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The GLAST Burst Monitor (GBM) is designed to provide wide field of view observations of gamma-ray bursts and other fast transient sources in the energy range 10 keV to 30 MeV. The GBM is composed of several unshielded and uncollimated scintillation detectors (twelve NaI and two BGO) that are widely dispersed about the GLAST spacecraft. As a result, reconstructing source locations, energy spectra, and temporal properties from GBM data requires detailed knowledge of the detectors' response to both direct radiation as well as that scattered from the spacecraft and Earth's atmosphere. This full GBM instrument response will be captured in the form of a response function database that is derived from computer modeling and simulation. The simulation system is based on the GEANT4 Monte Carlo radiation transport simulation toolset. [ABSTRACT FROM AUTHOR]

The origin of the soft gamma-ray (200 keV – 1 MeV) galactic ridge emission is one of the long-standing mysteries in the field of high-energy astrophysics. Population studies at lower energies have shown that emission from accreting compact objects gradually recedes in this domain, leaving place to another source of gamma-ray emission that is characterised by a hard power-law spectrum extending from 100 keV up to 100 MeV The nature of this hard component has remained so far elusive, partly due to the lack of sufficiently sensitive imaging telescopes that would be able to unveil the spatial distribution of the emission. The SPI telescope aboard INTEGRAL allows now for the first time the simultaneous imaging of diffuse and point-like emission in the soft gamma-ray regime. We present here all-sky images of the soft gamma-ray continuum emission that clearly reveal the morphology of the different emission components. We discuss the implications of our results on the nature of underlying emission processes and we put our results in perspective of GLAST studies of diffuse galactic continuum emission. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

One of the scientific goals of the Large-Area Telescope (LAT) on GLAST is the study of gamma-ray bursts (GRBs) in the energy range from ∼20 MeV to ∼300 GeV. In order to extend the energy measurement towards lower energies a secondary instrument, the GLAST Burst Monitor (GBM), will measure GRBs from ∼10 keV to ∼30 MeV and will therefore allow the investigation of the relation between the keV and the MeV-GeV emission from GRBs over more than six energy decades. These unprecedented measurements will furthermore permit the exploration of the unknown aspects of the high-energy burst emission. The status of the GBM project approximately one year before launch is reported here. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We introduce focusing optics and microcalorimeter spectroscopy to nuclear line emission astrophysics with a balloon payload concept called, B-MINE. It is designed to probe the deepest regions of a supernova explosion by detecting 44Ti emission at 68 keV with spatial and spectral resolutions that are sufficient to determine the velocity distribution of the 44Ti emitting region. B-MINE has a thin plastic foil telescope multilayered to maximize the reflectivity in a 20 keV band centered at 68 keV and a microcalorimeter array optimized for the same energy band. This combination provides a reduced background, an energy resolution of 50 eV and a 3σ sensitivity in 106 s of 6 × 10-8 ph cm-2 s-1 at 68 keV. During the course of a long duration balloon flight, B-MINE could carry out a detailed study of the 44Ti emission line centroids and width in CAS A. Details of the spectrometer and simulated results are presented. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Gamma Ray Large Area Space Telescope (GLAST) mission is a followup to the successful EGRET experiment onboard the Compton Gamma Ray Observatory (CGRO). It will provide a high-sensitivity survey of the sky in high-energy γ-rays, and will perform detailed observations of persistent and transient sources. There are two experiments onboard the GLAST — the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The primary mission of the GBM instrument is to support the LAT in observing γ-ray bursts (GRBs) by providing low-energy measurements with high time resolution and rapid burst locations over a large field-of-view (>= 8 sr). The GBM will complement the LAT measurements by observing GRBs in the energy range 10 keV to 30 MeV, the region of the spectral turnover in most GRBs. An important objective of the GBM is to compute the locations of GRB sources on-board the spacecraft and quickly communicate them to the LAT and to the ground to allow rapid followup observations. This information may be used to re-point the LAT towards particularly interesting burst sources that occurred outside its field-of-view. The GBM consists of 14 uncollimated scintillation detectors coupled to phototubes to measure γ-ray energies and time profiles. Two types of detectors are used to obtain spectral information over a wide energy range: 12 NaI(Tl) detectors (10 keV to 1 MeV), and 2 BGO detectors (150 keV to 30 MeV). The detectors are distributed around the GLAST spacecraft to provide a large, unobstructed field of view. The 12 NaI(Tl) detectors are mounted with different orientations for use in locating GRB sources. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Gamma Ray Large Area Space Telescope (GLAST), scheduled for launch in 2006, comprises a Large Area Telescope (LAT) and a GLAST Burst Monitor (GBM). The LAT is a pair telescope with unprecedented sensitivity in the 20 MeV to 300 GeV energy range. The GLAST Burst Monitor consists of an array of NaI and BGO scintillation detectors operating in the 10 kev to 25 MeV range and covering a wide field of view. The GBM will enhance LAT observations of GRBs by extending the spectral coverage into the range of current GRB databases, and will provide a trigger for repointing the spacecraft to observe delayed emission from bursts outside the LAT field of view. [ABSTRACT FROM AUTHOR]

