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 χ2r 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 Rrim ≈ 0.1 au. Altogether, we find a very complex, substantially non-point symmetric and temporally variable disc (rout ≲ 6 au) around the primary. Conclusions. The very close-in inner rim indicates the presence of material within the typical wall-like sublimation radius, Rrim,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.