Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 0711.3186

Beyond 1D: spectral line formation with 3D hydrodynamical model atmospheres of red giants

R. Collet·M. Asplund·R. Trampedach
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present the results of realistic, 3D, hydrodynamical, simulations of surface convection in red giant stars with varying effective temperatures and metallicities. We use the convection simulations as time-dependent, hydrodynamical, model atmospheres to compute spectral line profiles for a number of ions and molecules under the assumption of local thermodynamic equilibrium (LTE). We compare the results with the predictions of line formation calculations based on 1D, hydrostatic, model stellar atmospheres in order to estimate the impact of 3D models on the derivation of elemental abundances. We find large negative 3D-1D LTE abundance corrections (typically -0.5 to -1 dex) for weak low-excitation lines from molecules and neutral species in the very low metallicity cases. Finally, we discuss the extent of departures from LTE in the case of neutral iron spectral line formation.

Explore related subjects

astro-ph

Keep this discovery

BibTeXRIS

R. Collet, M. Asplund, R. Trampedach. 2007-11-20. Beyond 1D: spectral line formation with 3D hydrodynamical model atmospheres of red giants. https://arxiv.org/abs/0711.3186

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2016

The Interpretation of Inertial Force and The Existence of Absolute Background

The formalism of classical particle dynamics is reinvestigated according to the basic requirement of causal consistency, and a new equation of particle dynamics, which is more general and more in line with classical mechanics experiments than Newton's second law, is obtained. More importantly, the inertial frame of reference is no longer required and the inertial force is no longer introduced by hand. The new dynamical equation can be straightforwardly applied in any reference frame as long as which is irrotational with respect to the absolute background of the universe. The nature of the inertial force is nothing but the real forces acting on the reference object. The essence of this reform of classical particle dynamics is just a drawback of traditional formalism in Newtonian mechanics being corrected. However, it may be more important that a logical derivation of this new particle dynamics equation strongly suggests the existence of an absolute background for the whole space of the universe. In physical concepts, the absolute background for space does not conflict with the relative length of the base unit of space in Einstein's Special Relativity and General Relativity. Furthermore, the size of the base unit of space should essentially be understood as the length of the line segment, which is cut from the absolute background of space by the intrinsic physical events.

astro-ph↗
arXiv2015

The exact numerical treatment of inflationary models

The precision reached by the recent CMB measurements gives new insights into the shape of the primordial power spectra of the cosmological perturbations. In the context of inflationary cosmology, this implies that the CMB data are now sensitive to the form of the inflaton potential. Most of the current approaches devoted to the derivation of the inflationary primordial power spectra, or to the inflaton potential reconstruction problem, rely on approximate analytical treatments that may break down for exotic models. In this article, we numerically solve the inflationary evolution of both the background and all the perturbed quantities to extract the primordial power spectra exactly. Such a method solely relies on General Relativity and linear perturbation theory. More than providing a tool to test analytical approximations, one may consider, without complications, the treatment of non-standard inflationary models as those involving several fields, eventually non-minimally coupled to gravity. The usefulness of the exact numerical approach to deal with CMB data is illustrated by analysing the WMAP third year data in the context of single field models. For this purpose, we introduce a new inflationary related parameter encoding the basic properties of the reheating era. This reheating parameter has significant observable effects and provides a self-consistency test of inflationary models. As a working example, the marginalised probability distributions of the reheating and potential parameters associated with the small field models are presented.

astro-ph↗
arXiv2015

Mass estimates from stellar proper motions: The mass of $ω$ Centauri

A projected mass estimator and a maximum likelihood estimator are developed to best determine the mass of stellar clusters from proper motion data. Both methods effectively account and correct for errors in the velocities, and provide an unbiased and robust estimate of the cluster mass. Using an extensive proper motion study of $ω$ Centauri by van Leeuwen et al. (2000), we estimate the mass of $ω$ Centauri using these two different methods to be $2.8 \times 10^{6} M_{\odot} \left[d/5.1 kpc\right]^{3}$. Within this modeling context, the statistical error is $3\%$ and the systematic error is $4\%$.

astro-ph↗