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Blasts From The Past: Historic Supernovas
Images
  Flash from Chandra.

Analyzing X-Ray Pulses from Stellar Cores - Answer Key:

GK Per

Power Spectrum (period confirmed with "period fold")
Frequency = 0.00285hz
Period = 351s

If white dwarf:

g = (6.67 x 10-11Nm2/kg2) (2.0x1030kg)/(6.4x106m)2 = 3.2x106m/s2

ac = (4π2) (6.4x106m)/(351s)2 = 2.1x103m/s2

ac is less than g – GK Per could sustain this period if it were a white dwarf.

CEN X-3

Power Spectrum (period confirmed with "period fold")
Frequency = 0.208hz
Period = 4.8s

If white dwarf:

g is the same as above for GK Per = 3.2x106m/s2

ac = (4π2) (6.4x106m)/(4.8s)2 = 1.7x107m/s2

ac is greater than g – Cen X-3 could not sustain this period if it were a white dwarf.

If neutron star:

g = (6.67 x 10-11Nm2/kg2) (4.0x1030kg)/(10000m)2 = 2.7x1012m/s2

ac = (4π2) (10000m)/(4.8s)2 = 1.7x104m/s2

ac is less than g – Cen X-3 could sustain this period if it were a neutron star.