The 'SEI' method for accurate and efficient calculations of line profiles in spherically symmetric stellar winds

Lamers, H. J. G. L. M.; Cerruti-Sola, M.; Perinotto, M.

doi:10.1086/165100

Cited by 184 publications

(182 citation statements)

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“…We modelled the N v, C iv, Si iv and Si iii (λ1207) wind lines (and in a few cases also Al iii and C ii) using the "Sobolev with exact integration" (SEI) method described by Lamers et al (1987). In addition, we adopted the modified treatment of the wind optical depth law introduced by Massa et al (1995b), such that the radial optical depth τ rad (w) is treated in 10 independent velocity bins (each 0.1 v ∞ wide).…”

Section: Profile Fitting With the Sei Codementioning

confidence: 99%

Wind variability of B supergiants

Prinja

Massa²,

Fullerton

2002

A&A

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Abstract. We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analysed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include "normal" stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasises the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters, but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures. The diversity of wind patterns evident likely reflects the role of stellar rotation and viewing angle in determining the observational characteristics of azimuthally extended structure rooted at the stellar surface. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (Ṁ qi) is a factor of ∼1.5, when integrated between 0.2 and 0.9 v∞; it can however be several times larger over localised velocity regions. At a given effective temperature the mean relative ion ratios can differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in terms of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

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Section: Profile Fitting With the Sei Codementioning

confidence: 99%

Wind variability of B supergiants

Prinja

Massa²,

Fullerton

2002

A&A

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“…To constrain the properties of the wind, we fit a simple model to the N v doublet using the line-fitting routines of D. Massa, which combine the Sobolev with exact integration (SEI) algorithm described by Lamers et al (1987) with the wind optical depth law introduced by Massa, Prinja & Fullerton (1995). This approach uses the standard "beta law" parameterization of the velocity, which has the form…”

Section: Mass Lossmentioning

confidence: 99%

FUSE, STIS and Keck spectroscopic analysis of the UV-bright star vZ 1128 in M3 (NGC 5272)

Chayer

Dixon

Fullerton

et al. 2015

Mon. Not. R. Astron. Soc.

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We present a spectral analysis of the UV-bright star vZ 1128 in M3 based on observations with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Space Telescope Imaging Spectrograph (STIS), and the Keck HIRES echelle spectrograph. By fitting the H i, He i, and He ii lines in the Keck spectrum with non-LTE H-He models, we obtain T eff = 36,600 K, log g = 3.95, and log N (He)/N (H) = −0.84. The star's FUSE and STIS spectra show photospheric absorption from C, N, O, Al, Si, P, S, Fe, and Ni. No stellar features from elements beyond the iron peak are observed. Both components of the N v λ1240 doublet exhibit P Cygni profiles, indicating a weak stellar wind, but no other wind features are seen. The star's photospheric abundances appear to have changed little since it left the red giant branch (RGB). Its C, N, O, Al, Si, Fe, and Ni abundances are consistent with published values for the red-giant stars in M3, and the relative abundances of C, N, and O follow the trends seen on the cluster RGB. In particular, its low C abundance suggests that the star left the asymptotic giant branch before the onset of third dredge-up.

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“…Improved values for the terminal velocities of the winds were derived from line fits for the Fe ii lines. We used the SEI method for the calculation of the line profiles (Lamers et al 1987) which takes this The results are summarized in Tab. 1.…”

Section: Uv Observations Of the Disk Windmentioning

confidence: 99%

Disk Winds of B[e] Supergiants

Zickgraf

1999

International Astronomical Union Colloquium

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Abstract. The class of B [e] supegiants is characterized by a two-component stellar wind consisting of a normal hot star wind in the polar zone and a slow and dense disk-like wind in the equatorial region. The properties of the disk wind are discussed using satellite UV spectra of stars seen edge-on, i.e. through the equatorial disk. These observations show that the disk winds are extremely slow, v∞ 50 − 90 km s −1 , i.e. a factor of ∼ 10 slower than expected from the spectral types. Optical emission lines provide a further means to study the disk wind. This is discussed for line profiles of forbidden lines formed in the disk.

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The 'SEI' method for accurate and efficient calculations of line profiles in spherically symmetric stellar winds

Cited by 184 publications

References 0 publications

Wind variability of B supergiants

Wind variability of B supergiants

FUSE, STIS and Keck spectroscopic analysis of the UV-bright star vZ 1128 in M3 (NGC 5272)

Disk Winds of B[e] Supergiants

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