High-contrast observations of circumstellar environments with GTC/FRIDA: design and study of the coronagraphic devices

摘要

Over the past few years, several large ground-based facilities have enhanced their exoplanet direct imaging capabilities to observe planetary companions and debris disks around nearby stars. The Gran Telescopio Canarias (GTC) will soon have its first high-contrast capabilities with FRIDA. This near-infrared imager and integral field spectrograph will operate with GTCAO, the adaptive optics system of the telescope, to cover a broad range of astrophysical topics. In 2008, we performed preliminary studies to design a high-contrast mode for FRIDA. In this communication, we revisit these studies by investigating different options in coronagraphy to define a final high-contrast baseline for this instrument. Acknowledging the mechanical constraints of FRIDA and the GTCAO performance for high-contrast observations (60% Strehl ratio in K-band), we evaluate different options such as standalone pupil apodizations and classical Lyot coronagraphs to achieve a 10~(-5) contrast at 200-300 mas from an observed star over wide spectral bands. We then derive the adopted solutions for design and manufacturing of the prototypes. Finally, we discuss possible combinations of high-dispersion spectroscopy and high-contrast imaging for advanced exoplanet observations with this instrument.