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We report the confirmation of HIP 67506 C, a new stellar companion to HIP 67506 A. We previously reported a candidate signal at 2λ/D (240 mas) in L ′ in MagAO/Clio imaging using the binary differential imaging technique. Several additional indirect signals showed that the candidate signal merited follow-up: significant astrometric acceleration in Gaia DR3, Hipparcos–Gaia proper motion anomaly, and overluminosity compared to single main-sequence stars. We confirmed the companion, HIP 67506 C, at 0.1 arcsec with MagAO-X in 2022 April. We characterized HIP 67506 C MagAO-X photometry and astrometry, and estimated spectral-type K7-M2; we also re-evaluated HIP 67506 A in light of the close companion. Additionally, we show that a previously identified 9 arcsec companion, HIP 67506 B, is a much further distant unassociated background star. We also discuss the utility of indirect signposts in identifying small inner working angle candidate companions. [ABSTRACT FROM AUTHOR]

Improving direct detection capability close to the star through improved star subtraction and post-processing techniques is vital for discovering new low-mass companions and characterizing known ones at longer wavelengths. We present results of 17 binary star systems observed with the Magellan adaptive optics system (MagAO) and the Clio infrared camera on the Magellan Clay Telescope using binary differential imaging (BDI). BDI is an application of reference differential imaging (RDI) and angular differential imaging (ADI) applied to wide binary star systems (2 arcsec <Δρ < 10 arcsec) within the isoplanatic patch in the infrared. Each star serves as the point spread function (PSF) reference for the other, and we performed PSF estimation and subtraction using principal component analysis. We report contrast and mass limits for the 35 stars in our initial survey using BDI with MagAO/Clio in L ′ and 3.95 µm bands. Our achieved contrasts varied between systems, and spanned a range of contrasts from 3.0 to 7.5 magnitudes and a range of separations from 0.2 to 2 arcsec. Stars in our survey span a range of masses, and our achieved contrasts correspond to late-type M-dwarf masses down to ∼10  M Jup. We also report detection of a candidate companion signal at 0.2 arcsec (18 au) around HIP 67506 A (SpT G5V, mass ∼1.2 M⊙), which we estimate to be |$\sim 60-90 \, \rm{M_{Jup}}$|⁠. We found that the effectiveness of BDI is highest for approximately equal brightness binaries in high-Strehl conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

NaSt1 (aka Wolf-Rayet 122) is a peculiar emission-line star embedded in an extended nebula of [N ii] emission with a compact dusty core. The object was previously characterized as a Wolf-Rayet (WR) star cloaked in an opaque nebula of CNO-processed material, perhaps analogous to n Car and its Homunculus nebula, albeit with a hotter central source. To discern the morphology of the [N ii] nebula we performed narrow-band imaging using the Hubble Space Telescope and Wide-field Camera 3. The images reveal that the nebula has a disc-like geometry tilted ≈12° from edge-on, composed of a bright central ellipsoid surrounded by a larger clumpy ring. Ground-based spectroscopy reveals radial velocity structure (±10 km s-1) near the outer portions of the nebula's major axis, which is likely to be the imprint of outflowing gas. Near-infrared adaptive-optics imaging with Magellan AO has resolved a compact ellipsoid of Ks-band emission aligned with the larger [N ii] nebula, which we suspect is the result of scattered Hei line emission (A2.06 m). Observations with the Chandra X-ray Observatory have revealed an X-ray point source at the core of the nebula that is heavily absorbed at energies < 1 keV and has properties consistent with WR stars and colliding-wind binaries. We suggest that NaSt1 is a WR binary embedded in an equatorial outflow that formed as the result of non-conservative mass transfer. NaSt1 thus appears to be a rare and important example of a stripped-envelope WR forming through binary interaction, caught in the brief Roche lobe overflow phase. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]