非表示:
キーワード:
General Relativity and Quantum Cosmology, gr-qc, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
要旨:
We present new (3+1)D numerical relativity simulations of the binary neutron
star (BNS) merger and postmerger phase. We focus on a previously inaccessible
region of the binary parameter space spanning the binary's mass-ratio
$q\sim1.00-1.75$ for different total masses and equations of state, and up to
$q\sim2$ for a stiff BNS system. We study the mass-ratio effect on the
gravitational waves (GWs) and on the possible electromagnetic emission
associated to dynamical mass ejecta. We compute waveforms, spectra, and
spectrograms of the GW strain including all the multipoles up to $l=4$. The
mass-ratio has a specific imprint on the GW multipoles in the
late-inspiral-merger signal, and it affects qualitatively the spectra of the
merger remnant. The multipole effect is also studied by considering the
dependency of the GW spectrograms on the source's sky location. Unequal mass
BNSs produce more ejecta than equal mass systems with ejecta masses and kinetic
energies depending almost linearly on $q$. We estimate luminosity peaks and
light curves of macronovae events associated to the mergers using a simple
approach. For $q\sim2$ the luminosity peak is delayed for several days and can
be up to four times larger than for the $q=1$ cases. The macronova emission
associated with the $q\sim2$ BNS is more persistent in time and could be
observed for weeks instead of few days ($q=1$) in the near infrared. Finally,
we estimate the flux of possible radio flares produced by the interaction of
relativistic outflows with the surrounding medium. Also in this case a large
$q$ can significantly enhance the emission and delay the peak luminosity.
Overall, our results indicate that BNS merger with large mass ratio have EM
signatures distinct from the equal mass case and more similar to black hole -
neutron star binaries.
