The Luminous Eclipsing SMC OB + WN Binary HD 5980 before and during the Recent LBV‐like Outburst: An Extreme Case of Colliding Winds

Moffat, A. F. J.; Марченко, С. В.; Bartzakos, P.; Niemelä, Virpi Sinikka; Cerruti, M. A.; Magalhães, A. M.; Balona, L. A.; St-Louis, N.; Seggewiß, W.; Lamontagne, R.

doi:10.1086/305475

Cited by 52 publications

(56 citation statements)

References 41 publications

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“…However, it is well known that the wind collision zone can be a strong source of emission lines (e.g. HD 5980, Moffat et al 1998), which would resolve this problem. Their inferred minimum column density is also larger than the observed X-ray value, again implying an overestimate ofṀ 1 .…”

Section: Discussionmentioning

confidence: 99%

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

Pittard

Corcoran

2002

A&A

228

386

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Abstract. We present X-ray spectral fits to a recently obtained Chandra grating spectrum of η Carinae, one of the most massive and powerful stars in the Galaxy and which is strongly suspected to be a colliding wind binary system. Hydrodynamic models of colliding winds are used to generate synthetic X-ray spectra for a range of mass-loss rates and wind velocities. They are then fitted against newly acquired Chandra grating data. We find that due to the low velocity of the primary wind (≈500 km s −1 ), most of the observed X-ray emission appears to arise from the shocked wind of the companion star. We use the duration of the lightcurve minimum to fix the wind momentum ratio at η = 0.2. We are then able to obtain a good fit to the data by varying the mass-loss rate of the companion and the terminal velocity of its wind. We find thatṀ 2 ≈ 10 −5 M yr −1 and v∞ 2 ≈ 3000 km s −1 . With observationally determined values of ≈500-700 km s −1 for the velocity of the primary wind, our fit implies a primary mass-loss rate ofṀ 1 ≈ 2.5 × 10 −4 M yr −1 . This value is smaller than commonly inferred, although we note that a lower mass-loss rate can reduce some of the problems noted by Hillier et al. (2001) when a value as high as 10 −3 M yr −1 is used. The wind parameters of the companion are indicative of a massive star which may or may not be evolved. The line strengths appear to show slightly sub-solar abundances, although this needs further confirmation. Based on the over-estimation of the X-ray line strengths in our model, and re-interpretation of the HST/FOS results, it appears that the Homunculus nebula was produced by the primary star.

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Section: Discussionmentioning

confidence: 99%

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

Pittard

Corcoran

2002

A&A

228

386

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“…Indeed, the He ii λ4686 line in HD 5980 is highly phasedependent as a result of strong excess emission arising from its wind-wind collision zone (Moffat et al 1998).…”

Section: He II λ4686 In Wn Starsmentioning

confidence: 99%

Reduced Wolf-Rayet line luminosities at low metallicity

Crowther¹,

Hadfield²

2006

A&A

140

222

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New NTT/EMMI spectrophotometry of single WN2-5 stars in the Small and Large Magellanic Clouds are presented, from whichHe ii λ4686 line luminosities have been derived, and compared with observations of other Magellanic Cloud Wolf-Rayet stars. SMC WN3-4 stars possess line luminosities which are a factor of 4 times lower than LMC counterparts, incorporating several binary SMC WN3-4 stars from the literature. Similar results are found for WN5-6 stars, despite reduced statistics, incorporating observations of single LMC WN5-9 stars from the literature. C iv λ5808 line luminosities of carbon sequence WR stars in the SMC and IC 1613 (both WO subtypes) from the recent literature are a factor of 3 lower than LMC WC stars from Mt Stromlo/DBS spectrophotometry, although similar results are also obtained for the sole LMC WO star. We demonstrate how reduced line luminosities at low metallicity follow naturally if WR winds are metallicity-dependent, as recent empirical and theoretical results suggest. We apply mass loss-metallicity scalings to atmospheric non-LTE models of Milky Way and LMC WR stars to predict the wind signatures of WR stars in the metal-poor star forming WR galaxy I Zw 18. WN He ii λ4686 line luminosities are 7-20 times lower than in metal-rich counterparts of identical bolometric luminosity, whilst WC C iv λ5808 line luminosities are 3-6 times lower. Significant He + Lyman continuum fluxes are predicted for metal-poor early-type WR stars. Consequently, our results suggest a larger population of WR stars in I Zw 18 than is presently assumed, particularly for WN stars, potentially posing a severe challenge to evolutionary models at very low metallicity. Finally, reduced wind strengths from WR stars at low metallicities impacts upon the immediate circumstellar environment of long duration GRB afterglows, particularly since the host galaxies of high-redshift GRBs tend to be metal-poor.

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“…The characteristics of HD 5980 and its 1994 eruption are described in Barbá et al (1996), Drissen et al (2001), Moffat et al (1998), Koenigsberger et al (1998Koenigsberger et al ( , 2000, Koenigsberger (2004) and Georgiev et al (2011). Here we will only highlight the aspects that are relevant to the present investigation.…”

Section: Input Parameters For the 1994 Eventmentioning

confidence: 94%

Observations of the early stages in the formation of an LBV shell

González

Koenigsberger

2014

A&A

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Luminous blue variables are massive stars that undergo a series of eruptive events through which they shed their outer layers before becoming Wolf-Rayet stars. During the eruptive events, their winds are denser and expand slower than in the non-eruptive state. In this paper we apply a model for the interaction of the post-eruption fast wind with the slower moving shell of dense material that was ejected during the 1994 eruption of HD 5980, a massive system located in the Small Magellanic Cloud. The model predicts a velocity for the working surface that is consistent with the velocity of insterstellar-like absorption features observed in HST/STIS spectra of 1999 and 2000, leading to the conclusion that we have witnessed for the first time the earliest stages of a circumstellar shell being formed around an LBV.

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The Luminous Eclipsing SMC OB + WN Binary HD 5980 before and during the Recent LBV‐like Outburst: An Extreme Case of Colliding Winds

Cited by 52 publications

References 41 publications

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

Reduced Wolf-Rayet line luminosities at low metallicity

Observations of the early stages in the formation of an LBV shell

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