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Session 28 - Double Stars.
Display session, Tuesday, June 10
South Main Hall,
Recently CHARA has started using the Mount Wilson Institute Adaptive Optics system (MWI-AO) to complement its standard speckle program of binary star astrometry. The main goal of the adaptive optics program is to determine magnitudes of each individual component of these binaries, which will yield spectral types. The eventual aim is to combine the astrometric and photometric information, in order to calibrate the mass luminosity relationship. CHARA observed 80 known binaries using both the speckle and AO systems on six nights in 1996. The separation, position angle, and differential magnitudes in V, R and I filters are presented for these systems. B magnitude data are presented for 61 of the systems.
In addition to the study of known binaries, CHARA has also begun a survey of nearby stars for faint red companions. Twenty seven stars were observed in the I band. Six companions were observed, three of which were previously unknown. Confirming observations are currently underway and will be presented.
The MWI-AO system uses an unfiltered Shack-Hartmann wavefront sensor, and has only ten reflections in the optical path. These factors allow the system to go as faint as 12th magnitude. This ties in very well with the CHARA speckle program, which has a similar magnitude limit. The MWI-AO system uses a liquid nitrogen cooled 1024x1024 CCD. This allows a 22" field of view with the full chip, and a 5" view with the standard 256x256 subset. The 256x256 is normally used, because it reads out much faster, and most CHARA objects are much closer than 5". The system uses a 241 element deformable mirror, and the system can operate at 300-1000 Hz.
