The impact of r-process heating on the dynamics of neutron star merger accretion disc winds and their electromagnetic radiation

Journal Article · Sat Dec 11 00:00:00 EST 2021 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stab3583· OSTI ID:1855365

Klion, Hannah  ^[1]; Tchekhovskoy, Alexander ^[2]; Kasen, Daniel ^[3]; Kathirgamaraju, Adithan ^[1]; Quataert, Eliot ^[4]; Fernández, Rodrigo ^[5]

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1. Univ. of California, Berkeley, CA (United States)
2. Northwestern Univ., Evanston, IL (United States). Center for Interdisciplinary Exploration & Research in Astrophysics (CIERA)
3. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
4. Princeton Univ., NJ (United States)
5. Univ. of Alberta, Edmonton, AB (Canada)

Neutron star merger accretion discs can launch neutron-rich winds of >10^-2M⊙. This ejecta is a prime site for r-process nucleosynthesis, which will produce a range of radioactive heavy nuclei. The decay of these nuclei releases enough energy to accelerate portions of the wind by ~0.1c. Here, we investigate the effect of r-process heating on the dynamical evolution of disc winds. We extract the wind from a 3D general relativistic magnetohydrodynamic simulation of a disc from a post-merger system. This is used to create inner boundary conditions for 2D hydrodynamic simulations that continue the original 3D simulation. We perform two such simulations: one that includes the r-process heating, and another one that does not. We follow the hydrodynamic simulations until the winds reach homology (60 s). Using time-dependent multifrequency multidimensional Monte Carlo radiation transport simulations, we then calculate the kilonova light curves from the winds with and without dynamical r-process heating. We find that the r-process heating can substantially alter the velocity distribution of the wind, shifting the mass-weighted median velocity from 0.06c to 0.12c. The inclusion of the dynamical r-process heating makes the light curve brighter and bluer at $$\sim 1\, \mathrm{d}$$ post-merger. However, the high-velocity tail of the ejecta distribution and the early ($$\lesssim 1\, \mathrm{d}$$) light curves are largely unaffected.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1855365
• Journal Information: Monthly Notices of the Royal Astronomical Society, Vol. 510, Issue 2; ISSN 0035-8711
• Publisher: Royal Astronomical Society
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
neutron star mergers
radiative transfer