BEGIN:VCALENDAR VERSION:2.0 PRODID:-//AIP Calendar//www.aip.de// BEGIN:VEVENT SUMMARY:Colloquium: Jeff Valentini (STScl) DTSTART:20210204T133000Z DTEND:20210204T143000Z DTSTAMP:20260930T145936Z UID:www.aip.de-584 CATEGORIES:Scientific CATEGORIES:Generic Event CATEGORIES:Public CONTACT:Sydney Barnes DESCRIPTION:Inaccurate Abundances for Cool Stars\nFor many topics in astro physics\, stellar parameters with limited accuracy are sufficient. Some as trophysical problems require better accuracy than is typically achieved to day\, for example characterizing exoplanet host stars. Decades of research have addressed several issues that limited accuracy in the past\, e.g.\, radiastive transfer algorithms\, line data for atoms and molecules\, conti nuous opacities\, and non-LTE rate coefficients. A key limitation that sti ll limits accuracy is the treatment of kinematics in cool stellar photosph eres. Cool stellar photospheres have velocity fields that are not modeled adequately in 1D and 2D models. 1D models use various approximations that ultimately limit accuracy achievable today. Very common approximations inc lude microturblence and empirical line data\, despite availability of more accurate line data. These approximations are unnecessary when the model i ncludes velocity gradients in the photosphere. 3D hydrodynamic models calc ulate photospheric velocity fields\, but are computationally expensive. I will show a novel approach for modeling photospheric velocity gradients in a 1D model. Solar lines can be reproduced without the need for microturbu lence or empirical line data. This demonstrates that a key limitation of c urrent 1D models is treatment of velocity fields. One other limitation tha t needs attention is software development methodology.\n LOCATION:Colloquium zoom room END:VEVENT END:VCALENDAR