If the weather holds up, we will launch tomorrow (Tuesday Sept. 13) morning. As we prepare for the flight, we are using data taken with the Burst Alert Telescope (BAT) on board the Swift satellite mission to see which sources shine brightly in the 15-150 keV energy range. The Swift team publishes every day all sources the BAT detects. We plan that X-Calibur will observe the brightest sources. Right now the brightest northern hemisphere sources include the accreting neutron star Sco X-1, the rotation powered Crab Nebula and Pulsar (harboring a spinning neutron star), and the stellar mass black hole Cyg X-1.
We will complement the X-Calibur observations by simultaneously acquired pointed observations with the Swift X-Ray Telescope (XRT). The XRT will observe the sources in the 0.2-10 keV band, and X-Calibur in the 25-60 keV band. The data can be combined to find out in which emission state the source is during the observations. The objective of the X-Calibur observations is to use the added polarimetric information to constrain the models that have been developed to explain the X-ray emission.