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Events at Physics

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Events on Thursday, November 18th, 2010

Astronomy Colloquium
The Diverse Fates of Single and Binary Massive Stars
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Nathan Smith, University of Arizona
Abstract: Core-collapse supernovae (SNe) are bright, and therefore have the
potential to reveal details about the outcome of stellar evolution at large distances and different environments. However, our ability to theoretically predict which initial masses (and metallicities) produce which specific types of SNe they produce (e.g., Types Ib, Ic, II-P,II-L, IIn, IIb) is in rather miserable shape. This has critical implications for understanding the origin of long-duration GRBs, for example, which have been linked to Type Ic SNe. Observational input about the diverse end fates of massive stars helps this situation on two main fronts: 1. A growing number of direct detections of progenitor stars at the locations of SNe in archival pre-explosion data, mostly from HST, provides important links between the type of SN and the star's initial mass. 2. We now have reasonably good estimates about the relative fractions of different SN subtypes from the first decade of the Lick Observatory SN Search, allowing us to quantify what fraction of massive stars explode as which types of SN. Combining these two constraints, I will discuss the implications for the range of initial stellar masses that correspond to each type of SN. A key result (long suspected but now quantified) is that simple predictions of single-star stellar evolution models cannot be reconciled with the observed SN fractions, and that close binary evolution must be a primary agent responsible for SNe that have lost their H envelopes. Even accounting for this binary evolution (which has its own pitfalls), the remaining single-star progenitors contradict single-star evoution models, with some surprising implications. Time permitting, I will discuss some of the strange things that can occur in massive evolved binary systems -- especially one of them.
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Astrophysics with Gravitational-Wave Detectors
Time: 4:00 pm
Place: 4274 Chamberlin Hall
Speaker: Vuk Mandic, University of Minnesota
Abstract: Gravitational waves are predicted by general theory of relativity to be produced by accelerating mass systems with quadrupole moment. The amplitude of gravitational waves is expected to be very small, so the best chance of their direct detection lies with some of the most energetic events in the universe, such as mergers of two neutron stars or black holes, Supernova explosions, or the Big-Bang itself. I will review the status of current gravitational-wave detectors, such as the Laser Interferometer Gravitational-wave Observatory (LIGO), as well as some of the most recent results obtained using LIGO data. I will also discuss plans and expectations for the future generations of gravitational-wave detectors.
Host: Peter Timbie
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Graduate Introductory Seminar
Medical Physics
Time: 5:30 pm
Place: 2223 Chamberlin Hall
Speaker: Birn, Christian, Nickles
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