Long-duration (>2 s) γ-ray bursts that are believed to originate from the death of massive stars are expected to be accompanied by supernovae. GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very stringent limits and its physical origin is still debated. Here we report the discovery of near-infrared bump that is significantly above the regular decaying afterglow. This red bump is inconsistent with even the weakest known supernova. However, it can arise from a Li-Paczyński macronova—the radioactive decay of debris following a compact binary merger. If this interpretation is correct, GRB 060614 arose from a compact binary merger rather than from the death of a massive star and it was a site of a significant production of heavy r-process elements. The significant ejected mass favours a black hole–neutron star merger but a double neutron star merger cannot be ruled out.

The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2 ¹/₂ years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.

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 "Equation missing" 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.

We discuss the possibility of using fast radio bursts (FRBs)\char22{}if cosmological\char22{}as a viable cosmic probe. We find that the contribution of the host galaxies to the detected dispersion measures can be inapparent for the FRBs that are not from galaxy centers or star-forming regions. The inhomogeneity of the intergalactic medium (IGM), however, causes significant deviation of the dispersion measure from that predicted in the simplified homogeneous IGM model for an individual event. Fortunately, with sufficient FRBs along different sightlines but within a very narrow redshift interval (e.g., $\mathrm{$\Delta${}}z$\sim${}0.05$), the mean obtained from averaging observed dispersion measures does not suffer such a problem and hence may be used as a cosmic probe. We show that in the optimistic case (e.g., about 20 FRBs in each $\mathrm{$\Delta${}}z$ have been measured; the most distant FRBs were at redshift $$\ge${}3$; the host galaxies and the FRB sources contribute little to the detected dispersion measures) and with all the uncertainties (i.e., the inhomogeneity of the IGM, the contribution and uncertainty of host galaxies, and the evolution and error of ${f}_{\mathrm{IGM}}$) considered, FRBs could help constrain the equation of state of dark energy.