Faculty

• Stephane Coutu
• Douglas Cowen
• Tyce DeYoung
• Derek B. Fox
• Peter Mészáros (Director)
• Irina Mocioiu
• Paul Sommers
• Mark Strikman

To the Swift

The Swift Gamma Ray Burst Explorer satellite detected in February of 2006 the longest-lasting burst so far, labelled GRB060218, more than 2000 seconds long. Such gamma ray bursts are known to result from stars more massive than 25 solar masses which undergo core collapse, resulting in a highly relativistic jet which produces the gamma-rays, and at the same time the star ejects its outer envelope in a supernova explosion. While the gamma-rays from jets have been extensively studied, this is the first time that the supernova explosion has been observed as it breaks out from the opaque stellar wind of the progenitor star. Swift's sensitive X-ray detectors observed a characteristic black-body emission, which starts out weak compared to the non-thermal gamma/X spectrum of the jet burst, and becomes dominant by the time the jet burst ends, indicating the break-out of the supernova shock wave. Members of the Swift Penn State team published these results in a recent issue of Nature (vol. 442, p. 1008, August 31, 2006).

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The Center for Particle Astrophysics is engaged in a bold synergistic approach to understanding high energy processes in the universe. Our faculty at Penn State are prominent participants in three major international projects which make observations using extremely high energy protons, neutrinos and gamma-rays. These projects are, respectively, the Pierre Auger Cosmic Ray Observatory, the IceCube Neutrino Observatory and the Swift Gamma-Ray Burst Explorer satellite. Both Auger and IceCube are in advanced stages of construction and are poised to make major discoveries in the next few years. Penn State is the only U.S. institution participating in both of these premier ground-based projects of high energy particle astrophysics. Potentially observable sources for both Auger and IceCube include super-massive black holes at the center of active galaxies, and the explosive phenomena that give rise to gamma ray bursts (GRBs). These are believed to be especially violent supernova explosions and also mergers of collapsed stars in binary systems. Swift is presently providing the best gamma ray and X-ray observations of GRB explosions. Swift has been successfully operating for over three years, its mission control center being at Penn State. Penn State also plays a leading role in theoretical modeling of these explosions.

GRBs, and the mergers of super-massive black holes in the core of galaxies and quasars are also likely sources of detectable gravitational waves. Together with the Center for Gravitational Wave Physics, our Center will be studying GRBs and active galaxies by observing strong-interaction protons, weak-interaction neutrinos, electromagnetic gamma rays, and gravitational waves. Together, we cover all four forces of nature. This multi-force approach to high energy astrophysics is a pioneering venture in which the one-dimensional electromagnetic spectrum of conventional astronomy is supplemented with three other windows to the Universe. The discovery potential is enormous. Together with the Center for Fundamental Theory and the Institute for Gravitation and the Cosmos, the synergy between our various specialties and the breadth of knowledge to be gained through collaborations provide exciting prospects for making breakthroughs in our understanding of the Cosmos.