Anisotropic Ejecta Distribution of Kilonova AT 2017gfo
Observed light curves of AT 2017gfo together with our best fit results.
Collaborators: Chengjiang Yin, Binbin Zhang and Zigao Dai
Assuming the mass distribution of the ejecta is anisotropic, we built an analytic model to fit the multi-wavelength data of AT 2017gfo, which is associated with gravitational wave GW 170817. Our fitting results show that the observed data are consistent with the emission from a uniformly expanding ejecta with its mass and opacity anisotropically distributed with jet angle. The distribution of mass, velocity and opacity as a function of jet angle can be described by a cut-off powerlaw with different indexes.
The total mass of the ejecta is $M_{total} = 0.081~M_{\odot}$. The derived velocity of the ejecta is $v_{ej} \sim 0.27~c$ and the opacity $\kappa$ ranges from $4.2~\mathrm{cm^2 g^{−1}}$ to $18~\mathrm{cm^2 g^{−1}}$, both consistent with the results from the numerical simulations in previous works. Our results suggest that the ejecta radiation from the polar region will dominate over the equatorial region at both early and late times due to the anisotropic structure and viewing angle effect. We also show that relativistic Doppler effect and equal-arrival-time surface play an important role in shaping the observed kilonova light curve due to the high speed of ejecta.
If you are interested, our paper is available here.
