Many groups are trying to find faint stellar companions using a variety of techniques. The most obvious is to take long exposure pictures. Here adaptive optics (AO) is useful in correcting the blurring effects of the atmosphere. Starlight is concentrated into a tighter peak and less energy is put into the surrounding halo. Another method is to look for periodic decreases in a star's irradiance due to a planet blocking some of the light as it crosses in front of the star or transits. The most productive technique so far has been to look for periodic doppler shifts in the light coming from a candidate star, i.e. radial velocity searches. Several large planets have been found this way. This dissertation explores aspects of these three methods. The ability to detect a companion amid noise depends on the properties of the noise. While theoretical expectations exist for the properties of the halo produced by an AO system, experimental studies are few. The temporal and spatial characteristics of the halo produced by the AO system at the Starfire Optical Range are explored from the viewpoint of searching for faint stellar companions. We set limiting companion magnitudes for stars imaged while searching for brown dwarfs. The primary limitation to ground based transit searches is scintillation, irradiance fluctuations due to atmospheric turbulence. We explore reduction of this noise via differencing signals from binary stars. Theory is extended to include temporal and angular separation effects simultaneously. Evaluation of the derived equations and simulations demonstrate the benefits and limitations. Finally the design of an echelle spectrograph for use on the 6.5 m MMT or the Magellan telescope that is well suited to radial velocity searches for planets is presented. It has throughput between 10% and 18%, resolution of 200,000 per pixel and can sample the entire 0.31 to 1.1 μm range at once. This is accomplished by avoiding metallic reflections whenever possible and by using a mosaic of CCDs fit to the curved focal surface of a Schmidt camera. Efficient simultaneous observation of many spectral lines makes this a powerful instrument for radial velocity companion searches.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/290663 |
| Date | January 1996 |
| Creators | Ryan, Patrick Thomas |
| Contributors | Angel, J. R. P. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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