IA/U.Lisboa Seminar - Fast Line Profile Variations in spectra of OBA and a Nature of GW Precursors - 8 novembro 2016

Saint-Petersburg University, Russia

 

 

We review the results of our looking for fast line profile variations (LPVs) in spectra of OBA stars. Recent observations of selected stars using FOcal Reducer low dispersion Spectrographs FORS 1 and FORS 2 in spectropolarimetric mode mounted on the 8-m VLT telescopes show the strong LPV in spectra of magnetic OBA stars. The presence of short-term spectral variability in massive OBA stars, which are proposed to be the progenitors of Type II supernova was not studied systematically studies before and can be critical for the current theoretical understanding of their physics. We reveal the moderate line profile variations of various lines on a time-scale of minutes and a fraction of a minute in FORS 2 spectra of the A0 supergiant HD 92207. The possibility of such short time-scale LPVs for OBA stars was recently confirmed by our high time resolution spectra observations spectra of HD93521 (O9.5III) with the multi-mode focal reducer SCORPIO at the 6-meter telescope BTA of the Special Astrophysical Observatory (Northern Caucasus, Russia). We propose the programs of searching the short-term LPVs for binary OBA stars with the relativistic components (neutron star or black hole), which are the precursors of the power gravitational wave sources. The preliminary list of targets includes the High Mass X-ray Binaries Cyg X-1 and X Persei is given. The impact of binarity on the pattern of the short-term periodicity is discussed.