The International Astronomical Consortium for High-Energy Calibration (IACHEC) is an independent collaboration of scientists and engineers working to provide standards in the calibration of high energy (X-ray to gamma-ray) missions. Each year, coordinated observations of astrophysical targets are organized through the IACHEC. The data are shared between the missions and analysis organized to measure the cross-calibration of multiple instruments. Last week, simultaneous observations of the quasar 3C 273 were performed by nine missions, including NuSTAR. This is a record coordination of space missions from multiple organizations and countries. Observations were performed by NASA’s Chandra, Gehrels-Swift, NICER, IXPE, and NuSTAR observatories and were joined by ESA’s XMM-Newton, INTEGRAL, and Einstein Probe missions, as well as the JAXA/NASA/ESA XRISM mission. Data analysis is underway by members of the IACHEC calibration working groups and will be presented at the next IACHEC meeting in May in Osaka Bay (Japan).

The results of the selection for NICER cycle-7 were announced last week and include eight proposals selected for the joint observing program with NuSTAR. Of these, seven proposals were for Target of Opportunity (ToO) investigations, triggered when a transient event occurs in the universe, or when certain conditions are met. This is a record for the program, the high proportion of ToO proposals selected for joint observations is consistent with increasing interest in time domain astrophysics. The joint NuSTAR / NICER program is one of the six general observer (GO) programs that offer NuSTAR observing time to the community. Details of the proposal selection for observations in 2025 through joint programs with Chandra, XMM-Newton, IXPE, and NICER are now available and we expect the selection for Gehrels-Swift cycle-21 to be announced soon. This is in time for the community to evaluate the need for proposals for observations in NuSTAR GO cycle-11, the due date for which is January 29th, and which also offers XMM-Newton, Gehrels-Swift, and NICER observing time for investigations requiring coordinated observations.

Authors: Karl Forster (NuSTAR Science Operations Manager), Hannah Earnshaw (NuSTAR Project Scientist)