An analysis of HST UV spectra of Cyg OB2 stars

Herrero, A.; Puls, J.; Corral, L. J.; Kudritzki, Rolf‐Peter; Villamariz, M. R.

doi:10.1051/0004-6361:20000236

Cited by 66 publications

(142 citation statements)

References 17 publications

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“…Furthermore, the centroid of the observed absorption trough is 8.9 over the Ha laboratory wave-A length ; this suggests that the line proÐle is signiÐcantly distorted as it is Ðlled up with Ha emission arising in the wind. Finally, the overall shape of the Ha proÐle is very similar to that of other O If stars (e.g., Cygnus OB 7 and HD 210839, Herrero et al 2000).…”

Section: W R 147supporting

confidence: 62%

“…7 and HD 210839 ; see Fig. 6 in Herrero, Puls, & Villamariz 2000), including both the central narrow absorption and the broad emission wings.…”

Section: W R 146mentioning

confidence: 99%

“…These yield estimated values of g \ 0.10 and g \ 0.028 for WR 146 and WR 147, respectively. From the spectral types, we estimate that the O components in WR 146 and WR 147 have massloss rates yr~1 (see Herrero et al 2000). M 0 O D 1 10~5 M _ If we assume a typical terminal velocity km s~1 v = B 2000 for the O stars (see Prinja, Barlow, & Howarth 1990), we can estimate the mass-loss rate of the WR components and check for consistency.…”

Section: On the Binary Status And The W Ind Collisionmentioning

confidence: 99%

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Spatially Resolved STIS Spectra of WR + OB Binaries with Colliding Winds

Lépine

Wallace

Shara

et al. 2001

The Astronomical Journal

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We present spatially resolved spectra of the visual WR ] OB massive binaries WR 86, WR 146, and WR 147, obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space T elescope. The systems are classiÐed as follows : WR 86 \ WC 7 ] B0 III, WR 146 \ WC 6 ] O8 IÈIIf, WR 147 \ WN 8 ] O5È7 IÈII(f ). Both WR 146 and WR 147 are known to have strong nonthermal radio emission arising in a wind-wind collision shock zone between the WR and OB components. We Ðnd that the spectra of their O companions show Ha proÐles in emission, indicative of large mass-loss rates and consistent with the colliding-wind model. Our spectra indicate that the B component in WR 86 has a low mass-loss rate, which possibly explains the fact that WR 86, despite being a long-period WR ] OB binary, was not found to be a strong nonthermal radio emitter. Because of the small massloss rate of the B-star component in WR 86, the wind collision region must be closer to the B star and smaller in e †ective area, hence generating smaller amounts of nonthermal radio emission. Absolute magnitudes for all the stars are estimated based on the spectral types of the components (based on the tables by Schmidt-Kaler for OB stars and van der Hucht for WR stars) and compared with actual, observed magnitude di †erences. While the derived luminosities for the WC 7 and B0 III stars in WR 86 are consistent with the observed magnitude di †erence, we Ðnd a discrepancy of at least 1.5 mag between the observed luminosities of the components in each of WR 146 and WR 147 and the absolute magnitudes expected from their spectral types. In both cases, it looks as though either the WR components are about 2 mag too bright for their spectral types or that the O components are about 2 mag too faint. We discuss possible explanations for this apparent discrepancy.

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Section: W R 147supporting

confidence: 62%

“…7 and HD 210839 ; see Fig. 6 in Herrero, Puls, & Villamariz 2000), including both the central narrow absorption and the broad emission wings.…”

Section: W R 146mentioning

confidence: 99%

Section: On the Binary Status And The W Ind Collisionmentioning

confidence: 99%

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Spatially Resolved STIS Spectra of WR + OB Binaries with Colliding Winds

Lépine

Wallace

Shara

et al. 2001

The Astronomical Journal

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“…Generally, for the line profiles studied here, the influence of rotation is important for the recombination lines, but not for the resonance lines. We use observed uv fuse spectra from Fullerton et al (2006), and optical spectra from Markova et al (2005) and A. Herrero (described in Herrero et al 2000). In addition to H α , He ii 4686, and PV, we also consider the wind sensitive cores of H β and H γ .…”

