DECam Multi-Messenger Astrophysics Pipeline. I. from Raw Data to Single-Exposure Candidates

TL;DR

This paper presents a pipeline for rapid detection of astrophysical transients, including gravitational wave counterparts, from raw DECam data using image subtraction and source selection techniques.

Contribution

The authors develop a pipeline that processes raw DECam data to identify single-exposure transients, adaptable for other instruments and future surveys like LSST.

Findings

Pipeline produces clean, high-quality light curves.

Effective detection of bright transients with S/N ≥ 15.

Validated with archival data covering various transient types.

Abstract

We introduce a pipeline that performs rapid image subtraction and source selection to detect transients, with a focus on identifying gravitational wave optical counterparts using the Dark Energy Camera (DECam). In this work, we present the pipeline steps from processing raw data to identification of astrophysical transients on individual exposures. We process DECam data and build difference images using the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) Science Pipelines software, and we use flags and principal component analysis to select transients on a per-exposure basis, without associating the results from different exposures. Those candidates will be sent to brokers for further classification and alert distribution. We validate our pipeline using archival exposures that cover various types of objects, and the tested targets include a kilonova (GW170817), supernovae, stellar flares, variable stars (in a resolved galaxy or the Milky Way Bulge), and serendipitous objects. Overall, the data processing produces clean light curves that are comparable with published results, demonstrating the photometric quality of our pipeline. Real transients can be well selected by our pipeline when sufficiently bright (S/N $\gtrsim15$). This pipeline is intended to serve as a tool for the broader research community. Although this pipeline is designed for DECam, our method can be easily applied to other instruments and future LSST observations.