The NuSTAR schedule last week included targets for joint observing programs with ESA’s XMM-Newton observatory and the NASA’s Imaging X-ray Polarimetry Explorer (IXPE).  This would not be unusual except that the observations were for proposals selected for General Observer (GO) programs that do not officially begin until next year. These early observations were required to be able to coordinate with the schedule of observations being performed by the JAXA/NASA/ESA mission XRISM. The combination of the low X-ray energy sensitivity of XMM-Newton, the high spectral resolution of XRISM, and the broad high X-ray energy sensitivity of NuSTAR is proving to be a powerful combination, allowing detailed analysis of the emission from material flowing into and out of regions around supermassive black holes at the center of the nearby active galaxies. NuSTAR observations last week of another active galaxy, Ark 564, were timed to be simultaneous with a series of observations by IXPE to discriminate between competing models of the properties of a corona of hot plasma near the accretion disk close to the black hole. The other targets in the NuSTAR schedule last week also included the final observations for the previous NuSTAR GO cycle, held over to this month to coordinate with ground-based optical observatories, as well as calibration observations of the stellar-mass black hole binary system, Cyg X-2, performed to support re-calibration observations of the IXPE detectors.

Author: Karl Forster (NuSTAR Operations Lead, Caltech)