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arXiv · 0807.2782

NICMOS Spectrophotometry and Models for A-Stars

R. C. Bohlin·Martin Cohen
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Abstract

Absolute flux distributions for eight stars are well measured from 0.8-2.5mu m with NICMOS grism spectrophotometry at a resolution of R~100 and an accuracy of 1-2%. These SEDs are fit with Castelli & Kurucz model atmospheres; and the results are compared with the Cohen-Walker-Witteborn (CWW) template models for the same stars. In some cases, the T_{eff}, log g, and log z parameters of the best fitting model differ by up to 1000 K from the earlier CWW model. However, differences in the continua of the modeled IR flux distributions from 0.4-40mu m are always less than the quoted CWW uncertainty of 5% because of compensating changes in the measured extinction. At wavelengths longward of the 2.5mu m NICMOS limit, uncertainties still approach 5%, because A-star models are not yet perfect. All of these A stars lie in the JWST continuous viewing zone and will be important absolute flux standards for the 0.8-30mu m JWST wavelength range.

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R. C. Bohlin, Martin Cohen. 2008-07-17. NICMOS Spectrophotometry and Models for A-Stars. https://doi.org/10.1088/0004-6256%2F136%2F3%2F1171

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