Dynamical Interaction In The Evolution Of X-ray Binaries

Binary systems are ubiquitous in universe and have attracted the attention of as-tronomers with various observational features and behaviors. Generally speaking, stars in binary are coupled together so that one star may affect its companion and vice versa, the orbital period is an important parameter to judge the strength of binary coupling, but binary interactions such as wind, tidal interactions, matter transfer will change the bi-nary orbital period slowly, which in return, change the coupling and evolution routines and thus the final products of binary evolution.With proper models, one can estimate the influence of binary interactions on the evolution products of binaries. However, some dynamical processes may take place during the binary evolution, which will change the binary properties greatly and abruptly, and always in a random manner. This paper is focus on these dynamical processes that probably happen in binaries, we will briefly introduce them in the follows:In Chapter 1,we give a brief review on the basic knowledge of binary systems and binary evolution, which include the observational features of main sequence binaries and X-ray binaries, binary interactions and mechanisms of binary angular momentum lose, evolution of main sequence binaries to X-ray binaries.In Chapter 2, we introduce two kinds of dynamical processes that probably hap-pen in binaries. The first is the supernova of a massive star, which may change the binary orbit via the sudden lose of mass, a Kick velocity to the newborn neutron star and the direct impact on the companion stars by supernova ejecta. Second, the dynam-ical encounters of binaries in Globular Clusters, which may lead to the exchange of intruder with binary components, and the change of binary bounding energy (Eb) after encounters. Generally, the change of binary bounding energy during binary-single star interactions can be described with the Hills-Heggie Law, which states that hard binaries {Eb> Ek) will lose energy and evolve into smaller orbits, while soft binaries (Eb< Ek ) absorb energy from intruder and tend to be softer and even disrupted.In Chapter 3, we investigate the pulsar spin and orbital period distributions in Be/X-ray binaries. Be/X-ray binaries are relics of binary supernovae and the supernova-induced eccentric orbits are well preserved, therefore, they are ideal laboratories to study supernovae and neutron star kick. Two population of Be/X-ray binaries have been detected in the Corbet diagram, where both the pulsar spin period and orbital period are bimodal distributed. A model to explain the bimodal distribution of Be/X-ray binaries is the two types of supernovae model——electron-capture supernovae may impart a smaller kick velocity (vkick(?)50 km s-1) to newborn neutron star, which may result in a lower orbital period and smaller eccentricity for the Be/X-ray binaries, while neutron star created by iron-core-supernova may have much larger kick (vkick(?)200 km s-1), which may lead to a much larger orbital period and higher eccentricity in Be/X-ray binaries. However, the spin period of pulsars in X-ray binaries are affected by the binary mass transfer processes, which will erase the pulsar spin periods inherited from supernovae. By studying the interactions between neutron star and Be star disk in Be/X-ray binaries, and the related X-ray activities in outbursts, we suggest that the bimodal spin period distribution in Be/X-ray binaries is related to two types of accretion modes rather than two types of supernovae.In Chapter 4, we study the abundance of low-luminosity X-ray sources in Galac-tic Globular Clusters (GCs). It is well-known that the abundance of Low-Mass X-ray Binaries (LMXBs) and Millisecond Pulsars (MSPs) are orders of magnitude larger in GCs than in the Galactic field, which have been attributed to the efficiently formation of close binaries in GCs by stellar dynamical interactions.However, it remains an open question of whether there are over-abundant of cataclysmic variables (CV) and coro-nally active binaries (AB) in GC than in the field. Based on the archival Chandra data accumulated in the past fifteen years, we study the X-ray emission of low-luminosity X-ray sources in 69 Galactic GCs, we find that the cumulative X-ray emissivities of low-luminosity X-ray sources in most GCs are lower than that of stars in the solar neighborhood and the Local Group dwarf elliptical galaxies, which indicates an under- abundance of low-luminosity X-ray sources such as CVs and ABs in GCs. We suggest that most primordial binaries have been dynamically disrupted in GCs before they can evolve into CVs and ABs.In Chapter 5, we study the dynamical formation of X-ray sources in GCs. Al-though many primordial binaries have been dynamically disrupted in GCs, we found that hard main sequence binaries in GCs can be dynamically transformed into X-ray sources, the contribution of the dynamical formation channel could be two orders of magnitude larger than the primordial binary evolution channel.With the abundance of X-ray sources and main sequence binaries, we also confirm the the Hills-Heggie Law observationally, which provide an possible mechanism for the heating of cluster through the dynamical encounters of hard binaries.Finally, we summarize our research results in Chapter 6, and give a brief prospect for our future work.