The Spectra of Wolf-Rayet Stars at High Dispersion

Bappu, M. K. V.

doi:10.1007/978-94-010-2511-9_5

Cited by 19 publications

(5 citation statements)

References 14 publications

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“…For the stars observed at air masses greater than 1.5 we expect that the errors in v and (b -v) may each be as great as 0™2. Line identifications were made by reference to the Smith and Kuhi (1981) Atlas for WN stars, and the Bappu (1973) study for WC stars, with additional aid from Moore (1959). We classified the stars using the criteria listed by van der Hucht et al (1981), which were derived from Smith's (1968a) classification of Galactic and LMC WR stars.…”

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confidence: 99%

Spectroscopy of six Wolf-Rayet stars - The latest and faintest

Massey¹,

Conti²

1983

PASP

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We present absolute spectrophotometry and classification of six relatively faint galactic Wolf-Ray et (WR) stars for which previous photometry was poor. One of these objects, the heavily reddened infrared source CRL 2179, is the faintest known galactic WR star, with a visual magnitude ~ 22. Its spectral type is WC10, later than that of any other known Population I WC star. Another faint star, WR 122, has a strong NII emission-line spectrum which is unprecedented: we define its type as WN10. The other four stars have typical WR spectra.

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Spectroscopy of six Wolf-Rayet stars - The latest and faintest

Massey¹,

Conti²

1983

PASP

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“…Figure 2 shows a plot of the mean radial velocities of the violet-displaced absorption edges in the spectrum of HD 151932 versus lower excitation potential of the ions involved. Bappu (1973) first noted that the velocities of violet-displaced absorption components have different values for different ions. Our diagram, in addition, shows that radial velocity and excitation potential are strongly correlated in the sense that increasing km/s Fig.…”

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confidence: 99%

Violet-displaced absorption lines in the spectrum of the Wolf-Rayet star HD 151932

Seggewiß¹

1974

PASP

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Violet-displaced absorption components of Hei -Hen, N m -N v, and Civ have been found in the spectrum of the WN7 star HD 151932. The corresponding radial velocities increase with decreasing excitation potential of the originating ions, indicating a radially expanding atmosphere with accelerating velocity field. The velocity curves of the ions with lowest excitation potentials, He i and N in A4097, display a periodicity of about 3.5 days which leads to the concept of an oscillating outer envelope.

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“…Three conferences have been devoted to the Wolf-Rayet stars with the purpose of determining what the spectra of Wolf-Rayet stars mean in terms of conditions in the stellar atmosphere and to listing the basic properties of Wolf-Rayet stars (Gebbie and Thomas 1968; Bappu and Sahade 1973;de Loore and Willis 1982). An interesting insight on how astrophysicists work unfolds as one reads the invited presentations and fiery discussion (fully reported) which crossed and recrossed the conference room in 1968, the more formal presentations which took place in 1971 to provide firm information about many of the topics brought up in 1968, and the rather fully developed picture generated in 1981 by the invited presentations.…”

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“…Information about basic properties such as the masses of the Wolf-Rayet stars, their distribution in space in our Galaxy and in other galaxies, their effective temperatures as determined from observed quantities, and their absolute visual magnitudes can be found in Divan and Prévot-Burnichon (1986); see also Conti (1986). Less complete information can be found in some of the invited presentations reported in Bappu and Sahade (1973) and in de Loore and Willis (1982).…”

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“…In most Wolf-Rayet stars the emission lines are intrinsically wide; most features are blends of several lines. Atlases of Wolf-Rayet spectra at high resolution have been published by Johnson (1978) in the ultraviolet; by Underhill (1958Underhill ( , 1967 and Bappu (1973) in the visible range; and by Hillier, Jones, and Hyland (1983) and Aitken, Roche, and Allen (1984) in the infrared. Many low-resolution spectral scans of the ultraviolet spectral range of Wolf-Rayet stars can be found in Nussbaumer et al (1982), while low-resolution spectral scans of a few faint Wolf-Rayet stars from 1200 Â to about 7000 Â can be found in Garmany, Massey, and Conti (1984).…”

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The riddle of the Wolf-Rayet stars

Underhill

1986

PASP

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The history of Wolf-Ray et stars since their discovery is noted and a brief review is given of the major studies of these rare emission-line stars. One goal of the present paper is to determine what the spectra of Wolf-Rayet stars imply concerning the physical state of the atmospheres of WolfRayet stars. A second goal is to determine what the relationship is, if any, between a particular Wolf-Rayet subtype and the evolutionary state of a massive star. Because some massive Population I stars and some low-mass evolved stars show Wolf-Ray et-type spectra, the cause of the phenomenon is not associated with only one stage of evolution.The characteristic features of Wolf-Rayet spectra are reviewed and the typical masses, radii, effective temperatures, and rates of mass loss of Population I Wolf-Rayet stars are noted. The use of modeling as a tool for determining the physical state of a Wolf-Rayet atmosphere is reviewed and evaluations are given of the analyses which have been published of Wolf-Rayet spectra. It is noted that it is essential to identify a model atmosphere with the atmosphere of a star by predicting spectral features which agree with several details in the observed spectrum. This is because possessing a particular type of emission-line spectrum is the characteristic which defines a WolfRayet star.It is concluded that Wolf-Rayet stars appear to have effective temperatures in the range from 25,000 K to 30,000 K, normal (solar) composition, a density of the order of 10 10 cm 3 in the emission-line forming regions, and an electron temperature in the range from 50,000 K to 10 5 K in the case of WC stars, but greater than 10 5 K in WN stars. The mantles of Wolf-Rayet stars are very extensive, at least 10 14 cm in radius. This picture is self-consistent; it is yet to be proved that it is unique.A brief discussion is given of possible causes of the physical state of the mantle of a Wolf-Rayet star. It is pointed out that the electrodynamic coupling of mechanical motion in a disk supported by magnetic lines of force to the plasma of the stellar mantle is a promising source for the nonradiative energy and momentum which must be deposited in the mantle of the star in order to generate a Wolf-Rayet-type spectrum. At present any postulated correlation between Wolf-Rayet subtype and stage of evolution is entirely speculative and what exists in the literature is not supported by sound spectrum analysis.

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The Spectra of Wolf-Rayet Stars at High Dispersion

Cited by 19 publications

References 14 publications

Spectroscopy of six Wolf-Rayet stars - The latest and faintest

Spectroscopy of six Wolf-Rayet stars - The latest and faintest

Violet-displaced absorption lines in the spectrum of the Wolf-Rayet star HD 151932

The riddle of the Wolf-Rayet stars

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