Presentation #111.02 in the session “Time Domain Astrophysics (Poster)”.
Gamma-ray bursts (GRBs) categorically produce broadband afterglow emission, but in some cases, emission in the optical band is less luminous than expected. The phenomenon of optical darkness has been studied extensively in long GRBs (related to massive stellar explosions), with a number of proposed explanations, including high redshift and host galaxy extinction. Investigations into optical darkness in short GRBs (resulting from compact object binary mergers) have thus far been limited. This work implements an automated data analysis routine for determining the optical darkness of GRBs, which is based on spectral indices calculated from temporally-matched Swift-XRT data and ground-based follow-up observations. The pipeline produces a complete catalog of potential optically dark short GRBs. In the process of this analysis, we develop a versatile codebase that facilitates reproducibility of the processing pipeline for use on future GRBs. Here we present the results of our study and outline some of the possible explanations for optical darkness in short GRBs. Our analysis tools and resulting complete sample of dark short GRBs enable a systematic statistical study of the dark gamma-ray burst population, which—together with an exploration of the specific circumstances of each new GRB we identify as dark—provide new insight into the phenomenon and its origins.