14 July 2010 High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM
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In this paper, we present an original observational approach, which combines, for the first time, traditional speckle imaging with image post-processing to obtain in the optical domain diffraction-limited images with high contrast (10-5) within 0.5 to 2 arcseconds around a bright star. The post-processing step is based on wavelet filtering an has analogy with edge enhancement and high-pass filtering. Our I-band on-sky results with the 2.5-m Nordic Telescope (NOT) and the lucky imaging instrument FASTCAM show that we are able to detect L-type brown dwarf companions around a solar-type star with a contrast ▵I~12 at 2 and with no use of any coronographic capability, which greatly simplifies the instrumental and hardware approach. This object has been detected from the ground in J and H bands so far only with AO-assisted 8-10 m class telescopes (Gemini, Keck), although more recently detected with small-class telescopes in the K band. Discussing the advantage and disadvantage of the optical regime for the detection of faint intrinsic fluxes close to bright stars, we develop some perspectives for other fields, including the study of dense cores in globular clusters. To the best of our knowledge this is the first time that high contrast considerations are included in optical speckle imaging approach.
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Lucas Labadie, Rafael Rebolo, Bruno Femenía, Isidro Villó, Anastasio Díaz-Sánchez, Alejandro Oscoz, Roberto López, Jorge A. Pérez-Prieto, Antonio Pérez-Garrido, Sergi R. Hildebrandt, Victor Béjar-Sánchez, Juan José Piqueras, and Luis Fernando Rodríguez "High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM", Proc. SPIE 7735, Ground-based and Airborne Instrumentation for Astronomy III, 77350X (14 July 2010); doi: 10.1117/12.857998; https://doi.org/10.1117/12.857998

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