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Automated Science Processing (ASP) will be performed by the GLAST Large Area Telescope (LAT) Instrument Science Operations Center (ISOC) on data from the satellite as soon as the Level 1 data are available in the ground processing pipeline. ASP will consist of time‐critical science analyses that will facilitate follow‐up and multi‐wavelength observations of transient sources. These analyses include refinement of gamma‐ray burst (GRB) positions, timing, flux and spectral properties, off‐line searches for untriggered GRBs and gamma‐ray afterglows, longer time scale monitoring of a standard set of sources (AGNs, X‐ray binaries), and searches for previously unknown flaring sources in the LAT band. We describe the design of ASP and its scientific products; and we show results of a prototype implementation, driven by the standard LAT data processing pipeline, as applied to simulated LAT and GBM data.

The GLAST Large Area Telescope (LAT) is expected to detect gamma‐ray emission from over a thousand active galaxies, many of which will be flat spectrum radio quasars (FSRQs). A commonly assumed ingredient of leptonic models of FRSQs is the contribution to the gamma‐ray flux from external inverse‐Compton (EIC) scattering of photons from the broad line region (BLR) material by relativistic electrons and positrons in the jet. Here we explore the effect of the BLR geometry on the high‐energy emission from FSRQs.

We have developed an image restoration technique based on the Richardson-Lucy algorithm optimized for GLAST-LAT image analysis. Our algorithm is original since it utilizes the PSF (point spread function) that is calculated for each event. This is critical for EGRET and GLAST-LAT image analysis since the PSF depends on the energy and angle of incident gamma-rays and varies by more than one order of magnitude. EGRET and GLAST-LAT image analysis also faces Poisson noise due to low photon statistics. Our technique incorporates wavelet filtering to minimize noise effects. We present studies of EGRET sources using this novel image restoration technique for possible identification of extended gamma-ray sources., Comment: 5 pages, 3 figures. Presented at First GLAST Symposium, Stanford University, Stanford, CA, USA, February 5-8, 2007

The LAT Instrument Science Operations Center (ISOC) will perform various tasks to support coordination of multiwavelength observations for transient sources. In this paper, we describe the prototype implementation of the Automated Science Processing (ASP) for the detection and analysis of gamma‐ray bursts (GRBs) in LAT and GBM data. The GRB‐related tasks include: position refinement using LAT data given initial GBM or GCN locations, spectral analysis using LAT data alone, joint spectral fitting with GBM data, gamma‐ray afterglow detection and characterization, and blind searches for prompt burst emission in LAT data.

Galaxy clusters appear to have a hard X-ray component based on recent SAX observations. The emission is best fit by a powerlaw and is likely non-thermal in origin. For the Coma cluster, the non-thermal emission is 10% of the thermal component in the 2-10 keV range and dominates above 25 keV. Thus it should be the dominant component in the soft gamma-ray regime. The spectral index is not well constrained by the current X-ray data but appears to be flatter than predicted by the standard Synchrotron-inverse Compton model for both Coma and A2256. INTEGRAL will be able to measure the spectral index of Coma, for example, to 20% and provide an important constraint on emission models. INTEGRAL observations should also reduce possible systematic errors associated with these early detections. The SAX observations challenge the standard model for non-thermal emission since some NT clusters have radio halos (Coma, A2256), others do not (A2199). Alternative emission processes have been suggested to explain the lack of...

We discuss the results of three-dimensional magnetohydrodynamic simulations, using a pseudo-Newtonian potential, of thin disk (h/r ~ 0.1) accretion onto black holes. We find (i) that magnetic stresses persist within the marginally stable orbit, and (ii) that the importance of those stresses for the dynamics of the flow depends upon the strength of magnetic fields in the disk outside the last stable orbit. Strong disk magnetic fields (alpha > 0.1) lead to a gross violation of the zero-torque boundary condition at the last stable orbit, while weaker fields (alpha ~ 0.01) produce results more akin to traditional models for thin disk accretion onto black holes. Fluctuations in the magnetic field strength in the disk could lead to changes in the radiative efficiency of the flow on short timescales., 6 pages, to appear in proceedings, 20th Texas Symposium on Relativistic Astrophysics, eds J.C. Wheeler and H. Martel

Using a geometry consisting of a spherical Comptonizing region surrounded and penetrated by a thin accretion disk, we model the optical through γ-ray spectral energy distribution of the type 1 Seyfert galaxy NGC 5548. We take into account thermal reprocessing by the disk and how the resulting disk emission affects the energy balance of the Comptonizing region. These calculations allow us to infer the properties of the inner disk region including the size, temperature, and optical depth of the Comptonizing plasma. We discuss how INTEGRAL observations of AGNs such as NGC 5548 will provide stringent tests of this and other thermal Comptonization models.

