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The debris disc around HD 172555 was recently imaged in near-infrared polarised scattered light by the Very Large Telescopes Spectro-Polarimetric High-contrast Exoplanet REsearch instrument. Here we present optical aperture polarisation measurements of HD 172555 by the HIgh Precision Polarimetric Instrument (HIPPI), and its successor HIPPI-2 on the Anglo-Australian Telescope. We seek to refine constraints on the discs constituent dust grains by combining our polarimetric measurements with available infrared and millimetre photometry to model the scattered light and continuum emission from the disc. We model the disc using the 3D radiative transfer code Hyperion, assuming the orientation and extent of the disc as obtained from the SPHERE observation. After correction for the interstellar medium contribution, our multi-wavelength HIPPI/-2 observations (both magnitude and orientation) are consistent with the recent SPHERE polarisation measurement with a fractional polarisation $p = 62.4 pm 5.2$~ppm at 722.3 nm, and a position angle $theta = 67 pm 3^{circ}$. The multi-wavelength polarisation can be adequately replicated by compact, spherical dust grains (i.e. from Mie theory) that are around 1.2 $mu$m in size, assuming astronomical silicate composition, or 3.9 $mu$m assuming a composition derived from radiative transfer modelling of the disc. We were thus able to reproduce both the spatially resolved disc emission and polarisation with a single grain composition model and size distribution.
We present multi-epoch infrared photometry and spectroscopy obtained with warm Spitzer, Subaru and SOFIA to assess variability for the young ($sim$20 Myr) and dusty debris systems around HD 172555 and HD 113766A. No variations (within 0.5%) were foun
We describe the incorporation of polarized radiative transfer into the atmospheric radiative transfer modelling code VSTAR (Versatile Software for Transfer of Atmospheric Radiation). Using a vector discrete-ordinate radiative transfer code we are abl
Debris disks or belts are important signposts for the presence of colliding planetesimals and, therefore, for ongoing planet formation and evolution processes in young planetary systems. Imaging of debris material at small separations from the star i
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The absorption of stellar radiation observed by the HD209458b in resonant lines of OI and CII has not yet been satisfactorily modeled. In our previous 2D simulations we have shown that the hydrogen-dominated upper atmosphere of HD209458b, heated by X