Classical novae are considered to be the major source of the ISM enrichment with the isotopes of [sup 13]C, [sup 15]N, and [sup 22]Na. The latter, radioactive [sup 22]Na, that decays producing penetrating 1.275 MeV γ-ray photon, could be very useful as a probe of the galactic global distribution of novae. It is expected that the accumulation of [sup 22]Na from the frequent novae in the bulge will lead to an observable extended emission. Additionally, a [sup 22]Na detection from the single nova can be used to verify predictions of the modem thermonuclear runaway theory (TNR) applied to classical novae. To gain a better insight into this problem we have used a two-way approach. Namely: (1) — we have studied the global galactic distribution of the 1.275 MeV γ-ray line emission assuming that it is mostly originates from decay of the novae-produced [sup 22]Na; and (2) — we pursued the [sup 22]Na line emission detection from recent individual novae. The combination of both approaches makes possible to tap rather uncertain galactic novae rate by comparing observations of the individual Galactic novae with the integrated [sup 22]Na line emission from the disk and/or bulge population. The COMPTEL telescope on board the Compton Gamma-Ray Observatory (CGRO), due to its combination of imaging and spectroscopic capabilities, is suitable to address the above ideas. [ABSTRACT FROM AUTHOR]

During the CGRO mission, the Galactic centre region was well exposed by COMPTEL. There is evidence for a distinct excess near the Galactic centre direction in the COMPTEL energy range 1 - 30 MeV. The analysis for point sources is however complicated by the intense emission from the Galactic ridge. We use data from the full mission to investigate this source, present a multiwavelength spectrum and discuss various possible counterparts, including the microquasar source 1E1740.7 - 2942. [ABSTRACT FROM AUTHOR]

The COMPTEL telescope on board the Compton Gamma-Ray Observatory (CGRO) is capable of imaging γ-ray line sources, like classical novae, in the MeV regime at a level of sensitivity up to a few 10[SUP-5] photons cm[SUP-2]s[SUP-1]. At this level of sensitivity quite high expectations can be placed on the detection of the predicted [SUP22]Na γ-ray line at 1.275 MeV from nearby novae. Unfortunately, no positive detection of the nova-produced [SUP22]Na was reported until recently. We have used COMPTEL data collected up to the 2nd CGRO reboost to assess (1) - sodium production by individual novae, and (2) - the Galactic distribution of the nova-produced [SUP22]Na. [ABSTRACT FROM AUTHOR]

