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.

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.

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.

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!

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.

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

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

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. Instruments 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. 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 all- sky 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.

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 5- arcsec accuracy within 10 seconds of target acquisition for a typical GRB and can study the X-ray counterparts of GRBs beginning seconds from burst discovery and continuing for days to weeks. Instruments

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).

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 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. Instruments

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.

April 3, 2006 GRB TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4945 SUBJECT: GRB : 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 (trigger=203755). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec , {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 ( keV), at ~0 sec after the trigger. SAMPLE OBSERVATION:

Recent sightings!!!!!

For Educators…