Probing Atlas model atmospheres at high spectral resolution
Stellar synthesis and reference template validation
INAOE - Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro 1, 72840 Tonantzintla, Puebla, Mexico e-mail: [ebertone;mchavez;lino]@inaoep.mx
2 INAF - Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy e-mail: firstname.lastname@example.org
Accepted: 21 April 2008
Aims. The fast improvement of spectroscopic observations makes mandatory a strong effort on the theoretical side to better reproduce the spectral energy distribution (SED) of stars at high spectral resolution. In this regard, relying on the Kurucz Atlas/Synthe original codes we computed the Bluered library, consisting of 832 synthetic SED of stars, that cover a large parameter space at very high spectral resolution () along the 3500-7000 Å wavelength range.
Methods. Bluered synthetic spectra have been used to assess in finer detail the intrinsic reliability and the performance limits of the Atlas theoretical framework. The continuum-normalized spectra of the Sun, Arcturus, and Vega, plus a selected list of 45 bright stars with high-quality SEDs from the Prugniel & Soubiran Elodie catalog, form our sample designed to probe the global properties of synthetic spectra across the entire range of H-R parameters.
Results. Atlas models display a better fitting performance with increasing stellar temperature. High-resolution spectra of Vega, the Sun, and Arcturus have been reproduced at , respectively, within a 0.7%, 4.5%, and 8.8% relative scatter in residual flux. In all the three cases, the residual flux distribution shows a significant asymmetry (skewness parameter , respectively), which neatly confirms an overall “excess” of theoretical line blanketing. For the Sun, this apparent discrepancy is alleviated, but not recovered, by a systematic decrease (-40%) of the line oscillator strengths, , especially referring to iron transitions. Definitely, a straight “astrophysical” determination of for each individual atomic transition has to be devised to overcome the problem. By neglecting overblanketing effects in theoretical models when fitting high-resolution continuum-normalized spectra of real stars, we lead to a systematically warmer effective temperature (between +80 and +300 K for the solar fit) and a slightly poorer metal content.
Key words: Sun: atmosphere / stars: atmospheres / stars: individual: Arcturus / stars: individual: Vega / stars: fundamental parameters / line: profiles
© ESO, 2008