Other
Scientific paper
Apr 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994pasp..106..356w&link_type=abstract
Publications of the Astronomical Society of the Pacific, vol. 106, no. 698, p. 356-362
Other
12
Companion Stars, Extrasolar Planets, Faint Objects, Imaging Techniques, Astronomical Photometry, Charge Coupled Devices, Detection, White Dwarf Stars
Scientific paper
The ability to detect directly close, faint companions to bright stars depends on image sharpness to a high power (6-8 in the case of a planet). We present the first observations with a coronographic mode of the high-resolution camera on the CFH 3.6-m telescope. About 98% of the light of the guide star fell through a 5 arcsec hole and the wings of the image were well represented by a Moffat profile. Chopping in angle did not reduce glare in the wings as much as we expected because of eccentricity of the star in the aperture, residual asymmetry in the point-spread function, and weak radial patterns (in addition to those from the spider). Combining an angular chop with the image of another star to give an instrumental psf was more successful. We discuss the recognition and the photometry of a faint star in the field of sigma Draconis. Snapshots of Procyon yielded a separation of 5.2 arcsec, mv=11.3, B-V=+0.26, and B-I=+0.62 for its white-dwarf companion. The detection limits close to sigma Dra, tau Ceti, and epsilon Eridani are still some five magnitudes too bright for the detection of giant planets. Nonetheless, we remain optimistic that, with improved centering, the introduction of frame-transfer CCDs, longer exposure times in the 15% seeing at CFHT, and the use of other stars to define the telescope psf and fixed speckle background, it may be possible to realize these limits. Alt-azimuth telescopes present a special challenge]
Fletcher Murray J.
McClure Robert D.
Racine Rene
Walker Andrew R.
Walker Gordon A.
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