Two-temperature Radiative Hot Accretion Flow around Neutron Stars
Abstract
Numerical simulations of radiative two-temperature hot accretion flows (HAFs) around Neutron stars (NSs) are performed. We assume that all of the energy carried by the HAF around a NS will be thermalized and radiated out at the surface of the NS. The thermal photons will propagate outwards radially and cool the HAF via Comptonization. We define $\dot{m}$ as the mass accretion rate at the surface of the central object in unit of Eddington accretion rate ( ${\dot{M}}_{\mathrm{Edd}}=10{L}_{\mathrm{Edd}}/{c}^{2}$ , with LEdd and c being Eddington luminosity and speed of light, respectively). When $\dot{m}$ is lower than ∼10-4, the cooling of the HAF is not important and outflows are very strong. When $\dot{m}\gt \sim {10}^{-3}$ , cooling becomes important and outflows are significantly weak. In the range ${10}^{-4}\lt \dot{m}\lt {10}^{-3}$ , the HAFs transients from a strong outflow phase to a very weak outflow phase with increase of $\dot{m}$ . The properties of the HAF around a NS are also compared with those of the HAF around a BH. We find that with a similar $\dot{m}$ , the dynamical properties of the HAF around a NS are quite similar as those of the HAF around a BH. However, the emitted spectrum of a HAF around a NS can be quite different from that of a HAF around a BH due to the presence of a thermal soft X-ray component coming from the surface of the NS.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2020
- DOI:
- 10.3847/1538-4357/ab6d02
- arXiv:
- arXiv:2001.05612
- Bibcode:
- 2020ApJ...890..116B
- Keywords:
-
- Black hole physics;
- Neutron stars;
- Low-mass x-ray binary stars;
- Compact objects;
- Accretion;
- 159;
- 1108;
- 939;
- 288;
- 14;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 12 pages, 4 figures, accepted by ApJ