СПЕКТРАЛЬНЫЕ И ФОТОМЕТРИЧЕСКИЕ ИССЛЕДОВАНИЯ ГРУППЫ WR ЗВЕЗД

Abstract

Massive stars of spectral class O, leaving the Main Sequence (MS), are capable to lose their hydrogen envelopes. The remaining core begins to shrink, starting a sequence of nuclear reactions, the products of which are heavy elements C, N and O. The WR stage is an intermediate stage in the evolutionary path of massive stars to their final state: a neutron star or a black hole. WR stars play an important role in evolution: firstly, they enrich the interstellar medium with heavy elements, and secondly, they are considered as progenitors of supernovae and as possible sources of X-ray flares. This article presents preliminary results of observations of the group of WR stars. The spectra were obtained for three WC-type stars: WR 4, WR5, and WR154, and two WN-type stars: WR2 and WR3. On the basis of observational data, the absolute fluxes in the emission lines were obtained, the equivalent widths and half-widths of their profiles were determined. Comparison of our results for WR4, obtained over 2 nights, shows that in January 2021 the absolute fluxes in the emission lines decreased by 20% compared to the data of December 2020. Comparison with the data obtained in 1983-1984 did not reveal serious discrepancies in the results for WR4, but our values of the equivalent widths for WR5 turned out to be half as much. This may be due to an increase in the level of the continuum or due to decrease of the emission lines fluxes. Photometric observations were carried out for four WR stars, with WR4 and WR5 observed over three nights. Comparison with the earlier data shows an increase in the brightness of objects over the past 20 years: by 0m.2 - 0m.3 for WR2 and WR5 and by 0m.6 -0m. 8 for WR4 and WR3. So, at this stage, we have established the photometric variability of 4 WR stars: WR2, WR3, WR4, and WR5, as well as the spectral variability of at least two objects: WR4 and WR5.