Characterization of the inner disk around HD 141569 A from Keck/NIRC2 L-band vortex coronagraphy

TL;DR

This study uses advanced L'-band vortex coronagraphy at Keck to image and analyze the inner disk of HD 141569 A, revealing its structure, dust composition, and potential faint sources within the disk gap.

Contribution

First high-contrast L'-band imaging of HD 141569 A's inner disk with vortex coronagraph, providing detailed disk characterization and dust composition analysis.

Findings

Inner disk detected from ~23 to 70 AU.

Dust likely composed of pure olivine grains.

No true companion detected within the gap.

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 micron) 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 $\simeq 23$ AU and up to $\simeq 70$ AU. The spatial scale of our detection roughly corresponds to the optical and near-infrared scattered light, thermal Q, N and 8.6 micron 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.