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What are
Gamma Waves?
?
Gamma-rays can kill living cells, a fact
which medicine uses to its advantage, using
gamma-rays to kill cancerous cells.
Gamma-rays have the smallest wavelengths and
the most energy of any other wave in the
electromagnetic spectrum.
http://www.rantscheff.com/mufx.htm
http://imagers.gsfc.nasa.gov/ems/gamma.html
What causes Gamma Waves?
Gamma-rays are the most energetic form of light and are produced by the hottest
regions of the universe. They are produced by violent events like supernova explosions
and by less dramatic events, such as the decay of radioactive material in space.
Cosmic sources of gamma rays (mainly all cosmic particle accelerators) include solar flares,
supernovae, cosmic rays, neutron stars and pulsars.
http://swift.gsfc.nasa.gov/docs/swift/results/releases/images/SN2006X/SN2006X_before_after.jpg
http://imagers.gsfc.nasa.gov/ems/gamma.html
In the late 1960s and early 1970s. Detectors on board military
satellites, began to record bursts of gamma-rays -- not from
Earth, but from deep space.
http://imagers.gsfc.nasa.gov/ems/gamma.html
Gamma-ray bursts (or
GRB’s) which happen
at least once a day, are
seen to last for
fractions of a second to
minutes, popping off
like cosmic flashbulbs
from unexpected
directions, flickering,
and then fading after
briefly dominating the
gamma-ray sky.
Gamma-ray bursts can
release more energy in
10 seconds than the
Sun will emit in its
entire 10 billion-year
lifetime!
http://imagers.gsfc.nasa.gov/ems/gamma.html
So far, it appears that all of the bursts
we have observed have come from
outside the Milky Way Galaxy.
Scientists believe that a gamma-ray burst will occur once every few million
years here in the Milky Way, and in fact may occur once every several
hundred million years within a few thousand light-years of Earth.
Scientists believe these bursts could be caused by the collision of two neutron stars.
http://www.nasa.gov/mpg/114919main_neutron_star_NASA%20WebV_1.mpg
http://www.nasa.gov/mission_pages/swift/bursts/short_burst_oct5.html
•
Most of the radiation emitted from the accretion friction in an AGN with a
central black hole motor (which draws in the surrounding gas) is gamma in
nature.
Scientists also believe GRB’s could be the result of a neutron star getting pulled
apart and falling into one such black hole.
http://t2www.nasa.r3h.net/mpg/135241main_neutronstar4lunch-magic.mov_NASA%20WebV_Oct3.mpg
http://www.space.com/SpaceReportersNetworkAmateurAstronomy/Newton_Gammarayburts_200202.html
http://www.nasa.gov/mission_pages/swift/bursts/short_burst_oct5.html
By solving the mystery of gamma-ray bursts, scientists hope to gain further
knowledge of the origins of the Universe, the rate at which the Universe is
expanding, and the size of the Universe.
One way they are doing so is with the SWIFT satellite.
Swift is a first-of-its-kind multi-wavelength observatory dedicated to the study
of gamma-ray burst (GRB) science. It has three instruments which work
together to observe GRBs and afterglows in the gamma ray, X-ray, ultraviolet,
and optical wavebands. The main mission objectives for Swift are to:
1. Determine the origin of gamma-ray bursts
2. Classify gamma-ray bursts and search for new types
3. Determine how the blastwave evolves and interacts with the surroundings
4. Use gamma-ray bursts to study the early universe
5. Perform the first sensitive hard X-ray survey of the sky
http://heasarc.gsfc.nasa.gov/docs/swift/about_swift/
Instruments
Swift's Burst Alert Telescope
(BAT)
The Burst Alert Telescope (BAT) is a
highly sensitive, large FOV
instrument designed to provide
critical GRB triggers and 4-arcmin
positions. It is a coded aperture
imaging instrument with a 1.4
steradian field-of-view (half coded).
Within several seconds of detecting
a burst, the BAT calculates an initial
position, decides whether the burst
merits a spacecraft slew and, if so,
sends the position to the spacecraft.
