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#### Constraint on the ejecta mass for a black hole-neutron star merger event candidate S190814bv

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##### Citation

Kawaguchi, K., Shibata, M., & Tanaka, M. (2020). Constraint on the ejecta mass
for a black hole-neutron star merger event candidate S190814bv.* The Astrophysical Journal,*
*893*(2): 153. doi:10.3847/1538-4357/ab8309.

Cite as: https://hdl.handle.net/21.11116/0000-0006-68FF-7

##### Abstract

We derive the upper limit to the ejecta mass of S190814bv, a black

hole-neutron star merger candidate, through the radiative transfer simulations

for kilonovae with the realistic ejecta density profile as well as the detailed

opacity and heating rate models. The limits to the ejecta mass strongly depend

on the viewing angle. For the face-on observations ($\le45^\circ$), the total

ejecta mass should be smaller than $0.1\,M_\odot$ for the average distance of

S190814bv ($D=267$ Mpc), while larger mass is allowed for the edge-on

observations. We also derive the conservative upper limits of the dynamical

ejecta mass to be $0.02\,M_\odot$, $0.03\,M_\odot$, and $0.05\,M_\odot$ for the

viewing angle $\le 20^\circ$, $\le 45^\circ$, and for $\le 90^\circ$,

respectively. We show that the iz-band observation deeper than $22$ mag within

$2$ d after the GW trigger is crucial to detect the kilonova with the total

ejecta mass of $0.06\,M_\odot$ at the distance of $D=300$ Mpc. We also show

that a strong constraint on the NS mass-radius relation can be obtained if the

future observations put the upper limit of $0.03\,M_\odot$ to the dynamical

ejecta mass for a BH-NS event with the chirp mass smaller than $\lesssim

3\,M_\odot$ and effective spin larger than $\gtrsim 0.5$.

hole-neutron star merger candidate, through the radiative transfer simulations

for kilonovae with the realistic ejecta density profile as well as the detailed

opacity and heating rate models. The limits to the ejecta mass strongly depend

on the viewing angle. For the face-on observations ($\le45^\circ$), the total

ejecta mass should be smaller than $0.1\,M_\odot$ for the average distance of

S190814bv ($D=267$ Mpc), while larger mass is allowed for the edge-on

observations. We also derive the conservative upper limits of the dynamical

ejecta mass to be $0.02\,M_\odot$, $0.03\,M_\odot$, and $0.05\,M_\odot$ for the

viewing angle $\le 20^\circ$, $\le 45^\circ$, and for $\le 90^\circ$,

respectively. We show that the iz-band observation deeper than $22$ mag within

$2$ d after the GW trigger is crucial to detect the kilonova with the total

ejecta mass of $0.06\,M_\odot$ at the distance of $D=300$ Mpc. We also show

that a strong constraint on the NS mass-radius relation can be obtained if the

future observations put the upper limit of $0.03\,M_\odot$ to the dynamical

ejecta mass for a BH-NS event with the chirp mass smaller than $\lesssim

3\,M_\odot$ and effective spin larger than $\gtrsim 0.5$.