The Flaring TESS Objects of Interest: Flare Rates for all Two Minute Cadence TESS Planet Candidates

TL;DR

This study surveys flare rates of all 2250 TESS Objects of Interest with 2-minute cadence data, identifying flare stars, measuring flare distributions, and assessing their impact on atmospheric characterization of exoplanets.

Contribution

It provides the first comprehensive flare rate survey for all non-retired TESS TOIs with 2-minute data and introduces a flare ranking metric for target prioritization.

Findings

93 TOIs orbit flare stars and have measured flare frequency distributions.

TOIs of <1.5 R_Earth more frequently orbit flare stars.

One quarter of terrestrial M-dwarf planets are orbiting flare stars suitable for transmission spectroscopy.

Abstract

Although more than 5000 TESS Objects of Interest have been cataloged, no comprehensive survey of the flare rates of their host stars exists. We perform the first flare survey of all 2250 non-retired TOIs with 2 min cadence light curves to measure or place upper limits on their flare rates. We find 93 candidates orbit flare stars and measure their flare frequency distributions. Across the sample, TOIs of <1.5R_Earth orbit flare stars more frequently than do TOIs of 1.5<R<2.75R_Earth, 2.75<R<4R_Earth, or R<4R_Earth. We sort all TOI host stars by their flare rate/upper limit, stellar mass, and distance to create a flare ranking metric (FRM) to determine suitability for follow-up. The FRM of each TOI is then checked against the expected signal-to-noise of atmospheric features in transmission spectroscopy to locate the most promising targets. We find 1/4 of terrestrial M-dwarf planets amenable to transmission spectroscopy orbit flare stars. However, none of the M-dwarf hosts to terrestrial planets are currently flaring at sufficient levels for >99.9% atmospheric ozone depletion. We give the first upper limits on the flare rate of the host star to TOI 700 d and explore the flare rates incident on young planets such as DS Tuc Ab.