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  • New evidence for formation of Gold and other heavy rare elements in compact binary mergers
    Author: Update time: 2016-09-26

        A new evidence towards the origin of Gold and other heavy rare elements (like uranium, platinum silver and so on) was put forwards on Sept. 23 2016 in Nature Communications (http://www.nature.com/articles/ncomms12898) by researchers from  Purple Mountain Observatory, Hebrew University, National Astronomical Observatory of Japan and INAF/Brera Astronomical Observatory. These researchers have re-analyzed the HST and VLT data of GRB 050709, the first short event with an identified optical counterpart. They found that instead of being dominated by an afterglow (emission that follow most GRBs and arise due to the inteaction of the GRB jet with the surrounding medium), this signal was mostly dominated, by a Macronova, emission arrising from radioactive decay of heavy rare elements that have been synthsized by matter ejected during a merger between a neurton star and a black hole. Such mergers take place a few times a year and the Universe and they are identified by their accompanying short GRBs. This is the third macronova that has been identified (two earlier ones were associated with the short GRB130309B and hybrid GRB 060614). In fact in searching the arcival data of other short GRBs the research team finds that the results are consistent with macronova apearing in all short/hybrid GRBs and the macronovae were not found because they are too faint at the time the observations were taken. The results imply that most if not all compact bianry mergers generate macronovae and produce Gold and other rare elements. Mergers are also the candidate sources for detecton of gravational waves by advance LIGO and are prime candidates of being the sources of short/hybrid GRBs are also the sources of Gold. This confirms an almost 40 year old prediciton, published in the late eighties in Nature by Piran and his collaborators. The results have two exciting implications. First the total amount of Gold and other rare isotopes observed in this event, when combined with earlier observations suggest that compcat binary mergers are the main source of these elements in our Universe. Second we should expect the detection of gravitational waves from a neutron star merger as well as a macronova from the same event. This could finaly nail down the impressive link between Compact binary mergers, formation of Gold and other rare elements, short Gamma Ray Burst and gravitaional waves as been suggested almost forty years ago.

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