The central star of the planetary nebula PB 8: a Wolf-Rayet-type wind of an unusual WN/WC chemical composition

Todt, H.; Peña, M.; Hamann, Wolf-Rainer; Gräfener, G.

doi:10.1051/0004-6361/200912183

Cited by 40 publications

(75 citation statements)

References 33 publications

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“…Prinja and Massa (2013) suggested that the ratio of 23 Or from the black troughs, if present 24 Sometimes, two velocity laws with different β are combined, e.g. Todt et al 2010 narrow features observed at terminal velocities in the UV resonance lines of B-supergiants provides a clumping independent tool to estimate mass-loss rates in these objects. This may be especially important because in B-type supergiants, the Hα line might be optically thick, and thus lose its diagnostic value (Petrov et al, 2014).…”

Section: Mass-loss Diagnostics and The Effects Of Wind Clumpingmentioning

confidence: 99%

Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

et al. 2017

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Massive stars, at least ∼ 10 times more massive than the Sun, have two key properties that make them the main drivers of evolution of star clusters, galaxies, and the Universe as a whole. On the one hand, the outer layers of massive stars are so hot that they produce most of the ionizing ultraviolet radiation of galaxies; in fact, the first massive stars helped to re-ionize the Universe after its Dark Ages. Another important property of massive stars are the strong stellar winds and outflows they produce. This mass loss, and finally the explosion of a massive star as a supernova or a gamma-ray burst, provide a significant input of mechanical and radiative energy into the interstellar space. These two properties together make massive stars one of the most important cosmic engines: they trigger the star formation and enrich the interstellar medium with heavy elements, that ultimately leads to formation of Earth-like rocky planets and the development of complex life. The study of massive star winds is thus a truly multidisciplinary field and has a wide impact on different areas of astronomy.In recent years observational and theoretical evidences have been growing that these winds are not smooth and homogeneous as previously assumed, but rather populated by dense "clumps". The presence of these structures dramatically affects the mass loss rates derived from the study of stellar winds. Clump properties in isolated stars are nowadays inferred mostly through indirect methods (i.e., spectroscopic observations of line profiles in various wavelength regimes, and their analysis based on tailored, inhomogeneous wind models). The limited characterization of the clump physical properties (mass, size) obtained so far have led to large uncertainties in the mass loss rates from massive stars. Such uncertainties limit our understanding of the role of massive star winds in galactic and cosmic evolution.Supergiant high mass X-ray binaries (SgXBs) are among the brightest X-ray sources in the sky. A large number of them consist of a neutron star accreting from the wind of a massive companion and producing a powerful X-ray source. The characteristics of the stellar wind together with the complex interactions between the compact object and the donor star determine the observed X-ray output from all these systems. Consequently, the use of SgXBs for studies of massive stars is only possible when the physics of the stellar winds, the compact objects, and accretion mechanisms are combined together and confronted with observations. This detailed review summarises the current knowledge on the theory and observations of winds from massive stars, as well as on observations and accretion processes in wind-fed high mass X-ray binaries. The aim is to combine in the near future all available theoretical Unified view of of inhomogeneous stellar winds in supergiant stars and HXMB 3 diagnostics and observational measurements to achieve a unified picture of massive star winds in isolated objects and in binary systems.

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Section: Mass-loss Diagnostics and The Effects Of Wind Clumpingmentioning

confidence: 99%

Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

et al. 2017

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“…A spectral analysis based on a high resolution spectrum, Todt et al (2010) revealed that this object has a stellar temperature of about 50 kK and an unusual composition with He:H:C:N:O=55:40:1:1:1 by mass and resembles spectroscopically a massive WN/C star.…”

Section: Pbmentioning

confidence: 99%

[WN] central stars of planetary nebulae

Todt¹,

Miszalski

Toalá

et al. 2016

Proc. IAU

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Abstract. While most of the low-mass stars stay hydrogen-rich on their surface throughout their evolution, a considerable fraction of white dwarfs as well as central stars of planetary nebulae have a hydrogen-deficient surface composition. The majority of these H-deficient central stars exhibit spectra very similar to massive Wolf-Rayet stars of the carbon sequence, i.e. with broad emission lines of carbon, helium, and oxygen. In analogy to the massive Wolf-Rayet stars, they are classified as [WC] stars. Their formation, which is relatively well understood, is thought to be the result of a (very) late thermal pulse of the helium burning shell.It is therefore surprising that some H-deficient central stars which have been found recently, e.g. IC 4663 and Abell 48, exhibit spectra that resemble those of the massive Wolf-Rayet stars of the nitrogen sequence, i.e. with strong emission lines of nitrogen instead of carbon. This new type of central stars is therefore labelled [WN]. We present spectral analyses of these objects and discuss the status of further candidates as well as the evolutionary status and origin of the [WN] stars.

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“…The PoWR code has been used extensively to analyse not only massive stars with strong stellar winds (e.g. Liermann et al 2010), but also low‐mass central stars of planetary nebulae, and extreme helium stars (Hamann 2010; Todt et al 2010). The PoWR code solves the non‐LTE radiative transfer in a spherically expanding atmosphere simultaneously with the statistical equilibrium equations and accounts at the same time for energy conservation.…”

Section: Stellar Windsmentioning

confidence: 99%

Early magnetic B-type stars: X-ray emission and wind properties

Oskinova¹,

Todt²,

Ignace³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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107

144

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We present a comprehensive study of X-ray emission and wind properties of massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three stars xi1 CMa, V2052 Oph, and zeta Cas. We report the first detection of X-ray emission from V2052 Oph and zeta Cas. The observations show that the X-ray spectra of our program stars are quite soft. We compile the complete sample of early B-type stars with detected magnetic fields to date and existing X-ray measurements, in order to study whether the X-ray emission can be used as a general proxy for stellar magnetism. We find that hard and strong X-ray emission does not necessarily correlate with the presence of a magnetic field. We analyze the UV spectra of five non-supergiant B stars with magnetic fields by means of non-LTE iron-blanketed model atmospheres. The latter are calculated with the PoWR code, which treats the photosphere as well as the the wind, and also accounts for X-rays. Our models accurately fit the stellar photospheric spectra in the optical and the UV. The parameters of X-ray emission, temperature and flux are included in the model in accordance with observations. We confirm the earlier findings that the filling factors of X-ray emitting material are very high. Our analysis reveals that the magnetic early type B stars studied here have weak winds. The mass-loss rates are significantly lower than predicted by hydrodynamically consistent models. We find that, although the X-rays strongly affect the ionization structure of the wind, this effect is not sufficient in reducing the total radiative acceleration. When the X-rays are accounted for at the intensity and temperatures observed, there is still sufficient radiative acceleration to drive stronger mass-loss than we empirically infer from the UV spectral lines. (abridged)Comment: 20 pages, accepted by MNRA

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The central star of the planetary nebula PB 8: a Wolf-Rayet-type wind of an unusual WN/WC chemical composition

Cited by 40 publications

References 33 publications

Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

[WN] central stars of planetary nebulae

Early magnetic B-type stars: X-ray emission and wind properties

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