(Proposal ID) S16B-050

(PI) Sorahana, Satoko

(Proposal Title)
Searching for the Cause of Variability of Brown Dwarfs with NIR Spectroscopy

(Abstract)
We propose simultaneous H and K band spectroscopic monitoring observations of 
brown dwarfs (BDs) using the grism mode of MOIRCS/Subaru, with R~500. 
Photometry and spectroscopy of BDs have been carried out to understand their 
atmosphere, in which prominent spectroscopic features are created by low-
temperature processes such as molecular chemistry and dust formation/
sedimentation. Photometric monitoring revealed that some BDs are variable 
with periods order of several hours. We plan to spectroscopically monitor 
two BDs which show photometric variability with amplitudes of 2.9 and 17%. We 
have constructed a phenomenological model (temperature structure) to explain 
the observed photometric variability. To probe the background physical 
processes of the temperature structure, we obtain simultaneous spectroscopy 
of molecular lines to investigate their variability.