David M. Palmer

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The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is a first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more(More)
We investigate spectral evolution in 37 bright, long gamma-ray bursts observed with the BATSE Spectroscopy Detectors. High resolution spectra are characterized by the energy of the peak of νFν and the evolution of this quantity is examined relative to the emission intensity. In most cases it is found that this peak energy either rises with or slightly(More)
The occurrence and visibility of meteoroid impacts on the moon as seen from the earth were little more than speculation prior to November 1999. The best evidence of present-day impact activity came from the seismic experiments left on the Moon during the Apollo era. Past systematic attempts at earth-based observations to document lunar impacts revealed(More)
Gamma-ray bursts (GRBs) come in two classes: long (> 2 s), soft-spectrum bursts and short, hard events. Most progress has been made on understanding the long GRBs, which are typically observed at high redshift (z approximately 1) and found in subluminous star-forming host galaxies. They are likely to be produced in core-collapse explosions of massive stars.(More)
Two classes of rotating neutron stars-soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars-are magnetars, whose X-ray emission is powered by a very strong magnetic field (B approximately 10(15) G). SGRs occasionally become 'active', producing many short X-ray bursts. Extremely rarely, an SGR emits a giant flare with a total energy about a thousand(More)
Although the link between long gamma-ray bursts (GRBs) and supernovae has been established, hitherto there have been no observations of the beginning of a supernova explosion and its intimate link to a GRB. In particular, we do not know how the jet that defines a gamma-ray burst emerges from the star's surface, nor how a GRB progenitor explodes. Here we(More)
The bright gamma-ray burst GRB 050525a has been detected with the Swift observatory, providing unique multiwavelength coverage from the very earliest phases of the burst. The X-ray and optical/UVafterglow decay light curves both exhibit a steeper slope 0.15 days after the burst, indicative of a jet break. This jet break time combined with the total(More)
Soft gamma-ray repeaters (SGRs) are 'magnetars', a small class of slowly spinning neutron stars with extreme surface magnetic fields, B approximately 10(15) gauss (refs 1 , 2 -3). On 27 December 2004, a giant flare was detected from the magnetar SGR 1806-20 (ref. 2), only the third such event recorded. This burst of energy was detected by a variety of(More)
Long gamma-ray bursts (GRBs) are bright flashes of high-energy photons that can last for tens of minutes; they are generally associated with galaxies that have a high rate of star formation and probably arise from the collapsing cores of massive stars, which produce highly relativistic jets (collapsar model). Here we describe gamma- and X-ray observations(More)
The Soft Gamma Repeater 1806-20 produced patterns of bursts during its 1983 outburst that indicate multiple independent energy accumulation sites, each driven by a continuous power source, with sudden, incomplete releases of the accumulated energy. The strengths of the power sources and their durations of activity vary over several orders of magnitude.(More)