We present extensive optical spectroscopy of the early-type magnetic star HD 191612 (O6.5f?pe-O8fp). The Balmer and He I lines show strongly variable emission which is highly reproducible on a well-determined 538-d period. He II absorptions and metal lines (including many selective emission lines but excluding He II λ4686 Å emission) are essentially constant in line strength, but are variable in velocity, establishing a double-lined binary orbit with P orb = 1542 d, e = 0.45. We conduct a model-atmosphere analysis of the spectrum, and find that the system is consistent with a ∼O8 giant with a ∼B1 main-sequence secondary. Since the periodic 538-d changes are unrelated to orbital motion, rotational modulation of a magnetically constrained plasma is strongly favoured as the most likely underlying 'clock'. An upper limit on the equatorial rotation is consistent with this hypothesis, but is too weak to provide a strong constraint.

We follow, using both optical spectroscopy and photometry, the '' textbook '' colliding-wind WR+O binary WR 140 through and between the periastron passages of 1993 and 2001. An extensive collection of high-quality spectra allows us to derive precise orbital elements for both components simultaneously. We confirm the extremely high eccentricity of the system, e ¼ 0:881 AE 0:005, find an excellent match of the newly derived period to the previous estimates, P ¼ 2899:0 AE 1:3 days, and improve the accuracy of the time of periastron passage, T 0 ¼ HJD 2; 446; 147:4 AE 3:7. Around periastron, at orbital phases $ 0:995 1:015, additional emission components appear on the tops of the broad Wolf-Rayet emission lines of relatively low ionization potential. The phase-dependent behavior of these excess line emissions points to their origin in the wind-wind collision zone, which allows us to place some limits on the orbital inclination of the system, i ¼ 50 AE 15 , and half-opening angle of the bow shock cone, ¼ 40 AE 15 . The relatively sudden appearance and disappearance of the extra emission components probably signify a rapid switch from an adiabatically to a radiatively dominated regime and back again. Multiyear UBV photometry provides one more surprise: in 2001 at ¼ 0:02 0:06, the system went through a series of rapid, eclipse-like events. Assuming these events to be related to an episode of enhanced dust formation at periastron, we estimate the characteristic size of the dust grains to be a $ 0:07 lm.

Abstract. Spectroscopic observations of the peculiar variable V838 Mon during the period from the second light outburst until the fast dimming are presented. We describe high resolution (R ≈ 60 000) high S /N spectra obtained a day before the second light maximum and low resolution (R ≈ 6000) spectra covering the whole period. The temporal run of intensities and radial velocities of various lines is presented. Using Na  D IS lines we determine the reddening distance of V838 Mon d > 3.1 kpc, and kinematic distance d > 4 kpc. We estimate that V838 Mon is slightly metal deficient but otherwise has a quite solar-like chemical composition except for enhanced abundances of Li, Ba and La.

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We present the results of an optical spectroscopic study of the massive Wolf–Rayet (WR) binary HD 192641 = WR 137. These 1986–2000 data cover the dust‐formation maximum in 1997. Combining all available measurements of radial velocities, we derive, for the first time, a spectroscopic orbit with period 4766 ± 66 d (13.05 ± 0.18 yr). The resulting masses, adopting i= 67 °, are MO= 20 ± 2 M⊙ for the O component and MWR= 4.4 ± 1.5 M⊙ for the WR component. These appear, respectively, approximately normal and on the low side for the given spectral types. Analysis of the intense multisite spectroscopic monitoring in 1999 shows that the C iiiλ5696 and C ivλλ5802/12 lines have the highest intrinsic variability levels. The periodogram analysis yields a small‐amplitude modulation in the absorption troughs of the C ivλλ5802/12 and He iλ5876 lines with a period of 0.83 d, which could be related either to pulsations or large‐scale rotating structures as seen in the WN4 star EZ Canis Majoris (WR 6). Wavelet analysis of the strong emission lines of C iiiλ5696 and C ivλλ5802/12 enabled us to isolate and follow for several hours small structures (emission subpeaks) associated with density enhancements within the wind of the Wolf–Rayet star. Cross‐correlating the variability patterns seen in different lines, we find a weak but significant correlation between the variability in emission lines with different ionization potentials, i.e. in lines formed at different distances from the WR stellar core. Adopting a β wind‐velocity law, from the motion of individual subpeaks we find β∼ 5, which is significantly larger than the canonical value β≃ 1 found in O star winds.