Fig. 2. The schemes of the stellar surface with a dark spot and the corresponding best fits of the narrow spectral region 7705–7811 Å for four dates of observations.
The temperature increasing is interpreted as the changing of the surface area of a dark spot. Relative flux is calculated as a ratio of the flux at a particular wavelength (Fλ) to the flux in continuum (Fc). The observed spectra are shown as brown dots. The theoretical spectra (black solid curves) were calculated with the obtained parameters from Table 1 and convolved with the instrumental profile. Everywhere Vmic = 3 km s−1, V sini = 5 km s−1, Vmac = 16 km s−1. Titanium, carbon, nitrogen, and oxygen abundances are taken to be 4.95, 8.43, 8.60, and 8.80 dex, respectively. The molecular TiO (titanium oxide) lines are marked by vertical lines on each panel. a On 31-01-2020, the temperature of the spot is 3306 K if it occupies 50% of the surface area. b On 19-03-2020, the temperature of a spot is 3306 K if it occupies 33% of the surface area. c On 04-04-2020, the temperature of a spot is 3306 K if it occupies 10% of the surface area. d On 06-04-2020, the temperature of the whole star is 3646 K. Source data are provided as a Source Data file.