SwSt 1: an O-rich planetary nebula around a C-rich central star

Marco, Orsola De; Crowther, P. A.; Barlow, M. J.; Clayton, Geoffrey C.; Koter, A. de

doi:10.1046/j.1365-8711.2001.04887.x

Cited by 29 publications

(17 citation statements)

References 68 publications

(148 reference statements)

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“…Our agreement with the models by Koesterke & Hamann (1997b), but which is about half the value obtained by de Marco et al (2001) by modelling the stellar optical and UV spectra with state-of-the-art non-LTE codes for expanding atmospheres and a composite beta velocity law. and velocity, and therefore show strong variations when the star evolves (Crowther 1999).…”

Section: The Stellar Windsupporting

confidence: 84%

“…Column 5: optical extinction coefficients, taken from CMB98 (c = 1.46 × 1.21 × E(b − v)) and Tylenda et al (1992). Columns 6,7,8 and 9: respectively, the Zanstra (Gleizes et al 1989), energy-balance (Preite-Martinez et al 1989 and1991) and model atmosphere (Hamann 1996;Koesterke & Hamman 1997;Leuenhagen & Hamann 1998;de Marco et al 2001 and1998 for objects 37, 40 and41;Dudziak et al 2001 for object 25) temperatures, and the adopted value of the temperature (log T ). Columns 10 and 11: respectively, the terminal velocity obtained by modelling the spectra (Koesterke & Hamann 1997b;de Marco et al 2001 and1997 …”

Section: Column 3: [Wo]-[wc] Type From This Workmentioning

confidence: 99%

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Quantitative classification of WR nuclei of planetary nebulae

Acker

Neiner

2003

A&A

122

217

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Abstract. We analyse 42 emission-line nuclei of Planetary Nebulae (PNe), in the framework of a large spectrophotometric survey of [WC] nuclei of PNe conducted since 1994, using low/medium resolution spectra obtained at ESO and at OHP. We construct a grid of selected line-intensities (normalized to C -5806 Å = 100) ordered by decreasing ionisation potential going from 871 to 24 eV. In this grid, the stars appear to belong clearly to prominent O (hot [WO1-4] types) or C (cooler [WC4-11] types) line-sequences, in agreement with the classification of massive WR stars applied to Central Stars of Planetary Nebulae (CSPNe) by Crowther et al. 1998 (CMB98). We propose 20 selected line ratios and the FWHM of C  and C  lines as classification diagnostics, which agree well with the 7 line ratios and the FWHM proposed by CMB98. This classification based on ionisation is related to the evolution of the temperature and of the stellar wind, reflecting the mass-loss history. In particular, inside the hot [WO4]-class, we discover four stars showing very broad lines over the whole spectral range. These stars possibly mark the transition from the initial momentum-driven phase to the later energy-driven phase of the CSPNe along their evolution from the post-Asymptotic Giant Branch

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Section: The Stellar Windsupporting

confidence: 84%

Section: Column 3: [Wo]-[wc] Type From This Workmentioning

confidence: 99%

Quantitative classification of WR nuclei of planetary nebulae

Acker

Neiner

2003

A&A

122

217

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“…The abundances span a wide range. V348 Sgr and presumably HV 2671 are very carbon-rich, grouping closely with the members of the [WC] central stars of PNs (e.g., Leuenhagen, Haman, & Jeffrey 1996;De Marco et al 2001); DY Cen and MV Sgr are composed mainly of helium, more like normal RCB stars (Asplund et al 2000).…”

Section: Summary Of Hot Rcb Star Characteristicsmentioning

confidence: 75%

What Are the Hot R Coronae Borealis Stars?

