title: The Macronova in GRB 050709 and the GRB-macronova connection.
abstract: GRB 050709 was the first short Gamma-ray Burst (sGRB) with an identified optical counterpart. Here we report a reanalysis of the publicly available data of this event and the discovery of a Li-Paczynski macronova/kilonova that dominates the optical/infrared signal at t>2.5 days. Such a signal would arise from 0.05 r-process material launched by a compact binary merger. The implied mass ejection supports the suggestion that compact binary mergers are significant and possibly main sites of heavy r-process nucleosynthesis. Furthermore, we have reanalysed all afterglow data from nearby short and hybrid GRBs (shGRBs). A statistical study of shGRB/macronova connection reveals that macronova may have taken place in all these GRBs, although the fraction as low as 0.18 cannot be ruled out. The identification of two of the three macronova candidates in the I-band implies a more promising detection prospect for ground-based surveys.
authors.affiliation: Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Zhi-Ping
authors.initials: ZP
authors.lastname: Jin
authors.affiliation: Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel.
authors.forename: Kenta
authors.initials: K
authors.lastname: Hotokezaka
authors.affiliation: Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China.|University of Chinese Academy of Sciences, Yuquan Road 19, Beijing 100049, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan.
authors.forename: Masaomi
authors.identifier: http://orcid.org/0000-0001-8253-6850
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: INAF/Brera Astronomical Observatory, via Bianchi 46, I-23807 Merate (LC), Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: D'Avanzo
authors.affiliation: Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China.|Collaborative Innovation Center of Modern Astronomy and Space Exploration, Nanjing University, Nanjing 210046, China.
authors.forename: Yi-Zhong
authors.initials: YZ
authors.lastname: Fan
authors.affiliation: INAF/Brera Astronomical Observatory, via Bianchi 46, I-23807 Merate (LC), Italy.
authors.forename: Stefano
authors.identifier: http://orcid.org/0000-0001-9078-5507
authors.initials: S
authors.lastname: Covino
authors.affiliation: Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Da-Ming
authors.initials: DM
authors.lastname: Wei
authors.affiliation: Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel.
authors.forename: Tsvi
authors.initials: T
authors.lastname: Piran