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We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. In addition, rapid-response telescopes on the ground have new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and supernova physics. [ABSTRACT FROM AUTHOR]

We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains 476 bursts detected by the BAT between 2004 December 19 and 2009 December 21. This catalog presents burst trigger time, location, 90% error radius, duration, fluence, peak flux, time-averaged spectral parameters and time-resolved spectral parameters measured by the BAT. The BAT T90 duration peaks at 70 s. We confirm that the spectra of the BAT short-duration GRBs are generally harder than those of the long-duration GRBs. The observed durations of the BAT high redshift GRBs are not systematically longer than those of the moderate redshift GRBs. Furthermore, the observed spectra of the BAT high redshift GRBs are similar to or harder than the moderate redshift GRBs. [ABSTRACT FROM AUTHOR]

GRB 061007 had the brightest optical afterglow observed by UVOT so far and a highly unusual afterglow light curve. It had an usually smooth and steep panchromatic temporal decay, which, from the start of the Swift observations, decayed as a power with a slope of α = 1.65±0.02 in the X-ray and UV/optical bands. If we interpret the data in terms of a spherical blastwave, the energy budget that is implied is enormous, challenging the possible models for the progenitors. The alternative explanation is that with GRB 061007 we are witnessing the most collimated outflow ever observed. If this is correct, if implies the occurrence of a jet break within 80 s of the prompt emission. This event has therefore remarkable consequences for the GRB communicate, since it may imply that jet breaks can occur much earlier in the afterglow light curves than hitherto expected. [ABSTRACT FROM AUTHOR]

This is a short report on the preliminary findings of the gamma ray burst (GRB) working group for the white paper on the status and future of very high energy (VHE;>50 GeV) gamma-ray astronomy. The white paper discusses the status of past and current attempts to observe GRBs at GeV-TeV energies, including a handful of low-significance, possible detections. The white paper concentrates on the potential of future ground-based gamma-ray experiments to observe the highest energy emission ever recorded for GRBs, particularly for those that are nearby and have high Lorentz factors in the GRB jet. It is clear that the detection of VHE emission would have strong implications for GRB models, as well as cosmic ray origin. In particular, the extended emission phase (including both afterglow emission and possible flaring) of nearby long GRBs could provide the best possibility for detection. The difficult-to-obtain observations during the prompt phase of nearby long GRBs and short GRBs could also provide particularly strong constraints on the opacity and bulk Lorentz factors surrounding the acceleration site. The synergy with upcoming and existing observatories will, of course, be critical for both identification of GRBs and for multiwavelength/multimessenger studies. [ABSTRACT FROM AUTHOR]

