Analysis of Recent Short GRB Afterglow Light Curves

Since the historic Aug. 17, 2017 simultaneous detection of gravitational and electromagnetic waves produced by the merger of two neutron stars, the GW-GRB 170817 event, interest in short gamma-ray bursts (SGRBs) has increased exponentially. SGRBs (bursts with durations less than 2.0 seconds) represent only about 10 % of all bursts, and unlike long GRBs, there was until this recent event no complete consensus on the (merger) physical mechanism responsible for SGRBs. This combined fact had kept interest toward short bursts relatively low. But in the few years before the GW-GRB connection, which fully cemented the merger model as the physical process behind SGRBs, the detection of kilonovae/macronovae associated with three SGRBs had already started to raise the interest in this class of bursts.Fong et al. (2015) collected and analyzed afterglow observations of SGRBs from 2005 to 2014, covering their broadband emission from X-rays to radio. Using the widely adopted theoretical prescription of Panaitescu & Kumar (2000) for calculating afterglow fluxes, Fong et al. (2015) extracted individual and statistical values for the bursts' and afterglows' physical parameters: kinetic energy, medium density, electron and magnetic energy fractions, and jet opening angles. We have extended that work to the last 3 years (Jan. 2015 to Dec. 2017), using Swift events (29 short bursts recorded during that period) and Fermi events (116 events). We have searched the literature (GCN reports and published papers) to collect afterglow observations, whether positive or negative (upper limits), limiting ourselves to optical and near-infrared data, the bands where kilonova detections can be successful.Our aim is to fit or constrain the afterglow light curves with physical parameters, to the extent possible, and to try to identify cases that most resemble those that have had a kilonova detection.We present the most interesting cases that we have uncovered, along with the physical results from the sample.