2013/02/28 by A. Bauswein, S. Goriely, H. -T. Janka · 1 citation
Physics and Astronomy · #astro-ph.SR
paper · pdf · doi:10.1088/0004-637x/773/1/78
24 pages, 13 figures, accepted for publication in ApJ
arxiv created 2013/06/21 · arxiv updated 2015/06/15
We investigate systematically the dynamical mass ejection, r-process nucleosynthesis, and properties of electromagnetic counterparts of neutron-star (NS) mergers in dependence on the uncertain properties of the nuclear equation of state (EoS) by employing 40 representative, microphysical high-density EoSs in relativistic, hydrodynamical simulations. The crucial parameter determining the ejecta mass is the radius R1.35 of a 1.35 Msun NS. NSs with smaller R1.35 ("soft" EoS) eject systematically higher masses. These range from ~10-3 Msun to ~10-2 Msun for 1.35-1.35 Msun binaries and from ~5*10-3 Msun to ~2*10-2 Msun for 1.2-1.5 Msun systems (with kinetic energies between ~5*1049 erg and 1051 erg). Correspondingly, the bolometric peak luminosities of the optical transients of symmetric (asymmetric) mergers vary between 3*1041 erg/s and 14*1041 erg/s (9*1041 erg/s and 14.5*1041 erg/s) on timescales between ~2 h and ~12 h. If these signals with absolute bolometric magnitudes from -15.0 to -16.7 are measured, the tight correlation of their properties with those of the merging NSs might provide valuable constraints on the high-density EoS. The r-process nucleosynthesis exhibits a remarkable robustness independent of the EoS, producing a nearly solar abundance pattern above mass number 130. By the r-process content of the Galaxy and the average production per event the Galactic merger rate is limited to 4*10-5/yr (4*10-4/yr) for a soft (stiff) NS EoS, if NS mergers are the main source of heavy r-nuclei. The production ratio of radioactive 232Th to 238U attains a stable value of 1.64-1.67, which does not exclude NS mergers as potential sources of heavy r-material in the most metal-poor stars.