RAPID: Roman Alerts Promptly from Image Differencing

Mansi Kasliwal / California Institute of Technology, PI

The 2020 Decadal Survey identified time-domain and multi-messenger science as a high priority this decade. We propose a Project Infrastructure Team to enable a wide suite of dynamic sky science for the Nancy Grace Roman Space Telescope. Our goal is to provide four services:

1. Rapid image-differencing of every new Roman image from a reference image
2. Prompt public alert stream of all transient and variable candidates in the Roman difference images
3. Source match-files recording candidate photometry for every Roman source observed more than once in the same filter
4. Forced-photometry service to investigate precise photometric history at any location by drilling into all available Roman data.

The proposing team has extensive prior experience in building similar services for dedicated time-domain surveys. By promptly delivering a reliable alert stream, the transient and variable communities will be able to undertake timely panchromatic follow-up of the most interesting Roman discoveries. It is essential to provide full history and context to alerts in order to correctly identify high-value transients, and properly allocate follow-up resources, especially spectrographs.

Much of the proposed infrastructure will leverage previous work on other projects. We plan to broadcast the public alert stream in the same format as pioneered by the Zwicky Transient Facility. This format has recently been adopted

Development work will be required to adapt and tune our methods to Roman. We will use simulated Roman images to develop and test our pipeline before launch. We will solve image differencing to tackle the undersampled PSF and lack of a fixed reference grid in the Roman data. We will also develop machine learning for robust candidate identification. We have discussed this plan with colleagues at STSCI to understand how the initial input to this pipeline will come from MAST and how the final output of this pipeline will be returned to MAST for alert archiving.