We have explored the structure of a hot flow bathed in a general large-scale magnetic field. The importance of outflow and thermal conduction on the self-similar structure of a hot accretion flow has been investigated...We have explored the structure of a hot flow bathed in a general large-scale magnetic field. The importance of outflow and thermal conduction on the self-similar structure of a hot accretion flow has been investigated. We consider the additional 2 2 2 magnetic parameters are the Alfv6n sound speeds in three directions of cylindrical coordinates. In comparison to the accretion disk without winds, our results show that the radial and rotational velocities of the disk become faster, but the disk becomes cooler because of the angular momentum and energy flux which are taken away by the winds. Moreover, thermal conduction opposes the effect of winds and not only decreases the rotational velocity but also in- creases the radial velocity as well as the sound speed of the disk. In addition, we study the effect of the global magnetic field on the structure of the disk. Our numerical re- suits show that all the components of a magnetic field can be important and they have a considerable effect on velocities and vertical structure of the disk.展开更多
The steady equilibrium conditions for a mixed gas of neutrons, protons, electrons, positrons and radiation fields （abbreviated as npe^± gas） with or without external neutrino flux are investigated, and a genera...The steady equilibrium conditions for a mixed gas of neutrons, protons, electrons, positrons and radiation fields （abbreviated as npe^± gas） with or without external neutrino flux are investigated, and a general chemical potential equilibrium equation μn = μp ＋ Cμe is obtained to describe the steady equilibrium at high temperatures （T 〉 10^9 K）. An analytic fitting formula of coefficient C is presented for the sake of simplicity, when neutrinos and antineutrinos are transparent. It is a simple method to estimate the electron fraction for the steady equilibrium npe^± gas that adopts the corresponding equilibrium condition. As an example, we apply this method to the GRB accretion disk and confirm that the composition in the inner region is approximately in equilibrium when the accretion rate is low. For the case with external neutrino flux, we calculate the initial electron fraction of neutrino-driven wind from the proto-neutron star model M15-l1-r1. The results show that the improved equilibrium condition makes the electron fraction decrease significantly more than the case μn = μp ＋ μe when the time is less than 5s post bounce, which may be useful for r-process nucleosynthesis models.展开更多
Be/X-ray binaries represent a large fraction of high-mass Xray binaries,in which a compact object accretes a dense stellar wind from its Be star companion with a circumstellar disk,therefore emitting X-rays.The compac...Be/X-ray binaries represent a large fraction of high-mass Xray binaries,in which a compact object accretes a dense stellar wind from its Be star companion with a circumstellar disk,therefore emitting X-rays.The compact object is usually a neutron star that observationally appears as an X-ray pulsar.Be/X-ray binaries are able to build an evolutionary connection from primordial binaries with two main-sequence stars to double neutron stars and gravitational wave sources[1].展开更多
文摘We have explored the structure of a hot flow bathed in a general large-scale magnetic field. The importance of outflow and thermal conduction on the self-similar structure of a hot accretion flow has been investigated. We consider the additional 2 2 2 magnetic parameters are the Alfv6n sound speeds in three directions of cylindrical coordinates. In comparison to the accretion disk without winds, our results show that the radial and rotational velocities of the disk become faster, but the disk becomes cooler because of the angular momentum and energy flux which are taken away by the winds. Moreover, thermal conduction opposes the effect of winds and not only decreases the rotational velocity but also in- creases the radial velocity as well as the sound speed of the disk. In addition, we study the effect of the global magnetic field on the structure of the disk. Our numerical re- suits show that all the components of a magnetic field can be important and they have a considerable effect on velocities and vertical structure of the disk.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10733010, 10673010 and 10573016)the National Basic Research Program of China (2009CB824800)+2 种基金the Scientific Research Funds of Sichuan Provincial Education Department (10ZC014, 2009ZB087)China West Normal University(09A004)Graduate Innovation Funds of USTC
文摘The steady equilibrium conditions for a mixed gas of neutrons, protons, electrons, positrons and radiation fields （abbreviated as npe^± gas） with or without external neutrino flux are investigated, and a general chemical potential equilibrium equation μn = μp ＋ Cμe is obtained to describe the steady equilibrium at high temperatures （T 〉 10^9 K）. An analytic fitting formula of coefficient C is presented for the sake of simplicity, when neutrinos and antineutrinos are transparent. It is a simple method to estimate the electron fraction for the steady equilibrium npe^± gas that adopts the corresponding equilibrium condition. As an example, we apply this method to the GRB accretion disk and confirm that the composition in the inner region is approximately in equilibrium when the accretion rate is low. For the case with external neutrino flux, we calculate the initial electron fraction of neutrino-driven wind from the proto-neutron star model M15-l1-r1. The results show that the improved equilibrium condition makes the electron fraction decrease significantly more than the case μn = μp ＋ μe when the time is less than 5s post bounce, which may be useful for r-process nucleosynthesis models.
文摘Be/X-ray binaries represent a large fraction of high-mass Xray binaries,in which a compact object accretes a dense stellar wind from its Be star companion with a circumstellar disk,therefore emitting X-rays.The compact object is usually a neutron star that observationally appears as an X-ray pulsar.Be/X-ray binaries are able to build an evolutionary connection from primordial binaries with two main-sequence stars to double neutron stars and gravitational wave sources[1].