The star forming process in the Milky Way is non-uniform in time and space. The scale of star forming regions ranges from groups within a few pc to large segments of spiral arms with linear dimension of order kpc. When many stars form in a relatively small volume over a short duration, a localized starburst ensues. The energetic impact of such a burst of star formation can severely affect the dynamic structure of the gaseous disk. Stellar winds and supernova explosions drive an expanding superbubble, whose size eventually exceeds the scale height of the disk and thus drives a disk-wind blowing metal enriched gas into the halo. We discuss the basic scenario of superbubble evolution, emphasizing the associated gamma-ray line signatures. In particular, we discuss nuclear line emission from [SUP26]Al and [SUP60]Fe in the Cygnus region. [ABSTRACT FROM AUTHOR]

The "Pre-SMM" (Vestrand and Miller 1998) picture of gamma-ray line (GRL) flares was that they are relatively rare events. This picture was quickly put in question with the launch of the Solar Maximum Mission (SMM). Over 100 GRL flares were seen with sizes ranging from very large GOES class events (X12) down to moderately small events (M2). It was argued by some (Bai 1986) that this was still consistent with the idea that GRL events are rare. Others, however, argued the opposite (Vestrand 1988; Cliver, Crosby and Dennis 1994), stating that the lower end of this distribution was just a function of SMM's sensitivity. They stated that the launch of the Compton Gamma-ray Observatory (CGRO) would in fact continue this distribution to show even smaller GRL flares. In response to a BACODINE cosmic gamma-ray burst alert, COMPton TELescope on the CGRO recorded gamma rays above 1 MeV from the C4 flare at 0221 UT 20 January 2000. This event, though at the limits of COMPTEL's sensitivity, clearly shows a nuclear line excess above the continuum. Using new spectroscopy techniques we were able to resolve individual lines. This has allowed us to make a basic comparison of this event with the GRL flare distribution from SMM and also compare this flare with a well-observed large GRL flare seen by OSSE. [ABSTRACT FROM AUTHOR]

The June 11,1991 gamma-ray flare seen by the Compton Gamma-ray Observatory (CGRO) displays several features that make it a dynamic and rich event. It is a member of a class of long duration gamma-ray events with both 2.223 MeV and greater than 8 MeV emission for hours after the impulsive phase. It also contains an inter-phase between the impulsive and extended phases that presents a challenge to the standard gamma-ray line (GRL) flare picture. This phase has strong 2.223 MeV emission and relatively weak 4.44 MeV emission indicative of a very hard parent proton spectrum. However, this would indicate emission greater than 8 MeV, which is absent from this period. We present the application of new spectroscopy techniques to this phase of the flare in order to present a reasonable explanation for this seemly inconsistent picture. [ABSTRACT FROM AUTHOR]

The study of gamma-ray bursts (GRBs) is one of the primary scientific objectives of the Gamma-ray Large Area Space Telescope (GLAST) mission. With its high sensitivity to prompt and extended 20 MeV to 300 GeV burst emission, GLAST's Large Area Telescope (LAT) is expected to yield significant progress in the understanding of GRB physics. To tie these breakthrough highenergy measurements to the known properties of GRBs at lower energies, the GLAST Burst Monitor (GBM) will provide spectra and timing in the 10 kev to 25 MeV energy range. The GBM will also have the capability to quickly localize burst sources to ∼ 15[°] over more than half the sky, allowing the LAT to re-point at particularly interesting bursts which occur outside its field of view. With combined LAT/GBM measurements GLAST will be able to characterize the spectral behavior of many bursts over nearly six decades in energy. This will allow the unknown aspects of high-energy burst emission to be explored in the context of well-known low-energy properties. In this paper, we present an overview of the GBM instrument, including its technical design, scientific goals, and expected performance. [ABSTRACT FROM AUTHOR]

The SPI Imaging Test Setup (SPITS) was built at MPE to allow experimental verification of the imaging properties of the SPectrometer onboard INTEGRAL (SPI). Of special importance is the possibility to validate simulations -- which are needed for SPI image reconstruction -- with laboratory measurements. SPITS consists of a coded mask and two Germanium detectors. The coded mask has the same tungsten-alloy HURA mask coding as SPI and is made of SPI flight model materials. The two hexagonal Ge-detectors are from the SPI flight detector manufacturing line. Housed in a common A1 vacuum cap and mounted on an XY-table, they can be moved to cover the 19 Ge detector positions of the SPI camera. We have measured the response of SPITS to radioactive sources (60 keV to 1.8 MeV) at a distance of 9 m from the detector plane. We use both image deconvolution algorithms foreseen for SPI data analysis (spiros and spiskymax) for our analysis. We present our findings for the angular resolution and the point-source-location capability of SPITS for several photon energies and for several source geometries relative to the mask coding. [ABSTRACT FROM AUTHOR]

