Improving the detectability of gravitational wave counterparts of short hard gamma ray bursts
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With multiple observatories and missions being planned for detecting orphaned afterglows associated with gamma-ray bursts (GRBs) we emphasize the importance of developing data analysis strategies for searching their possible counterpart signals in the data of gravitational wave detectors in the advanced detector era. This is especially attractive since short hard gamma-ray bursts (SGRBs) may have compact binary coalescences involving neutron stars (CBCNS) as their progenitors, which emit gravitational waves. Joint electromagnetic and gravitational wave observations of these objects will enrich our understanding of their beaming, energetics, galactic environment, and shed light on a host of other outstanding questions related to them. We recognize some of the astrophysical factors that determine what fraction of these sources can generate orphaned afterglows. We developed a search pipeline by modifying the existing blind hierarchical coherent search pipeline, targeting their sky-position and time of occurrence known from EM observations to enable it to search for counterparts of SGRB and SGRB afterglows in gravitational wave detector data. The modifications allows it to analyze extended periods of time in the gravitational wave data in the past of the afterglow detection epoch, while targeting its known sky-position, to search for gravitational waves from the common progenitor. We assess the improvement in gravitational wave detectability to be had from utilizing the sky-position information. We also propose a method for mitigating the effects on the detection efficiency of targeted searches of gravitational wave signals from the putative CBCNS sources of afterglows and short gamma-ray bursts arising from the presence of errors in detector calibration or CBCNS waveform models used in the search.