid interior structure in terms of surveying their bulk densities.(c) Mass/bulk density can also be estimate using the binary asteroids discovered by the ZTF.(d) The shape distributions for asteroids of different taxonomies, families (ages), and locations in the main asteroid belt. Asteroid shape would evolved due to collision and spin, which depends on their interior structure (i.e., how strong and porous). Therefore, the shape distribution can provide information of their interior structures.For mechanisms of spin-status alteration:(a) I will try to correlate the spin-rate distribution with other properties or parameters, e.g., location in main asteroid belt, asteroid size, orbital parameters. This will help to quantify how asteroid spin status is affected by mutual collision and the YORP effect.(b) Except for the radioactive dating, asteroid age can only be determined via asteroid families. Therefore, the spin-rate distributions of different asteroid families represents different degrees of evolution, which can also help to study the mechanisms of spin-status alteration.(c) If the Slivan state (i.e., spin-vector alignment) presents in an asteroid family, we would see rotation period clustering of its members. With the ZTF data set, we are able to conduct this study for most asteroid families. For binary formation and evolution:The binary fraction and the configurations of the primary and secondary components of the system can be obtained from the ZTF data set, which be used to test various binary formation theories. Moreover, I will continuously monitor those asteroids close to the spin barrier because we expect to witness rotational fission happening which is the formation model accounting for the observed properties. |
