Spectroscopy of the short GRB 130603B: The host galaxy and environment of a compact object merger

The nature of short duration gamma-ray bursts (GRBs) remains a central problem of modern astrophysics. They are thought to be related to the violent merger of compact objects, such as neutron stars or black holes, which would make them promising sources of gravitational waves. The absence of supernovae signatures clearly indicates that SGRB progenitors differ from their long duration cousins, but constraints to-date arise almost entirely from studies of host galaxies to which they cannot always be securely associated. Further progress has been significantly hampered by the faintness and rapid fading of their optical counterparts

(afterglows), which has so far precluded spectroscopy of such events. Afterglow spectroscopy is the key tool to firmly determine the distance at which the burst was produced, crucial to quantify its physics, and study its local environment. In this talk I will present the first spectra of a prototypical short GRB afterglow in which absorption features are detected. From these spectra we determine the unequivocal redshift of the burst to be z=0.3565, measure absorption lines and a substantial line of sight extinction. The detection of a ‘kilonova’ emission associated to GRB130603B confirms that this event is the result of a compact object merger. Our observations give the first detailed view of the environment of such an event and suggest a merger with a short delay time.

03/10/2013 - 14:30
Dr. Antonio de Ugarte Postigo