The asymmetric structure of the inner disc around HD 142527 A with VLTI/MATISSE
Abstract
Circumstellar discs, and especially their inner regions, covering ranges from <1 au to a few astronomical units, are the birthplaces of terrestrial planets. The inner regions are thought to be similarly diverse in structure as the well-observed outer regions probed by ALMA. Combining data and results from previous studies of 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. We model the multi-wavelength interferometric data using a parametrised, geometrically thin disc model, allowing for azimuthal asymmetry, exploring a first-order disc modulation and an off-centre Gaussian component. 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 2r 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. All together, we find a very complex, substantially non-point symmetric and temporally-variable disc (rout6 au) around the primary. The very close-in inner rim indicates the presence of material inside 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 passing (~5 au) and short orbit (P≈24 yr) of the companion HD 142527 B.