Paper: astro-ph/0601059
Date: Tue, 3 Jan 2006 23:14:48 GMT (403kb)

Title: Suppressing Speckle Noise for Simultaneous Differential Extrasolar
Planet Imaging (SDI) at the VLT and MMT

Authors: Beth A. Biller, Laird M. Close, Rainer Lenzen, Wolfgang Brandner,
Donald McCarthy, Eric Nielsen, Stephan Kellner, and Markus Hartung

Comments: 5 pages, 3 figures, 1 table. Presented at IAU Colloquium 200, Direct
Imaging of Exoplanets: Science and Techniques
\\
We discuss the instrumental and data reduction techniques used to suppress
speckle noise with the Simultaneous Differential Imager (SDI) implemented at
the VLT and the MMT. SDI uses a double Wollaston prism and a quad filter to
take 4 identical images simultaneously at 3 wavelengths surrounding the 1.62 um
methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By
performing a difference of images in these filters, speckle noise from the
primary can be significantly attenuated, resulting in photon noise limited data
past 0.5''. Non-trivial data reduction tools are necessary to pipeline the
simultaneous differential imaging. Here we discuss a custom algorithm
implemented in IDL to perform this reduction. The script performs basic data
reduction tasks but also precisely aligns images taken in each of the filters
using a custom shift and subtract routine. In our survey of nearby young stars
at the VLT and MMT (see Biller et al., this conference), we achieved H band
contrasts >25000 (5 sigma Delta F1(1.575 um) > 10.0 mag, Delta H > 11.5 mag for
a T6 spectral type object) at a separation of 0.5" from the primary star. We
believe that our SDI images are among the highest contrast astronomical images
ever made from ground or space for methane rich companions.

\\ ( http://arXiv.org/abs/astro-ph/0601059 , 403kb)