(Proposal ID) S12B-017

(PI) Narita, Norio

(Proposal Title)
Ascertaining Rayleigh Scattering in the Atmosphere of GJ1214b

(Abstract)
GJ1214b is a transiting super-earth orbiting around a nearby (13 pc) M dwarf 
GJ1214. Previous observations of transit depths in various wavelength bands 
have revealed that the planet has either a water-rich atmosphere or a hydrogen-
rich hazy atmosphere. To determine a conclusive atmosphere model of GJ1214b, 
we propose to conduct high precision Cousins B and V band transit photometry 
of GJ1214b to ascertain Rayleigh scattering in the atmosphere of this planet. 
Since GJ1214 is very faint in B (16.40 mag) and V (14.67 mag) bands, we 
definitely need the Subaru Suprime-Cam, which has a large (8.2~m) telescope 
aperture and a very wide (34'x 27') field of view, to achieve sufficient 
precision to ascertain Rayleigh scattering. The proposed transit observations 
in B and V bands will provide us new information of transit depths in the 
bluer region, where Rayleigh scattering in the atmosphere of GJ1214b is 
important. As a result, we will be able to answer whether GJ1214b is a water-
world or a hydrogen-rich hazy world. In addition, the proposed observations 
will demonstrate effectiveness of this kind of blue-band observations and 
encourage future similar studies for other transiting terrestrial planets 
around nearby M dwarfs.