AAS 199th meeting, Washington, DC, January 2002
Session 92. Circumstellar Material and Atmospheres: Cooler
Display, Wednesday, January 9, 2002, 9:20am-6:30pm, Exhibit Hall

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[92.10] The Effect of TiO Absorption on the Angular Diameters of Cool Stars

T. E. Nordgren (University of Redlands), H. M. Dyck (NPOI)

In this paper we compare the optical and infrared angular diameters of 32 cool stars (spectral type K2 - M6) with measured TiO absorption. We show that for the coolest stars in the sample there is a correlation between the ratio of optical to infrared diameter and TiO absorption strength. As the molecular absorption strength increases the optical angular diameter becomes progressivley larger than the infrared angular diameter. We argue that this validates recent proposals in the literature that suggest TiO absoprtion affects optical diameters significantly and that therefore infrared angular diameters, while possibly of a lower precision, yield a more accurate effective temperature scale for these stars.


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