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Electromagnetic counterparts of compact object mergers powered by the radioactive decay of r-process nuclei

Metzger, B. D. ; Martínez-Pinedo, G. ; Darbha, S. ; Quataert, E. ; Arcones, A. ; Kasen, D. ; Thomas, R. ; Nugent, P. ; Panov, I. V. ; Zinner, N. T.

In: Monthly Notices of the Royal Astronomical Society, 2010, vol. 406, no. 4, p. 2650-2662

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    Title
    • Electromagnetic counterparts of compact object mergers powered by the radioactive decay of r-process nuclei
    Author
    • Metzger, B. D.. Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
    • Martínez-Pinedo, G.. GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, D-64291 Darmstadt, Germany
    • Darbha, S.. Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, 601 Campbell Hall, Berkeley, CA 94720, USA
    • Quataert, E.. Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, 601 Campbell Hall, Berkeley, CA 94720, USA
    • Arcones, A.. GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, D-64291 Darmstadt, Germany
    • Kasen, D.. University of California, Santa Cruz, CA 95064, USA
    • Thomas, R.. Computational Cosmology Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS50B-4206, Berkeley, CA 94720, USA
    • Nugent, P.. Computational Cosmology Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS50B-4206, Berkeley, CA 94720, USA
    • Panov, I. V.. Department of Physics, University of Basel, Klingelbergstr. 82, CH-4056 Basel, Switzerland
    • Zinner, N. T.. Department of Physics, Harvard University, Cambridge, MA 02138, USA
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:304105
    Summary
    The most promising astrophysical sources of kHz gravitational waves (GWs) are the inspiral and merger of binary neutron star(NS)/black hole systems. Maximizing the scientific return of a GW detection will require identifying a coincident electromagnetic (EM) counterpart. One of the most likely sources of isotropic EM emission from compact object mergers is a supernova-like transient powered by the radioactive decay of heavy elements synthesized in ejecta from the merger. We present the first calculations of the optical transients from compact object mergers that self-consistently determine the radioactive heating by means of a nuclear reaction network; using this heating rate, we model the light curve with a one-dimensional Monte Carlo radiation transfer calculation. For an ejecta mass ∼10−2 M⊙ (10−3 M⊙) the resulting light-curve peaks on a time-scale ∼1 d at a V-band luminosity νLν∼ 3 × 1041 (1041) erg s−1[MV=−15(−14)]; this corresponds to an effective ‘f' parameter ∼3 × 10−6 in the Li-Paczynski toy model. We argue that these results are relatively insensitive to uncertainties in the relevant nuclear physics and to the precise early-time dynamics and ejecta composition. Since NS merger transients peak at a luminosity that is a factor of ∼103 higher than a typical nova, we propose naming these events ‘kilo-novae'. Because of the rapid evolution and low luminosity of NS merger transients, EM counterpart searches triggered by GW detections will require close collaboration between the GW and astronomical communities. NS merger transients may also be detectable following a short-duration gamma-ray burst or ‘blindly' with present or upcoming optical transient surveys. Because the emission produced by NS merger ejecta is powered by the formation of rare r-process elements, current optical transient surveys can directly constrain the unknown origin of the heaviest elements in the Universe