# Frequent flare events on the short-period M-type eclipsing binary BX Tri

## TL;DR

This study documents frequent flare events on the short-period M-type eclipsing binary BX Tri, revealing high flare activity possibly linked to rapid mass transfer, and analyzes its evolutionary status and orbital period changes.

## Contribution

It provides the first long-term, multi-color photometric and spectroscopic observations of BX Tri, identifying six flares and analyzing their energies and implications for system evolution.

## Key findings

- Six flares observed over four years, with the strongest exceeding superflare energy levels.
- BX Tri is likely a semi-detached system with the primary filling its Roche lobe.
- High flare frequency may be related to rapid mass transfer between components.

## Abstract

We present long-term, multi-color photometric monitoring and spectroscopic observations of the short-period M-type eclipsing binary BX Tri. Six flare events were recorded in 4 years from 2014 to 2017. Three of them were detected on one night within an orbital cycle. The strongest one was identified on December 23, 2014. With the amplitudes of $\Delta$B=0.48 mag, $\Delta$V=0.28 mag, $\Delta$R=0.10 mag, $\Delta$I=0.02 mag, the total energy due to the flare event was measured to be 4.08 ($\pm$0.24) $\times$$10^{34}$ erg, exceeding the superflare level ($10^{34}$). Based on the observations, the evolutionary status of the binary system as well as the long-term orbital period changes were analyzed. It reveals that BX Tri is probably a semi-detached system with the primary component filling its Roche lobe. The extremely high occurrence of flare events of the binary could be related to the rapid mass transfer between components.