In order to study bursts with a variety of intensities, durations, and temporal structures,
the BAT must have a large dynamic range and trigger capabilities. The BAT uses a twodimensional coded aperture mask and a large area solid state detector array to detect
weak bursts, and has a large FOV to detect a good fraction of bright bursts. Since the BAT
coded aperture FOV always includes the XRT and UVOT fields-of-view, long duration
gamma-ray emission from the burst can be studied simultaneously with the X-ray and
UV/optical emission. The data from the BAT can also produce a sensitive hard X-ray allsky survey over the course of Swift's two year mission.
In order to study bursts with a variety of intensities, durations, and temporal
structures, the BAT must have a large dynamic range and trigger capabilities.
The BAT uses a two-dimensional coded aperture mask and a large area solid
state detector array to detect weak bursts, and has a large FOV to detect a good
fraction of bright bursts.
Instruments
Swift's X-Ray Telescope
(XRT)
Swift's X-Ray Telescope (XRT) is
designed to measure the fluxes,
spectra, and lightcurves of GRBs
and afterglows over a wide
dynamic range covering more than
7 orders of magnitude in flux. The
XRT can pinpoint GRBs to 5arcsec accuracy within 10 seconds
of target acquisition for a typical
GRB and can study the X-ray
counterparts of GRBs beginning
20-70 seconds from burst
discovery and continuing for days
to weeks.
The blue circle shows the BAT "Error Circle", which is the region of the sky
containing the source, given the position uncertainty of the BAT instrument. The
actual source location is shown by the false-color blob centered on this image,
which shows the focal spot of the XRT mirrors. The position of this source can be
determined by the XRT to within about 1 pixel (2.4 arcseconds).
Instruments
Swift's Ultraviolet/Optical Telescope
(UVOT)
Ground observations of GRBs have shown
that optical afterglows typically decline
in brightness as t -1.1 to t -2.1.
Therefore, rapid response is required
to observe these counterparts and
determine their redshift while they are
still bright. The UVOT is uniquely
capable for afterglow studies. It has
UV capability which is not possible
from the ground. It cannot be clouded
out. It is also much more sensitive
than any other quick reaction
telescope. The UVOT also enables
optimal ground based observations by
providing rapid optical images of the
GRB field so that any optical or IR
counterpart can be quickly identified
and studied. Stars in the FOV of the
UVOT provide an astrometric grid for
the GRB field.
Here is an optical image of
a GRB afterglow, two days
after it went off. This
observation was made using
a large ground-based
telescope (the 4.2 meter
William Herschel Telescope,
observation by Paul Groot)
when it was around
magnitude 20. This image is
cropped to 2 arcminutes
(compared to 17 arcmin for
the UVOT FOV). The size of
the 5 arcsecond diameter
position determination from
the XRT is shown as a green
circle. The UVOT will be able
to determine the location of
any afterglow it sees to an
accuracy of a few tenths of
an arcsecond.
SAMPLE OBSERVATION:
April 3, 2006 GRB060403
TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4945
SUBJECT: GRB 060403: Swift detection of a burst
DATE: 06/04/03 13:40:52 GMT
FROM: Scott Barthelmy at NASA/GSFC P. T. Boyd (NASA/GSFC), S. D.
Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/ORAU), N.
Gehrels (NASA/GSFC), C. Gronwall (PSU), S. T. Holland (GSFC/USRA), J. A.
Kennea (PSU), H. A. Krimm (GSFC/USRA), V. La Parola (INAF-IASFPA), V.
Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), P. Romano (INAF-OAB) and T. Sakamoto (NASA/ORAU)
report on behalf of the Swift Team:
At 13:12:17 UT, the Swift Burst Alert Telescope (BAT)
triggered and located GRB 060403 (trigger=203755). Swift
slewed immediately to the burst. The BAT on-board
calculated location is RA,Dec 282.306, +8.330 {18h 49m 13s,
+08d 19' 47"} (J2000) with an uncertainty of 3 arcmin
(radius, 90% containment, including systematic uncertainty).
The BAT light curve shows a single FRED-like peak structure
with a duration of about 25 sec. The peak count rate was
~2000 counts/sec (15-350 keV), at ~0 sec after the trigger.
Recent sightings!!!!!
http://grb.sonoma.edu/?
For Educators…
http://swift.sonoma.edu/