Every Datapoint Counts: Stellar Flares as a Case Study of Atmosphere Aided Studies of Transients in the LSST Era

TL;DR

This paper proposes a novel method to study stellar flares using LSST data by leveraging Differential Chromatic Refraction to estimate flare temperatures from single-epoch observations, enabling large-scale statistical analysis of flare properties.

Contribution

It introduces a methodology utilizing DCR effects to constrain flare temperatures from single observations, addressing a key challenge in LSST flare detection and analysis.

Findings

Flare temperatures ≥ 4000K can be constrained from single g-band observations at high airmass.

Many LSST observations will occur at high airmass, enabling temperature estimation.

Recommendations are provided for survey design to optimize flare studies with LSST.

Abstract

Due to their short timescale, stellar flares are a challenging target for the most modern synoptic sky surveys. The upcoming Vera C. Rubin Legacy Survey of Space and Time (LSST), a project designed to collect more data than any precursor survey, is unlikely to detect flares with more than one data point in its main survey. We developed a methodology to enable LSST studies of stellar flares, with a focus on flare temperature and temperature evolution, which remain poorly constrained compared to flare morphology. By leveraging the sensitivity expected from the Rubin system, Differential Chromatic Refraction can be used to constrain flare temperature from a single-epoch detection, which will enable statistical studies of flare temperatures and constrain models of the physical processes behind flare emission using the unprecedentedly high volume of data produced by Rubin over the 10-year LSST. We model the refraction effect as a function of the atmospheric column density, photometric filter, and temperature of the flare, and show that flare temperatures at or above ~4,000K can be constrained by a single g-band observation at airmass X > 1.2, given the minimum specified requirement on single-visit relative astrometric accuracy of LSST, and that a surprisingly large number of LSST observations is in fact likely be conducted at X > 1.2, in spite of image quality requirements pushing the survey to preferentially low X. Having failed to measure flare DCR in LSST precursor surveys, we make recommendations on survey design and data products that enable these studies in LSST and other future surveys.