Free Access
Volume 559, November 2013
Article Number A16
Number of page(s) 28
Section Stellar atmospheres
Published online 29 October 2013

Online material

Table 1

High-resolution Mercator-Hermes (H) and ESO-Feros (F) échelle spectroscopic observations of MWC 314.

thumbnail Fig. 1

Narrow-band Hα image of the extended bipolar nebula of MWC 314 (adapted from Marston & McCollum 2008). The image is 12.5′ vertically. The inset shows the Mercator-MEROPE intensity contour image with faint Hα nebulosity surrounding the central star. North is up, and east to the left.

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thumbnail Fig. 2

Comparison of the (intensity contour) narrow-band Hα emission image (left-hand panel) and the continuum image (right-hand panel) of MWC 314 observed in March 2011 with Mercator-MEROPE. Line emission is absent in the continuum image where extended east-west filament structures are observed in the Hα emission image (see Sect. 3). Both panels are 6.9′ by 10′. North is up, and east to the left.

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thumbnail Fig. 3

Comparison of 100′′  × 100′′  Hα (left-hand panel) and continuum (right-hand panel) intensity contour images of MWC 314. The outer intensity contour signals an extended Hα envelope that is almost circular symmetric within 20′′  of the central star.

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thumbnail Fig. 4

Best fit orbital solution to 16 radial velocity measurements in MWC 314. The RV observation dates during 22 m are given in Table 1. The solid horizontal line is drawn at the γ-velocity for the best fit orbital solution.

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thumbnail Fig. 9

Top panels: dynamic spectra of three absorption lines of MWC 314 in the heliocentric velocity scale. Blue colours correspond to normalised stellar continuum flux levels. Bottom panels: corresponding normalised line profiles shifted upwards with orbital phase (spectrum numbers are labelled in the left-hand panel). The (S-shaped) Doppler shifts of the lines is due to the orbital motion of the primary star. We observe significant enhancements in the absorption line depth at orbital phases with large Doppler blue-shift of φ = 0.65–0.85.

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thumbnail Fig. 10

Three Si iii absorption lines observed in MWC 314 (black solid lines) are overplotted with theoretical line profiles computed in non-LTE with Multi. The line transfer calculations use atmosphere models of Teff = 17 kK (dashed drawn lines), 18 kK (solid drawn lines), and 19 kK (dash-dotted lines). Boldly drawn lines are computed with log g = 2.5, and thin drawn lines for log g = 3.0. Atmosphere models with Teff > 19 kK yield Si iii line equivalent widths incompatible with observed values. The detailed profile fits require Vrotsini ≃ 50 km   s-1.

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thumbnail Fig. 14

Normalised Hα, Hβ, Hδ, and H Pa 14 lines are plotted with φ (clockwise). The line FWHM decreases towards the higher H Balmer series lines. The Hα line wings extend beyond ±300 km   s-1. The higher Balmer series lines also show stronger absorption in the violet line wing to ~300 km   s-1. The Hδ and Pa14 lines (bottom panels) show enhanced blue-shifted absorption around φ = 0.65–0.85, similar to the He i lines.

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thumbnail Fig. 15

Hα (bottom panel) and Hβ (top panel) emission lines of MWC 314 show largest normalised flux maxima at φ ≃ 0.65 (spectrum Nos. 6 and 16), and smallest flux maxima at φ ≃ 0.32 (Nos. 13, 15, and 7). The absolute emission line fluxes determined with the V-brightness curve are however almost invariable, indicating that the extended circumbinary Hα and Hβ emission line formation regions are little influenced by the orbital motion.

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thumbnail Fig. 16

Top panel: continuum normalised flux maxima observed with φ in strong Hα (open symbols) and Hβ (dots) emission lines of MWC 314. The Hα maxima are divided by 24, and Hβ maxima by 6.75 for comparison. Bottom panel: blue/red emission peak ratio we observe in two permitted Fe ii emission lines formed in the circumbinary disc. The B/R variations of ±10% are due to orbital modulation of Doppler shifting line opacity, whereas the Hα and Hβ flux changes result from variability of the stellar continuum flux with φ.

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thumbnail Fig. 18

Detailed profiles of permitted Fe ii lines (middle and right-hand panels) strongly depend on φ. The prominent emission lines form in a circumbinary disc and stay static (within ±3 km   s-1) around the γ-velocity. The B/R emission peak ratios (see bottom panel of Fig. 14) periodically vary due to Doppler shifting lines formed in the orbiting primary star. It causes the triple-peaked emission lines around φ = 0.4–0.5. We observe in Si ii λ6347 static line emission from the disc modulated by Doppler shifting absorption in the primary (left-hand panels).

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thumbnail Fig. 19

Normalised fluxes plotted with φ (shifted upwards) of two forbidden [N ii] (left-hand panels) and two [Fe ii] (right-hand panels) emission lines in MWC 314. The FWHM ≃ 50  km   s-1 of the double-peaked [Fe ii] emission lines is comparable to the permitted Fe ii emission lines (see Fig. 16), indicating a common line formation region in a circumbinary disc. The [N ii] lines show smaller FWHM ≃ 25  km   s-1.

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thumbnail Fig. 20

Comparison of the Spitzer spectrum of MWC 314 (bottom spectrum) and the theoretical model spectrum (top spectrum). The vertical lines mark the wavelength positions of H i and He ii lines used in the spectrum calculations. The prominent emission lines computed at 22.38 μm and 27.8 μm are due to H i and He i lines (see text).

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thumbnail Fig. 23

Top panels: dynamic spectra with orbital phase φ of He i λ5876 computed with the 3D asymmetric wind model we develop for MWC 314 in this paper. Bottom panels: corresponding normalised flux spectra for 12 φ-values. Left-hand panels are computed for f = 10 and ς0 = ϑ0 = π/4 in the density structure of Eq. (6). For comparison the middle panels are computed for f = 10, ς0 = ϑ0 = π/3, with the radial velocity amplitude of orbital motion set to 4× the observed value. Right-hand panel is computed for f = 3.3, ς0 = ϑ0 = π/4, and the observed Vr-curve. The latter values provide the best fit to the P Cyg absorption line profile changes we observe with φ shown in Fig. 12 (see Sect. 5.3).

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© ESO, 2013

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