Gamma Ray Bursts

Just before 2000 UTC on 14 January, the Fermi and Swift satellites detected a spike of gamma rays from the constellation Fornax. The missions alerted the astronomical community to the location of the burst, dubbed GRB 190114C. Ground-based facilities detected radiation with up to a trillion times the energy of visible light from the gamma-ray burst.

The illustration above shows the set-up for the most common type of GRB. The core of a massive star (left) has collapsed and formed a black hole. This “engine” drives a jet of particles that moves through the collapsing star and out into space at nearly the speed of light. The so-called prompt emission, which typically lasts a minute or less, may arise from the jet’s interaction with gas near the newborn black hole and from collisions between shells of fast-moving internal shockwaves within the jet itself. The afterglow emission occurs as the leading edge of the jet sweeps through the surroundings creating an external shock wave, and emitting radiation across a broad spectrum. That may continue for months to years in the case of radio and visible light and for hours at the highest gamma-ray energies yet observed.

Image Credit: NASA

Note: My principal contribution to the Swift satellite was the design and testing of the power regulation system for the X-ray detectors in Burst Alert Telescope.

GRB 080916C

Gamma ray bursts are the brightest explosions we see in the Universe. The farthest known GRB occurred 12.2 billion light-years away in the constellation Carina. The explosion that created GRB 080916C contained the power of 9,000 supernovae. This very short movie shows Fermi Large Area Telescope observations of GRB 080916C. About 8 minutes of data are compressed into 6 seconds. The colored dots represent gamma rays of different energies. The blue dots represent lower-energy gamma rays; green, moderate energies; and red, the highest energies.

Video Credit: NASA / DOE / Fermi LAT Collaboration

Gamma Ray Burst

When a massive star collapses to form a black hole, a burst of gamma rays results as particles are blasted outward at nearly the speed of light. This animation shows the most common type of gamma-ray burst. An end-on view of a jet greatly boosts its apparent brightness. One especially bright burst (GRB 130427A) was detected in 2013 by the Fermi and Swift satellites. A Fermi image of that burst ends the animation sequence.

Video Credit: NASA

Swift’s Gamma Ray Burst Number 1,000

grb151027b_uvot_xrt_labeled_2160GRB 151027B, Swift‘s 1,000th burst, is in the center of this composite X-ray, ultraviolet, and optical image. X-rays were captured by Swift‘s X-Ray Telescope within minutes after the Burst Alert Telescope detected the blast. Swift‘s Ultraviolet/Optical Telescope (UVOT) began observations a few seconds later and faintly detected the burst in visible light. The image includes X-rays with energies from 300 to 6,000 eV, mostly from the burst, and lower-energy light seen through the UVOT’s visible, blue and ultraviolet filters (color shifted, respectively, to red, green and blue).

Image Credit: NASA

Gamma Ray Burst

When a massive star collapses to form a black hole, a burst of gamma rays results as particles are blasted outward at nearly the speed of light. This animation shows the most common type of gamma-ray burst. An end-on view of a jet greatly boosts its apparent brightness. One especially bright burst (GRB 130427A) was detected last April by the Fermi and Swift satellites. A Fermi image of that burst ends the animation sequence.

Video Credit: NASA

An Afterglow

hs-2013-29-a-full_jpgThese picture taken by the Hubble Space Telescope reveal a stellar explosion apparently caused by the merger of two compact objects. Hubble spotted the outburst while looking for the aftermath of a short-duration gamma-ray burst. GRBs are flashes of intense high-energy radiation that come from random directions in space. The short-duration bursts last only a few seconds but occasionally produce dim afterglows in visible and near-infrared light that last for hours or days. That afterglow can permit astronomers to find the exact location of the burst.

The galaxy in the center of the left-hand image is about 4 billion light-years away. It produced a gamma-ray burst designated GRB 130603B. A Hubble image taken on 13 June, 2013, shows a glow in near-infrared light at the source of the gamma-ray burst (top right). On 3 July, the source had faded (lower right). The fading glow suggests that the afterglow was the decaying fireball of a newly discovered type of stellar blast called a kilonova.

Kilonovas are about 1,000 times brighter than a nova caused by the eruption of a white dwarf. But they are only about 1 to 10 percent the brightness of a typical supernova, the self-detonation of a massive star.

Image Credit: NASA/ESA

Gamma Rays!

Fermi_LAT_GRB_673Just after 07:47 UTC last Saturday, the Gamma-ray Burst Monitor (GBM) aboard the Fermi satellite triggered on an eruption of high-energy light in the constellation Leo. Click on the image to see an animation showing a more detailed Fermi Large Area Telescope view. GRB 130427A produced the highest-energy light ever detected from gamma ray burst. The sequence shows high-energy (100 MeV to 100 GeV) gamma rays from a 20-degree-wide region of the sky starting three minutes before the burst to 14 hours after. After a one-second spike, the burst’s output remained relatively quiet for the next 15 seconds while Fermi‘s GBM showed bright, variable lower-energy emission. Then the burst re-brightened in the LAT over the next few minutes and remained bright for almost half a day. The record-setting blast of gamma rays came from a dying star in a distant galaxy roughly 3.6 billion light-years away.

Fermi’s Large Area Telescope (LAT) recorded one gamma ray with an energy of at least 94 billion electron volts (GeV), or some 35 billion times the energy of visible light, and about three times greater than any previous GRB. The GeV emission from the burst lasted for several hours, and it remained detectable by the LAT for the most of the day, making it the longest gamma-ray emission from a GRB detected to date.

The burst occurred as NASA’s Swift satellite was slewing between targets, which delayed its Burst Alert Telescope’s (BAT) detection by less than a minute. (The BAT is a wide-angle detector that can quickly determine the bearing to a gamma ray source. I designed the low-noise power regulators that feed the detector array in the BAT.) The burst was detected in optical, infrared and radio wavelengths by ground-based observatories using the rapid, accurate position from Swift.

Swift_XRTSwift‘s X-Ray Telescope took this image of GRB 130427A at 07:50 UTC on 27 April, moments after Swift and Fermi triggered on the GRB.

Gamma-ray bursts are the universe’s most luminous explosions. We believe that most occur when massive stars run out of nuclear fuel and collapse under their own weight. As the core collapses into a black hole, jets of material explode outward at almost the speed of light.

Image Credits: NASA

Gamma Rays for Christmas

GRB_111209AThe gamma ray burst (GRB) from GRB 111209A (aka the Christmas Burst) was detected in early December, 2011. The blast produced high-energy emission for an astonishing seven hours, the longest-duration GRB ever observed. This false-color image shows the event as captured by the X-ray Telescope aboard NASA’s Swift satellite. Because the distance to the burst was not measured initially, astronomers came up with a couple of radically different interpretations. In one scenario, a solitary neutron star in our own galaxy shredded and accreted an approaching comet-like body. In the other, a neutron star spiraled into and was eaten by a giant star in a distant galaxy. Now, a third explanation has been advanced. After a measurement of the Christmas Burst’s host galaxy, it appears that the GRB resulted from the collapse and explosion of a supergiant star hundreds of times larger than the sun.

[youtube http://www.youtube.com/watch?v=MVQI8RC67Yw]

Image Credit: NASA