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The time variability and spectra of directly imaged companions provide insight into their physical properties and atmospheric dynamics. We present follow-up R ∼ 40 spectrophotometric monitoring of red companion HD 1160 B at 2.8–4.2  μ m using the double-grating 360° vector Apodizing Phase Plate (dgvAPP360) coronagraph and ALES integral field spectrograph on the Large Binocular Telescope Interferometer. We use the recently developed technique of gvAPP-enabled differential spectrophotometry to produce differential light curves for HD 1160 B. We reproduce the previously reported ∼3.2 h periodic variability in archival data, but detect no periodic variability in new observations taken the following night with a similar 3.5 per cent level precision, suggesting rapid evolution in the variability of HD 1160 B. We also extract complementary spectra of HD 1160 B for each night. The two are mostly consistent, but the companion appears fainter on the second night between 3.0–3.2  μ m. Fitting models to these spectra produces different values for physical properties depending on the night considered. We find an effective temperature T eff  =  |$2794^{+115}_{-133}$|  K on the first night, consistent with the literature, but a cooler T eff  =  |$2279^{+79}_{-157}$| K on the next. We estimate the mass of HD 1160 B to be 16–81  M Jup, depending on its age. We also present R  = 50 000 high-resolution optical spectroscopy of host star HD 1160 A obtained simultaneously with the PEPSI spectrograph. We reclassify its spectral type to A1 IV-V and measure its projected rotational velocity |$\upsilon \sin i$| =  |$96^{+6}_{-4}$|  km s−1. We thus highlight that gvAPP-enabled differential spectrophotometry can achieve repeatable few per cent level precision and does not yet reach a systematic noise floor, suggesting greater precision is achievable with additional data or advanced detrending techniques. [ABSTRACT FROM AUTHOR]

We present diffraction-limited Ks band and L′ adaptive optics images of the edge-on debris disk around the nearby F2 star HD 15115, obtained with a single 8.4 m primary mirror at the Large Binocular Telescope. At the Ks band, the disk is detected at signal-to-noise per resolution element (SNRE) ∼ 3-8 from ∼1 to 2.″5 (45-113 AU) on the western side and from ∼1.″2 to 2.″1 (63-90 AU) on the east. At L′ the disk is detected at SNRE ∼ 2.5 from ∼1 to 1.″45 (45-90 AU) on both sides, implying more symmetric disk structure at 3.8 μm. At both wavelengths the disk has a bow-like shape and is offset from the star to the north by a few AU. A surface brightness asymmetry exists between the two sides of the disk at the Ks band, but not at L′. The surface brightness at the Ks band declines inside 1″ (∼45 AU), which may be indicative of a gap in the disk near 1″. The Ks – L′ disk color, after removal of the stellar color, is mostly gray for both sides of the disk. This suggests that scattered light is coming from large dust grains, with 3-10 μm sized grains on the east side and 1-10 μm dust grains on the west. This may suggest that the west side is composed of smaller dust grains than the east side, which would support the interpretation that the disk is being dynamically affected by interactions with the local interstellar medium. [ABSTRACT FROM AUTHOR]