Spectrophotometry of WoIf-Rayet binary systems.

Abstract

view Abstract Citations (8) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrophotometry of WoIf-Rayet binary systems. Bappu, M. K. Vainu ; Sinvhal, S. D. Abstract Spectra obtained at the cassegrain focus of the Mt. Wilson 6o-inch telescope over two seasons of observing have been used to study the variation of emission line intensities and the profiles of a few Wolf-Rayet binary systems. The binaries chosen are HD 214419, HD 193576 and HD 193928 having periods of 1.64, 4.21 and 21.64 days, respectively. Of these three, only two have been known to be eclipsing variables. HD 214419. Hiltner (1950) has found by photoelectric methods that the intensity of Heii 4686 in the binary reaches a maximum during conjunctions and~a minimum at elongations. We have measured equivalent widths at different phases for the lines Heii 6560, Hei 5875, Heii 5411 and Niv 4058. The equivalent widths of all these lines have a pattern of behavior identical to that of Heii 4686, in that all of them show increased intensities at primary and secondary minima with a lower value of intensity at elongations. On certain nights the emission intensity is considerably above average as noted by Hiltner. On such occasions, there is corresponding increase in the intensity of the other lines showing that a change in the general overall excitation mechanism is the responsible agent for the fluctuation. There are no very conspicuous changes with phase in the profiles of X4686 as has been noted in the case of HD 193576. Nearly always at the primary minimum when the Wolf-Rayet star is behind its companion, the X4686 profile has a sharp peak at the centre with wide distended wings. At secondary mini- μm when we receive radiation primarily from the Wolf-Rayet star a well rounded profile results with a slight asymmetry on the long wavelength side. The shapes at primary minimum of the profiles of Heii 4686, Heii 6560, Heii 5411 and Niv 4058 resemble the curves that would result, were the profiles outside eclipse modified by electron scattering. There is evidence that the half-widths of Niv 4058 increase at primary minimum. Such a result may be obtained if self-reversal effects are conspicuous at primary minimum, or if the macroscopic motions in the circulatory system of gas around the two components are appreciable. The former alternative may be disregarded since the profiles do not suggest any self-reversal effects. An interesting feature is the development of intense violet edges immediately after the primary and secondary minima. All the Heii lines develop such a violet edge and this pattern is followed by the Hei lines at XX5875 and 4471. It is difficult to observe this effect in the violet wing of ~656o since the io~a-F emulsion used has a dip in sensitivity in this wave-length region. HD 193576. Well-widened spectra in the blue region for this star have been used in the determination of equivalent widths for Heii 4860, Heii 4686, Nv 4603 and Niv 4058. When plotted with phase the lines Heii 4686 and Niv 4058 have negligible eclipse effects at primary minimum. Heii 4860 and Nv 4603 have minimum intensities at primary minimum, in the latter case probably caused by its own intense violet edge coupled with the violet edge of ~46I9 of Nv. HD 193928. Large scale variations in the emission-line intensities of the violet edges of Hei 4471 and Nv 4603 are easily noticeable. At certain phases X4860 as well as Heii 4686 develop humps on the long wave-length side of the profile. In the case of HD 214419 we find that the increase in brightness at primary and secondary minima is shared by all the emission lines measured. In HD 193576, Heii 4860 and Nv 4603 do not share the behavior of Heii 4686 and Nvi 4058. It would be of great interest to obtain photoelectric light curves of this star in the light of Heii 3206 and Niv 3483. One of us (Bappu 1951) has suggested that the increase in intensity of the emission lines in HD 214419 could be explained on the basis of a common envelope model. Such a situation would demand that the abnormal behavior be shared by all the emission lines together, a phenomenon that we have found to exist in HD 214419. The validity of the common-envelope hypothesis would cease to exist in those systems that are not close binaries. Verification of this hypothesis might therefore be made by carrying out programs of emission line photometry in WolfRayet binary systems having different periods. Bappu, M. K. V. 1951, Harvard thesis. Hiltner, W. A. 1950, Ap. J. 112, 447. U. P. Government Astronomical Observatory, Banaras, India. Publication: The Astronomical Journal Pub Date: June 1955 DOI: 10.1086/107182 Bibcode: 1955AJ.....60..152B full text sources ADS | data products SIMBAD (3)