CCAPP Seminar: "Core and Surface Rotation Rates of Evolved Intermediate Mass Stars" Jamie Tayar (OSU)

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June 6, 2017
11:30AM - 12:30PM
Location
McPherson 4054

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Add to Calendar 2017-06-06 11:30:00 2017-06-06 12:30:00 CCAPP Seminar: "Core and Surface Rotation Rates of Evolved Intermediate Mass Stars" Jamie Tayar (OSU) Intermediate mass stars (M ~ 2.0 - 3.0 Msun) provide important tests of the role of rotation in the structure and evolution of stars because they live in an important transitional regime. Like massive stars, they rotate rapidly on the main sequence and have convective cores. However, they evolve to become secondary red clump stars, where their structure and internal rotation can be measured with the tools of red giant asteroseismology developed for lower mass stars. Compared to prior studies, we have focused our efforts on measuring surface rotation rates and studying trends in representative samples. The slow surface rotation rates of these stars provides conclusive evidence for some combination of strong post-MS angular momentum loss and differential rotation with depth in convective envelopes. We compare the measured core and surface rotation rates, find that the contrast is smaller than in first ascent red giants, and discuss evidence for core-envelope recoupling during the core helium burning phase. Finally, we discuss trends in both core and surface rotation with mass, metallicity, and surface gravity and their implications for internal angular momentum transport and loss models. McPherson 4054 Center for Cosmology and AstroParticle Physics (CCAPP) ccapp@osu.edu America/New_York public
Description

Intermediate mass stars (M ~ 2.0 - 3.0 Msun) provide important tests of the role of rotation in the structure and evolution of stars because they live in an important transitional regime. Like massive stars, they rotate rapidly on the main sequence and have convective cores. However, they evolve to become secondary red clump stars, where their structure and internal rotation can be measured with the tools of red giant asteroseismology developed for lower mass stars. Compared to prior studies, we have focused our efforts on measuring surface rotation rates and studying trends in representative samples. The slow surface rotation rates of these stars provides conclusive evidence for some combination of strong post-MS angular momentum loss and differential rotation with depth in convective envelopes. We compare the measured core and surface rotation rates, find that the contrast is smaller than in first ascent red giants, and discuss evidence for core-envelope recoupling during the core helium burning phase. Finally, we discuss trends in both core and surface rotation with mass, metallicity, and surface gravity and their implications for internal angular momentum transport and loss models.

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