| 其他摘要 | Compact objects are the products of the end stages of stellar evolution. The studies for the accretion onto compact stars has promoted the understanding of the physical processes under extreme physical conditions, and also provided important constraints for the evolution of binaries, such as the angular momentum loss mechanisms, the common-envelope evolution and the mass-accretion process of compact objects, etc. In addition, many special objects can be formed through the accretion onto compact stars, such as the X-ray binaries, pulsars, supernovae and cataclysmic variables, etc., which are ideal astrophysics laboratories. However, the evolution history of compact stars and the origin of related objects have not been completely resolved, such as the accretion disc, magnetic braking, accretion efficiency, and the final evolutionary outcomes of compact stars, etc.In this paper, we introduced the research background and status of the accretion onto compact stars, and the accretion physics and related objects in details. We have carried out a series of work on the accreting white dwarf (WD) and accreting neutron star (NS). We explained the origin of black widows (BWs) with companion masses<0.01𝑀⊙through ultracompact X-ray binaries with He star companions, and provided a channel for the formation of isolated millisecond pulsars (MSPs). We studied the Type Ia supernovae (SNe Ia) in NS+He star binaires and gave the parameter space for the formation of SNe Ia through this channel, and provided an explanation for the isolated mildly recycled pulsars. We studied the electron-capture supernovae (EC-SNe) in NS+He star binaires and gave the parameter space for the formation of EC-SNe through this channel, and gave the characteristics of double neutron stars (DNSs) originating from EC-SN channel. We developed a method to measure the WD-mixing fraction in classical novae, and explained the helium enrichment in the nova ejecta. We studied the characteristics of He-flashes on the surface of oxygen-neon (ONe) WDs, and provided the input parameters for the population synthesis studies. The main research results we obtained are as follows:(1) We explained the origin of BWs with companion masses (M_2) < 0.01𝑀⊙, and provided a formation channel for the isolated MSPs.BWs are a type of eclipsing millisecond pulsars (MSPs) with M_2<0.05𝑀⊙. Recent observations indicate that there are two subtypes of BWs. One is the BWs with M_2=0.01-0.05𝑀⊙, whereas another with M_2<0.01𝑀⊙. However, the origin of the latter is still highly uncertain. We investigated the formation of BWs with M_2<0.01𝑀⊙ through ultra-compact X-ray binaries (UCXBs) with He star companions, in which a neutron star (NS) accretes material from a He star through Roche-lobe overflow. Our channel can explain the formation of the BWs with M_2<0.01𝑀⊙ within the Hubble time, especially three widely studied BWs, i.e. PSRs J1719-1438, J2322-2650 and J1311-3430. We found that X-ray irradiation feedback does not affect the evolutionary tracks of evaporation process. We also found that the UCXB channel with He star companions are the potential progenitors of isolated MSPs. In addition, the origin of BWs with M_2<0.01𝑀⊙ is different with another sub-type of BWs, and the BWs with M_2<0.01𝑀⊙ may not be produced by redback systems.(2) We studied the SNe Ia in NS+He star binaires and gave the parameter space for the formation of SNe Ia through this channel, and provided an explanation for the isolated mildly recycled pulsars.SNe Ia are generally thought to originate from thermonuclear explosions of carbon-oxygen white dwarfs in close binaries. However, the observed diversity among SNe Ia implies that they have different progenitor models. We performed the long-term evolution of NS+He star binaries with different initial He star masses (M_He) and orbital periods (P_orb) for the first time, in which the He star companions can explode as SNe Ia eventually. Our simulations indicate that after the He stars develop highly degenerate oxygen-neon (ONe) cores with masses from 1.335-1.385𝑀⊙, explosive oxygen burning can be triggered due to the ignition of central residual carbon. According to these calculations, we obtained an initial parameter space for the production of SNe Ia in the logP_orb-M_He plane. Meanwhile, we found that isolated mildly recycled pulsars can be formed after He stars explode as SNe Ia in NS+He star binaries, in which the isolated pulsars have minimum spin periods of ~30-110ms, and space velocity of<360km/s.(3) We studied the electron-capture supernovae (EC-SNe) in NS+He star binaires and gave the parameter space for the formation of EC-SNe through this channel, and gave the characteristics of double neutron stars (DNSs) originating from EC-SN channel.Electron-capture supernovae (EC-SNe) are induced by the e-capture on Ne20 in the strongly degenerate oxygen-neon (ONe) cores with masses close to the Chandrasekhar limit (M_Ch). We simulated NS+He star binaries with different initial He star masses (M_He) and orbital periods (P_orb), and considered the explosive oxygen burning that may occur in the ONe core. We provided the initial parameter spaces for producing EC-SNe in the logP_orb-M_He diagram, and found that both M_He and P_orb for EC-SNe increase with metallicity. Then, by considering NS kicks added to the newborn NS, we investigated the properties of DNS systems after the He star companions collapse into NSs. We found that most of the observed DNS systems can be produced by relatively small NS kicks (<80km/s). We also gave the properties of the pre-SN systems of the observed DNS systems, and found that the majority of the observed DNS systems appear to have tight pre-SN orbit (<1d).(4) We developed a method to measure the WD-mixing fraction in classical novae, and explained the helium enrichment in the nova ejecta. Classical novae are powered by thermonuclear runaways occurring on the surface of accreting WDs.In the observations, the enrichments of helium and heavy elements in nova ejecta have been detected, indicating the existence of a mixing process between the accreted matter and the matter from the outer layers of the underlying WDs prior to nova outbursts. However, the mixing fraction in classical novae is still uncertain. By considering different WD-mixing fractions and WD masses, we carried out a series of simulations of nova outbursts. We identified four elemental abundance ratios that can be used to determine the WD-mixing fraction, and a higher metallicity in ejecta prefers to be accompanied by a lower WD mass. In addition, By considering the mixing process between the accreted material and the He-rich envelope, we explained the helium enrichment in the nova ejecta, and found that He-mixing leads to more violent classical nova outbursts.(5) We studied the characteristics of He-flashes on the surface of oxygen-neon (ONe) WDs.It has been suggested that ONe WDs can increase their mass to the Chandrasekhar limit by multiple He-shell flashes, leading to accretion induced collapse (AIC) events. However, the properties of He-shell flashes on the surface of ONe WDs are still not well understood. We investigated the long-term evolution of ONe WDs accreting He-rich material with different WD masses and constant mass-accretion rates. We found that the mass-retention efficiency increases with the ONe WD mass and the mass-accretion rate, whereas both the nova cycle duration and the ignition mass decrease with the ONe WD mass and the mass-accretion rate. We also present the nuclear products in different accretion scenarios. In additon, by considering the mixing process between the accreted matter and the WD matter, we also gave the characteristics of the nova outbursts in the mixed model. The results presented in this article can be used in the future binary population synthesis studies of AIC events. |
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