Averaged intensity, photocenter, and FWHM spectra of LkCa 15 from top to bottom for the parallel (left) and perpendicular (right) slit orientations from position angles as indicated in the legend, both with the original spectral resolution (black dotted lines) and after rebinning (black solid lines). The horizontal dashed lines in the middle and bottom panels indicate the ±1σ levels for the rebinned spectra, corresponding to ±0.5 and ±0.9 mas for the photocenter and FWHM accuracies. The red lines shows a face-on disk/sphere model with inverse Gaussian profile and radius ~70 mas or ~11 au at 159 pc (see Sect. 3.2 and Appendix D).