Characterization of the Inner Disk Around Hd 141569 a From Keck/Nirc2 L-Band Vortex Coronagraphy

Abstract

HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a new image of the third inner disk component of HD 141569 A made in the L' band (3.8 µm) during the commissioning of the vector vortex coronagraph recently installed in the near-infrared imager and spectrograph NIRC2 behind the W.M. Keck Observatory Keck II adaptive optics system. We used reference point spread function subtraction, which reveals the innermost disk component from the inner working distance of 23 AU and up to 70 AU. The spatial scale of our detection roughly corresponds to the optical and near-infrared scattered light, thermal Q, N and 8.6µm PAH emission reported earlier. We also see an outward progression in dust location from the L'-band to the H-band (VLT/SPHERE image) to the visible (HST/STIS image), likely indicative of dust blowout. The warm disk component is nested deep inside the two outer belts imaged by HST NICMOS in 1999 (respectively at 406 and 245 AU). We fit our new L'-band image and spectral energy distribution of HD 141569 A with the radiative transfer code MCFOST. Our best-fit models favor pure olivine grains, and are consistent with the composition of the outer belts. While our image shows a putative very-faint point-like clump or source embedded in the inner disk, we did not detect any true companion within the gap between the inner disk and the first outer ring, at a sensitivity of a few Jupiter masses.

Spiral Arms in Disks: Planets or Gravitational Instability?

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HD 104860 and HD 192758: Two Debris Disks Newly Imaged in Scattered Light with the Hubble Space Telescope

“…We find a relatively low value for the Henyey-Greenstein parameter of anisotropic scattering, with =  | | g 0.17 0.13, indicative of grains favoring forward scattering. This value is expected for a disk of moderate inclination such as HD104860, which does not Golimowski et al 2011;Mawet et al 2017). As mentioned before, this may not be representative of the SPF at smaller scattering angles, as it was shown that, for some dust grains, it may significantly differ from a HenyeyGreenstein model and sharply peak at angles below 40°despite a relatively flat phase function at large angles (Hedman & Stark 2015; Milli et al 2017b).…”

Subwavelength diamond gratings for vortex coronagraphy: towards an annular groove phase mask for shorter wavelengths and topological charge 4 designs

“…Even so, progress is being made in the fields of direct imaging of exoplanets [1] and characterization of proto-star systems [2,3]. This progress is likely to accelerate due to a new generation of 30 m-class telescopes, such as the European ELT, already under construction.…”

“…A method for increasing or decreasing the depth of the grating for the L-band has been developed [7], which allows optimization of the phase mask rejection ratio. The phase masks have been installed in infrared coronagraphic instruments (N-and L-band) on several 10-m class telescopes (VLT/NACO [8], VLT/VISIR [9], LBT/LMIRCam [10] and Keck/NIRC2 [1][2][3]) around the world. Following the success of these infrared coronagraphs, AGPMs for the NIR (1-3 μm) and ultimately for VIS (400-700 nm) spectral bands have become attractive, in particular for current high contrast instruments like VLT/SPHERE.…”