The Simons Observatory: Development of a Pipeline to Detect Rapid Transients in Time-Ordered Data

TL;DR

This paper presents a new pipeline for detecting fast astrophysical transients directly from raw CMB survey data, enhancing sensitivity to millisecond to minute scale events and demonstrating effective performance on simulated data.

Contribution

The authors develop and integrate a novel real-time detection pipeline for fast transients into the Simons Observatory, operating directly on time-ordered data for the first time.

Findings

Detects over 90% of 0.5 s flares at various frequencies.

Reduces detection thresholds for longer flares.

Accurately localizes transient positions within the telescope resolution.

Abstract

We introduce a method for detecting astrophysical transients evolving on timescales of milliseconds to minutes using cosmic microwave background (CMB) survey telescopes. While previous transient searches in CMB data operate in map space, our pipeline directly processes the raw time-ordered data, enabling sensitivity to fast, dynamic signals. We integrate our detection approach into the Simons Observatory time-domain pipeline and assess the performance on simulated observations with injected stellar flare-like light curves. For events flaring with a timescale of 0.5 s, the pipeline detects $\gtrsim90$% of events at flux densities of 800, 1150, 1650, and 4250 mJy when measured in the 93, 145, 225, and 280 GHz bands respectively. For longer $\ge5$ second flares, the 90% detection thresholds are reduced by a factor of four. We are able to determine the position of detected events in each observing band, with a positional uncertainty at the detection threshold comparable to the telescope resolution at that band. These results demonstrate the readiness of this pipeline for incorporation into upcoming Simons Observatory data analyses.