Enhancing the Chandra archive with ZTF alert streams through annotation

The new window on the transient and variable optical sky, opened by current and upcoming synoptic telescopes, will also shine a new light in the X-ray band. Given that many transient and variable events are expected to emit in both the visible and X-ray spectrum, cross-matching and multi-band analysis are particularly salient tools for classifying and characterizing these phenomena. The Chandra Data Archive (CDA) and Chandra Source Catalog (CSC) offer an astounding wealth of X-ray observations, taken over the course of more than 20 years, that can be used to constrain transients and variable sources detected by facilities operating in the visible light. However, manual comparison across separate data archives is a generally daunting and labor-intensive task for a single researcher. We present a programmatic interface that cross-matches the position of transient and variable events, as observed and classified by the Zwicky Transient Facility (ZTF), with archived data from Chandra. The software will provide an accessible, automated means to identify CDA observations and CSC master sources spatially coincident with ZTF observations. This annotation of the Chandra archive with ZTF-based events demonstrates a powerful approach to help archives in both catering to the new scientific needs of communities they serve and maximizing their scientific legacies.