Automating Citizen Scientist Contributions to REFITT

Increasingly sophisticated all-sky survey telescopes associated with large-scale data collection have motivated development of cyberinfrastructure that can process and prioritize discoveries and coordinate complementary observations that enhance science inference. The Recommender Engine for Intelligent Transient Tracking (REFITT) fulfills this need by ingesting survey data streams and broker input to make forecasts on the time evolution of transients in our sky (Sravan et al. 2020). These predictions are prioritized and sent to available and optimal observing agents for follow up observations to optimally augment light curves in order to expand our knowledge of the properties and physics of transients. In order for REFITT to ingest the data and forecast transient evolution, all measurements must be transformed into a standard photometric system. We developed a pipeline that ingests combined images, confirms object coordinates, calibrates the Zero Point using standard calibration stars, applies appropriate aperture radii, performs aperture photometry, and applies needed transformations. We focused on developing a transformation of unfiltered measurements to the g and r filters of the Zwicky Transient Facility (ZTF). This can enable amateur astronomers to contribute observations that are often unfiltered to maximize the light gathering power of small aperture telescopes. We investigated two methods to transform measurements made from unfiltered images to ZTF passbands to place them in context with light curves of transients discovered by the public survey of ZTF. Direct calibration uses reference field stars in the ZTF DR3 catalog to find the Zero Point. The second method uses the color information of the transient and a property of the telescope instrument, the color term (CT), which is measured using field stars. For an object with a sparse light curve, the direct calibration method is preferable, however, we found that the second method was the more precise way to transform unfiltered measurements to filtered measurements, thus accurately tracking transient evolution. Future work includes building a large sample of observations to best measure CT and including additional color terms for high confidence transformations. Our work removes obstacles for Citizen Scientist to contribute to REFITT and to efficiently participate in the global effort to monitor the dynamic universe.