The solar-like latitudinal distribution of flaring activities revealed by TESS, APOGEE and GALAH

TL;DR

This study reveals that stellar flares predominantly occur at low latitudes and that the average latitude of active regions increases with faster stellar rotation, using data from TESS, APOGEE, and GALAH.

Contribution

It introduces a novel method to infer the latitudinal distribution of active regions on stars using flare detection and inclination data, revealing a solar-like latitudinal distribution of flaring activity.

Findings

Flares are mainly detected on stars with high inclination, indicating low-latitude activity.

The mean latitude of active regions increases with stellar rotation speed.

Flares are associated with small-scale magnetic fields at low latitudes.

Abstract

Flare flux reflect contribution from active regions rather than the whole hemisphere of a star. Unlike the amplitude of light-curves caused by starspots, the flare detection is independent of inclination. The two valuable properties of flares can be used to reveal the latitudinal distribution of active regions (LaDAR) given that LaDAR is coupled with inclination and location information in spatially unresolved stars. We detected $\sim 27000$ flares of 1510 flaring stars in the TESS mission with the corresponding inclinations obtained. The detection rate of flaring stars shows that flares are hard to detect on stars with low inclination, indicating that flares occur mainly at low latitudes. Further investigation of the relationship between the apparent flaring activity and inclination along with the rotation period finds that as the rotation period increases from a solar-like rotation to an ultra-fast rotation, the mean latitude of active regions increases from $\theta \approx 15^{\circ}$ to $\theta \approx 27^{\circ}$, whose trend is in line with the rotation--activity relationship. The LaDAR indicates that flares are attributed to small-scale fields that are formed at low latitudes, while polar spots that are associated with large-scale fields are inactive and are difficult to trigger flares.