Marco¹,

Clayton²,

Herwig³

et al. 2002

The Astronomical Journal

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We investigate the evolutionary status of four stars: V348 Sgr, DY Cen, and MV Sgr in the Galaxy and HV 2671 in the LMC. These stars have in common random deep declines in visual brightness, which are characteristic of R Coronae Borealis (RCB) stars. RCB stars are typically cool hydrogen-deficient supergiants. The four stars studied in this paper are hotter (T eff = 15-20 kK) than the majority of RCB stars (T eff = 5000-7000 K). Although these are commonly grouped together as the hot RCB stars they do not necessarily share a common evolutionary history. We present new observational data and an extensive collection of archival and previously published data that is reassessed to ensure internal consistency. We find temporal variations of various properties on different timescales that will eventually help us to uncover the evolutionary history of these objects. DY Cen and MV Sgr have typical RCB helium abundances, which exclude any currently known post-asymptotic giant branch (post-AGB) evolutionary models. Moreover, their carbon and nitrogen abundances present us with further problems for their interpretation. V348 Sgr and HV 2671 are in general agreement with a born-again post-AGB evolution, and their abundances are similar to Wolf-Rayet central stars of planetary nebulae (PNs). The three Galactic stars in the sample have circumstellar nebulae, which produce forbidden line radiation (for HV 2671 we have no information). V348 Sgr and DY Cen have lowdensity, low-expansion velocity nebulae (resolved in the case of V348 Sgr), while MV Sgr has a higher density, higher expansion velocity nebula. All three stars, on the other hand, have split emission lines, which indicate the presence of an equatorial bulge but not of a Keplerian disk. In addition, the historical light curves for the three Galactic hot RCB stars show evidence for a significant fading in their maximum-light brightnesses of $1 mag over the last 70 yr. From this we deduce that their effective temperatures increased by a few thousand degrees. If V348 Sgr is a born-again star, as we presume, this means that the star is returning from the bornagain AGB phase to the phase of a central star of PN. Spectroscopically, no dramatic change is observed over the last 50 years for V348 Sgr and MV Sgr. However, there is some evidence that the winds of V348 Sgr and DY Cen have increased in strength in the last decade. HV 2671, located in the LMC, has not been analyzed in detail but at 5 Å resolution is almost identical to V348 Sgr. Through the bolometric correction derived for V348 Sgr and the known distance, we can estimate the absolute V magnitude of HV 2671 (M V = À3.0 mag) and its bolometric luminosity ($6000 L ).

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“…(see e.g. Leuenhagen, Hamann & Jeffery 1996; Koesterke & Hamann 1997b; Koesterke, Dreizler & Rauch 1998; Leuenhagen & Hamann 1998; De Marco et al 2001; Herald & Bianchi 2004a; Herald, Bianchi & Hillier 2005; Marcolino et al 2007). To date, only a few Galactic CSPNe are well studied.…”

Section: Introductionmentioning

confidence: 99%

A new grid of synthetic spectra for the analysis of [WC]-type central stars of planetary nebulae

Keller

Herald

Bianchi

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present a comprehensive grid of synthetic stellar‐atmosphere spectra, suitable for the analysis of high‐resolution spectra of hydrogen‐deficient post‐asymptotic giant branch objects hotter than 50 000 K, migrating along the constant luminosity branch of the Hertzsprung–Russell diagram. The grid was calculated with cmfgen, a state‐of‐the‐art stellar atmosphere code that properly treats the stellar winds, accounting for expanding atmospheres in non‐local thermodynamic equilibrium, line blanketing, soft X‐rays and wind clumping. We include many ionic species that have been previously neglected. Our uniform set of models fills a niche in an important parameter regime, that is, high effective temperatures, high surface gravities and a range of mass‐loss values. The grid constitutes a general tool to facilitate determination of the stellar parameters and line identifications and to interpret morphological changes in the stellar spectrum as stars evolve through the central star of planetary nebula phase. We show the effect of major physical parameters on spectral lines in the far‐ultraviolet (far‐UV), UV and optical regimes. We analyse UV and far‐UV spectra of the central star of NGC 6905 using the grid to constrain its physical parameters, and proceed to further explore other parameters not taken into consideration in the grid. This application shows that the grid can be used to constrain the main photospheric and wind parameters, as a first step towards a detailed analysis. The full grid of synthetic spectra, comprising of far‐UV, UV, optical and infrared spectral regions, is available online.

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SwSt 1: an O-rich planetary nebula around a C-rich central star

Cited by 29 publications

References 68 publications

Quantitative classification of WR nuclei of planetary nebulae

Quantitative classification of WR nuclei of planetary nebulae

What Are the Hot R Coronae Borealis Stars?

A new grid of synthetic spectra for the analysis of [WC]-type central stars of planetary nebulae

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