Spectral variability of luminous early type stars. I. Peculiar supergiant HD199478

Details Spectral variability of luminous early type stars. I. Peculiar supergiant HD199478 Spectral variability of luminous early type stars. I. Peculiar supergiant HD199478

Nov 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000a%26a...363..995m&link_type=abstract

Astronomy and Astrophysics, v.363, p.995-1004 (2000)

Astronomy and Astrophysics

Astrophysics

10

Line: Profiles, Stars: Early-Type, Stars: Emission-Line, Be, Stars: Individual: Hd 199478

Scientific paper

We have obtained time-series of high-quality Hα spectra with high resolution in wavelength (R = lambda /delta lambda of 15000 to 22000) and time (Delta t =1d) of the late-type B supergiant HD199478. The spectra were analysed in terms of line-profile variability (lpv) using contemporary techniques of time-series analysis, such as Temporal Variance Spectrum and the 2d- Discrete Fourier Transform. The Hα profile is found to consist of a highly variable emission core (between -280 and +150 km s-1) superimposed on almost constant, extended (+/-1000 km s-1) emission wings. Due to the lack of strong line-emission, the latter is attributed to electron-scattering in deep atmospheric layers. The Hα variability manifests itself by variations in velocity and intensity of blue- and red-shifted emission peaks, which result in drastic alterations in the shape of the profile from almost symmetric and unshifted emission, with respect to the stellar rest frame, through blue- or red-shifted asymmetric emission, to double-peaked emission or a reverse P Cygni-type profile. Significant variations in total emissivity (i.e. EW) of the line are also noted, but these variations do not appear to be obviously linked to changes in the line-profile shape. The pattern of variability resembles that in Be-stars - though on a much shorter time scale - and suggests interpretation in terms of an axially symmetric and perturbed stellar wind. Since the time-scale of the V/R variations is found to be 3 to 5 times longer than the radial fundamental pulsation period but consistent with rotational period, rotational modulation as a possible cause for this variability is considered. Besides variations in Hα , continuous changes in velocity (typical dispersion of sigma ~ 5 km s-1) and strength, i.e. EW, (up to 13% of the mean) of a sample of three absorption lines (CII lambda lambda6583 , 6578 and HeI lambda6678 ) were also observed. The phenomenon observed is more likely connected to changes in velocity and temperature structures of the stellar photosphere. Pulsation instability as a possible cause of photospheric variability is suggested.

Affiliated with

Also associated with

No associations

Rating

Spectral variability of luminous early type stars. I. Peculiar supergiant HD199478 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Spectral variability of luminous early type stars. I. Peculiar supergiant HD199478, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spectral variability of luminous early type stars. I. Peculiar supergiant HD199478 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1147095