TITLE: GCN CIRCULAR NUMBER: 25946 SUBJECT: FACT follow-up of IceCube-191001A DATE: 19/10/04 20:17:42 GMT FROM: Daniela Dorner at U of Wuerzburg A. Biland (ETH Zurich) reports on behalf of the FACT Collaboration: On Tue 01 Oct 19 20:09:48 UTC, the IceCube collaboration reported the detection of a high-energy neutrino (run number 133119, event number 22683750). FACT observed the position of the neutrino for a total of 5.13 hours on Oct 1st and Oct 2nd. The automatic quick-look analysis does not show any signal from the observed position. Preliminary results can be found at https://fact-project.org/monitoring/index.php?y=2019&m=10&d=02&source=3748&timebin=12&plot=week https://fact-project.org/monitoring/index.php?y=2019&m=10&d=02&source=3748&timebin=3&plot=night https://fact-project.org/monitoring/index.php?y=2019&m=10&d=01&source=3748&timebin=3&plot=night From the results of the quick-look analysis, an upper limit of 24% of the flux of the Crab Nebula at TeV energies was determined with a confidence level of 99%. Contact person: Daniela Dorner (dorner@astro.uni-wuerzburg.de) The First G-APD Cherenkov Telescope (FACT) is an imaging air Cherenkov telescope monitoring blazars at TeV energies. It is located in the Observatorio del Roque de los Muchachos on the Canary Island La Palma. [GCN OPS_NOTE(05oct19): "Title:" was removed from the SUBJECT:-line.]