We present an updated version of COMPTEL’s 1.809 MeV sky survey. Based on eight years of observations we compare results from different imaging techniques using background from adjacent energy bands. We confirm the previously reported characteristics of the galactic 1.809 MeV emission, specifically an extended galactic ridge emission, mainly concentrated towards the inner galaxy, a peculiar emission feature in the Cygnus region, and a low-intensity ridge extending towards Carina and Vela. Because this gamma ray line is due to the decay of radioactive [sup 26]Al, predominantly synthesized in massive stars, one anticipates flux enhancements aligned with regions of recent star formation. This is born out by the observations. In particular the Cygnus feature, first presented in 1996 based on three years of COMPTEL data, is confirmed. Based on the stellar population we distinguish three prominent areas in this region, for which we separately derive fluxes, and discuss interpretations. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The COMPTEL map of the 1.809 MeV line, which is attributed to the radioactive decay of [sup 26]Al, shows significant excess emission in the Cygnus region. We investigate counterparts of this emission, based on COMPTEL data accumulated over 8 years. Previous studies suggested that this flux is due to the integrated, but unresolved, nucleosynthesis from young, massive objects like Wolf Rayet (WR) stars and core collapse supernovae. Beside a static scenario of known point sources-WR stars and SNRs-we consider OB associations in a dynamic scenario to model the observed flux in the Cygnus region. We carry out population synthesis studies to determine the time-dependent production of [sup 26]Al and also kinetic as well as radiative energy. Furthermore we consider the impact of enhanced [sup 26]Al yields probably occurring in a fraction of massive close binary systems. We compare the nucleosynthesis results of our OB association model with recent measurements in the Cygnus region. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report a refined analysis of the cosmic diffuse gamma-ray background (hereafter CDG) in the energy range 0.8–30 MeV with the Compton telescope COMPTEL onboard the Compton Gamma-Ray Observatory. We have identified all major instrumental-background lines, included the results of a detailed study of the instantaneous instrumental continuum-background characteristics, and used all available COMPTEL data at high galactic latitudes. The new “whole-sky” average CDG spectrum again shows no evidence for an MeV-bump, merges smoothly with the spectra at higher and lower energies, and is consistent with a transition from a softer to a harder component around a few MeV. This spectrum is consistent with previous COMPTEL results. In addition, comparison of the CDG intensity from various regions of the sky allows us to place limits on the large-scale anisotropy of the CDG in selected energy bands. Upper limits on the relative deviations from isotropy consistent with the data at the 95% confidence limit range from about 24% to about 45% on scales of a few steradian. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The type Ia supernova SN 1998bu in M96 was observed by COMPTEL for a total of 88 days starting 17 days after the detection of the SN. A special mode improving the low-energy sensitivity was invoked. We obtained images in the 847 keV and 1238 keV lines of [sup 56]Co using an improved point-spread function for the low-energies. We do not detect SN1998bu. Sensitive upper limits at both energies constrain the standard supernova model for this event. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Limitations in COMPTEL [sup 44]Ti line searches arise from uncertainties in different background modelling techniques, and in different event selection criteria to suppress a large part of the background. Therefore, the significance of the reported detections of Cas A and RX J0852-4622/GRO J0852-4642 have been reassessed in great detail. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The instrumental-line background of the Compton telescope COMPTEL onboard the Compton Gamma-Ray Observatory is due to the activation and/or decay of a number of different isotopes. The major components of the COMPTEL instrumental-line background can be attributed to eight individual isotopes, namely [sup 2]D, [sup 22]Na, [sup 24]Na, [sup 28]Al, [sup 40]K, [sup 52]Mn, [sup 57]Ni, and [sup 208]Tl. In addition, evidence for the presence of [sup 27]Mg has been obtained in the search for gamma-ray lines from supernovae. The identification of the instrumental lines with specific isotopes is based on the line energies as well as on the variation of the activity with time, cosmic-ray intensity and deposited radiation dose during passages through the South-Atlantic Anomaly. The characteristic variation of the activity due to an individual isotope depends on its life-time, orbital parameters, and the solar cycle. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In the course of the mission we have gradually developed an analysis method that separates in an iterative manner the celestial emission and the (a priori unknown) instrumental background. It has become our standard analysis tool for point sources. We illustrate here that this method is widely applicable now. It provides mutually consistent sets of model-fitting parameters (spectra) and sky maps, both for continuum and line studies. Because of the wide applicability, it has been possible to make various cross-checks while building up confidence in this procedure. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

