Authors

Laurent Pueyo (1), Justin Crepp (2), Sasha Hinkley (2), Ben Oppenheimer (3), Neil Zimmerman (3), Douglas Brenner (3), Gautam Vasisht (4)

Affiliations

(1) JPL/STScI. (2); Califormia Institute of Technology (3); American Museum of Natural History; (4) Jet Propulsion Laboratory

Abstract

The contrast floor of current telescopes is set by the light diffracted by the imperfection on the various surfaces of the their optical train. When these errors are very stable, in the case of a space observatory for instance, they can be calibrated and subtracted using reference observations. However, in the case of ground-based telescopes, these so called speckles are time dependent and refined observing scenarios associated with appropriate post-processing techniques need to be developed in order to discriminate real astronomical companions from fiducials due to optical imperfections. In this paper we report recent advances in speckle calibration obtained using the P1640 Integral Field Spectrograph, installed at the Palomar Hale telescope. We present a novel algorithm that combines wavelength diversity and optimized Point Spread Function subtraction in order to detect faint companions lying underneath Adaptive Optics residuals. We show how this method allowed us to increase the dynamic range of our images up to the photometric limit. Then we discuss a spectral calibration method that retrieves the spectrum of this faint companion independently of the gain and bias introduced by the PSF subtraction algorithm. The methods reported here could be adapted to future ground based exo-planet imaging instruments that will be equipped with Integral Field Spectrographs.