TITLE: GCN CIRCULAR NUMBER: 30937 SUBJECT: IceCube-210922A: Hard X-ray flux limit for JCMT/SCUBA2 source from NuSTAR observations DATE: 21/10/13 17:43:00 GMT FROM: Felicia Krauss at Penn State U <Felicia.Krauss@psu.edu> Felicia Krauss, Timothée Gregoire, Derek Fox, Doug Cowen, Hugo Ayala (PSU) and Alexis Coleiro (APC) report for AMON (https://amon.psu.edu/): The Nuclear Spectroscopic Telescope Array (NuSTAR) has observed the JCMT/SCUBA2 source NVSS J040205-042434, proposed as a possible counterpart to the IceCube-210922A high-energy neutrino (GCN Circ. 30862, 30882). NuSTAR observed the position October 10 (13:55:13 UTC) - October 11 (17:20:00 UTC) for a total of 49.2 ksec. No X-ray source is visible in the field of view. The 3 sigma upper limit for the 3-70 keV flux is 1.6x10^-11 ergs/cm^2/s assuming a photon index of 2.