4.7 Article

High-contrast observations of brown dwarf companion HR 2562 B with the vector Apodizing Phase Plate coronagraph

Journal

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 506, Issue 3, Pages 3224-3238

Publisher

OXFORD UNIV PRESS
DOI: 10.1093/mnras/stab1893

Keywords

instrumentation: high angular resolution; planets and satellites: atmospheres; planets and satellites: detection; brown dwarfs; stars: individual: HR 2562; infrared: planetary systems

Funding

  1. Netherlands Research School for Astronomy (NOVA)
  2. European Research Council (ERC) under the European Union [805445]
  3. Jet Propulsion Laboratory (JPL) - NASA through the Sagan Fellowship Program
  4. NASA Exoplanets Research Program (XRP) [NNX16AD44G]
  5. European Research Council [678194]
  6. Spanish MINECO [AyA2017-84089]
  7. European Union [776403]
  8. National Aeronautics and Space Administration
  9. National Science Foundation
  10. Chandra X-ray Science Center (CXC)
  11. High Energy Astrophysics Science Archive Center (HEASARC)
  12. JWST Mission office at the Space Telescope Science Institute for 3D visualization
  13. European Research Council (ERC) [805445] Funding Source: European Research Council (ERC)

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The vAPP coronagraph is effective in high-contrast imaging by modifying the PSF to create a dark hole for deep flux suppression. In this study, the vAPP coronagraph was used to recover the brown dwarf HR 2562 B in the L-band, with successful extraction of the companion using different processing techniques. The atmospheric modeling of HR 2562 B indicates a spectral type at the L/T transition, with varying effective temperature and surface gravity depending on the wavebands considered.
The vector Apodizing Phase Plate (vAPP) is a class of pupil plane coronagraph that enables high-contrast imaging by modifying the Point Spread Function (PSF) to create a dark hole of deep flux suppression adjacent to the PSF core. Here, we recover the known brown dwarf HR 2562 B using a vAPP coronagraph, in conjunction with the Magellan Adaptive Optics (MagAO) system, at a signal-to-noise of S/N = 3.04 in the lesser studied L-band regime. The data contained a mix of field and pupil-stabilized observations, hence we explored three different processing techniques to extract the companion, including Flipped Differential Imaging (FDI), a newly devised Principal Component Analysis (PCA)-based method for vAPP data. Despite the partial field-stabilization, the companion is recovered sufficiently to measure a 3.94 mu m narrow-band contrast of (3.05 +/- 1.00) x 10(-4) (Delta m(3.94 mu m) = 8.79 +/- 0.36 mag). Combined with archival GPI and SPHERE observations, our atmospheric modelling indicates a spectral type at the L/T transition with mass M = 29 +/- 15 M-Jup, consistent with literature results. However, effective temperature and surface gravity vary significantly depending on the wavebands considered (1200 <= T-eff(K) <= 1700 and 4.0 <= log(g)(dex) <= 5.0), reflecting the challenges of modelling objects at the L/T transition. Observations between 2.4 and 3.2 mu m will be more effective in distinguishing cooler brown dwarfs due to the onset of absorption bands in this region. We explain that instrumental scattered light and wind-driven halo can be detrimental to FDI+PCA and thus must be sufficiently mitigated to use this processing technique. We thus demonstrate the potential of vAPP coronagraphs in the characterization of high-contrast substellar companions, even in sub-optimal conditions, and provide new complementary photometry of HR 2562 B.

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