Very high contrast integral field spectroscopy of AB Doradus C: 9-mag contrast at 0.2 arcsec without a coronagraph using spectral deconvolution

Niranjan Thatte, Roberto Abuter, Matthias Tecza, Eric L. Nielsen, Fraser J. Clarke, Laird M Close

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

We present an extension of the spectral deconvolution (SD) method to achieve very high contrast at small inner working radii. We apply the method to the specific case of ground-based adaptive optics fed integral field spectroscopy (without a coronagraph). Utilizing the wavelength dependence of the Airy and speckle patterns, we make an accurate estimate of the point spread function that can be scaled and subtracted from the data cube. The residual noise in the resulting spectra is very close to the photon noise from the starlight halo. We utilize the technique to extract a very high signal-to-noise ratio H- and K-band spectrum of AB Doradus (AB Dor) C, the low-mass companion to AB Dor A. By effectively eliminating all contamination from AB Dor A, the extracted spectrum retains both continuum and spectral features. The achieved 1σ contrast is 9 mag at 0.2 arcsec, 11 mag at 0.5 arcsec, in 20 min exposure time, at an effective spectral bandwidth of 5.5 nm, proving that the method is applicable even in low-Strehl regimes. The SD method clearly demonstrates the efficacy of image slicer based integral field units in achieving very high contrast imaging spectroscopy at small angular separations, validating their use as high-contrast spectrographs/imagers for extreme adaptive optics systems.

Original languageEnglish (US)
Pages (from-to)1229-1236
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume378
Issue number4
DOIs
StatePublished - Jul 2007

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coronagraphs
deconvolution
spectroscopy
spectral methods
adaptive optics
speckle
speckle patterns
point spread functions
extremely high frequencies
signal-to-noise ratio
spectrographs
halos
contamination
signal to noise ratios
continuums
wavelength
bandwidth
radii
method
photons

Keywords

  • Binaries: close
  • Instrumentation: adaptive optics
  • Instrumentation: spectrographs
  • Stars: individual: AB Doradus C
  • Stars: low-mass, brown dwarfs

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Very high contrast integral field spectroscopy of AB Doradus C : 9-mag contrast at 0.2 arcsec without a coronagraph using spectral deconvolution. / Thatte, Niranjan; Abuter, Roberto; Tecza, Matthias; Nielsen, Eric L.; Clarke, Fraser J.; Close, Laird M.

In: Monthly Notices of the Royal Astronomical Society, Vol. 378, No. 4, 07.2007, p. 1229-1236.

Research output: Contribution to journalArticle

Thatte, Niranjan ; Abuter, Roberto ; Tecza, Matthias ; Nielsen, Eric L. ; Clarke, Fraser J. ; Close, Laird M. / Very high contrast integral field spectroscopy of AB Doradus C : 9-mag contrast at 0.2 arcsec without a coronagraph using spectral deconvolution. In: Monthly Notices of the Royal Astronomical Society. 2007 ; Vol. 378, No. 4. pp. 1229-1236.
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AU - Clarke, Fraser J.

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AB - We present an extension of the spectral deconvolution (SD) method to achieve very high contrast at small inner working radii. We apply the method to the specific case of ground-based adaptive optics fed integral field spectroscopy (without a coronagraph). Utilizing the wavelength dependence of the Airy and speckle patterns, we make an accurate estimate of the point spread function that can be scaled and subtracted from the data cube. The residual noise in the resulting spectra is very close to the photon noise from the starlight halo. We utilize the technique to extract a very high signal-to-noise ratio H- and K-band spectrum of AB Doradus (AB Dor) C, the low-mass companion to AB Dor A. By effectively eliminating all contamination from AB Dor A, the extracted spectrum retains both continuum and spectral features. The achieved 1σ contrast is 9 mag at 0.2 arcsec, 11 mag at 0.5 arcsec, in 20 min exposure time, at an effective spectral bandwidth of 5.5 nm, proving that the method is applicable even in low-Strehl regimes. The SD method clearly demonstrates the efficacy of image slicer based integral field units in achieving very high contrast imaging spectroscopy at small angular separations, validating their use as high-contrast spectrographs/imagers for extreme adaptive optics systems.

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