Every Datapoint Counts: Atmosphere-aided Flare Studies in the Rubin era

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In 1859, the Earth was struck by a solar storm that disrupted telegraph stations and created visible aurorae as far south as Cuba. If the same storm were to happen today, it would cause trillions of dollars in damage to the world’s power grids and communication technology. Just before the event, English astronomer Richard Carrington observed a sudden brightening of the Sun’s surface - the first observation of a solar flare. Flares such as the one Carrington observed are not unique to the Sun, but also occur on other stars, especially those cooler and less massive than the Sun. They vary across a range of energies, temperatures, durations, and brightness. By measuring the properties of flares, we come closer to understanding how they work and how they affect a planet’s ability to sustain life. In particular, measuring the temperature of flares can tell us the extent to which they threaten the atmospheres of planets orbiting other stars. The Legacy Survey of Space and Time (LSST) will observe millions of stellar flares over its 10-year mission. The investigators are developing a technique to use the Earth’s atmosphere to measure the color, and thus the temperature, of the flares. This project will also sponsor a student at Lincoln University to work on “sonification” of Rubin data. This technique is the representation of data through sound, to make the results accessible to Blind and Visually Impaired (BVI) persons. The upcoming Vera C. Rubin Observatory through its Legacy Survey of Space and Time (LSST) provides an opportunity to collect a large ensemble of flare measurements from millions of stars across the sky. Because of the short flare duration and the survey cadence, it is unlikely that flares will be detected with more than one data point. This program aims to develop a methodology to enable LSST studies of stellar flares, with a focus on flare temperature and temperature evolution, which remain poorly constrained compared to the photometric morphology of flares. Leveraging the exquisite image quality and sensitivity expected from the Rubin system, Differential Chromatic Refraction can be used to constrain flare temperature from a single-epoch detection. Modeling the refraction effect as a function of the atmospheric column density, photometric filter, and temperature of the flare, flare temperatures at or above 10,000K can be constrained by a single g-band observation at airmass as low as X=1.2, given the minimum specified requirement on single-visit absolute astrometric accuracy of LSST. Nearly 100,000 g-band images are expected to be collected at higher airmass than X=1.2 in the Rubin LSST 10-year survey. This project will develop a pipeline to process LSST data and characterize a large sample of sparsely observed flare temperatures, which will constrain models of the physical processes behind flare emission as well as the relationship between flare parameters (e.g. temperature, duration, energy) and stellar parameters (e.g. spectral type, rotation, magnetic field).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.