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

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

a_c 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

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

a_c 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

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

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