Real Time Transient Detection with RAPTOR: Exploring the Path Toward a

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Real Time Transient Detectionwith RAPTOR
Exploring the Path Toward a Thinking Telescope

• Tom Vestrand
• on behalf of the RAPTOR Team
• Los Alamos National Laboratory
• First Zwicky Workshop---Pasadena, 17 January 2004

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Scientific Motivation Searching for Optical
Transients in Real Time

• The optical sky, even for relatively bright
  transient objects, is largely unmonitored.
• There are spectacular Explosive Optical
  Transients that have been found because of High
  Energy Satellite real-time alerts.
• But fast Optical Transients may exist that cannot
  be found by high-energy satellite monitoring,
  either because they are precursors of or are
  unrelated to high-energy transients.

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• Mining in real time is the ability to recognize,
  gather, and analyze observations as a transient
  event is in progress---thereby enabling more
  detailed follow-up observations while the event
  is on-going.

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Why is the Problem Hard?

• Need a Fast Pipeline that makes photometric
  measurements of more than 100,000 sources and
  identifies transients in less than 30 seconds.
  (10 times faster than the fastest real-time
  pipeline.)
• Must move the more sensitive narrow-field
  telescopes into the transient in seconds for
  spectroscopy and light curve measurement. (mounts
  must move 10 times faster than typical
  astronomical mounts)
• Must correctly identify, in real time, the
  celestial transient in the forest of
  non-celestial transients. ( more than 1000 false
  positives for every real event)

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False Positives

• Hot Pixels
• Satellites
• Airplanes
• Cosmic Rays
• Glints from Space Junk
• Image Defects
• False positives killed the efforts by the
  MIT/GODDARD team with the ETC (Explosive
  Transient Camera) in the early 1990s.

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Human VisionA Closed Loop Real Time System

• Wide-field, low resolution imaging by rods cells
  of retina
• Narrower field, higher spatial resolution imaging
  by cone cells of fovea---yields color information
• Binocular vision---for distance information and
  correction of image defects
• Processor running complex real time
  software---the brain
• Eyes are rapidly slewing to quickly point the
  fovea for follow-up observations
• Brain has an adaptive catalog---our memory

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Raptor Sky Monitoring with Both Eyes Open

• Wide-field imaging system monitors 1300
  square-deg with resolution 35 arcsec and
  limiting magnitude of R13th in 60 seconds. (
  like the rod cells of the retina )
• Each array has a fovea telescope with
  limiting magnitude of R16.5 (60 sec),
  resolution of 7 arcsec and Gunn g (or r) filter.
  Provides color, better resolution, and faster
  cadence light curves (cone cells of fovea)
• Rapidly slewing mount places the fovea anywhere
  in the field in lt3 seconds. (rapid eye movement).
• Two identical arrays are separated by 38 km.
  (stereoscopic vision)

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Prompt Optical Emission from a Below Average
Gamma Ray Burst
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Simultaneous Two Color Measurements during the
first minute

• Color measurements? slope of continuum, that plus
  time evolution yields basic parameters of flow
  the Lorentz factor, the ambient density, the
  fraction of the energy in mass of the particles,
  and the fraction of the energy in the magnetic
  field

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GRB Precursors, Short Duration GRBs, and the
First Few Seconds

• Are there optical precursor flashes to GRBs?
• Do short duration GRBs generate prompt optical
  emission?
• What happens in the first few seconds of a long
  duration GRB?
• These important questions cannot be answered by
  any rapidly slewing telescope.

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The Solution Wide-Field Stereoscopic Monitoring

• RAPTOR continuously monitors essentially all of
  the field-of-view (FOV)of the Swift burst alert
  telescope. (gt1000 times the FOV of typical wide
  field telescope.)
• RAPTOR has the capability to find GRB precursors,
  prompt emission from short Duration GRBs and
  observe the first few seconds of long GRBs.

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Current Status

• Full stereoscopic closed loop operation is now
  operating.
• Stereoscopic viewing reduces the number of false
  positives from more than a thousand per night to
  less than a few per night.

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Moving Toward a Thinking System

• Goal is to build a system that not only
  recognizes transients, but also recognizes
  important anomalies in persistent objects and
  performs prompt follow-up observations in real
  time.
• To do this, we need--
• A record of the variability of sky that is
  continuously updated to place the observed
  variation in context.
• Machine Learning and Data Mining tools able to
  find and recognize the important variations in
  the flood of incoming measurements.

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http//skydot.lanl.gov
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Public SkyDOT website
skydot.lanl.gov
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Conclusions

• Time Domain Astronomy is too important to be
  left to the Astronomers.
• To be effective it requires real-time follow-up
  observations.
• We do not have the attention span, response
  time, or memory required to monitor the huge
  volume of data, recognize important variations,
  and respond.
• Autonomous Robotic Telescopes with smarts and
  the ability to learn will be essential for
  exploring the Time Domain in astronomy.