TESS Photometric Variability of Young Brown Dwarfs in the Taurus Star-forming Region

Abstract

We present a comprehensive analysis of TESS high-quality light curves from sectors 43 and 44 of a few samples of young (∼2–3 Myr) brown dwarfs in the Taurus molecular cloud. They are well characterized and bona fide members of Taurus. We aim to search for the fast rotations of brown dwarfs and to picturize their dynamic atmosphere and surface features. Out of 11 young BDs, we found that 72% are periodic, in the period range of 1–7 days; among them, three BDs have periods <1.5 day and the period of one object is estimated for the first time. The sinusoidal periodic variations are related to a large spot or group of small spots corotating with the objects. Interestingly, we have detected four flare events in three young BDs, with one object, MHO 4, showing two flares in two different sectors. From the flared light curves, we have estimated the total bolometric flared energy in a range of 10 ^35 –10 ^36 erg, which is close to the superflare energy range (≥10 ^34 erg). To produce such kinds of superflare events, we have calculated the required magnetic field strength, which comes out at the order of a few kilogauss. Such superflares have a strong effect on the habitability of planets around M dwarfs.

Keywords

• Variable stars
• Stellar flares
• Stellar activity
• M dwarf stars
• Starspots
• Stellar rotation