Energy injection in gamma-ray burst afterglows
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Blvd, Pasadena CA 91125 (United States)
- Racah Institute of Physics, Edmund J. Safra Campus, Hebrew University of Jerusalem, Jerusalem 91904 (Israel)
- University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721 (United States)
We present multi-wavelength observations and modeling of gamma-ray bursts (GRBs) that exhibit a simultaneous re-brightening in their X-ray and optical light curves, and are also detected at radio wavelengths. We show that the re-brightening episodes can be modeled by injection of energy into the blastwave and that in all cases the energy injection rate falls within the theoretical bounds expected for a distribution of energy with ejecta Lorentz factor. Our measured values of the circumburst density, jet opening angle, and beaming-corrected kinetic energy are consistent with the distribution of these parameters for long-duration GRBs at both z∼1 and z≳6, suggesting that the jet launching mechanism and environment of these events are similar to that of GRBs that do not have bumps in their light curves. However, events exhibiting re-brightening episodes have lower radiative efficiencies than average, suggesting that a majority of the kinetic energy of the outflow is carried by slow-moving ejecta, which is further supported by steep measured distributions of the ejecta energy as a function of Lorentz factor. We do not find evidence for reverse shocks over the energy injection period, implying that the onset of energy injection is a gentle process. We further show that GRBs exhibiting simultaneous X-ray and optical re-brightenings are likely the tail of a distribution of events with varying rates of energy injection, forming the most extreme events in their class. Future X-ray observations of GRB afterglows with Swift and its successors will thus likely discover several more such events, while radio follow-up and multi-wavelength modeling of similar events will unveil the role of energy injection in GRB afterglows.
- OSTI ID:
- 22882424
- Journal Information:
- Astrophysical Journal, Vol. 814, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
Similar Records
AFTERGLOW OBSERVATIONS OF FERMI LARGE AREA TELESCOPE GAMMA-RAY BURSTS AND THE EMERGING CLASS OF HYPER-ENERGETIC EVENTS
THE AFTERGLOW AND ULIRG HOST GALAXY OF THE DARK SHORT GRB 120804A