View
17
Download
0
Category
Tags:
Preview:
DESCRIPTION
Acoustic Oscillations in Red Giants. Jim Fuller Caltech/KITP. Quiz: In which decade was the first Pulsating Red Giant Discovered?. Answer: 1596 Mira’s variability discovered by David Fabricious. Luminosity variations from Acoustic Oscillations. Chaplin & Miglio 2013. - PowerPoint PPT Presentation
Citation preview
QUIZ: IN WHICH DECADE WAS THE FIRST PULSATING RED GIANT
DISCOVERED?
Answer: 1596Mira’s variability discovered by David Fabricious
WHAT ARE ACOUSTIC OSCILLATIONS?
• Sound waves in star
• Waves are excited by convective motions
• Sound waves reflect, create global-scale standing waves, i.e., oscillation modes, at characteristic frequencies
CHARACTERISTIC FREQUENCIES
• Stellar dynamical frequency• Freefall frequency, orbital frequency at stellar surface
OSCILLATION FREQUENCIES
• Stars tend to oscillate at frequencies
• Oscillation spectrum exhibits peaks separated by
EVOLUTION UP GIANT BRANCH
• As stars evolve up RGB or AGB, their radii increase dramatically
• Mode frequencies and frequency spacing decrease
• Longer observation baselines needed
• Continuous data not needed
• Mode amplitudes increase
• Less sensitivity needed to detect oscillations
Recommended