Identifying Flare Locations Through Exoplanet Transit Occultations

TL;DR

This paper proposes a novel method using optical photometry during exoplanet transits to locate stellar flare regions on M dwarfs, which impacts understanding of stellar activity and exoplanet habitability.

Contribution

It introduces a new technique to identify flare latitudes on M dwarfs through transit occultation analysis, enhancing stellar activity mapping capabilities.

Findings

Estimated 3-22 detectable occultations in TESS data

Most occultations occur in eclipsing binary systems

Demonstrated flare occultation detection on CM Draconis

Abstract

M dwarfs are the most common stars in the galaxy, with long lifespans, a high occurrence rate of rocky planets, and close-in habitable zones. However, high stellar activity in the form of frequent flaring and any associated coronal mass ejections may drive atmospheric escape with the bombardment of radiation and high-energy particles, drastically impacting the habitability of these systems. The stellar latitude where flares and coronal mass ejections occur determines the space weather that exoplanets are subject to, with high-energy particle events associated with equatorial flares producing significant atmospheric erosion. However, the flaring latitudes for M dwarfs remain largely unconstrained. To aid in the effort to locate these flaring regions we explore the applicability of flare occultations using optical photometry to identify the latitudes of flares. As a planet transits in front of an ongoing flare the timing and geometry of the transit can be used to constrain the latitude and longitude of the flare. We predict the probability of detecting an occultation for known transiting planets and eclipsing binaries. From this, we estimate 3-22 detectable occultations exist within the TESS primary mission photometry, with the majority occurring in eclipsing binary observations. To demonstrate this technique, we analyze a candidate flare occultation event for the eclipsing binary CM Draconis.