High-contrast observations of brown dwarf companion HR 2562 B with the vector Apodizing Phase Plate coronagraph. Issue 3 (5th July 2021)

• Record Type: Journal Article
• Authors: Sutlieff, Ben J; Bohn, Alexander J; Birkby, Jayne L; Kenworthy, Matthew A; Morzinski, Katie M; Doelman, David S; Males, Jared R; Snik, Frans; Close, Laird M; Hinz, Philip M; Charbonneau, David
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 506:Issue 3(2021)
• Page Start: 3224
• Page End: 3238
• Publication Date: 2021-07-05
• Subjects: instrumentation: high angular resolution -- planets and satellites: atmospheres -- planets and satellites: detection -- brown dwarfs -- stars: individual: HR 2562 -- infrared: planetary systems; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1893
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: 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 $\mu\mathrm{ m}$ narrow-band contrast of (3.05 ± 1.00) × 10 −4 ($\Delta \, {\rm m}_{3.94 \mu {\rm m}}$ = 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 MJup, 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 $\mu\mathrm{ m}$ 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.