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SAC Seminar - Tim Brown: Dancing with the Stars: How Do They Spin the Way They Do?

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Torsdag 13. november 2014,  kl. 14:15 - 15:00



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 (of mine) to an alternative explanation for the observations that was first suggested by Sydney Barnes.  This variant 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.