lect 15 - Exam 2 Based on Lectures notes, problems worked...

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Exam 2 • Based on Lectures notes, problems worked on class, and quizzes (Chapters/sections 17.6-22.??) • To be held at Testing Center (basement of Science and Tech 1 building , see attached map). • You may take the exam anytime during the days 3/29 – 4/3 • You need to bring a Picture ID, pen/pencil (calculators are not allowed, but you can use the Windows calculator). • Exam will be administered via Blackboard system. • Approximately 50 questions. • There will be a quiz on the material covered until Thursday and that is due at 3:00 pm on 3/30. • On 3/30,I will review (including quiz 7). • There is class on Thursday April 1 st . Please check hours of operation at http://ttc.gmu.edu/hours.html Depends on what it is covered on Thursday
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Lecture room at Enterprise Hall Testing Center (basement of Science and Tech 1 Building) Johnson Center
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Pulsars gradually slow down as they radiate energy into space • The pulse rate of many pulsars is slowing down steadily • This reflects the gradual slowing of the neutron star’s rotation as it radiates energy into space • Old Pulsars: slowed down to a period of a second or more • In Summary: An isolated pulsar slows down as it ages, so it’s pulse period increases but some pulsars can speed up!
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Sudden speedups of the pulse rate are called glitches
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Superfluidity and superconductivity are among the strange properties of neutron stars A neutron star consists of a superfluid, superconducting core surrounded by a superfluid mantle and a thin, brittle crust Glitches may be caused by interactions between the neutron star’s crust and its superfluid interior or material falling onto the crust. There is evidence for an “atmosphere”
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Evidence for an atmosphere
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Evidence for an atmosphere => absorption of X-rays photons
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The fastest pulsars were probably created by mass transfer in close binary systems They are called millisecond pulsars (period between 1- 10ms) (or 100-1000 rotations per second) If a neutron star is in a close binary system with an ordinary star, tidal forces will draw gas from the ordinary star onto the neutron star How do we know is a close binary system? Short orbital periods, 10-100 days (remember Kepler’s third law) The transfer of material onto the neutron star can make it rotate extremely rapidly, giving rise to a millisecond pulsar
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formed by a high-mass and a Low-mass star: - The high-mass star will become a Type II supernovae; neutron star. Then the pulsar will slow down radiating energy. - The low-mass star (slowly evolving) becomes later a red giant and starts to spill gas over to the neutron star, increasing its rotational speed. But, not all millisecond pulsars are members of close binaries…
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This note was uploaded on 02/06/2011 for the course ASTR 113 taught by Professor Geller during the Spring '08 term at George Mason.

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lect 15 - Exam 2 Based on Lectures notes, problems worked...

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