Abstract
We performed 86 GHz VLBI observations of Sgr A*. Here we present the analysis of two datasets: one epoch using the VLBA (all 86GHz capable stations1) together with the LMT (project code: BF114A) on May 22nd, 2015, and one epoch using VLBA, LMT, and GBT on May 23rd, 2015 (project code: BF114B). Both observations were made in left-circular polarization mode only, at a centre frequency of 86.068 GHz and a sampling rate of 2 Gbps (512 MHz on-sky bandwidth). For fringe finding we used the primary calibrators 3C 279 and 3C 454.3 at the start and end of the track respectively. In between, the scans alternated every 5-min between Sgr A* and the secondary fringe finder NRAO 530 ([HB89] 1730-130 with short regular gaps (every ~30min) for pointing and longer GBT-only gaps every ~4h for focusing.
