TITLE: GCN CIRCULAR NUMBER: 21804 SUBJECT: LIGO/Virgo G298048: e-MERLIN upper limits on 5 GHz compact emission from SSS17a DATE: 17/09/04 07:48:43 GMT FROM: Zsolt Paragi at Euro VLBI Javier Moldon and Rob Beswick (JBO-Manchester University) for the EuroVLBI team We monitored the field around the optical counterpart SSS17a (Coulter et al., LVC 21529) with the e-MERLIN radio interferometer between August 23 and 28, 2017. We conducted observations at C band centred at 5 GHz with a bandwidth of 512 MHz for 5 hours between 13:00 and 18:00 UTC in each consecutive day. No significant detection above 5-sigma level is found in the runs with individual rms noise levels between 31 and 39 microJy/beam. The upper limits at 5-sigma level are 180, 160, 160, 190, 150, 150 microJy/beam for days 23 to 28 August, respectively. The average half power beam width of the images is 266 mas x 33 mas with a position angle of 0 degrees. An image produced combining the data from the six runs yields an upper limit of 70 microJy/beam at the 5-sigma level. Additional observations are planned with e-MERLIN to continue the monitoring of the transient source. e-MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of STFC. -- Zsolt Paragi Head of User Support Joint Institute for VLBI ERIC (JIVE) Web: http://www.jive.eu Oude Hoogeveensedijk 4 Phone: +31 (0)521-596-536 7991 PD Dwingeloo Mobile: +31 (0)629-034-718 the Netherlands Fax: +31 (0)521-596-539