TITLE: GCN CIRCULAR NUMBER: 20981 SUBJECT: LIGO/Virgo G275404: European VLBI Network (EVN) follow-up of the near-IR transient in the AGL J1914+1043 field DATE: 17/04/05 14:50:35 GMT FROM: Zsolt Paragi at Euro VLBI Zsolt Paragi (JIVE) Tao An (Shanghai Astronomical Observatory) Philippe Bacon (APC Université Paris Diderot) Rob Beswick (JBO-Manchester University) Eric Chassande-Mottin (APC Université Paris Diderot) Sándor Frey (Konkoly Observatory) Marcello Giroletti (IRA-INAF) Peter Jonker (SRON) Mark Kettenis (JIVE) Benito Marcote (JIVE) Arpad Szomoru (JIVE) Huib van Langevelde (JIVE) Jun Yang (Onsala Space Observatory) for the Euro VLBI team We observed the near-IR transient (Yoshida et al., GCN 20784) within the error circle of AGL J1914+1043 (Tavani et al., GCN 20754) with the real-time very long baseline interferometry (e-VLBI) technique using the EVN at 4.9 GHz between 2:06—11:48 UT on 24 March 2017. There is no compact radio emission detected on milliarcsecond scales within +-4 arcseconds of the near-IR transient coordinates of RA=19:10:31.46, DEC=+07:53:52.0, with a 6 sigma upper limit of 105 microJy/beam. More details on the Euro VLBI team observations: Participating EVN telescopes were Effelsberg, Irbene, Jodrell Bank MkII, Medicina, Onsala, Noto, Torun, Westerbork (single dish), Yebes, Arecibo, Hartebeesthoek and Tianma. The observing frequency of 4.9 GHz was preferred over 1.6 GHz because of strong scatter-broadening in this region. The phase-referencing calibrator was J1922+0841, 3 degrees away from the target; it has resolved structure on mas scales, but strong fringes were detected. The cycle time was 1:30-3:30 minutes. Total on-source integration time on the target was 4.1 hours. A number of other calibrators/calibrator candidates were observed as well, most notably J1909+0756 (11 arcminutes from the target), that was detected as a ~30 mJy but quite resolved source (~10 mas East-West; not useful as calibrator beyond 10 Mlambda at this frequency). None of the sources reported by Medicina single dish observations at 5 GHz (Pilia et al., GCN 20869) were detected (we had 3 times 1-minute scans on each). The data were correlated real-time with the EVN Software Correlator at JIVE (SFXC) and processed according to standard procedures, using measured system temperature for most telescopes (for Arecibo, Noto, Jodrell Bank we used nominal SEFDs). The EVN is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project code: RP027.