GSU Graduate Student Jeremy Jones

In his last year of PhD at Georgia State University, Jeremy studies A stars with CHARA.

![](files/AlumniStaff/Jones_Picture.jpg)
GSU Graduate Student Jeremy Jones
GSU Postdoc Jeremy Jones

Jeremy told us: "With my thesis project, 'The Ages of A-Stars', I am using the CHARA Array to measure the sizes (and shapes!) of nearby A-type stars. Because A-type stars evolve so rapidly (MS lifetime ~1-4 billion years), knowing how big and bright they are allow us to estimate how old they are. One complication is that A-stars are often rapidly rotating (with equatorial rotation velocities of over 150 km/s). This rapid rotation makes the stars bulge at the equator and leads to an effect called gravity darkening where the equator of the star is darker than the poles. This complication means we cannot use simple single-diameter disk models to analyze our interferometric data, so I have developed a model that accounts for rotation and simultaneously fits to interferometric and photometric data. We have verified this model on A-stars in the Ursa Major moving group (Jones et al. 2015) and are turning our attention to kappa Andromedae, a rapid rotator with a low-mass brown dwarf companion that has been directly imaged (Jones et al. in prep). Beyond this, we have observations for dozens more A-stars awaiting modeling."

![](files/AlumniStaff/Jones_Science_Picture.png)
The constellation Ursa Major with model images of four A-star members of the Ursa Major moving group.