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Cen X-3 & Clocks in the Sky

Introduction: Light Curves, Power Spectra, & Periodicities

Education Activities To Accompany Chandra Data Analysis Software
Cen X-3 & Clocks in the Sky

Interpreting the power spectrum: how fast is the pulsar moving?

Other observations show a remarkable feature. Every 2.1 days the x-rays disappear for about 12 hours. When the x-rays reappear, the pulses reach us at higher frequencies (eventually reaching a frequency of 0.2083 pulses per second); 1.05 days (half the orbit period) later, the pulses start reaching us at lower frequencies (eventually dropping to a frequency of 0.20783 pulses per second). This oscillation in the pulse frequency continues, back and forth, every 2.1 days. What we are apparently seeing is the x-ray source moving towards us (giving us a higher frequency Doppler shift) and then moving away from us, on the other side of the orbit (giving us lower frequencies). Our clock is telling us about the nature of the orbit of the x-ray source! The exact way the frequencies change tells us that the orbit is essentially a circular one, with the x-ray source moving rapidly about another object. How fast? We use the Doppler shift formula to find out:
Click Here for the Solution
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Last updated: 03/21/08


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