Swift very fast follow up observations of Gamma-Ray Bursts have allowed us to discover a new feature of GRB afterglows: a phase of shallow decay, usually attributed to energy injection in the burst ejecta, which can last for several thousands of seconds both in the X-ray and optical bands. Here I shall discuss this phase in the cases of Swift GRBs 050401, 050801 and 050802. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Burst Alert Telescope (BAT), a large coded aperture instrument with a wide field-of-view (FOV), provides the gamma-ray burst triggers and locations for the Swift Gamma-Ray Burst Explorer. In addition to providing this imaging information, BAT will perform a 15 keV – 150 keV all-sky hard x-ray survey based on the serendipitous pointings resulting from the study of gamma-ray bursts, and will also monitor the sky for transient hard x-ray sources. For BAT to provide spectral and photometric information for the gamma-ray bursts, the transient sources and the all-sky survey, the BAT instrument response must be determined to an increasingly greater accuracy. This paper describes the spectral models and the ground calibration experiments used to determine the BAT response to an accuracy suitable for gamma-ray burst studies. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Burst Alert Telescope (BAT) on Swift has two main types of “rate” triggers: short and long. Short trigger time scales range from 4ms to 64ms, while long triggers are 64ms to ≈ 16 seconds. While both short and long trigger have criteria with one background sample (traditional “one-sided” triggers), the long triggers can also have criteria with two background samples (“bracketed” triggers) which remove trends in the background. Both long and short triggers can select energy ranges of 15–25, 15–50, 25–100 and 50–350 KeV. There are more than 180 short triggering criteria and approximately 500 long triggering criteria used to detect gamma ray bursts. To fully utilize these criteria, the thresholds must be set correctly. The optimum thresholds are determined by a tradeoff between avoiding false triggers and capturing as many bursts as possible. We use realistic simulated orbital variations, which are the prime cause of false triggers. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The BAT instrument tells Swift where to point to make immediate follow-up observations of GRBs. The science software on board must efficiently process γ-ray events coming in at up to 34 kHz, identify rate increases that could be due to GRBs while disregarding those from known sources, and produce images to accurately and rapidly locate new Gamma-ray sources. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We describe the Energetic X-ray Imaging Survey Telescope EXIST, designed to carry out a sensitive all-sky survey in the 10 keV – 600 keV band. The primary goal of EXIST is to find black holes in the local and distant universe. EXIST also traces cosmic star formation via gamma-ray bursts and gamma-ray lines from radioactive elements ejected by supernovae and novae. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Swift is a first-of-its-kind multiwavelength transient observatory for gamma-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of gamma-ray bursts and their afterglows, as well as using bursts to probe the early Universe. Swift will also perform the first sensitive hard Xray survey of the sky. The mission is being developed by an international collaboration and consists of three instruments, the Burst Alert Telescope (BAT), the X-ray Telescope (XRT), and the Ultraviolet and Optical Telescope (UVOT). The BAT, a wide-field gamma-ray detector, will detect 3-7 gamma-ray bursts per week with a sensitivity 5 times that of BATSE. The sensitive narrow-field XRT and UVOT will be autonomously slewed to the burst location in 20 to 70 seconds to determine 0.3-5.0 arcsec positions and perform optical, UV, and X-ray spectrophotometry. Strong education/public outreach and follow-up programs will help to engage the public and astronomical community. The Swift launch is planned for September 2003. [ABSTRACT FROM AUTHOR]

A next generation Gamma Ray Burst (GRB) mission to follow the upcoming Swift mission is described. The proposed Energetic X-ray Imaging Survey Telescope, EXIST, would yield the limiting (practical) GRB trigger sensitivity, broad-band spectral and temporal response, and spatial resolmion over a wide field. It would provide high resolmion spectra and locations for GRBs detected at GeV energies with GLAST. Together with the next generation missions Constellation-X, NGST and LISA and optical-survey (LSST) telescopes, EXIST would enable GRBs to be used as probes of the early universe and the first generation of stars. EXIST alone would give ∼10-50' positions (long or short GRBs), approximate redshifts from lags, and constrain physics of jets, orphan afterglows, nemrinos and SGRs. [ABSTRACT FROM AUTHOR]

The Compton Gamma Ray Observatory was de-orbited on 4 June 2000 after 9 highly successful years in orbit. Major discoveries were made every year with Compton. We present a retrospective overview of the mission from launch to deorbit,, highlighting some seminal scientific findings. [ABSTRACT FROM AUTHOR]

The Gamma-ray Large Area Space Telescope is planned as NASA’s next major mission in high-energy gamma-ray astronomy. It is included in the Space Science Enterprise Strategic Plan as a 2002 “New Start,” with a planned 2005 launch. NASA commissioned a Facility Science Team (FST) of both advocates and non-advocates to establish the framework of the mission. The FST developed a Science Requirements Document that outlines the specifications of an instrument needed to make the next advance in this field. The adopted specifications will lead to an investigation with an energy response extending to 300 GeV, ten times higher than the EGRET instrument on the Compton Observatory, and with a source sensitivity 50 times greater. In addition there would be gains in spectral and spatial resolution. A heavy emphasis will be placed on multi-wavelength observations to maximize the science from the mission. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In 1997, NASA convened a working group to provide input on the future of gamma-ray astronomy. This group, the Gamma-Ray Program Working Group or GRAPWG, was reconvened in 1998 to provide further input. This paper describes the scope and recommendations of this group. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

LOTIS (Livermore Optical Transient Imaging System) and Super-LOTIS are automatic telescope systems that search for prompt optical emission from gamma-ray bursts (GRBs). Both systems are capable of responding to the Gamma-ray burst Coordinate Network (GCN) triggers within seconds. These systems have been monitoring the GCN real-time data for automatic HETE2 GRB triggers since HETE2's launch. In this paper, we present the systems' capability and current status. We also present the result of the GRB010921 afterglow detection that was localized by HETE2 and the IPN. [ABSTRACT FROM AUTHOR]