Abstrakt
The B[e] phenomenon can be present in stars of different types and at different evolutionary stages. Very extended circumstellar matter prohibits the study of the atmosphere of these stars, since no photospheric lines are usually observed.
Standard stellar atmosphere models are thus not applicable when determining stellar parameters. One of a few possibilities for comprehending the nature of these objects is to study their time variations.
Unfortunately, almost no set of spectra with an adequate time description is available for these objects. We obtained an extensive set of MWC 342 spectra (102) during the years 2004-2010 in the wavelength interval around the Ha line (6265-6765 angstrom) to focus on the time variability of the spectral lines in this region.
We chose MWC 342 from the known stars showing the B[e] phenomenon since, although this star is very bright, its evolutionary status and the role of binarity in the appearance of the B[e] phenomenon are unknown. The time dependence of radial velocities and equivalent widths of emission lines was measured for the Ha line, He I 6678 angstrom, [OI] 6300, 6364 angstrom, Fe II 6318, 6384, 6344 and 6456 angstrom, and Si II 6347, 6371 angstrom.
We detected variability in the spectral lines on both short and long time scales.