A Spectacular Radio Flare from XRF 050416a at 40 Days and Implications for the Nature of X-Ray Flashes

摘要: We present detailed optical, near-infrared, and radio observations of the X-ray flash XRF 050416a obtained with Palomar Siding Springs Observatories, as well HST VLA, placing this event among best-studied flashes to date. In addition, we an optical spectrum from Keck LRIS which measure redshift burst, z = 0.6528. At isotropic-equivalent prompt energy release was about 1051 ergs, using a standard afterglow synchrotron model, find that blast wave kinetic is factor 10 larger, EK,iso ≈ 1052 ergs. The lack observed jet break t ~ 20 days indicates opening angle θj 7° total beaming-corrected relativistic 1050 further show burst produced strong flare at 40 accompanied by flattening in band, attribute abrupt circumburst density jump or episode injection (from either refreshed shock off-axis ejecta). Late-time evidence for associated supernova peak luminosity roughly comparable SN 1998bw. Next, host galaxy actively forming stars rate least 2 M☉ yr-1 LB 0.5L* metallicity Z 0.2-0.8 Z☉. Finally, discuss nature context short-hard GRBs under framework dirty fireball models flashes.