© 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Energetic particles accelerated in supernova remnants provide a variety of continuum emission signatures over the entire electromagnetic spectrum. The measured hard X-ray continuum emission from the Cas A supernova remnant indicates in fact the presence of high-energy electrons and makes it an interesting candidate for study at MeV energies. We have analyzed COMPTEL data with respect to continuum emission in addition to the previously detected [sup 44]Ti line. The results provide useful constraints on models of electron shock acceleration in this object. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

[sup 44]Ti is one of the few radioactive nuclei produced abundantly in supernovae (SNe). Because its life time is comparable to the typical time between supernovae in the Galaxy, γ-ray lines from [sup 44]Ti provide a powerful tool for the search for optically obscured supernovae that occurred during the last few 100 years. We present our analysis of COMPTEL data (Cycle 1–6), comparing γ-ray line images and flux distributions with Monte Carlo simulations of SNe in the Galaxy. Assuming standard SNe distribution models and theoretical estimates of the [sup 44]Ti yields, we constrain the Galactic supernova rate. We compare these constraints with those obtained from the historical record covering the last millennium. Relating the current supernova rate to the observed [sup 44]Ti solar abundance through chemical evolution models, agreement can be obtained only if there is a special type of supernova (e.g., helium detonations) that produces large amounts of [sup 44]Ti, but with a very low event rate. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The spectrometer on INTEGRAL (SPI) is one of the two main telescopes of the future INTEGRAL observatory. SPI is made of a compact hexagonal matrix of 19 high-purity germanium detectors shielded by a massive anticoincidence system. A HURA type coded aperture modulates the astrophysical signal. The spectrometer system, its physical characteristics and performances are presented. The instrument properties such as imaging capability, energy resolution and sensitivity have been evaluated by means of extensive Monte-Carlo simulations. With the expected performances of SPI, it will be possible to explore the γ-ray sky in greater depth and detail than it was possible with previous γ-ray telescopes like SIGMA, OSSE and COMPTEL. In particular, the high-energy resolution will allow for the first time the measurement of γ-ray line profiles. Such lines are emitted by the debris of nucleosynthesis and annihilation processes in our Galaxy. Lines from these processes have already been measured, but due to the relatively poor energy resolution, details of the emission processes in the source regions could not be studied. With the high-resolution spectroscopy of SPI such detailed investigations will be possible. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The COMPTEL telescope on board the Compton Gamma-Ray Observatory (CGRO) is capable of imaging γ-ray line sources, like classical novae, in the MeV regime at a level of sensitivity up to a few 10[sup -5] photons cm[sup -2] s[sup -1]. At this level of sensitivity quite high expectations can be placed on the detection of the predicted [sup 22]Na γ-ray line at 1.275 MeV from nearby novae. We have used COMPTEL data collected up to the 2[sup nd] CGRO reboost to update previously published limits for the sodium production by novae. Results of the [sup 22]Na line emission studies from the old and the most recent novae are discussed and compared with model predictions. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]