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Pulsars ASTR2110 Sarazin. Crab Nebula. July 4, 1054, Chinese “guest star”. What is energy source?. Pulsars. Cambridge radio array, excellent time resolution, broad sky coverage November 28, 1967: Jocelyn Bell (-Burnell) PSR 1919+21. Pulsars. Pulsars.
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Crab Nebula July 4, 1054, Chinese “guest star” What is energy source?
Pulsars Cambridge radio array, excellent time resolution, broad sky coverage November 28, 1967: Jocelyn Bell (-Burnell) PSR 1919+21
Pulsars Terrestrial, etc.? No, no parallax Little Green Men? No. pulses individually irregular no modulation broad-band no planetary motion
Pulsars Terrestrial, etc.? No. no parallax Little Green Men? No. pulses individually irregular no modulation broad-band no planetary motion
Pulsars Terrestrial, etc.? No. no parallax Little Green Men? No. pulses individually irregular no modulation broad-band no planetary motion
Pulsars: Properties mid 1968 Periods: P = 0.2 – 2 seconds | d P / dt | < 10-13 sec/sec, very good clock dP/dt > 0, pulses slowing very slightly Pulse duration >~ 20 ms
Size limit D D ≤ c dt ≲ 103 km M ≳ M → WD, NS, or BH
Origin of Clock? • Orbital Period? • a ~ 108 cm • as loses energy, binary gets smaller, period gets shorter • Pulsation Period? • P ∝ 1/2, → ~ 109 gm/cm3, between WD and NS? • Why would pulsation period change with time? • Rotation Period? • vrot < vesc→ cannot be WD • Prot (NS) > 1 msec = 0.001 sec → OK • Rotating BHs are symmetric → no reason for pulses • As rotating object loses energy, slows down, Prot increases
Crab Pulsar 1968 P = 0.033 sec dP/dt = 4 x 10-13 tslow ~ P/(dP/dt) ~ 2000 years ~ time since supernova Decrease in rotational kinetic energy = energy from Crab Nebula
How Does Pulsar Power Crab Nebula?Pulsar Wind Nebulae red = optical blue = X-ray
Pulsar Wind Nebulae Crab Chandra Xray