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.429S The Astrophysical Journal Supplement Series, 32:429-465, 1976 November .32. © 1976. The American Astronomical Society. All rights reserved. Printed in U.S.A. 6ApJS. 197 COPERNICUS ULTRAVIOLET OBSERVATIONS OF MASS-LOSS EFFECTS IN O AND B STARS Theodore P. Snow, Jr., and Donald C. Morton Princeton University Observatory Received 1976 February 4 ABSTRACT Copernicus far-ultraviolet spectral scans at 0.2 and 0.4 Â resolution have been used to search for P Cygni hues in 47 stars to determine the distribution of high-velocity mass loss in the H-R diagram and to identify the stellar characteristics associated with the phenomenon. For all 40 stars with displaced absorption lines, the tables list the velocities of the short-wavelength edge, the line center, and the peak of the emission if present. Portions of the spectra of 42 stars are reproduced including an extensive sequence showing the profiles of C m À1176 and N v À1240. Evidence for mass motions in ground-based spectra of the survey stars also are listed. With a few exceptions, it was found that stars brighter than Mb?i = — 6.0 are losing mass, and fainter ones are not, within the present detection limits. Edge velocities up to 5 times the surface escape velocity were found, but no strong correlations with luminosity or efiective temperature were seen. Some stars had a wide range of ionization states at all velocities, and some had narrow absorption components super- posed on broader features. O vi absorption fines with shifts or asymmetries are present in several O and hot B stars, suggesting the existence of coronae with electron temperatures 7^ ä 105 K. Tables are provided summarizing the best available data on the wavelengths and oscillator strengths of most lines likely to show mass-loss effects in either visual or UV spectra. Subject headings: stars: early-type — stars: mass loss — ultraviolet: spectra I. BACKGROUND our survey probably would have been inappropriate anyway. A P Cygni profile in a stellar spectrum, in the The explanation of the P Cygni profile was under- simplest form of the definition, consists of an emission stood as early as 1929 when McCrea (1929) discussed line near its laboratory wavelength in the star’s frame this type of fine produced in the expanding shells of and an accompanying absorption fine on the short- novae and Beals (1929) described the mass outflow wavelength side with a definite radial velocity away implied by such fines in Wolf-Rayet stars as well as in from the star. According to the usual convention, such P Cyg and t? Car. Underhill (1960) has presented a a velocity is negative when referred to the star, whose useful diagram of an expanding stellar shell with velocity normally is derived from the ordinary sym- sufficient extension that it is optically thin to the metrical absorption fines in the visible spectrum. continuum radiation from the photosphere. The Frequently the emission has a small positive velocity absorption component of the profile is produced by and sometimes the absorption shift is relatively small, that part of the expanding region which the observer so that an emission wing can appear on the short- sees projected against the photosphere, while the wavelength edge. emission originates from the entire shell except the The term P Cygni line has been adopted from the part occulted by the opaque photosphere. prototype B1 peculiar star P Cygni which has at least The strongest P Cygni fines with the largest shifts 137 such profiles in its visual and near-ultraviolet usually appear in the resonance fines, presumably spectrum, with absorption velocities between — 11 and because the required velocity occurs mainly in lower — 298 kms_1, as described by Struve and Roach density shells where neither the photon flux nor the (1939) and Beals (1951). This star has varied irregularly particle density is high enough to populate the excited in brightness between visual maxima of about mag 3 levels, except possibly the fine-structure levels of the in 1600 and 3.5 in 1655 and minima fainter than 6. ground term. Since only the lowest ion states such as Currently the brightness is relatively constant at Na I, Ca ii, and Fe i have resonance lines at visual mv = 4.8. Regrettably, this star had to be omitted wavelengths, the conspicuous P Cygni features in the from the present survey because the large interstellar hotter stars are found in the UY spectral region short- extinction (EB-V = 0.67) prevented the recording of ward of 3000 Â, where the higher ion states of most of an adequate UY signal in a single scan with the the abundant elements have their absorptions from the Copernicus spectrometer. However, Hutchings (19766) ground term. In some