Fe II (4583.83 Å), Ti II (4443.80 Å), and Ca II K lines of HD 37306. While most of the spectra, represented by the median spectrum in the plot (black line), do no vary and show two Ca II non-photospheric absorptions, a strong shell-like profile appeared in September 2017 (red line, FEROS). It was not observed again in later spectra in November and December 2018, which are not shown in this figure. The red vertical line marks the radial velocity of the star.