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G. Doppmann, O. Ershov, P. M. Harvey, D. T. Jaffe, L. Keller (UT Austin)
Dynamic range is a critical performance criterion for systems designed to detect faint substellar companions to bright stars. One approach to improving dynamic range is to take advantage of spectral differences between the substellar objects and the stars. We present here a technique for detection of substellar objects closer to the parent star than possible with coronagraphs and with larger brightness differences than possible with direct imaging. The technique involves simultaneous short exposure imaging on and off spectral features of the substellar objects (for example, the methane absorption feature at 2.21 microns), and use of shift and add and/or speckle techniques to analyze spectral difference images. The technique will also significantly improve the dynamic range of adaptive optics of faint companions near bright primaries. We present the optical design of a prototype dichroic speckle imaging system that produces diffraction limited images of a 10 arcsec field in 2 adjacent quadrants of a NICMOS3 256 x 256 detector array. We discuss recent preliminary field tests of this device on the 2.7m Harlan Smith Telescope.
The author(s) of this abstract have provided an email address for comments about the abstract: greg@astro.as.utexas.edu