The effect of jet–ejecta interaction on the viewing angle dependence of kilonova light curves

Journal Article · Sat Jan 09 00:00:00 EST 2021 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stab042· OSTI ID:1763809

Klion, Hannah ^[1]; Duffell, Paul C. ^[2]; Kasen, Daniel ^[3]; Quataert, Eliot ^[4]

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1. Physics and Astronomy Departments and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720, USA
2. Center for Astrophysics, Harvard University, Cambridge, MA 02138, USA, Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
3. Physics and Astronomy Departments and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720, USA, Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
4. Physics and Astronomy Departments and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720, USA, Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA

ABSTRACT

The merger of two neutron stars produces an outflow of radioactive heavy nuclei. Within a second of merger, the central remnant is expected to also launch a relativistic jet, which shock-heats and disrupts a portion of the radioactive ejecta. Within a few hours, emission from the radioactive material gives rise to an ultraviolet, optical, and infrared transient (a kilonova). We use the endstates of a suite of 2D relativistic hydrodynamic simulations of jet–ejecta interaction as initial conditions for multidimensional Monte Carlo radiation transport simulations of the resulting viewing angle-dependent light curves and spectra starting at $$1.5\, \mathrm{h}$$ after merger. We find that on this time-scale, jet shock heating does not affect the kilonova emission for the jet parameters we survey. However, the jet disruption to the density structure of the ejecta does change the light curves. The jet carves a channel into the otherwise spheroidal ejecta, revealing the hot, inner regions. As seen from near (≲30°) the jet axis, the kilonova is brighter by a factor of a few and bluer. The strength of this effect depends on the jet parameters, since the light curves of more heavily disrupted ejecta are more strongly affected. The light curves and spectra are also more heavily modified in the ultraviolet than in the optical.

• Sponsoring Organization: USDOE
• Grant/Contract Number: FG02-97ER25308
• OSTI ID: 1763809
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 1 Vol. 502; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English