TITLE: GCN CIRCULAR NUMBER: 19428 SUBJECT: GRB 160509A: Further VLA Observations DATE: 16/05/13 15:48:05 GMT FROM: S. Bradley Cenko at NASA/GSFC S. B. Cenko (NASA GSFC), S. Vogel (U. Maryland), D. A. Perley (DARK), and A. Fruchter (STScI) report on behalf of a larger collaboration: We have imaged the location of the radio afterglow (Alexander et al., GCN 19414) of GRB 160509A (Longo et al., GCN 19403; Roberts et al., GCN 19411; Ono et al, GCN 19405) with the Very Large Array beginning at 10:11 UT on 2016 May 11 (2.0 d after the Fermi-GBM trigger time) in both C and X bands. The radio counterpart has brightened significantly since the early observations reported in Alexander et al., GCN 19414. We measure a preliminary flux density of ~ 0.7 mJy in X-band (9.0 GHz) and ~ 0.5 mJy in C-band (6.0 GHz), corresponding to a spectral index beta ~ 0.8 (fnu ~ nu^beta). Further observations are planned.