stars there are enough collisions has described part of the far-UV spectrum obtained in the lower layers of the expanding shell to populate by adding 11 successive scans. Since this "star seems the excited levels of H i, He i, He n, etc. and produce more like a nova than an ordinary B star, inclusion in visual absorption fines, but their shifts normally are 429 © American Astronomical Society • Provided by the NASA Astrophysics Data System .429S 430 SNOW AND MORTON Vol. 32 .32. of the order of —102 km s-1. Consequently it was the According to Batten (1967), there are eight spectro- UV spectra obtained with rockets (Morton 1967; scopic binaries in Table 1, namely HD 199579, 2 6ApJS. Carruthers 1968; and Stecher 1968) that revealed the 29 CMa, r CMa, t Ori, 8 Ori A, 0 Ori A, a Vir, and large displacements of —1000 to — 3000 km s_1 in the a Pav. In each case we have assumed that the UV 197 resonance lines of C rv, N v, and Si rv and demonstrated spectrum and the ejection of mass are due to the that the material actually was escaping from the star. brighter visual component, which is the basis of the Since the UV spectrum is so important for the under- spectral classification. Where the orbital velocities are standing of mass ejection from hot stars, a survey of sufficiently large, it would be very useful to investigate their spectra was one of the early observing programs whether the P Cygni absorptions follow the primary in for the Copernicus satellite spectrometer (Rogerson, velocity or are stationary, as McCluskey and Kondo Spitzer, et al. 1973). This paper describes these spectra, (1976) found for 29 CMa. The latter situation gives a which mainly were obtained by continuous scans at lower limit on the radius of the observed material and 0.2 Á resolution while the higher resolution detectors hence a lower limit on the rate of mass loss once the were recording selected interstellar profiles. Initially, total column density has been determined. priority was given to the brighter stars without exces- In most cases the absolute magnitudes Mv were taken sive interstellar extinction, but later stars were added from Conti and Alschuler (1971) or Conti and to help fill out the distribution of temperature and Burnichon (1974) for the O stars, and from Lesh luminosity types. Altogether there are 47 stars in our (1968, 1972) for the B stars. Values in italics indicate fist. Although the information in a few cases is limited the direct determinations from clusters, or the to a scan between approximately 1150 and 1250 Â, the measured parallaxes used by Code et al. (1975). Since majority of stars have data between 1000 Â and 1450Â, the Lesh scale averages 0.7 mag brighter than that of with a few extensions to 940 Â if the interstellar extinc- Conti at 09.5 V, we adopted a distance of 179 pc for tion is not excessive. Some data at longer wavelengths t Sco and 172 for 8 Sco from the cluster parallaxes of at 0.4 Â resolution also are available for the brighter Bertiau (1958), and we assumed that £ Oph is at the stars. similar distance of 175 pc. In the case of 6 Car, we took Mv = —3.3 from the H-R diagram of Eggen a) Classification of P Cygni Profiles (1965). We used a distance of 450 pc for £ Pup, which is close to the value derived by Graham (1965) and Beals (1951) has described eight difierent types of Brandt et al. (1971) from HjS photometry of the B profiles in P Cygni spectra, ranging from the most 2 stars surrounding y Vel. For the remaining O stars common form (type T) described at the beginning of not in clusters, spectroscopic absolute magnitudes this section to unshifted absorption or emission lines. were obtained from the calibrations of Conti and In the present paper we shall use the term P Cygni Alschuler (1971) and Walbom (1972), using their profile specifically for this type I, and explicitly respective spectral types, with averages taken when describe the other forms such as an absorption with a both classifications were available. The magnitudes relatively small shift so that the emission appears on of £ Ori A, 8 Sco, and a Vir were corrected for the both sides (type III). Particular cases of type III would companions detected with the intensity interferom- be the Balmer emission lines in an Oe star (as recently eter by Hanbury Brown, Davis, and Allen (1974û). defined by Conti and Leep 1974) or a Be star. We also Hutchings (1976a), using Hy equivalent widths to shall refer to a shortward-displaced absorption with no determine M , agreed with our values within ±0.5 mag emission component (type VIII) and an additional v except for HD 112244, which he estimated to be ninth type consisting of an asymmetric absorption line 1.0 mag brighter.

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