The EGRET instrument aboard the Compton Gamma‐Ray Observatory has detected gamma‐ray emission from many Active Galactic Nuclei during the Phase I & II observation periods. With the continuing discovery of gamma‐ray loud AGN, it becomes increasingly important to characterize the luminosity and density distribution of these objects in order to understand how the gamma‐ray characteristics are related to properties observed at radio, optical and X‐ray wavelengths. The 〈V/Vmax〉 test is applied to the population of gamma‐ray loud Active Galactic Nuclei which have been observed by the EGRET instrument during the Phase I all‐sky survey. Evidence for luminosity evolution is presented, and estimates of the degree of evolution are made given standard assumptions about the cosmology and the form of the luminosity evolution. The effects of observational biases due to gamma‐ray flux‐detection limits and optical identifications are considered.

The EGRET phase 1 & 2 observations of Geminga have been used to determine an optimum contemporary ephemeris using the ‘‘Z2n timing method.’’ The residuals for this linear ephemeris over 2.1 years are less than 5 ms, suggesting that Geminga has not glitched. A position estimate is found to be consistent with the G‘ optical counterpart. The comparison of f between this ephemeris and that of COS‐B yields an estimate of f which is an order of magnitude smaller than that determined from the COS‐B data. It is estimated that the anticipated EGRET phase 3 Geminga exposure will allow for the comparison of Geminga phase between EGRET, COS‐B, and SAS‐2.

The EGRET gamma‐ray telescope has detected a persistent source of high energy gamma rays which has not been identified. It was detected in seven different observations in 1991–1993. Variations in the spectrum, combined with a galactic latitude of +25°, make it likely that this is a previously unknown blazar.

During Phase 1 and Phase 2 of the Compton Observatory’s viewing program, Mrk 421 was in EGRET’s field of view a total of 6 times. This BL Lac object was positively detected by EGRET at 5 σ level and with a photon flux of (1.4±0.3)×10−7 cm−2 s−1 for E≳100 MeV when it was first covered by EGRET in 1991 June 28–July 12. The photon spectrum of this first observation can be represented by a single power law with a photon spectral index of −1.96±0.14. During the 5 subsequent observations, this source was covered by EGRET either at large viewing angles with respect to the instrument axis or with short exposure times. But the source was always visible to the EGRET telescope at about the same flux level as during the first observation except one viewing period, VP222, 1993 May 24–31, for which only an upper limit can be obtained for the photon flux. This upper limit is also consistent with the detected flux levels of the other observations. The average photon floux for E≳100 MeV as calculated from the combined data of all these 6 observations is (1.7±0.3)×10−7 cm−2 s−1 and the corresponding photon spectral index for the combined data is −1.71±0.15. A summary of these results are given in this paper.

The Compton Observatory was pointed at Cygnus twice during the full sky survey (5/30–6/8/91 & 8/8–8/15/91). The COS‐B sources 2CG 075+00 and 2CG 078+01 are detected by EGRET, and smaller error boxes have been obtained, but the sources are not yet identified at other wavelengths. An excess of counts is noted at the position of Cygnus X‐3 consistent with a point source. The corresponding flux is 8±2×10−7 cm−2 s−1 (E≳0.1 GeV)—a factor of 5 less than the flux reported by the SAS‐2 group for Cygnus X‐3. The observed intensities for the individual periods were consistent with no change in intensity between the first and second observations (the second observation began two weeks after the beginning of the July 1991 radio flare). More work is required to refine and verify the galactic diffuse model (which comprises at least 10 times more flux than Cygnus X‐3 in this direction) before a definitive Cygnus X‐ray point‐source result will be obtained. The 4.8 hr X‐ray periodicity of Cygnus X‐3 is not detected in exta...

Ever since the detection of the Crab and Vela pulsars as high‐energy gamma‐ray sources, there has been speculation that many pulsars might be gamma‐ray emitters, some of which might be detectable with more sensitive instruments. Based on theoretical considerations, most interest has focused on young pulsars where a relatively high fraction of the spin down energy might be expected to be carried away in gamma rays. Millisecond pulsars have also been suggested as possible detectable gamma‐ray sources. Consequently, the Compton Gamma Ray Observatory was designed with the ability to time tag gamma rays to an accuracy of a tenth of a millisecond in absolute time. This is needed in view of the long integration times required because of the low expected fluxes. In addition, a cooperative effort has been organized with radio astronomers who are making contemporary measurements of the ephemerides of a relatively large fraction of known pulsars which might be expected to be candidate gamma‐ray ‘‘pulsars’’ based on ...