Imaging the 44 au kuiper belt-analogue debris ring around Hd 141569A with gpi polarimetry

We present the first polarimetric detection of the inner disk component around the pre-main sequence B9.5 star HD 141569A. Gemini Planet Imager H-band (1.65µm) polarimetric differential imaging reveals the highest signal-to-noise ratio detection of this ring yet attained and traces structure inwards to 0⁰⁰ . 25 (28 AU at a distance of 111 pc). The radial polarized intensity image shows the east side of the disk, peaking in intensity at 0⁰⁰ . 40 (44 AU) and extending out to 0⁰⁰ . 9 (100 AU). There is a spiral arm-like enhancement to the south, reminiscent of the known spiral structures on the outer rings of the disk. The location of the spiral arm is coincident with ¹²CO J=3–2 emission detected by ALMA, and hints at a dynamically active inner circumstellar region. Our observations also show a portion of the middle dusty ring at ∼220 AU known from previous observations of this system. We fit the polarized H-band emission with a continuum radiative transfer Mie model. Our best-fit model favors an optically thin disk with a minimum dust grain size close to the blow-out size for this system: evidence of on-going dust production in the inner reaches of the disk. The thermal emission from this model accounts for virtually all of the far-infrared and millimeter flux from the entire HD 141569A disk, in agreement with the lack of ALMA continuum and CO emission beyond ∼100 AU. A remaining 8–30µm thermal excess a factor of ∼2 above our model argues for a yet-unresolved warm innermost 5–15 AU component of the disk.