QUIESCENT X-RAY EMISSION FROM AN EVOLVED BROWN DWARF?

摘要

I report on the X-ray detection of Gl 569Bab. During a 25 ks Chandra observation, the binary brown dwarf is for the first time spatially separated in X-rays from the flare star primary Gl 569A. Companionship to Gl 569A constrains the age of the brown dwarf pair to ～300-800 Myr. The observation presented here is only the second X-ray detection of an evolved brown dwarf. About half of the observing time is dominated by a large flare on Gl 569Bab; the remainder is characterized by weak and nonvariable emission just above the detection limit. This emission—if not related to the afterglow of the flare—represents the first detection of a quiescent corona on a brown dwarf, representing an important piece in the puzzle of dynamos in the substellar regime.