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OAO 1657‐415 is an eclipsing X‐ray binary pulsar that has undergone several torque reversals throughout its long history of observation. We present a frequency history spanning nearly 19 years of observations from the Burst and Transient Source Experiment (BATSE) and from the Gamma‐Ray Burst Monitor (GBM). Orbital ephemerides of the pulsar system is obtained at several intervals throughout this history. With these ephemerides, statistically significant orbital decay is established.

We compiled X-ray and Optical observations of the accreting X-ray binary system A 0535+262 since its discovery in 1975, that will allow us to shed light on the unpredictable behavior of this binary system. We present the data in terms of the Be-disk interaction with the neutron star companion. In addition, we show recent results from the continuous monitoring of this source by the Gamma-ray Burst Monitor(GBM), on board the Fermi observatory, since its launch in 2008 June 11., Comment: 4 pages, 5 figures, Conference proceeding of "Astrophysics of Neutron Stars 2010 - a conference in honor of M. Ali Alpar", 2-6 August 2010, Cesme, Izmir, Turkey

On July 23, 2008 GRB 080723B, a bright GRB lasting about 105 s was detected by the INTEGRAL burst alert system. This burst was also detected by the Fermi Gamma‐ray burst monitor. At this time no Fermi/GBM GCN notices were distributed to the public because Fermi was still in commissioning phase. The simultaneous detection of a bright GRB by both satellites gives us the opportunity to cross‐calibrate the GBM with the already well‐calibrated instruments on‐board INTEGRAL, the Spectrometer SPI and the Imager IBIS. Time‐resolved spectroscopy of this long and structured GRB is of special importance because Fermi was slewing during the GRB was still ongoing. In this paper we present a first and still preliminary analysis of the GBM spectra and compare them to those obtained by SPI for the same selection of time intervals. A more accurate cross‐calibration will be forthcoming when the improved in‐flight calibration of GBM is available and the corresponding data and responses can be reprocessed.

One of the scientific objectives of NASA’s Fermi Gamma‐ray Space Telescope is the study of Gamma‐Ray Bursts (GRBs). The Fermi Gamma‐Ray Burst Monitor (GBM) was designed to detect and localize bursts for the Fermi mission. By means of an array of 12 NaI(Tl) (8 keV to 1 MeV) and two BGO (0.2 to 40 MeV) scintillation detectors, GBM extends the energy range (20 MeV to >300 GeV ) of Fermi’s main instrument, the Large Area Telescope (LAT), into the traditional range of current GRB databases. The physical detector response of the GBM instrument to GRBs is determined with the help of Monte Carlo simulations, which are supported and verified by on‐ground individual detector calibration measurements. We present the principal instrument properties, which have been determined as a function of energy and angle, including the channel‐energy relation, the energy resolution and the effective area.

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, and is being extensively validated against calibrated experimental GBM data. We discuss the architecture of the GBM simulation and modeling system and describe how its products will be used for analysis of observed GBM data. Companion papers describe the status of validating the system.

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.

The GLAST Burst Monitor (GBM) comprises 12 NaI and 2 BGO detectors dispersed about the GLAST spacecraft. The GBM instrument simulation software must generate an accurate response function database for all detectors in their flight configuration to optimize the mission science return. Before science analysis codes use the response database, we must confirm that our simulation codes and models can reproduce laboratory observations. To validate the simulation effort, Monte Carlo results are compared to calibrated laboratory measurements collected with a variety of radiation sources.

The GLAST Burst Monitor (GBM) consists of 12 NaI detectors and 2 BGO detectors mounted on two sides of the spacecraft. This provides detection capability for energies between 10 keV and 30 MeV, and sensitivity to all directions in the sky. Extensive measurements using radioactive sources have been performed on the isolated detectors. Simulations of these measurements using the GEANT4 Monte Carlo radiation transport simulations toolset have also been preformed. For gamma‐ray burst the spacecraft itself will have a significant impact on the detector response, therefore the final stage of validations involves measuring the detector response to radioactive sources after the spacecraft is fully assembled, and validating the results using simulation. Details of these simulations will be given in this paper.