The asymmetric structure of the inner disc around HD 142527 A with VLTI/MATISSE

Context . Circumstellar discs, and especially their inner regions, which cover ranges from less than 1 au to a few au, are the birthplaces of terrestrial planets. The inner regions are thought to be as diverse in structure as the well-observed outer regions probed by ALMA. Aims . By combining data and results from previous studies using the VLTI/PIONIER and VLTI/GRAVITY instruments with new, multi-epoch VLTI/MATISSE observations, we aim to provide a comprehensive picture of the structure of the inner regions of the circumstellar disc around the F-type Herbig Ae/Be star HD 142527 A, the primary of a binary star system. Methods . We modelled the multi-wavelength interferometric data using a parametrised, geometrically thin disc model, allowing for azimuthal asymmetry, and exploring a first-order disc modulation and an off-centre Gaussian component. Results . We find time-variable structures in the N -band observables, which we reproduce with time-dependent models. This variability manifests as azimuthally asymmetric emission, evidenced by strong, non-zero closure phases in the N -band data. Fits to individual epochs of the N -band observations yield better χ 2 r values than fits to all epochs simultaneously. This suggests substantial changes in the geometry of the inner disc emission from ∼1 au up to a few astronomical-unit scales from one year to the next. Moreover, our models produce a very close-in inner disc rim R rim ≈ 0.1 au. Altogether, we find a very complex, substantially non-point symmetric and temporally variable disc ( r out ≲ 6 au) around the primary. Conclusions . The very close-in inner rim indicates the presence of material within the typical wall-like sublimation radius, R rim,literature ≈ 0.3 au. The complex, temporally variable inner-disc geometry is likely affected, or even caused by, the close passage (∼5 au) and short orbit ( P ≈ 24 yr) of the companion HD 142527 B.

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