Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981pasp...93..119e&link_type=abstract
Astronomical Society of the Pacific, Publications, vol. 93, Feb.-Mar. 1981, p. 119-125.
Astronomy and Astrophysics
Astronomy
30
Emission Spectra, Main Sequence Stars, O Stars, Stellar Spectra, Variable Stars, H Lines, Radial Velocity, Spectral Line Width, Stellar Mass Ejection, Stellar Rotation
Scientific paper
An episode of double emission lines of hydrogen and helium in the spectrum of the rapidly rotating O9.5 V(e) star Zeta Ophiuchi is reported. Observations were made in H-alpha, H-beta and several He I and He II lines with the Reticon detector on the coude spectrograph of the 2.1-m telescope at McDonald Observatory during March and May, 1980, and with the Washburn Observatory echelle spectrograph and 0.91-m telescope on August 22. The strongest lines, H-alpha and He I 5876 and 6678 A, appeared as broad but shallow absorptions with emission peaks in both the red and blue wings, while the weaker He I 4713 and He II 4541 lines also showed definite emission. The symmetry, radial velocities, equivalent widths and emission peaks of the spectral lines are found to be similar to those observed during the previous outburst of Zeta Ophiuchi in 1974. Application of the model of an optically and geometrically thin ring of gas moving with circular orbits in the equatorial plane proposed by Huang (1972) indicates the presence of material extending from the stellar surface to a distance of 4.8 stellar radii, and an inclination of the rotation axis of 57 deg, which implies an equatorial rotation velocity of 480 km/sec, about 72 percent of the critical velocity for stellar breakup.
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