Atmospheric NLTE-models for the spectroscopic analysis of blue stars with winds. II. Line-blanketed models
By J. Puls, M. Urbaneja, R. Venero, T. Repolust, U. Springmann, A. Jokuthy, M. R. Mokiem. 2004
186 citations recorded by the source corpus.
Received; accepted Abstract. We present new or improved methods for calculating NLTE, line-blanketed model atmospheres for hot stars with winds (spectral types A to O), with particular emphasis on a fast performance. These methods have been implemented into a previous, more simple version of the model atmosphere code Fastwind (Santolaya-Rey et al. 1997) and allow to spectroscop- ically analyze rather large samples of massive stars in a rea sonable time-scale, using state-of-the-art physics. Alth ough this updated version of the code has already been used in a number of recent investigations, the corresponding methods have not been explained in detail so far, and no rigorous comparison with results from alternative codes has been performed. This paper intends to address both topics. In particular, we describe our (partly approximate) approach to solve the equations of statistical equilibrium for tho se elements which are primarily responsible for line-blocking and blanketing, as well as an approximate treatment of the line-blocking itself, which is based on a simple statistical approach usin g suitable means for line opacities and emissivities. Both methods are validated by specific tests. Furthermore, we comment on our i mplementation of a consistent temperature structure. In the second part, we concentrate on a detailed comparison with results from those two codes which have been used in alternative spectroscopical investigations, namely cmfgen (Hillier & Miller 1998) andwm-Basic (Pauldrach et al. 2001). All three codes predict almost identical temperature structur es and fluxes for λ > 400 A, whereas at lower wavelengths a number of discrepancies are found. Particularly in the Heii continua, where fluxes and corresponding numbers of ionizin g photons react extremely sensitively to subtle differences in the models, we consider any uncritical use of these quantities (e.g., in the context of nebula diagnostics) as being dangerous. Optical H/He lines as synthesized byfastwind are compared with results from cmfgen, obtaining a remarkable coincidence, except for the Hei singlets in the temperature range between 36,000 to 41,000 K for dwarfs and between 31,000 to 35,000 K for supergiants, wherecmfgen predicts much weaker lines. Consequences due to these discrepancies are discussed. Finally, suggestions are presented how to adequately parameterize model-grids for hot stars with winds, with only one additional parameter compared to standard grids from plane-parallel, hydrostatic models.
Subfields: Astronomy and Astrophysics, Instrumentation
View Paper: https://www.semanticscholar.org/paper/f3ffaa9679d1a6b73ebb3d701be44114ece55ba0
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Citations in the corpus
- A possible black hole in the γ-ray microquasar LS 5039 (2005, methodology): “Despite this, we have selected two extreme profiles showing minimum and maximum EW for the calculation, which we have performed by using again the latest version of FASTWIND (Puls et al. 2005; see examples of use in Repolust et al. 2004).”
- Mass loss from hot massive stars (2008, background): “Justa couple of years later two more codes, PoWR (Gräfener et al 2002) and FASTWIND (Santol ya-Rey et al 1997, Puls et al 2005) became available.”
- Modelling the nebular emission from primeval to present-day star-forming galaxies (2016, background): “…Ekström et al. 2012; Georgy et al. 2013; Chen et al. 2015) and atmospheres (e.g., Hauschildt & Baron 1999; Hillier & Miller 1999; Pauldrach et al. 2001; Lanz & Hubeny 2003, 2007; Hamann & Gräfener 2004; Martins et al. 2005; Puls et al. 2005; Rodŕıguez-Merino et al. 2005; Leitherer et al. 2010).”
- Fourier method of determining the rotational velocities in OB stars (2007, methodology): “For this formal test we used Fastwind (Santolaya-Rey et al. 1997; Puls et al. 2005) theoretical profiles from a model with Teff = 30 000 K, log g= 4.0 (an early B dwarf) and convolved with different broadening profiles.”
- The VLT-FLAMES survey of massive stars: surface chemical compositions of B-type stars in the Magellanic Clouds (2006, methodology): “Additionally atmospheric parameters of several of our Magellanic Cloud objects have been independently estimated by Mokiem et al. (2006a, 2006b) using the non-LTE code fastwind (Puls et al. 2005).”