Monday, October 14, 2013 at 4:00 PM

JILA Auditorium

Tim Brown, University of Colorado

"Dancing with the Stars:  How Do They Spin the Way They Do?"

Abstract:

All stars rotate, with periods ranging from milliseconds (for some neutron stars)  to years (for some supergiants).  Cool main-sequence stars with surface convection  zones (Sun-like stars) show less range, but still span periods from fractions of a  day to months.  Our current understanding says that young stars rotate rapidly,  but are eventually spun down by the torque from a magnetized stellar wind.   To explain the details of rotational period distributions in not-too-old star clusters,  the theory invokes other processes, notably a moderately long-lived (few hundred MY)  decoupling of the rotation of the stellar convection zone from that of the interior.   In this talk, I will first review the observational and theoretical arguments that lead  to this picture. Then I will describe a modest variant to an alternative explanation for the observations that was first suggested by Sydney Barnes. It retains the notion  of magnetized wind braking but does not require young-star convection zones to  rotate independently of their radiative interiors.  A desirable feature of this view is  that if it is shown to be correct,  we may as a result learn something fundamental  about stellar dynamos.  Last, I will discuss how one might choose between these  two pictures.  Unsurprisingly, time-domain observations are the key; LCOGT's  world-wide network of robotic telescopes is ideally suited to provide much of the  necessary data.

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