Fast Photometric Variability of Very Low Mass Stars in IC 348: Detection of Superflare in an M-dwarf

TL;DR

This study investigates rapid optical variability in very low mass stars and brown dwarfs in IC 348, discovering new periodicities, a superflare, and insights into their magnetic activity and rotation.

Contribution

It provides the first detection of superflare activity in young M-dwarfs and brown dwarfs, revealing rapid variability and magnetic phenomena in these low-mass objects.

Findings

22 new variable M-dwarfs and BDs identified

Periodic variability observed in 11 objects with 3.5-11 hour periods

Detected a superflare with energy close to 10^{35} ergs

Abstract

We present here optical I-band photometric variability study down to $\simeq$ 19 mag of a young ($\sim$2-3 Myr) star-forming region IC 348 in the Perseus molecular cloud. We aim to explore the fast rotation (in the time-scales of hours) in Very Low Mass stars (VLMs) including Brown Dwarfs (BDs). From a sample of 177 light-curves using our new I-band observations, we detect new photometric variability in 22 young M-dwarfs including 6 BDs, which are bonafide members in IC 348 and well-characterized in the spectral type of M-dwarfs. Out of 22 variables, 11 M dwarfs including one BD show hour-scale periodic variability in the period range 3.5 - 11 hours and rest are aperiodic in nature. Interestingly, an optical flare is detected in a young M2.75 dwarf in one night data on 20 December 2016. From the flare light curve, we estimate the emitted flared energy of 1.48 $\times$ 10$^{35}$ ergs. The observed flared energy with an uncertainty of tens of per cent is close to the super-flare range ($\sim$ 10$^{34}$ ergs), which is rarely observed in active M dwarfs.