长期以来,疏散星团成员星的证认问题一直是天文学领域的一个挑战,由于疏散星团形成及演化的复杂性,没有统一的方法能准确地确定疏散星团中的成员星.目标是以3种不同空间分布类型的疏散星团为样本,选取恒星的位置和运动的五维参数,通过DB...长期以来,疏散星团成员星的证认问题一直是天文学领域的一个挑战,由于疏散星团形成及演化的复杂性,没有统一的方法能准确地确定疏散星团中的成员星.目标是以3种不同空间分布类型的疏散星团为样本,选取恒星的位置和运动的五维参数,通过DBSCAN(Density-Based Spatial Clustering of Applications with Noise)、FOF(Friend of Friend)和STAR GO(Star's Galactic Origin)3种聚类方法,对疏散星团进行聚类检测,量化不同算法的绩效.研究结果表明,FOF与STAR GO算法对有特殊结构的星团更为适用,能识别出星团的潮汐或延展结构,而DBSCAN对星团核心区域成员星的识别更为完整.旨在星团结构细节与提高成员星识别的完整性之间找到更均衡的算法策略.展开更多
Using the stellar evolution code MESA,we mimic the negative jet feedback mechanism in common envelope evolution(CEE)of low-mass main sequence stars,M_(2)?0.1-0.2M_(☉),spiraling inward inside the envelopes of asymptot...Using the stellar evolution code MESA,we mimic the negative jet feedback mechanism in common envelope evolution(CEE)of low-mass main sequence stars,M_(2)?0.1-0.2M_(☉),spiraling inward inside the envelopes of asymptotic giant branch or red giant branch stars and find that the jets reduced the envelope density,and therefore the jets'power,by a factor ofχ≈0.5(M_(2)/0.1M_(☉))^(-1).We mimic the energy that the jets deposit into the envelope by depositing energy into the outer envelope,a process that inflates the envelope,therefore reducing the density in the vicinity of the main sequence star,the accretion rate,and the jets'power.In deriving this expression for the negative jet feedback coefficientχ,we assume that the actual mass accretion rate is a fractionξ≈0.2-0.5 of the classical Bondi-Hoyle-Lyttleton mass accretion rate and that the jets carry a fractionη≈0.25-0.5 of the accretion energy onto the main sequence star.Our study is another step in establishing the major role of jets in the onset and early phase of CEE,a possible grazing envelope evolution phase,and in transient events,such as luminous red novae,which these processes can power.展开更多
文摘长期以来,疏散星团成员星的证认问题一直是天文学领域的一个挑战,由于疏散星团形成及演化的复杂性,没有统一的方法能准确地确定疏散星团中的成员星.目标是以3种不同空间分布类型的疏散星团为样本,选取恒星的位置和运动的五维参数,通过DBSCAN(Density-Based Spatial Clustering of Applications with Noise)、FOF(Friend of Friend)和STAR GO(Star's Galactic Origin)3种聚类方法,对疏散星团进行聚类检测,量化不同算法的绩效.研究结果表明,FOF与STAR GO算法对有特殊结构的星团更为适用,能识别出星团的潮汐或延展结构,而DBSCAN对星团核心区域成员星的识别更为完整.旨在星团结构细节与提高成员星识别的完整性之间找到更均衡的算法策略.
文摘Using the stellar evolution code MESA,we mimic the negative jet feedback mechanism in common envelope evolution(CEE)of low-mass main sequence stars,M_(2)?0.1-0.2M_(☉),spiraling inward inside the envelopes of asymptotic giant branch or red giant branch stars and find that the jets reduced the envelope density,and therefore the jets'power,by a factor ofχ≈0.5(M_(2)/0.1M_(☉))^(-1).We mimic the energy that the jets deposit into the envelope by depositing energy into the outer envelope,a process that inflates the envelope,therefore reducing the density in the vicinity of the main sequence star,the accretion rate,and the jets'power.In deriving this expression for the negative jet feedback coefficientχ,we assume that the actual mass accretion rate is a fractionξ≈0.2-0.5 of the classical Bondi-Hoyle-Lyttleton mass accretion rate and that the jets carry a fractionη≈0.25-0.5 of the accretion energy onto the main sequence star.Our study is another step in establishing the major role of jets in the onset and early phase of CEE,a possible grazing envelope evolution phase,and in transient events,such as luminous red novae,which these processes can power.
