ATLAS vs. NextGen model atmospheres: a combined analysis of synthetic spectral energy distributions

Details ATLAS vs. NextGen model atmospheres: a combined analysis of synthetic spectral energy distributions ATLAS vs. NextGen model atmospheres: a combined analysis of synthetic spectral energy distributions

2004-06-08

arxiv.org/abs/astro-ph/0406215v1

Astronomy and Astrophysics

Astrophysics

18 pages, 14 figures; accepted for publication in the Astronomical Journal (scheduled for the August issue); see also http:/

Scientific paper

10.1086/422486

We carried out a critical appraisal of the two theoretical models, Kurucz' ATLAS9 and PHOENIX/NextGen, for stellar atmosphere synthesis. Our tests relied on the theoretical fit of SEDs for a sample of 334 target stars along the whole spectral-type sequence. The best-fitting physical parameters of stars allowed a calibration of the temperature and bolometric scale. The main conclusions of our analysis are: i) the fitting accuracy of both theoretical libraries drastically degrades at low Teff; ii) comparing with empirical calibrations, both ATLAS and NextGen fits tend to predict slightly warmer Teff, but ATLAS provides in general a sensibly better fit; iii) there is a striking tendency of NextGen to label target stars with an effective temperature and surface gravity in excess with respect to ATLAS. This is a consequence of some ``degeneracy'' in the solution space, partly induced by the different input physics and geometry constraints. A different T(\tau) vertical structure of stellar atmosphere seems also required for NextGen synthetic SEDs in order to better account for limb-darkening effects in cool stars, as supported by the recent observations of the EROS BLG2000-5 microlensing event.

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