Contributions are accepted from participants that presented invited plenary session reviews, contributed plenary session talks, and contributed posters. In addition, individual and collective contributions from (parallel) splinter sessions and contributions from the CS19 hack day are welcome. Submission of presentation slides from speakers and full posters are encouraged. PDF versions of these documents are the preferred format for Zenodo contributions to permit the documents to be previewed in a web browser. For maximum impact, a written contribution may be provided with presentation slides and/or a poster to provide greater context. Those wishing to submit a written conference proceeding are encouraged to format the document using the CS19 LaTeX template (available on www.coolstars19.com/contributions.html). There are no page limits to written contributions. Contributions will be checked for the proper metadata. Instructions about how to prepare your contribution are available on www.coolstars19.com/contributions.html