TITLE: GCN CIRCULAR NUMBER: 21588 SUBJECT: LIGO/Virgo G298048: VLBA observations of the possible counterpart SSS17a in NGC 4993 DATE: 17/08/19 09:36:26 GMT FROM: Igor Andreoni at Swinburne U of Tech A. Deller (Swinburne/OzGrav), M. Bailes (Swinburne/OzGrav), I. Andreoni (Swinburne/OzGrav/AAO), K. Bannister (CSIRO), J. Cooke (Swinburne/OzGrav), D. Dobie (University of Sydney), D. Kaplan (UWM) C. Lynch (University of Sydney), T. Murphy (University of Sydney), on behalf of a joint effort between OzGrav and the VAST collaboration. We are observing the optical transient SSS17a (Coulter et al. - GCN 21529, Allam et al. - GCN 21530, Yang et al.- GCN 21531, Melandri et al. - GCN 21532) and its host galaxy NGC 4993 with the Very Long Baseline Array. We are observing at a central frequency of 8.7 GHz with a bandwidth of 256 MHz. The first observation took place from 2017-08-17 19:58UT to 2017-08-18 01:34UT. Analysis of the data will take place after correlation, in 7-10 days. Two subsequent epochs are planned in the coming three days. We thank the Long Baseline Observatory staff for facilitating these observations.