Section: A Multi-diagnostic Study Of λ Cepmentioning

confidence: 99%

Mass loss from inhomogeneous hot star winds

Sundqvist¹,

Puls²,

Feldmeier³

et al. 2011

A&A

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117

168

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Context. Mass loss is essential for massive star evolution, thus also for the variety of astrophysical applications relying on its predictions. However, mass-loss rates currently in use for hot, massive stars have recently been seriously questioned, mainly because of the effects of wind clumping. Aims. We investigate the impact of clumping on diagnostic ultraviolet resonance and optical recombination lines often used to derive empirical mass-loss rates of hot stars. Optically thick clumps, a non-void interclump medium, and a non-monotonic velocity field are all accounted for in a single model. The line formation is first theoretically studied, after which an exemplary multi-diagnostic study of an O-supergiant is performed. Methods. We used 2D and 3D stochastic and radiation-hydrodynamic wind models, constructed by assembling 1D snapshots in radially independent slices. To compute synthetic spectra, we developed and used detailed radiative transfer codes for both recombination lines (solving the "formal integral") and resonance lines (using a Monte-Carlo approach). In addition, we propose an analytic method to model these lines in clumpy winds, which does not rely on optically thin clumping. Results. The importance of the "vorosity" effect for line formation in clumpy winds is emphasized. Resonance lines are generally more affected by optically thick clumping than recombination lines. Synthetic spectra calculated directly from current radiationhydrodynamic wind models of the line-driven instability are unable to in parallel reproduce strategic optical and ultraviolet lines for the Galactic O-supergiant λ Cep. Using our stochastic wind models, we obtain consistent fits essentially by increasing the clumping in the inner wind. A mass-loss rate is derived that is approximately two times lower than what is predicted by the line-driven wind theory, but much higher than the corresponding rate derived when assuming optically thin clumps. Our analytic formulation for line formation is used to demonstrate the potential importance of optically thick clumping in diagnostic lines in so-called weak-winded stars and to confirm recent results that resonance doublets may be used as tracers of wind structure and optically thick clumping. Conclusions. We confirm earlier results that a re-investigation of the structures in the inner wind predicted by line-driven instability simulations is needed. Our derived mass-loss rate for λ Cep suggests that only moderate reductions of current mass-loss predictions for OB-stars are necessary, but this nevertheless prompts investigations on feedback effects from optically thick clumping on the steady-state, NLTE wind models used for quantitative spectroscopy.

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“…a - Najarro, Hanson, & Puls (2011), b -Bouret et al (2012), c -Borissova et al (2012. V sinI for Cyg OB2 #11 are taken from Herrero et al (2001). blended into wide bands at low spectral resolution.…”

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confidence: 99%

Investigation of Cyg OB2 #11(O5 Ifc) by Modelling its Atmosphere

Maryeva¹,

Zhuchkov

Malogolovets³

2014

Publ. Astron. Soc. Aust.

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We continue the study of O-supergiants belonging to the association Cyg OB2 using moderate-resolution spectra. In this paper we present results of the modelling of the stellar atmosphere of Cyg OB2 #11. This object belongs to the spectral class Ofc, which was recently introduced and is yet small in numbers. Ofc class consists of stars with normal spectra with CIII λλ4647, 4650, 4652 emission lines of comparable intensity to those of the Of-defining lines NIII λλ4634, 4640, 4642. We combined new spectral data obtained by the 1.5-m Russian-Turkish telescope with spectra from MAST and CASU archives and determined physical parameters of the wind and chemical composition of the stellar atmosphere using cmfgen code. The estimated nitrogen abundance is lower than one in atmospheres of 'normal' O-supergiants (i.e. O4-6 supergiants without additional spectral index 'n' or 'c') and carbon abundance is solar. Also we find an excess in silicon. We present an illustrative comparison of our modelling results with current Geneva evolutionary models for rotating massive stars. The position on the Hertzsprung-Russell diagram corresponds to the star mass of about 50 M and age about 4.5 Myr. Moreover, we carried out the high angular resolution (∼0.02arcsec) observations on the Russian 6-m telescope aiming to find weaker companions of this star, which did not reveal any.

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An analysis of HST UV spectra of Cyg OB2 stars

Cited by 66 publications

References 17 publications

Spatially Resolved STIS Spectra of WR + OB Binaries with Colliding Winds

Spatially Resolved STIS Spectra of WR + OB Binaries with Colliding Winds

Mass loss from inhomogeneous hot star winds

Investigation of Cyg OB2 #11(O5 Ifc) by Modelling its Atmosphere

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