# Detection of a giant white-light flare on an L2.5 dwarf with the Next Generation Transit Survey

## TL;DR

This paper reports the detection of one of the largest white-light flares from an ultracool L2.5 dwarf star, demonstrating NGTS's capability to study flaring activity in stars cooler than 2000 K.

## Contribution

First detection of a giant white-light flare on an L2.5 dwarf using NGTS, extending flare observations to ultracool stars below 2000 K.

## Key findings

- Flare energy estimated at 3.4×10^33 erg, surpassing solar flares.
- NGTS can effectively detect flares in ultracool dwarfs.
- The observed flare is among the largest from such stars.

## Abstract

We present the detection of a $\Delta V\sim$ -10 flare from the ultracool L2.5 dwarf ULAS J224940.13-011236.9 with the Next Generation Transit Survey (NGTS). The flare was detected in a targeted search of late-type stars in NGTS full-frame images and represents one of the largest flares ever observed from an ultracool dwarf. This flare also extends the detection of white-light flares to stars with temperatures below 2000 K. We calculate the energy of the flare to be $3.4^{+0.9}_{-0.7}\times10^{33}$erg, making it an order of magnitude more energetic than the Carrington event on the Sun. Our data show how the high-cadence NGTS full-frame images can be used to probe white-light flaring behaviour in the latest spectral types.