The complex inner disk of the Herbig Ae star HD 100453 with VLTI/MATISSE

Context. The inner regions of planet-forming disks hold invaluable insights for our understanding of planet formation. The inner disk regions that might be affected by already formed planets are of particular interest. The disk around the Herbig star HD 100453 presents one such environment, with an inner disk that is significantly misaligned with respect to the outer disk. Aims. This paper expands the existing H band (PIONIER) and K band (GRAVITY) interferometric studies of the inner disk of HD 100453 to the L band with the MATISSE VLTI instrument. Based on snapshot data spanning approximately four years, we aim to understand the inner disk structures and their potential time evolution better. Methods. Based on the MATISSE data we obtained, we used a combination of analytical models and image reconstruction to constrain the disk structure. Additionally, we fitted a temperature gradient model to the selected wavelength range of PIONIER, GRAVITY, and MATISSE to derive the physical properties of the inner regions. Results. Our parametric model determined an inclination of ≈47.5° and a position angle of ≈83.6°, which corroborates the strong misalignment of the inner to the outer disk. From the symmetric temperature gradient, we derive an inner disk radius of ≈0.27 au, with dust surface densities of Σsubl ≈ 10−3.2 g/cm2 and a vertical optical depth τz,subl ≈ 0.1-0.06. Same-night MATISSE and GRAVITY observations show directional discrepancies that are inconsistent with a first-order azimuthally modulation ring. This indicates that higher-order asymmetries are required to explain the interferometric signals. This interpretation is further supported by a MATISSE snapshot image reconstruction that revealed a two-component asymmetric structure. Conclusions. The chromatic interferometric data reveal that higher-order asymmetries are probably required to explain the inner disk of HD 100453, which suggests a possible origin in dynamic interactions or disk instabilities. Coordinated multi-wavelength infrared interferometric observations with GRAVITY and MATISSE will be crucial to confirm these findings and uncover their underlying nature.