An r−process macronova/kilonova in GRB 060614: evidence for the merger of a neutron star-black hole binary
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China
Published online: 12 February 2016
After the jet break at t ~ 1.4 days, the optical afterglow emission of the long-short burst GRB 060614 can be divided into two components. One is the power-law decaying forward shock afterglow emission. The other is an excess of flux in several multi-band photometric observations, which emerges at ~4 days after the burst, significantly earlier than that observed for a supernova associated with a long-duration GRB. At t > 13.6 days, the F814W-band flux drops faster than t−3.2. Moreover, the spectrum of the excess component is very soft and the luminosity is extremely low. These observed signals are incompatible with those from weak supernovae, but the ejection of ~ 0.1 M⊙ of r−process material from a black hole-neutron star merger, as recently found in some numerical simulations, can produce it. If this interpretation is correct, it represents the ﬁrst time that a multi-epoch/band lightcurve of a Li-Paczynski macronova (also known as kilonova) has been obtained and black hole-neutron star mergers are sites of signiﬁcant production of r−process elements.
© Owned by the authors, published by EDP Sciences, 2016
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