TITLE: GCN CIRCULAR NUMBER: 23506 SUBJECT: Fermi-GBM Observations During Four New GW-Detected BBH Mergers DATE: 18/12/04 18:56:35 GMT FROM: Eric Burns at GSFC Four new binary black hole mergers detections by LIGO/Virgo have been reported in GWTC-1, the first catalog of gravitational-wave transients [1]. We searched for coincident Fermi-GBM on-board triggers[2], sub-threshold short gamma-ray burst candidates[3], and for transient using the targeted search of Fermi-GBM data[4]. In no cases did we find significant gamma-ray emission in the Fermi-GBM data. We report the GW localization probability observed by Fermi-GBM (observing fraction) for each GW at event time: GW Observing Fraction GW170729 88% GW170809 78% GW170818 100% GW170823 0% (Fermi was transiting the SAA) The results of the observations around prior gravitational wave signals have been previously published or are reported in GCN circulars. We have searched for significant gamma-ray emission in Fermi-GBM around the marginal triggers reported in GWTC-1 and found nothing of immediate interest. The results here are preliminary. The final results and the population-level analysis are part of on-going work between Fermi-GBM and LIGO/Virgo. Upper limits may be presented in this work. The implications of these non-detections on the candidate counterpart around GW150914 are the subject of on-going work. [1] https://arxiv.org/abs/1811.12907 [2] https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html [3] https://gcn.gsfc.nasa.gov/fermi_gbm_subthresh_archive.html [4] http://iopscience.iop.org/article/10.1088/0067-0049/217/1/8/meta [GCN OPS NOTE(04dec18): This circular (23506) is superceeded by Circular 23508 when the author resubmitted with a copy that had the authors included.]