The optical afterglow of the short γ-ray burst GRB 050709

• Published in: Nature Vol. 437; no. 7060; pp. 859 - 861
• Main Authors: Hjorth, Jens, Watson, Darach, Fynbo, Johan P. U, Price, Paul A, Jensen, Brian L, Jørgensen, Uffe G, Kubas, Daniel, Gorosabel, Javier, Jakobsson, Páll, Sollerman, Jesper, Pedersen, Kristian, Kouveliotou, Chryssa
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 06.10.2005; Nature Publishing Group
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Gamma-ray sources ; gamma-ray bursts; Stellar systems. Galactic and extragalactic objects and systems. The universe; Unidentified sources and radiation outside the solar system; Energetics; Blue galaxies; Afterglow; Light emission; Supernovae; Dwarf galaxies; Cosmic gamma bursts; Gamma ray burst; Localization; Synchrotron radiation
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature04174

It has long been known that there are two classes of γ-ray bursts (GRBs), mainly distinguished by their durations. The breakthrough in our understanding of long-duration GRBs (those lasting more than ∼2 s), which ultimately linked them with energetic type Ic supernovae, came from the discovery of their long-lived X-ray and optical 'afterglows', when precise and rapid localizations of the sources could finally be obtained. X-ray localizations have recently become available for short (duration <2 s) GRBs, which have evaded optical detection for more than 30 years. Here we report the first discovery of transient optical emission (R-band magnitude ∼23) associated with a short burst: GRB 050709. The optical afterglow was localized with subarcsecond accuracy, and lies in the outskirts of a blue dwarf galaxy. The optical and X-ray afterglow properties 34 h after the GRB are reminiscent of the afterglows of long GRBs, which are attributable to synchrotron emission from ultrarelativistic ejecta. We did not, however, detect a supernova, as found in most nearby long GRB afterglows, which suggests a different origin for the short GRBs.