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Release : 2000
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Book Synopsis Optimization of an Adaptive Optics System and Its Application to High-resolution Imaging Spectroscopy of T Tauri by :
Download or read book Optimization of an Adaptive Optics System and Its Application to High-resolution Imaging Spectroscopy of T Tauri written by . This book was released on 2000. Available in PDF, EPUB and Kindle. Book excerpt: The AO system ALFA of the Max-Planck institutes for astronomy and for extraterrestrial physics incorporates a Shack-Hartmann wavefront sensor and a laser guide star facility. An effective use of faint natural guide stars as well as the laser guide star requires optimized wavefront reconstruction algorithms. The centroid estimation algorithm was improved by pixel masking methods and by weighting the pixel intensities with their signal to noise ratio. To reconstruct the wavefront from sensor data, the least-squares algorithm was modified and a maximum a posteriori algorithm was developed. In addition, a microlens geometry which is perfectly adapted to the annular telescope pupil is presented. Most of the modifications were simulated, implemented in ALFA, and finally tested at the telescope. The combined effect is an improvement in limiting guide star brightness from about V = 11 to V = 14 under the very best observing conditions. The analysis shows that a gain of another half of a magnitude could be obtained by using a detector with virtually zero read-noise. In addition, the young stellar system T~Tauri was observed with AO assisted imaging and long-slit spectroscopy. In this way, the two stars T Tau N and T Tau S could be separated, and their near-infrared spectra were obtained individually. Only the Calar Alto observatory currently permits those observations. It turned out that both stars exhibit similar hydrogen recombination-line spectra, but only T Tau N shows features that arise in a stellar photosphere. By using speckle methods on AO compensated short exposures, the recently discovered 0.08' companion to T Tau S could be confirmed. In combination with published data, the parameter space of its orbit could be narrowed, and indication for a rather large mass of about 2 solar masses was found for T Tau S.
