The Dynamic Radio Sky SKA Level 0

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The Dynamic Radio SkySKA Level 0

• Joseph Lazio
• James Cordes

Basic research in radio astronomy at the NRL is
supported by the Office of Naval Research.
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What Does The Transient Radio Sky Look Like?

• Classes of Objects
• GRBs (g-ray loud and g-ray quiet)
• Pulsar giant pulses
• Extrasolar planets
• IDV
• UHECRs
• ETI
• Microquasars

• Operational Modes and Design
• Blind searching vs. targeted vs. triggered
• Collecting area
• Frequency range
• Configuration
• Subarrays vs. multibeaming
• RFI mitigation
• Triggers to other wavelengths!

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Radio Transients

• Consider an incoherent synchrotron source.
• Rayleigh-Jeans approximation
• S/? 2kT/?2
• ?2W2 (1/2?k)(SD2/T)
• pulse width or transient duration W
• flux density S
• distance D
• brightness temperature T
• observing frequency ?

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TransientPhase Space
?W dimensionless pulse width, uncertainty-like
relation SD2 pseudo-luminosity ? Large ?, ?t
searches have not been done in the radio.
Unexplored phase space!
from J. Cordes
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The Dynamic Radio Sky

• GRBs
• Detect the first massive stars as they collapse
  to form black holes
• Complimentary to JWST
• Extragalactic pulsars
• Probe directly the local baryon density
• Unique to SKA (modulo FUSE and Chandra studies)
• Extrasolar planets
• Measure magnetic field and rotation of planets
• Directly applicable to habitability of
  terrestrial planets
• Complimentary to TPF

• IDV
• Probe innermost regions of AGN, near supermassive
  black holes
• Transient pulsars
• Newly discovered
• UHECRs
• Search for particles with energies above the
  G-Z-K limit
• Physics beyond the Standard Model?
• Complimentary to Fermilab and LHC
• ETI
• Transformational discovery!
• Complimentary to TPF

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Crab Pulsar Giant Pulses
Arecibo

• S 160 x Crab Nebula
• 200 kJy
• Detectable to 1.5 Mpc with Arecibo
• Detectable to 7 Mpc with SKA
• Pulses 3x stronger detectable with the SKA at
  the Virgo cluster

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Extrasolar Planets

• Emission generated by stellar-wind loading of
  planetary magnetospheres.
• May be bursty.
• Assume 15 min. integration 4 MHz bandwidth ?
  SKA sensitivity is 1 ?Jy.
• SKA does not need to rely on bursts.
• Planetary magnetic fields important for
  habitability assessments.

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New Astrophysical Sources

• Evaporating black holes (Phinney Taylor)
• Coalescing compact objects (NS-NS, NS-BH)
• Prompt GRB emission (coherent)
• Coherent sources
• LIGO sources

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GCRT J1746-2757

• Discovered serendipitously in VLA observations of
  Galactic center
• Extremely steep spectrum or rapid fading
• No X-ray counterpart

GCRT J1746-2757
1998 September
(Hyman, Lazio, Kassim 2002)
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The Dynamic Radio SkyBlind Searching Experiment

• A?T needs to be large
• A collecting area
• ? solid angle covered (instantaneous FOV)
• T time per sky position
• Field of View 1 deg2
• Cover one hemisphere in one day at sub-mJy levels
• Requires access to full field of view
  instantaneously
• Computationally demanding!
• Configuration
• Compact core (? 50 collecting area)
• RFI mitigation

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The Dynamic Radio SkyTargeted Experiments

• Field of View 1 deg2
• Allows nearby galaxies (e.g., M31, M33) to be
  observed in one or a few beams
• Requires access to full field of view
  instantaneously
• Computationally demanding!
• Collecting area 0.5SKA
• Extragalactic pulsars
• Extrasolar planets
• Frequency range 0.55 GHz
• 1 GHz for extragalactic pulsars
• 5 GHz for IDV
• ( 10 GHz for SETI)
• Configuration
• Compact core (? 50 collecting area)
• RFI mitigation

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Radio Transient Sources

• Sky Surveys
• The X-and-?-ray skies have been monitored highly
  successfully with wide FoV detectors (e.g.
  RXTE/ASM, CGRO/BATSE).
• Neutrino/gravitational wave detectors are all
  sky.
• Optical transient surveys (ROTSE, RAPTOR, LSST)
  are/will revolutionalize our knowledge of the
  optical transient sky and will drive the trend
  toward data mining of petabyte databases.
• The transient radio sky (e.g. t largely unexplored.

New objects/phenomena are likely to be discovered
as well as extreme cases in predictable classes
of objects.