Evolution of Disc Mass and Mass Capture Rate by the Neutron Star

Fig. 3 shows (a) the evolution of the disc mass $M_{\rm d}$ and the mass capture rate by the neutron star, $\dot{M}_{\rm acc}$, over $0 \le t \le 30.02$ and (b) their orbital-phase dependence over $25 \le t \le 30$, where the unit of time is $P_{\rm orb}$. Here, $M_{\rm d}$ is defined as the mass in $0.0878 \le r/a \le 2$ and $\rho_{-11}$ is the base density of the disc normalized by $10^{-11} {\rm g\,cm}^{-3}$. In Fig. 3(b), the horizontal line denotes the averaged mass capture rate by the neutron star. On average, the neutron star captures the disc mass at the rate of $2.07\cdot 10^{-10} \rho_{-11} M_\odot{\rm yr}^{-1}$, which will produce $2.44\cdot 10^{36} \rho_{-11} {\rm erg\,s}^{-1}$ of luminosity if all the material accretes on to the neutron star.

Figure 3: (a) Evolution of the disc mass and the mass capture rate by the neutron star and (b) their orbital-phase dependence. In panel (b), averaging is done over $25 \le t \le 30$, where the unit of time is $P_{\rm orb}$. In each panel, the blue line denotes the mass capture rate $\dot{M}_{\rm acc}$, while the red line denotes the disc mass $M_{\rm d}$, which is defined by the mass in $0.088 \le r/a \le 2$. The horizontal dashed line in panel (b) denotes the mass capture r ate averaged over one orbital period. $\rho_{-11} = \rho_0/10^{-11}{\rm g\,cm}^{-3}$, where $\rho _0$ is the base density of the disc.