Heather Swan

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Measuring Fast Spectral Variability of
GRB Early Afterglows with the
AEOS Burst Camera
Image of M8, taken by the AEOS Burst Camera

• Heather Swan
• Physics Department
• University of Michigan
• Carl Akerlof, Timothy McKay, Eli Rykoff, Donald
  Smith, U of Michigan
• Mark Skinner, Andrew Alday, Kevin Moore, Boeing
  LTS

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Outline

• Why?
• What is the AEOS and ABC?
• GRB response
• Data and simulations

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GRB 030418 was dimmer than expected at early times
Circum-burst absorbs optical light if we could
see the spectrum, we would expect to see red -gt
blue
Optical lightcurve
First image 76s after g-rays
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GRB 990123 was brighter than expected at early
times
Relativistic fireball example of a reverse
shock if we could see the spectrum, we would
expect to see blue -gt red
Optical lightcurve
g-rays were still emitting for first few images
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Swifts BAT error box is the perfect size for the
ABC
90 will be localized to a 3 arc minute
radius (Can see them with the ABC)
50 will be localized within 12 seconds (Can see
them promptly) (From Fenimore, et al)
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The AEOS telescope is a large optical telescope
used by the Air Force

• Advanced Electro-Optical Systems Telescope (AEOS)
• Largest ground based AF optical telescope
  (3.67m)
• Designed to track satellites, can quickly (20
  sec) slew to coordinates
• Located in Haleakala, Hawaii, at 10,000 ft

ABC
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The AEOS Burst Camera (ABC) is attached to the
AEOS

• Optics designed by Carl Akerlof
• Package designed by Alan Schier
• Camera built by Astronomical Research Cameras
• Field of view 6' x 6'
• Focal length of 15.5m
• 9 ToO observations / year

Limiting Mag 22nd for 10 sec exposure
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The ABC will try to observe GRBs within minutes
after they are localized
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No prompt response yet

• GRB needs to be lt 1 hour old and visible in Maui
• The few that have been attempted
• Bad weather
• Bad pointing
• Several test bursts have been sent
• Responses between 1 and 10 minutes
• One was caught during testing (030329)
• Images taken several days after the event

GRB 030329
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A diffraction grating was recently installed on
the ABC

• Low resolving power (8)
• Installed Jan 05

A light bulb viewed through the grating, and a
star.
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Simulations of the grating are similar to what is
seen
Blackbody, suns temp
1st
0th
2nd
higher orders
Image from ABC of a star
The blaze angle was chosen so most of the light
would be in the 1st order
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We can differentiate between blue and red stars
Cooler temps
Hotter temps
Simulations of different temperature blackbodies
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We can differentiate between different types of
objects
Quasar
Star
Symbiotic binary
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In summary, the ABC is up and running, were just
waiting for a GRB

• The ABC can quickly and deeply observe GRBs
• First image within minutes of GRB detection
• Small 6 x 6 field of view
• Deep (22nd mag) images with 10s exposures
• The ABC has a diffraction grating
• Will get early spectral information for GRBs

Questions?