SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star ^*

Abstract

We present the direct imaging discovery of a substellar companion to the nearby Sun-like star, HD 33632 Aa, at a projected separation of ∼20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5σ astrometric acceleration on the star as detected with the Gaia and Hipparcos satellites. SCExAO/CHARIS JHK (1.1-2.4 μm) spectra and Keck/NIRC2 L p (3.78 μm) photometry are best matched by a field L/T transition object: an older, higher-gravity, and less dusty counterpart to HR 8799 cde. Combining our astrometry with Gaia/Hipparcos data and archival Lick Observatory radial velocities, we measure a dynamical mass of 46.4±8 M J and an eccentricity of e < 0.46 at 95% confidence. HD 33632 Ab's mass and mass ratio (4.0% ± 0.7%) are comparable to the low-mass brown dwarf GJ 758 B and intermediate between the more massive brown dwarf HD 19467 B and the (near-)planet-mass companions to HR 2562 and GJ 504. Using Gaia to select for direct imaging observations with the newest extreme adaptive optics systems can reveal substellar or even planet-mass companions on solar system-like scales at an increased frequency compared to blind surveys. Unified Astronomy Thesaurus concepts: Exoplanets (498); Brown dwarfs (185); Astronomical instrumentation (799); Astronomical optics (88); Direct imaging (387); Coronagraphic imaging (313); Exoplanet detection methods (489); Astronomical techniques (1684)

SCExAO/MEC and CHARIS Discovery of a Low-mass, 6 au Separation Companion to HIP 109427 Using Stochastic Speckle Discrimination and High-contrast Spectroscopy*

“…The broadband and H band flux densities agree to within 1σ except at ∼1.45 μm, where telluric absorption is strongest. The CHARIS spectra show clear local minima at 1.4 μm and 1.8-2.0 μm, consistent with absorption from water opacity (e.g., Currie et al 2020a). In the standard Maunakea Observatory bandpasses, HIP 109427 B photometry drawn from the CHARIS broadband spectrum and NIRC2 imaging data is J = 10.62 ± 0.10, H = 10.30 ± 0.07, K s = 10.02 ± 0.11, and L p = 9.58 ± 0.13.…”

“…Astrometry derived from the Hipparcos-Gaia Catalogue of Accelerations (HGCA; Brandt 2018) reveals a substantial deviation from simple linear kinematic motion (χ 2 = 108.83) consistent with a ∼11σ-significant acceleration. We therefore targeted this star as a part of our survey to discover low-mass companions to accelerating stars (e.g., Currie et al 2020a).…”

“…Following recent work (Currie et al 2020a), we compared the CHARIS spectra for HIP 109427 B to entries in the Montreal Spectral Library 21 (e.g., Gagné et al 2015), considering the impact of spatially and spectrally correlated noise (Greco & Brandt 2016). 22 The CHARIS data reveal highly correlated errors (Figure 3, right panel).…”

First on-sky demonstration of spatial Linear Dark Field Control with the vector-Apodizing Phase Plate at Subaru/SCExAO

“…It operates downstream of the AO188 system (Minowa et al 2010), which provides an initial, low-order correction to the incoming wavefront. The main WFS of SCExAO is a visible Pyramid wavefront with an operational wavelength range of 600-900 nm (Lozi et al 2019 In addition to enabling high-contrast science (e.g., Goebel et al 2018;Lawson et al 2020;Currie et al 2020a), SCExAO is serving as a technology demonstration testbed and it has tested many different FPWFSs on-sky (Martinache et al 2014;Martinache et al 2016;N'Diaye et al 2018;Bos et al 2019;Vievard et al 2019;.…”

Constraints on the nearby exoplanet ϵ Indi Ab from deep near- and mid-infrared imaging limits

“…Calissendorff & Janson 2018) or all three (e.g. Brandt et al 2019;Grandjean et al 2019;Currie et al 2020) has been achieved in a number of cases, encouraging increasing efforts in recent years to use similar approaches to detect and characterise exoplanets (e.g. Mawet et al 2019).…”