INTRODUCTORY REMARKS

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INTRODUCTORY REMARKS

• D. C. Backer
• Astronomy Department
• Radio Astronomy Laboratory, UC Berkeley

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THE UNKNOWN
As we know, There are known knowns. There are
things we know we know. We also know There are
known unknowns. That is to say We know there
are some things We do not know. But there are
also unknown unknowns, The ones we don't know
We don't know.   Department of Defense news
briefing Feb. 12, 2002
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Sources Time Scales -- Generic

• Gravitational collapse (G rho)-0.5 e.g., star
  core 1 s
• Nuclear L/Vs e.g., NS accretion layer 1
  km/0.1 c??
• Electromagnetic L/c e.g., PSR GP 1 m/c 3
  ns
• Magnetic L/VB e.g., magnetar 1 km/?
• Electrostatic L/c e.g., lightning, EMP
• Spin/Orbit? gravity again? Kepler time
• Mechanical L/cs e.g., neutron star crust

Sites factories for exotica in globular clusters
MBH galaxy cores, and also more
prosaic environs of compact binaries
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Calculus

• Density, n Birth Rate/Volume Life Time
• Luminosity Function, dn/dL
• Flux Luminosity / 4 pi Distance2
• Detections 4/3 pi Distance3 Density(Flux)

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Pulsars
THE FIRST FOUR While pursuing her PhD at
Cambridge University, Jocelyn Bells advisor was
Antony Hewish, a radio astronomer. Hewish and his
graduate students in 1967 completed a radio
telescope specially designed to observe the
scintillation (twinkling) of stars, particularly
quasars. That summer, she observed an unusual
signal at a wavelength of 3.7m -- unusual in that
it corresponded to a sharp burst of radio energy
at a regular interval of about one second. These
were not like signals from other known sources
such as stars, galaxies, or solar wind.
While continuing with her actual Ph.D. research,
Bell identified a second piece of 'scruff' close
to Cassiopea A (itself a supernova remnant) and
managed to capture the regular pulses about 1
second apart. This significantly reduced the
possibility of distant life, and Bell went back
through the miles of chart data that she had
accumulated looking for more 'scruff'. She
identified two more lots of 'scruff' and several
other potential anomalies. These additional
discoveries confirmed to Hewish and Bell that
this was neither man-made interference, nor was
it (probably) alien life, but was some form of
emission from these stars.
"We did all the work ourselves and cheerfully
sledgehammered all one summer." Burnell and the
antenna.
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Crab Staelin Reifenstein1968 (Science)
PSR B053121 - Crab
PSR B052521
P-ALFA 1/11 found via single pulses
Parkes MB 20/800
M31/M33 tantalizing J. Cordes
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Crab Giant Pulses
Tip detectable out to Virgo cluster!
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Nature 422, 141 - 143 (13 March 2003)

• Nanosecond radio bursts from strong plasma
  turbulence in the Crab pulsar
• T. H. HANKINS, J. S. KERN, J. C. WEATHERALL
  J. A. EILEK

2 ns resolution at 5 GHz periodic frequency
structure
ns
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4C 21.53 A Millisecond Pulsar B193721

• End of 19th Century photoelectric effect small
  anomaly amidst grand edifice of Physics takeoff
  point for Einstein quantum world.
• Compact, steep-spectrum (high TB) weird source
  in Crab Nebula (Hewish Okoye c. 1960).
  Calibrator for DBs MSc project 20-km, 38-MHz
  interferometer summer 1967. Pulsar 9 months
  later.
• Hewish scintillation array discovers zone of
  avoidance for IPS objects along plane Readhead
  et al. Anomaly stood out 4C 21.53. Tony R. told
  me about this in Fall 1979 at 1d astrophysics mtg
  at Caltech. I followed up and even wrote a
  speculative paper about confusing data.
• Westerbork image at 610 MHz in 1982 confirmed
  speculations and triggered Arecibo campaign
  starting with Shri K and Mike D observations in
  Sep 1982. Seen early as interstellar
  scintillator.

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Interstellar Scattering 101
Lesson 1 basic physical optics
6.5. Critical Size, Theta_cLesson 2 source at finite distance D and screen
at xD