2019MNRAS.485.3558I

The results of spectral monitoring of the Hα and Hβ hydrogen lines for the supergiant star HD 199478 (B8Iae) are presented. Our observations have shown that the profiles of the spectral lines under consideration can remain unchanged over a period of 18-24 days. The most probable characteristic time of variability revealed in the hydrogen line parameters is 22 ± 2 days, which may be due to the axial rotation period of the star. During the observing season of 2011, we discovered a high-velocity absorption (HVA) event with a maximal shift of -510 km s^–1 that continued for at least 13 days. HVA was also detected in the Hβ line for the first time, which was observed simultaneously with that of the Hα line. The broad emission in the Hα line with a maximal shift of ±300 km s^–1 was observed in both the blue and red wings, irrespective of the central Nα emission. Quasi-cyclic smooth variability of the Hα and Hβ spectral parameters was discovered, with a maximum full cycle of 90-100 days. The equivalent widths of the Hα emission core and Hβ absorption vary in counterphase, which indicates that the emission contributes to the Hβ absorption line. The observed variability in the star's atmosphere is probably related to the axial rotation and the inhomogeneous structure of the atmosphere, its activity probably maintained by a magnetic field.