Performance of the X-Calibur Hard X-Ray Polarimetry Mission during its 2018/19 Long-Duration Balloon Flight

X-Calibur is a balloon-borne telescope that measures the polarization of high-energy X-rays in the 15--50keV energy range. The instrument makes use of the fact that X-rays scatter preferentially perpendicular to the polarization direction. A beryllium scattering element surrounded by pixellated CZT detectors is located at the focal point of the InFOC{\mu}S hard X-ray mirror. The instrument was launched for a long-duration balloon (LDB) flight from McMurdo (Antarctica) on December 29, 2018, and obtained the first constraints of the hard X-ray polarization of an accretion-powered pulsar. Here, we describe the characterization and calibration of the instrument on the ground and its performance during the flight, as well as simulations of particle backgrounds and a comparison to measured rates. The pointing system and polarimeter achieved the excellent projected performance. The energy detection threshold for the anticoincidence system was found to be higher than expected and it exhibited unanticipated dead time. Both issues will be remedied for future flights. Overall, the mission performance was nominal, and results will inform the design of the follow-up mission XL-Calibur, which is scheduled to be launched in summer 2022.Comment: 19 pages, 31 figures, submitted to Astropart. Phy

Formative Process Evaluation for Implementing a Social Marketing Intervention to Increase Walking Among African Americans in the Positive Action for Today’s Health Trial

Objectives. Evaluating programs targeting physical activity may help to reduce disparate rates of obesity among African Americans. We report formative process evaluation methods and implementation dose, fidelity, and reach in the Positive Action for Today’s Health trial. Methods: We applied evaluation methods based on an ecological framework in 2 community-based police-patrolled walking programs targeting access and safety in underserved African American communities. One program also targeted social connectedness and motivation to walk using a social marketing approach. Process data were systematically collected from baseline to 12 months. Results: Adequate implementation dose was achieved, with fidelity achieved but less stable in both programs. Monthly walkers increased to 424 in the walking-plus-social marketing program, indicating expanding program reach, in contrast to no increase in the walking-only program. Increased reach was correlated with peer-led Pride Strides (r = .92; P < .001), a key social marketing component, and program social interaction was the primary reason for which walkers reported participating. Conclusions: Formative process evaluation demonstrated that the walking programs were effectively implemented and that social marketing increased walking and perceived social connectedness in African American communities